The syntheses, structures and reactivity of bis(tert-butylcyclopentadienyl)molybdenum derivatives: nitrogen alkylation of an η2-acetonitrile ligand and influence of the chalcogen on the barrier to inversion of chalcogenoether adducts

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The syntheses, structures and reactivity of bis(tert-butylcyclopenta-

dienyl)molybdenum derivatives: nitrogen alkylation of an ꢀ²-aceto-

nitrile ligand and inﬂuence of the chalcogen on the barrier to

inversion of chalcogenoether adducts

Jun Ho Shin, William Savage, Vincent J. Murphy, Jeﬀrey B. Bonanno, David G. Churchill and

Gerard Parkin*

Department of Chemistry, Columbia University, New York, New York 10027, USA

Received 9th January 2001, Accepted 26th March 2001

First published as an Advance Article on the web 17th May 2001

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An investigation of the chemistry of the tert-butyl-substituted molybdenocene system, {(Cp^Bu)₂Mo}

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(Cp^Bu= C₅H₄Bu^t), has demonstrated that the η²-acetonitrile ligand in (Cp^Bu)₂Mo(η²-MeCN) may be alkylated

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by RI (R = Me, Et) at nitrogen to give iminoacyl derivatives, [(Cp^Bu) Mo(η²-MeC᎐NR)]^ϩ, which is a new type of

᎐

2

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reactivity for mononuclear acetonitrile complexes. A series of chalcogenolate–hydride complexes (Cp^Bu)₂Mo(EPh)H

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(E = S, Se, Te) have been obtained by reaction of (Cp^Bu)₂MoH₂with Ph₂E₂, and may be alkylated by MeI to give the

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chalcogenoether adducts [(Cp^Bu)₂Mo(PhEMe)H]I. Dynamic NMR studies on [(Cp^Bu)₂Mo(PhEMe)H]^ϩindicate that

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the barrier to inversion at the chalcogen increases in the sequence S < Se < Te. The oxo complex (Cp^Bu)₂MoO reacts

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with 2 equivalents of Me₃SiX (X = Cl, Br, I, O₂CMe, O₃SMe) to yield (Cp^Bu)₂MoX₂; for X = CN and NCS, (Cp^Bu)₂-

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Mo(OSiMe₃)X, the product of reaction with 1 equivalent may be isolated. (Cp^Bu)₂Mo(OSiMe₃)X (X = CN, NCS)

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reacts with Me₃SiNCS to give the thiocyanate complex (Cp^Bu)₂Mo(SCN)X, rather than the isocyanate isomer,

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(Cp^Bu)₂Mo(NCS)X, thereby indicating that the reactions do not involve a simple metathesis of the Si–NCS bond.

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Other complexes that are reported include: (Cp^Bu)₂MoX₂(X = H, Cl, Br, I, Me, CH₂Ph, CH₂SiMe₃), (Cp^Bu)₂MoL

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(L = CO, C₂H₄, C₂H₂, MeCN, PMe₃), [(Cp^Bu)₂Mo(µ-E)]₂, (Cp^Bu)₂Mo(η²–E₂) and (Cp^Bu)₂Mo(EPh)₂(E = S, Se, Te).

Introduction

Although the ﬁrst molybdenocene and tungstenocene com-

plexes, [Cp₂MoCl][Cr(CNS)₄(NH₃)₂]ؒH₂O and [Cp₂MCl₂]₂-

[PtCl₆] (M = Mo and W), were prepared by Cotton and

Wilkinson in 1954,¹the development of molybdenocene

and tungstenocene chemistry awaited the synthesis of the

dihydrides, Cp₂MH₂, in 1959.²By comparison to the extensive

chemistry of the parent molybdenocene system,^3,4the chemistry

of ring-substituted molybdenocene complexes is poorly

developed, an observation that has been attributed to synthetic

diﬃculties.⁵Unsubstituted molybdenocene complexes typically

exhibit poor solubility which hampers certain studies. For

example, Marks has noted how the low solubility of the parent

system complicates thermochemical studies, necessitating the

use of methylated molybdenocene complexes.⁶In this paper,

we report the chemistry of molybdenocene complexes that

feature a bulky tert-butyl substituent on the cyclopentadienyl

ring and thus exhibit improved solubility in organic solvents

1

and also provides a useful probe for H NMR spectroscopic

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Fig. 1 Molecular structure of (Cp^Bu)₂MoH₂(the hydride ligands were

studies. Speciﬁc issues that are discussed include: (i) nitrogen

alkylation of an η²-acetonitrile ligand and (ii) the inﬂuence of

the chalcogen on the barrier to inversion of chalcogenoether

adducts.

not located, and their positions are illustrative and are based on those

in Cp₂MoH₂).

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structure of (Cp^Bu)₂MoH₂has been determined by X-ray dif-

fraction (Fig. 1) and the Cp_cent–Mo–Cp_centangle of 150.6Њ is

Results and discussion

slightly greater than that in the parent complex, Cp₂MoH₂

Dihydride, dihalide and dialkyl complexes

(145.8Њ).¹²Although the hydride ligands were not located, the

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(Cp^Bu)₂MoH₂, the key starting material for development of

[MoH₂] moiety of (Cp^Bu)₂MoH₂is characterized by a signal

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1

the chemistry of the [(Cp^Bu)₂Mo] system, is readily obtained

at δ Ϫ8.78 ppm in the H NMR spectrum and by ν(Mo–H)

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by reaction of MoCl₅with a mixture of NaBH₄and (Cp^Bu)Li

(Scheme 1), a procedure that is analogous to the synthesis of

absorptions at 1823 and 1866 cm^Ϫ1in the solution IR spectrum.

For comparison, spectroscopic data for other molybdenocene

other molybdenocene dihydrides,⁷e.g. Cp₂MoH₂,⁸(Cp^Me)₂-

dihydrides are summarized in Table 1.

n

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MoH₂,^5b,6,9(Cp^Bu)₂MoH₂,⁹and Cp*₂MoH₂.^10,11The molecular

The dihydride complex (Cp^Bu)₂MoH₂is readily converted to

1732

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

DOI: 10.1039/b100372k

This journal is © The Royal Society of Chemistry 2001

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Table 1 ¹H NMR and IR spectral data of [Mo–H] moieties of molybdenum dihydride complexes

Complex

¹H NMR/ppm

ν(Mo–H)/cm^Ϫ1

Reference

Cp₂MoH₂

Ϫ8.80

Ϫ8.25

Ϫ8.78

1826 (1847)

1835 (1840)

1823, 1866^a

1852, 1906^b

1830

1862

1750, 1760

7

(Cp^Me)₂MoH₂

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(Cp^Bu)₂MoH₂

This work

n

(Cp^Bu)₂MoH₂

Ϫ8.70

Ϫ8.38

Ϫ4.77

Ϫ4.74

Ϫ6.18

Ϫ8.70

9

83

84, 85

84

86

Cp*₂MoH₂

Me₂C(C₅H₄)₂MoH₂

[(C₄H₈)(C₅H₄)₂]MoH₂

Me₂Si(C₅Me₄)₂MoH₂

O{Me₂Si(C₅H₄)}₂MoH₂

1830

1818

5

^aPentane solution. ^bKBr disk.

Scheme 1

halide derivatives which, in turn, are useful precursors to

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other molybdenocene complexes. For example, (Cp^Bu)₂MoH₂

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is converted to the dichloride, (Cp^Bu)₂MoCl₂by reaction of

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(Cp^Bu)₂MoH₂with CCl₄(Scheme 1).^13,14The bromide ana-

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logue, (Cp^Bu)₂MoBr₂may likewise be obtained by treatment

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of (Cp^Bu)₂MoH₂with CH₂Br₂. In contrast, the reaction of

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(Cp^Bu)₂MoH₂with CH₃I yields the hydride–iodide complex,

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(Cp^Bu)₂Mo(H)I, rather than the diiodide. The diiodide may,

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nevertheless, be obtained by treatment of (Cp^Bu)₂MoO with

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Me₃SiI (vide infra). The molecular structures of (Cp^Bu)₂MoCl₂

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and (Cp^Bu)₂MoBr₂have been determined by X-ray diﬀraction

as shown in Fig. 2.

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The dialkyl complexes (Cp^Bu)₂MoR₂are readily obtained by

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reactions of (Cp^Bu)₂MoCl₂with a variety of alkylating agents,

e.g. CH₃Li, CH₃MgI, Me₃SiCH₂MgCl and PhCH₂MgCl

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(Scheme 2). The molecular structures of (Cp^Bu)₂Mo(CH₂Ph)₂

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and (Cp^Bu)₂Mo(CH₂SiMe₃)₂have been determined by X-ray

diﬀraction as shown in Figs. 3 and 4. Comparison of the data

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for the halide and alkyl derivatives, (Cp^Bu)₂MoX₂, and also

those described below (Table 2), indicates that the X–Mo–X

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angles in (Cp^Bu)₂MoX₂(ca. 73–81Њ) are relatively insensitive

to the nature of X and are similar to that of Cp₂MoCl₂(82Њ);

in contrast, it is well established that the dⁿcount has a pro-

nounced eﬀect on X–M–X angle, as illustrated by the value of

100.8Њ for the Mo^VIcomplex, [Cp₂MoCl₂]^2ϩ(Table 2).

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Fig. 2 Molecular structure of (Cp^Bu)₂MoBr₂(the chloride analogue

is similar). Selected bond lengths (Å) and angles (Њ): Mo–Cl 2.493(2),

Cl–Mo–Cl 80.6(1); Mo–Br 2.650(2), Br–Mo–Br 80.7(1).

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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Table 2 Structurally characterized (Cp^Bu)₂Mo(X)(Y) complexes

Complex

d(Mo–X)/Å

X–Mo–Y/Њ

Reference

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(Cp^Bu)₂MoCl₂

2.493(2)

2.650(1)

2.347(3)

2.304(3)

80.6(1)

80.7(1)

77.0(1)

78.4(2)

76.24(9)

73.3(1)

77.4(2)

82.0(2)

87.9(1)

87.07(10)

100.8

This work

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(Cp^Bu)₂MoBr₂

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(Cp^Bu)₂Mo(CH₂Ph)₂

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(Cp^Bu)₂Mo(CH₂SiMe₃)₂

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(Cp^Bu)₂Mo[OS(O)₂Me]₂

2.148(2), 2.117(2)

2.504(1)

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(Cp^Bu)₂(SPh)₂

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[(Cp^Bu)₂Mo(PMe₃)Me]^ϩ

Cp₂MoCl₂

2.491(2),^a2.287(7)^b

2.464(6), 2.470(5)

2.382(4)

[Cp₂MoCl₂][BF₄]

87

88

89

2.400(3)

2.286(4)

[Cp₂MoCl₂][AsF₆]₂

^aMo–P. ^bMo–C(1).

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Fig. 4 Molecular structure of (Cp^Bu)₂Mo(CH₂SiMe₃)₂. Selected bond

lengths (Å) and angles (Њ): Mo–C(21) 2.304(3), Si–C(21) 1.863(3);

C(21)–Mo–C(21Ј) 78.4(2), Mo–C(21)–Si 134.3(2).

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Molybdenocene adducts (Cp^Bu)₂MoL (L

؍

CO, C₂H₄, C₂H₂,

Scheme 2

MeCN, PMe₃)

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Reduction of (Cp^Bu)₂MoCl₂using Na(Hg) in the presence of

a donor ligand, e.g. L = CO, C₂H₄, C₂H₂, MeCN, PMe₃, yields

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the corresponding adducts (Cp^Bu)₂MoL (Scheme 2),¹⁵with the

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molecular structure of (Cp^Bu)₂MoPMe₃shown in Fig. 5. The

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acetonitrile adduct (Cp^Bu)₂Mo(η²-MeCN) is characterized by

a ν(CN) IR absorption at 1777 cm^Ϫ1, which is indicative of

the rather rare η²-coordination mode, analogous to that for

Cp₂Mo(η²-MeCN).^16–18Speciﬁcally, whereas η¹-coordination is

characterized by a small increase in ν(CN) stretching frequency,

the uncommon η²-coordination mode is associated with a large

decrease in ν(CN) stretching frequency of up to ca. 500 cm^Ϫ1

lower than that of free acetonitrile (2250 cm^Ϫ1),¹⁹due to exten-

sive back-bonding.²⁰η²-Acetonitrile ligands may be classiﬁed

as either two-electron or four-electron donors (analogous to

alkynes), which may be distinguished on the basis of the ¹³C

NMR chemical shift for the nitrile carbon atom.²¹Thus,

two-electron donor MeCN ligands are characterized by ¹³C

NMR chemical shifts in the range ca. δ 165–180 ppm, whereas

four-electron donors are characterized by shifts in the range

ca. δ 230–240 ppm.^22,23Hence, with a chemical shift of 168.1

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ppm, the acetonitrile ligand in (Cp^Bu)₂Mo(η²-MeCN) is better

described as two-electron donor, in accord with the 16-electron

conﬁguration of the molybdenocene fragment.

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Fig. 3 Molecular structure of (Cp^Bu)₂Mo(CH₂Ph)₂. Selected bond

lengths (Å) and angles (Њ): Mo–C(1) 2.347(3), Mo–C(2) 2.309(3), C(1)–

C(31) 1.483(4), C(2)–C(41) 1.488(4); C(1)–Mo–C(2) 77.0(1), Mo–C(1)–

C(31) 122.8(2), Mo–C(2)–C(41) 121.0(2).

Facile displacement of the carbonyl ligand allows the mono-

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carbonyl (Cp^Bu)₂Mo(CO) to be a useful precursor for other

1734

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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Fig. 5 Molecular structure of (Cp^Bu)₂Mo(PMe₃). Selected bond

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Fig.

6

Molecular structure of [(Cp^Bu)₂Mo(PMe₃)Me]^ϩ. Selected

length (Å): Mo–P 2.459(1) Å.

bond lengths (Å) and angles (Њ): Mo–P 2.491(2), Mo–C(1) 2.287(7);

P–Mo–C(1) 77.4(2).

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molybdenocene derivatives, e.g. (Cp^Bu)₂Mo(η²-E₂) and (Cp^Bu)₂-

Mo(EPh)₂(E = S, Se, Te) by reaction with the elemental

chalcogen and Ph₂E₂, as described in detail below.²⁴It is

also noteworthy that these reactions are considerably more

facile than the corresponding reactions of the dihydride

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(Cp^Bu)₂MoH₂.

In addition to displacement reactions, the carbonyl and tri-

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methylphosphine adducts (Cp^Bu)₂MoL (L = CO, PMe₃) are

readily alkylated by MeI to give the corresponding methyl

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complex, [(Cp^Bu)₂Mo(L)Me]^ϩ(Scheme 3). The molecular

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Fig. 7 Molecular structure of [(Cp^Bu)₂Mo(η²-MeC᎐NEt)]^ϩ. Selected

᎐

bond lengths (Å) and angles (Њ): Mo–C(2) 2.105(9), Mo–N 2.113(8),

C(1)–C(2) 1.523(14), C(2)–N 1.177(12), C(3)–C(4) 1.11(3), C(3)–N

1.52(2); C(2)–Mo–N 32.4(3), N–C(2)–C(1) 133.9(11), N–C(2)–Mo

74.2(6), C(1)–C(2)–Mo 151.9(9), C(4)–C(3)–N 127(2), C(2)–N–C(3)

137.0(12), C(2)–N–Mo 73.4(6), C(3)–N–Mo 149.6(10).

In contrast to the formation of a simple methyl complex,

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the reaction of MeI with the acetonitrile adduct (Cp^Bu)₂-

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Mo(η²-MeCN) yields the iminoacyl complex [(Cp^Bu)₂-

Mo(η²-MeC᎐NMe)]I (Scheme 3). Likewise, EtI reacts with

᎐

t

(Cp^Bu)₂Mo(η²-MeCN) to yield [(Cp^Bu) Mo(η²-MeC᎐NEt)]I.

᎐

2

t

The iminoacyl moiety (MeC᎐NMe) in [(Cp^Bu)₂Mo(η²-

᎐

MeC᎐NMe)]I is characterized by ¹H NMR signals at δ 3.00 (q,

᎐

⁵J_H–H= 1 Hz, CCH₃) and 3.56 (q, J_H–H= 1 Hz, NCH₃) ppm

5

attributable to the methyl groups attached to carbon and

nitrogen, respectively; these signals have been assigned by

Scheme 3

comparison with the ¹H NMR spectrum of the deuterated

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structure of [(Cp^Bu)₂Mo(PMe₃)Me]I²⁵has been determined

derivative [(Cp^Bu) Mo(η²-MeC᎐NCD )]I. Interestingly, the

᎐

2

3

t

by X-ray diﬀraction (Fig. 6), while the carbonyl complex

ν(CN) stretching frequency for the iminoacyl [(Cp^Bu)₂-

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[(Cp^Bu)₂Mo(CO)Me]I is characterized by a ν(CO) stretch of

Mo(η²-MeC᎐NMe)]^ϩ(1747 cm^Ϫ1) is comparable to that

᎐

t

2011 cm^Ϫ1. This value is ca. 100 cm^Ϫ1higher than that of the

of the acetonitrile adduct (Cp^Bu)₂Mo(η²-MeCN) (1777 cm^Ϫ1).

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neutral d⁴precursor, (Cp^Bu)₂Mo(CO) (1907 cm^Ϫ1), in accord

with the reduction of metal-to-ligand π-backbonding expected

for the cationic species.²⁶

The molecular structure of [(Cp^Bu) Mo(η²-MeC᎐NEt)]I has

᎐

2

been determined by X-ray diﬀraction as shown in Fig. 7. Of

particular note, the C(2)–N bond length [1.177(12) Å] in

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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[(Cp^Bu) Mo(η²-MeC᎐NEt)]^ϩis short compared to those of

᎐

2

other iminoacyl derivatives [1.19 – 1.35 Å; mean 1.27 Å].²⁷

Furthermore, the C–N bond length is short compared to com-

pounds with uncoordinated C᎐N double bonds (1.29–1.31 Å),²⁸

᎐

but is comparable to the MeC᎐N triple bond length of free

᎐

acetonitrile [1.158(2) Å].²⁹For additional comparison, the C–N

bond length in the acetonitrile complex, Cp₂Mo(η²-MeCN) is

1.20(1) Å.^16a

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The formation of the iminoacyl complexes [(Cp^Bu)₂Mo(η²-

t

MeC᎐NR)]^ϩby the room temperature alkylation of (Cp^Bu)₂-

᎐

Mo(η²-MeCN) with RI is noteworthy because it represents an

unprecedented reaction of acetonitrile coordinated to a single

metal center; furthermore, such alkylation is of interest since

acetonitrile is not particularly basic.³⁰Thus, acetonitrile com-

plexes typically react by either (i) displacement, (ii) electro-

philic or nucleophilic attack at carbon, or (iii) direct reaction

at the metal center. For example, the acetonitrile ligand in

Cp₂Mo(η²-MeCN) is readily displaced by Bu^tNC to give

Cp₂MoCNBu^t,³¹and by (PhCOO)₂, Et₂S₂, and Ph₂Se₂to give

Cp₂Mo(ER)₂(E = O, S or Se).^15aAnother example of displace-

ment of an acetonitrile ligand is provided by the reaction of

[Cp₂Ti(η¹-NCMe)Me]^ϩwith Me₃SiCN to give [Cp₂Ti(η²-

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Fig. 8 Molecular structure of (Cp^Bu)₂MoO. Selected bond length (Å):

Mo–O 1.705(4).

MeC᎐NSiMe )(CNSiMe )]^ϩ; the reaction is proposed to

᎐

3

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occur via insertion of equilibrium amounts of the isomeric

isocyanide, Me₃SiNC, into the Ti–Me bond.³²Illustrative of

electrophilic attack at carbon, (dppe)₂Re(NCR)Cl is protonated

to give [(dppe)₂Re{NC(H)R}Cl]^ϩ.³³Cp₂Mo(η²-MeCN) is

complex (Cp^Bu)₂MoO, may be synthesized by the reaction of

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(Cp^Bu)₂MoCl₂with excess LiOH (Scheme 2). The molecular

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structure of (Cp^Bu)₂MoO has been determined by X-ray dif-

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fraction (Fig. 8); the Mo᎐O bond length in (Cp^Bu)₂MoO

᎐

also protonated by HBF to yield Cp Mo(η¹-NH᎐CHMe)(η¹-

[1.706(4) Å] is similar to that in the (Cp^Me)₂MoO counterpart

᎐

4

2

t

NCMe); however, rather than direct attack at the acetonitrile

ligand, the reaction has been postulated to occur via initial

protonation at the metal center, followed by insertion of the

acetonitrile ligand.^20a,34Another example of electrophilic attack

[1.721(2) Å].³⁹The [Mo᎐O] moiety in (Cp^Bu)₂MoO is also

᎐

characterized by an IR absorption at 838 cm^Ϫ1, a value that is

comparable to those in, Cp₂MoO (800 cm^Ϫ1) and (Cp^Me)₂MoO

(827 cm^Ϫ1).⁴⁰Although the ν(Mo᎐O) frequencies are low and

᎐

at carbon is provided by the formation of the acetylimido

the Mo᎐O bond lengths are long in comparison to those for

᎐

Me₂

complex [Tp^Me]W{NC(O)Me}(CO)I by reaction of [Tp ]-

2

other molybdenum oxo complexes,⁴¹it is recognized that this

is a common feature of metallocene oxo complexes due to the

orbital description of the metallocene fragment disfavoring the

W{NCMe}(CO)I with oxo transfer reagents such as DMSO,

propylene oxide and pyridine N-oxide.^21bExamples of nucleo-

philic attack at carbon involve reactions with [Et₃BH]^Ϫ, H₂O,

+

42,43

¯

᎐

triply bonded [M᎐O] resonance structure.

᎐

ROH and RNH₂.²⁰

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As with (Cp^Bu)₂MoCl₂, (Cp^Bu)₂MoO is also a useful reagent

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Alkylation of the nitrogen atom of (Cp^Bu)₂Mo(η²-MeCN)

also represents an alternative synthesis of iminoacyl derivatives,

which have otherwise been obtained by insertion of an iso-

cyanide RNC into a M–Me bond.²⁷For example, [Cp₂Mo(η²-

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for the synthesis of other (Cp^Bu)₂MoX₂derivatives. For

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example, (Cp^Bu)₂MoO reacts with Me₃SiX (X = Cl, Br, I,

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O₂CMe, O₃SMe)⁴⁴to yield (Cp^Bu)₂MoX₂(Scheme 4), with the

MeC᎐NR)]^ϩ(R = Me, Et) has been obtained by thermal

᎐

isomerization of the isocyanide adduct [Cp₂Mo(CNR)Me]^ϩ.³⁵

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Two possibilities exist for the formation of [(Cp^Bu)₂Mo(η²-

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MeC᎐NR)]^ϩfrom (Cp^Bu)₂Mo(η²-MeCN): (i) direct nucleo-

᎐

philic attack of the nitrogen atom with RI, and (ii) initial

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methylation of the metal center to give [(Cp^Bu)₂Mo(NCMe)-

Me]^ϩ, accompanied by subsequent rearrangement. Of these

two possibilities, the former is considered to be the more likely

in view of the observation that other [(Cp^R)₂M(NCMe)R]^ϩ

complexes show no tendency to convert to the corresponding

iminoacyl derivatives.^36,37Furthermore, the reactions of [Cp₂Ti-

(NCMe)Me]^ϩwith CO and CNBu^tgive [Cp₂Ti(NCMe)(η²-CO-

Me)]^ϩand [Cp₂Ti(η²-Bu^tN=CMe)(CNBu^t)]^ϩ, respectively,

with no evidence for coupling of the methyl and acetonitrile

ligands.³⁸The enhanced nucleophilic character of the nitrogen

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atom in (Cp^Bu)₂Mo(η²-MeCN), compared to that of other

η¹-MeCN adducts is undoubtedly a manifestation of the

uncommon η²-coordination mode. Thus, whereas the nitrogen

atom of an η¹-coordinated acetonitrile is unlikely to act in a

nucleophilic manner because the nitrogen lone pair is directly

involved in bonding with the metal, the lone pair of the nitro-

gen atom of an η²-coordinated acetonitrile ligand is not

involved in bonding to the metal and is thus susceptible to

electrophilic attack.

Scheme 4

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structure of (Cp^Bu)₂Mo[OS(O)₂Me]₂illustrated in Fig. 9. The

ﬁrst step of these transformations is proposed to involve the

formal 1,2-addition⁴⁵of the Si–X bond across the Mo᎐O

᎐

t

double bond, generating (Cp^Bu)₂Mo(OSiMe₃)X; subsequent

Chalcogenido complexes

metathesis of the Mo–OSiMe₃and Me₃Si–X bonds yields

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(a) The oxo complex (Cp^Bu)₂MoO. The molybdenum oxo

(Cp^Bu)₂MoX₂and (Me₃Si)₂O. Although the intermediates

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J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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(SCN) (vide infra) is characterized by a single ν(CN) absorption

at 2072 cm^Ϫ1, it is characterized by two very distinct ¹³C NMR

spectroscopic signals at δ 153.0 and 124.6 ppm which are

assignable to the carbons of the [Mo–NCS] and the [Mo–SCN]

moieties, respectively, on the basis of the criteria described

above.

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The ability to isolate the trimethylsiloxy species (Cp^Bu)₂-

Mo(OSiMe₃)X for derivatives in which X = CN or NCS, but

not for those in which X = Cl, Br, I, O₂CMe, or O₃SMe is a

particularly noteworthy observation since it indicates that the

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reactivity of the Mo–OSiMe₃linkage of (Cp^Bu)₂Mo(OSiMe₃)X

towards Me₃SiX is strongly dependent on the nature of X.

In this regard, Marks and co-workers have also reported that

the related chloride species (Cp^Me)₂Mo(OSiMe₃)Cl can not

be isolated from the reaction of (Cp^Me)₂MoO with Me₃SiCl.⁶

The tungsten analogue (Cp^Me)₂W(OSiMe₃)Cl could be

isolated,⁶however, and Cp₂W(OSiMe₃)Cl⁵¹and Cp*₂W(OSi-

Me₃)Cl⁵²have also been spectroscopically identiﬁed.

t

Interestingly, the stability of the cyanide complex (Cp^Bu)₂-

Mo(OSiMe₃)(CN) is suﬃciently great that it shows no further

Bu^t

reaction towards Me₃SiCN, even at 80 ЊC. The isothiocyanate

Fig. 9 Molecular structure of (Cp )₂Mo[OS(O)₂Me]₂. Selected bond

t

complex (Cp^Bu)₂Mo(OSiMe₃)(NCS) does, nevertheless, react

lengths (Å) and angles (Њ): Mo–O(11) 2.148(2), Mo–O(21), 2.117(2),

S(1)–O(11) 1.500(2), S(2)–O(21), 1.498(2); O(11)–Mo–O(21) 76.24(9),

Mo–O(11)–S(1) 137.23(14), Mo–O(21)–S(2) 135.7(2).

t

further with Me₃SiNCS to give sequentially (Cp^Bu)₂Mo(NCS)-

t

(SCN) and (Cp^Bu)₂Mo(NCS)₂(Scheme 5). The two isomers

may be cleanly isolated on the basis of their solubility dif-

t

(Cp^Bu)₂Mo(OSiMe₃)X were not generally isolated, examples of

ferences; thus, (Cp^Bu)₂Mo(NCS)₂is completely insoluble in

t

such species, namely (Cp^Bu)₂Mo(OSiMe₃)(CN) and (Cp^Bu)₂-

benzene and toluene, while (Cp^Bu)₂Mo(NCS)(SCN) is soluble

Mo(OSiMe₃)(NCS), have been obtained from the reactions of

in both solvents. The observation that the asymmetric isomer

t

(Cp^Bu)₂MoO with one equivalent of Me₃SiCN and Me₃SiNCS

(Scheme 4). The thiocyanate ligand is ambidentate and may

coordinate to a metal center via either sulfur (M–SCN, thio-

cyanate) or nitrogen (M–NCS, isothiocyanate). ¹³C NMR

spectroscopy has been used to distinguish the two coordination

modes, with the chemical shift for M–NCS moieties being

comparable to, or greater than, that for NCS^Ϫ(ca. 134 ppm),

whereas M–SCN moieties are characterized by chemical shifts

(Cp^Bu)₂Mo(NCS)(SCN) is formed initially is particularly

important, because it indicates that the reaction does not

involve a simple metathesis of the Mo–OSiMe₃and Me₃Si–

NCS bonds. One possibility is that the terminal sulfur atom

interacts with the molybdenum center and facilitates the overall

reaction, as illustrated in Scheme 6.

t

Although (Cp^Bu)₂Mo(OSiMe₃)(CN) is unreactive towards

Me₃SiCN at 80 ЊC, it does react with other Me₃SiX derivatives

t

less than that for NCS^Ϫ(i.e. δ_M–SCN< δ_NCSϪр δ_M–NCS).⁴⁶Thus,

at room temperature to yield (Cp^Bu)₂Mo(X)(CN) (X = Cl, Br, I,

t

with a chemical shift of 150.2 ppm, (Cp^Bu)₂Mo(OSiMe₃)(NCS)

is clearly identiﬁed as a N-bound isothiocyanate derivative.

In contrast to the use of ¹³C NMR spectroscopy, the ν(CN)

stretching frequency is not capable of deﬁnitively identifying

the thiocyanate coordination mode.⁴⁷For example, [M–NCS]

moieties are characterized by ν(CN) stretching frequencies in

O₃SCH₃). (Cp^Bu)₂Mo(OSiMe₃)(CN) also reacts with Me₃Si-

t

NCS to yield (Cp^Bu)₂Mo(SCN)(CN), rather than (Cp^Bu)₂Mo-

t

(NCS)(CN), which may be obtained by reaction of (Cp^Bu)₂-

t

Mo(NCS)₂with Me₃SiCN (Scheme 5). (Cp^Bu)₂Mo(SCN)(CN)

t

and (Cp^Bu)₂Mo(NCS)(CN) may be readily distinguished on the

basis of the ¹³C NMR resonances for the [NCS] ligand: 124.6

t

the range ca. 2025–2100 cm^{Ϫ1 48}

,

while [M–SCN] moieties are

and 150.2 ppm, respectively. The formation of (Cp^Bu)₂Mo-

t

characterized by ν(CN) stretching frequencies in the range

(SCN)(CN), rather than (Cp^Bu)₂Mo(NCS)(CN), in the reaction

t

2090–2125 cm^{Ϫ1 49,50}

.

Thus, with a ν(CN) stretching frequency

of (Cp^Bu)₂Mo(OSiMe₃)(CN) with Me₃SiNCS is in accord with

t

of 2102 cm^Ϫ1, IR spectroscopy is inconclusive with respect

the above formation of (Cp^Bu)₂Mo(NCS)(SCN) in the reaction

t

to the coordination mode in (Cp^Bu)₂Mo(OSiMe₃)(NCS).

of (Cp^Bu)₂Mo(OSiMe₃)(NCS) with Me₃SiNCS. Thus, it is evi-

t

Furthermore, while the mixed complex (Cp^Bu)₂Mo(NCS)-

dent that the reactivity displayed by (Cp^Bu)₂Mo(OSiMe₃)-

Scheme 5

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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t

genido complexes, (Cp^Bu)₂Mo(η²-E₂) (E = S, Se) as illustrated

in Scheme 7.⁵³

t

The ditellurido complex (Cp^Bu)₂Mo(η²-Te₂) may also be

isolated, but the reaction requires the presence of PMe₃as a

catalyst which generates Me₃PTe as the active transfer

t

agent.^54,55The carbonyl complex (Cp^Bu)₂Mo(CO) also reacts

t

with the elemental chalcogens to give (Cp^Bu)₂Mo(η²-E₂) (E = S,

Scheme 6

Se, Te), as illustrated in Scheme 7,⁵⁶but the reactions are more

t

facile than those of (Cp^Bu)₂MoH₂; for example the reaction

(CN) towards a variety of Me₃SiX derivatives indicates that

Me₃SiCN is unique by showing little tendency to displace

t

between (Cp^Bu)₂Mo(CO) and tellurium does not require

an OSiMe₃group. Furthermore, Me₃SiCN does react with

the presence of catalytic PMe₃, unlike the reaction of

t

(Cp^Bu)₂Mo(OSiMe₃)(NCS), but rather than displace the Me₃-

(Cp^Bu)₂MoH₂.

t

Ligand exchange is observed between (Cp^Bu)₂Mo(η²-Se₂)

SiO ligand, it is the NCS ligand that is displaced giving

t

(Cp^Bu)₂Mo(OSiMe₃)(CN). The preferential displacement of

and (Cp^Bu)₂Mo(η²-Te₂) to give the mixed chalcogenido com-

t

plex (Cp^Bu)₂Mo(η²-SeTe) as a component in an equilibrium

the NCS ligand, rather than the Me₃SiO ligand, in the reaction

t

of (Cp^Bu)₂Mo(OSiMe₃)(NCS) with Me₃SiCN presumably

reﬂects the diﬀerent nucleophilic tendencies of the oxygen and

nitrogen atoms of the two molybdenum-bound ligands. The

greater nucleophilic character of the [Mo–NCS] moiety is likely

associated with increased availability of the nitrogen lone pair

of the bent Mo–NCS ligand, compared to that of oxygen in the

more bulky Me₃SiO ligand. It is also possible that displacement

of the NCS ligand is favored due to the Mo–NCS bond being

weaker than the Mo–OSiMe₃bond, although these values are

1

mixture which has been characterized by H, ⁷⁷Se and ¹²⁵Te

t

1

NMR spectroscopy. The H NMR spectrum of (Cp^Bu)₂Mo-

(η²-SeTe) shows a singlet and four multiplets⁵⁷consistent

with an asymmetric structure, while those of each symmetric

dichalcogenido complex show a singlet and two “triplets”.

Also, the ⁷⁷Se and ¹²⁵Te NMR spectra shows signals at Ϫ430

(¹J_Se–Te= 522 Hz) and Ϫ459 ppm,⁵⁸respectively, and the values

diﬀer by 170–340 ppm from those of the dichalcogenido

complexes.

t

The diselenido and ditellurido complexes (Cp^Bu)₂Mo(η²-Se₂)

unknown.

t

The fact that (Cp^Bu)₂Mo(OSiMe₃)(CN) reacts with other

and (Cp^Bu)₂Mo(η²-Te₂) are characterized by ⁷⁷Se and ¹²⁵Te

NMR signals at δ Ϫ254 and δ Ϫ803 ppm, respectively, while

t

Me₃SiX derivatives indicates that the inertness of (Cp^Bu)₂-

t

the molecular structures of (Cp^Bu)₂Mo(η²-S₂) and (Cp^Bu)₂-

Mo(OSiMe₃)(CN) towards Me₃SiCN is not so much associated

t

with a special stability of (Cp^Bu)₂Mo(OSiMe₃)(CN), but rather

is associated with Me₃SiCN. A possible rationalization for the

inability of Me₃SiCN to displace a Mo–OSiMe₃group is pro-

vided by the above observation that it is the terminal sulfur

atom of the Me₃Si–NCS molecule that initially becomes

Mo(η²-Se₂) have been determined by X-ray diﬀraction

(Fig. 10); selected bond lengths and angles are compared in

t

Table 3. The [Mo(η²-E₂)] moieties of (Cp^Bu)₂Mo(η²-E₂) may be

described by two extreme resonance forms (Fig. 11). The issue

of which resonance form is most appropriate may be decided

t

by comparing the [E–E] bond lengths in (Cp^Bu)₂Mo(η²-E₂)

coordinated to the molybdenum center. Extending this notion

t

to the reaction of (Cp^Bu)₂Mo(OSiMe₃)(CN) towards Me₃SiCN,

with other [E–E] and [E᎐E] bond length data. For example,

᎐

t

the S–S bond length of 2.043(4) Å in (Cp^Bu)₂Mo(η²-S₂) is

the initial product would be predicted to be an unprecedented

t

isocyanide species, (Cp^Bu)₂Mo(NC)X. As such, a mechanism of

this type would not be expected to be facile, in accord with the

observations.

comparable to the S–S single bonds in S₈(2.060 Å)⁵⁹and S₂

2Ϫ

(e.g. 2.08 Å in SrS₂⁶⁰and 2.13 Å in Na₂S₂⁶¹), but is much longer

than that of the S᎐S bond in the gas phase (1.887 Å).^59,62

᎐

t

Likewise, the Se–Se bond length of 2.322(6) Å in (Cp^Bu)₂Mo-

(b) Sulﬁdo, selenido, and tellurido complexes. Whereas the

(η²-Se₂) is much closer to those in the Se₈molecule (2.34 Å)⁵⁹

t

oxo derivative (Cp^Bu)₂MoO is readily obtained from (Cp^Bu)₂-

MoCl₂, heavier chalcogenido complexes are more conveniently

obtained from either the dihydride or carbonyl complexes,

and Na₂Se₂[2.38(5) Å]⁶¹than that of the Se᎐Se bond in the

᎐

gas phase (2.19 Å).⁵⁹On the basis of these bond length com-

parisons, it is evident that the dichalcogenido complexes,

t

(Cp^Bu)₂MoH₂and (Cp^Bu)₂Mo(CO). Thus, (Cp^Bu)₂MoH₂reacts

readily with elemental sulfur or selenium to give the dichalco-

(Cp^Bu)₂Mo(η²-E₂) (E = S, Se), have a Mo() metallacyclo-

propane type structure rather than a Mo() dichalcogen

Scheme 7

1738

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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t

Table 3 Comparison of bond lengths (Å) and angles (Њ) for (Cp^Bu)₂-

resonance form which would have more double bond character

Mo(η²-E₂) (E = S, Se)

between both chalcogen atoms.⁶³

t

Dinuclear monochalcogenido complexes [(Cp^Bu)₂Mo(µ-E)]₂

E = S

E = Se

(E = S, Se, Te) may be obtained by treatment of the dichalco-

t

genido complexes (Cp^Bu)₂Mo(η²-E₂) with PMe₃as illustrated

Mo–E(1)

Mo–E(2)

E(1)–E(2)

2.459(2)

2.449(2)

2.043(4)

2.598(4)

2.586(4)

2.322(6)

in Scheme 7. The observation that the sulﬁdo, selenido, and

t

tellurido ligands in [(Cp^Bu)₂Mo(µ-E)]₂bridge two metal centers,

t

whereas the oxo ligand in (Cp^Bu)₂MoO is terminal, is in line

with previous studies on chalcogenido complexes of the transi-

tion elements, which indicate that the occurrence of terminal

E(1)–Mo–E(2)

Mo–E(1)–E(2)

Mo–E(2)–E(1)

49.2(1)

65.1(1)

65.7(1)

53.2(2)

63.1(2)

63.6(2)

chalcogenido complexes decreases rapidly in the order O ӷ

t

S > S > Te.⁴²The molecular structure of [(Cp^Bu)₂Mo(µ-Se)]₂

has been determined by X-ray diﬀraction (Fig. 12). The Mo–Se

bond length [2.611(2) Å] is comparable to those in

t

(Cp^Bu)₂Mo(η²-Se₂) [2.598(4) and 2.586(4) Å]. The [Mo(µ-

t

E)₂Mo] moieties of [(Cp^Bu)₂Mo(µ-E)]₂(E = Se, Te) derivatives

are characterized by ⁷⁷Se and ¹²⁵Te NMR signals at δ Ϫ996 and

δ Ϫ1664 ppm, respectively.

t

The abstraction of a chalcogen atom from (Cp^Bu)₂Mo(η²-E₂)

t

is reversible, in the sense that [(Cp^Bu)₂Mo(µ-E)]₂(E = Se, Te)

t

regenerate (Cp^Bu)₂Mo(η²-E₂) upon heating with elemental Se

t

or Te.⁶⁴The reaction of [(Cp^Bu)₂Mo(µ-Se)]₂with tellurium gives

t

not only (Cp^Bu)₂Mo{η²-(SeTe)}, but also (Cp^Bu)₂Mo(η²-Se₂)

t

and (Cp^Bu)₂Mo(η²-Te₂) as a result of chalcogen scrambling.

Chalcogenolate complexes

t

The reactions of (Cp^Bu)₂MoH₂with Ph₂E₂(E = S, Se, Te)

provide a convenient method for generating phenylchalco-

t

genolate derivatives.⁶⁵Thus, reaction of (Cp^Bu)₂MoH₂with

t

Ph₂E₂(E = S, Se, Te) gives sequentially (Cp^Bu)₂Mo(EPh)H

t

and (Cp^Bu)₂Mo(EPh)₂, with the exception that the tellurium

t

derivative (Cp^Bu)₂Mo(TePh)₂is not obtained in the presence of

t

excess Ph₂Te₂at 120 ЊC (Scheme 8). (Cp^Bu)₂Mo(TePh)₂is,

t

nevertheless, readily obtained by the reaction of (Cp^Bu)₂Mo-

(CO) with Ph₂Te₂at room temperature (Scheme 8); likewise,

t

Fig. 10 Molecular structure of (Cp^Bu)₂Mo(η²-S₂) (the selenium

t

analogue has a similar structure).

(Cp^Bu)₂Mo(SPh)₂and (Cp^Bu)₂Mo(SePh)₂may be obtained

t

from the reactions of (Cp^Bu)₂Mo(CO) with Ph₂E₂(E = S,

Se).⁶⁶

t

The molecular structures of (Cp^Bu)₂Mo(EPh)H (E = Se, Te)

t

and (Cp^Bu)₂Mo(SPh)₂have been determined by X-ray diﬀrac-

tion as shown in Figs. 13 and 14. Selected metrical data listed in

Table 4, which indicate that the angle at the chalcogen decreases

t

in the sequence S > Se > Te. For the sulﬁdo complex, (Cp^Bu)₂-

Fig. 11 Resonance structures for Mo(η²-E₂) interactions.

t

Fig. 12 Molecular structure of [(Cp^Bu)₂Mo(µ-Se)]₂. There are two crystallographically independent half-molecules in the asymmetric unit, one

of which is disordered. Selected bond lengths (Å) and angles (Њ) are only listed for the ordered molecule: Mo(1)–Se(1) 2.611(2) Å; Se(1)–Mo(1)–

Se(1Ј) 74.24(6), Mo(1)–Se(1)–Mo(1Ј) 105.76(6).

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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t

Table 4 Selected bond lengths and angles for (Cp^Bu)₂Mo(SPh)₂, (Cp^Bu)₂Mo(EPh)H and (E = Se, Te)

Complex

d(Mo–E)/Å

d(E–C)/Å

Mo–E–C/Њ

E–Mo–X/Њ

t

(Cp^Bu)₂Mo(SPh)₂

2.504(1)

2.620(1)

2.799(1)

1.782(3)

1.914(10)

2.146(10)

113.6(1)

105.8(3)

102.9(3)

73.3

84.4

77.3

t

(Cp^Bu)₂Mo(SePh)H

t

(Cp^Bu)₂Mo(TePh)H

Scheme 8

t

Fig. 13 Molecular structure of (Cp^Bu)₂Mo(TePh)H (the selenium

analogue is similar).

t

Fig. 14 Molecular structure of (Cp^Bu)₂Mo(SPh)₂.

t

Mo(SPh)₂, the phenyl groups adopt an exo conformation which

minimizes (i) destabilizing interactions between the lone pairs

of electrons and the d²pair of electrons on the molybdenum

[(Cp^Bu)₂Mo(PhEMe)H]I are characterized by ¹H NMR signals

2

at δ Ϫ8.80 (E = S), Ϫ9.12 (E = Se, J_Se–H= 14 Hz) and Ϫ9.39

2

ppm (E = Te, J_Te–H= 38 Hz), and by ν(Mo–H) IR absorptions

center,⁶⁷and (ii) steric interactions between the two phenyl

at 1898 (E = S), 1895 (E = Se) and 1893 cm^Ϫ1(E = Te). The

t

groups. In contrast, the phenyl groups of (Cp^Bu)₂Mo(EPh)H

(E = Se, Te) are directed toward the hydride ligand. Presumably,

in the presence of the small hydride ligand, the phenyl group

adopts an endo conformation to minimize steric interactions

[Mo(PhEMe)] moieties in [(Cp^Bu)₂Mo(PhSeMe)H]I and

t

[(Cp^Bu)₂Mo(PhTeMe)H]I are also characterized by ⁷⁷Se NMR

and ¹²⁵Te NMR spectroscopic signals at δ 244 ppm (w_1/2= 42

Hz) and δ 547 ppm (w_1/2= 102 Hz), respectively. These values

with the tert–butyl substituents of the cyclopentadienyl ligands.

are shifted substantially downﬁeld from the signals of both (i)

t

The chalcogenolate complexes (Cp^Bu)₂Mo(EPh)₂(E = S, Se,

the parent chalcogenolate–hydride complexes, (Cp^Bu)₂Mo-

t

Te) react readily with MeI to yield (Cp^Bu)₂MoI₂and PhEMe,

(SePh)H (Ϫ117 ppm) and (Cp^Bu)₂Mo(TePh)H (Ϫ213 ppm),

t

a transformation that has precedence.⁶⁸Of substantially more

and (ii) the bis(chalcogenolate) complexes (Cp^Bu)₂Mo(SePh)₂

t

interest, the corresponding reactions of the hydride derivatives

(Ϫ83 ppm) and (Cp^Bu)₂Mo(TePh)₂(Ϫ195 ppm).

t

(Cp^Bu)₂Mo(EPh)H (E = S, Se, Te) with MeI give the chalco-

The ¹H NMR spectra of [(Cp^Bu)₂Mo(PhEMe)H]I show

interesting diﬀerences in the range 4–6 ppm, i.e. that of the

C₅H₄Bu^tring protons (Fig. 15). Speciﬁcally, the ¹H NMR

t

genoether adducts [(Cp^Bu)₂Mo(PhEMe)H]I, rather than

t

(Cp^Bu)₂Mo(H)(I) (Scheme 8).⁶⁹The [Mo–H] moieties in

1740

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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t

Scheme 9 Chemical exchange between the two Cp^Buligands of

t

[(Cp^Bu)₂Mo(PhEMe)H]^ϩ. Unless the structure of [(Cp^Bu)₂Mo(PhE-

Me)H]^ϩis one in which the phenyl and methyl groups are located in

positions that are related to those of the inverted conﬁguration by

reﬂection of the E(Ph)Me ligand in the molybdenocene coordination

t

plane, chemical exchange between the two Cp^Buligands requires both

rotation about the M–E bond and inversion at the chalcogen (rotation

t

of the Cp^Buabout the Mo–Cp^Bucentroid is assumed to be facile).

Other sequences of rotation and inversion are also feasible.

t

Fig. 15 ¹H NMR spectra of [(Cp^Bu)₂Mo(PhEMe)H]I (E = S, Se, Te);

t

resonances marked * and # correspond to (Cp^Bu)₂MoI₂and (Cp^Bu)₂-

Mo(H)I impurities that are formed due to dissociation of PhEMe. For

clarity, the hydride resonances are not illustrated.

The more facile exchange for the [(Cp^Bu)₂Mo(PhSMe)H]I

derivative also indicates that inversion, and not rotation about

the M–E bond, is the rate determining factor. Speciﬁcally,

rotation about the Mo–E(Ph)Me bond would be expected to

t

more facile for the tellurium derivative, [(Cp^Bu)₂Mo(Ph-

TeMe)H]I, due to the longer Mo–Te bond minimizing inter-

Bu^t

spectrum of [(Cp )₂Mo(PhSMe)H]I shows four signals for the

t

ring protons, while that of [(Cp^Bu)₂Mo(PhTeMe)H]I exhibits

Bu^t

t

actions between the telluroether substituents and the Cp

eight signals. The selenium analogue [(Cp^Bu)₂Mo(PhSeMe)-

ligand during rotation. Finally, it should be noted that chemical

1

t

H]I, exhibits intermediate characteristics, with the H NMR

exchange of the two Cp^Buligands can also be achieved by

dissociation of the chalcogenoether. However, if this were to be

the mechanism for exchange then one would expect the oppos-

spectrum showing four signals, one of which is very broad

(Fig. 15).⁷⁰Furthermore, two of the eight ¹H NMR signals for

t

[(Cp^Bu)₂Mo(PhTeMe)H]I in the range 4–6 ppm coalesce at

60 ЊC (Fig. 15), consistent with an exchange process.⁷¹The

Bu^t

ite trend to that observed, i.e. the [(Cp )₂Mo(PhSMe)H]I

t

derivative, with the expected stronger Mo–E(Ph)Me bond,

would be the derivative that should exhibit eight ring proton

signals. Thus, the available evidence suggests that the facility

room temperature static H NMR spectrum of [(Cp^Bu)₂Mo-

(PhTeMe)H]I, consisting of eight ring proton signals and

two tert-butyl signals demonstrates clearly that the two

1

t

of chemical exchange of the two Cp^Buligands in [(Cp^Bu)₂Mo-

(PhEMe)H]I is dictated by the barrier to inversion of the

chalcogen. In support of this suggestion, calculations on a

series of sulfonium, selenonium, and telluronium ylides,

R₂E(CRЈ₂), indicate that the barrier to inversion increases in the

sequence S < Se < Te.^74,75

Bu^t

Cp ligands are inequivalent. Although none of the complexes

has been structurally characterized, the inequivalence of the

t

two Cp^Buligands is reasonably attributed to the pyramidal

chalcogen center of the E(Ph)Me ligand—thus, regardless of

t

the location of the phenyl and methyl groups, the two Cp^Bu

ligands can never be related by a mirror plane. Chemical

t

exchange of the two Cp^Buligands requires inversion at the

chalcogen and, depending upon the location of the phenyl and

methyl groups, rotation about the Mo–E bond (see, for

example, Scheme 9). Speciﬁcally, rotation is required unless the

phenyl and methyl groups are located in positions that are

related to those of the inverted conﬁguration by reﬂection of

the E(Ph)Me ligand in the molybdenocene coordination plane.

For all other conformations, partial rotation about the Mo–E

Experimental section

General considerations

All manipulations were performed using a combination of

glovebox, high-vacuum or Schlenk techniques.⁷⁶Solvents

were puriﬁed and degassed by standard procedures and

all commercially available reagents were used as received,

unless otherwise noted in the experimental procedures. IR

spectra were recorded as KBr pellets or neat samples on Perkin-

Elmer 1430 or 1600 spectrophotometers and are reported

in cm^Ϫ1. Mass spectra were obtained on a Nermag R10-10 mass

spectrometer using chemical ionization (CH₄) techniques.

Elemental analyses were measured using a Perkin-Elmer 2400

bond is also required to eﬀect exchange. The observation that

t

exchange is more facile for [(Cp^Bu)₂Mo(PhSMe)H]I than

t

[(Cp^Bu)₂Mo(PhTeMe)H]I is consistent with the observation

that inversion barriers tend to increase as one descends the

Periodic Table. For example, the inversion barrier of NH₃

is considerably lower than that of PH₃due to the reduced

tendency of phosphorus to rehybridize and obtain a planar

transition state.⁷²Likewise, inversion at the three-coordinate

oxygen in the bis(pyrazolyl)borato complex [(Ph₂CHO)-

1

CHN Elemental Analyzer. H NMR spectra were recorded on

Varian VXR-200 (200.057 MHz), VXR-300 (299.943 MHz),

and VXR-400 (399.95 MHz) spectrometers. ¹³C, ³¹P, ⁷⁷Se

and ¹²⁵Te NMR spectra were recorded on a Varian VXR-300

t

i

Bp^{Bu ,Pr}]ZnI is more facile than that at sulfur in [(Ph₂CHS)-

t

i

Bp^{Bu ,Pr}]ZnI.⁷³

spectrometer. H and ¹³C chemical shifts are reported in ppm

1

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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1

relative to SiMe₄(δ = 0) and were referenced internally with

respect to the protio solvent impurity (δ = 7.15 for C₆D₅H and

δ = 7.26 for CHCl₃) and the ¹³C resonances (δ = 128.0 for

C₆D₆and δ = 77.0 for CDCl₃) respectively. ³¹P NMR chemical

shifts are reported in ppm relative to 85% H₃PO₄(δ = 0) and

were referenced using P(OMe₃) (δ = 141.0) as external standard.

⁷⁷Se chemical shifts are reported in ppm relative to neat

Me₂Se (δ = 0) and were referenced using a solution of Ph₂Se₂

in C₆D₆(δ = 460) as external standard.^{77 125}Te chemical shifts

are reported in ppm relative to neat Me₂Te (δ = 0) and were

referenced using a solution of Ph₂Te₂in CDCl₃(δ = 420.8)⁷⁸or

a solution of Te(OH)₆(1.74 M in D₂O, δ = 712)^79,80as external

standard. All coupling constants are reported in Hz.

105.0 [d, J_C–H= 184, 2 C of C₅H₄{C(CH₃)₃}], 120.7 [s, 1 C of

C₅H₄{C(CH₃)₃}].

t

Synthesis of (Cp^Bu)₂MoBr₂

A solution of (Cp^Bu)₂MoH₂(200 mg, 0.59 mmol) in toluene (15

mL) was treated with CH₂Br₂(800 mg, 10.01 mmol) for 4 hours

at 80 ЊC. After this period, the mixture was concentrated to

ca. 1 mL and ﬁltered. The precipitate obtained was washed with

t

Bu^t

pentane (2 × 5 mL) and dried in vacuo to give (Cp )₂MoBr₂as

a brown solid (130 mg, 44%). Analysis calcd. for C₁₈H₂₆Br₂Mo:

C, 43.4%; H, 5.3%. Found: C, 44.0%; H, 5.0%. IR Data (KBr

disk, cm^Ϫ1): 3111 (w), 3064 (vs), 2959 (vs), 2907 (s), 2867 (s),

1486 (m), 1461 (m), 1395 (s), 1360 (m), 1266 (m), 1207 (w), 1152

(m), 1061 (w), 1045 (w), 1024 (w), 972 (w), 932 (w), 906 (w),

859 (w), 837 (vs), 663 (w), 588 (w), 478 (w), 448 (w), 414 (w).

¹H NMR (CDCl₃): 1.15 [s, C₅H₄{C(CH₃)₃}], 5.39 [t, ³J_H–H= 2.5,

t

Synthesis of (Cp^Bu)₂MoH₂

A mixture of MoCl₅(16.5 g, 60.39 mmol), NaBH₄(11.4 g,

t

301.34 mmol) and (Cp^Bu)Li⁸¹(31.0 g, 241.92 mmol) was treated

with toluene (100 mL) and THF (300 mL) at Ϫ78 ЊC. The

mixture was allowed to warm to room temperature and reﬂuxed

overnight. After this period, all the volatile components were

removed in vacuo. The residue was dissolved in THF (100 mL)

and HCl(aq) (1000 mL of 0.5 M) was added very slowly at

0 ЊC (CAUTION!! H₂is liberated vigorously). The mixture

was allowed to warm to room temperature and the THF

was removed in vacuo and the aqueous mixture was ﬁltered,

retaining the ﬁltrate. The sticky residue was dissolved in THF

(ca. 50 mL) and HCl(aq) (ca. 200 mL of 0.5 M) was added.

The THF was removed in vacuo and the aqueous mixture was

ﬁltered, retaining the ﬁltrate. The THF/HCl(aq) extraction

procedure was repeated one more time, and the combined

ﬁltrate was adjusted to pH 7–8 with NaOH solution (6 M),

thereby depositing a gray–green solid. The solid was isolated by

ﬁltration and dried overnight in vacuo. The gray–green residue

was extracted into THF until the ﬁltrate was colorless (ca. 300

mL), and the solvent was removed from the combined ﬁltrate

in vacuo. The yellow–brown residue was extracted into pentane

(ca. 500 mL) and ﬁltered. The solvent was removed from the

2 H of C₅H₄{C(CH₃)₃}], 5.88 [t, J_H–H= 2.5, 2 H of C₅H₄-

3

{C(CH₃)₃}]. ¹³C NMR (CDCl₃): 31.1 [q, J_C–H= 126, C₅H₄{C-

1

(CH₃)₃}], 33.2 [s, C₅H₄{C(CH₃)₃}], 97.5 [d, J_C–H= 184, 2 C of

C₅H₄{C(CH₃)₃}], 104.3 [d, ¹J_C–H= 178, 2 C of C₅H₄{C(CH₃)₃}],

117.1 [s, 1 C of C₅H₄{C(CH₃)₃}].

t

Synthesis of (Cp^Bu)₂MoI₂

A solution of (Cp^Bu)₂MoO (150 mg, 0.42 mmol) in toluene

(15 mL) was treated with Me₃SiI (212 mg, 1.06 mmol) for

30 minutes at room temperature. After this period, the mixture

was concentrated to 1 mL and ﬁltered. The precipitate was

t

washed with pentane (2 × 5 mL) and dried in vacuo to give

t

(Cp^Bu)₂MoI₂as a brown solid (220 mg, 88%). Analysis calcd.

for C₁₈H₂₆I₂Mo: C, 36.5%; H, 4.4%. Found: C, 36.9%; H,

5.0%. IR Data (KBr disk, cm^Ϫ1): 3092 (vs), 2953 (vs), 2898 (vs),

2907 (s), 2863 (s), 1478 (s), 1459 (s), 1414 (s), 1365 (vs), 1273 (s),

1193 (m), 1152 (s), 1074 (m), 1023 (w), 951 (w), 904 (m),

880 (vs), 840 (m), 804 (s), 658 (m), 595 (w), 472 (w), 407 (w).

¹H NMR (C₆D₆): 0.77 [s, C₅H₄{C(CH₃)₃}], 4.94 [br s, 2 H of

C₅H₄{C(CH₃)₃}], 5.51 [br s, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR

1

Bu^t

(C₆D₆): 31.0 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.7 [s, C₅H₄-

ﬁltrate to give (Cp )₂MoH₂as a yellow–brown solid (9.1 g,

1

{C(CH₃)₃}], 92.3 [d, J_C–H= 187, 2 C of C₅H₄{C(CH₃)₃}],

44%). Analysis calcd. for C₁₈H₂₈Mo: C, 63.5%; H, 8.3%. Found:

C, 63.2%; H, 7.9%. MS: m/z = 339 (M^ϩϪ 3). IR Data (KBr

disk, cm^Ϫ1): 3097 (w), 3077 (m), 2960 (vs), 2903 (s), 2864 (s),

1906 (m) [ν(Mo–H)], 1852 (br, w) [ν(Mo–H)], 1483 (s), 1457 (s),

1389 (s), 1357 (s), 1270 (s), 1194 (m), 1145 (m), 1067 (w), 1038

(s), 1015 (s), 909 (s), 859 (w), 832 (m), 801 (m), 762 (vs), 678 (m),

1

99.5 [d, J_C–H= 180, 2 C of C₅H₄{C(CH₃)₃}], 114.5 [s, 1 C

of C₅H₄{C(CH₃)₃}].

t

Synthesis of (Cp^Bu)₂Mo(H)(I)

A solution of (Cp^Bu)₂MoH₂(500 mg, 1.47 mmol) in toluene (10

mL) was treated with CH₃I (1.00 g, 7.05 mmol) for 3 days at

room temperature. After this period, the volatile components

were removed, and the residue was washed with pentane (3 × 10

t

1

600 (w), 544 (w), 468 (w), 405 (w). H NMR (C₆D₆): Ϫ8.78

[s, Mo(H)₂], 1.18 [s, C₅H₄{C(CH₃)₃}], 4.23 [br s, 2 H of

C₅H₄{C(CH₃)₃}], 4.40 [br s, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR

t

1

(C₆D₆): 30.6 [s, C₅H₄{C(CH₃)₃}], 32.0 [q, J_C–H= 126,

mL) and dried in vacuo to give (Cp^Bu)₂Mo(H)(I) as a dark

brown solid (545 mg, 80%). Analysis calcd. for C₁₈H₂₇IMo:

C, 46.4%; H, 5.8%. Found: C, 46.2%; H, 5.9%. MS: m/z = 468

(M^ϩ). IR Data (KBr disk, cm^Ϫ1): 3083 (m), 2958 (vs), 2901 (s),

2865 (s), 1876 (w) [ν(Mo–H)], 1484 (s), 1459 (s), 1390 (m), 1361

(s), 1268 (s), 1197 (m), 1148 (m), 1038 (s), 901 (m), 843 (m), 770

(s), 694 (w), 652 (m), 595 (w), 477 (w), 406 (w). ¹H NMR

(C₆D₆): Ϫ8.93 [s, Mo–H], 1.19 [s, C₅H₄{C(CH₃)₃}], 3.85 [br s,

1 H of C₅H₄{C(CH₃)₃}], 3.97 [br s, 1 H of C₅H₄{C(CH₃)₃}],

4.72 [br s, 1 H of C₅H₄{C(CH₃)₃}], 4.80 [br s, 1 H of C₅H₄-

{C(CH₃)₃}]. ¹³C NMR (C₆D₆): 31.6 [s, C₅H₄{C(CH₃)₃}], 32.2

1

C₅H₄{C(CH₃)₃}], 72.3 [d, J_C–H= 177, 2 C of C₅H₄{C(CH₃)₃}],

1

74.9 [d, J_C–H= 175, 2 C of C₅H₄{C(CH₃)₃}], 116.8 [s, 1 C of

C₅H₄{C(CH₃)₃}].

t

Synthesis of (Cp^Bu)₂MoCl₂

t

A solution of (Cp^Bu)₂MoH₂(2.04 g, 5.99 mmol) in toluene

(40 mL) was treated with CCl₄(5.00 g, 32.50 mmol) at room

temperature for 1 day, giving a brown precipitate. After this

period, the mixture was cooled to 0 ЊC and ﬁltered. The precipi-

tate obtained was washed with pentane (3 × 10 mL) and dried

1

Bu^t

[q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 75.0 [d, J_C–H= 183, 1 C of

C₅H₄{C(CH₃)₃}], 81.9 [d, J_C–H= 177, 1 C of C₅H₄{C(CH₃)₃}],

82.0 [d, J_C–H= 179, 1 C of C₅H₄{C(CH₃)₃}], 94.8 [d, J_C–H

177, 1 C of C₅H₄{C(CH₃)₃}], 123.0 [s, 1 C of C₅H₄{C(CH₃)₃}].

in vacuo to give (Cp )₂MoCl₂as a brown solid (2.25 g, 92%).

1

Analysis calcd. for C₁₈H₂₆Cl₂Mo: C, 52.8%; H, 6.4%. Found:

C, 52.8%; H, 5.9%. MS: m/z = 410 (M^ϩ). IR Data (KBr disk,

cm^Ϫ1): 3109 (m), 3066 (vs), 2957 (vs), 2907 (vs), 2868 (s), 1486

(s), 1461 (s), 1394 (s), 1361 (s), 1267 (s), 1206 (w), 1152 (m),

1045 (m), 1024 (m), 976 (w), 934 (w), 906 (m), 860 (w), 835 (vs),

666 (m), 589 (w), 479 (w), 449 (w), 412 (w). ¹H NMR (CDCl₃):

1

=

t

Synthesis of (Cp^Bu)₂MoMe₂

t

A solution of (Cp^Bu)₂MoCl₂(300 mg, 0.73 mmol) in Et₂O (20

mL) was treated with MeMgI (0.98 mL of 3.0 M in Et₂O, 2.94

mmol). The mixture was stirred at room temperature for 1 hour,

after which period the volatile components were removed

in vacuo. The residue was extracted into pentane, ﬁltered, con-

3

1.16 [s, C₅H₄{C(CH₃)₃}], 5.34 [t, J_H–H= 2.5, 2 H of C₅H₄-

3

{C(CH₃)₃}], 5.82 [t, J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C

1

NMR (CDCl₃): 31.0 [q, J_C–H= 127, C₅H₄{C(CH₃)₃}], 33.3 [s,

1

C₅H₄{C(CH₃)₃}], 99.2 [d, J_C–H= 185, 2 C of C₅H₄{C(CH₃)₃}],

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

1743

View Article Online

t

centrated and cooled to Ϫ78 ЊC to give (Cp^Bu)₂MoMe₂as a red

period, the volatile components were removed, and the residue

solid (190 mg, 74%). Analysis calcd. for C₂₀H₃₂Mo: C, 65.2%;

H, 8.8%. Found: C, 64.9%; H, 9.1%. IR Data (KBr disk, cm^Ϫ1):

3109 (w), 2951 (vs), 2900 (vs), 2870 (vs), 1481 (s), 1458 (s), 1410

(s), 1391 (m), 1360 (vs), 1273 (vs), 1197 (m), 1176 (m), 1150 (s),

1069 (m), 1043 (s), 914 (s), 882 (vs), 855 (s), 812 (m), 660 (m),

598 (w), 472 (m), 404 (m). ¹H NMR (C₆D₆): 0.08 [s, Mo(CH₃)₂],

1.02 [s, C₅H₄{C(CH₃)₃}], 4.02 [br s, 2 H of C₅H₄{C(CH₃)₃}],

4.29 [br s, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (C₆D₆): Ϫ9.7 [q,

was extracted into pentane. The solvent was removed from

t

the ﬁltrate, and the residue was dried in vacuo to give (Cp^Bu)₂-

Mo(CO) as a green solid (235 mg, 88%). Analysis calcd. for

C₁₉H₂₆OMo: C, 62.3%; H, 7.2%. Found: C, 61.4%; H, 7.5%. IR

Data (KBr disk, cm^Ϫ1): 3095 (w), 2956 (vs), 2900 (s), 2863 (m),

᎐

1907 (vs) [ν(C᎐O)], 1479 (m), 1459 (m), 1359 (m), 1263 (m),

᎐

1200 (w), 1138 (w), 1083 (w), 1042 (w), 1010 (w), 903 (m),

871 (w), 809 (w), 787 (w), 654 (w), 598 (w), 576 (w), 482 (s). ¹H

NMR (C₆D₆): 1.10 [s, C₅H₄{C(CH₃)₃}], 3.76 [t, ³J_H–H= 2, 2 H of

1

¹J_C–H= 128, Mo(CH₃)₂], 31.6 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}],

1

32.5 [s, C₅H₄{C(CH₃)₃}], 89.0 [d, J_C–H= 176, 2 C of C₅H₄-

C₅H₄{C(CH₃)₃}], 4.37 [t, ³J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}]. ¹³

C

{C(CH₃)₃}], 91.0 [d, ¹J_C–H= 170, 2 C of C₅H₄{C(CH₃)₃}], 109.4

[s, 1 C of C₅H₄{C(CH₃)₃}].

NMR (C₆D₆): 30.8 [s, C₅H₄{C(CH₃)₃}], 32.1 [q, J_C–H= 125,

1

C₅H₄{C(CH₃)₃}], 74.3 [d, J_C–H= 172, 2 C of C₅H₄{C(CH₃)₃}],

1

74.6 [d, J_C–H= 178, 2 C of C₅H₄{C(CH₃)₃}], 111.2 [s, 1 C of

t

1

Synthesis of (Cp^Bu)₂Mo(CH₂SiMe₃)₂

C₅H₄{C(CH₃)₃}], 246.9 [s, Mo(CO)]. H NMR (C₆D₆): 1.10 [s,

3

C₅H₄{C(CH₃)₃}], 3.76 [t, J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}],

t

A solution of (Cp^Bu)₂MoCl₂(200 mg, 0.49 mmol) in Et₂O

3

4.37 [t, J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (C₆D₆):

30.8 [s, C₅H₄{C(CH₃)₃}], 32.1 [q, ¹J_C–H= 125, C₅H₄{C(CH₃)₃}],

(15 mL) was treated with Me₃SiCH₂MgCl (1.5 mL of 1.0 M in

Et₂O, 1.50 mmol). The mixture was stirred at room temperature

for 1 hour, after which period the volatile components

1

74.3 [d, J_C–H= 172, 2 C of C₅H₄{C(CH₃)₃}], 74.6 [d, J_C–H

=

178, 2 C of C₅H₄{C(CH₃)₃}], 111.2 [s, 1 C of C₅H₄{C(CH₃)₃}],

246.9 [s, Mo(CO)].

were removed in vacuo. The residue was extracted into pentane,

t

ﬁltered, concentrated and cooled to Ϫ78 ЊC to give (Cp^Bu)₂-

Mo(CH₂SiMe₃)₂as a red solid (140 mg, 56%). Analysis calcd.

for C₂₆H₄₈Si₂Mo: C, 60.9%; H, 9.4%. Found: C, 60.6%; H,

9.1%. IR Data (KBr disk, cm^Ϫ1): 2946 (vs), 2901 (s), 2873 (s),

2838 (s), 2703 (w), 1480 (m), 1461 (m), 1437 (w), 1411 (w), 1395

(w), 1363 (s), 1271 (s), 1256 (s), 1245 (s), 1201 (w), 1152 (w),

1047 (w), 1013 (w), 968 (m), 922 (w), 886 (s), 854 (vs), 820 (vs),

Bu^t

Synthesis of (Cp )₂Mo(PMe₃)

t

A mixture of (Cp^Bu)₂MoCl₂(200 mg, 0.49 mmol), Na (25 mg,

1.09 mmol) and Hg (1 mL) in THF (20 mL) was treated with

PMe₃(0.5 mL) and stirred for 4 hours at room temperature.

After this period, the volatile components were removed,

and the residue was extracted into pentane. The solvent was

1

785 (s), 746 (s), 730 (s), 671 (s), 608 (w), 561 (w), 461 (w). H

NMR (C₆D₆): Ϫ0.34 [s, CH₂Si(CH₃)₃], 0.29 [s, CH₂Si(CH₃)₃],

removed from the ﬁltrate, and the residue was dried in vacuo to

t

3

1.02 [s, C₅H₄{C(CH₃)₃}], 4.35 [t, J_H–H= 2.5, 2 H of C₅H₄-

give (Cp^Bu)₂Mo(PMe₃) as a red–orange solid (145 mg, 72%).

Analysis calcd. for C₂₁H₃₅PMo: C, 60.9%; H, 8.5%. Found: C,

60.3%; H, 8.6%. IR Data (KBr disk, cm^Ϫ1): 3094 (m), 2955 (vs),

2902 (vs), 1458 (s), 1421 (m), 1357 (s), 1265 (s), 1193 (m), 1136

(m), 1040 (m), 1002 (m), 944 (vs), 830 (vs), 761 (s), 703 (s), 657

{C(CH₃)₃}], 4.56 [br s, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR

(C₆D₆): Ϫ15.0 [t, ¹J_C–H= 114, CH₂Si(CH₃)₃], 4.5 [q, ¹J_C–H= 117,

1

CH₂Si(CH₃)₃], 31.6 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 33.0 [s,

1

C₅H₄{C(CH₃)₃}], 85.5 [d, J_C–H= 181, 2 C of C₅H₄{C(CH₃)₃}],

1

2

91.3 [d, J_C–H= 173, 2 C of C₅H₄{C(CH₃)₃}], 116.0 [s, 1 C of

(s), 462 (w), 413 (m). ¹H NMR (C₆D₆): 0.98 [d, J_P–H= 7,

C₅H₄{C(CH₃)₃}].

P(CH₃)₃], 1.24 [s, C₅H₄{C(CH₃)₃}], 3.34 [dt, ³J_P–H= 6, ³J_H–H= 2,

2 H of C₅H₄{C(CH₃)₃}], 4.15 [br s, 2 H of C₅H₄{C(CH₃)₃}]. ¹³

C

t

NMR (C₆D₆): 23.9 [qd, ¹J_C–H= 127, ¹J_P–C= 23, P(CH₃)₃], 31.4 [s,

C₅H₄{C(CH₃)₃}], 32.2 [q, ¹J_C–H= 125, C₅H₄{C(CH₃)₃}], 67.1 [d,

¹J_C–H= 172, 2 C of C₅H₄{C(CH₃)₃}], 72.1 [d, ¹J_C–H= 174, 2 C of

C₅H₄{C(CH₃)₃}], 107.1 [s, 1 C of C₅H₄{C(CH₃)₃}]. ³¹P NMR

(C₆D₆): 8.5 [s].

Synthesis of (Cp^Bu)₂Mo(CH₂Ph)₂

t

A solution of (Cp^Bu)₂MoCl₂(250 mg, 0.61 mmol) in Et₂O (15

mL) was treated with PhCH₂MgCl (1.8 mL of 1.0 M in Et₂O,

1.80 mmol). The mixture was stirred at room temperature

for 1 hour, after which period the volatile components were

t

removed in vacuo. The residue was extracted into pentane,

Synthesis of (Cp^Bu)₂Mo(ꢀ²-C₂H₄)

t

ﬁltered, concentrated and cooled to Ϫ78 ЊC to give (Cp^Bu)₂-

Mo(CH₂Ph)₂as a red solid (220 mg, 69%). Analysis calcd. for

C₃₂H₄₀Mo: C, 73.8%; H, 7.7%. Found: C, 72.9%; H, 7.7%. IR

Data (KBr disk, cm^Ϫ1): 3115 (m), 3063 (s), 3011 (s), 2950 (vs),

2900 (vs), 2864 (vs), 1591 (vs), 1482 (vs), 1458 (vs), 1419 (s),

1393 (s), 1359 (vs), 1309 (m), 1267 (vs), 1205 (vs), 1178 (s), 1150

(s), 1074 (m), 1028 (vs), 994 (m), 946 (m), 917 (s), 894 (vs), 868

(s), 854 (s), 841 (s), 810 (m), 784 (vs), 756 (vs), 698 (vs), 598 (m),

546 (vs), 460 (m), 405 (s). ¹H NMR (C₆D₆): 0.76 [s, C₅H₄-

t

A mixture of (Cp^Bu)₂MoCl₂(200 mg, 0.49 mmol), Na (25 mg,

1.09 mmol) and Hg (1 mL) in THF (15 mL) was stirred under

C₂H₄(0.1 atm) for 1 day at room temperature. After this period,

the volatile components were removed, and the residue was

extracted into pentane. The solvent was removed from the

t

ﬁltrate, and the residue was dried in vacuo to give (Cp^Bu)₂-

Mo(η²-C₂H₄) as a dark brown solid (50 mg, 28%). IR Data

(KBr disk, cm^Ϫ1): 3099 (w), 3059 (w), 2954 (vs), 2898 (vs), 2862

(vs), 1479 (s), 1458 (s), 1385 (m), 1357 (s), 1266 (s), 1199 (w),

1145 (s), 1050 (m), 1030 (m), 910 (m), 878 (s), 841 (m), 797 (s),

3

{C(CH₃)₃}], 2.36 [s, CH₂Ph], 4.20 [t, J_H–H= 2, 2 H of

3

C₅H₄{C(CH₃)₃}], 4.30 [t, J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}],

3

1

6.99 [t, J_H–H= 7, 1 H of CH₂C₆H₅], 7.08 [d, J_H–H= 7, 2 H of

712 (w), 649 (m), 453 (w), 408 (m). H NMR (C₆D₆): 1.20 [s,

CH₂C₆H₅], 7.19 [t, J_H–H= 8, 2 H of CH₂C₆H₅]. ¹³C NMR

C₅H₄{C(CH₃)₃}], 1.44 [s, Mo(CH₂CH₂)], 2.92 [t, ³J_H–H= 2, 2 H

3

1

3

(C₆D₆): 16.8 [t, J_C–H= 132, CH₂Ph], 31.5 [q, J_C–H= 126,

of C₅H₄{C(CH₃)₃}], 4.48 [t, J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}].

C₅H₄{C(CH₃)₃}], 32.6 [s, C₅H₄{C(CH₃)₃}], 88.9 [d, ¹J_C–H= 180,

¹³C NMR (C₆D₆): 13.1 [t, J_C–H= 152, Mo(CH₂CH₂)], 31.9 [s,

1

2 C of C₅H₄{C(CH₃)₃}], 94.8 [d, J_C–H= 176, 2 C of C₅H₄-

C₅H₄{C(CH₃)₃}], 32.5 [q, ¹J_C–H= 125, C₅H₄{C(CH₃)₃}], 80.7 [d,

¹J_C–H= 171, 2 C of C₅H₄{C(CH₃)₃}], 82.1 [d, ¹J_C–H= 176, 2 C of

C₅H₄{C(CH₃)₃}], 105.9 [s, 1 C of C₅H₄{C(CH₃)₃}].

{C(CH₃)₃}], 116.9 [s, 1 C of C₅H₄{C(CH₃)₃}], 122.4 [dt,

2

1

¹J_C–H= 160, J_C–H= 7, 1 C of CH₂C₆H₅], 127.6 [dt, J_C–H= 154,

²J_C–H= 7, 2 C of CH₂C₆H₅], 128.1 [dd, J_C–H= 157, J_C–H= 8, 2

1

2

t

Synthesis of (Cp^Bu)₂Mo(ꢀ²-C₂H₂)

C of CH₂C₆H₅], 157.4 [s, 1 C of CH₂C₆H₅].

t

A mixture of (Cp^Bu)₂MoCl₂(200 mg, 0.49 mmol), Na (25 mg,

Bu^t

Synthesis of (Cp )₂Mo(CO)

1.09 mmol) and Hg (1 mL) in THF (20 mL) was stirred under

C₂H₂(0.7 atm) for 4 hours at room temperature. After this

period, the volatile components were removed, and the residue

was extracted into pentane. The solvent was removed from the

t

A mixture of (Cp^Bu)₂MoCl₂(300 mg, 0.73 mmol), Na (36 mg,

1.57 mmol) and Hg (1 mL) in THF (30 mL) was stirred under

CO (1 atm) for 1.5 hours at room temperature. After this

1744

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

View Article Online

t

ﬁltrate to give (Cp^Bu)₂Mo(η²-C₂H₂) as a red–brown oil (140 mg,

to give [(Cp^Bu)₂Mo(PMe₃)Me]I as a yellow–orange solid (125

mg, 93%). Analysis calcd. for C₂₂H₃₈IPMo: C, 47.5%; H, 6.9%.

Found: C, 48.1%; H, 6.1%. IR Data (KBr disk, cm^Ϫ1): 3050

(vs), 2958 (vs), 2906 (vs), 2869 (s), 1484 (s), 1462 (s), 1422 (m),

1396 (s), 1365 (s), 1293 (m), 1272 (m), 1193 (m), 1152 (m), 1072

(m), 952 (vs), 879 (m), 847 (s), 819 (s), 728 (m), 672 (m), 600 (w),

79%). Analysis calcd. for C₂₀H₂₈Mo: C, 65.9%; H, 7.7%. Found:

C, 64.4%; H, 8.1%. IR Data (neat): 3101 (w), 3062 (w), 3022

(w), 2956 (vs), 2899 (s), 2864 (s), 1623 (s) [ν(C᎐C)], 1482 (s),

1458 (s), 1405 (m), 1391 (m), 1359 (vs), 1271 (s), 1200 (w), 1147

(m), 1049 (m), 1031 (m), 1014 (m), 915 (m), 892 (m), 858 (s), 839

᎐

1

3

(s), 828 (m), 794 (s), 662 (w), 642 (m), 597 (w), 461 (w). H

462 (w), 413 (m). H NMR (CDCl₃): Ϫ0.09 [d, J_P–H= 8, Mo-

(CH₃)], 1.21 [s, C₅H₄{C(CH₃)₃}], 1.69 [d, J_P–H= 9, P(CH₃)₃],

NMR (C₆D₆): 1.25 [s, C₅H₄{C(CH₃)₃}], 3.35 [t, ³J_H–H= 2, 2 H of

2

3

C₅H₄{C(CH₃)₃}], 4.53 [t, J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}],

4.43 [br s, 1 H of C₅H₄{C(CH₃)₃}], 4.91 [br s, 1 H of

7.55 [s, Mo(CHCH)]. ¹³C NMR (C₆D₆): 31.8 [s, C₅H₄{C-

C₅H₄{C(CH₃)₃}], 5.31 [br s, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR

(CH₃)₃}], 32.2 [q, ¹J_C–H= 125, C₅H₄{C(CH₃)₃}], 85.2 [d, ¹J_C–H

=

(CDCl₃): Ϫ17.4 [qd, J_C–H= 130, J_P–C= 16, Mo(CH₃)], 19.2

1 1 1

1

2

172, 4 C of C₅H₄{C(CH₃)₃}], 115.3 [s, 1 C of C₅H₄{C(CH₃)₃}],

[qd, J_C–H= 130, J_P–C= 31, P(CH₃)₃], 31.5 [q, J_C–H= 126,

118.2 [dd, ¹J_C–H= 152, ²J_C–H= 9, Mo(CHCH)].

C₅H₄{C(CH₃)₃}], 33.0 [s, C₅H₄{C(CH₃)₃}], 85.4 [d, ¹J_C–H= 181,

1

1 C of C₅H₄{C(CH₃)₃}], 86.7 [d, J_C–H= 176, 1 C of C₅H₄-

{C(CH₃)₃}], 91.8 [d, J_C–H= 183, 1 C of C₅H₄{C(CH₃)₃}], 96.3

t

1

Synthesis of (Cp^Bu)₂Mo(ꢀ²-MeCN)

1

[d, J_C–H= 174, 1 C of C₅H₄{C(CH₃)₃}], 119.6 [s, 1 C of

t

A mixture of (Cp^Bu)₂MoCl₂(200 mg, 0.49 mmol), Na (25 mg,

C₅H₄{C(CH₃)₃}]. ³¹P NMR (CDCl₃): 11.3 [s].

1.09 mmol) and Hg (1 mL) in MeCN (20 mL) was stirred for

10 minutes at room temperature. After this period, the volatile

components were removed from the mixture, and the residue

Bu^t

Synthesis of [(Cp ) Mo(ꢀ²-MeC᎐NMe)]I

A solution of (Cp^Bu)₂Mo(η²-MeCN) (95 mg, 0.18 mmol) in

C₆H₆(10 mL) was treated with MeI (383 mg, 2.70 mmol) for

2 hours at room temperature, resulting in the formation of

an orange–brown precipitate. The mixture was ﬁltered, and the

᎐

2

t

was extracted into pentane. The solvent was removed from

t

the ﬁltrate to give (Cp^Bu)₂Mo(η²-MeCN) as a red–brown oil

(150 mg, 81%). Analysis calcd. for C₂₀H₂₉NMo: C, 63.3%; H,

7.7%; N, 3.7%. Found: C, 62.1%; H, 7.9%; N, 2.6%. IR Data

precipitate was washed with pentane (2 × 5 mL) and dried

(neat): 3087 (s), 2958 (vs), 2902 (vs), 2864 (vs), 2707 (w), 1777

(vs) [ν(C᎐N)], 1485 (vs), 1461 (vs), 1434 (s), 1390 (s), 1359 (vs),

t

in vacuo to give [(Cp^Bu) Mo(η²-MeC᎐NMe)]I as an orange–

᎐

2

᎐

brown solid (75 mg, 57%). Analysis calcd. for C₂₁H₃₂INMo:

C, 48.4%; H, 6.2%; N, 2.7%. Found: C, 48.2%; H, 6.3%;

N, 2.2%. IR Data (KBr disk, cm^Ϫ1): 3060 (vs), 2962 (vs), 2866

(s), 1747 (s) [ν(CN)], 1479 (s), 1461 (s), 1387 (s), 1363 (s), 1269

(s), 1197 (w), 1149 (m), 1118 (s), 1059 (m), 1033 (m), 935 (m),

904 (s), 883 (s), 844 (s), 822 (s), 734 (w), 670 (w), 626 (w), 466

(w), 424 (w). ¹H NMR (CDCl₃): 1.26 [s, C₅H₄{C(CH₃)₃}], 3.00

1270 (vs), 1199 (m), 1147 (s), 1052 (vs), 942 (s), 912 (s), 895 (s),

879 (s), 860 (s), 832 (s), 810 (s), 791 (s), 786 (s), 665 (m), 628

(vw), 597 (vw), 551 (s), 482 (vw), 463 (w), 432 (w), 416 (w). ¹H

NMR (C₆D₆): 1.24 [s, C₅H₄{C(CH₃)₃}], 2.53 [s, CH₃CN], 3.16

[q, ³J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}], 3.82 [q, ³J_H–H= 2, 1 H of

3

C₅H₄{C(CH₃)₃}], 3.97 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}],

3

4.98 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (C₆D₆):

5

1

[q, J_H–H= 1, CH₃C=NCH₃], 3.56 [q, J_H–H= 1, CH₃C=NCH₃],

21.4 [q, J_C–H= 129, CH₃CN], 31.8 [q, J_C–H= 126, C₅H₄-

3

1

4.40 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 4.54 [q, J_H–H

=

{C(CH₃)₃}], 31.8 [s, C₅H₄{C(CH₃)₃}], 79.9 [d, J_C–H= 174, 1 C

of C₅H₄{C(CH₃)₃}], 82.2 [d, J_C–H= 178, 1 C of C₅H₄{C-

(CH₃)₃}], 86.6 [d, J_C–H= 172, 1 C of C₅H₄{C(CH₃)₃}], 87.4

[d, J_C–H= 176, 1 C of C₅H₄{C(CH₃)₃}], 117.0 [s, 1 C of

3

1

2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.25 [q, J_H–H= 2.5, 1 H of

3

1

C₅H₄{C(CH₃)₃}], 5.62 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}].

¹³C NMR (CDCl₃): 22.0 [q, ¹J_C–H= 132, CH₃C=NCH₃], 31.7 [s,

1

C₅H₄{C(CH₃)₃}], 31.8 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 41.5

[q, J_C–H= 142, CH₃C=NCH₃], 89.9 [d, J_C–H= 177, 1 C of

C₅H₄{C(CH₃)₃}], 168.1 [s, CH₃CN].

1

Bu^t

C₅H₄{C(CH₃)₃}], 91.0 [d, J_C–H= 176, 1 C of C₅H₄{C(CH₃)₃}],

Synthesis of [(Cp )₂Mo(CO)Me]I

1

93.3 [d, J_C–H= 175, 2 C of C₅H₄{C(CH₃)₃}], 121.7 [s, 1 C of

t

A solution of (Cp^Bu)₂Mo(CO) (100 mg, 0.27 mmol) in C₆H₆

C H {C(CH ) }], 189.5 [s, CH C᎐NCH ].

᎐

5

4

3

(10 mL) was stirred with MeI (400 mg, 2.82 mmol) for 1.5 hours

at room temperature to give an orange–brown precipitate. The

mixture was ﬁltered, and the residue was washed with toluene

(3 × 5 mL) and pentane (3 × 5 mL) and dried in vacuo to

t

Synthesis of [(Cp^Bu) Mo(ꢀ²-MeC᎐NEt)]I

᎐

2

t

A solution of (Cp^Bu)₂Mo(η²-MeCN) (100 mg, 0.26 mmol) in

toluene (10 mL) was treated with EtI (608 mg, 3.90 mmol)

for 2 hours at room temperature, resulting in the formation of

a brown precipitate. The mixture was ﬁltered, and the residue

Bu^t

give [(Cp )₂Mo(CO)Me]I as an orange–brown solid (125 mg,

90%). Analysis calcd. for C₂₀H₂₉IOMo: C, 47.3%; H, 5.8%.

Found: C, 47.6%; H, 5.0%. IR Data (KBr disk, cm^Ϫ1): 3110 (w),

was washed with pentane (2 × 5 mL) and dried in vacuo to give

᎐

3048 (m), 2965 (m), 2908 (m), 2011 (vs) [ν(C᎐O)], 1483 (w),

t

᎐

orange–brown solid of [(Cp^Bu) Mo(η²-MeC᎐NEt)]I (30 mg,

᎐

2

1464 (w), 1397 (w), 1371 (w), 1272 (w), 1194 (w), 1150 (w), 1082

(w), 1035 (w), 951 (w), 887 (w), 863 (w), 838 (w), 678 (w),

512 (w), 452 (m). ¹H NMR (CDCl₃): 0.08 [s, Mo(CH₃)], 1.37 [s,

21%). Analysis calcd. for C₂₂H₃₄INMo: C, 49.4%; H, 6.4%;

N, 2.6%. Found: C, 49.0%; H, 6.2%; N, 2.2%. IR Data (KBr

disk, cm^Ϫ1): 3062 (vs), 2963 (vs), 2867 (s), 1764 (s), 1745 (s)

[ν(C᎐N)], 1480 (s), 1460 (s), 1381 (s), 1363 (s), 1338 (m), 1270

(s), 1196 (m), 1146 (s), 1113 (s), 1061 (m), 1033 (s), 963 (m), 933

(m), 905 (s), 881 (s), 844 (s), 819 (s), 670 (m), 622 (w), 465 (w),

3

C₅H₄{C(CH₃)₃}], 5.42 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}],

3

᎐

5.62 [q, J_H–H= 2.5,

1 H of C₅H₄{C(CH₃)₃}], 5.84 [q,

³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.96 [q, J_H–H= 2.5, 1 H

3

of C₅H₄{C(CH₃)₃}]. ¹³C NMR (CDCl₃): Ϫ18.6 [q, J_C–H= 136,

1

3

Mo(CH₃)], 31.9 [q, ¹J_C–H= 127, C₅H₄{C(CH₃)₃}], 32.8 [s, C₅H₄-

424 (w). H NMR (CDCl₃): 1.21 [t, J_H–H= 7, CH C᎐NCH -

᎐

3

2

1

CH₃], 1.27 [s, C₅H₄{C(CH₃)₃}], 3.04 [t, ⁵J_H–H= 1, CH C᎐NCH -

᎐

3 2

{C(CH₃)₃}], 90.8 [d, J_C–H= 175, 1 C of C₅H₄{C(CH₃)₃}], 91.1

CH₃], 3.83 [qq, ³J_H–H= 7, ⁵J_H–H= 1, CH C᎐NCH CH ], 4.43 [q,

[d, ¹J_C–H= 183, 1 C of C₅H₄{C(CH₃)₃}], 93.1 [d, ¹J_C–H= 182, 1 C

᎐

3

2

3

1

³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 4.46 [q, ³J_H–H= 2.5, 1 H of

of C₅H₄{C(CH₃)₃}], 95.8 [d, J_C–H= 191, 1 C of C₅H₄{C-

3

C₅H₄{C(CH₃)₃}], 5.29 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}],

(CH₃)₃}], 127.6 [s, 1 C of C₅H₄{C(CH₃)₃}], 227.0 [s, Mo(CO)].

5.53 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (CD-

3

1

Bu^t

Cl₃): 13.4 [q, J_C–H= 128, CH₃C=NCH₂CH₃], 22.7 [q, J_C–H

=

Synthesis of [(Cp )₂Mo(PMe₃)Me]I

1

132, CH C᎐NCH CH ], 31.7 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}],

᎐

3

2

3

t

A solution of (Cp^Bu)₂Mo(PMe₃) (100 mg, 0.24 mmol) in C₆H₆

31.8 [s, C₅H₄{C(CH₃)₃}], 47.5 [t, J_C–H= 142, CH₃C=NCH₂-

1

(10 mL) was treated with MeI (100 mg, 0.70 mmol) for 0.5

hour at room temperature to give an orange–brown precipitate.

The mixture was ﬁltered, and the precipitate was washed with

benzene (2 × 5 mL) and pentane (2 × 5 mL) and dried in vacuo

CH₃], 89.5 [d, J_C–H= 183, 1 C of C₅H₄{C(CH₃)₃}], 91.3 [d,

¹J_C–H= 183, 1 C of C₅H₄{C(CH₃)₃}], 91.6 [d, ¹J_C–H= 169, 1 C of

1

C₅H₄{C(CH₃)₃}], 92.9 [d, J_C–H= 180, 1 C of C₅H₄{C(CH₃)₃}],

122.0 [s, 1 C of C H {C(CH ) }], 188.4 [s, CH C᎐NCH CH ].

᎐

5

4

3

2

3

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

1745

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t

Synthesis of (Cp^Bu)₂MoO

A mixture of (Cp^Bu)₂MoCl₂(450 mg, 1.10 mmol) and LiOH

(m), 1419 (w), 1367 (m), 1277 (m), 1231 (m), 1196 (w), 1152 (w),

t

1041 (w), 969 (vs), 907 (w), 869 (m), 822 (s), 794 (w), 741 (w),

662 (w), 464 (w). ¹H NMR (CDCl₃): Ϫ0.13 [s, OSi(CH₃)₃],

(270 mg, 11.27 mmol) in toluene (20 mL) was stirred for 4 hours

at 80 ЊC. After this period, the mixture was ﬁltered, and the

volatile components were removed from the ﬁltrate in vacuo.

The residue obtained was extracted into pentane, and the

ﬁltrate was concentrated to ca. 1 mL to give green crystals of

3

1.16 [s, C₅H₄{C(CH₃)₃}], 4.87 [q, J_H–H= 2.5, 1 H of C₅H₄-

3

{C(CH₃)₃}], 5.05 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.31

[q, ³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.93 [q, ³J_H–H= 2.5, 1 H

1

of C₅H₄{C(CH₃)₃}]. ¹³C NMR (CDCl₃): 3.4 [q, J_C–H= 117,

1

Bu^t

OSi(CH₃)₃], 31.1 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.6 [s,

(Cp )₂MoO, which were isolated by ﬁltration and dried in

1

C₅H₄{C(CH₃)₃}], 91.9 [d, J_C–H= 185, 1 C of C₅H₄{C(CH₃)₃}],

vacuo (290 mg, 74%). Analysis calcd. for C₁₈H₂₆OMo: C, 61.0%;

H, 7.4%. Found: C, 61.1%; H, 8.0%. MS: m/z = 357 (M^ϩϩ 1).

IR Data (KBr disk, cm^Ϫ1): 3108 (w), 2959 (vs), 2900 (s), 2864

(s), 1480 (m), 1460 (s), 1421 (m), 1359 (s), 1280 (s), 1202 (w),

1155 (m), 1068 (m), 1048 (m), 910 (m), 877 (s), 838 (vs), 796 (s),

1

93.5 [d, J_C–H= 171,

1 C of C₅H₄{C(CH₃)₃}], 97.4 [d,

¹J_C–H= 183, 1 C of C₅H₄{C(CH₃)₃}], 105.8 [d, J_C–H= 178, 1 C

of C₅H₄{C(CH₃)₃}], 122.8 [s, 1 C of C₅H₄{C(CH₃)₃}], 140.7 [s,

CN].

1

Bu^t

662 (m), 461 (w). H NMR (C₆D₆): 1.33 [s, C₅H₄{C(CH₃)₃}],

Synthesis of (Cp )₂Mo(OSiMe₃)(NCS)

4.79 [t, ³J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}], 4.97 [t, ³J_H–H= 2, 2 H

t

of C₅H₄{C(CH₃)₃}]. ¹³C NMR (C₆D₆): 31.5 [q, J_C–H= 126,

A solution of (Cp^Bu)₂MoO (200 mg, 0.56 mmol) in toluene

1

C₅H₄{C(CH₃)₃}], 32.0 [s, C₅H₄{C(CH₃)₃}], 93.2 [d, ¹J_C–H= 176,

(20 mL) was treated with Me₃SiNCS (74 mg, 0.56 mmol).

The volatile components were removed after stirring for 10

1

2 C of C₅H₄{C(CH₃)₃}], 100.6 [d, J_C–H= 173, 2 C of

C₅H₄{C(CH₃)₃}], 128.0 [s, 1 C of C₅H₄{C(CH₃)₃}].

minutes at room temperature, and the residue was washed with

t

pentane (2 × 5 mL) and dried in vacuo to give (Cp^Bu)₂Mo-

(OSiMe₃)(NCS) as a dark brown solid (255 mg, 93%). Analysis

calcd. for C₂₂H₃₅NOSSiMo: C, 54.4%; H, 7.3%; N, 2.9%.

Found: C, 54.6%; H, 7.3%; N, 2.6%. IR Data (KBr disk, cm^Ϫ1):

3077 (w), 2955 (s), 2905 (m), 2867 (m), 2102 (vs) [ν(CN)], 1485

(w), 1462 (w), 1389 (w), 1360 (w), 1269 (w), 1237 (m), 1202 (w),

1150 (w), 1040 (w), 1023 (w), 964 (vs), 896 (m), 824 (vs), 740

(m), 666 (w), 450 (w), 403 (w). ¹H NMR (C₆D₆): 0.34 [s,

t

Reactions of (Cp^Bu)₂MoO with Me₃SiX (X

؍

Cl, Br, I)

t

A solution of (Cp^Bu)₂MoO (ca. 10 mg) in C₆D₆(1 mL) was

treated with excess Me₃SiX (X = Cl, Br, I). The sample was

monitored by ¹H NMR spectroscopy, which demonstrated that

t

the formation of (Cp^Bu)₂MoX₂was complete within 30 minutes

at room temperature.

3

OSi(CH₃)₃], 0.87 [s, C₅H₄{C(CH₃)₃}], 4.34 [q, J_H–H= 2.5, 1 H

t

Reaction of (Cp^Bu)₂MoO with Me₃SiO₂CMe

3

of C₅H₄{C(CH₃)₃}], 4.64 [q, J_H–H= 2.5, 1 H of C₅H₄{C-

t

3

A solution of (Cp^Bu)₂MoO (ca. 10 mg) in C₆D₆(1 mL) was

(CH₃)₃}], 4.69 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.13 [q,

³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (C₆D₆): 4.0 [q,

treated with excess Me₃SiO₂CMe. The sample was monitored

1

¹J_C–H= 116, OSi(CH₃)₃], 31.0 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}],

1

by H NMR spectroscopy, which demonstrated that the form-

t

1

mation of (Cp^Bu)₂Mo(O₂CMe)₂was complete within 24 hours

32.7 [s, C₅H₄{C(CH₃)₃}], 97.0 [d, J_C–H= 181, 1 C of C₅H₄{C-

1

(CH₃)₃}], 102.4 [d, J_C–H= 180, 1 C of C₅H₄{C(CH₃)₃}], 102.9

at 80 ЊC. H NMR (C₆D₆): 0.98 (s, 18H), 2.07 (s, 3H), 5.22

1

(t, 4H), 5.33 (t, 4H). ¹H NMR (C₆D₆): 0.98 [s, C₅H₄{C(CH₃)₃}],

[d, J_C–H= 178, 1 C of C₅H₄{C(CH₃)₃}], 103.3 [d, J_C–H= 184,

1 C of C₅H₄{C(CH₃)₃}], 123.6 [s, 1 C of C₅H₄{C(CH₃)₃}], 150.2

[s, NCS)].

3

2.07 [s, O₂CCH₃], 5.22 [t, J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}],

5.33 [t, ³J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}].

t

Reaction of (Cp^Bu)₂Mo(OSiMe₃)(CN) with Me₃SiNCS

t

Synthesis of (Cp^Bu)₂Mo(O₃SMe)₂

t

A solution of (Cp^Bu)₂Mo(OSiMe₃)(CN) (ca. 10 mg) in C₆D₆

t

A solution of (Cp^Bu)₂MoO (200 mg, 0.56 mmol) in toluene

(20 mL) was treated with Me₃SiO₃SMe (190 mg, 1.13 mmol)

for 1 hour at room temperature. After this period, the mixture

was concentrated to ca. 1 mL and ﬁltered. The precipitate

(1 mL) was treated with Me₃SiNCS (excess) at room tem-

perature. The sample was monitored by ¹H NMR spectroscopy,

t

which demonstrated the formation of (Cp^Bu)₂Mo(SCN)CN

to be complete within 5 hours. ¹H NMR (CDCl₃): 1.28 [s,

was washed with pentane (2 × 5 mL) and dried in vacuo to give

3

t

(Cp^Bu)₂Mo(O₃SMe)₂as an olive-green solid (225 mg, 76%).

Analysis calcd. for C₂₀H₃₂O₆S₂Mo: C, 45.5%; H, 6.1%. Found:

C, 45.9%; H, 6.4%. IR Data (KBr disk, cm^Ϫ1): 3107 (s), 2960 (s),

2909 (m), 2876 (m), 1491 (s), 1464 (m), 1419 (m), 1366 (m), 1325

(m), 1271 (vs), 1197 (s), 1141 (vs), 1013 (vs), 981 (vs), 882 (s),

C₅H₄{C(CH₃)₃}], 5.30 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}],

5.34 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.48 [q, J_H–H

3

=

3

2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.71 [q, J_H–H= 2.5, 1 H of C₅H₄-

{C(CH₃)₃}]. ¹³C{¹H} NMR (CDCl₃): 31.2 [C₅H₄{C(CH₃)₃}],

33.2 [C₅H₄{C(CH₃)₃}], 89.7 [1 C of C₅H₄{C(CH₃)₃}], 95.3 [1 C

of C₅H₄{C(CH₃)₃}], 97.6 [1 C of C₅H₄{C(CH₃)₃}], 98.7 [1 C of

C₅H₄{C(CH₃)₃}], 124.6 [s, Mo(SCN)], 125.5 [1 C of C₅H₄{C-

(CH₃)₃}], 137.1 [Mo-CN].

1

861 (s), 773 (s), 668 (w), 559 (s), 532 (s), 428 (w). H NMR

(CDCl₃): 1.20 [s, C₅H₄{C(CH₃)₃}], 2.69 [s, O₃SCH₃], 5.95 [t,

³J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}], 6.17 [t, ³J_H–H= 2.5, 2 H of

C₅H₄{C(CH₃)₃}]. ¹³C NMR (CDCl₃): 30.6 [q, J_C–H= 127,

1

t

Reaction of (Cp^Bu)₂Mo(OSiMe₃)(NCS) with Me₃SiCN

C₅H₄{C(CH₃)₃}], 33.7 [s, C₅H₄{C(CH₃)₃}], 40.9 [q, ¹J_C–H= 136,

1

t

A solution of (Cp^Bu)₂Mo(OSiMe₃)(NCS) (ca. 10 mg) in C₆D₆

O₃SCH₃], 98.3 [d, J_C–H= 185, 2 C of C₅H₄{C(CH₃)₃}], 104.4

[d, J_C–H= 180, 2 C of C₅H₄{C(CH₃)₃}], 134.3 [s, 1 C of

1

(1 mL) was treated with Me₃SiCN (excess) at room tem-

perature. The sample was monitored by ¹H NMR spectroscopy,

C₅H₄{C(CH₃)₃}].

t

which demonstrated that formation of (Cp^Bu)₂Mo(OSiMe₃)-

(CN) was complete within 30 minutes.

t

Synthesis of (Cp^Bu)₂Mo(OSiMe₃)(CN)

t

A solution of (Cp^Bu)₂MoO (270 mg, 0.76 mmol) in toluene

(20 mL) was treated with Me₃SiCN (100 mg, 1.01 mmol) for

1 hour at room temperature. After this period, the volatile

Bu^t

Reaction of Cp ₂Mo(NCS)₂with Me₃SiCN

A solution of Cp^Bu₂Mo(NCS)₂(ca. 20 mg) in CDCl₃(1 mL)

t

components were removed, and the residue was washed with

was treated with Me₃SiCN (ca. 20 mg) and heated at 80 ЊC. The

t

pentane (2 × 5 mL) and dried in vacuo to give (Cp^Bu)₂Mo-

(OSiMe₃)(CN) as a purple solid (305 mg, 88%). Analysis calcd.

for C₂₂H₃₅NOSiMo: C, 58.3%; H, 7.8%; N, 3.1%. Found: C,

reaction was monitored by ¹H NMR spectroscopy, and the

t

formation of Cp^Bu₂Mo(NCS)(CN) was complete over 6 days.

3

¹H NMR (CDCl₃): 1.24 [s, C₅H₄{C(CH₃)₃}], 5.15 [q, J_H–H

=

57.5%; H, 6.8%; N, 2.9%. IR Data (KBr disk, cm^Ϫ1): 3039 (w),

2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.46 [q, J_H–H= 2.5, 1 H of

C₅H₄{C(CH₃)₃}], 5.50 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}],

3

᎐

2959 (s), 2906 (m), 2871 (m), 2105 (m) [ν(C᎐N)], 1482 (w), 1461

᎐

1746

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

View Article Online

t

3

5.75 [q, J_H–H= 2.5,

1

H

of C₅H₄{C(CH₃)₃}]. ¹³C{¹H}

Synthesis of (Cp^Bu)₂Mo(CN)Br

Bu^t

NMR (CDCl₃): 30.9 [C₅H₄{C(CH₃)₃}], 33.0 [C₅H₄{C(CH₃)₃}],

90.8 [1 C of C₅H₄{C(CH₃)₃}], 91.6 [1 C of C₅H₄{C(CH₃)₃}],

92.0 [1 C of C₅H₄{C(CH₃)₃}], 102.3 [1 C of C₅H₄{C(CH₃)₃}],

C of C₅H₄{C(CH₃)₃}], 134.7 [Mo-CN], 150.2

[Mo(NCS)].

A solution of (Cp )₂Mo(OSiMe₃)(CN) (200 mg, 0.44 mmol)

in toluene (20 mL) was stirred with Me₃SiBr (135 mg, 0.88

mmol) for 1 day at room temperature. After this period, the

mixture was cooled at 0 ЊC and ﬁltered. The precipitate was

130.2 [1

washed with toluene (2 × 5 mL) and pentane (2 × 5 mL)

t

and dried in vacuo to give (Cp^Bu)₂Mo(CN)Br as a brown solid

(180 mg, 92%). Analysis calcd. for C₁₉H₂₆BrNMo: C, 51.4%; H,

5.9%; N, 3.2%. Found: C, 50.2%; H, 5.4%; N, 2.9%. IR Data

Bu^t

Syntheses of (Cp )₂Mo(NCS)(SCN) and (Cp )₂Mo(NCS)₂

A solution of (Cp^Bu)₂MoO (200 mg, 0.56 mmol) in benzene

(15 mL) was treated with Me₃SiNCS (180 mg, 1.37 mmol) for

3 hours at room temperature. After this period, the mixture

was ﬁltered, and the precipitate was washed with toluene

t

(KBr disk, cm^Ϫ1): 3122 (m), 3091 (s), 2959 (vs), 2905 (s), 2870

᎐

(m), 2108 (s) [ν(C᎐N)], 1484 (s), 1463 (s), 1417 (m), 1397 (m),

᎐

1276 (s), 1196 (w), 1153 (m), 1078 (w), 1041 (m), 1025 (m), 968

(w), 907 (m), 889 (s), 844 (m), 813 (m), 733 (w), 697 (w), 666 (w),

631 (w), 602 (w), 534 (w), 513 (w), 480 (w), 438 (w), 415 (w). ¹H

NMR (CDCl₃): 1.21 [s, C₅H₄{C(CH₃)₃}], 5.34 [br s, 2 H of

C₅H₄{C(CH₃)₃}], 5.52 [br s, 1 H of C₅H₄{C(CH₃)₃}], 5.77

[br s, 1 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (CDCl₃): 31.2 [q,

¹J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.8 [s, C₅H₄{C(CH₃)₃}], 90.9 [d,

¹J_C–H= 184, 1 C of C₅H₄{C(CH₃)₃}], 95.3 [d, ¹J_C–H= 178, 1 C of

(2 × 5 mL) and pentane (2 × 5 mL) and dried in vacuo to give

t

(Cp^Bu)₂Mo(NCS)₂as a purple solid (90 mg, 35%). Analysis

calcd. for C₂₀H₂₆N₂S₂Mo: C, 52.9%; H, 5.8%; N, 6.2%. Found:

C, 52.2%; H, 5.2%; N, 6.0%. IR Data (KBr disk, cm^Ϫ1): 3127

(w), 3087 (m), 2963 (s), 2906 (m), 2875 (m), 2076 (vs) [ν(CN)],

1492 (m), 1460 (m), 1385 (m), 1365 (m), 1270 (m), 1189 (w),

1150 (m), 1049 (w), 1013 (w), 958 (w), 931 (w), 911 (w), 880

1

(w), 830 (m), 684 (w), 579 (w), 481 (w). H NMR (CDCl₃):

C₅H₄{C(CH₃)₃}], 96.9 [d, J_C–H= 185, 1 C of C₅H₄{C(CH₃)₃}],

101.5 [d, J_C–H= 178, 1 C of C₅H₄{C(CH₃)₃}], 120.2 [s, 1 C of

C₅H₄{C(CH₃)₃}], [not located, CN].

3

1

1.25 [s, C₅H₄{C(CH₃)₃}], 5.45 [t, J_H–H= 2.5, 2 H of C₅H₄{C-

(CH₃)₃}], 5.56 [t, ³J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR

1

(CDCl₃): 30.9 [q, J_C–H= 127, C₅H₄{C(CH₃)₃}], 33.5 [s,

C₅H₄{C(CH₃)₃}], 96.1 [d, J_C–H= 185, 2 C of C₅H₄{C(CH₃)₃}],

100.3 [d, J_C–H= 181, 2 C of C₅H₄{C(CH₃)₃}], 133.7 [s, 1 C of

C₅H₄{C(CH₃)₃}], 149.9 [s, Mo(NCS)]. The volatile components

were removed from the reaction ﬁltrate, and the residue

1

t

Synthesis of (Cp^Bu)₂Mo(CN)I

1

t

A solution of (Cp^Bu)₂Mo(OSiMe₃)CN (200 mg, 0.44 mmol) in

toluene (20 mL) was stirred with Me₃SiI (110 mg, 0.55 mmol)

for 1 day at room temperature. After this period, the mixture

was cooled at 0 ЊC and ﬁltered. The precipitate was washed with

obtained was washed with pentane (2 × 5 mL) and dried in

t

vacuo to give (Cp^Bu)₂Mo(NCS)(SCN) as a dark brown solid

(150 mg, 59%). Analysis calcd. for C₂₀H₂₆N₂S₂Mo: C, 52.9%; H,

5.8%; N, 6.2%. Found: C, 53.6%; H, 5.6%; N, 6.0%. IR Data

(KBr disk, cm^Ϫ1): 3086 (m), 2960 (s), 2904 (m), 2873 (m), 2072

(vs) [ν(CN)], 1488 (m), 1460 (m), 1389 (m), 1363 (m), 1269 (m),

1192 (w), 1150 (m), 1045 (w), 1017 (w), 928 (w), 912 (w), 843 (s),

694 (m), 684 (m), 594 (w), 485 (w), 432 (w), 408 (w). ¹H NMR

toluene (2 × 5 mL) and pentane (2 × 5 mL) and dried in vacuo

t

to give (Cp^Bu)₂Mo(CN)I as a brown solid (120 mg, 55%).

Analysis calcd. for C₁₉H₂₆INMo: C, 46.5%; H, 5.3%; N, 2.9%.

Found: C, 47.2%; H, 5.6%; N, 3.2%. IR Data (KBr disk, cm^Ϫ1):

᎐

3089 (vs), 2957 (vs), 2903 (vs), 2868 (s), 2106 (vs) [ν(C᎐N)], 1482

᎐

(s), 1462 (s), 1414 (s), 1367 (vs), 1274 (s), 1196 (m), 1152 (s),

1077 (m), 1041 (m), 965 (m), 888 (s), 842 (s), 812 (s), 734 (w),

666 (w), 598 (w), 475 (w), 441 (w), 414 (m). ¹H NMR (CDCl₃):

3

(CDCl₃): 1.28 [s, C₅H₄{C(CH₃)₃}], 5.01 [q, J_H–H= 2, 1 H of

C₅H₄{C(CH₃)₃}], 5.15 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}],

3

1.22 [s, C₅H₄{C(CH₃)₃}], 5.27 [q, J_H–H= 2.5, 1 H of C₅H₄-

5.79 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}], 5.92 [q, J_H–H= 2,

3

1 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (CDCl₃): 30.7 [q, ¹J_C–H= 127,

{C(CH₃)₃}], 5.50 [m, 2 H of C₅H₄{C(CH₃)₃}], 5.76 [q, J_H–H

=

2.5, 1 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (CDCl₃): 31.3 [q,

¹J_C–H= 127, C₅H₄{C(CH₃)₃}], 32.7 [s, C₅H₄{C(CH₃)₃}], 88.7 [d,

¹J_C–H= 185, 1 C of C₅H₄{C(CH₃)₃}], 94.0 [d, ¹J_C–H= 185, 1 C of

1

C₅H₄{C(CH₃)₃}], 33.5 [s, C₅H₄{C(CH₃)₃}], 87.9 [d, J_C–H

178, 1 C of C₅H₄{C(CH₃)₃}], 91.9 [d, J_C–H= 181, 1 C of

=

1

C₅H₄{C(CH₃)₃}], 97.2 [d, J_C–H= 185, 1 C of C₅H₄{C(CH₃)₃}],

1

C₅H₄{C(CH₃)₃}], 94.5 [d, J_C–H= 178, 1 C of C₅H₄{C(CH₃)₃}],

98.0 [d, J_C–H= 180, 1 C of C₅H₄{C(CH₃)₃}], 119.1 [s, 1 C of

C₅H₄{C(CH₃)₃}], 136.1 [s, CN].

109.7 [d, J_C–H= 181, 1 C of C₅H₄{C(CH₃)₃}], 124.6 [s,

1

Mo(SCN)], 135.5 [s, 1 C of C₅H₄{C(CH₃)₃}], 153.0 [s, Mo-

(NCS)].

t

Synthesis of (Cp^Bu)₂Mo(CN)Cl

Synthesis of (Cp^Bu)₂Mo(CN)(O₃SMe)

t

A solution of (Cp^Bu)₂Mo(OSiMe₃)(CN) (200 mg, 0.44 mmol)

in toluene (20 mL) was treated with Me₃SiCl (96 mg,

0.88 mmol) and stirred for 1 day at room temperature. After

this period, the mixture was cooled at 0 ЊC and ﬁltered. The

in toluene (20 mL) was stirred with Me₃SiO₃SMe (89 mg,

0.53 mmol) for 4 hours at room temperature. After this period,

the mixture was concentrated to 5 mL and ﬁltered at 0 ЊC.

precipitate was washed with pentane (2 × 5 mL) and dried

The precipitate was washed with pentane (2 × 5 mL) and dried

t

in vacuo to give (Cp^Bu)₂Mo(CN)Cl as a brown solid (150 mg,

85%). Analysis calcd. for C₁₉H₂₆ClNMo: C, 57.1%; H,

6.6%; N, 3.5%. Found: C, 56.8%; H, 6.8%; N, 3.5%. IR Data

in vacuo to give (Cp^Bu)₂Mo(CN)(O₃SMe) as a brown solid (150

mg, 74%). Analysis calcd. for C₂₀H₂₉NO₃SMo: C, 52.3%; H,

6.4%; N, 3.1%. Found: C, 51.5%; H, 6.3%; N, 3.1%. IR Data

(KBr disk, cm^Ϫ1): 3098 (s), 3071 (vs), 2959 (vs), 2909 (vs), 2871

(KBr disk, cm^Ϫ1): 3102 (s), 2958 (s), 2909 (m), 2874 (m), 2116 (s)

᎐

(vs), 2106 (vs) [ν(C᎐N)], 1487 (s), 1463 (s), 1394 (s), 1363

[ν(C᎐N)], 1489 (m), 1465 (m), 1392 (m), 1366 (m), 1328 (w),

᎐

(s), 1269 (s), 1205 (w), 1152 (m), 1077 (w), 1044 (m), 1024 (m),

972 (w), 933 (w), 908 (m), 842 (vs), 732 (w), 669 (w), 597 (w),

1273 (vs), 1198 (m), 1151 (vs), 1081 (m), 1011 (vs), 908 (w),

849 (m), 769 (m), 672 (w), 599 (w), 558 (m), 531 (m), 467 (w),

1

463 (w), 435 (w), 420 (w). H NMR (CDCl₃): 1.22 [s, C₅H₄-

423 (w). H NMR (CDCl₃): 1.23 [s, C₅H₄{C(CH₃)₃}], 2.70 [s,

3

{C(CH₃)₃}], 5.28 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.36

O₃SCH₃], 5.56 [q, ³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.59 [q,

[q, ³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.42 [q, ³J_H–H= 2.5, 1 H

³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 5.88 [q, ³J_H–H= 2.5, 1 H of

3

of C₅H₄{C(CH₃)₃}], 5.88 [q, J_H–H= 2.5, 1 H of C₅H₄-

C₅H₄{C(CH₃)₃}], 5.99 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}].

1

{C(CH₃)₃}]. ¹³C NMR (CDCl₃): 31.1 [q, J_C–H= 126, C₅H₄-

¹³C NMR (CDCl₃): 31.0 [q, J_C–H= 127, C₅H₄{C(CH₃)₃}],

1

{C(CH₃)₃}], 32.9 [s, C₅H₄{C(CH₃)₃}], 91.5 [d, J_C–H= 185, 1 C

33.2 [s, C₅H₄{C(CH₃)₃}], 40.0 [q, ¹J_C–H= 137, O₃SCH₃], 91.5 [d,

¹J_C–H= 185, 1 C of C₅H₄{C(CH₃)₃}], 98.2 [d, ¹J_C–H= 182, 1 C of

1

of C₅H₄{C(CH₃)₃}], 94.7 [d, J_C–H= 183, 1 C of C₅H₄-

{C(CH₃)₃}], 97.2 [d, ¹J_C–H= 191, 1 C of C₅H₄{C(CH₃)₃}], 103.2

C₅H₄{C(CH₃)₃}], 98.7 [d, J_C–H= 182, 1 C of C₅H₄{C(CH₃)₃}],

1

[d, J_C–H= 178, 1 C of C₅H₄{C(CH₃)₃}], 122.3 [s, 1 C of

99.6 [d, J_C–H= 185, 1 C of C₅H₄{C(CH₃)₃}], 127.8 [s, 1 C of

C₅H₄{C(CH₃)₃}], 137.9 [s, CN].

C₅H₄{C(CH₃)₃}], 137.7 [s, CN].

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

1747

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t

1

Synthesis of (Cp^Bu)₂Mo(ꢀ²-S₂)

87.2 [d, J_C–H= 176, 2 C of C₅H₄{C(CH₃)₃}], 108.1 [s, 1 C of

C₅H₄{C(CH₃)₃}]. ¹²⁵Te NMR (C₆D₆): Ϫ803 [s].

Bu^t

A mixture of (Cp )₂MoH₂(300 mg, 0.88 mmol) and sulfur

(85 mg, 2.65 mmol of “S”) in toluene (20 mL) was stirred at

room temperature for 1 hour. The volatile components were

t

Chalcogen exchange between (Cp^Bu)₂Mo(ꢀ²-Se₂) and (Cp^Bu)₂-

Mo(ꢀ²-Te₂)

removed and the residue was washed with pentane (2 × 5 mL)

t

and dried in vacuo to give (Cp^Bu)₂Mo(η²-S₂) as an orange solid

(310 mg, 87%). Analysis calcd. for C₁₈H₂₆S₂Mo: C, 53.7%; H,

6.5%. Found: C, 53.5%; H, 6.5%. MS: m/z = 404 (M^ϩ). IR Data

(KBr disk, cm^Ϫ1): 3077 (s), 2956 (vs), 2865 (s), 1459 (s), 1390 (s),

1361 (s), 1267 (s), 1199 (w), 1150 (m), 1037 (m), 896 (s), 823 (s),

A mixture of (Cp^Bu)₂Mo(η²-Se₂) (ca. 30 mg) and (Cp^Bu)₂-

Mo(η²-Te₂) (ca. 30 mg) in C₆D₆(1 mL) was heated at 80 ЊC.

1

The sample was monitored by H NMR spectroscopy, which

t

demonstrated that (Cp^Bu)₂Mo{η²-(SeTe)} was formed as the

1

major product over a period of 1 day. H NMR (C₆D₆): 0.94

1

[s, C₅H₄{C(CH₃)₃}], 4.16 [q, ³J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}],

663 (w), 582 (w), 533 (m), 466 (w). H NMR (C₆D₆): 1.08 [s,

3

C₅H₄{C(CH₃)₃}], 3.95 [t, J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}],

4.60 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}], 4.66 [q, J_H–H= 2,

3

4.85 [t, J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (C₆D₆):

3

1 H of C₅H₄{C(CH₃)₃}], 5.32 [q, J_H–H= 2, 1 H of C₅H₄{C-

32.2 [q, ¹J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.3 [s, C₅H₄{C(CH₃)₃}],

(CH₃)₃}]. ⁷⁷Se NMR (C₆D₆): Ϫ430 [s, ¹J_Se–Te= 522]. ¹²⁵Te NMR

(C₆D₆): Ϫ459 [s, ¹J_Te–Senot observed].

1

88.8 [d, J_C–H= 176, 2 C of C₅H₄{C(CH₃)₃}], 93.0 [d, J_C–H

=

180, 2 C of C₅H₄{C(CH₃)₃}], 113.9 [s, 1 C of C₅H₄{C(CH₃)₃}].

t

Reactions of (Cp^Bu)₂Mo(CO) with the elemental chalcogens

t

Synthesis of (Cp^Bu)₂Mo(ꢀ²-Se₂)

t

A solution of (Cp^Bu)₂Mo(CO) (ca. 10 mg) in C₆D₆(1 mL)

t

was treated with elemental chalcogen (excess). ¹H NMR

A mixture of (Cp^Bu)₂MoH₂(220 mg, 0.65 mmol) and selenium

powder (170 mg, 2.15 mmol of “Se”) in toluene (20 mL) was

stirred at 120 ЊC for 1 hour. The mixture was ﬁltered, and the

volatile components were removed from the ﬁltrate. The residue

t

spectroscopy was used to monitor the formation of (Cp^Bu)₂-

Mo(η²-E₂) (E = S, 1 hour at room temperature; E = Se, 5 hours

at 80 ЊC; E = Te, 1 day at 120 ЊC).

was washed with pentane (2 × 5 mL) and dried in vacuo to give

t

(Cp^Bu)₂Mo(η²-Se₂) as a brown solid (270 mg, 84%). Analysis

calcd. for C₁₈H₂₆Se₂Mo: C, 43.6%; H, 5.3%. Found: C, 42.8%;

H, 5.4%. MS: m/z = 497 (M^ϩϪ 1). IR Data (KBr disk, cm^Ϫ1):

3075 (s), 2957 (vs), 2899 (s), 2863 (s), 1478 (m), 1458 (s), 1390

(s), 1360 (s), 1267 (s), 1200 (w), 1149 (m), 1038 (m), 937 (w),

Synthesis of [(Cp^Bu)₂Mo(ꢁ-S)]₂

t

A solution of (Cp^Bu)₂Mo(η²-S₂) (ca. 10 mg) in C₆D₆(1 mL)

was treated with PMe₃. The sample was monitored by ¹H

NMR spectroscopy, which demonstrated that the formation

t

of [(Cp^Bu)₂Mo(µ-S)]₂was complete after 1 day at room tem-

1

896 (s), 828 (vs), 660 (w), 575 (w), 457 (w), 412 (w). H NMR

1

perature, accompanied by the formation of Me₃PS. H NMR

(C₆D₆): 1.24 [s, C₅H₄{C(CH₃)₃}], 3.34 [m, 2 H of C₅H₄-

{C(CH₃)₃}], 4.15 [br s, 2 H of C₅H₄{C(CH₃)₃}].

3

(C₆D₆): 1.00 [s, C₅H₄{C(CH₃)₃}], 4.14 [t, J_H–H= 2, 2 H of

C₅H₄{C(CH₃)₃}], 4.93 [t, ³J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}]. ¹³

C

1

NMR (C₆D₆): 32.2 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.3 [s,

1

C₅H₄{C(CH₃)₃}], 87.7 [d, J_C–H= 181, 2 C of C₅H₄{C(CH₃)₃}],

t

1

Synthesis of [(Cp^Bu)₂Mo(ꢁ-Se)]₂

91.4 [d, J_C–H= 178, 2 C of C₅H₄{C(CH₃)₃}], 111.0 [s, 1 C of

t

C₅H₄{C(CH₃)₃}]. ⁷⁷Se NMR (C₆D₆): Ϫ254 [s].

A solution of (Cp^Bu)₂Mo(η²-Se₂) (300 mg, 0.60 mmol) in

toluene (20 mL) was treated with PMe₃(0.5 mL) for 6 hours at

room temperature. After this period, the volatile components

were removed in vacuo and the residue obtained was extracted

into pentane (50 mL). The ﬁltrate was concentrated to ca. 3 mL

and placed at Ϫ78 ЊC, thereby depositing a red–brown solid

that was isolated by ﬁltration. The Me₃PSe by-product was

t

Synthesis of (Cp^Bu)₂Mo(ꢀ²-Te₂)

t

A mixture of (Cp^Bu)₂MoH₂(335 mg, 0.98 mmol) and tellurium

powder (390 mg, 3.06 mmol of “Te”) in toluene (20 mL) was

treated with PMe₃(0.5 mL) at Ϫ78 ЊC. The mixture was

warmed to room temperature and heated at 80 ЊC for 1 day.

After this period, the mixture was ﬁltered and the volatile

components were removed from the ﬁltrate. The residue was

dissolved in toluene (20 mL) and stirred with Hg (1 mL) for

1.5 hours at room temperature to convert PMe₃PTe to HgTe,

removed by vacuum sublimation at 50 ЊC, giving pure red–

t

brown [(Cp^Bu)₂Mo(µ-Se)]₂(170 mg, 60%). Analysis calcd. for

C₃₆H₅₂Se₂Mo₂: C, 51.8%; H, 6.3%. Found: C, 51.8%; H, 5.8%.

MS: m/z = 835 (M^ϩϪ 1). IR Data (KBr disk, cm^Ϫ1): 3123 (w),

2956 (vs), 2899 (vs), 2864 (s), 1480 (s), 1458 (s), 1391 (m), 1360

(s), 1273 (s), 1195 (w), 1150 (m), 1041 (m), 917 (m), 871 (m),

which was removed by ﬁltration. The volatile components were

t

removed from the ﬁltrate, giving a mixture of (Cp^Bu)₂Mo(η²-

1

821 (vs), 783 (vs), 655 (w), 587 (w), 459 (w). H NMR (C₆D₆):

t

Te₂) and [(Cp^Bu)₂Mo(µ-Te)]₂(due to tellurium abstraction by

PMe₃). The residue was extracted into toluene and tellurium

powder was added to the extracted ﬁltrate, and the mixture

was allowed to stir for 2.5 hours at 120 ЊC to convert

1.05 [s, C₅H₄{C(CH₃)₃}], 4.80 [br s, 2 H of C₅H₄{C(CH₃)₃}],

5.68 [br s, 2 H of C₅H₄{C(CH₃)₃}]. ¹³C NMR (C₆D₆): 31.8 [q,

¹J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.7 [s, C₅H₄{C(CH₃)₃}], 91.4

1

[d, J_C–H= 176, 2 C of C₅H₄{C(CH₃)₃}], 95.8 [d, J_C–H= 175,

2 C of C₅H₄{C(CH₃)₃}], 110.1 [s, 1 C of C₅H₄{C(CH₃)₃}]. ⁷⁷Se

NMR (C₆D₆): Ϫ996 [s].

t

[(Cp^Bu)₂Mo(µ-Te)]₂to (Cp^Bu)₂Mo(η²-Te₂). After this period,

the mixture was ﬁltered, and the volatile components were

removed from the ﬁltrate. The residue was extracted into tolu-

ene again and the volatile components were removed. The

extraction was repeated until no tellurium powder was observed

t

Synthesis of [(Cp^Bu)₂Mo(ꢁ-Te)]₂

t

from the residue. The ﬁnal residue was washed with pentane

A mixture of (Cp^Bu)₂Mo(η²-Te₂) (390 mg, 0.66 mmol) and Hg

t

(2 × 5 mL) and dried in vacuo to give (Cp^Bu)₂Mo(η²-Te₂) as a

dark-brown solid (390 mg, 67%). Analysis calcd. for C₁₈H₂₆-

Te₂Mo: C, 36.4%; H, 4.4%. Found: C, 37.0%; H, 4.7%. MS:

m/z = 593 (M^ϩϪ 1). IR Data (KBr disk, cm^Ϫ1): 3108 (m), 3071

(w), 2953 (vs), 2899 (s), 2862 (s), 1477 (s), 1458 (s), 1361 (vs),

1269 (s), 1196 (w), 1148 (m), 1025 (m), 937 (m), 907 (m), 889 (s),

836 (vs), 796 (s), 729 (w), 659 (m), 591 (w), 466 (w), 405 (w). ¹H

NMR (C₆D₆): 0.86 [s, C₅H₄{C(CH₃)₃}], 4.62 [t, ³J_H–H= 2, 2 H of

(2 mL) in benzene (20 mL) was treated with PMe₃(0.5 mL) and

stirred for 1 day at room temperature. The mixture was ﬁltered

after this period, and the volatile components were removed

slowly from the ﬁltrate. The residue was dried in vacuo to give

t

[(Cp^Bu)₂Mo(µ-Te)]₂as a brown solid (290 mg, 95%). IR Data

(KBr disk, cm^Ϫ1): 3074 (w), 2957 (vs), 2901 (s), 2865 (s), 1480

(s), 1460 (s), 1394 (m), 1362 (s), 1271 (s), 1195 (w), 1149 (m),

1039 (m), 914 (m), 874 (s), 825 (s), 788 (s), 658 (w), 588 (w), 473

(w), 409 (w). ¹H NMR (C₆D₆): 1.04 [s, C₅H₄{C(CH₃)₃}], 4.87 [br

s, 2 H of C₅H₄{C(CH₃)₃}], 5.69 [br s, 2 H of C₅H₄{C(CH₃)₃}].

¹³C NMR (C₆D₆): 31.8 [q, ¹J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.5 [s,

C₅H₄{C(CH₃)₃}], 5.06 [t, ³J_H–H= 2, 2 H of C₅H₄{C(CH₃)₃}]. ¹³

C

1

NMR (C₆D₆): 31.8 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.0 [s,

1

C₅H₄{C(CH₃)₃}], 83.7 [d, J_C–H= 181, 2 C of C₅H₄{C(CH₃)₃}],

1748

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

View Article Online

1

C₅H₄{C(CH₃)₃}], 85.2 [d, J_C–H= 180, 2 C of C₅H₄{C(CH₃)₃}],

(SePh)H as a red–brown solid (200 mg, 46%). Analysis calcd.

1

89.9 [d, J_C–H= 176, 2 C of C₅H₄{C(CH₃)₃}], 108.7 [s, 1 C of

for C₂₄H₃₂SeMo: C, 58.2%; H, 6.5%. Found: C, 58.9%; H, 5.9%.

MS: m/z = 495 (M^ϩϪ H). IR Data (KBr disk, cm^Ϫ1): 3113 (m),

3062 (m), 2959 (vs), 2900 (s), 2864 (s), 1882 (w) [ν(Mo–H)],

1571 (s), 1484 (s), 1459 (s), 1430 (s), 1390 (s), 1359 (vs), 1270 (s),

1194 (m), 1149 (m), 1063 (m), 1019 (s), 909 (m), 879 (s), 838 (s),

C₅H₄{C(CH₃)₃}]. ¹²⁵Te NMR (C₆D₆): Ϫ1664 [s].

t

Reaction of [(Cp^Bu)₂Mo(ꢁ-Te)]₂with Te

A mixture of [(Cp^Bu)₂Mo(µ-Te)]₂(ca. 10 mg) and tellurium

t

1

779 (vs), 738 (vs), 694 (vs), 664 (s), 473 (s). H NMR (C₆D₆):

powder (ca. 5 mg) in C₆D₆(1 mL) was heated at 120 ЊC.

Ϫ7.83 [s, ²J_Se–H= 15, Mo–H], 1.19 [s, C₅H₄{C(CH₃)₃}], 3.66 [br

s, 1 H of C₅H₄{C(CH₃)₃}], 3.89 [br s, 1 H of C₅H₄{C(CH₃)₃}],

4.69 [br s, 1 H of C₅H₄{C(CH₃)₃}], 4.91 [br s, 1 H of C₅H₄-

1

The sample was monitored by H NMR spectroscopy, which

Bu^t

demonstrated that the formation of (Cp )₂Mo(η²-Te₂) was

complete after 5 hours.

3

{C(CH₃)₃}], 7.07 [m, 3 H of SeC₆H₅], 7.87 [d, J_H–H= 8, 2 H

of SeC₆H₅]. ¹³C NMR (C₆D₆): 31.7 [s, C₅H₄{C(CH₃)₃}], 32.2

Bu^t

Reaction of [(Cp )₂Mo(ꢁ-Te)]₂with Se

A mixture of [(Cp^Bu)₂Mo(µ-Te)]₂(ca. 10 mg) and selenium

1

[q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 76.7 [d, J_C–H= 177, 1 C of

t

1

C₅H₄{C(CH₃)₃}], 79.0 [d, J_C–H= 184, 1 C of C₅H₄{C(CH₃)₃}],

1

powder (ca. 5 mg) in C₆D₆(1 mL) was heated at 80 ЊC.

81.8 [d, J_C–H= 177,

1

C

of C₅H₄{C(CH₃)₃}], 98.8 [d,

1

The sample was monitored by H NMR spectroscopy, which

¹J_C–H= 178, 1 C of C₅H₄{C(CH₃)₃}], 123.1 [s, 1 C of C₅H₄-

1 2

t

demonstrated that a mixture of (Cp^Bu)₂Mo(η²-Te₂), (Cp^Bu)₂-

{C(CH₃)₃}], 123.2 [dt, J_C–H= 159, J_C–H= 8, 1 C of SeC₆H₅],

1 2

t

Mo(η²-Se₂) and (Cp^Bu)₂Mo(η²-SeTe) was obtained after 1 hour,

127.7 [dd, J_C–H= 157, J_C–H= 8, 2 C of SeC₆H₅], 134.8 [dt,

¹J_C–H= 158, ²J_C–H= 7, 2 C of SeC₆H₅], 140.5 [s, 1 C of SeC₆H₅].

⁷⁷Se NMR (C₆D₆): Ϫ117 [d, ²J_Se–H= 15].

t

then the formation of (Cp^Bu)₂Mo(η²-Se₂) was complete within

24 hours.

t

Reaction of [(Cp^Bu)₂Mo(ꢁ-Se)]₂with Se

Synthesis of (Cp^Bu)₂Mo(TePh)H

t

A mixture of [(Cp^Bu)₂Mo(µ-Se)]₂(ca. 10 mg) and selenium

A mixture of (Cp^Bu)₂MoH₂(300 mg, 0.88 mmol) and Ph₂Te₂

powder (ca. 5 mg) in C₆D₆(1 mL) was heated at 80 ЊC.

(343 mg, 0.84 mmol) in toluene (15 mL) was stirred for 24 hours

at room temperature. After this period, the volatile components

1

The sample was monitored by H NMR spectroscopy, which

t

demonstrated that the formation of (Cp^Bu)₂Mo(η²-Se₂) was

were removed in vacuo, and the residue obtained was washed

t

complete within 5 hours.

with cold pentane (2 × 5 mL) and dried to give (Cp^Bu)₂Mo-

(TePh)H as a brown solid (390 mg, 81%). Analysis calcd. for

C₂₄H₃₂TeMo: C, 53.0%; H, 5.9%. Found: C, 51.7%; H, 6.2%. IR

Data (KBr disk, cm^Ϫ1): 3106 (m), 3057 (s), 2955 (vs), 2899 (s),

2862 (s), 1869 (w) [ν(Mo–H)], 1567 (m), 1483 (s), 1461 (s), 1429

(m), 1387 (s), 1359 (s), 1269 (s), 1194 (w), 1148 (m), 1039 (m),

1016 (s), 916 (m), 880 (m), 838 (s), 783 (s), 731 (s), 694 (s), 658

t

Reaction of [(Cp^Bu)₂Mo(ꢁ-Se)]₂with Te

t

A mixture of [(Cp^Bu)₂Mo(µ-Se)]₂(ca. 10 mg) and tellurium

powder (ca. 5 mg) in C₆D₆(1 mL) was heated at 80 ЊC. The

sample was monitored by ¹H NMR spectroscopy, which

t

demonstrated that a mixture of (Cp^Bu)₂Mo(η²-Te₂), (Cp^Bu)₂-

1

2

Bu^t

(m), 458 (m), 408 (w). H NMR (C₆D₆): Ϫ8.25 [s, J_Te–H= 39,

Mo(η²-Se₂) and (Cp )₂Mo(η²-SeTe) was obtained after 1 day;

3

Mo–H], 1.11 [s, C₅H₄{C(CH₃)₃}], 3.83 [q, J_H–H= 2, 1 H of

the mixture persisted even after 3 days at 80 ЊC.

3

C₅H₄{C(CH₃)₃}], 3.89 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}],

3

Bu^t

4.82 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}], 4.88 [q, J_H–H= 2,

1 H of C₅H₄{C(CH₃)₃}], 6.98 [t, ³J_H–H= 7, 2 H of TeC₆H₅], 7.09

[t, ³J_H–H= 7, 1 H of TeC₆H₅], 8.04 [d, ³J_H–H= 8, 2 H of TeC₆H₅].

¹³C NMR (C₆D₆): 31.4 [s, C₅H₄{C(CH₃)₃}], 32.2 [q, ¹J_C–H= 126,

Synthesis of (Cp )₂Mo(SPh)H

t

A mixture of (Cp^Bu)₂MoH₂(400 mg, 1.18 mmol) and Ph₂S₂

(256 mg, 1.18 mmol) in toluene (10 mL) was stirred for 1 day at

80 ЊC. After this period, the volatile components were removed

in vacuo, and the residue obtained was washed with cold

1

C₅H₄{C(CH₃)₃}], 76.8 [d, J_C–H= 183, 1 C of C₅H₄{C(CH₃)₃}],

1

77.6 [d, J_C–H= 181,

1

C

of C₅H₄{C(CH₃)₃}], 80.9 [d,

t

pentane (2 × 5 mL) and dried to give (Cp^Bu)₂Mo(SPh)H as

an orange–brown solid (440 mg, 83%). Analysis calcd. for

C₂₄H₃₂SMo: C, 64.3%; H, 7.2%. Found: C, 64.1%; H, 7.1%. IR

Data (KBr disk, cm^Ϫ1): 3127 (w), 3076 (vs), 2957 (vs), 2899 (s),

2863 (s), 1896 (w) [ν(Mo–H)], 1574 (s), 1456 (s), 1393 (m), 1358

(vs), 1272 (s), 1195 (m), 1148 (m), 1076 (m), 1019 (s), 914 (m),

898 (m), 842 (m), 804 (m), 776 (s), 736 (vs), 691 (vs), 595 (w),

¹J_C–H= 176, 1 C of C₅H₄{C(CH₃)₃}], 92.0 [d, J_C–H= 179, 1 C

1

of C₅H₄{C(CH₃)₃}], 111.5 [s, 1 C of TeC₆H₅], 121.8 [s, 1 C

1

2

of C₅H₄{C(CH₃)₃}], 124.9 [dt, J_C–H= 159, J_C–H= 7, 1 C of

TeC₆H₅], 127.8 [dd, ¹J_C–H= 157, ²J_C–H= 8, 2 C of TeC₆H₅], 139.9

1

2

[dt, J_C–H= 160, J_C–H= 7, 2 C of TeC₆H₅]. ¹²⁵Te NMR (C₆D₆):

Ϫ213 [d, ²J_Te–H= 39].

t

1

486 (m), 407 (w). H NMR (C₆D₆): Ϫ7.52 [s, Mo–H], 1.21 [s,

Synthesis of (Cp^Bu)₂Mo(SPh)₂

3

Bu^t

C₅H₄{C(CH₃)₃}], 3.62 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}],

Method A: from (Cp )₂Mo(SPh)H. A mixture of (Cp )₂-

Mo(SPh)H (95 mg, 0.21 mmol) and Ph₂S₂(50 mg, 0.23 mmol)

in toluene (15 mL) was stirred for 2 days at 80 ЊC. After this

period, the volatile components were removed, and the residue

was washed with cold pentane (2 × 5 mL) and dried in vacuo to

3

3.90 [q, J_H–H= 2, 1 H of C₅H₄{C(CH₃)₃}], 4.53 [q, J_H–H= 2,

3

1 H of C₅H₄{C(CH₃)₃}], 4.97 [q, J_H–H= 2, 1 H of C₅H₄{C-

(CH₃)₃}], 6.99 [t, ³J_H–H= 7, 1 H of SC₆H₅], 7.18 [t, ³J_H–H= 7, 2 H

of SC₆H₅], 7.74 [d, ³J_H–H= 8, 2 H of SC₆H₅]. ¹³C NMR (C₆D₆):

31.8 [s, C₅H₄{C(CH₃)₃}], 32.2 [q, ¹J_C–H= 126, C₅H₄{C(CH₃)₃}],

Bu^t

give (Cp )₂Mo(SPh)₂as a red solid (90 mg, 76%).

1

77.0 [d, J_C–H= 176,

1 C of C₅H₄{C(CH₃)₃}], 80.3 [d,

¹J_C–H= 181, 1 C of C₅H₄{C(CH₃)₃}], 82.2 [d, ¹J_C–H= 176, 1 C of

Bu^t

Method B: from (Cp )₂Mo(CO). A mixture of (Cp )₂-

Mo(CO) (150 mg, 0.41 mmol) and Ph₂S₂(90 mg, 0.41 mmol) in

toluene (10 mL) was stirred for 2 hours at room temperature.

After this period, the volatile components were removed from

C₅H₄{C(CH₃)₃}], 101.3 [d, ¹J_C–H= 177, 1 C of C₅H₄{C(CH₃)₃}],

1

121.7 [d, J_C–H= 160, 1 C of SC₆H₅], 123.5 [s, 1 C of

C₅H₄{C(CH₃)₃}], 127.5 [d, ¹J_C–H= 163, 2 C of SC₆H₅], 132.6 [d,

¹J_C–H= 158, 2 C of SC₆H₅], 152.3 [s, 1 C of SC₆H₅].

the mixture, and the residue was washed with pentane (3 ×

t

5 mL) and dried in vacuo to give (Cp^Bu)₂Mo(SPh)₂as a red solid

(140 mg, 61%). Analysis calcd. for C₃₀H₃₆S₂Mo: C, 64.7%; H,

6.5%. Found: C, 64.5%; H, 6.2%. IR Data (KBr disk, cm^Ϫ1):

3097 (vs), 3065 (s), 2956 (vs), 2902 (s), 2868 (s), 1574 (vs), 1486

(s), 1459 (vs), 1431 (s), 1391 (s), 1358 (vs), 1269 (s), 1190 (w),

1150 (m), 1078 (s), 1048 (s), 1022 (s), 958 (w), 927 (w), 908 (s),

846 (s), 826 (m), 803 (s), 740 (vs), 696 (vs), 676 (m), 488 (m),

Bu^t

Synthesis of (Cp )₂Mo(SePh)H

t

A mixture of (Cp^Bu)₂MoH₂(300 mg, 0.88 mmol) and Ph₂Se₂

(275 mg, 0.88 mmol) in toluene (10 mL) was stirred for 2 hours

at room temperature. After this period, the volatile components

were removed in vacuo, and the residue obtained was washed

t

with cold pentane (2 × 5 mL) and dried to give (Cp^Bu)₂Mo-

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

1749

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1

403 (w). H NMR (C₆D₆): 0.92 [s, C₅H₄{C(CH₃)₃}], 4.89 [t,

(ca. 10 mg) in C₆D₆(1 mL) was heated at 120 ЊC. The sample

³J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}], 5.05 [t, J_H–H= 2.5, 2 H

was monitored by ¹H NMR spectroscopy, which demonstrated

that no reaction had occurred after a period of 4 days.

3

of C₅H₄{C(CH₃)₃}], 6.99 [t, J_H–H= 7, 1 H of SC₆H₅], 7.09 [t,

³J_H–H= 7, 2 H of SC₆H₅], 7.62 [d, J_H–H= 7, 2 H of SC₆H₅].

3

t

¹³C NMR (C₆D₆): 31.0 [q, ¹J_C–H= 126, C₅H₄{C(CH₃)₃}], 33.8 [s,

Reactions of (Cp^Bu)₂Mo(EPh)₂(E

؍

S, Se, Te) with MeI

1

C₅H₄{C(CH₃)₃}], 94.5 [d, J_C–H= 182, 2 C of C₅H₄{C(CH₃)₃}],

t

1

A solution of (Cp^Bu)₂Mo(EPh)₂(E = S, Se, Te) (ca. 10 mg) in

98.5 [d, J_C–H= 177, 2 C of C₅H₄{C(CH₃)₃}], 124.1 [d,

¹J_C–H= 159, 1 C of SC₆H₅], 124.7 [s, 1 C of C₅H₄{C(CH₃)₃}],

C₆D₆(1 mL) was treated with excess MeI at room temperature.

1

¹H NMR spectroscopy was used to monitor the formation of

127.7 [d, J_C–H= 157, 2 C of SC₆H₅], 135.3 [d, J_C–H= 157, 2 C

of SC₆H₅], 148.9 [s, 1 C of SC₆H₅].

t

(Cp^Bu)₂MoI₂(E = S, 1 day; E = Se, 2 hours; E = Te, 0.5 hours).

t

Synthesis of [(Cp^Bu)₂Mo(PhSMe)H]I

t

Synthesis of (Cp^Bu)₂Mo(SePh)₂

t

A solution of (Cp^Bu)₂Mo(SPh)H (100 mg, 0.22 mmol) in C₆H₆

(10 mL) was treated with excess MeI (625 mg, 4.40 mmol) for

1 hour at room temperature, resulting in the formation of a

brown precipitate. The mixture was ﬁltered, and the precipitate

t

Method A: from (Cp^Bu)₂MoH₂. A mixture of (Cp^Bu)₂MoH₂

(300 mg, 0.88 mmol) and Ph₂Se₂(605 mg, 1.94 mmol) in toluene

(20 mL) was stirred for 6 days at 120 ЊC. After this period,

the volatile components were removed, and the oily residue was

was washed with toluene (2 × 5 mL) and pentane (2 × 5 mL)

washed with pentane (2 × 5 mL) and dried in vacuo to give

t

and dried in vacuo to give [(Cp^Bu)₂Mo(η²-1-PhSMe)H]I as a

brown solid (90 mg, 68%). Analysis calcd. for C₂₅H₃₅ISMo:

C, 50.9%; H, 6.0%. Found: C, 50.4%; H, 5.5%. IR Data (KBr

disk, cm^Ϫ1): 3057 (vs), 2964 (vs), 2870 (s), 1898 (w) [ν(Mo–H)],

1579 (w), 1485 (s), 1382 (s), 1271 (m), 1149 (m), 1080 (m), 1021

(m), 968 (m), 908 (m), 843 (m), 794 (s), 751 (s), 689 (m), 483 (w),

t

(Cp^Bu)₂Mo(SePh)₂as an olive-green solid (340 mg, 59%).

t

Method B: from (Cp^Bu)₂Mo(CO). A mixture of (Cp^Bu)₂-

Mo(CO) (200 mg, 0.55 mmol) and Ph₂Se₂(171 mg, 0.55 mmol)

in toluene (10 mL) was stirred for 1 hour at room temperature.

After this period, the volatile components were removed, and

1

426 (w). H NMR (CDCl₃): Ϫ8.80 [s, Mo–H], 1.18 [s, C₅H₄-

{C(CH₃)₃}], 2.81 [s, CH₃SC₆H₅], 4.44 [q, J_H–H= 2.5, 1 H of

C₅H₄{C(CH₃)₃}], 4.52 [q, J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}],

the residue obtained was washed with pentane (3 × 5 mL) and

3

t

dried in vacuo to give (Cp^Bu)₂Mo(SePh)₂as an olive-green solid

(230 mg, 65%). Analysis calcd. for C₃₀H₃₆Se₂Mo: C, 55.4%;

H, 5.6%. Found: C, 55.3%; H, 5.6%. IR Data (KBr disk, cm^Ϫ1):

3087 (m), 3054 (m), 2961 (vs), 2902 (s), 2868 (s), 1573 (s), 1470

(vs), 1432 (s), 1395 (m), 1359 (s), 1295 (w), 1271 (s), 1190 (w),

1150 (s), 1065 (m), 1021 (s), 998 (w), 924 (m), 905 (m), 850 (s),

3

5.30 [q, J_H–H= 2.5,

1 H of C₅H₄{C(CH₃)₃}], 5.79 [q,

³J_H–H= 2.5, 1 H of C₅H₄{C(CH₃)₃}], 7.30 [t, J_H–H= 7, 1 H

3

of CH₃SC₆H₅], 7.33 [d, J_H–H= 7, 2 H of CH₃SC₆H₅], 7.42 [t,

³J_H–H= 8, 2 H of CH₃SC₆H₅]. ¹³C NMR (CDCl₃): 29.6 [q,

¹J_C–H= 142, CH₃SC₆H₅], 31.9 [q, ¹J_C–H= 127, C₅H₄{C(CH₃)₃}],

1

810 (s), 738 (vs), 694 (vs), 664 (s), 472 (s), 408 (m). H NMR

(C₆D₆): 0.77 [s, C₅H₄{C(CH₃)₃}], 4.76 [t, J_H–H= 2.5, 2 H of

1

32.0 [s, C₅H₄{C(CH₃)₃}], 79.5 [d, J_C–H= 178, 1 C of C₅H₄-

3

1

{C(CH₃)₃}], 79.7 [d, J_C–H= 187, 1 C of C₅H₄{C(CH₃)₃}], 89.4

3

C₅H₄{C(CH₃)₃}], 5.20 [t, J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}],

[d, ¹J_C–H= 183, 1 C of C₅H₄{C(CH₃)₃}], 94.7 [d, ¹J_C–H= 180, 1 C

7.02 [m, 3 H of SeC₆H₅], 7.82 [m, 2 H of SeC₆H₅]. ¹³C NMR

1

2

of C₅H₄{C(CH₃)₃}], 127.1 [dt, J_C–H= 160, J_C–H= 7, 2 C of

CH₃SC₆H₅], 128.7 [dt, J_C–H= 163, J_C–H= 7, 1 C of CH₃-

SC₆H₅], 129.7 [dd, J_C–H= 164, J_C–H= 8, 2 C of CH₃SC₆H₅],

133.2 [s, 1 C of C₅H₄{C(CH₃)₃}], 138.3 [t, J_C–H= 9, 1 C of

1

(C₆D₆): 31.2 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 33.2 [s, C₅H₄-

1

2

1

{C(CH₃)₃}], 93.4 [d, J_C–H= 183, 2 C of C₅H₄{C(CH₃)₃}], 96.7

1

2

1

[d, J_C–H= 177, 2 C of C₅H₄{C(CH₃)₃}], 119.3 [s, 1 C of

2

C₅H₄{C(CH₃)₃}], 125.8 [dt, ¹J_C–H= 159, ²J_C–H= 7, 1 C of SeC₆-

CH₃SC₆H₅].

1

2

H₅], 127.9 [dt, J_C–H= 154, J_C–H= 7, 2 C of SeC₆H₅], 137.5 [t,

²J_C–H= 7, 1 C of SeC₆H₅], 138.0 [dt, J_C–H= 160, J_C–H= 7, 2 C

1

2

t

Synthesis of [(Cp^Bu)₂Mo(PhSeMe)H]I

of SeC₆H₅]. ⁷⁷Se NMR (C₆D₆): Ϫ83 [s].

t

A solution of (Cp^Bu)₂Mo(SePh)H (115 mg, 0.23 mmol) in

C₆H₆(10 mL) was treated with excess MeI (330 mg, 2.32

mmol) for 1 hour at room temperature, resulting in the for-

mation of a brown precipitate. The mixture was ﬁltered, and the

t

Synthesis of (Cp^Bu)₂Mo(TePh)₂

t

A mixture of (Cp^Bu)₂Mo(CO) (100 mg, 0.27 mmol) and Ph₂Te₂

(112 mg, 0.27 mmol) in toluene (15 mL) was stirred for 1 hour

at room temperature. After this period, the volatile components

precipitate was washed with toluene (2 × 5 mL) and pentane

t

(2 × 5 mL) and dried in vacuo to give [(Cp^Bu)₂Mo(PhSeMe)H]I

were removed and the residue obtained was washed with

t

as

a brown solid (135 mg, 91%). Analysis calcd. for

pentane (2 × 5 mL) and dried in vacuo to give (Cp^Bu)₂Mo-

(TePh)₂as a brown solid (140 mg, 69%). Analysis calcd. for

C₃₀H₃₆Te₂Mo: C, 48.2%; H, 4.9%. Found: C, 48.2%; H, 5.0%.

IR Data (KBr disk, cm^Ϫ1): 3056 (s), 2958 (vs), 2901 (s), 2866 (s),

1567 (m), 1464 (vs), 1428 (s), 1389 (m), 1362 (s), 1295 (m), 1267

(s), 1183 (w), 1149 (m), 1059 (m), 1015 (s), 912 (m), 883 (m),

834 (s), 796 (vs), 730 (vs), 695 (vs), 657 (m), 595 (w), 458 (s),

C₂₅H₃₅ISeMo: C, 47.1%; H, 5.5%. Found: C, 46.9%; H, 5.4%.

IR Data (KBr disk, cm^Ϫ1): 3056 (vs), 2963 (vs), 2870 (s), 1895

(w) [ν(Mo–H)], 1578 (w), 1485 (vs), 1462 (s), 1381 (s), 1313

(w), 1272 (m), 1193 (w), 1149 (m), 1018 (s), 914 (s), 843 (m),

792 (s), 745 (s), 689 (m), 643 (w), 581 (w), 471 (m), 406 (w). ¹H

NMR (CDCl₃): Ϫ9.12 [s, ²J_Se–H= 14, Mo–H], 1.20 [s, C₅H₄{C-

(CH₃)₃}], 2.67 [s, CH₃SeC₆H₅], 4.35 [br s, 1 H of C₅H₄{C-

(CH₃)₃}], 4.59 [br s, 1 H of C₅H₄{C(CH₃)₃}], 5.30 [very br, 1 H

of C₅H₄{C(CH₃)₃}], 5.77 [br s, 1 H of C₅H₄{C(CH₃)₃}], 7.32

1

409 (m). H NMR (C₆D₆): 0.74 [s, C₅H₄{C(CH₃)₃}], 4.69 [t,

³J_H–H= 2.5, 2 H of C₅H₄{C(CH₃)₃}], 5.03 [t, J_H–H= 2.5, 2 H

3

of C₅H₄{C(CH₃)₃}], 6.92 [t, J_H–H= 7, 2 H of TeC₆H₅], 7.07 [t,

3

[d, J_H–H= 7, 2 H of CH₃SeC₆H₅], 7.38 [t, J_H–H= 7, 1 H of

³J_H–H= 7, 1 H of TeC₆H₅], 8.00 [d, J_H–H= 8, 2 H of TeC₆H₅].

3

CH₃SeC₆H₅], 7.45 [t, J_H–H= 7, 2 H of CH₃SeC₆H₅]. ¹³C NMR

3

¹³C NMR (C₆D₆): 31.4 [q, ¹J_C–H= 126, C₅H₄{C(CH₃)₃}], 32.7 [s,

1

(CDCl₃): 19.8 [q, J_C–H= 145, CH₃SeC₆H₅], 31.6 [s,

C₅H₄{C(CH₃)₃}], 31.8 [q, J_C–H= 126, C₅H₄{C(CH₃)₃}], 78.1

1

C₅H₄{C(CH₃)₃}], 88.0 [d, J_C–H= 183, 2 C of C₅H₄{C(CH₃)₃}],

91.3 [d, J_C–H= 176, 2 C of C₅H₄{C(CH₃)₃}], 113.3 [s, 1 C

1

[br d, J_C–H= 170, 1 C of C₅H₄{C(CH₃)₃}], 79.8 [br d,

of TeC₆H₅], 116.9 [s, 1 C of C₅H₄{C(CH₃)₃}], 127.0 [dt,

¹J_C–H= 180, 1 C of C₅H₄{C(CH₃)₃}], 88.0 [d, J_C–H= 182, 1 C

1

¹J_C–H= 160, J_C–H= 8, 1 C of TeC₆H₅], 128.1 [dd, J_C–H= 158,

2

1

of C₅H₄{C(CH₃)₃}], 92.4 [br d, J_C–H= 172, 1 C of C₅H₄-

²J_C–H= 8, 2 C of TeC₆H₅], 141.9 [dt, J_C–H= 160, J_C–H= 7, 2 C

1

2

1

2

{C(CH₃)₃}], 128.5 [dt, J_C–H= 163, J_C–H= 7, 2 C of CH₃Se-

of TeC₆H₅]. ¹²⁵Te NMR (C₆D₆): Ϫ195 [s].

1

2

C₆H₅], 129.0 [dt, J_C–H= 163, J_C–H= 7, 1 C of CH₃SeC₆H₅],

1

2

t

129.6 [dd, J_C–H= 163, J_C–H= 7, 2 C of CH₃SeC₆H₅], 131.6 [s,

1 C of C₅H₄{C(CH₃)₃}], 131.8 [s, 1 C of CH₃SeC₆H₅]. ⁷⁷Se

NMR (CDCl₃): 244 [s].

Reactivity of (Cp^Bu)₂Mo(TePh)H towards Ph₂Te₂

A mixture of (Cp^Bu)₂Mo(TePh)H (ca. 10 mg) and Ph₂Te₂

t

1750

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

View Article Online

t

Synthesis of [(Cp^Bu)₂Mo(PhTeMe)H]I

A solution of (Cp^Bu)₂Mo(TePh)H (65 mg, 0.12 mmol) in C₆H₆

(10 mL) was treated with excess MeI (511 mg, 3.60 mmol) for

2 hours at room temperature, resulting in the formation of a

brown precipitate. The mixture was ﬁltered, and the residue was

Acknowledgement

We thank the U.S. Department of Energy, Oﬃce of Basic

Energy Sciences (#DE-FG02-93ER14339) for support of this

research.

t

washed with toluene (2 × 5 mL) and pentane (2 × 5 mL) and

t

dried in vacuo to give [(Cp^Bu)₂Mo(PhTeMe)H]I as a brown

solid (75 mg, 92%). Analysis calcd. for C₂₅H₃₅ITeMo: C, 43.8%;

H, 5.1%. Found: C, 43.5%; H, 5.1%. IR Data (KBr disk, cm^Ϫ1):

3051 (vs), 2963 (vs), 2870 (s), 1893 (w) [ν(Mo–H)], 1620 (w),

1573 (w), 1484 (vs), 1434 (s), 1382 (s), 1270 (s), 1192 (m), 1148

(m), 1018 (s), 916 (s), 843 (s), 794 (s), 740 (s), 690 (m), 624

References

1 F. A. Cotton and G. Wilkinson, Z. Naturforsch., Teil B, 1954, 9, 417.

2 M. L. H. Green, C. N. Street and G. Wilkinson, Z. Naturforsch.,

Teil B, 1959, 14, 738.

3 (a) R. Davis and L. A. P. Kane-Maguire, in Comprehensive

Organometallic Chemistry, ed. G. Wilkinson, F. G. A. Stone and

E. W. Abel, Pergamon Press, New York, 1982, vol. 3, ch. 28,

pp. 1321–1384; (b) M. J. Morris, Comprehensive Organometallic

Chemistry II, ed. J. A. Labinger and M. J. Winter, Pergamon, New

York, 1995, vol. 5, ch. 5.

4 J. A. McCleverty, Molybdenum: An Outline of Its Chemistry and

Uses, ed. E. R. Braithwaite and J. Haber, Elsevier, Amsterdam,

1994, ch. 6, pp. 343–350 and references therein.

5 (a) T. Mise, M. Maeda, T. Nakajima, K. Kobayashi, I. Shimizu,

Y. Yamamoto and Y. Wakatsuki, J. Organomet. Chem., 1994, 473,

155; (b) T. Ito and T. Yoden, Bull. Chem. Soc. Jpn., 1993, 66, 2365.

6 L. Luo, G. Lanza, I. L. Fragala, C. L. Stern and T. J. Marks, J. Am.

Chem. Soc., 1998, 120, 3111.

1

(w), 518 (w), 460 (m), 407 (w). H NMR (CDCl₃): Ϫ9.39 [s,

²J_Te-H= 38, Mo-H], 1.08 [s, 9 H, 1 Bu^tof 2 C₅H₄{C(CH₃)₃}],

1.25 [s, 9 H, 1 Bu^tof 2 C₅H₄{C(CH₃)₃}], 2.48 [s, CH₃TeC₆H₅],

4.38 [q, ³J_H–H= 3, 1 H of 2 C₅H₄{C(CH₃)₃}], 4.47 [q, ³J_H–H= 3,

3

1 H of 2 C₅H₄{C(CH₃)₃}], 4.80 [q, J_H–H= 2, 1 H of 2

3

C₅H₄{C(CH₃)₃}], 4.82 [q, J_H–H= 2, 1 H of 2 C₅H₄{C(CH₃)₃}],

5.14 [q, ³J_H–H= 3, 1 H of 2 C₅H₄{C(CH₃)₃}], 5.45 [q, ³J_H–H= 2,

3

1 H of 2 C₅H₄{C(CH₃)₃}], 5.50 [q, J_H–H= 3, 1 H of 2

3

C₅H₄{C(CH₃)₃}], 5.58 [q, J_H–H= 2, 1 H of 2 C₅H₄{C(CH₃)₃}],

7.37 [m, 5 H of CH₃SC₆H₅]. ¹³C NMR (CDCl₃): Ϫ2.7 [q,

¹J_C–H= 137, CH₃TeC₆H₅], 31.4 [s, 1 C of 2 C₅H₄{C(CH₃)₃}],

7 For a summary of detailed synthetic procedures, see: N. D. Silavwe,

M. P. Castellani and D. R. Tyler, Inorg. Synth., 1992, 29, 204.

8 M. L. H. Green and P. J. Knowles, J. Chem. Soc., Perkin Trans. 1,

1973, 989.

9 G. J. S. Adam and M. L. H. Green, J. Organomet. Chem., 1981, 208,

299.

1

31.5 [s, 1 C of 2 C₅H₄{C(CH₃)₃}], 31.8 [q, J_C–H= 126, 3 C of

1

2 C₅H₄{C(CH₃)₃}], 32.0 [q, J_C–H= 127, 3 C of 2 C₅H₄{C-

(CH₃)₃}], 75.7 [d, ¹J_C–H= 188, 1 C of 2 C₅H₄{C(CH₃)₃}], 76.9 [d,

¹J_C–H= 182, 1 C of 2 C₅H₄{C(CH₃)₃}], 80.6 [d, ¹J_C–H= 178, 1 C

1

of 2 C₅H₄{C(CH₃)₃}], 80.8 [d, J_C–H= 178, 1 C of 2 C₅H₄-

10 J. L. Thomas, J. Chem. Soc., 1973, 95, 1838.

{C(CH₃)₃}], 85.9 [d, ¹J_C–H= 182, 1 C of 2 C₅H₄{C(CH₃)₃}], 86.1

11 Cp*₂MoH₂has also been prepared by cocondensation of Mo

atoms with Cp*H using metal vapor synthesis techniques. See:

F. G. N. Cloke, J. C. Green, M. L. H. Green and C. P. Morley,

J. Chem. Soc., Chem. Commun., 1985, 945.

1

[d, J_C–H= 181, 1 C of 2 C₅H₄{C(CH₃)₃}], 87.3 [d, J_C–H= 176,

1

1 C of 2 C₅H₄{C(CH₃)₃}], 87.4 [d, J_C–H= 176, 1 C of 2

C₅H₄{C(CH₃)₃}], 114.1 [s, 1 C of 2 C₅H₄{C(CH₃)₃}], 129.3 [s,

1 C of CH₃TeC₆H₅], 129.4 [s, 1 C of 2 C₅H₄{C(CH₃)₃}], 129.6

12 A. J. Schultz, K. L. Stearley, J. M. Williams, R. Mink and

G. D. Stucky, Inorg. Chem., 1977, 16, 3303.

1

[d, J_C–H= 161, 1 C of CH₃TeC₆H₅], 129.9 [d, J_C–H= 162, 2 C

13 If the reaction time or the amount of CCl₄is not suﬃcient,

1

t

a mixture of (Cp^Bu)₂MoCl₂and (Cp^Bu)₂Mo(H)(Cl) is obtained. H

1

of CH₃TeC₆H₅], 133.0 [d, J_C–H= 161, 2 C of CH₃TeC₆H₅].

t

¹²⁵Te NMR (CDCl₃): 547 [s].

NMR (C₆D₆) of (Cp^Bu)₂Mo(H)(Cl): 1.27 (s, 18H), 3.74 (q, 2H), 4.05

(q, 2H), 4.47 (q, 2H), 4.86 (q, 2H), Ϫ8.49 (s, 1H).

14 The tungsten counterpart has been prepared: See: I. V. Jourdain,

M Fourmigue, F. Guyon and J. Amaudrut, J. Chem. Soc., Dalton

Trans., 1998, 483.

X-Ray structure determinations

X-Ray diﬀraction data for (Cp^Bu)₂MoH₂were collected on a

t

15 The cyclopentadientyl analogues, Cp₂MoL (L = PMe₃,^aCO,^bC₂-

H₄,^bC₂H₂,^cCH₃CN^d), are known. (a) C. G. de Azevedo, M. A. A. F.

de C. T. Carrondo, A. R. Dias, A. M. Martins, M. F. M. Piedade

and C. C. Romão, J. Organomet. Chem., 1993, 445, 125; (b)

Reference 10; (c) K. L. T. Wong, J. L. Thomas and H. H.

Brintzinger, J. Am. Chem. Soc., 1974, 96, 3694; (d) Reference 16.

16 (a) T. C. Wright, G. Wilkinson, M. Motevalli and M. B. Hursthouse,

J. Chem. Soc., Dalton Trans., 1986, 2017; (b) R. M. Bullock,

C. E. L. Headford, K. M. Hennessy, S. E. Kegley and J. R. Norton,

J. Am. Chem. Soc., 1989, 111, 3897.

Bruker P4 diﬀractometer equipped with a SMART CCD

detector; data for all other complexes were collected using a

Siemens P4 diﬀractometer. Crystal data, data collection and

reﬁnement parameters are summarized in Table 5. The struc-

tures were solved using direct methods and standard diﬀerence

map techniques, and were reﬁned by full-matrix least-squares

procedures using SHELXTL.⁸²Hydrogen atoms on carbon

were included in calculated positions.

CCDC reference numbers 161663–161678.

See http://ww w .rsc.org/suppdata/dt/b1/b100372k/ for crystal-

lographic data in CIF or other electronic format.

17 The only other structurally characterized mononuclear η²-aceto-

nitrile complex listed in the Cambridge Structural Database

(Version 5.19) is [Mo(dmpe)₂(η²-MeCN)Cl][BPh₄]. See: S. J.

Anderson, F. J. Wells, G. Wilkinson, B. Hussain and M. B.

Hursthouse, Polyhedron, 1988, 7, 2615.

Summary

18 The related isonitrile complex, Cp₂MoCNMe, has also been

synthesized and proposed to have an η¹-coordination mode, similar

to the carbonyl derivative. See: M. J. Calhorda, A. R. Dias,

A. M. Martins and C. C. Romao, Polyhedron, 1989, 8, 1802.

19 M. F. Farona and K. F. Kraus, Inorg. Chem., 1970, 9, 1700.

20 (a) R. A. Michelin, M. Mozzon and R. Bertani, Coord. Chem. Rev.,

1996, 147, 299; (b) B. N. Storhoﬀ and H. C. Lewis, Jr., Coord. Chem.

Rev., 1977, 23, 1.

21 See, for example: (a) J. L. Kiplinger, A. M. Arif and T. G.

Richmond, Organometallics, 1997, 16, 246; (b) S. Thomas,

C. G. Young and E. R. T. Tiekink, Organometallics, 1998, 17, 182;

(c) M. L. H. Green, A. K. Hughes and P. Mountford, J. Chem.

Soc., Dalton Trans., 1991, 1407; (d) J. Barrera, M. Sabat and

W. D. Harman, Organometallics, 1993, 12, 4381.

A study of the tert-butylmolybdenocene dihydride system

has resulted in the synthesis of a series of complexes which

include: (i) alkyl, hydride, and halide complexes, (ii) adducts,

t

(Cp^Bu)₂MoL (L = CO, C₂H₄, C₂H₂, MeCN, PMe₃), (iii) imino-

t

acyl complexes [(Cp^Bu) Mo(η²-MeC᎐NR)]^ϩ(R = Me, Et), (iv)

᎐

2

t

chalcogenido complexes, (Cp^Bu)₂MoO, [(Cp^Bu)₂Mo(µ-E)]₂, and

t

(Cp^Bu)₂Mo(η²-E₂) (E = S, Se, Te), (v) chalcogenolate com-

t

plexes, (Cp^Bu)₂Mo(EPh)H and (Cp^Bu)₂Mo(EPh)₂(E = S, Se,

t

Te), and (vi) chalcogenoether complexes, [(Cp^Bu)₂Mo(Ph-

EMe)H]I (E = S, Se, Te). Of particular note, the iminoacyl

t

complexes [(Cp^Bu) Mo(η²-MeC᎐NR)]^ϩare obtained by alkyla-

᎐

2

22 So-called “three-electron” acetonitrile ligands have also been

described and are characterized by chemical shifts of ca. δ 175–185

ppm. See: M. Etienne, C. Carfagna, P. Lorente, R. Mathieu and

D. de Montauzon, Organometallics, 1999, 18, 3075.

tion of the nitrogen atom of the coordinated acetonitrile,

a

rather uncommon transformation. Finally, ¹H NMR

spectroscopy indicates that the barrier to inversion at the

chalcogen in the coordinated chalcogenoether complexes

23 In contrast, terminal acetonitrile complexes are typically

t

[(Cp^Bu)₂Mo(PhEMe)H] increases in the sequence S < Se < Te.

characterized by ¹³C NMR chemical shifts in the range ca. δ 118–140

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

1751

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ppm, comparable to that for free MeCN (δ 117.7 ppm). See reference

48 For [Mo(NCS)] complexes, see: (a) K.-B. Shiu, S.-T. Lin, S.-M. Peng

21(c).

and M.-C. Cheng, Inorg. Chim. Acta, 1995, 229, 153; (b) H.

Arzoumanian, R. Lopez and G. Agrifoglio, Inorg. Chem., 1994, 33,

3177; (c) S. A. Roberts, C. G. Young, C. A. Kipke, W. E. Cleland, Jr.,

K. Yamanouchi, M. D. Carducci and J. H. Enemark, Inorg. Chem.,

1990, 29, 3650; (d) A. A. Eagle, C. G. Young and E. R. T. Tiekink,

Polyhedron, 1990, 9, 2965; (e) F. A. Cotton and M. Matusz, Inorg.

Chem., 1988, 27, 2127; ( f ) A. Blagg, A. T. Hutton and B. L. Shaw,

Polyhedron, 1987, 6, 95.

t

24 Likewise, the reactions of (Cp^Bu)₂MoL (L = PMe₃, MeCN) with

t

sulfur, selenium and tellurium generate (Cp^Bu)₂Mo(η²-E₂), although

the reaction with sulfur yields a mixture with additional unidentiﬁed

species.

25 For some related [Cp₂Mo(PPh₃)R]^ϩ(R = H, Me) derivatives, see:

C. G. de Azevedo, M. J. Calhorda, M. A. A. F. de C. T. Carrondo,

A. R. Dias, V. Félix and C. C. Romão, J. Organomet. Chem., 1990,

391, 345.

49 For [M(SCN)] complexes of transition metals, see: (a) M.

Bonamico, V. Fares, L. Petrilli, F. Tarli, G. Chiozzini and

C. Riccucci, J. Chem. Soc., Dalton Trans., 1994, 3349; (b) G.

Marangoni, B. Pitteri, V. Bertolasi, V. Ferretti and P.

Gilli, Polyhedron, 1993, 12, 1669; (c) A. Fumagalli, S. Martinengo,

D. Galli, C. Allevi, G. Ciani and A. Sironi, Inorg. Chem., 1990, 29,

1408; (d) M. J. Maroney, E. O. Fey, D. A. Baldwin, R. E. Stenkamp,

L. J. Jensen and N. J. Rose, Inorg. Chem., 1986, 25, 1409;

(e) H. J. Gysling, H. R. Luss and D. L. Smith, Inorg. Chem., 1979,

18, 2696; ( f ) G. Beran, A. J. Carty, P. C. Chieh and H. A. Patel,

J. Chem. Soc., Dalton Trans., 1973, 488.

50 For [M(NCS)(SCN)] complexes, see: (a) A. J. Paviglianiti,

D. J. Minn, W. C. Fultz and J. L. Burmeister, Inorg. Chim. Acta,

1989, 159, 65; (b) G. R. Clark and G. Palenik, J. Inorg. Chem., 1970,

9, 2754.

51 R. S. Pilato, C. E. Housmekerides, P. Jernakoﬀ, D. Rubin,

G. L. Geoﬀroy and A. L. Rheingold, Organometallics, 1990, 9,

2333.

26 Other cationic molybdenocene carbonyl complexes exhibit similar

ν(CO) stretching frequencies, e.g. [Cp₂Mo(CO)H][BF₄] (2017 cm^Ϫ1).

See: J. R. Ascenso, C. G. de Azevedo, I. S. Gonçalves, E. Herdtweck,

D. S. Moreno, M. Pessanha and C. C. Romão, Organometallics,

1995, 14, 3901.

27 For structurally characterized iminoacyl complexes, see:

(a) C. H. Zambrano, P. E. Fanwick and I. P. Rothwell,

Organometallics, 1994, 13, 1174; (b) T. V. Lubben, K. Plössl,

J. R. Norton, M. M. Miller and O. P. Anderson, Organometallics,

1992, 11, 122; (c) M. D. Curtis, J. Real, W. Hirpo and W. M. Butler,

Organometallics, 1990, 9, 66; (d) L. R. Chamberlain, L. D. Durfee,

P. E. Fanwick, L. Kobriger, S. L. Latesky, A. K. McMullen,

I. P. Rothwell, K. Folting, J. C. Huﬀman, W. E. Streib and R. Wang,

J. Am. Chem. Soc., 1987, 109, 390; (e) A. M. Barriola, A. M. Cano,

T. Cuenca, F. J. Fernández, P. Gómez-Sal, A. Manzanero and

P. Royo, J. Organomet. Chem., 1997, 542, 247.

28 C. Sandorfy, in The Chemistry of the Carbon–Nitrogen Double Bond;

ed. S. Patai, Interscience, New York, 1970, ch. 1.

52 (a) G. Parkin and J. E. Bercaw, J. Am. Chem. Soc., 1989, 111, 391;

29 CRC Handbook of Chemistry and Physics, ed. R. C. Weast,

M. J. Astle and W. H. Beyer, CRC Press, Inc., Boca Raton, FL,

67th edn., 1986–1987, p. F158.

(b) G. Parkin and J. E. Bercaw, Polyhedron, 1988, 7, 2053.

1

53 H₂S and H₂Se are observed by H NMR spectroscopy to be a side

product of these reactions.

30 For example, the pK_aof [MeCNH]^ϩis Ϫ10. See: A. Gervasini and

A. Auroux, J. Phys. Chem., 1993, 97, 2628.

54 D. Rabinovich and G. Parkin, Inorg. Chem., 1996, 34, 6341.

t

55 Puriﬁcation of (Cp^Bu)₂Mo(η²-Te₂) requires separation from

Me₃PTe. This is achieved by addition of mercury, which decomposes

Me₃PTe to PMe₃and HgTe, and the latter material is separated

by ﬁltration. The reaction of Et₃PTe with Hg is known to give

HgTe and Et₃P. See: M. L. Steigerwald and C. R. Sprinkle,

31 A. M. Martins, M. J. Calhorda, C. C. Romão, C. Volkl, P. Kiprof

and A. C. Filippou, J. Organomet. Chem., 1992, 423, 267.

32 M. Bochmann, L. M. Wilson, M. B. Hursthouse and M. Motevalli,

Organometallics, 1988, 7, 1148.

33 (a) J. J. R. Fraústo da Silva, M. F. C. Guedes da Silva, R. A.

Hendersen, A. J. L. Pombeiro and R. L. Richards, J. Organomet.

Chem., 1993, 461, 141; (b) A. J. L. Pombeiro, Inorg. Chim. Acta,

1992, 198–200, 179;(c)A. J. L. Pombeiro, NewJ. Chem., 1994, 18, 163.

34 B. S. McGilligan, T. C. Wright, G. Wilkinson, M. Motevalli and

M. B. Hursthouse, J. Chem. Soc., Dalton Trans., 1988, 1737.

35 A. M. Martins, M. J. Calhorda, C. C. Romão, C. Völkl, P. Kiprof

and A. C. Filippou, J. Organomet. Chem., 1992, 423, 367.

36 Examples include [Cp₂W(NCMe)R]^ϩ(R = H, Me, Et),^a,b

[Cp(Cp^OR)W(NCMe)Me]^ϩ[R = CHPh(Prⁱ)],^c[Cp₂Ti(NCMe)Me]^ϩ,^d

(a) A. J. Carmichael and A. McCamley, J. Chem. Soc., Dalton

Trans., 1995, 3125; (b) P. Jernakoﬀ, J. R. Fox, J. C. Hayes, S. Lee,

B. M. Foxman and N. J. Cooper, Organometallics, 1995, 14, 4493;

(c) J. P. McNally and N. J. Cooper, J. Am. Chem. Soc., 1989, 111,

4500; (d) M. Bochmann, L. M. Wilson, M. B. Hursthouse and

R. L. Short, Organometallics, 1987, 6, 2556.

Organometallics, 1988, 7, 245.

t

56 The reaction with excess sulfur gives a mixture of (Cp^Bu)₂Mo(η²-S₂)

t

and a complex which is tentatively characterized as (Cp^Bu)₂Mo-

(η²-S₃). ¹H NMR (C₆D₆): 0.89 (s, 18H), 4.51 (t, 4H), 4.99 (t, 4H).

1

57 H NMR data (C₆D₆): 0.94 (s, 18H), 4.16 (“q”, 2H), 4.60 (“q”, 2H),

4.66 (“q”, 2H), 5.32 (“q”, 2H).

1

58 J_Se–Teis not observed for the ¹²⁵Te NMR signal due to its broad line

width.

59 A. F. Wells, Structural Inorganic Chemistry, Clarendon Press,

Oxford, 4th edn., 1975, pp. 571–573.

60 M. Herberhold, D. Reiner and U. Thewalt, Angew. Chem., Int. Ed.

Engl., 1983, 22, 1000.

61 H. Föppl, E. Busmann and F.-K. Frorath, Z. Anorg. Allg. Chem.,

1962, 314, 12.

62 B. Meyer, Chem. Rev., 1976, 76, 367.

63 For further comparison, the mean E–E bond length data for [M(η²-

E₂)] compounds listed in the Cambridge Structural Database

37 Also in support of a mechanism involving direct reaction at

t

nitrogen, (Cp^Bu)₂Mo(η²-C₂H₂), which possesses structural similarity

(Version 5.19) are: S–S (2.05 Å), and Se–Se (2.31 Å).

t

to (Cp^Bu)₂Mo(η²-MeCN), but has no lone pair of electrons, shows

no reactivity towards MeI.

64 The reaction between [(Cp^Bu)₂Mo(µ-S)]₂and sulfur precipitates an

unidentiﬁed red paramagnetic complex.

38 M. Bochmann and L. M. Wilson, J. Chem. Soc., Chem. Commun.,

1986, 1610.

65 For a review of chalcogenolate complexes, see: J. Arnold, Prog.

Inorg. Chem., 1995, 43, 353.

39 N. D. Silavwe, M. Y. Chiang and D. R. Tyler, Inorg. Chem., 1985, 24,

66 The cyclopentadienyl counterparts, Cp₂Mo(EPh)₂(E = S, Se, Te)

have been reported.^a,b,cFurthermore, Cp₂Mo(SPh)H has been

reported to be a product of the reaction between [Cp₂Mo(SPh)-

(NCMe)]PF₆and NaBH₄.^d(a) M. L. H. Green and W. E. Lindsell,

J. Chem. Soc. A, 1967, 1455; (b) M. Sato and T. Yoshida,

J. Organomet. Chem., 1975, 87, 217; (c) Reference 15(a);

(d) M. J. Calhorda, M. A. A. F. de C. T. Carrondo, A. R. Dias,

A. M. T. Domingos, M. T. L. S. Duarte, M. H. Garcia and

C. C. Romão, J. Organomet. Chem., 1987, 320, 63.

4219.

40 N. D. Silavwe, M. R. M. Bruce, C. E. Philbin and D. R. Tyler, Inorg.

Chem., 1988, 27, 4669.

41 ν(Mo᎐O) frequencies are typically ≈ 900–1000 cm^Ϫ1while the mean

᎐

Mo᎐O bond length for complexes listed in the Cambridge Structural

᎐

Database (Version 5.19) is 1.70 Å.

42 (a) G. Parkin, Prog. Inorg. Chem., 1998, 47, 1; (b) T. M. Trnka and

G. Parkin, Polyhedron, 1997, 16, 103.

43 (a) A. J. Bridgeman, L. Davis, S. J. Dixon, J. C. Green and I. N.

Wright, J. Chem. Soc., Dalton Trans., 1995, 1023; (b) Reference 6.

67 d⁰(Cp^R)₂M(ER)₂complexes, on the other hand, tend to adopt endo

conformations to maximize π-donation to the lateral vacant orbital

on the metal center. See, for example: W. A. Howard, T. M Trnka

and G. Parkin, Inorg. Chem., 1995, 34, 5900 and references therein.

68 For example, Cp₂M(EPh)₂(M = Nb, Mo, W; E = Se, Te) reacts with

MeI to give Cp₂MI₂. See reference 66(b).

44 In contrast, Me₃SiX (X = C₂H, CH₂OH, and NHSiMe₃) are

t

unreactive towards (Cp^Bu)₂MoO at 120 ЊC.

45 The term “1,2-addition” is only intended to describe the relationship

of the product to the terminal oxo complex. It is not intended to

provide a mechanistic description of the reaction.

46 (a) J. A. Kargol, R. W. Crecely and J. L. Burmeister, Inorg.

Chim. Acta, 1977, 25, L109; (b) J. A. Kargol, R. W. Crecely and

J. L. Burmeister, Inorg. Chem., 1979, 18, 2532.

47 The integrated absorption intensities of the ν(CN) band has,

nevertheless, been proposed to provide an indication of co-

ordination mode. See: W. C. Fultz, J. L. Burmeister, J. J.

MacDougall and J. H. Nelson, Inorg. Chem., 1980, 19, 1085.

69 [Cp₂Mo(SeMe₂)I]I has been isolated from the reaction of

Cp₂Mo(SeMe)₂with CH₃I. See reference 66(b).

70 The position of the broad signal was identiﬁed by integration of

this region of the spectrum. Also, this signal sharpened as the

temperature was raised.

71 It should be noted that the ¹H NMR spectrum of the

cyclopentadienyl analogue [Cp₂Mo(PhTeMe)H]I also indicates

that the two Cp ligands are inequivalent. [Cp₂Mo(PhTeMe)H]I

1752

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

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was prepared by the reaction Cp₂Mo(TePh)H with MeI. ¹H

NMR(CDCl₃) for [Cp₂Mo(PheMe)H]I: 7.53 (m, 5H), 5.35 (s, 5H),

5.31 (s, 5H), 2.61 (s, 3H), Ϫ9.35 (s, 1H, ²J_Te–H= 47 Hz).

72 See, for example: (a) W. Kutzelnigg, Angew. Chem., Int. Ed.

Engl., 1984, 23, 272; (b) W. Cherry and N. Epiotis, J. Am.

Chem. Soc., 1976, 98, 1135; (c) J. Lambert, Top. Stereochem., 1971,

6, 19.

79 D. E. Gindelberg and J. Arnold, Organometallics, 1994, 13,

4462.

80 The ¹²⁵Te NMR signal for aqueous Te(OH)₆has also been reported

to be at 707 ppm. However, we ﬁnd better internal consistency

adopting the value of 712 ppm for this reference. See: W. Tötsch,

P. Peringer and F. Sladky, J. Chem. Soc., Chem. Commun., 1981,

841.

81 R. A. Howie, G. P. McQuillan, D. W. Thompson and G. A. Lock,

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82 G. M. Sheldrick, SHELXTL, An Integrated System for Solving,

Reﬁning and Displaying Crystal Structures from Diﬀraction Data,

University of Göttingen, Göttingen, Federal Republic of Germany,

1981.

83 F. G. N. Cloke, J. P. Day, J. C. Green, C. P. Morley and A. C. Swain,

J. Chem. Soc., Dalton Trans., 1991, 789.

84 L. Labella, A. Chernega and M. L. H. Green, J. Organomet. Chem.,

1985, 485, C18.

85 L. Labella, A. Chernega and M. L. H. Green, J. Chem. Soc., Dalton

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86 D. Churchill, J. H. Shin, T. Hascall, J. M. Hahn, B. M. Bridgewater

and G. Parkin, Organometallics, 1999, 18, 2403.

73 P. Ghosh and G. Parkin, Chem. Commun., 1998, 413.

74 T. Shimizu, A. Matsuhisa, N. Kamigata and S. Ikuta, J. Chem. Soc.,

Perkin Trans. 2, 1995, 1805.

75 Furthermore, calculations on the barrier to inversion of [EX₃]^ϩ

(E = O, S, Se, Te; X = H, Me) increase in the sequence

O Ӷ Se < Se < Te. B. M Bridgewater and G. Parkin, unpublished

results.

76 (a) J. P. McNally, V. S. Leong and N. J. Cooper, in Experimental

Organometallic Chemistry, ed. A. L. Wayda and M. Y. Darensbourg,

American Chemical Society, Washington, DC, 1987, ch. 2,

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(c) D. F. Shriver and M. A. Drezdzon, The Manipulation of

Air-Sensitive Compounds, Wiley-Interscience, New York, 2nd edn.,

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87 K. Prout, T. S. Cameron, F. A. Forder, S. R. Critchley, B. Denton

and G. V. Rees, Acta Crystallogr., Sect. B, 1974, 30, 2290.

88 T. M. Klapötke, A. Schulz, T. S. Cameron and P. K. Bakshi,

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77 M. Lardon, J. Am. Chem. Soc., 1970, 92, 5063.

78 P. Granger, S. Chapelle, W. R. McWhinnie and A. Al-Rubaie,

J. Organomet. Chem., 1981, 220, 149.

89 P. Gowik, T. Klapötke and P. White, Chem. Ber., 1989, 122, 1649.

J. Chem. Soc., Dalton Trans., 2001, 1732–1753

1753

Article Doi

The syntheses, structures and reactivity of bis(tert-butylcyclopentadienyl)molybdenum derivatives: nitrogen alkylation of an η2-acetonitrile ligand and influence of the chalcogen on the barrier to inversion of chalcogenoether adducts

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