Migration and insertion processes in the reactions of the hydrocarbyl-bridged unsaturated complexes [Mo2(μ5- C5H5)2(μ-R)(μ-PCy2)(CO) 2] (R = Me, CH2Ph, Ph) with CO and

Organometallics 2009, 28, 6293–6307 6293

DOI: 10.1021/om9006856

Migration and Insertion Processes in the Reactions of the

Hydrocarbyl-Bridged Unsaturated Complexes [Mo₂(η⁵-C₅H₅)₂(μ-R)-

(μ-PCy₂)(CO)₂] (R = Me, CH₂Ph, Ph) with CO and NO

M. Angeles Alvarez, M. Esther Garcıa, M. Eugenia Martınez, Alberto Ramos,

and Miguel A. Ruiz*

´ ꢀ ꢀ

Departamento de Quımica Organica e Inorganica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain

Received August 3, 2009

The alkyl-bridged unsaturated complexes [Mo₂Cp₂(μ-R)(μ-PCy₂)(CO)₂] (R = Me, CH₂Ph) react

readily with CO (1 atm) at room temperature or below, but the products are strongly dependent on

the alkyl bridge. Thus the benzyl complex 1b is selectively carbonylated to give the hydride derivative

5

˚

[Mo₂Cp(η -C₅H₄CH₂Ph)(μ-H)(μ-PCy₂)(CO)₄] [Mo-Mo = 3.217(1) A], whereas the methyl com-

plex gives first the acetyl-bridged complex [Mo₂Cp₂{μ-κ¹:η²-C(O)Me}(μ-PCy₂)(CO)₃], which then

evolves to give up to three different products depending on the reaction conditions: the hydrides

[Mo₂Cp(η⁵-C₅H₄R⁰)(μ-H)(μ-PCy₂)(CO)₄] (R⁰= Me, C(O)Me) and the heptacarbonyl complex

˚

[Mo₂Cp(μ-PCy₂)(CO)₇] (Mo-Mo = 3.2120(3) A), the latter requiring the displacement of a Cp

ligand. The phenyl-bridged complex [Mo₂Cp₂(μ-Ph)(μ-PCy₂)(CO)₂] requires higher CO pressures

(ca. 3 atm) and temperatures (ca. 333 K) to be carbonylated at a reasonable rate, then yielding a

mixture of the corresponding hydride [Mo₂Cp(η⁵-C₅H₄Ph)(μ-H)(μ-PCy₂)(CO)₄] and the above

heptacarbonyl complex. The title complexes also react readily with NO (2000 ppm in N₂) at room

temperature, but the products obtained, again, strongly depend on the starting substrate. The

methyl-bridged complex gives a mixture of two dinitrosyl derivatives having terminal methyl

1

2

˚

([Mo₂Cp₂(Me)(μ-PCy₂)(CO)(NO)₂], Mo-Mo = 3.074(1) A) or bridging acetyl ([Mo₂Cp₂{μ-κ :η -

˚

C(O)Me}(μ-PCy₂)(NO)₂], Mo-Mo = 2.9931(6) A) ligands. The benzyl complex gives the analogous

benzyl derivative ([Mo₂Cp₂(CH₂Ph)(μ-PCy₂)(CO)(NO)₂], Mo-Mo = 3.0993(4) A) as major

˚

product, along with small amounts of the dicarbonyl [Mo₂Cp₂(CH₂Ph)(μ-PCy₂)(CO)₂(NO)₂] and

the trinitrosyl complex [Mo₂Cp₂(μ-PCy₂)(μ-NO)(NO)₂], the formation of the latter requiring the

displacement of the benzyl ligand. Finally, the phenyl-bridged complex gives again the analogous

phenyl derivative [Mo₂Cp₂(Ph)(μ-PCy₂)(CO)(NO)₂], but small amounts of dinitrosyl derivatives

having terminal benzoyl, [Mo₂Cp₂{C(O)Ph}(μ-PCy₂)(CO)(NO)₂], bridging benzoyl, [Mo₂Cp₂{μ-

κ¹:η²-C(O)Ph}(μ-PCy₂)(NO)₂], and bridging phenyl ([Mo₂Cp₂{μ-κ¹:η²-Ph}(μ-PCy₂)(NO)₂],

˚

Mo-Mo = 2.9753(5) A)) ligands are now formed. The latter complex can be selectively generated

through the photochemical decarbonylation of the major phenyl complex. In contrast, separate

experiments revealed that all hydrocarbyl complexes of the type [Mo₂Cp₂(R)(μ-PCy₂)(CO)(NO)₂]

rearrange thermally at ca. 343 K into the corresponding acyl isomers [Mo₂Cp₂{μ-κ¹:η²-C(O)R}(μ-

PCy₂)(NO)₂].

Introduction

coexist with small amounts of the nonagostic forms B,

computed to be only slightly more energetic (Chart 1).¹

Although in the agostic form the alkyl ligand formally

behaves as a three-electron donor, but does it as a one-

electron donor in the nonagostic form, the weakness of the

Recently we reported the preparation and a complete

study of the structure and bonding of the unsaturated

alkyl-bridged complexes [Mo₂Cp₂(μ-R)(μ-PCy₂)(CO)₂]

[R = Me (1a), CH₂Ph (1b)], this revealing that in the solid

state the alkyl ligands are involved in a very weak R-agostic

interaction with the dimetal center. This interaction is re-

tained in solution, but there the agostic forms A probably

C-H Mo interaction in the former structure for com-

3 3 3

pounds 1a,b probably renders almost equivalent degrees of

real unsaturation in both situations. Beyond the above

formalisms, the dimetal center in these species is highly

unsaturated, and we can more precisely describe the inter-

metallic interaction as being mainly composed of a tricentric

(Mo₂C) and two bicentric (Mo₂) bonding interactions, the

latter being of σ and π types. The latter implies the presence

of low-lying metal-based empty orbitals, which should make

these molecules highly reactive, thus providing a unique

*To whom correspondence should be addressed. E-mail: mara@

uniovi.es.

(1) (a) Garcıa, M. E.; Ramos, A.; Ruiz, M. A.; Lanfranchi, M.;

Marchio, L. Organometallics 2007, 26, 6197. (b) García, M. E.; Melon, S.;

Ramos, A.; Riera, V.; Ruiz, M. A.; Belletti, D.; Graiff, C.; Tiripicchio, A.

ꢀ

Organometallics 2003, 22, 1983.

r

2009 American Chemical Society

Published on Web 10/15/2009

pubs.acs.org/Organometallics

6294 Organometallics, Vol. 28, No. 21, 2009

Alvarez et al.

Chart 1

Among all the alkyl-bridged complexes described so far,

however, only a few of them display multiple intermetallic

bonding,⁹and the reactivity of the latter unsaturated species

has not been explored.

In a preliminary study on the chemical behavior of the

methyl-bridged complex 1a we found that, according to the

expectations based on its electronic structure, this complex

reacted readily with CO to remove both the agostic interac-

tion and the multiple metal-metal bonding. However, an

unexpected migration of the methyl ligand to yield methyl-

and acetyl-substituted cyclopentadienyl ligands was also

found to occur under mild conditions.¹⁰These are very

unusual transformations; actually, the only close migratory

transformations we can quote are the thermal decomposi-

tions above 373 K of the complexes [MCpR(CO)₃] (M = Mo

or W, R = Et, Ph, CH₂Ph) to give hexacarbonyl dimers of

the type [M₂Cp₂(CO)₆] having one or two η⁵-C₅H₄R li-

gands.¹¹Thus, we decided to study in more detail this

migratory behavior at our unsaturated dimolybdenum cen-

ters. In this paper we report our full results on the reactions of

the methyl- and benzyl-bridged complexes 1a,b with CO and

opportunity to examine at the molecular level the chemistry

of bridging alkyl ligands at a highly unsaturated dimetal site.

Alkyl-bridged complexes are species of general interest for

several reasons: they serve as models both for intermediates

in alkyl-transfer processes and for adsorbates in several

heterogeneously catalyzed reactions such as the Fischer-

Tropsch synthesis, and they are also implied as catalysts or

precursors of the homogeneous catalysts used in the polym-

erization of olefins.^2,3Although a large number of such

binuclear complexes have been reported so far, only some

of them display metal-metal bonds, these generally exhibit-

ing an R-agostic interaction with one of the metal atoms. The

reactivity reported so far for the alkyl bridges in the latter

complexes includes the oxidative addition of the agostic

C-H bond at trimetal centers,⁴rearrangement of the ligand

to a terminal coordination mode,⁵deprotonation,⁶reductive

elimination with other ligands,⁷and insertion of CO.^5b,c,8

with NO. To check the influence of the agostic C-H Mo

3 3 3

interactions on the observed reactivity, we have also studied

the phenyl-bridged complex [Mo₂Cp₂(μ-R)(μ-PCy₂)(CO)₂]

(1c), a molecule having no agostic interactions with the metal

center (Chart 1).^1aAs it will be shown below, the reactivity

toward CO and NO of the agostic complexes 1a,b is not very

different from that of the nonagostic 1c, and in all cases it

involves easy migration of the hydrocarbyl ligand up to the

cyclopentadienyl groups (carbonylation reactions), apart

from other expected results, such as the disappearance of

the agostic interactions and multiple metal-metal bonding.

Results and Discussion

(2) (a) Braunstein, P.; Boag, N. M. Angew. Chem., Ed. Int. 2001, 40,

2427. (b) Marks, T. J. Acc. Chem. Res. 1992, 25, 57.

Carbonylation of Compounds 1. The unsaturated com-

plexes [Mo₂Cp₂(μ-R)(μ-PCy₂)(CO)₂] (1a-c) react readily

with CO, but the products are strongly dependent on the

hydrocarbyl bridge. Besides this, in no instance could the

simple addition derivative of type [Mo₂Cp₂(R)(μ-PCy₂)-

(CO)₄] be obtained or even detected.

(3) For some recent work on alkyl-bridged complexes see, for exam-

ple: (a) Bryliakov, K. P.; Talsi, E. P.; Semikolenova, N. V.; Zakharov, V.

A. Organometallics 2009, 28, 3225. (b) Li, S.; Miao, W.; Tang, T.; Dong, W.;

Zhang, X.; Cui, D. Organometallics 2008, 27, 718. (c) Bryliakov, K. P.; Talsi,

E. P.; Voskoboynikov, A. Z.; Lancaster, S. J.; Bochmann, M. Organome-

tallics 2008, 27, 6333. (d) Bolton, P. D.; Clot, E.; Cowley, A. R.; Mountford,

P. J. Am. Chem. Soc. 2006, 128, 15005. (e) Dietrich, H. M.; Grove, H.;

€

Tornroos, K. W.; Anwander, R. J. Am. Chem. Soc. 2006, 128, 1458.

The benzyl complex 1b reacts with CO (1 atm) at room

temperature to give the hydride derivative [Mo₂Cp(η⁵-

C₅H₄CH₂Ph)(μ-H)(μ-PCy₂)(CO)₄] (3b), this implying a for-

mal exchange between the benzyl ligand and a cyclopenta-

dienylic hydrogen atom. In contrast, the methyl complex 1a

reacts with CO under comparable conditions to give a

mixture of the acetyl-bridged complex [Mo₂Cp₂{μ-κ¹:η²-C-

(O)Me}(μ-PCy₂)(CO)₃] (2), the methylcyclopentadienyl hy-

dride complex [Mo₂Cp(η⁵-C₅H₄Me)(μ-H)(μ-PCy₂)(CO)₄]

(3a), the heptacarbonyl [Mo₂Cp(μ-PCy₂)(CO)₇] (4), and

the acetylcyclopentadienyl hydride [Mo₂Cp{η⁵-C₅H₄C-

(O)Me}(μ-H)(μ-PCy₂)(CO)₄] (5) (Chart 2), with their relative

amounts being strongly dependent upon experimental con-

ditions. Several separated experiments revealed that the

acetyl-bridged complex 2 is the main precursor to all other

species 3-5. Thus, when 1a is reacted with CO at 273 K for 5

h, complex 2 is obtained as the almost unique product.

Compound 2, in turn, can be transformed selectively into

its isomer 3a by just storing it in the solid state for 15 days.

(f) Weng, Z.; Teo, S.; Koh, L. L.; Hor, T. S. A. Chem. Commun. 2006, 1319.

(4) (a) Calvert, R. B.; Shapley, J. R. J. Am. Chem. Soc. 1977, 99, 5225.

(b) Dutta, T. K.; Vites, J. C.; Jacobsen, G. B.; Fehlner, T. P. Organometallics

1987, 6, 842.

(5) (a) Wigginton, J. R.; Trepanier, S. J.; McDonald, R.; Ferguson,

M. J.; Cowie, M. Organometallics 2005, 24, 6194. (b) Rowsell, B. D.;

McDonald, R.; Cowie, M. Organometallics 2004, 23, 3873. (c) Trepanier, S.

J.; McDonald, R.; Cowie, M. Organometallics 2003, 22, 2638.

(6) (a) Davies, D. L.; Gracey, B. P.; Guerchais, V.; Knox, S. A. R.;

Orpen, A. G. J. Chem. Soc., Chem. Commun. 1984, 841. (b) Casey, C. P.;

Fagan, P. J.; Miles, W. H. J. Am. Chem. Soc. 1982, 104, 1134. (c) Dawkins,

G. M.; Green, M.; Orpen, A. G.; Stone, F. G. A. J. Chem. Soc., Chem.

Commun. 1982, 41.

(7) (a) Carlucci, L.; Proserpio, D. M.; D’Alfonso, G. Organometallics

1999, 18, 2091. (b) Noh, S. K.; Sendlinger, S. C.; Janiak, C.; Theopold, K. H.

J. Am. Chem. Soc. 1989, 111, 9127.

(8) (a) Samant, R. G.; Trepanier, S. J.; Wigginton, J. R.; Xu, L.;

Bierenstiel, M.; McDonald, R.; Ferguson, M. J.; Cowie, M. Organome-

tallics 2009, 28, 3407. (b) Gao, Y.; Jennings, M. C.; Puddephatt, R. J.

Organometallics 2001, 20, 1882. (c) Jeffery, J. C.; Orpen, A. G.; Stone, F. G.

A.; Went, M. J. J. Chem. Soc., Dalton Trans. 1986, 173.

(9) Apparently only a few complexes (all dichromium ones) have

been reported to have bridges across multiple metal-metal bonds:

(a) Horvath, S.; Gorelsky, S. I.; Gambarotta, S.; Korobkov, I. Angew.

Chem., Int. Ed. 2008, 47, 1. (b) Heintz, R. A.; Ostrander, R. L.; Rheingold,

A. L.; Theopold, K. H. J. Am. Chem. Soc. 1994, 116, 11387. (c) Morse, P.

M.; Spencer, M. D.; Wilson, S. R.; Girolami, G. Organometallics 1994, 13,

1646. (d) Andersen, R. A.; Jones, R. A.; Wilkinson, G. J. Chem. Soc., Dalton

Trans. 1978, 446.

ꢀ

(10) Alvarez, M. A.; Garcıa-Vivo, D.; Garcıa, M. E.; Martınez, M.

E.; Ramos, A.; Ruiz, M. A. Organometallics 2008, 27, 1973.

(11) Pittman, C. U.; Felis, R. F. J. Organomet. Chem. 1974, 72, 399.

Article

Organometallics, Vol. 28, No. 21, 2009 6295

Table 1. Selected IR^aand NMR^bData for New Compounds

compound

ν(X-O)^a

δ(P)^b

[Mo₂Cp₂{μ-κ¹:η²-C(O)Me}(μ-PCy₂)(CO)₃] (2)^c

[Mo₂Cp(η⁵-C₅H₄Me)(μ-H)(μ-PCy₂)(CO)₄] (3a)

[Mo₂Cp(η⁵-C₅H₄CH₂Ph)(μ-H)(μ-PCy₂)(CO)₄] (3b)

[Mo₂Cp(η⁵-C₅H₄Ph)(μ-H)(μ-PCy₂)(CO)₄] (3c)

[Mo₂Cp(μ-PCy₂)(CO)₇] (4)

1919 (s), 1864 (vs), 1816 (m, sh), 1583 (w)^c

1953 (m, sh), 1924 (vs), 1852 (s)

1943 (m, sh), 1925 (vs), 1853 (s)

1943 (m, sh), 1926 (vs), 1854 (s)

2067 (s), 1989 (w, sh), 1956 (vs), 1923 (s), 1856 (m)

1950 (m, sh), 1933 (vs), 1864 (s), 1678 (w)

1972 (s), 1632 (s),^f1572 (vs)^f

1977 (vs), 1636 (s),^f1570 (s)^f

1979 (vs), 1635 (s),^f1579 (s)^f

1610 (m, sh),^f1578 (vs)^f

261.3,^d215.5,^d

220.7^e

221.1

229.5^e

259.9^e

224.6^e

214.7

[Mo₂Cp{η⁵-C₅H₄C(O)Me}(μ-H)(μ-PCy₂)(CO)₄] (5)

[Mo₂Cp₂(Me)(μ-PCy₂)(CO)(NO)₂] (6a)

[Mo₂Cp₂(CH₂Ph)(μ-PCy₂)(CO)(NO)₂] (6b)

[Mo₂Cp₂(Ph)(μ-PCy₂)(CO)(NO)₂] (6c)

212.3

221.7

[Mo₂Cp₂{μ-κ¹:η²-C(O)Me}(μ-PCy₂)(NO)₂] (7a)

[Mo₂Cp₂{μ-κ¹:η²-C(O)CH₂Ph}(μ-PCy₂)(NO)₂] (7b)

[Mo₂Cp₂{μ-κ¹:η²-C(O)Ph}(μ-PCy₂)(NO)₂] (7c)

[Mo₂Cp₂(CH₂Ph)(μ-PCy₂)(CO)₂(NO)₂] (8)

[Mo₂Cp₂(μ-PCy₂)(μ-NO)(NO)₂] (9)

224.7

224.9

1612 (m, sh),^f1578 (vs)^f

1614 (m, sh),^f1579 (vs)^f

224.5^e

54.1^g

219.4

1906 (w), 1819 (vs), 1749 (m),^f1661(s)^f

1589 (vs),^h1420 (m)^h

[Mo₂Cp₂{C(O)Ph}(μ-PCy₂)(CO)(NO)₂] (10)ⁱ

[Mo₂Cp₂{μ-κ¹:η²-Ph}(μ-PCy₂)(NO)₂] (11)

1980 (vs), 1640 (s),^f1576 (s)^f

1612 (vs),^f1551 (w)^f

213.8^e

224.9

^aRecorded in dichloromethane solution, ν in cm^-1; X = C, N. ^bRecorded in CD₂Cl₂solutions at 290 K and 121.50 (³¹P) MHz, δ in ppm relative to

external 85% aqueous H₃PO₄(³¹P). ^ccis and trans isomers coexist in solution. ^dResonances for the averaged cis and trans isomers, recorded in toluene-d₈

at 290 K. When recorded at 213 K, four resonances, at 260.4 (cis-2A), 247.0 (cis-2B), 217.4 (trans-2A), and 211.5 (trans-2B), are observed. ^eRecorded in

CDCl₃. ^fν(N-O). ^gRecorded at 233 K. ^hRecorded in KBr disk. ⁱData estimated from the spectra of mixtures of compounds 7c and 10.

Chart 2

Chart 3

However, if a toluene solution of 2 is reacted with CO at room

temperature, then the major species formed is the complex 5,

along with smaller amounts of compounds 3a and 4. Finally,

an increase of the CO pressure (to ca. 3 atm) or the tempera-

ture in the above experiment causes a significant increase in

the relative amount of the heptacarbonyl complex 4.

The phenyl-bridged complex 1c is less reactive toward CO

(compared to the alkyl complexes 1a,b) since it requires

higher CO pressures (ca. 3 atm) and temperatures (ca. 333

K) to be carbonylated at a reasonable rate. Under these

conditions, a mixture of the corresponding phenylcyclopen-

tadienyl hydride [Mo₂Cp(η⁵-C₅H₄Ph)(μ-H)(μ-PCy₂)(CO)₄]

(3c) and the heptacarbonyl complex 4 is obtained.

proportion being solvent-dependent (1:1 in CD₂Cl₂; 2:1 in

toluene-d₈) and both having separated resonances for the

cyclopentadienyl ligands, as expected, while the high chemi-

cal shift of the methyl resonance (ca. 2.8 ppm in CD₂Cl₂) is

consistent with the migration of the methyl ligand to a

carbonyl, to yield an acetyl group. These isomers give rise

to very differently deshielded ³¹P NMR resonances, at 261

(major isomer in toluene) and 215 ppm (minor isomer). The

chemical shift of the major isomer is similar to those of the

isoelectronic tricarbonyl alkenyl complexes [Mo₂Cp₂{μ-

κ¹:η²-HCC(p-tol)H}(μ-PCy₂)(CO)₃] (δ_P= 251.2 ppm)^13a

and [Mo₂Cp₂{μ-κ¹:η²-HCCH₂}(μ-PCy₂)(CO)₃] (δ_P= 250.5

ppm),^13bthese complexes displaying a cisoid arrangement of

the Cp ligands with respect to the average Mo₂P plane.^13b

Therefore, we identify the major isomer in 2 as that having a

cisoid arrangement of the Cp ligands, and therefore assign

the more shielded resonance to the corresponding trans

isomer.

Solution Structure of the Tricarbonyl 2. The IR spectrum of

2 exhibits three strong to medium bands in the C-O stretch-

ing region of the carbonyl ligands (Table 1) and a weaker

band at 1583 cm^-1, which is assigned to the C-O stretch of

the acyl group. The relative intensities of the carbonyl bands

are different from those computed using DFT methods for

either the cis or the trans isomers of the isoelectronic carbyne

complex [Mo₂Cp₂(μ-COMe)(μ-PCy₂)(CO)₃],¹²but they can

be interpreted as arising from a mixture of both types of

isomers in similar amount. Actually, the NMR data to be

discussed below indicate the presence of four interconverting

isomers in solution for compound 2 (Chart 3).

The room-temperature ³¹P resonances of 2 are broad, but

on lowering the temperature, they eventually split into two

new ones with distinct intensities in each case (see Experi-

mental Section), with their relative proportions being also

solvent-dependent. We identify these resonances as arising

from the four possible isomers derived from the different

orientations of the bridging acyl ligand, assumed to have an

alkenyl-like coordination geometry, as found for the dini-

trosyl complex 7a to be discussed later on. We have labeled in

each case the major isomer as A, but the association of these

The room-temperature ¹H NMR spectra of 2 suggest the

presence of only two species in solution, with their relative

ꢀ

(12) Garcıa, M. E.; Garcıa-Vivo, D.; Ruiz, M. A.; Alvarez, S.;

ꢀ

Aullon, G. Organometallics 2007, 26, 5912.

6296 Organometallics, Vol. 28, No. 21, 2009

Alvarez et al.

Figure 1. ORTEP diagram (30% probability) of compound 3b,

with Cy rings (except the C1 atoms) and H atoms (except the

hydride ligand) omitted for clarity. Only one of the two inde-

pendent molecules present in the unit cell is shown.

˚

Table 2. Selected Bond Lengths (A) and Angles (deg) for Com-

pound 3b

Figure 2. ORTEP diagram (30% probability) of compound 4

with H atoms omitted for clarity.

Mo(1)-Mo(2)

Mo(1)-P(1)

Mo(2)-P(1)

Mo(1)-H(1)

Mo(2)-H(1)

Mo(1)-C(1)

Mo(1)-C(2)

Mo(2)-C(3)

Mo(2)-C(4)

C(14)-C(15)

3.2172(8)

2.448(2)

2.454(2)

1.70(6)

Mo(1)-P(1)-Mo(2)

Mo(1)-H(1)-Mo(2)

H(1)-Mo(1)-P(1)

H(1)-Mo(2)-P(1)

P(1)-Mo(1)-C(1)

P(1)-Mo(1)-C(2)

P(1)-Mo(2)-C(3)

P(1)-Mo(2)-C(4)

82.0(1)

127(2)

77(2)

˚

corresponding C(14)-C(15) length of 1.493(9) A being as

expected for a single bond between sp²and sp³carbon

atoms.¹⁷

74(2)

1.90(6)

75.0(2)

103.4(2)

102.7(2)

75.1(2)

Spectroscopic data in solution for compounds 3 and 5

(Table 1 and Experimental Section) are similar to each other

and comparable to those of similar complexes of the type

[M₂Cp₂(μ-H)(μ-PRR⁰)(CO)₄] (M = Mo, W),^15,16,18,19thus

needing no detailed comments. We only note that, because of

the presence of a substituent in one of the Cp rings and the

asymmetry of the corresponding Mo center, all four CH

groups in the substituted Cp ring are inequivalent and give

1.961(7)

1.950(7)

1.941(7)

1.971(7)

1.491(9)

isomers with the drawings in Chart 3 within each pair is

arbitrary.

The ¹³C{¹H} NMR spectrum for the absolute major

isomer cis-2A displays a highly deshielded acyl resonance

at 276 ppm, a chemical shift similar to those in complexes of

the type [MoCp{C(O)R}(CO)₂(PR⁰₃)].¹⁴Moreover, the car-

bonyl ligands give rise to three distinct resonances, with

chemical shifts and P-C couplings comparable to those of

the isoelectronic cis-[Mo₂Cp₂(μ-COMe)(μ-PCy₂)(CO)₃]¹²

and cis-[Mo₂Cp₂{μ-κ¹:η²-HCCRH}(μ-PCy₂)(CO)₃].¹³

Solid-State and Solution Structure of Compounds 3 and 5.

The molecule of compound 3b (Figure 1 and Table 2) is built

up from two MoCp(CO)₂fragments placed in a transoid

arrangement and bridged by phosphide and hydride ligands.

This structure is comparable to those most commonly found

for phosphide-hydride complexes of the type [Mo₂Cp₂(μ-

H)(μ-PRR⁰)(CO)₄]^15,16and thus needs no detailed com-

ments. The most relevant feature is the presence of the benzyl

group as a substituent in one cyclopentadienyl ring, with the

rise to separated H and ¹³C NMR resonances. The same

1

applies to the ¹³C NMR resonances of the carbonyl ligands,

which give rise to two doublets (C cis to P) and two singlets

(C trans to P) as a result of their distinct P-C couplings. This

is a well-known trend for mononuclear carbonyl complexes

of the type [MCpX(CO)₂(PR₃)] (M = Mo, W; X = halogen,

alkyl, hydride, etc.), which systematically exhibit higher

absolute values of J_CPfor carbonyl ligands cis to the P

atoms.²⁰In the case of compound 5, the presence of the

acetyl group is revealed by the appearance of an IR band at

1678 cm^-1and of a quite deshielded ¹³C{¹H} NMR reso-

nance at 195.8 ppm, both of them in the usual region of acetyl

substituents in organic compounds.

Solid-State and Solution Structure of Compound 4. The

molecule of this heptacarbonyl complex (Figure 2 and

Table 3) displays Mo(CO)₅and MoCp(CO)₂fragments

bridged by a PCy₂ligand. The first fragment adopts a

pseudooctahedral geometry, with the sixth coordination

position roughly pointing to the midpoint of the Mo(1)-P(1)

bond, while the MoCp(CO)₂fragment exhibits the common

geometry found in complex 3b and related species. The

(13) (a) Alvarez, M. A.; Garcıa, M. E.; Ramos, A.; Ruiz, M. A.;

Lanfranchi, M.; Tiripicchio, A. Organometallics 2007, 26, 5454.

(b) Alvarez, M. A.; García, M. E.; Ramos, A.; Ruiz, M. A. J. Organomet.

Chem. 2009, 694, 3864.

(14) (a) Blekiron, P.; Lavender, M. H.; Morris, M. J. J. Organomet.

Chem. 1992, 426, C28. (b) Adams, H.; Bailey, N. A.; Blekiron, P.; Morris, M.

J. J. Chem. Soc., Dalton Trans. 1997, 3589. (c) Adams, H.; Bailey, N. A.;

Blekiron, P.; Morris, M. J. J. Chem. Soc., Dalton Trans. 2000, 3074.

(17) Huheey, J. E.; Keiter, E. A.; Keiter, R. L. Inorganic Chemistry:

Principles of Structure and Reactivity, 4th ed.; Harper Collins College

Publishers: New York, 1993.

ꢀ

(15) (a) Alvarez, C. M.; Alvarez, M. A.; Garcıa-Vivo, D.; Garcıa, M.

ꢀ

E.; Ruiz, M. A.; Saez, D.; Falvello, L. R.; Soler, T.; Herson, P. J. Chem.

(18) Garcıa, M. E.; Riera, V.; Ruiz, M. A.; Saez, D. Organometallics

Soc., Dalton Trans. 2004, 4168. (b) Alvarez, C. M.; Alvarez, M. A.; Alonso,

M.; García, M. E.; Rueda, M. T.; Ruiz, M. A. Inorg. Chem. 2006, 45, 9593.

(16) (a) Petersen, J. L.; Dahl, L. F.; Williams, J. M. J. Am. Chem. Soc.

1974, 95, 6610. (b) Jones, R. A.; Schawab, S. T.; Stuart, A. L.; Whittlesey, B.

R.; Wright, T. C. Polyhedron 1985, 4, 1689. (c) Bridgeman, A. J.; Mays, M.

J.; Woods, A. D. Organometallics 2001, 20, 2076.

2002, 21, 5515.

(19) Henrick, K.; McPartlin, M.; Horton, A. D.; Mays, M. J. J.

Chem. Soc., Dalton Trans. 1988, 1083.

(20) (a) Wrackmeyer, B.; Alt, H. G.; Maisel, H. E. J. Organomet.

Chem. 1990, 399, 125. (b) Todd, L. J.; Wilkinson, J. L.; Hickley, J. P.; Beach,

D. L.; Barnett, K. W. J. Organomet. Chem. 1978, 154, 151.

Article

Organometallics, Vol. 28, No. 21, 2009 6297

˚

Table 3. Selected Bond Lengths (A) and Angles (deg) for

Compound 4

Scheme 1. Initial Reaction Pathways in the Carbonylation of

Compounds 1a-c (O.A. = oxidative addition)

Mo(1)-Mo(2)

Mo(1)-P(1)

Mo(2)-P(1)

Mo(1)-C(1)

Mo(1)-C(2)

Mo(2)-C(3)

Mo(2)-C(4)

Mo(2)-C(5)

Mo(2)-C(6)

Mo(2)-C(7)

3.2120(3)

2.3964(6)

2.5520(6)

1.941(3)

1.967(3)

2.048(3)

2.065(3)

2.047(3)

2.068(3)

2.014(3)

Mo(1)-P(1)-Mo(2)

P(1)-Mo(1)-C(1)

P(1)-Mo(1)-C(2)

P(1)-Mo(2)-C(7)

P(1)-Mo(2)-C(3)

P(1)-Mo(2)-C(6)

P(1)-Mo(2)-C(4)

P(1)-Mo(2)-C(5)

Mo(2)-Mo(1)-C(1)

Mo(2)-Mo(1)-C(2)

80.9(1)

82.1(1)

110.1(1)

164.8(1)

88.3(1)

97.4(1)

80.8(1)

111.5(1)

117.4(1)

82.0(1)

˚

intermetallic length in 4 (3.2120(3) A) is comparable to that

in 3b and therefore consistent with the formulation of a single

Mo-Mo bond for this molecule. Incidentally, this also

implies that tricentric Mo₂H bonds (like those in the hydrides

3 and 5) are not particularly elongated when compared to

related bicentric Mo₂bonds in this sort of complex. We

finally note the strongly asymmetric coordination of the

˚

phosphide ligand, ca. 0.15 A closer to the MoCp fragment,

thus justifying an extreme description of the corresponding

˚

Mo-P bonds as of the single (P-Mo(2) = 2.5520(6) A) and

donor (PfMo(1) = 2.3964(6) A) types.

˚

The spectroscopic data in solution for 4 (Table 1 and

Experimental Section) are in full agreement with the struc-

ture found in the crystal. Thus its IR spectrum exhibits five

C-O stretching bands, with the three most energetic bands

being characteristic of Mo(CO)₅fragments.²¹The ¹³C{¹H}

NMR spectra, however, reveal the presence of dynamic

effects in solution, since at room temperature they exhibit

only four different carbonyl resonances. The two more

deshielded resonances [241.0 (d, J_CP= 22) and 234.7 ppm

(s)] have chemical shifts and P-C couplings comparable to

those observed for the hydride compounds 3 and 5 and are

thus safely assigned to the MoCp(CO)₂fragment. The most

shielded resonance (209.1 ppm, J_CP= 14) can be assigned to

the carbonyl trans to phosphorus in the Mo(CO)₅fragment,

by comparison with the data of compounds of the type

[Mo(CO)₅(PR₃)].²²Finally, the intense resonance at 210.1

ppm must correspond to the average resonance of the four

equatorial carbonyls of the Mo(CO)₅fragment. Indeed, on

lowering the temperature, this resonance eventually splits

into four different resonances. A rotational movement of the

Mo(CO)₅fragment around the Mo-CO(axial) axis can

easily account for this positional exchange.

Reaction Pathways in the Carbonylation of Compounds 1.

The reactions of compounds 1a-c with CO share many

common features and are thus likely to proceed through

analogous pathways, even if not all possible compounds have

been identified for all three starting substrates. For instance, the

acyl intermediate 2has been detected only in the reactions of the

methyl complex, although it is likely to be formed also for the

benzyl and phenyl complexes, whereas the heptacarbonyl

compound 4 is formed in significant amounts only for the

methyl and phenyl complexes, in the latter case surely because

of the more forcing conditions necessary to take the reaction to

completion in a reasonable time. Notably, in all cases the

activation of a C-H bond of a cyclopentadienyl ligand, as

required to form complexes 3 and 5, is the prevalent process,

even under the mild reaction conditions being used. In previous

work on the activation of Cp ligands at Mo₂and W₂substrates

we have shown that the coordinative unsaturation of the

dimetal center can induce reversible oxidative addition of the

cyclopentadienyl C-H bonds to give hydride cyclopentadie-

nylidene derivatives.²³As shown below, we can propose sen-

sible elemental steps that can lead to the coordinative situation

in which the necessary C-H bond cleavage step can take place.

By considering the unsaturation of the complexes 1a-c, it is

very likely that the reaction is initiated by a rapid uptake of two

CO molecules to give an electron-precise tetracarbonyl inter-

mediate A having a terminal hydrocarbyl ligand (Scheme 1),

thus paralleling the carbonylation reaction of the isoelec-

tronic stannyl-bridged complex [Mo₂Cp₂(μ-PCy₂)(μ-SnPh₃)-

(CO)₂].²⁴The intermediates A could next evolve by insertion of

CO in the Mo-C(hydrocarbyl) bond at the more crowded Mo

center, to give the acyl derivatives B. This is a well-known

reaction of mononuclear alkyl and aryl carbonyl complexes of

the transition metals.²⁵The intermediates B, however, are

electronically and coordinatively unsaturated, and they would

then evolve at least in three different ways. In the absence of

additional CO, this unsaturation might be removed in two

ways: either by rearrangement of the acyl ligand, from terminal

to a bridging position, to give compound 2 (the fastest process

for the methyl complex), or through the oxidative addition of a

C-H bond of a Cp ligand, to give the corresponding hydride

cyclopentadienylidene intermediates C (not detected), thus

paralleling the formation of the hydride complexes [M₂Cp(μ-

κ¹:η⁵-C₅H₄)(μ-H)(CO)₃(μ-A₂PXPA₂)] (M = Mo, W; X =

CH₂, O; A = Ph, OEt).^23aIn the presence of enough CO,

however, the intermediates B would just evolve to give the

electron-precise intermediates D, thought to be the precursors

of the heptacarbonyl complex 4, as discussed below.

(23) (a) Alvarez, M. A.; Alvarez, C.; Garcıa, M. E.; Riera, V.; Ruiz,

M. A. Organometallics 1997, 16, 2581, and references therein. (b) Alvarez,

M. A.; García, M. E.; Riera, V.; Ruiz, M. A.; Bois, C.; Jeannin, Y. J. Am.

Chem. Soc. 1995, 117, 1324.

(21) Braterman, P. S. Metal Carbonyl Spectra; Academic Press:

London, U.K., 1975.

(24) Alvarez, M. A.; Garcıa, M. E.; Ramos, A.; Ruiz, M. A. Orga-

nometallics 2006, 25, 5374.

(25) Crabtree, R. H. The Organometallic Chemistry of the Transition

Metals, 2nd ed.; John Wiley & Sons: New York, 1994.

(22) Mann, B. E.; Taylor, B. F. ¹³C NMR Data for Organometallic

Compounds; Academic Press: London, U.K., 1981.

6298 Organometallics, Vol. 28, No. 21, 2009

Alvarez et al.

Scheme 2. Proposed Reaction Pathways to the Hydride Com-

plexes 3a and 5 (R.E. = reductive elimination)

Scheme 3. Proposed Reaction Pathway Leading to Compound 4

(X = R, C(O)Me)

thus giving rise to a wide variety of coordination and

organometallic complexes exhibiting a rich chemistry.^27,28

It was thus expected that NO would readily react with the un-

saturated complexes 1a-c under mild conditions, although,

this ligand being an odd-electron molecule, different inser-

tion or migration processes of the hydrocarbyl groups might

be thus induced.

Diluted NO (2000 ppm in N₂) is indeed able to react

smoothly with the methyl complex 1a in toluene at room

temperature to give a 1:2 mixture of two dinitrosyl deriva-

tives, the methyl complex [Mo₂Cp₂(CH₃)(μ-PCy₂)(CO)-

(NO)₂] (6a) and its acyl-bridged isomer [Mo₂Cp₂{μ-κ¹:η²-

C(O)Me}(μ-PCy₂)(NO)₂] (7a). Under similar conditions, the

benzyl complex 1b gives the benzyl derivative [Mo₂Cp₂-

(CH₂Ph)(μ-PCy₂)(CO)(NO)₂] (6b) as major product, along

with small amounts of the dicarbonyl [Mo₂Cp₂(CH₂Ph)(μ-

PCy₂)(CO)₂(NO)₂] (8) and the trinitrosyl [Mo₂Cp₂(μ-PCy₂)-

(μ-NO)(NO)₂] (9) (Chart 4). Finally, the phenyl-bridged

complex gives again the hydrocarbyl derivative [Mo₂Cp₂-

(Ph)(μ-PCy₂)(CO)(NO)₂] (6c) as major product, but now

small amounts are obtained of dinitrosyl derivatives having

terminal benzoyl, [Mo₂Cp₂{C(O)CPh}(μ-PCy₂)(CO)(NO)₂]

(10), bridging benzoyl, [Mo₂Cp₂{μ-κ¹:η²-C(O)Ph}(μ-PCy₂)-

(NO)₂] (7c), or bridging phenyl ligands, [Mo₂Cp₂{μ-κ¹:η²-

Ph}(μ-PCy₂)(NO)₂] (11) (Chart 4). The latter can be selec-

tively generated through the photochemical decarbonylation

of the major product 6c (Scheme 4). In contrast, separated

experiments revealed that all hydrocarbyl complexes of type

6 rearrange thermally at ca. 343 K into the corresponding

acyl-bridged isomers 7. We note that the benzoyl complex 10

can be decarbonylated thermally or photochemically to give

the benzoyl-bridged derivative 7c, but the latter does not

transform into 11 even after extended photolysis. Thus it

seems that, once formed, the benzoyl ligands in these dini-

trosyl substrates do not experience deinsertion of CO easily.

Solid-State and Solution Structure of Compounds 6. The

molecular structures of 6a and 6b (Figures 3 and 4, and

Table 4) are similar to each other and display transoid

MoCp(R)(NO) and MoCp(CO)(NO) fragments bridged by

a PCy₂ligand. The intermetallic separations of ca. 3.07 and

The formation of compound 5 can be justified as a result of

a reductive elimination between the acyl and cyclopentadie-

nylidene ligands in the intermediate C when R = Me, this

giving first an unsaturated tricarbonyl intermediate F that

would finally accept another CO molecule (Scheme 2). The

formation of compounds 3a-c might proceed analogously,

but requires a deinsertion process of CO from C to give a

related complex E having an hydrocarbyl (instead of acyl)

terminal ligand. This is not unlikely, because the carbonyla-

tion of alkyl or aryl complexes to give the corresponding acyl

derivatives is often a reversible process.²⁵Additionally, we

cannot exclude that the intermediates E would directly come

from A after decarbonylation and C-H bond cleavage steps.

Finally, the formation of the heptacarbonyl 4, which is

favored under pressure of CO, can be rationalized as a

further reaction of the corresponding intermediates A or D

with CO (Scheme 3), this forcing the migration of the

hydrocarbyl or acyl groups to the Cp ligand to give penta-

carbonyl intermediates H having a η⁴-cyclopentadiene li-

gand, which would finally be displaced by two additional CO

molecules to give compound 4. Although the migration of an

alkyl or aryl ligand to a metal-bound Cp ligand is a rare

process, it has been observed occasionally. For instance, the

phenyl complex [VCp₂Ph] reacts in this way with CO to give the

phenylcyclopentadiene derivative [VCp(η⁴-C₅H₅Ph)(CO)₂],

although the related methyl and benzyl complexes give only

the more common acyl derivatives [VCp₂{C(O)R}(CO)].²⁶

Reactions of Compounds 1a-c with NO. Nitrogen mon-

oxide is a remarkable molecule able to strongly bind to

transition metal atoms in both high and low oxidation states,

˚

3.10 A, respectively, are consistent with the formulation of

single metal-metal bonds for these 34-electron complexes

and are comparable to that measured in the related dinitrosyl

(26) Fachinetti, G.; Floriani, C. J. Chem. Soc., Chem. Commun. 1974,

516.

(27) Richter-Addo, G. B.; Legzdins, P. Metal Nitrosyls; Oxford

University Press: Oxford, U.K., 1992.

(28) (a) Hayton, T. W.; Legzdins, P.; Sharp, W. B. Chem. Rev. 2002,

102, 935. (b) Ford, P. C.; Lorkovic, I. M. Chem. Rev. 2002, 102, 993.

(c) Mingos, D. M. P.; Sherman, D. J. Adv. Inorg. Chem. 1989, 34, 293.

(d) Gladfelter, W. L. Adv. Organomet. Chem. 1985, 24, 41.

complex [Mo₂Cp*₂(μ-PHPh)₂(NO)₂] [3.099(2) A],²⁹as they

˚

are the M-N and N-O bond lengths. The phosphide ligand

(29) Legzdins, P.; Ross, K. J.; Sayers, S. F.; Rettig, S. J. Organome-

tallics 1997, 16, 190.

Article

Organometallics, Vol. 28, No. 21, 2009 6299

Scheme 4. Thermal andPhotochemical EvolutionofCompounds6

Chart 4

Figure 3. ORTEP diagram (30% probability) of compound 6a,

with Cy rings (except the C1 atoms) and H atoms omitted for

clarity. Only one of the two independent molecules present in the

unit cell is shown.

Figure 4. ORTEP diagram (30% probability) of compound 6b,

with Cy rings (except the C1 atoms) and H atoms omitted for

clarity.

is expectedly bound in a significantly asymmetric way, closer

˚

(by ca. 0.1 A) to the electron-poorer metal atom, so we might

again represent the corresponding interactions as single

relative intensities of both N-O stretching bands are similar

in all cases is somewhat unexpected considering that the

relative positioning of these ligands is of a transoid type, but

this can be attributed to the coupling of the C-O and N-O

stretches, with it increasing the intensity of the symmetrical

stretch.

˚

(P-Mo ca. 2.50 A) and donor (PfMo ca. 2.40 A) bonds,

thus achieving an 18-electron configuration at each metal

center. The hydrocarbyl ligands display Mo-C lengths of

˚

2.205(8) and 2.272(3) A, respectively, which suggest a strong

binding of these groups to the metal atoms since, for

instance, the methyl complexes of the type [MoL(CO)₃Me]

(L = substituted η⁵-Cp ligand) display Mo-C lengths of ca.

The ³¹P{¹H} NMR spectra of compounds 6 display a

resonance at ca. 215 ppm, not far from those of the hydrides

3 and all other complexes with a single metal-metal bond

reported in this work (Table 1). The ¹H and ¹³C NMR

spectra display the expected resonances derived from the

presence of inequivalent Cp and Cy groups, in addition to

those corresponding to the metal-bound hydrocarbyl group

in each case and deserve no special comments. We note only

that the phenyl complex 6c gives rise to five (¹H) and six (¹³C)

different resonances in the normal aromatic region. From

this we conclude that there is a severe steric crowding in the

molecule preventing the Ph ring from free rotation around

the Mo-C bond. In line with this, an inspection of the crystal

structure of compounds 6a and 6b reveals a close proximity

between some of the methyl (or benzyl) and cyclohexyl H

atoms.

30

˚

2.30 A.

The spectroscopic data in solution for compounds 6a-c

(Table 1 and Experimental Section) are similar to each other

and consistent with the structures just discussed. They all

exhibit a strong C-O stretching band at ca. 1975 cm^-1in the

region of terminal carbonyls and two strong bands at ca.

1635 and 1575 cm^-1, consistent with the presence of two

terminal nitrosyl ligands in each case. The fact that the

€

(30) (a) Zhao, J.; Santos, A. M.; Herdtweck, E.; Kuhn, F. E. J. Mol.

€

Catal. A 2004, 222, 265. (b) Kornich, J.; Haubold, S.; He, J.; Reimelt, O.;

Heck, J. J. Organomet. Chem. 1999, 584, 329. (c) El Mouatassim, B.;

Elamouri, H.; Vaissermann, J.; Jaouen, G. Organometallics 1995, 14, 3296.

(d) Rogers, R. D.; Atwood, J. L.; Rausch, M. D.; Macomber, D. W. J. Chem.

Crystallogr. 1990, 20, 555.

6300 Organometallics, Vol. 28, No. 21, 2009

Alvarez et al.

˚

Table 4. Selected Bond Lengths (A) and Angles (deg) for Com-

pounds 6a and 6b

6a

6b

Mo(1)-Mo(2)

Mo(1)-P

3.074(1)

2.502(2)

2.401(2)

1.794(6)

1.760(6)

1.991(7)

2.205(8)

77.6(1)

89.8(2)

136.7(2)

87.4(2)

126.2(2)

78.0(2)

97.9(2)

84.5(2)

96.1(2)

3.0993(4)

2.513(1)

2.402(1)

1.797(3)

1.775(3)

1.976(4)

2.272(3)

78.2(1)

94.3(1)

133.8(1)

85.3(1)

122.9(1)

76.8(1)

99.8(1)

Mo(2)-P

Mo(1)-N(1)

Mo(2)-N(2)

Mo(1)-C(1)

Mo(2)-C(2)

Mo(1)-P-Mo(2)

Mo(1)-Mo(2)-N(2)

Mo(1)-Mo(2)-C(2)

Mo(2)-Mo(1)-N(1)

Mo(2)-Mo(1)-C(1)

P-Mo(1)-C(1)

P-Mo(1)-N(1)

P-Mo(2)-C(2)

P-Mo(2)-N(2)

Figure 5. ORTEP diagram (30% probability) of compound 7a,

with Cy rings (except the C1 atoms) and H atoms omitted for

clarity.

mode, which leaves the O atom within the M₂C plane.^8aIn

contrast, the O atom of the acyl ligand in 7a is well above the

Mo₂C plane, and this in fact causes a significant distortion in

the nitrosyl ligands, with one of them pointing away from the

dimetal center, surely to avoid unfavorable repulsions with

the methyl group (Mo-Mo-NO = 113.2(2)^o), while the

second nitrosyl remains almost normal to the intermetallic

vector (Mo-Mo-NO = 87.3(1)^o).

The spectroscopic data in solution for compounds 7a-c

(Table 1 and Experimental Section) are similar to each other

and consistent with the solid-state structure of 7a just

discussed. The IR spectra of these complexes exhibit N-O

stretching bands at ca. 1610 and 1580 cm^-1with medium and

strong intensities, respectively, thus indicating the retention

in solution of the transoid arrangement of the nitrosyl

ligands. The ¹H NMR spectra exhibit two cyclopentadienyl

resonances in each case, as expected, and the methyl reso-

nance of 7a appears at 2.65 ppm, a chemical shift comparable

to that in compound 2. Finally, the acyl group gives rise in all

cases to a characteristically deshielded ¹³C NMR resonance

at ca. 270 ppm, a chemical shift also comparable to that of

the corresponding resonance in the acetyl-bridged complex 2

(276.0 ppm for the isomer cis-2A).

Solution Structure of Compounds 8-10. The IR spectrum

of compound 8 exhibits two C-O stretching bands of weak

and strong intensities at 1906 and 1819 cm^-1and two N-O

stretching bands of medium and strong intensities at 1749

and 1661 cm^-1, respectively (Table 1). The C-O bands are

comparable to those of trans-dicarbonyl complexes of the

type [MoCp(R)(CO)₂(PR₃)],³²whereas the N-O bands are

similar to those exhibited by the mononuclear complexes

[MoCp(NO)₂X] (X = Me, Et, Ph, iBu, Cl).³³In addition, the

phosphide ligand gives rise to an abnormally shielded reso-

nance at 54.1 ppm, an effect observed for dialkyl- and diaryl-

phosphide ligands bridging metal atoms without metal-

metal bonds.³⁴All this strongly supports the formulation

81.3(1)

97.5(1)

˚

Table 5. Selected Bond Lengths (A) and Angles (deg) for

Compound 7a

Mo(1)-Mo(2)

Mo(1)-P(1)

Mo(2)-P(1)

Mo(1)-N(1)

Mo(2)-N(2)

Mo(1)-C(1)

Mo(1)-Ο(3)

Mo(2)-C(1)

C(1)-Ο(3)

2.9931(6)

2.473(1)

2.411(1)

1.775(5)

1.770(5)

2.345(5)

2.111(3)

2.068(5)

1.313(6)

1.219(6)

1.216(6)

1.512(8)

Mo(1)-P(1)-Mo(2)

Mo(1)-Mo(2)-Ν(2)

Mo(2)-Μο(1)-Ν(1)

Mo(1)-N(1)-Ο(1)

Mo(2)-N(2)-Ο(2)

Mo(1)-Ο(3)-C(1)

Mo(2)-C(1)-Ο(3)

Mo(2)-C(1)-C(2)

O(3)-C(1)-C(2)

75.6(1)

116.2(2)

87.3(1)

169.7(4)

173.4(5)

82.9(3)

120.5(4)

124.6(4)

114.6(5)

89.3(1)

N(1)-Ο(1)

N(2)-Ο(2)

C(1)-C(2)

P(1)-Mo(1)-C(1)

P(1)-Mo(2)-C(1)

98.0(1)

Solid-State and Solution Structure of Compounds 7. The

molecular structure of the acetyl-bridged complex 7a

(Figure 5 and Table 5) exhibits two MoCp(NO) fragments

arranged in a transoid manner and bridged by phosphide and

˚

acyl ligands. The intermetallic length of 2.9931(6) A is

shorter than that in 6 yet consistent with the formulation

of a single bond for this 34-electron complex. The acyl ligand

bridges the dimetal center in an alkenyl-like (κ¹:η²) mode

characterized by relatively short Mo-C(bridgehead) dis-

tances to both metal atoms.¹³Thus the Mo(2)-C(1) distance

˚

of 2.068(5) A is substantially shorter than those in “normal”

˚

terminal acyl complexes (ca. 2.26 A for compounds of the

type [MoCp{C(O)R}(CO)₂(PR₃)]),^14b,cwhile the Mo(1)-

C(1) length of 2.345(1) A is only slightly longer than these

˚

reference values. On the other hand, the C(1)-O(3) length of

1.313(6) A has a value intermediate between the reference

˚

values for double and single C-O bonds involving sp²

˚

carbon atoms (cf. 1.19 A for aldehydes and 1.33 A for

enols),³¹but closer to the upper limit, thus suggesting a

strong π-coordination of the double CdO bond to the Mo(1)

atom. We note that the alkenyl-like coordination of the acyl

ligand in 7a is very different from that of the acyl ligands

obtained by CO insertion in agostic methyl ligands bridging

late transition metals, usually adopting a κ¹:κ¹coordination

(32) (a) Faller, J. W.; Anderson, A. S. J. Am. Chem. Soc. 1970, 92,

5852. (b) Barnett, K. W.; Treichel, P. M. Inorg. Chem. 1967, 6, 294.

(33) Hoyano, J. R.; Legzdins, P.; Malito, J. T. J. Chem. Soc., Dalton

Trans. 1975, 1022.

(34) Carty, A. J.; MacLaughlin, S. A.; Nucciarone, D. In Phosphorus-

31 NMR Spectroscopy in Stereochemical Analysis; Verkade, J. G., Quin, L.

D., Eds.; VCH: Deerfield Beach, FL, 1987; Chapter 16.

(31) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,

A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1.

Article

Organometallics, Vol. 28, No. 21, 2009 6301

˚

Table 6. Selected Bond Lengths (A) and Angles (deg) for

Compound 11

Mo(1)-Mo(2)

Mo(1)-P(1)

Mo(2)-P(1)

Mo(1)-C(1)

Mo(2)-C(1)

Mo(2)-C(2)

Mo(1)-N(1)

Mo(2)-N(2)

C(1)-C(2)

2.9753(5)

2.395(1)

2.441(1)

2.150(4)

2.372(4)

2.514(4)

1.773(3)

1.780(3)

1.423(6)

1.424(6)

1.368(6)

1.416(6)

1.369(6)

1.442(5)

Mo(1)-P(1)-Mo(2)

N(1)-Mo(1)-Mo(2)

N(2)-Mo(2)-Mo(1)

Mo(1)-C(1)-Mo(2)

Mo(1)-C(1)-C(2)

C(2)-C(1)-C(6)

Mo(1)-N(1)-O(1)

Mo(2)-N(2)-O(2)

P(1)-Mo(1)-C(1)

P(1)-Mo(2)-C(2)

75.9(1)

97.4(1)

103.8(1)

82.1(1)

121.9(3)

113.7(4)

173.7(3)

176.2(3)

104.8(1)

112.7(1)

C(2)-C(3)

C(3)-C(4)

C(4)-C(5)

C(5)-C(6)

C(6)-C(1)

Scheme 5. Reaction Pathways in the Nitrosylation of

Compounds 1a-c (Mo = MoCp; P = PCy₂)

Figure 6. ORTEP diagram (30% probability) of compound 11,

with Cy rings (except the C1 atoms) and H atoms omitted for

clarity. Only one of the two independent molecules present in the

unit cell is shown.

of 8 as made up of a trans-MoCp(CH₂Ph)(CO)₂(PCy₂)

fragment bound through its P atom to a MoCp(NO)₂frag-

ment (Chart 4). In agreement with this, the CO ligands and

the CH₂protons of the benzyl group give rise to a single

NMR resonance in each case.

When recorded in dichloromethane solution, the IR spec-

trum of compound 9 displays two bands, at 1625 and

1587 cm^-1, of weak and strong intensities, respectively, these

being comparable to those of compounds 7 and therefore

suggestive of the presence of two terminal nitrosyls in a

transoid arrangement. In addition, a third band at lower

frequency (1420 cm^-1) can be detected when recording the

IR spectrum in a KBr disk, which indicates the presence of a

bridging nitrosyl ligand.³⁵Moreover, the inequivalence of

the diastereotopic pairs of cyclohexyl carbon atoms gives an

independent confirmation of the transoid arrangement of the

MoCp(NO) fragments of the molecule. Finally, a mass

spectrum showed the molecular ion, thus providing further

support for the composition proposed for this compound.

As for compound 10 we note that, although we were not

able to isolate it as a pure material, the available spectro-

scopic data for this complex suggest a structure comparable

to those of the carbonyldinitrosyl complexes 6, but having a

terminal benzoyl ligand. This is confirmed by the appearance

of a strongly deshielded resonance at 278.9 ppm in its ¹³C

NMR spectrum, which can be safely assigned to the metal-

bound carbon atom.

with its coordination to the dimetal center, that being of the

alkenyl (μ-κ¹:η²) type, so that the ipso carbon of the ring is

strongly bound to one molybdenum atom (Mo(1)-C(1) =

˚

2.150(4) A in the molecule of Figure 6), while the ipso and

ortho carbons are involved in a π-bonding interaction with

the second Mo atom (Mo(2)-C(1) = 2.372(4) and Mo-

˚

(2)-C(2) = 2.514(2) A). As a result, the bond involved in this

˚

interaction (C(1)-C(2) = 1.423(6) A) is elongated with

respect to the reference values of unperturbed aromatic

Solid-State and Solution Structure of Compound 11. The

crystals of the phenyl-bridged complex 11 have two inde-

pendent molecules in the unit cell with comparable geome-

tries (Figure 6 and Table 6). This complex exhibits two

MoCp(NO) fragments in an almost eclipsed conformation

and bridged by PCy₂and phenyl ligands. The nitrosyl ligands

are almost parallel to each other and essentially perpendi-

cular to the Mo₂P plane, and the intermetallic lengths of

˚

rings (ca. 1.37 A). A comparable effect has been found in

the heterometallic complex [RuIrCp*₂(μ-H)(μ-κ¹:η²-Ph)-

36

˚

(μ-PPh₂)] (C-C = 1.404(8) A). We also note that the

π-bonding interaction with the metal has a localizing effect

of the π-bonding within the aromatic ring (short-long

sequence in the C-C lengths), with a maximum difference

˚

of ca. 0.07 A for adjacent C-C bonds.

˚

2.9753(5) and 3.0403(5) A in the two independent molecules

The spectroscopic data in solution for 11 are consistent

with the retention of the solid-state structure also in solution.

Thus its IR spectrum exhibits two N-O stretching bands at

1612 and 1551 cm^-1, with strong and weak intensities,

respectively, which is indicative of a cisoid arrangement of

the nitrosyl ligands in solution. As for the phenyl ligand, it

are comparable to those measured in compounds 6a,b or 7a

and consistent with the formulation of a single Mo-Mo

bond for this molecule. This requires the phenyl ligand to be

acting as a three-electron donor group, which is consistent

(35) (a) Legzdins, P.; Young, M. A.; Batchelor, P. J.; Einstein, F. W.

J. Am. Chem. Soc. 1995, 117, 8798. (b) Alt, H. G.; Frister, T.; Trapl, E. E.;

Engelhart, H. E. J. Organomet. Chem. 1989, 362, 125.

(36) Shima, T.; Suzuki, H. Organometallics 2005, 24, 1703.

6302 Organometallics, Vol. 28, No. 21, 2009

Alvarez et al.

exhibits five inequivalent proton resonances, with one of

them being considerably shielded (5.95 ppm), which is con-

sistent with the π-coordination of the ipso and ortho carbons

of the ring to the second metal atom. We note that this

shielding is also characteristic of μ-κ¹:η²-alkenyl ligands¹³

and that a similar shielding was observed in the spectrum of

the above phenyl-bridged RuIr complex when recorded in

THF-d₈solution at 153 K. This heterometallic complex also

exhibited rapid rotation of the phenyl ring at room tempera-

ture involving the exchange between coordinated and un-

coordinated ortho positions. In the case of compound 11 this

does not take place at a significant rate even at room

temperature. However, another dynamic process must ne-

cessarily occur, since the Cp ligands give rise to a single

resonance at 5.14 ppm in spite of their inequivalence.

Although we have not investigated this in detail, it is very

likely that the phenyl ring experiences a fast movement

similar to the windshield wiper movement characteristic of

μ-κ¹:η²-alkenyl ligands, first proposed by Shapley et al.^13a,37

This movement would render equivalent environments for

both molybdenum centers while maintaining the individual

chemical environments of each carbon and hydrogen site of

the phenyl ring.

lation would lead to compounds 6. On the other hand, the

alternative coordination of the second NO molecule to the

Mo(NO)(CO) fragment would at least force a shift of the

carbonyl ligand to the other metal center, thus leading to

compounds like 8, only formed for the benzyl substrate,

perhaps for steric reasons. Finally, the room-temperature

formation of the acyl-bridged complexes 7a and 7c could be

justified by assuming a third possible evolution of the initial

intermediate P: a simple decarbonylation to give a second

paramagnetic intermediate R. Indeed it is known that mono-

nuclear radicals experience very fast decarbonylation pro-

cesses under mild conditions,³⁸and we have also shown that

binuclear radicals lose CO molecules readily at room tem-

perature.^40,41The incorporation of the second molecule to

the intermediate R would give a dinitrosyl intermediate S

having different coordination numbers at both metal centers.

This difference could be then removed in two possible ways,

either by carbonyl transfer between metal centers, this lead-

ing to compounds 6, or by insertion of CO into the Mo-R

bond followed by rearrangement of the resulting acyl ligand

from terminal to a bridging position, thus explaining the

room-temperature formation of compounds 7.

Pathways in the Nitrosylation Reactions of Compounds

1a-c. The reactions of the unsaturated compounds 1 with

NO are of only moderate selectivity, although they bear

some analogies. Moreover, even when some of the products

are related by decarbonylation or isomerization processes

actually occurring at ca. 343 K (i.e., 10 f 7c or 6a-c f 7a-c)

or under photochemical activation (i.e., 6c f 11), the very

fact that they all are formed at room temperature indicates

that there are separated pathways leading to each of them.

Besides this, we can guess that some of these products might

be formed through more than a single pathway. Thus we will

not attempt to justify the different products formed in each

case, but just outline sensible steps accounting for their

presence in the corresponding reaction mixtures (Scheme 5).

The coordination of the first NO molecule to the unsatu-

rated complexes 1 would generate an unstable paramagnetic

intermediate P rapidly reacting with a second NO molecule

to remove its unpaired electron. This is a well-known beha-

vior of mononuclear organometallic radicals,³⁸and we have

shown previously that binuclear radicals like the neutral

[Mo₂Cp₂(μ-PPh₂)(CO)₄]³⁹or the cationic ones [Mo₂Cp₂(μ-

A₂PXPA₂)(μ-CO)₂(CO)₂]^þalso react rapidly with NO under

mild conditions.⁴⁰The second NO molecule should prefer-

ably bind the more deficient MoR(CO) center, but this

would force the insertion or removal of CO in order to

reduce the subsequent steric crowding at that metal center

in the resulting intermediate Q: insertion of CO into the

Mo-R bond would give compound 10, whereas decarbony-

Concluding Remarks

The electronic and coordinative unsaturation of the hy-

drocarbyl-bridged complexes [Mo₂Cp₂(μ-R)(μ-PCy₂)(CO)₂]

(1a-c) (R = Me, CH₂Ph, Ph) facilitates the multiple uptake

of simple donor molecules such as CO or NO under mild

conditions, this invariably implying the displacement of the

hydrocarbyl group to a terminal position at an early stage of

the reaction. As a result, few differences are observed be-

tween the behavior of the agostic methyl or benzyl complexes

1a,b and the nonagostic phenyl-bridged complex 1c. The

carbonylation reactions are thought to involve in the early

stages the reversible insertion of CO into the Mo-C-

(hydrocarbyl) bonds to yield acyl-bridged intermediates,

which then invariably evolve so that the hydrocarbyl groups

eventually reach the cyclopentadienyl ligands, either by

direct migration (to give a substituted cyclopentadiene easily

displaced by CO) or through the coupling with a cyclopen-

tadienylidene ligand, in turn derived from a C-H bond

cleavage reaction. The latter route is dominant in all cases

and gives the hydride derivatives of general formula

[Mo₂Cp(η⁵-C₅H₄R⁰)(μ-H)(μ-PCy₂)(CO)₄] (R⁰= Me, C(O)-

Me, CH₂Ph, Ph).

The reactions of compounds 1a-c with NO also imply the

displacement of the hydrocarbyl groups to a terminal posi-

tion, and the insertion of CO into Mo-C(hydrocarbyl)

bonds to yield acyl derivatives is again one of the relevant

processes taking place, but now the resulting products of all

these elemental steps are thermally stable and no migration

or any other sort of coupling of the hydrocarbyl ligand with

the cyclopentadienyl groups is observed under mild or even

forcing conditions.

(37) Shapley, J. R.; Richter, S. I.; Tachikawa, M.; Keister, J. B. J.

Organomet. Chem. 1975, 94, C43.

(38) (a) Paramagnetic Organometallic Species in Activation Selectiv-

ity, Catalysis; Chanon M.; Julliard, M.; Poite, J. C., Eds.; Kluwer Academic

Publishers: Dordrecht, 1989. (b) Organometallic Radical Processes; Trog-

ler, W. C., Ed.; Elsevier: Amsterdam, 1990. (c) Astruc, D. Electron Transfer

and Radical Processes in Transition-Metal Chemistry; VCH: New York,

1995. (d) Sun, S.; Sweigart, D. A. Adv. Organomet. Chem. 1996, 40, 171.

(e) Poli, R. Chem. Rev. 1996, 96, 2135. (f) Hoff, C. D. Coord. Chem. Rev.

2000, 206, 451. (g) Torraca, K. E.; McElwee-White, L. Coord. Chem. Rev.

2000, 206, 469.

(39) Garcıa, M. E.; Riera, V.; Rueda, M. T.; Ruiz, M. A.; Lanfranchi,

M.; Tiripicchio, A. J. Am. Chem. Soc. 1999, 121, 4060.

(40) Alvarez, M. A.; Anaya, Y.; Garcıa, M. E.; Ruiz, M. A. Organo-

metallics 2004, 23, 3950.

Experimental Section

General Procedures and Starting Materials. All manipulations

and reactions were carried out under a nitrogen (99.995%)

atmosphere using standard Schlenk techniques. Solvents

were purified according to literature procedures and distilled

(41) Alvarez, M. A.; Anaya, Y.; Garcıa, M. E.; Riera, V.; Ruiz, M. A.;

Vaissermann, J. Organometallics 2003, 22, 456.

Article

Organometallics, Vol. 28, No. 21, 2009 6303

prior to use.⁴²Petroleum ether refers to that fraction distilling in

the range 338-343 K. The compounds [Mo₂Cp₂(μ-R)(μ-PCy₂)-

(CO)₂] [R = Me (1a), CH₂Ph (1b), Ph (1c)] were prepared as

described previously.¹Photochemical experiments were per-

formed using jacketed Pyrex Schlenk tubes, cooled by tap water

(ca. 288 K). A 400 W mercury lamp (Applied Photophysics)

placed ca. 1 cm away from the Schlenk tube was used for these

experiments. Chromatographic separations were carried out

using jacketed columns cooled by tap water (ca. 288 K).

Commercial aluminum oxide (Aldrich, activity I, 150 mesh)

was degassed under vacuum prior to use. The latter was mixed

under nitrogen with the appropriate amount of water to reach

the activity desired. All other reagents were obtained from the

usual commercial suppliers and used as received. IR stretching

frequencies were measured in solution, Nujol mulls, or KBr and

are referred to as ν(solvent), ν(Nujol), or ν(KBr), respectively.

Nuclear magnetic resonance (NMR) spectra were routinely

recorded at 400.13 (¹H), 162.01 (³¹P{¹H}), or 100.63 MHz

(¹³C{¹H}) at 290 K in CD₂Cl₂solutions unless otherwise stated.

Chemical shifts (δ) are given in ppm, relative to internal tetra-

methylsilane (¹H, ¹³C) or external 85% aqueous H₃PO₄(³¹P).

Coupling constants (J) are given in Hz.

isomer cis-2. Spectroscopic data for trans-2A: ³¹P{¹H} NMR

(213 K): δ 219.9 (s). ¹H NMR (213 K): δ 5.43 (d, J_PH= 2, 5H,

Cp), 5.16 (s, 5H, Cp), 2.84 (s, 3H, Me), 3.02-0.47 (m, 22H, Cy).

¹H NMR (toluene-d₈, 213 K): δ 4.86 (s, br, 5H, Cp), 4.70 (s, 5H,

Cp), 3.28-0.58 (m, 22H, Cy), the resonance of the Me group of

isomer trans-2A was masked by those of the major isomer.

Spectroscopic data for trans-2B: ³¹P{¹H} NMR: δ 213.8 (s).

¹H NMR (213 K): 3.02-0.47 (m, 22H, Cy), other resonances

of minor isomer trans-2B were masked by those of the

1

major isomers. H NMR (toluene-d₈, 213 K): δ 4.86, 4.35 (2s,

br, 2 ꢀ 5H, Cp), 3.28-0.58 (m, 22H, Cy), the resonance of the

Me group of isomer trans-2B was masked by those of the major

isomers.

Preparation of [Mo₂Cp(η⁵-C₅H₄Me)(μ-H)(μ-PCy₂)(CO)₄]

(3a). A solid sample of compound 2 (0.050 g, 0.077 mmol) was

stored at 253 K for 15 days under a nitrogen atmosphere,

whereupon it was transformed almost selectively into the tetra-

carbonyl complex 3a. The residue was dissolved in a minimum

of dichloromethane and chromatographed through an alumina

column (activity IV) at 288 K. Elution with dichloromethane-

petroleum ether (1:10) yielded an orange fraction. Removal of

solvents under vacuum from the latter fraction gave compound

3a as an orange microcrystalline solid (0.040 g, 80%). Anal.

Calcd for C₂₇H₃₅Mo₂O₄P: C, 50.17; H, 5.46. Found: C, 49.89;

H, 5.35. ¹H NMR (300.13 MHz, CDCl₃): δ 5.37 (m, 1H, C₅H₄),

5.32 (s, 5H, Cp), 5.17, 5.04, 4.93 (3m, 3 ꢀ 1H, C₅H₄), 2.27 (s, 3H,

Me), 2.73-1.03 (m, 22H, Cy), -13.18 (d, J_CP= 35, 1H, μ-H).

¹³C{¹H} NMR (100.63 MHz, 213 K): δ 245.8 (d, J_CP= 27, CO),

245.0 (d, J_CP= 25, CO), 236.7, 236.6 (2s, CO), 108.2 [s,

C¹(C₅H₄)], 92.8 (s, C₅H₄), 90.5 (s, Cp), 90.3, 90.0, 88.5 (3s,

C₅H₄), 40.1 [m, 2C¹(Cy)], 31.4 [s, 2C²(Cy)], 29.8, 29.3 [2s,

C²(Cy)], 28.0-26.9 [m, C³, C⁴(Cy)], 15.4 (s, Me).

Preparation of [Mo₂Cp₂{μ-K¹:η²-C(O)Me}(μ-PCy₂)(CO)₃]

(2). A solution of compound 1a (0.060 g, 0.102 mmol) in toluene

(4 mL) was stirred under a CO atmosphere for 5 h at 273 K to

give an orange solution. The solvent was then removed under

vacuum, and the residue was dissolved in a minimum of

dichloromethane and chromatographed through an alumina

column (activity IV) at 288 K. Elution with dichlorometha-

ne-petroleum ether (1:4) yielded an orange fraction. Removal

of solvents under vacuum from the latter fraction gave com-

pound 2 as an orange microcrystalline solid (0.050 g, 76%). In

solution, this product was shown (by ¹H or ³¹P NMR spectro-

scopy) to be a mixture of four isomers, with their equilibrium

ratios being both solvent- and temperature-dependent. Inter-

conversion within the pairs cis-2A/cis-2B and trans-2A/trans-2B

is fast on the NMR time scale at room temperature. The average

cis/trans ratios at room temperature are 1:1 in CD₂Cl₂and 2:1 in

toluene-d₈. At 213 K, the overall cis/trans ratios are 2:1 both in

CD₂Cl₂and in toluene-d₈. At this temperature, the ratios cis-2A/

cis-2B are 3:1 in CD₂Cl₂and 10:1 in toluene-d₈, while the ratios

trans-2A/trans-2B are 2:1 in CD₂Cl₂and 1:1 in toluene-d₈. Anal.

Calcd for C₂₇H₃₅Mo₂O₄P: C, 50.17; H, 5.46. Found: C, 49.89;

H, 5.50. Spectroscopic data for cis-2 (average resonances): ³¹P-

{¹H} NMR: δ 263.8 (s, br). ¹H NMR: δ 5.34 (s, 5H, Cp), 5.01 (s,

br, 5H, Cp), 2.78 (s, 3H, Me), 2.36-0.64 (m, 22H, Cy). ¹H NMR

(toluene-d₈): δ 4.86 (s, 5H, Cp), 4.72 (s, br, 5H, Cp), 2.15 (s, 3H,

Me), 2.58-0.76 (m, 22H, Cy). Spectroscopic data for cis-2A:

³¹P{¹H} NMR (213 K): δ 263.6 (s). ¹H NMR (213 K): δ 5.38 (s,

5H, Cp), 4.91 (d, J_PH= 2, 5H, Cp), 2.90 (s, 3H, Me), 3.02-0.47

(m, 22H, Cy). ¹H NMR (toluene-d₈, 213 K): δ 4.71 (s, 5H, Cp),

4.57 (s, 5H, Cp), 2.03 (s, 3H, Me), 3.28-0.58 (m, 22H, Cy).

¹³C{¹H} NMR (toluene-d₈, 213 K): δ 276.0 [s, C(O)Me], 241.2

(d, J_CP= 18, CO), 238.8 (d, J_CP= 25, CO), 237 (s, CO), 91.9,

89.2 (2s, Cp), 43.7 [s, br, C¹(Cy)], 42.2 [d, J_CP= 18, C¹(Cy)], 35.5

[s, C²(Cy)], 32.3 (s, Me), 31.3, 30.2, 29.5 [3s, C²(Cy)], 29.0-27.3

[m, C³(Cy)], 26.2, 26.1 [2s, C⁴(Cy)]. Spectroscopic data for cis-

2B: ³¹P{¹H} NMR (213 K): δ 250.4 (s). ¹H NMR (213 K): δ 5.42

(s, 5H, Cp), 5.06 (s, 5H, Cp), 2.85 (s, 3H, Me), 3.02-0.47 (m,

Preparation of [Mo₂Cp{η⁵-C₅H₄C(O)Me}(μ-H)(μ-PCy₂)-

(CO)₄] (5). A solution of compound 2 (0.050 g, 0.077 mmol) in

toluene (4 mL) was stirred under a CO atmosphere at room

temperature for 2 h to give an orange solution. The solvent was

then removed under vacuum, and the residue was dissolved in a

minimum of dichloromethane and chromatographed through

an alumina column (activity IV) at 288 K. Elution with petro-

leum ether yielded a pink fraction. Removal of solvents under

vacuum from the latter fraction gave compound [Mo₂Cp(μ-

PCy₂)(CO)₇] (4) as a pink microcrystalline solid (0.005 g, 14%).

Elution with dichloromethane-petroleum ether (1:10) yielded

an orange fraction, which yielded analogously compound 3a as

an orange microcrystalline solid (0.005 g, 10%). Elution with

dichloromethane-petroleum ether (1:3) yielded an orange frac-

tion, which gave analogously compound 5 as an orange micro-

crystalline solid (0.035 g, 67%). The crystals of 4 used in the

X-ray study were grown by the slow evaporation at room

temperature of a concentrated solution of the complex in

petroleum ether. Data for 4: Anal. Calcd for C₂₄H₂₇Mo₂O₇P:

1

C, 44.33; H, 4.18. Found: C, 43.92; H, 4.05. H NMR (300.13

MHz, CDCl₃): δ 5.28 (s, 5H, Cp), 2.73-1.03 (m, 22H, Cy).

¹³C{¹H} NMR: δ 241.0 (d, J_CP= 22, CO), 234.7 (s, CO), 210.1

(s, br, 4CO), 209.1 (d, J_CP= 14, CO), 93.0 (s, Cp), 55.3 [d, J_CP

=

13, C¹(Cy)], 48.4 [d, J_CP= 15, C¹(Cy)], 35.6 [d, J_CP= 5,

C²(Cy)], 34.8 [s, C²(Cy)], 33.8 [d, J_CP= 4, C²(Cy)], 33.4 [s,

C²(Cy)], 28.6 [d, J_CP= 10, 2C³(Cy)], 28.2 [d, J_CP= 10, C³(Cy)],

28.0 [d, J_CP= 14, C³(Cy)], 26.5 [s, 2C⁴(Cy)]. ¹³C{¹H} NMR

(213 K): δ 241.5 (d, J_CP= 22, CO), 235.6, 227.1, 227.0 (3s, CO),

209.1 (s, br, CO), 203.6, 201.5 (2s, CO). Data for 5: Anal. Calcd

for C₂₈H₃₅Mo₂O₅P: C, 49.86; H, 5.23. Found: C, 49.59; H, 5.35.

¹H NMR (300.13 MHz, CDCl₃): δ 6.03, 5.81, 5.37 (3m, 3 ꢀ 1H,

C₅H₄), 5.32 (s, 5H, Cp), 5.08 (m, 1H, C₅H₄), 2.50 (s, 3H, Me),

2.71-0.02 (m, 22H, Cy), -13.31 (d, J_PH= 35, 1H, μ-H).

¹³C{¹H} NMR (213 K): δ 243.0, 242.3 (2d, J_CP= 27, CO),

236.0, 233.8 (2s, CO), 195.8 [ s, C(O)Me], 98.7 (s, C₅H₄), 98.0 [s,

C¹(C₅H₄)], 93.2, 92.8 (2s, C₅H₄), 90.8 (s, Cp), 88.0 (s, C₅H₄), 40.6

[d, J_CP= 18, C¹(Cy)], 39.4 [d, J_CP= 16, C¹(Cy)], 31.8 [s, 2C²-

(Cy)], 30.1, 29.0 [2s, C²(Cy)], 28.0, 27.8 [2d, J_CP= 9, C³(Cy)],

1

22H, Cy). H NMR (toluene-d₈, 213 K): δ 4.78 (s, 5H, Cp),

3.28-0.58 (m, 22H, Cy), other resonances of minor isomer cis-

2B were masked by those of the major isomer. Spectroscopic

data for trans-2 (average resonances): ³¹P{¹H} NMR: δ 216.9

1

(s). H NMR: δ 5.30, 5.21 (2s, 2 ꢀ 5H, Cp), 2.78 (s, 3H, Me),

2.36-0.64 (m, 22H, Cy). ¹H NMR (toluene-d₈): δ 4.93, 4.85 (2s,

2 ꢀ 5H, Cp), 2.62-0.76 (m, 22H, Cy), the resonance of the Me

group of isomer trans-2 was masked by those of the major

(42) Armarego, W. L. F.; Chai, C. Purification of Laboratory Che-

micals, 5th ed.; Butterworth-Heinemann: Oxford, UK, 2003.

6304 Organometallics, Vol. 28, No. 21, 2009

Alvarez et al.

27.3 (s, Me), 27.2 [d, J_CP= 16, C³(Cy)], 27.1 [d, J_CP= 14, C³-

(Cy)], 26.9, 26.7 [2s, C⁴(Cy)].

22H, Cy), 0.56 (d, J_PH= 7, 3H, Mo-Me). Data for 7a: Anal.

Calcd for C₃₁H₄₃Mo₂N₂O₃P (7a C₇H₈): C, 52.11; H, 6.07; N,

3

Preparation of [Mo₂Cp(η⁵-C₅H₄CH₂Ph)(μ-H)(μ-PCy₂)(CO)₄]

(3b). A solution of compound 1b (0.050 g, 0.075 mmol) in toluene

(4 mL) was stirred under a CO atmosphere at room temperature

for 2 h to give an orange solution. The solvent was then removed

under vacuum, and the residue was dissolved in a minimum of

dichloromethane and chromatographed through an alumina

column (activity IV) at 288 K. Elution with dichloromethane-

petroleum ether (1:8) yielded an orange fraction. Removal of

solvents under vacuum from the latter fraction gave compound

3b as an orange microcrystalline solid (0.044g, 81%). Thecrystals

used in the X-ray study were grown by the slow diffusion of

petroleum ether into a THF solution of the complex at 273 K.

Anal. Calcd for C₃₃H₃₉Mo₂O₄P: C, 54.86; H, 5.44. Found: C,

54.80; H, 5.46. ¹H NMR (300.09 MHz): δ 7.36-7.24 (m, 5H, Ph),

5.41 (m, 2H, C₅H₄), 5.34 (s, 5H, Cp), 5.07, 5.00 (2m, 2 ꢀ 1H,

C₅H₄), 3.91 (s, 2H, CH₂), 2.72-1.11 (m, 22H, Cy), -13.12 (d,

3.92. Found: C, 51.73; H, 5.69; N, 4.15. ¹H NMR: δ 5.58, 5.26

(2s, 2 ꢀ 5H, Cp), 2.65 (d, J_PH= 1, 3H, C(O)Me), 2.22-1.20 (m,

22H, Cy). ¹³C{¹H} NMR: δ 274.8 [d, J_CP= 6, μ-C(O)Me], 99.0,

95.9 (2s, Cp), 49.3 [d, J_CP= 13, C¹(Cy)], 41.7 [d, J_CP= 16,

C¹(Cy)], 42.4 (s, Me), 35.7 [s, C²(Cy)], 35.3 [d, J_CP= 3, C²(Cy)],

35.1, 34.6 [2d, J_CP= 4, C²(Cy)], 28.8 [d, J_CP= 13, C³(Cy)], 28.7

[d, J_CP= 11, C³(Cy)], 28.6 [d, J_CP= 13, C³(Cy)], 28.5 [d, J_CP

=

10, C³(Cy)], 26.6, 26.5 [2s, C⁴(Cy)].

Preparation of [Mo₂Cp₂{μ-K¹:η²-C(O)Me}(μ-PCy₂)(NO)₂]

(7a). A toluene solution (4 mL) of compounds 6a and 7a

was prepared “in situ” as described above from compound 1a

(0.030 g, 0.051 mmol), and this mixture was stirred at 333 K for

2 h to give a yellow solution. The solvent was then removed

under vacuum, and the residue was dissolved in a minimum of

dichloromethane and chromatographed through an alumina

column (activity IV) at 288 K. Elution with dichloromethane-

petroleum ether (1:2) yielded a yellow fraction. Removal of

solvents under vacuum from the latter fraction gave compound

7a as a yellow microcrystalline solid (0.027 g, 84%).

J

_PH= 35, 1H, μ-H). ¹³C{¹H} NMR (213 K): δ 244.9 (d, J_CP

=

26, CO), 244.3 (d, J_CP= 25, CO), 235.8, 235.7 (2s, CO), 140.8 [s,

C¹(Ph)], 128.2 [s, C³(Ph)], 127.9 [s, C²(Ph)], 126.0 [s, C⁴(Ph)],

110.6 [s, C¹(C₅H₄)], 91.6, 90.5 (2s, C₅H₄), 89.8 (s, Cp), 88.6, 88.0

(2s, C₅H₄), 39.2, 39.1[2d, J_CP= 15, C¹(Cy)], 35.2(s, CH₂), 30.4 [s,

2C²(Cy)], 28.9, 28.6 [2s, C²(Cy)], 27.0 [s, br 2C³(Cy)], 26.4 [d,

Reaction of Compound 1b with NO. A solution of compound

1b (0.060 g, 0.090 mmol) in toluene (4 mL) was stirred at room

temperature while gently bubbling NO (2000 ppm in N₂)

through the solution for 1 h to give a green solution. The solvent

was then removed under vacuum, and the residue was dissolved

in a minimum of dichloromethane and chromatographed

through an alumina column (activity IV) at 288 K. Elution with

dichloromethane-petroleum ether (1:8) yielded a yellow frac-

tion. Removal of solvents under vacuum from the latter fraction

gave compound [Mo₂Cp₂(CH₂Ph)(μ-PCy₂)(CO)₂(NO)₂] (8) as a

yellow microcrystalline, quite air-sensitive solid (0.010 g, 15%).

Elution with dichloromethane-petroleum ether (1:6) yielded a

yellow fraction, which gave analogously compound [Mo₂Cp₂-

(CH₂Ph)(μ-PCy₂)(CO)(NO)₂] (6b) as a yellow microcrystalline

solid (0.040 g, 65%). Elution with dichloromethane-petroleum

ether (1:3) yielded a blue fraction, which gave analogously

compound [Mo₂Cp₂(μ-PCy₂)(μ-NO)(NO)₂] (9) as a blue micro-

crystalline, quite air-sensitive solid (0.005 g, 9%). The crystals of

6b used in the X-ray study were grown by the slow diffusion of

petroleum ether into a dichloromethane solution of the complex

at 253 K. Data for 6b: Anal. Calcd for C₃₀H₃₉Mo₂N₂O₃P: C,

51.59; H, 5.63; N, 4.01. Found: C, 51.50; H, 6.04; N, 3.62. IR

J

_CP= 10, 2C³(Cy)], 26.1 [s, 2C⁴(Cy)].

Preparation of [Mo₂Cp(η⁵-C₅H₄Ph)(μ-H)(μ-PCy₂)(CO)₄]

(3c). A solution of compound 1c (0.025 g, 0.038 mmol) in

toluene (4 mL) was placed in a bulb equipped with a Young’s

valve. The bulb was cooled at 77 K, evacuated under vacuum,

and then refilled with CO. The valve was then closed, and the

solution was allowed to reach room temperate and further

stirred at 333 K for 40 h. The solvent was then removed under

vacuum, and the residue was dissolved in a minimum of

dichloromethane and chromatographed through an alumina

column (activity IV) at 288 K. Elution with petroleum ether

yielded a pink fraction. Removal of solvents under vacuum from

the latter fraction gave compound [Mo₂Cp(μ-PCy₂)(CO)₇] (4) as

a pink microcrystalline solid (0.005 g, 28%). Elution with

dichloromethane-petroleum ether (1:10) yielded an orange

fraction, which gave analogously compound 3c as an orange

microcrystalline solid (0.015 g, 56%). Data for 3c: Anal. Calcd

for C₃₂H₃₇Mo₂O₄P: C, 54.25; H, 5.26. Found: C, 54.60; H, 5.46.

¹H NMR (CDCl₃): δ 7.58 (m, 2H, Ph), 7.39 (m, 2H, Ph), 7.29 (m,

1H, Ph), 5.90 (m, 2H, C₅H₄), 5.32, 5.27 (2m, 2 ꢀ 1H, C₅H₄), 5.14

(s, 5H, Cp), 2.80-0.88 (m, 22H, Cy), -13.13 (d, J_PH= 35, 1H,

μ-H).

Reaction of Compound 1a with NO. A solution of compound

1a (0.030 g, 0.051 mmol) in toluene (4 mL) was stirred at room

temperature while gently bubbling NO (2000 ppm in N₂)

through the solution for 4 h to give a yellow solution shown

(by NMR) to be a mixture of compounds [Mo₂Cp₂(Me)(μ-

PCy₂)(CO)(NO)₂] (6a) and [Mo₂Cp₂{μ-κ¹:η²-C(O)Me}(μ-

PCy₂)(NO)₂] (7a) in a 1:2 ratio. The solvent was then removed

under vacuum, and the residue was dissolved in a minimum of

dichloromethane and chromatographed through an alumina

column (activity IV) at 288 K. Elution with dichloromethane-

petroleum ether (1:5) yielded a yellow fraction. Removal of

solvents under vacuum from the latter fraction gave compound

6a as a yellow microcrystalline solid (0.010 g, 31%). Elution with

dichloromethane-petroleum ether (1:2) yielded a second yellow

fraction, which gave analogously compound 7a as an orange

microcrystalline solid (0.020 g, 62%). The crystals of 6a used in

the X-ray study were grown by the slow diffusion at 253 K of a

layer of petroleum ether into a saturated solution of the complex

in dichloromethane. The crystals of 7a used in the X-ray study

were grown by the slow diffusion of petroleum ether into a

toluene solution of the complex at 253 K. Data for 6a: Anal.

Calcd for C₂₄H₃₅Mo₂N₂O₃P: C, 46.31; H, 5.67; N, 4.50. Found:

C, 46.42; H, 5.69; N, 4.51. IR ν(Nujol): 1972 (vs), 1651 (s), 1584

(s) cm^-1. ¹H NMR: δ 5.60, 5.55 (2s, 2 ꢀ 5H, Cp), 2.41-0.36 (m,

.

ν(Nujol): 1970 (vs), 1640 (s), 1579 (s) cm^-^{1 1}H NMR: δ

7.23-7.18 (m, 4H, Ph), 6.93 (m, 1H, Ph), 5.62, 5.22 (2s, 2 ꢀ

5H, Cp), 3.65 (t, J_PH= J_HH= 9, 1H, MoCH₂), 2.46 (dd, J_HH

=

9, J_PH= 4, 1H, MoCH₂), 2.81-0.37 (m, 22H, Cy). ¹³C{¹H}

NMR: δ 229.5 (d, J_CP= 17, CO), 156.7 [d, J_CP= 3, C¹(Ph)],

128.0 [s, C³(Ph), C²(Ph)], 122.2 [s, C⁴(Ph)], 100.6, 95.1 (2s, Cp),

42.5, 41.7 [2d, J_CP= 13, C¹(Cy)], 33.2 [d, J_CP= 6, C²(Cy)], 31.6

[s, 2C²(Cy)], 31.2 [s, C²(Cy)], 28.2 [d, J_CP= 10, C³(Cy)], 28.1 [d,

J

_CP= 9, C³(Cy)], 27.9, 27.8 [2d, J_CP= 13, C³(Cy)], 26.8, 26.7

[2s, C⁴(Cy)], 14.6 (d, J_CP= 13, MoCH₂). Spectroscopic data for

8: ¹H NMR: δ 7.25 [d, J_HH= 7, 2H, H²(Ph)], 7.06 [ft, J_HH= 7,

2H, H³(Ph)], 6.83 [ft, J_HH= 7, 1H, H⁴(Ph)], 5.62 (s, br, 5H, Cp),

4.89 (s, 5H, Cp), 2.62 (d, J_PH= 1, 2H, MoCH₂), 2.10-1.17 (m,

22H, Cy). ¹H NMR (233 K): δ 7.25 [d, J_HH= 7, 2H, H²(Ph)],

7.09 [ft, J_HH= 7, 2H, H³(Ph)], 6.86 [ft, J_HH= 7, 1H, H⁴(Ph)],

5.55, 4.92 (2s, 2 ꢀ 5H, Cp), 2.61 (s, 2H, CH₂), 2.50-1.21 (m,

22H, Cy). ¹³C{¹H} NMR (233 K): δ 247.7 (s, br, CO), 153.1 [s,

C¹(Ph)], 127.4, 127.3 [2s, C³(Ph), C²(Ph)], 122.4 [s, C⁴(Ph)],

103.7, 93.0 (2s, Cp), 46.0 [s, br, C¹(Cy)], 32.9, 32.8 [2s, C²(Cy)],

28.3 [d, J_CP= 14, C³(Cy)], 28.2 [d, J_CP= 9, C³(Cy)], 26.7

[s, C⁴(Cy)], 7.06 (d, J_CP= 7, MoCH₂). Spectroscopic data for

1

9: ν(CH₂Cl₂): 1625 (w, sh), 1587 (vs) cm^-1. H NMR (300.13

MHz): δ 5.63 (s, 10H, Cp), 2.39-1.26 (m, 22H, Cy). ¹³C{¹H}

NMR: δ 99.7 (s, Cp), 48.0 [d, J_CP= 15, C¹(Cy)], 39.4 [d, J_CP

=

3, C²(Cy)], 34.6 [d, J_CP= 4, C²(Cy)], 28.8, 28.4 [2d, J_CP= 12,

C³(Cy)], 26.5 [s, C⁴(Cy)]. SIMS (m/z): 609.00 (M^þ), 579.01

(M^þ- NO), 351.87 (M^þ- 2 NO, PCy₂).

Article

Preparation of [Mo₂Cp₂{μ-K¹:η²-C(O)CH₂Ph}(μ-PCy₂)(NO)₂]

Organometallics, Vol. 28, No. 21, 2009 6305

5.68; N, 4.27. Found: C, 50.99; H, 5.58; N, 4.14. ¹H NMR

(CDCl₃): δ 7.64 (ft, J_HH= 8, 1H, Ph), 7.18 (ft, J_HH= 8, 1H, Ph),

6.80 (d, J_HH= 8, 1H, Ph), 6.43 (ft, J_HH= 8, 1H, Ph), 5.95 (d,

(7b). A toluene solution of compound 6b (0.020 g, 0.029 mmol)

was stirred for 2 h at 343 K to give a yellow solution. The solvent

was then removed under vacuum, and the residue was dissolved in

a minimum of dichloromethane and chromatographed through

an alumina column (activity IV) at 288 K. Elution with dichlor-

omethane-petroleum ether (1:3) yielded a yellow fraction. Re-

moval of solvents under vacuum from the latter fraction gave

compound 7b as a yellow microcrystalline solid (0.015 g, 75%).

Anal. Calcd for C₃₀H₃₉Mo₂N₂O₃P: C, 51.59; H, 5.63; N, 4.01.

Found: C, 51.26; H, 5.61; N, 3.86. ¹H NMR(CDCl₃): δ 7.59-7.25

J

_HH= 8, 1H, Ph), 5.14 (s, 10H, Cp), 2.39-1.26 (m, 22H, Cy).

Preparation of [Mo₂Cp₂{μ-K¹:η²-C(O)Ph}(μ-PCy₂)(NO)₂]

(7c). Method A: A toluene solution of compound 6c (0.020 g,

0.029 mmol) was stirred for 1.5 h at 343 K to give a yellow

solution. The solvent was then removed under vacuum, and the

residue was dissolved in a minimum of dichloromethane and

chromatographed through an alumina column (activity IV) at

288 K. Elution with dichloromethane-petroleum ether (1:2)

yielded a yellow fraction. Removal of solvents under vacuum

from the latter fraction gave compound 7c as a yellow micro-

crystalline solid (0.015 g, 75%). Method B: The crude mixture of

compounds 6c, 7c, 10, and 11 obtained as described above from

compound 1c (0.040 g, 0.046 mmol) and NO was further stirred

for 1 h in refluxing toluene to give a yellow solution. The solvent

was then removed under vacuum, and the residue was dissolved

in a minimum of dichloromethane and chromatographed

through an alumina column (activity IV) at 288 K. Elution with

dichloromethane-petroleum ether (1:2) yielded a yellow frac-

tion, which gave analogously compound 7c as a yellow micro-

crystalline solid (0.029 g, 70%).

(m, 5H, Ph), 5.58, 4.92 (2s, 2 ꢀ 5H, Cp), 4.86, 3.15 (2d, J_HH

=

11, 2 ꢀ 1H, CH₂), 2.40-1.10 (m, 22H, Cy). ¹³C{¹H} NMR: δ

271.6 [d, J_CP= 5, μ-C(O)CH₂Ph], 140.1 [s, C¹(Ph)], 130.4, 128.6

[2s, C³(Ph), C²(Ph)], 126.5 [s, C⁴(Ph)], 98.6, 95.8 (2s, Cp), 61.3 (s,

CH₂), 49.4 [d, J_CP= 12, C¹(Cy)], 47.5 [d, J_CP= 15, C¹(Cy)], 35.6

[s, 2C²(Cy)], 35.2, 34.7 [2d, J_CP= 5, C²(Cy)], 28.8 [d, J_CP= 13,

C³(Cy)], 28.7, 28.6 [2d, J_CP= 12, C³(Cy)], 28.5 [d, J_CP= 11,

C³(Cy)], 26.6, 26.5 [2s, C⁴(Cy)].

Reaction of Compound 1c with NO. A solution of compound

1c (0.040 g, 0.061 mmol) in toluene (40 mL) was stirred while

gently bubbling NO (2000 ppm in N₂) through the solution for

16 h to give an orange solution. The solvent was then removed

under vacuum, and the residue was dissolved in a minimum of

dichloromethane and chromatographed through an alumina

column (activity IV) at 288 K. Elution with dichloromethane-

petroleum ether (1:4) yielded a yellow fraction. Removal of

solvents under vacuum from the latter fraction gave compound

[Mo₂Cp₂(Ph)(μ-PCy₂)(CO)(NO)₂] (6c) as a yellow microcrystal-

line solid (0.020 g, 48%). Elution with dichloromethane-

petroleum ether (1:2) yielded a yellow fraction, which gave

analogously a mixture of the compounds [Mo₂Cp₂{μ-κ¹:η²-

C(O)Ph}(μ-PCy₂)(NO)₂] (7c) and [Mo₂Cp₂{C(O)Ph}(μ-PCy₂)-

(CO)(NO)₂] (10) as a yellow microcrystalline solid (ratio 7c:10

ca. 5:3), which could not be further purified. Finally, elution

with dichloromethane-petroleum ether (1:1) yielded an orange

fraction, which gave analogously compound [Mo₂Cp₂(μ-κ¹:η²-

Ph)(μ-PCy₂)(NO)₂] (11) as an orange microcrystalline solid

(0.010 g, 25%). The crystals of compound 11 used in the

X-ray were grown by slow diffusion of petroleum ether into a

dichloromethane solution of the complex at 253 K. Data for 6c:

Anal. Calcd for C₂₉H₃₇Mo₂N₂O₃P: C, 50.89; H, 5.45; N, 4.09.

Found: C, 50.80; H, 5.55; N, 3.92. ¹H NMR (CDCl₃): δ 7.44 [br,

2H, H²(Ph)], 7.02 [ft, J_HH= 7, 2H, H³(Ph)], 6.83 [ft, J_HH= 7,

1H, H⁴(Ph)], 5.65, 5.62 (2s, 2 ꢀ 5H, Cp), 2.51-0.64 (m, 22H,

Cy). ¹³C{¹H} NMR (233 K): δ 230.6 (d, J_CP= 17, CO), 162.0 [d,

J_CP= 11, C¹(Ph)], 143.9, 142.0 [2s, C²(Ph)], 127.7, 125.7 [2s,

C³(Ph)], 122.3 [s, C⁴(Ph)], 100.7, 95.2 (2s, Cp), 44.7 [d, J_CP= 17,

C¹(Cy)], 40.2 [d, J_CP= 12, C¹(Cy)], 32.2 [s, C²(Cy)], 31.2 [d,

J_CP= 4, C²(Cy)], 31.1 [d, J_CP= 5, C²(Cy)], 28.7 [s, C²(Cy)], 27.9

Preparation of [Mo₂Cp₂(μ-K¹:η²-Ph)(μ-PCy₂)(NO)₂] (11). A

toluene solution of compound 6c (0.020 g, 0.029 mmol) was

irradiated with UV-visible light at 285 K for 15 min to give an

orange solution. The solvent was then removed under vacuum,

and the residue was dissolved in a minimum of dichloromethane

and chromatographed through an alumina column (activity IV)

at 288 K. Elution with dichloromethane-petroleum ether (1:1)

yielded an orange fraction. Removal of solvents under vacuum

from the latter fraction gave compound 11 as an orange micro-

crystalline solid (0.015 g, 79%).

X-ray Structure Determination of Compounds 3b and 11. The

X-ray intensity data were collected on Smart-CCD-1000 (3b)

and Kappa-Appex-II (11) Bruker diffractometers using gra-

phite-monochromated Mo KR radiation. Cell dimensions and

orientation matrixes were initially determined from least-

squares refinements on reflections measured in three sets of 30

exposures collected in three different ω regions and eventually

refined against all reflections. The software SMART⁴³was used

for collecting frames of data, indexing reflections, and determin-

ing lattice parameters for 3b, and the software APEX⁴⁴was used

for collecting frames with the omega/phi scan measurement

method for 11. The collected frames were then processed for

integration by the software SAINT,⁴³and a multiscan absorp-

tion correction was applied with SADABS.⁴⁵Using the program

suite WinGX,⁴⁶the structure was solved by Patterson interpre-

tation and phase expansion (3b) or direct methods (11) and

refined with full-matrix least-squares on F²with SHELXL97.⁴⁷

All non-hydrogen atoms were refined anisotropically. In the

case of compound 3b two independent molecules were found in

the asymmetric unit, and three reflections had to be omitted in

order to avoid inadequate anisotropic parameters in C(53).

Most of the hydrogen atoms could be located in the Fourier

map in the last least-squares refinements, but in order to avoid a

low reflections/parameters ratio, all them except the hydride

ligands were fixed at calculated geometric positions. As for the

hydride ligands, the H(2) atom could be located in the Fourier

maps, while for H(1) possible positions were investigated by a

potential energy minima search using the program HYDEX.⁴⁸

[d, J_CP= 9, C³(Cy)], 27.2 [d, J_CP= 10, C³(Cy)], 27.5 [d, J_CP

=

14, C³(Cy)], 27.4 [d, J_CP= 11, C³(Cy)], 26.4, 26.1 [2s, C⁴(Cy)].

Data for 7c: Anal. Calcd for C₂₉H₃₇Mo₂N₂O₃P: C, 50.89; H,

5.45; N, 4.09. Found: C, 50.75; H, 5.33; N, 4.15. ¹H NMR

(CDCl₃): δ 7.84 [m, 2H, H²(Ph)], 7.42-7.17 (m, 3H, Ph), 5.39,

5.31 (2s, 2 ꢀ 5H, Cp), 2.35-1.26 (m, 22H, Cy). ¹³C{¹H} NMR

(233 K): δ 266.5 [d, J_CP= 4, C(O)Ph], 150.6 [s, C¹(Ph)], 130.1 [s,

C⁴(Ph)], 128.4, 127.0 [2s, C³(Ph), C²(Ph)], 99.1, 96.0 (2s, Cp),

52.0 [d, J_CP=10, C¹(Cy)], 42.8 [d, J_CP= 16, C¹(Cy)], 36.6 [s,

C²(Cy)], 35.7 [d, J_CP= 3, C²(Cy)], 35.0, 34.1 [2s, C²(Cy)], 28.7

[d, J_CP= 15, C³(Cy)], 28.6 [d, J_CP= 11, 2C³(Cy)], 28.3 [d, J_CP

=

10, C³(Cy)], 26.48, 26.46 [2s, C⁴(Cy)]. Spectroscopic data for 10:

¹H NMR (CDCl₃): δ 7.64 [m, 2H, H²(Ph)], 7.42-7.17 (m, 3H,

Ph), 5.70, 5.61 (2s, 2 ꢀ 5H, Cp), 2.35-1.26 (m, 22H, Cy).

¹³C{¹H} NMR (233 K): δ 278.9 [d, J_CP= 11, C(O)Ph], 228.5

(d, J_CP= 17, CO), 155.0 [s, C¹(Ph)], 129.4 [s, C⁴(Ph)], 127.0,

125.6 [2s, C³(Ph), C²(Ph)], 100.9, 95.0 (2s, Cp), 42.0, 40.6 [2d,

J_CP=15, C¹(Cy)], 34.1 [s, C²(Cy)], 32.9 [d, J_CP= 4, C²(Cy)],

30.1 [s, 2C²(Cy)], 29.1-27.5 [m, C³(Cy)], 26.4, 26.2 [2s, C⁴(Cy)].

Data for 11: Anal. Calcd for C₂₈H₃₇Mo₂N₂O₂P: C, 51.23; H,

(43) SMART & SAINT Software Reference Manuals, Version 5.051

(Windows NT Version); Bruker Analytical X-ray Instruments: Madison, WI,

1998.

(44) APEX 2, version 2.0-1; Bruker AXS Inc: Madison, WI, 2005.

(45) Sheldrick, G. M. SADABS, Program for Empirical Absortion

€

Correction; University of Gottingen: Gottingen, Germany, 1996.

(46) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.

(47) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112.

(48) Orpen, A. G. J. Chem. Soc., Dalton Trans. 1980, 2509.

6306 Organometallics, Vol. 28, No. 21, 2009

Alvarez et al.

Table 7. Crystal Data for New Compounds

6a 6b

3b

4

7a C₇H₈

3

11

mol formula

mol wt

cryst syst

C₃₃H₃₉Mo₂O₄P C₂₄H₂₇Mo₂O₇P C₂₄H₃₅Mo₂N₂O₃P C₃₀H₃₉Mo₂N₂O₃P C₃₁H₄₃Mo₂N₂O₃P C₂₈H₃₇Mo₂N₂O₂P

722.49

triclinic

P1

650.31

monoclinic

P2₁/c

622.39

orthorhombic

Pca2₁

698.48

monoclinic

P2₁/c

714.52

triclinic

P1

656.45

monoclinic

P2₁/c

space group

˚

radiation (λ, A)

0.71073

13.403(2)

15.504(3)

15.517(3)

84.337(3)

72.189(3)

83.307(3)

3042.2(9)

4

0.71073

15.2107(3)

11.5579(2)

17.7653(4)

90

125.1440(10)

90

2553.87(9)

4

1.691

1.54184

9.903(5)

27.514(5)

17.963(5)

90.000(5)

4894(3)

8

1.54184

9.10550(10)

33.0473(3)

9.75290(10)

90

105.342(2)

90

2830.18(5)

4

1.639

1.54184

8.7525(3)

12.2232(3)

14.5532(5)

87.328(3)

75.793(3)

82.829(2)

1497.32(8)

2

0.71073

14.7493(8)

19.0347(11)

18.8952(8)

90

93.055(2)

90

5297.3(5)

8

1.644

˚

a, A

˚

b, A

˚

c, A

R, deg

β, deg

γ, deg

3

˚

V, A

Z

calcd density,

g cm^-3

1.577

1.689

1.585

absorp coeff,

mm^-1

0.913

1.085

9.238

8.065

7.634

1.036

temperature, K

θ range, deg

index ranges

(h, k, l)

no. of reflns

collected

no. of indep

120(2)

100(2)

100.0(1)

1.38-26.43

-15, 16;-19,

19; 0, 19

32 980

2.25-25.35

-18, 17;-13,

0; -21, 16

23 604

3.21-73.87

-11, 10;-33,

26; -22, 20

17 200

4.89-73.91

-10, 11;-39,

40; -10, 11

15 257

3.13-73~71

-10, 10;-14,

15; -17, 17

14 309

1.38-26.02

-18, 18;-0,

23; 0, 23

40 199

12 335 (0.0579)

7844

4670 (0.0304)

4283

8162 (0.0229)

7604

5368 (0.0355)

4464

5692 (0.0289)

4984

10 434 (0.0573)

8126

reflns (R_int

no. of reflns

)

with I > 2σ(I)

R indexes [data

with I > 2σ(I)]^a

R₁= 0.0479

R₁= 0.0194

R₁= 0.0372

R₁= 0.0332

R₁= 0.0372

R₁= 0.0359

wR₂= 0.1109^b

R₁= 0.0898

wR₂= 0.0649^c

R₁= 0.0255

wR₂= 0.0958^d

R₁= 0.0403

wR₂= 0.084^e

R₁= 0.0422

wR₂= 0.1007^f

R₁= 0.0462

wR₂= 0.0706^g

R₁= 0.0545

R indexes

(all data)^a

wR₂= 0.1392^b

1.166

0/728

wR₂= 0.0756^c

1.284

0/301

wR₂= 0.0979^d

1.053

1/580

wR₂= 0.0882^e

0.999

0/343

wR₂= 0.1035^f

1.246

0/418

wR₂= 0.0778^g

1.029

0/639

GOF

no. of restraints/

params

-3

˚

ΔF (max., min.), e A

1.274, -1.714

0.641, -0.834

1.683, -0.772

0.732, -1.185

0.715, -0.684

0.815, -0.677

P

^aR =

F_o| - |F_c

/

|F_o|. wR = [ w(|F_o|²- |F_c|²)²/ w|F_o|²]^1/2. w = 1/[σ²(F_o²) þ (aP)²þ bP] where P = (F_oþ 2F_c²)/3. ^ba = 0.0470, b = 5.2766.

2

^ca = 0.0387, b = 0.9114. ^da = 0.0516, b = 14.2617. ^ea = 0.0628, b = 0. ^fa = 0, b = 10.4207. ^ga = 0.0212, b = 9.4585.

Only one minimum was found around the Mo(1)-Mo(2) bond,

and therefore it was assigned to H(1). All hydrogen atoms were

refined isotropically. Compound 11 was also found to crystallize

with two independent molecules in the asymmetric unit. All

hydrogen atoms were geometrically placed and refined using a

riding model, except for H(2) and H(2B), which were located in

the Fourier maps and refined isotropically. The final refine-

ments on F²proceeded by full-matrix least-squares calculations

in all cases. Further details of the data collection and refine-

ments are given in Table 7.

conveniently modeled, but all the involved atoms were refined

isotropically, as in most cases their temperature factors become

nonpositive definites. All hydrogen atoms were geometrically

placed; they were given an overall isotropic thermal parameter

and were refined using a riding model. Further details of the data

collection and refinements are given in Table 7.

X-ray Structure Determination of Compounds 6a, 6b, and 7a.

Data collection was performed on a Oxford Diffraction Xca-

libur Nova single-crystal diffractometer, using Cu KR radia-

˚

tion (λ = 1.5418 A). Images were collected at a 65 mm fixed

X-ray Structure Determination of Compound 4. Data collec-

tion for compound 4 was performed on a Nonius Kappa CCD

single diffractometer, using graphite-monochromated Mo KR

radiation. Images were collected at a 35 mm fixed crystal-

detector distance, using the oscillation method, with 1° oscilla-

tion and 40 s exposure time per image. Data collection strategy

was calculated with the program Collect.⁴⁹Data reduction and

cell refinement were performed with the programs HKL Denzo

and Scalepack.⁵⁰A semiempirical absorption correction was

applied using the program SORTAV.⁵¹Using the program suite

WinGX,⁴⁶the structure was solved by Patterson interpretation

and phase expansion and refined with full-matrix least-squares

on F²with SHELXL97.⁴⁷All non-hydrogen atoms were refined

anisotropically. During the refinement stages, one cyclohexyl

group was found to be disordered. The disorder could be

crystal-detector distance, using the oscillation method, with

1° oscillation and variable exposure time per image (15-70 s).

Data collection strategy was calculated with the program

CrysAlis Pro CCD.⁵²Data reduction and cell refinement were

performed with the program CrysAlis Pro RED.⁵²An empiri-

cal absorption correction was applied using the SCALE3

ABSPACK algorithm as implemented in the program CrysAlis

Pro RED.⁵²Using the program suite WinGX,⁴⁶the structure

was solved by direct methods using SIR92⁵³(6a and 7a) or by

Patterson interpretation and phase expansion (6b) and refined

with full-matrix least-squares on F²using SHELXL97.⁴⁷Com-

pound 6a was found to crystallize as two independent mole-

cules in the asymmetric unit. During the final stages of the

refinement, all non-H atoms were refined anisotropically and

all hydrogen atoms were geometrically placed and refined

(49) Collect; Nonius B.V.: Delft, The Netherlands, 1997-2004.

(50) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.

(51) Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33.

(52) CrysAlis Pro; Oxford Diffraction Ltd.: Oxford, U.K., 2006.

(53) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Gualardi, A. J.

Appl. Crystallogr. 1993, 26, 343.

Article

Organometallics, Vol. 28, No. 21, 2009 6307

using a riding model. For compound 6b all non-hydrogen

atoms were refined anisotropically and all hydrogen atoms

were fixed at calculated geometric positions and were given an

overall isotropic thermal parameter, although they were loca-

ted in the Fourier map. Compound 7a was found to crystallize

with a molecule of toluene; all atoms of this solvent molecule

were assigned an occupancy factor of 0.5, this providing a

satisfactory refinement. All non-hydrogen atoms were refined

anisotropically. Although all hydrogen atoms were located

in the Fourier map, they were fixed at calculated geometric

positions and were given an overall isotropic thermal

parameter. Further details of the data collection and refine-

ments are given in Table 7.

Acknowledgment. We thank the MEC of Spain for a

grant (to A.R.) and financial support (projects BQU2003-

05471 and CTQ2006-01207/BQU).

Supporting Information Available: CIF file giving the crystal-

lographic data for the structural analysis of compounds 3b, 4,

6a, 6b, 7a C₇H₈, and 11. This material is available free of charge

3

via the Internet at http://pubs.acs.org.

Article Doi

Migration and insertion processes in the reactions of the hydrocarbyl-bridged unsaturated complexes [Mo2(μ5- C5H5)2(μ-R)(μ-PCy2)(CO) 2] (R = Me, CH2Ph, Ph) with CO and

DOI: 10.1021/om9006856

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om9006856

Full text of DOI:10.1021/om9006856

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