Synthesis of [(Me3SiNCH2CH2)3N]3- and [(C6F5NCH2CH2)3N] 3- complexes of molybdenum and tungsten that contain CO, isocyanides, or ethylene

1132

Organometallics 2000, 19, 1132-1149

Syn th esis of [(Me₃SiNCH₂CH₂)₃N]^3-a n d

[(C₆F ₅NCH₂CH₂)₃N]^3-Com p lexes of Molybd en u m a n d

Tu n gsten Th a t Con ta in CO, Isocya n id es, or Eth ylen e

George E. Greco, Myra B. O’Donoghue, Scott W. Seidel, William M. Davis, and

Richard R. Schrock*

Department of Chemistry 6-331, Massachusetts Institute of Technology,

Cambridge, Massachusetts 02139

Received September 23, 1999

Paramagnetic complexes of the type [N₃N]MoL ([N₃N]^3-) [(Me₃SiNCH₂CH₂)₃N]^3-; L )

CO, RNC, C₂H₄) have been prepared by displacing dinitrogen from [N₃N]Mo(N₂). [N₃N]Mo-

(CO) was reduced by magnesium powder in the presence of Me₃SiCl to yield the diamagnetic

oxycarbyne complex [N₃N]MotCOSiMe₃, while oxidation of [N₃N]Mo(CN-t-Bu) with [Cp₂-

Fe]OTf yielded {[N₃N]Mo(CN-t-Bu)}OTf. Thermolysis of [N₃N]Mo(CN-t-Bu) resulted in loss

of a t-Bu radical to yield [N₃N]Mo(CN), which was structurally characterized. [N₃N_F]ML

([N₃N_F]^3-) [(C₆F₅NCH₂CH₂)₃N]^3-; M ) Mo, W; L ) CO, RNC) complexes have been prepared

by one-electron reduction of [N₃N_F]M(OTf) in the presence of L. An X-ray study of [N₃N_F]W-

(CN-t-Bu) showed it to contain a bent isocyanide ligand. Anionic CO complexes were prepared

by the two-electron reduction of [N₃N_F]M(OTf) in the presence of CO. An X-ray study of

{[N₃N_F]W(CO)₂}Na(ether)₃revealed it to have a pseudo-octahedral structure in which sodium

is bound to the CO trans to the amine donor atom. Treatment of {[N₃N_F]M(CO)}^-complexes

with Me₃SiCl gave oxycarbyne complexes [N₃N_F]MtCOSiMe₃. Reaction of [N₃N_F]WCO with

V(Mes)₃(THF) yielded [N₃N_F]W(CO)V(Mes)₃, the structure of which was determined in an

X-ray study. Cationic [N₃N_F]^3-complexes could be prepared that contain up to 3 equiv of

isocyanide. An X-ray study of {[N₃N_F]W(CN-t-Bu)₃}BPh₄showed it to be a seven-coordinate

species with one isocyanide located in the equatorial plane and the other two isocyanide

ligands in the apical pocket. Reduction of [N₃N_F]W(OTf) under ethylene gave [N₃N_F]W(C₂H₄),

which could be oxidized to yield diamagnetic {[N₃N_F]W(C₂H₄)}OTf.

In tr od u ction

three metal bonding orbitals (two π and one σ) within

this pocket. The relatively well-protected nature of the

apical coordination site in [N₃N]^3-([N₃N]^3-) [(Me₃Si-

NCH₂CH₂)₃N]^3-) complexes in particular has allowed

us to isolate unusual complexes such as trigonal-

monopyramidal complexes that contain the first-row

metals from titanium to iron,¹²a tantalum phosphin-

idene complex,¹³and tungsten and molybdenum termi-

nal phosphido and arsenido complexes.⁴The presence

of one σ and two π orbitals is ideal for the formation of

[N₃N]MtE complexes (M ) Mo, W; E ) CR, N, P, As).⁴

Alternatively, the metal center can bind two ligands via

a single and a double bond, as in the alkylidene hydride

complex [N₃N]W(C₅H₈)(H).^8,9The third bonding mode

in which the metal forms single bonds to three ligands

In the last several years a wide variety of transition-

metal complexes that contain a triamidoamine ligand,

[(RNCH₂CH₂)₃N]^3-(R ) C₆F₅,^1,2SiMe₃^3-9), have been

synthesized in our laboratories;¹⁰recently we have been

able to extend this series to ligands in which R is an

ordinary aryl group.¹¹The salient features of such

complexes are the sterically protected, 3-fold-symmetric,

apical coordination site and the spatial arrangement of

(1) Kol, M.; Schrock, R. R.; Kempe, R.; Davis, W. M. J . Am. Chem.

Soc. 1994, 116, 4382.

(2) Seidel, S. W.; Schrock, R. R.; Davis, W. M. Organometallics 1998,

17, 1058.

(3) Verkade, J . G. Acc. Chem. Res. 1993, 26, 483.

(4) Mo¨sch-Zanetti, N. C.; Schrock, R. R.; Davis, W. M.; Wanninger,

K.; Seidel, S. W.; O’Donoghue, M. B. J . Am. Chem. Soc. 1997, 119,

11037.

(5) Schrock, R. R.; Seidel, S. W.; Mo¨sch-Zanetti, N. C.; Shih, K.-Y.;

O’Donoghue, M. B.; Davis, W. M.; Reiff, W. M. J . Am. Chem. Soc. 1997,

119, 11876.

is uncommon, in part for steric reasons, with [N₃N]-

9,14

WH₃

being a rare example. Three-coordinate molyb-

denum triamido complexes are related to triamidoamine

complexes, although they are unique in some respects,

such as their ability to cleave dinitrogen homolytically

to yield Mo(VI) nitrido species.^15,16

(6) O’Donoghue, M. B.; Davis, W. M.; Schrock, R. R. Inorg. Chem.

1998, 37, 5149.

(7) O’Donoghue, M. B.; Davis, W. M.; Schrock, R. R.; Reiff, W. M.

Inorg. Chem. 1999, 38, 243.

(8) Schrock, R. R.; Seidel, S. W.; Mo¨sch-Zanetti, N. C.; Dobbs, D.

A.; Shih, K.-Y.; Davis, W. M. Organometallics 1997, 16, 5195.

(9) Schrock, R. R.; Shih, K.-Y.; Dobbs, D.; Davis, W. M. J . Am. Chem.

Soc. 1995, 117, 6609.

(10) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9.

(11) Greco, G. E.; Popa, A. I.; Schrock, R. R. Organometallics 1998,

17, 5591.

(12) Cummins, C. C.; Lee, J .; Schrock, R. R.; Davis, W. M. Angew.

Chem., Int. Ed. Engl. 1992, 31, 1501.

(13) Cummins, C. C.; Schrock, R. R.; Davis, W. M. Angew. Chem.

1993, 115, 758.

(14) Dobbs, D. A.; Schrock, R. R.; Davis, W. M. Inorg. Chim. Acta

1997, 263, 171.

(15) Cummins, C. C. Prog. Inorg. Chem. 1998, 47, 685-836.

Publication on Web 02/17/2000

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1133

Sch em e 1

One of the original goals of the chemistry of transi-

tion-metal triamidoamine complexes was to understand

how dinitrogen might be activated and reduced in a C₃-

symmetric environment.^1,6,7We now know that {[N₃N]-

Mo(N₂)}^-can be formed readily upon reduction of [N₃N]-

MoCl with excess magnesium and that it can be oxidized

(Scheme 1). Exposure of benzene solutions of [N₃N]Mo-

(N₂) to 1 equiv of CO resulted in a color change from

orange to emerald green over the course of 15 min;

[N₃N]Mo(CO) could be isolated from the reaction as

green needles in 85% yield. When an excess of CO was

used in this reaction, a mixture of [N₃N]Mo(CO) and

[N₃N]MotCOSiMe₃(see below) was formed, along with

to form [N₃N]Mo(N₂).^6,7{[N₃N_F]Mo(N₂)}^-([N₃N_F]^3-

)

[(C₆F₅NCH₂CH₂)₃N]^3-) also can be formed readily,

although [N₃N_F]Mo(N₂) is still unknown. One could

argue that as far as binding dinitrogen and related

ligands is concerned, the [N₃N]Mo and [N₃N_F]W plat-

forms might be approximately the same, the greater

reducing power of W(III) versus Mo(III) being attenu-

ated by the electron-withdrawing ability of the C₆F₅

groups. However, reduction of [N₃N_F]W(OTf) or [N₃N_F]-

WCl under dinitrogen so far has not yielded any

dinitrogen complexes. Therefore, we became interested

in comparing examples of [N₃N]Mo and [N₃N_F]M (M )

Mo, W) complexes that contain other π back-bonding

ligands such as CO, RNC, and ethylene. This type of

organometallic chemistry would be different from that

explored so far, which has been dominated by alkyl,

alkylidene, and alkylidyne complexes of Mo(IV) or

W(IV),^2,5and more relevant to activation and reduction

of dinitrogen. In this paper we report the synthesis of

[N₃N]Mo or [N₃N_F]M (M ) Mo, W) complexes that

contain CO, isonitriles, and ethylene. The chemistry of

[N₃N]W complexes is limited by the low-yield synthesis

of [N₃N]WCl;⁸therefore, similar [N₃N]W chemistry was

not explored.

1

other decomposition products. The H NMR spectrum

of [N₃N]Mo(CO) consists of two broad resonances at

13.17 and -38.04 ppm for the methylene protons in the

[N₃N]^3-backbone (Table 1) and a sharper resonance at

-2.03 ppm, which we assign to the SiMe₃groups. This

1

spectrum is similar to the H NMR spectrum of [N₃N]-

Mo(N₂)⁶and other [N₃N]Mo(L) complexes reported here,

in that one of the backbone methylene resonances is

found downfield of the TMS resonance. In [N₃N]MoCl

and other paramagnetic d²complexes,¹⁰including those

reported here (Table 1), both backbone methylene

resonances are found upfield of 0 ppm.¹⁰

The IR spectrum of [N₃N]Mo(CO) in pentane has a

strong, sharp CO stretch at 1859 cm^-1, which lies

toward the low end of the range of typical stretching

frequencies for neutral, terminal CO complexes.¹⁷The

two peaks found in the IR spectrum of [N₃N]Mo(CO) in

Nujol at 1841 and 1832 cm^-1we believe can be at-

tributed to the presence of two molecules in the unit

cell, a circumstance that also gave rise to two peaks in

the solid-state (Nujol) IR spectrum of [N₃N]Mo(N₂), but

one in solution.⁶SQUID magnetic susceptibility data

for solid [N₃N]Mo(CO) over the temperature range

5-300 K could be fit to the Curie law to give µ ) 1.74-

(1) µ_B(R ) 0.9998), a value that is close to the spin-

only moment for a system containing one unpaired

electron. When a C₆D₆solution of [N₃N]Mo(CO) was

heated to 80 °C for 1 week, the color darkened slightly

and ¹H NMR spectra revealed that ∼10% [N₃N]Mot

COSiMe₃(see below) was present, along with other

unidentified decomposition products.

Resu lts

Syn th esis a n d Rea ctivity of [N₃N]Mo Com p lexes.

Attempts to synthesize [N₃N]Mo(CO) in THF by reduc-

ing [N₃N]MoCl with magnesium powder in the presence

of 1 equiv of CO failed; [N₃N]MoCl was recovered

unchanged. However, [N₃N]Mo(CO) could be accessed

by substituting dinitrogen in [N₃N]Mo(N₂) with CO

(16) Peters, J . C.; Cherry, J .-P.; Thomas, J . C.; Baraldo, L.; Mindiola,

D. J .; Davis, W. M.; Cummins, C. C. J . Am. Chem. Soc. 1999, 121,

10053.

(17) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.

Principles and Applications of Organotransition Metal Chemistry, 2nd

ed.; University Science Books: Mill Valley, CA, 1987.

1134 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

Ta ble 1. IR, Ma gn etic, a n d Selected NMR Da ta for CO, Isocya n id e, a n d Eth ylen e Com p lexes^a

ligand CH₂NMR (ppm)

compd

[N₃N]Mo(CO)

IR^b(cm^-1

)

magnetism^c(µ_Β)

1859 (pentane)

1841, 1832 (N)

1838 (N)

1740 (N)

2147 (THF)

not obsd

1.74 (S)

13.2

-38.0

[N₃N]Mo(CN-t-Bu)

[N₃N]Mo(CNAr)

{[N₃N]Mo(CN-t-Bu)}OTf

[N₃N]Mo(CN)

[N₃N]Mo(C₂H₄)

[N₃N_F]Mo(CO)

{[N₃N_F]Mo(CO)}Na(15-crown-5)

[N₃N_F]W(CO)

{[N₃N_F]W(CO)}Na(15-crown-5)

[N₃N_F]Mo(CN-t-Bu)

[N₃N_F]Mo(CNAr)

1.74 (S)

P

13.4

61.9

-29.4

-25.7

-39.0

-29.8

-98.1

-112.4

2.71 (S)

2.73 (S)

1.73 (S)

2.1 (E)

D

not obsd

1889 (N)

1695 (N)

1846 (N)

1628 (N)

1787 (N)

1777 (N)

1790 (N)

1684 (N)

1679 (N)

2136 (N)

2066 (N)

2184 (N)

12.9

3.73

29.3

3.63

6.6

26.2

5.7

8.0

31.8

-28.1

-27.8

-20.2

-21.0

4.09

4.18

4.06

4.28

-23.9

2.22

-19.2

2.20

2.6 (E)

D

2.4 (E)

2.2 (E)

2.3 (E)

1.74 (S), 2.2 (E)

2.2 (E)

2.8 (E)

3.1 (E)

3.3 (E)

D

-28.2

-22.7

-27.6

-25.8

-25.1

-55.0

-55.2

-80.7

-81.2

3.76

[N₃N_F]Mo(CN-n-Bu)

[N₃N_F]W(CN-t-Bu)

[N₃N_F]W(CNAr)

{[N₃N_F]W(CN-t-Bu)}BAr^F

4

{[N₃N_F]W(CNAr)}BAr^F

4

{[N₃N_F]Mo(CN-t-Bu)}BAr^F

4

{[N₃N_F]Mo(CNAr)}BAr^F

2133 (N)

4

{[N₃N_F]W(CN-t-Bu)₂}OTf

{[N₃N_F]W(CNAr)₂}OTf

[N₃N_F]Mo(CN-t-Bu)₂OTf

[N₃N_F]Mo(CNAr)₂OTf

[N₃N_F]W(CN-t-Bu)₃OTf

[N₃N_F]W(C₂H₄)

2111, 2104 (N)

2096, 2058 (N)

2162, 2136 (N)

2116, 2095 (N)

2178, 2145 (N)

D

3.92

3.65

3.97

complex mutiplet

not obsd

1.8 (E)

D

{[N₃N_F]W(C₂H₄)}OTf

4.42

3.96

a

b

IR: free ArNC, 2115 cm^-1; t-BuNC, 2136 cm^-1; CO, 2143 cm^-1

.

Legend: N ) Nujol. ^cLegend: S ) SQUID; E ) Evans method; D

) diamagnetic; p ) paramagnetic.

When THF solutions of [N₃N]Mo(CO) are stirred over

magnesium powder in the presence of Me₃SiCl, the color

changes from deep green to yellow over the course of

15 min. Diamagnetic [N₃N]MotCOSiMe₃can be iso-

lated from the reaction as pale yellow needles in 91%

yield (Scheme 1). In the absence of Me₃SiCl, two

magnetic, and NMR data listed in Table 1 suggest that

low-spin [N₃N]Mo(CN-t-Bu) is a close relative of [N₃N]-

Mo(CO). [N₃N]Mo(CNAr) (Ar ) 2,6-dimethylphenyl) can

be prepared in an analogous manner.

Ferrocenium triflate reacts smoothly with [N₃N]Mo-

(CN-t-Bu) in THF to give {[N₃N]Mo(CN-t-Bu)}OTf

quantitatively as an orange powder. In the ¹H NMR

spectrum of {[N₃N]Mo(CN-t-Bu)}OTf the resonances for

the methylene protons of the ligand backbone are both

found upfield of the resonance attributed to the TMS

groups of the ligand at 12.83 ppm (Table 1), which is

typical of paramagnetic d²[N₃N]Mo complexes. The

higher CN stretching frequency in {[N₃N]Mo(CN-t-Bu)}-

OTf in THF (2147 cm^-1) reflects the weak π back-

bonding from the cationic d²metal center compared to

that of the d³metal center in [N₃N]Mo(CN-t-Bu) (1838

cm^-1). The proposed high-spin d²configuration of {[N₃N]-

Mo(CN-t-Bu)}OTf is further supported by SQUID mag-

netic susceptibility measurements over the temperature

range 5-300 K, which reveal a behavior analogous to

that observed for [N₃N]MoMe and [N₃N]MoCl (ø ap-

proaches a constant as T approaches 0 K)⁵and which

we now assume to be characteristic of paramagnetic d²

[N₃N]Mo complexes of this general type (Figure 1). The

data can be fit to a Curie-Weiss law (ø ) µ²/8(T - Θ))

over the temperature range 30-300 K to yield a value

of µ ) 2.71(4) µ_Band Θ ) -5(1) K, consistent with two

unpaired electrons being present, presumably in the d_xz

and d_yzorbitals. This type of behavior has been at-

tributed⁵to a combination of spin-orbit coupling and

low-symmetry ligand field components that result in

zero-field splitting of the d²ground-state spin triplet.¹⁸

[N₃N]Mo(CN-t-Bu) proved to be thermally unstable.

When a toluene solution of [N₃N]Mo(CN-t-Bu) was

heated to 86 °C for 36 h, the color changed from orange

1

diamagnetic complexes are observed by H NMR spec-

troscopy that have characteristic resonances for a

diamagnetic [N₃N]^3-complex. They are tentatively

formulated as {[N₃N]Mo(CO)}₂Mg(THF)₂and {[N₃N]-

Mo(CO)}MgCl(THF)₂, the CO analogues of {[N₃N]Mo-

(N₂)}₂Mg(THF)₂and {[N₃N]Mo(N₂)}MgCl(THF)₂,⁶re-

spectively. No attempt was made to isolate these

complexes. They react immediately with Me₃SiCl to give

1

[N₃N]MotCOSiMe₃, according to NMR studies. The H

NMR spectrum of [N₃N]MotCOSiMe₃consists of two

TMS resonances in the ratio of 3:1 and a pair of triplets

for the methylene protons on the ligand backbone. In

the ¹³C NMR spectrum of [N₃N]MotCOSiMe₃the

alkylidyne carbon resonance is found at 208.3 ppm, a

chemical shift that is approximately 90 ppm to higher

field than typically found for alkylidyne complexes of

this type that contain a proton or a carbon substitu-

ent.^2,5No CO stretch could be identified in the IR

spectrum in Nujol.

No reaction is observed between [N₃N]MoCl and

magnesium powder in the presence of 1 equiv of

t-BuNC. Paramagnetic [N₃N]Mo(CN-t-Bu) can be iso-

lated in a reaction in which [N₃N]MoCl is reduced by

Na/Hg amalgam in the presence of t-BuNC, but the

reaction is not clean and [N₃N]Mo(CN-t-Bu) is contami-

nated with [N₃N]MoCl. A clean, high-yield route to

[N₃N]Mo(CN-t-Bu) consists of the reaction between

[N₃N]Mo(N₂) and t-BuNC (Scheme 1). Upon addition of

t-BuNC to a toluene solution of [N₃N]Mo(N₂) the color

changes to deep orange and [N₃N]Mo(CN-t-Bu) can be

isolated as rust-colored needles in 96% yield. The IR,

(18) Figgis, B. N.; Lewis, J . Prog. Inorg. Chem. 1964, 6, 37.

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1135

[16]aneS₄) is also relatively stable toward decomposition

to yield trans-Mo(CN)₂(Me₈[16]aneS₄).²¹

Reduction of [N₃N]MoCl in THF with an excess of

magnesium powder in the presence of 5 equiv of

ethylene proceeds smoothly over a period of 12 h to give

a purple solution that contains paramagnetic [N₃N]Mo-

(C₂H₄) (Scheme 1). The ethylene complex can be isolated

as purple needles in 97% yield upon recrystallization

from hexamethyldisiloxane. Exposing C₆D₆solutions of

orange [N₃N]Mo(N₂) to excess ethylene (10 equiv) also

yielded [N₃N]Mo(C₂H₄) rapidly and cleanly according to

¹H NMR spectra. Unlike other Mo(III) adducts described

so far, resonances for the methylene protons of the

ligand backbone in [N₃N]Mo(C₂H₄) were not observed

1

in its H NMR spectrum; only a single broad resonance

F igu r e 1. Plot of ø_m(corrected for diamagnetism using

Pascal’s constants) versus T for {[N₃N]Mo(CN-t-Bu)}OTf.

was observed at 3.63 ppm (∆ν_1/2) 414 Hz) that we

assign to the TMS groups of the ligand. A resonance

attributable to the ethylene ligand also could not be

observed. Toluene-d₈solutions of [N₃N]Mo(C₂H₄) show

little change after being heated in vacuo at 60 °C for 14

h. However, after a sample was heated to 90 °C in

toluene under 1 atm of dinitrogen for 1 week, the ¹H

NMR spectrum revealed the presence of [N₃N]Mo-Nd

N-Mo[N₃N]⁶and [N₃N]Mo(N₂), along with [N₃N]Mo-

(C₂H₄). Therefore, we presume that [N₃N]Mo(C₂H₄) and

[N₃N]Mo(N₂) are in equilibrium with each other, al-

though the breadth of the TMS resonance in the

spectrum of [N₃N]Mo(C₂H₄) and its coincidental overlap

with the TMS resonance in the spectrum of [N₃N]Mo-

NdN-Mo[N₃N] precluded any accurate estimate of the

extent of its conversion to the dinitrogen complexes. In

any case the equilibrium would appear to be reached

slowly. A SQUID study shows that the magnetic sus-

ceptibility of [N₃N]Mo(C₂H₄) obeys the Curie law be-

tween 5 and 300 K (µ ) 1.73(1) µ_Bwith R ) 0.9999),

consistent with [N₃N]Mo(C₂H₄) being a low-spin Mo(III)

complex.

to yellow. When the thermolysis was carried out in C₆D₆

1

in a sealed NMR tube, H NMR spectra of the crude

reaction mixture revealed three broad, paramagnetically

shifted resonances at 7.73, -25.7, and -112.4 ppm,

characteristic of a new C₃-symmetric complex. Reso-

nances were also observed for isobutylene, isobutane,

and hexamethylethane, products that we propose arise

from the disproportionation and coupling of t-Bu radi-

cals. Yellow, crystalline [N₃N]Mo(CN) could be isolated

from the thermolysis reaction in 88% yield (Scheme 1).

A plot of the molar magnetic susceptibility of [N₃N]Mo-

(CN) versus temperature is characteristic of paramag-

netic d²[N₃N]MoX complexes of this general type. The

data can be fit to the Curie-Weiss law over the

temperature range 30-300 K to give µ ) 2.73(1) µ_Band

Θ ) -7.1(3) Κ. A CN stretch could not be located in the

IR spectrum of [N₃N]Mo(CN). (The IR spectrum of the

analogous tungsten complex¹⁹also lacks an absorption

that could be assigned to the cyanide ligand.)

Oxidation of [N₃N]Mo(C₂H₄) by ferrocenium triflate

Single crystals of [N₃N]Mo(CN) were grown from a

saturated diethyl ether solution at -30 °C and exam-

ined in an X-ray study. Crystallographic data and

collection and refinement parameters are given in Table

2. The molecular structure of [N₃N]Mo(CN) is shown

in Figure 2, while selected bond lengths, bond angles,

and dihedral angles are listed in Table 3. The structure

of [N₃N]Mo(CN) bears a striking resemblance to that

of [N₃N]MoCl.²⁰The Mo-N_amidebond distances are

statistically identical in the two complexes, as are the

Mo-N_axbond distances. The TMS groups also are all

oriented upright in both complexes, as measured by

N_ax-Mo-N_eq-Si dihedral angles close to 180°, indica-

tive of little steric pressure within the pocket. For

comparison, in [N₃N]Mo(OTf) the dihedral angles range

from 136 to 143°, since the TMS groups twist in

response to the sterically bulky triflate ligand within

the pocket.⁵

gave [N₃N]Mo(OTf)⁵as the only identifiable product,

1

according to H NMR spectroscopy. Since ethylene is

somewhat labile in [N₃N]Mo(C₂H₄), we assume that it

is even more labile in hypothetical {[N₃N]Mo(C₂H₄)}⁺

as a consequence of reduced back-bonding from the

cationic d²metal center. Loss of ethylene folowed by

triflate attack at the cationic Mo center then produces

[N₃N]Mo(OTf). This behavior is in contrast with the

result of oxidation of [N₃N_F]W(C₂H₄) with ferrocenium

triflate to give {[N₃N_F]W(C₂H₄)}OTf (vide infra).

Syn th esis a n d Rea ctivity of [N₃N_F]M (M ) Mo,

W) Ca r bon yl Com p lexes. Reduction of [N₃N_F]Mo(OTf)

with 2 equiv of sodium amalgam in the presence of

excess CO gives {[N₃N_F]Mo(CO)}Na(THF)_x(Scheme 2).

The amount of THF in the isolated compound varies

from sample to sample (according to proton NMR

spectra). Addition of 15-crown-5 to a THF solution of

the crude product yields {[N₃N_F]Mo(CO)}Na(15-crown-

5), which can be crystallized from a mixture of toluene

and pentane at -40 °C. The proton, carbon, and fluorine

NMR spectra of {[N₃N_F]Mo(CO)}Na(15-crown-5) are all

consistent with a trigonally symmetric diamagnetic

species. The resonance for the carbonyl carbon is found

at 226.7 ppm in the ¹³C NMR spectrum. Since a CO

Unlike [N₃N]Mo(CN-t-Bu), [N₃N]Mo(CNAr) showed

no evidence of decomposition after a solution had been

heated to 80 °C for 12 h. The greater stability of aryl

isocyanides compared to that of tert-butyl isocyanide

toward decomposition via homolytic N-C bond cleavage

is to be expected. For example, trans-Mo(PhNC)₂(Me₈-

(19) Dobbs, D. A. Unpublished observations.

(20) Duan, Z.; Verkade, J . G. Inorg. Chem. 1995, 34, 1576.

(21) Adachi, T.; Nobuyoshi, S.; Ueda, T.; Kaminaka, M.; Yoshida,

T. J . Chem. Soc., Chem. Commun. 1989, 1320.

1136 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

Ta ble 2. Cr ysta llogr a p h ic Da ta , Collection P a r a m eter s, a n d Refin em en t P a r a m eter s for [N₃N]Mo(CN),

[N₃N_F]W(CO)V(Mes)₃, a n d [N₃N_F]W(CN-t-Bu )^a

[N₃N]Mo(CN)

[N₃N_F]W(CO)V(Mes)₃

[N₃N_F]W(CN-t-Bu)

empirical formula

fw

cryst dimens (mm)

cryst syst

a (Å)

C

₁₈H₄₄N₅O_0.50Si₃Mo

C₅₉H₅₂F₁₅N₄OVW

1352.84

0.12 × 0.12 × 0.10

monoclinic

12.1785(7)

17.3080(10)

26.374(2)

95.6570(10)

5532.2(5)

P2₁/c

C₂₉H₂₁F₁₅N₅W

908.36

518.79

0.37 × 0.32 × 0.23

tetragonal

16.5384(4)

9.8908(3)

90

2705.32(12)

P4h2₁

4

0.21 × 0.14 × 0.08

monoclinic

9.344(4)

27.089(23)

12.237(10)

97.26(5)

3072.8(37)

P2₁/c

b (Å)

c (Å)

â (deg)

V (Å³)

space group

Z

4

D_calcd(Mg/m³)

1.274

0.633

1100

1.624

2.342

2696

1.964

3.881

1756

abs coeff (mm^-1

F₀₀₀

)

temp (K)

183(2)

188 (2)

153(2)

θ range (deg)

1.74-23.23

1.41-20.00

1.50-23.32

no. of rflns collected

no. of indep rflns

R1 (I > 2σ(I))^b

wR2 (I > 2σ(I))^c

R1 (all data)

11 177

15 746

9917

2052

0.0292

0.0842

0.0320

5147

0.1078

0.1955

0.1272

4215

0.0494

0.1103

0.0555

wR2 (all data)

GOF

0.0929

0.936

0.2191

1.400

0.1141

1.216

a

b

All structures were solved on a Siemens SMART/CCD diffractometer using 0.710 73 Å Mo KR radiation. R1 ) ∑||F_o| - |F_c||/∑|F_o|.

2

^cwR2 ) [(∑w(|F_o| - |F_c|)²/∑wF_o)]^1/2

.

resonance for the carbonyl carbon is found at 212.4 ppm

in the ¹³C NMR spectrum, which is between values for

the analogous [N₃N]Mo (208.3 ppm; vide supra) and

[N₃N_F]W (214.1 ppm; vide infra) complexes.

Oxidation of {[N₃N_F]Mo(CO)}Na(15-crown-5) with 1

equiv of ferrocenium tetraphenylborate gives green,

paramagnetic, [N₃N_F]Mo(CO) as the only metal-contain-

ing product (Scheme 2). Only two peaks are observed

in the ¹⁹F NMR spectrum of [N₃N_F]Mo(CO), and the

proton NMR spectrum contains a high-field and a low-

field resonance for the protons on the ligand backbone,

consistent with what is found for the other neutral

M(III) complexes in the present study. (The resonance

for the ortho fluorine appears to be too broad to be

located with confidence.) The CO absorption at 1889

cm^-1is at higher energy than in the analogous [N₃N]-

Mo complex (1845 cm^-1; vide supra) or the [N₃N_F]W

complex (1846 cm^-1; vide infra), consistent with weaker

back-bonding from the metal to CO in [N₃N_F]Mo(CO);

i.e., the C₆F₅ligand renders the metal more electron

poor than the TMS ligand does, and W is a better

reductant than Mo. A magnetic moment of 2.1 µ_B, which

indicates one unpaired electron, was calculated from a

magnetic susceptibility measurement in C₆D₆solution

using the Evans method. If {[N₃N_F]Mo(CO)}Na(15-

crown-5) is oxidized with ferrocenium triflate, instead

of ferrocenium tetraphenylborate, [N₃N_F]Mo(OTf) is the

only compound that could be identified. We propose that

it is produced by a two-electron oxidation of the metal

and displacement of CO by triflate in the intermediate

{[N₃N_F]Mo(CO)}OTf.

F igu r e 2. ORTEP drawing of [N₃N]Mo(CN).

Ta ble 3. Selected Bon d Len gth s (Å) a n d Bon d

An gles (d eg) for [N₃N]Mo(CN)

Bond Lengths (Å)

Mo-N(1)

Mo-N(2)

Mo-N(4)

1.980(5)

1.970(3)

2.210(5)

Mo-C(7)

C(7)-N(5)

2.182(6)

1.113(8)

Bond Angles (deg)

Mo-N(2)-Si(1)

Mo-N(1)-Si(2)

N(2)-Mo-N(2A)

N(1)-Mo-N(2)

128.1(2)

128.3(3)

115.6(2)

118.53(11)

N(1)-Mo-N(4)

Mo-C(7)-N(5)

C(7)-Mo-N(4)

N(2)-Mo-N(4)

80.9(2)

179.8(6)

179.1(2)

80.92(12)

Dihedral Angles (deg)^a

N(4)-Mo-N(2)-Si(1) 179.1 N(4)-Mo-N(1)-Si(2) 180.0

a

Obtained from a Chem 3D model.

stretch is observed at 1695 cm^-1in the IR spectrum in

Nujol, sodium cannot be bound so strongly to oxygen

as to justify a description of this species as an oxycar-

byne derivative, i.e., [N₃N_F]MotCONa(15-crown-5).

Addition of trimethylchlorosilane to {[N₃N_F]Mo(CO)}-

Na(THF)_xresults in immediate bleaching of the orange

color and formation of what can be described as [N₃N_F]-

MotCOSiMe₃(Scheme 2). The colorless product can be

isolated in 50% yield by recrystallization from ether. The

[N₃N_F]W(OTf) reacts with 1 equiv of 0.5% sodium

amalgam under carbon monoxide to yield [N₃N_F]W(CO)

as a paramagnetic red crystalline solid in high yield

(Scheme 2). Only the meta and para fluorines can be

observed in the ¹⁹F NMR spectrum as broad resonances

at -132.1 and -170.5 ppm. [N₃N_F]W(CO) is always

contaminated with a trace (<5% by NMR) of a diamag-

netic impurity, although the presence of this impurity

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1137

Sch em e 2

did not prevent successful C, H, and N analyses. A ¹³

C

plane in {[N₃N_F]W(CO)₂}Na(THF)_xand a pseudo-

NMR study of the diamagnetic impurity present in a

sample of [N₃N_F]W(¹³CO) revealed a sharp resonance

at 205.1 ppm, which displayed tungsten satellite peaks

(J _CW) 131 Hz). In the proton-coupled spectrum this

peak splits into a doublet with J _CH) 7.5 Hz. Therefore,

we propose that the diamagnetic impurity is either a

carbonyl hydride complex, [N₃N_F]W(CO)(H), analogous

to crystallographically characterized [N₃N]W(CO)(H), in

which δ(C_R) ) 209 ppm and J _CW) 133 Hz,⁸or [N₃N_F]Wt

COH, analogous to [N₃N_F]WtCOSiMe₃described below,

in which δ(C_R) ) 216.9 ppm. The origin of the hydrogen

atom is not known. No reaction was observed when

[N₃N_F]WCl was stirred with Na/Hg under CO.

Reaction of [N₃N_F]W(OTf) with 2 equiv of sodium

amalgam in the presence of an excess of CO yields an

intensely purple solution. When the solution is exposed

to vacuum, the color changes to red and, ultimately, to

yellow. Proton, carbon, and fluorine NMR spectra sug-

gest that the yellow diamagnetic product is {[N₃N_F]W-

(CO)}Na(THF)_x, a stable crystalline derivative of which

can be prepared by adding 15-crown-5 to it. The

resonance for the carbonyl carbon occurs at 224.2 ppm

(J _CW) 270 Hz) in the ¹³C NMR spectrum of ¹³C-labeled

{[N₃N_F]W(CO)}Na(15-crown-5) (cf. 226.7 ppm in {[N₃N_F]-

Mo(CO)}Na(15-crown-5)). The IR spectrum of {[N₃N_F]W-

(CO)}Na(15-crown-5) contains a single CO stretching

band at 1628 cm^-1(cf. 1695 cm^-1in the analogous Mo

complex), which shifts to 1592 cm^-1in ¹³C-labeled

material, again consistent with the expected greater

reducing power of tungsten compared to molybdenum.

We were interested in determining the identity of the

purple material formed upon initial reduction of [N₃N_F]-

W(OTf) in the presence of CO. The purple solution

maintains its color indefinitely at room temperature in

the presence of CO, or at -40 °C in the drybox freezer

(under nitrogen). Since the anionic monocarbonyl com-

plex can be isolated upon exposure of the purple solution

to vacuum, we proposed that the purple material is

{[N₃N_F]W(CO)₂}Na(THF)_x. This hypothesis is supported

by the fact that exposing a solution of {[N₃N_F]W(CO)}-

Na(THF)_xto CO (after removing dinitrogen from solu-

tion via the freeze-pump-thaw method) results in the

reappearance of the purple color. The ¹⁹F NMR spec-

trum shows a 2:1 ratio of all three types of fluorine in

the molecule, consistent with the presence of a mirror

octahedral coordination environment around tungsten.

When the reduction of [N₃N_F]W(OTf) was carried out

under ¹³CO, two peaks were observed in the ¹³C NMR

spectrum of the purple product at 246.2 ppm (J _WC

)

112 Hz) and 242.4 ppm (J _WC) 215 Hz). IR spectra in

THF of both labeled and unlabeled material showed two

very broad CO stretches. The stretches are centered at

1952 and 1726 cm^-1in unlabeled material; they move

to 1895 and 1682 cm^-1in ¹³C-labeled material. If the

reduction of [N₃N_F]W(OTf) is carried out in ether

instead of THF, and the crude reaction mixture is cooled

to -40 °C under nitrogen, single crystals of {[N₃N_F]W-

(CO)₂}Na(ether)₃may be obtained. Dissolving the crys-

tals in any solvent which is not saturated with CO

resulted in formation of {[N₃N_F]W(CO)}Na(ether)_x. An

IR spectrum obtained in Nujol contained two sharp

peaks at 1926 and 1716 cm^-1, which is consistent with

the IR spectrum obtained in THF solution. All data are

consistent with one CO being bound relatively strongly

to tungsten and the other being labile.

A single crystal of {[N₃N_F]W(CO)₂}Na(ether)₃was

studied by X-ray diffraction. Crystallographic data and

collection and refinement parameters are given in Table

4. A view of the structure along with the atom-labeling

scheme is shown in Figure 3, while selected bond

lengths, bond angles, and dihedral angles are listed in

Table 5. The carbonyl ligand trans to N(4) has sodium

bound to it. The C(1)-O(1) bond length (1.21 Å) and a

W-C(1) bond length (1.89 Å) suggest that the anionic

charge is localized on this CO. We believe that the

relatively large J _CW(215 Hz) in the ¹³C NMR spectrum

of {[N₃N_F]W(CO)₂}Na(THF)_x(vide supra) is found for

the R-carbon atom in the more “reduced” CO ligand that

has sodium bound to it. The C(2)-O(2) bond length of

1.16 Å and a W-C(2) distance of 2.06 Å are more

consistent with a “normal” CO. On the basis of the bond

length in gaseous CO (1.128 Å)²²and typical values for

C-O single and double bonds (1.42 and 1.22 Å, respec-

tively),²³the C(1)-O(1) bond order is close to 2, while

the C(2)-O(2) bond order is between 2 and 3.

(22) Greenwood, N. N.; Earnshaw, A. Chemistry of the Elements;

University Press: Cambridge, England, 1984.

(23) Carey, F. A.; Sundberg, R. J . Advanced Organic Chemistry A;

Plenum Press: New York, 1990.

1138 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

Ta ble 5. Selected Bon d Len gth s, An gles, a n d

Ta ble 4. Cr ysta llogr a p h ic Da ta , Collection

P a r a m eter s, a n d Refin em en t P a r a m eter s for

{[N₃N_F]W(CO)₂}[Na (eth er )₃] a n d

Dih ed r a l An gles for {[N₃N_F]W(CO)₂}Na (eth er )₃

Bond Lengths (Å)

a

{[N₃N_F]W(CN-t-Bu )₃}BP h ₄

W-C(1)

W-C(2)

W-N(1)

W-N(2)

W-N(3)

1.889(9)

2.057(10)

2.136(6)

2.077(6)

2.040(6)

W-N(4)

2.286(6)

1.207(9)

2.224(6)

1.159(10)

C(1)-O(1)

O(1)-Na

C(2)-O(2)

{[N₃N_F]W(CO)₂}-

[Na(ether)₃]

{[N₃N_F]W(CN-

t-Bu)₃}BPh₄

empirical formula

fw

cryst dimens (mm)

cryst syst

a (Å)

C₃₈H₄₂F₁₅N₄NaO₅W C₇₅H₈₃BF₁₅N₇O₃W

1126.60

0.1 × 0.1 × 0.24

triclinic

11.4786(12)

11.7106(12)

19.202(2)

80.697(2)

74.554(2)

63.0820(10)

2215.8(4)

P1h

1610.14

0.6 × 0.6 × 0.6

monoclinic

11.6756(2)

24.3939(2)

25.9702(5)

90

91.792(1)

90

7393.0(2)

P2₁/c

Bond Angles (deg)

C(1)-W-C(2)

C(1)-W-N(1)

C(1)-W-N(2)

C(1)-W-N(3)

C(1)-W-N(4)

C(2)-W-N(1)

C(2)-W-N(2)

C(2)-W-N(3)

C(2)-W-N(4)

N(1)-W-N(2)

N(1)-W-N(3)

76.0(3)

105.1(3)

99.2(3)

100.5(3)

175.3(3)

76.0(3)

168.8(3)

81.8(3)

108.6(3)

95.9(2)

N(1)-W-N(4)

N(2)-W-N(3)

N(2)-W-N(4)

N(3)-W-N(4)

W-N(1)-C(3)

W-N(2)-C(11)

W-N(3)-C(19)

C(1)-O(1)-Na

W-C(1)-O(1)

W-C(2)-O(2)

77.5(2)

109.2(3)

76.4(2)

b (Å)

c (Å)

79.3(2)

R (deg)

123.3(5)

125.9(5)

124.7(5)

172.3(6)

179.1(7)

171.8(7)

â (deg)

γ (deg)

V (Å³)

space group

Z

2

4

D_calcd(Mg/m³)

abs coeff (mm^-1)

F₀₀₀

1.689

1.447

140.5(2)

2.725

1.652

Dihedral Angles (deg)

N(4)-W-N(1)-C(3) 173.8(6) N(4)-W-N(3)-C(19) 151.4(6)

N(4)-W-N(2)-C(11) 172.2(6)

1116

3280

temp (K)

θ range (deg)

177(2)

1.10-23.27

no. of rflns collected 9266

183(2)

2.07-23.24

29 930

no. of indep rflns

6264

(R(int) ) 0.0386)

0.0449

0.1023

0.0597

0.1122

1.129

10 559

(R(int) ) 0.0279)

0.0327

0.0659

0.0355

0.0669

1.221

varying in length from 2.04 to 2.14 Å. In structurally

characterized group 6 complexes with C₃symmetry,

M-N_eqbond lengths are all ∼1.97 Å (( 0.02 Å). The

long and unequal W-N_eqbond lengths in {[N₃N_F]W-

(CO)₂}Na(ether)₃can be ascribed in part to steric

crowding at the six-coordinate metal center.

R1 (I > 2σ(I))^b

wR2 (I > 2σ(I))^c

R1 (all data)

wR2 (all data)

GOF

a

All structures were solved on a Siemens SMART/CCD diffrac-

When a THF solution of [N₃N_F]W(CO) is stirred over

1 equiv of sodium amalgam for 1 h, and Me₃SiCl is then

added, brown, crystalline, diamagnetic [N₃N_F]Wt

COSiMe₃can be isolated in good yield (Scheme 2). The

¹³C NMR spectrum of [N₃N_F]WtCOSiMe₃shows a

resonance characteristic of an alkylidyne carbon atom

at 216.9 ppm. For comparison the alkylidyne carbon

atom resonance is found at 214.1 ppm in [N₃N]Wt

COSiMe₃.¹⁴

b

tometer using 0.717 03 Å Mo KR radiation. R1 ) ∑||F_o| - |F_c||/

∑|F_o|. ^cwR2 ) [(∑w(|F_o| - |F_c|)²/∑wF_o)]^1/2

.

2

[N₃N_F]W(CO) reacts with V(Mes)₃(THF)²⁴in toluene

at room temperature to yield [N₃N_F]W(CO)V(Mes)₃in

high yield as a black crystalline solid. The effective

magnetic moment of [N₃N_F]W(CO)V(Mes)₃at 22 °C was

found to be 2.1 ( 0.1 µ_Bby the Evans method. Broad-

ened and slightly shifted ¹H NMR resonances for the

mesityl rings are observed at 17.5, 16.2, and 6.6 ppm,

while resonances for the [N₃N_F]W half of the molecule

are located at the normal diamagnetic positions. There-

fore, the paramagnetism can be ascribed to the vana-

dium center in [N₃N_F]W(CO)V(Mes)₃. No ¹³C resonance

for the CO ligand could be observed in [N₃N_F]W(¹³CO)V-

(Mes)₃, and no band that can be assigned to the C-O

stretch could be identified in the IR spectrum.

F igu r e 3. ORTEP drawing of {[N₃N_F]W(CO)₂}Na(ether)₃.

Crystals of [N₃N_F]W(CO)V(Mes)₃suitable for X-ray

diffraction were obtained from toluene at -40 °C. Views

of the structure are shown in Figure 4. Crystallographic

data can be found in Table 2 and selected interatomic

distances and angles in Table 6. The structure is not of

high quality (only W, V, O, N, and F atoms were refined

anisotropically); therefore, errors are too large to discuss

bond lengths and angles in detail. A description of this

complex as a “vanadoxyalkylidyne” complex, [N₃N_F]Wt

COV(Mes)₃, would appear to be justified on the basis of

the W-C(1) bond length of 1.88(2) Å and chemical shifts

The coordination environment around tungsten is

pseudo-octahedral, with the N(2)-W-N(3) and N(1)-

W-N(2) angles reduced to 96 and 109°, respectively,

compared to analogous angles close to 120° in trigonally

symmetric complexes such as [N₃N_F]W(CN-t-Bu) (vide

infra). The C(2)-W-N(1) angle is 76°, and the C(2)-

W-N(3) angle is 81°. The neutral CO ligand (C(2)-O(2))

is pointed slightly up from the N(1)/N(2)/N(3) plane,

with the C(1)-W-C(2) bond angle being 76° and the

N(4)-W-C(2) angle being 109°. Also of interest is the

fact that the W-N_eqbond lengths are all over 2 Å,

(24) Seidel, W.; Kreisel, G. Z. Anorg. Allg. Chem. 1977, 435, 146.

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1139

Ta ble 6. Selected In ter a tom ic Dista n ces (Å) a n d

An gles (d eg) for [N₃N_F]W(CO)V(Mes)₃a n d

[N₃N_F]W(CN-t-Bu )

[N₃N_F]W(CO)V(Mes)₃

[N₃N_F]W(CN-t-Bu)

W-C(1)

1.88(2)

1.98(2)

1.95(2)

2.31(2)

1.19(2)

W-C(7)

1.913(11)

1.975(8)

1.967(8)

1.980(8)

2.243(8)

1.249(14)

1.420(15)

W-N(1)

W-N(2)

W-N(3)

W-N(4)

O-C(1)

V-O

W-N(1)

W-N(2)

W-N(3)

W-N(4)

C(7)-N(5)

1.824(14) N(5)-C(8)

W-N(1)-C(11)

W-N(2)-C(21)

W-N(3)-C(31)

N(3)-W-N(1)

N(2)-W-N(3)

N(2)-W-N(1)

N(4)-W-N(3)

N(3)-W-C(1)

N(2)-W-C(1)

W-C(1)-O

126.6(13) W-N(1)-C(11)

124.9(13) W-N(2)-C(21)

127.4(13) W-N(3)-C(31)

127.9(6)

124.4(7)

125.5(6)

117.5(3)

117.8(3)

114.7(3)

79.7(3)

100.8(4)

99.4(3)

172.1(8)

132.2(10)

116.4(7)

118.4(7)

114.9(7)

80.1(8)

101.0(8)

99.8(8)

178(2)

N(3)-W-N(1)

N(2)-W-N(3)

N(2)-W-N(1)

N(4)-W-N(3)

N(3)-W-C(7)

N(2)-W-C(7)

W-C(7)-N(5)

C(7)-N(5)-C(8)

C(1)-O-V

176(2)

N(4)-W-N(2)-C(21) 176^a

N(4)-W-N(1)-C(11) 179^a

N(4)-W-N(3)-C(31) 178^a

N(4)-W-N(2)-C(21) 169^a

N(4)-W-N(1)-C(11) 179^a

N(4)-W-N(3)-C(31) 173^a

V-C(41)

2.05(2)

V-C(51)

2.03(2)

2.05(2)

3.55^a

V-C(61)

C(14)-C(43)

C(34)-C(55)

C(24)-C(63)

C(33)-C(55)

3.32^a

3.41^a

3.64^a

a

Obtained from a Chem 3D model.

for the ligand protons in the proton NMR spectrum and

C₆F₅fluorines in the ¹⁹F NMR spectra that are char-

acteristic of diamagnetic compounds, as noted above.

The metrical parameters for the triamidoamine side of

the molecule are all typical of triamidoamine molecules

in which there is little steric strain; i.e., the N(4)-W-

N_eq-C₆F₅dihedral angles are all close to 180°. The

mesityl rings on vanadium adopt a propeller-like ori-

entation, possibly in order to minimize steric interac-

tions between the ortho methyl groups present on the

rings. The V-O distance of 1.824(14) Å is similar to that

observed for some vanadium alkoxides,²⁵and the ge-

ometry at the vanadium center is nearly tetrahedral.

As a point of reference the VdO bond length in

(Mes)₃VdO was found to be 1.575(4) Å.²⁶Both the

W-C(1)-O and V-O-C(1) angles are close to 180°. The

mesityl rings are roughly eclipsed with the C₆F₅rings,

although they do not lie perfectly parallel to one other

(Figure 4b). Distances between the mesityl ring carbons

and the C₆F₅ring carbons that range from 3.3 to 3.5 Å

suggest that there is some degree of interaction between

the mesityl and pentafluorophenyl rings.^27-29

F igu r e 4. (a, top) ORTEP drawing of [N₃N_F]W(CO)V-

(Mes)₃. (b, bottom) Top view (Chem 3D) of [N₃N_F]W(CO)V-

(Mes)₃.

isocyanide (Scheme 3; Table 1). All complexes are orange

paramagnetic crystalline solids. We have also shown

that [N₃N_F]W(CN-t-Bu) can be formed by employing

[N₃N_F]WCl and 1 equiv of sodium amalgam in the

presence of tert-butyl isocyanide. The meta fluorine

resonances are found near -160 ppm in the ¹⁹F NMR

spectra, which is about 35 ppm upfield of where they

are found in neutral d²complexes such as [N₃N_F]WCl.

Infrared absorptions that can be attributed to an

isocyanide stretch are observed at unusually low ener-

gies for a coordinated isocyanide ligand,³⁰consistent

with extensive π back-bonding into the isocyanide

ligand. The isocyanide stretch is found at lower energies

for the W compounds, as expected. [N₃N_F]W(CN-t-Bu)

is also always contaminated with a trace (<5% by NMR)

of a diamagnetic impurity, although the presence of this

impurity did not prevent successful C, H, and N

analysis. The nature of this impurity is not known. A

SQUID measurement on [N₃N_F]W(CN-t-Bu) revealed

that it is a one-electron Curie magnet down to 5 K (µ )

1.74 µ_B), as found for [N₃N]Mo(CN-t-Bu). Solution

magnetic susceptibility measurements using the Evans

method yielded magnetic moments ranging from 2.2 to

Syn th esis a n d Rea ctivity of Neu tr a l [N₃N_F]M (M

) Mo, W) a n d Ca t ion ic Isocya n id e Com p lexes.

Complexes that contain one t-BuNC or ArNC (Ar ) 2,6-

dimethylphenyl) can be prepared by reducing [N₃N_F]M-

(OTf) complexes (M ) Mo, W) in the presence of the

(25) Carrano, C. J .; Mohan, M.; Holmes, S. M.; de la Rosa, R.; Butler,

A.; Charnock, J . M.; Garner, C. D. Inorg. Chem. 1994, 33, 646.

(26) Vivanco, M.; Ruiz, J .; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.

Organometallics 1993, 12, 1802.

(27) Williams, J . H. Acc. Chem. Res. 1993, 26, 593.

(28) Dahl, T. Acta Chem. Scand. 1994, 48, 95.

(29) Coates, G. W.; Dunn, A. R.; Henling, L. M.; Dougherty, D. A.;

Grubbs, R. H. Angew. Chem., Int. Ed. Engl. 1997, 36, 248.

(30) Malatesta, L.; Bonati, F. Isocyanide Complexes of Metals;

Wiley: New York, 1969; Vol. IV.

1140 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

Sch em e 3

2.4 µ_Bfor the four isocyanide complexes, all of which

are in the proper range for one unpaired electron.

A single-crystal X-ray study of [N₃N_F]W(CN-t-Bu)

revealed it to have the structure shown in Figure 5.

Crystallographic data can be found in Table 2 and

selected interatomic distances and angles in Table 6.

The metrical parameters for the triamidoamine side of

the molecule are all typical for complexes of this type

and consistent with little steric strain in the complex

that results from crowding within the trigonal pocket.

For example, the N(4)-W-N_eq-C angles are 169, 179,

and 173°, and the N_eq-W-N_eq′ angles are 117, 118, and

115°. The tert-butyl group is tipped away from the C₆F₅

ring attached to N(2) and between the other two C₆F₅

rings. The W-C(7) distance (1.913(11) Å), the C(7)-N(5)

distance (1.249(14) Å), and the C(7)-N(5)-C(8) angle

(132.2(10)°) are all more consistent with a W(V) “aza-

vinylidene” description, i.e., [N₃N_F]WdCdN-t-Bu, than

with an isocyanide complex of W(III). The azavinylidene

description is also consistent with the presence of one

unpaired electron, as noted above. The relative stability

of [N₃N_F]W(CN-t-Bu) toward loss of a tert-butyl radical

should be compared with the formation of [N₃N]Mo(CN)

upon heating [N₃N]Mo(CN-t-Bu).

Reduction of [N₃N_F]MoCl by sodium amalgam in the

presence of n-butyl isocyanide yields red, crystalline

[N₃N_F]Mo(CN-n-Bu) in good yield (Table 1). A trace of

diamagnetic material is present in spectra of [N₃N_F]Mo-

(CN-n-Bu), although its presence did not prevent suc-

cessful C, H, and N analyses. The CN absorptions in

all three [N₃N_F]Mo(CNR) (R ) t-Bu, Ar, n-Bu) com-

plexes are found between 1777 and 1790 cm^-1in Nujol.

Comparison with the CN stretching frequency in [N₃N]-

Mo(CNAr) (1740 cm^-1in Nujol) suggests that the

[N₃N_F]^3-ligand overall leads to less back-bonding to a

π acceptor ligand than [N₃N]^3-ligand, as one might

expect.

Oxidation of [N₃N_F]M(CNR) compounds with [Cp₂Fe]-

BAr^F(Ar^F) 3,5-(CF₃)₂C₆H₃) in CH₂Cl₂produced

4

paramagnetic monocations in high yields (Scheme 3;

1

Table 1). Resonances in the H and ¹⁹F NMR spectra of

these compounds are considerably broader than those

for [N₃N_F]M(CNR) compounds, and no resonance for

ortho fluorines is visible in ¹⁹F NMR spectra. NMR

resonances are much sharper in the spectra of tungsten

complexes than in the spectra of molybdenum com-

plexes, as is routinely the case.^2,5,8The isocyanide

absorptions in the IR spectra of all four cations are

found near the absorption for free isocyanide, indicating

little back-bonding from the cationic metal centers.

Solution magnetic susceptibility measurements (Evans

method) yielded magnetic moments ranging from 2.8 to

3.3 µ_Bfor the four cations, all of which are in the proper

range for two unpaired electrons. Magnetic data are

consistent with a description as d²M(IV) complexes

rather than d⁰M(VI) azavinylidene complexes. Similar

compounds are obtained if the oxidation is performed

with [Cp₂Fe]BPh₄, although the solubility of these

complexes in common organic solvents is too low to

permit full characterization.

Oxidation of [N₃N_F]W(CN-t-Bu) with ferrocenium

triflate affords a THF-soluble, diamagnetic species in

50% yield that we formulate as {[N₃N_F]W(CN-t-Bu)₂}-

OTf on the basis of spectroscopic and analytical data.

The remaining 50% of the tungsten is found in the form

of relatively insoluble [N₃N_F]W(OTf). Proton, carbon,

and fluorine NMR spectra suggest that {[N₃N_F]W(CN-

t-Bu)₂}OTf has C₃symmetry (equivalent isocyanide

groups). The isocyanide carbon resonance in the ¹³C

NMR spectrum is found at 157.3 ppm, which is 3 ppm

downfield of free isocyanide.³¹We speculate that this

product is a six-coordinate cation in which the trigonal

symmetry of the ligand core is maintained and that the

two isocyanides equilibrate on the NMR time scale

without dissociating from the metal. Two stretches are

When [N₃N_F]WCl is treated with sodium amalgam in

the presence of n-butyl isocyanide under conditions

identical with those used to synthesize [N₃N_F]Mo(CN-

n-Bu), a paramagnetic species can be observed by ¹⁹F

NMR after ∼1 h, whose ¹⁹F chemical shifts and peak

widths are similar to those observed for [N₃N_F]Mo(CN-

n-Bu). Therefore, we propose that [N₃N_F]W(CN-n-Bu)

is present at this point. However, attempts to isolate

and purify this product by recrystallization from dichlo-

romethane led to increasing contamination with one or

more diamagnetic impurities. So far we have not been

able to isolate [N₃N_F]W(CN-n-Bu) in pure form.

found in the IR spectrum at 2111 and 2104 cm^-1

.

Oxidation of [N₃N_F]W(CNAr) with ferrocenium triflate

affords a 1:1 mixture of {[N₃N_F]W(CNAr)₂}OTf and

[N₃N_F]W(OTf) in a completely analogous fashion. The

isocyanide carbon resonance in the ¹³C NMR spectrum

of {[N₃N_F]W(CNAr)₂}OTf is found at 174.7 ppm, 4 ppm

downfield of free isocyanide.³¹The diamagnetic nature

of {[N₃N_F]W(CNR)₂}OTf species can be attributed to

(31) Caro, C. F.; Hitchcock, P. B.; Lappert, M. F.; Layh, M. Chem.

Commun. 1998, 1297.

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1141

reactions involving loss of isocyanide, at least under

mild conditions (22 °C), and {[N₃N_F]Mo(CNR)₂}BAr^F

4

complexes are stable as a consequence of the poor

-

coordinating ability and large size of the BAr^F

ion.

4

The NMR spectra of {[N₃N_F]Mo(CNR)₂}OTf are com-

plicated by behavior involving formation of {[N₃N_F]Mo-

(CNR)}OTf and {[N₃N_F]Mo(OTf), as mentioned above,

especially at temperatures below 0 °C where [N₃N_F]Mo-

(OTf) crystallizes out, as is readily ascertained by visual

inspection. At temperatures above 20 °C, a resonance

for only one type of isocyanide is observed. If free

isocyanide is added to the sample, the single resonance

shifts downfield, closer to that of free isocyanide, sug-

gesting rapid exchange of free and coordinated isocya-

nide. It should be noted that the resonances in the

spectra are broadened by the paramagnetism of {[N₃N_F]-

Mo(CNR)}OTf and (to a lesser extent if it has crystal-

lized out of the sample) [N₃N_F]Mo(OTf). There are small

differences between ArNC and t-BuNC complexes that

can be traced to differences in basicity and steric bulk.

F igu r e 5. ORTEP drawing of [N₃N_F]W(CN-t-Bu).

formation of a pseudooctahedral species in which the

d_xzand d_yzorbitals are no longer degenerate. NMR

spectra in CDCl₃down to -60 °C show that the

isocyanide ligands remain apparently equivalent, al-

though the remainder of the spectrum is consistent with

the known^2,5,8,32“locking” of the backbone of the [N₃N_F]^3-

ligand in one C₁conformation.

1

For example, in H NMR spectra of {[N₃N_F]Mo(CNAr)₂}-

OTf, resonances for free and bound ArNC are observed

below 0 °C. The reason, we propose, is that the equi-

librium between {[N₃N_F]Mo(CNAr)₂}OTf and [N₃N_F]Mo-

(OTf) plus free ArNC is shifted further to the right for

the more poorly coordinating ArNC and the rate of

ArNC exchange is slow on the NMR time scale. In

contrast, only one broad tert-butyl resonance can be

We believe that the initial product of the oxidation of

[N₃N_F]W(CN-t-Bu) with [Cp₂Fe]OTf is {[N₃N_F]W(CN-

t-Bu)}OTf, by analogy with {[N₃N_F]W(CN-t-Bu)}BAr^F

.

1

4

observed in the H NMR spectrum of {[N₃N_F]Mo(CN-

t-Bu)₂}OTf down to -60 °C. Although a ¹³C NMR

spectrum can be obtained for {[N₃N_F]Mo(CN-t-Bu)₂}-

OTf at 0 °C, no isocyanide carbon resonance can be

observed. Both {[N₃N_F]Mo(CNR)₂}OTf compounds can

be recrystallized from dichloromethane in the presence

of excess isocyanide to give analytically pure material.

Solid-state IR spectra (Nujol) of the recrystallized

material indicates the presence of two isocyanide reso-

nances, analogous to those observed in the correspond-

ing (stable) W complexes. Resonances in NMR spectra

However, the metal center in {[N₃N_F]W(CN-t-Bu)}OTf

must be attacked by triflate and the isocyanide lost to

yield [N₃N_F]W(OTf). The free isocyanide then captures

the remaining {[N₃N_F]W(CN-t-Bu)}OTf, producing the

50% yield of {[N₃N_F]W(CN-t-Bu)₂}OTf, from which the

isocyanide is not lost readily (Scheme 3). This proposal

is supported by the finding that {[N₃N_F]W(CNR)₂}⁺

complexes can be prepared straightforwardly by treating

[N₃N_F]W(OTf) with 2 equiv of isocyanide in THF. Yields

in excess of 80% are obtained within a few minutes.

Diamagnetic {[N₃N_F]W(CNR)₂}BAr^Fcomplexes can

of {[N₃N_F]Mo(CNR)₂}BAr^Fcomplexes are broad, as a

4

be prepared by addition of 1 equiv of the appropriate

consequence of formation of a small amount of para-

isocyanide to {[N₃N_F]W(CNR)}BAr^F(Scheme 3). The

magnetic {[N₃N_F]Mo(CNR)}BAr^F

.

4

¹H and ¹⁹F NMR spectra, and the position of the CN

stretches in the IR spectrum of {[N₃N_F]W(CNAr)₂}-

BAr^F₄, for example, are similar to those of {[N₃N_F]W-

(CNAr)₂}OTf.

The low-temperature spectrum of {[N₃N_F]Mo(CN-t-

Bu)₂}OTf in the presence of added t-BuNC shows new

features that suggest that yet another compound is

being formed reversibly. On the basis of NMR reso-

nances analogous to those found for {[N₃N_F]W(CN-t-

Bu)₃}OTf (vide infra), we propose that {[N₃N_F]Mo(CN-

t-Bu)₃}OTf is being formed at low temperatures.

Predictably, it is more unstable toward loss of isocyanide

than is {[N₃N_F]W(CN-t-Bu)₃}OTf. {[N₃N_F]Mo(CNAr)₃}-

OTf apparently does not form as readily as {[N₃N_F]Mo-

(CN-t-Bu)₃}OTf as a consequence of the poorer basicity

of ArNC relative to t-BuNC.

Oxidation of [N₃N_F]Mo(CN-t-Bu) or [N₃N_F]Mo(CNAr)

with ferrocenium triflate yielded only [N₃N_F]Mo(OTf),

in 81% and 88% yield, respectively. {[N₃N_F]Mo(CNR)₂}-

OTf complexes can be prepared by adding isocyanide

to [N₃N_F]Mo(OTf), but at least 3 equiv of isocyanide is

required before all of the insoluble [N₃N_F]Mo(OTf)

disappears. After THF is removed and the residue is

redissolved in dichloromethane, insoluble [N₃N_F]Mo-

(OTf) forms again but disappears upon addition of more

isocyanide. Isolated yields of the {[N₃N_F]Mo(CNR)₂}OTf

complexes are only about 60%. These data are consistent

with a high lability of the second equivalent of isocya-

nide in {[N₃N_F]Mo(CNR)₂}OTf and decomposition of

{[N₃N_F]Mo(CNR)}OTf to yield free isocyanide and in-

soluble [N₃N_F]Mo(OTf) (Scheme 3). In contrast, as noted

above, {[N₃N_F]W(CNR)₂}OTf complexes are stable to

Treatment of [N₃N_F]W(OTf) with 3 equiv or more of

tert-butyl isocyanide yields diamagnetic, emerald green

{[N₃N_F]W(CN-t-Bu)₃}OTf, a composition we propose on

the basis of its similarity to a structurally characterized

1

tetraphenylborate derivative described below. The H,

¹³C, and ¹⁹F NMR spectra of {[N₃N_F]W(CN-t-Bu)₃}OTf

are all indicative of it not being C₃symmetric. Two

resonances corresponding to tert-butyl groups are found

in the ¹H NMR spectrum in a 2:1 ratio. The lower

intensity downfield peak is broad at room temperature,

(32) Reid, S. M.; Neuner, B.; Schrock, R. R.; Davis, W. M. Organo-

metallics 1998, 17, 4077.

1142 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

Ta ble 7. Selected Bon d Len gth s, Bon d An gles, a n d

Dih ed r a l An gles for {[N₃N_F]W(CN-t-Bu )₃}BP h ₄

Bond Lengths (Å)

W-C(101)

W-C(102)

W-C(103)

W-N(1)

2.118(4)

2.128(4)

2.182(4)

2.070(3)

2.043(3)

W-N(3)

2.068(3)

2.253(3)

1.158(5)

1.150(5)

1.146(5)

W-N(4)

C(101)-N(5)

C(102)-N(6)

C(103)-N(7)

W-N(2)

Bond Angles (deg)

C(101)-W-C(102) 65.73(14) N(1)-W-N(2)

99.66(12)

140.41(12)

75.66(11)

96.98(12)

77.76(12)

73.17(12)

172.8(3)

176.3(3)

174.8(3)

135.6(2)

127.2(2)

132.2(2)

C(101)-W-C(103) 101.57(14) N(1)-W-N(3)

C(101)-W-N(1)

C(101)-W-N(2)

C(101)-W-N(3)

C(101)-W-N(4)

76.70(13) N(1)-W-N(4)

83.47(13) N(2)-W-N(3)

141.09(13) N(2)-W-N(4)

143.20(13) N(3)-W-N(4)

C(102)-W-C(103) 79.80(14) W-C(101)-N(5)

C(102)-W-N(1)

C(102)-W-N(2)

C(102)-W-N(3)

C(102)-W-N(4)

C(103)-W-N(1)

C(103)-W-N(2)

C(103)-W-N(3)

C(103)-W-N(4)

131.98(13) W-C(102)-N(6)

104.41(13) W-C(103)-N(7)

76.67(13) W-N(1)-C(1)

149.78(13) W-N(2)-C(9)

79.63(13) W-N(3)-C(17)

174.53(13) C(101)-N(5)-C(104) 173.7(4)

80.47(13) C(102)-N(6)-C(108) 175.5(4)

96.84(13) C(103)-N(7)-C(112) 169.7(4)

F igu r e 6. ORTEP view of the cation in {[N₃N_F]W(CN-t-

Bu)₃}BPh₄(35% probability level).

and the region of the methylene backbone protons

consists of several broad, featureless lumps. Lowering

the temperature to -20 °C results in the sharpening of

the resonances in the methylene backbone region to

yield five resonances in a 2:2:2:4:2 ratio; little fine

structure can be resolved. Temperature-dependent ¹H

NMR spectra suggest that the isocyanide ligand that

gives rise to the downfield resonance is the one that is

labile at room temperature on the NMR time scale. Six

different resonances for the ligand backbone carbons are

observed in the ¹³C NMR spectrum, and the ¹⁹F NMR

spectrum in THF features a 2:1 ratio of peaks, similar

to that observed in {[N₃N_F]W(CO)₂}Na(THF)_x. Addition

of [N₃N_F]W(OTf) to {[N₃N_F]W(CN-t-Bu)₃}OTf resulted

in formation of {[N₃N_F]W(CN-t-Bu)₂}OTf; conversely,

addition of 1 equiv of t-BuNC to {[N₃N_F]W(CN-t-Bu)₂}-

OTf yields {[N₃N_F]W(CN-t-Bu)₃}OTf quantitatively.

Dihedral Angles (deg)

N(4)-W-N(1)-C(1) 161.1(4) N(4)-W-N(3)-C(17) 154.1(4)

N(4)-W-N(2)-C(9) 176.1(3)

F igu r e 7. ¹⁹F NMR spectrum of [N₃N_F]W(C₂H₄) (asterisks

denote paramagnetic impurity).

Mo(CN-t-Bu)₃}⁺loses t-BuNC much more readily than

does {[N₃N_F]W(CN-t-Bu)₃}⁺.

Syn th esis of [N₃N_F]^3-Eth ylen e Com p lexes. Re-

duction of [N₃N_F]Mo(OTf) with sodium amalgam under

excess ethylene yields a mixture of paramagnetic and

diamagnetic compounds from which no compound could

be identified or isolated. In contrast, [N₃N_F]W(OTf)

reacts slowly with sodium amalgam in THF under ∼3

atm of ethylene to give paramagnetic [N₃N_F]W(C₂H₄)

in good yield (Table 1). Although no ¹H NMR resonance

could be observed readily, three ¹⁹F resonances could

be observed (Figure 7), the one which we assign to the

ortho fluorines at -100 ppm being ∼2500 Hz wide at

half-height. Even after reprecipitation of [N₃N_F]W(C₂H₄)

from solution, it contains a trace of an impurity (denoted

by asterisks in Figure 7). Preparation of analogous

[N₃N_F]W(olefin) complexes in which the olefin is 2-butene

or cyclopentene was not successful. The magnetic mo-

ment of [N₃N_F]W(C₂H₄) (measured in solution at 22 °C

by the Evans method) is 1.8 µ_B, consistent with one

unpaired electron.

The {[N₃N_F]W(CN-t-Bu)₃}BPh₄complex could be pre-

pared by oxidation of [N₃N_F]W(CN-t-Bu) with [Cp₂Fe]-

BPh₄followed by addition of excess isocyanide to the

resulting cation. Single crystals were obtained from

THF. Crystallographic data and collection and refine-

ment parameters are given in Table 4. A view of the

structure of the cation, along with the atom-labeling

scheme, is shown in Figure 6, while selected bond

lengths, bond angles and dihedral angles are listed in

Table 7. The highly distorted geometry is roughly a

pentagonal bipyramid with C(103) and N(2) occupying

the axial sites. The overall structure is similar to that

of {[N₃N_F]W(CO)₂}Na(ether)₃, except two ligands are

found in the apical pocket instead of one. The CN bond

lengths in all three isocyanide ligands are statistically

equivalent. However, the W-C(103) bond length is

slightly longer than the other two, suggesting that the

equatorial isocyanide is more weakly bound. The two

ligand arms cis to the equatorial isocyanide are twisted

to a significant degree, judging from the N(4)-W-N(1)-

C(1) and N(4)-W-N(3)-C(17) dihedral angles of 161

and 154°, respectively. The W-N(amide) bond lengths

are relatively long, as found in {[N₃N_F]W(CO)₂}Na-

(ether)₃. This extremely crowded complex can form as

a consequence of the relatively high W-isocyanide bond

strength and superior donor ability of the t-BuNC

ligand. As noted above, resonances consistent with the

formation of {[N₃N_F]Mo(CN-t-Bu)₃}OTf can only be

observed in low-temperature NMR spectra; i.e., {[N₃N_F]-

Oxidation of [N₃N_F]W(C₂H₄) with [Cp₂Fe]OTf in THF

led to the formation of diamagnetic {[N₃N_F]W(C₂H₄)}-

OTf as a red powder in high yield. The ¹H NMR

spectrum displays a peak at 3.10 ppm for the ethylene

ligand and H and ¹⁹F resonances that are characteristic

1

of diamagnetic [N₃N_F]^3-complexes. {[N₃N_F]W(C₂H₄)}-

OTf is diamagnetic as a consequence of ethylene break-

ing the pseudo C₃symmetry through π back-bonding,

leaving the other π type orbital (e.g., d_xz) empty. An

alternative description, although one that is not re-

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1143

quired on the basis of the compound’s diamagnetism,

is a W(VI) metallacyclopropane complex.

MoCl is reduced by magnesium under dinitrogen, while

[N₃N]MoCl is not reduced by magnesium under CO, is

still puzzling to us. At this stage we can only speculate

that the magnesium is poisoned by CO during the

attempted reduction under the conditions employed.

Discu ssion

The electron-withdrawing power of the pentafluo-

rophenyl ligand approximately counterbalances the

greater reducing power of tungsten versus molybdenum,

as evidenced by CO stretching frequencies that are

approximately the same in [N₃N_F]W(CO) (1846 cm^-1in

Nujol) and in [N₃N]Mo(CO) (1841 and 1832 cm^-1in

Nujol; 1859 cm^-1in pentane). Therefore, since [N₃N]-

Mo(N₂) is a known and stable molecule, we believed that

[N₃N_F]W(N₂) should be a stable species. The fact that

we cannot prepare it by the reduction of [N₃N_F]W(OTf)

or [N₃N_F]WCl under dinitrogen, while stronger trapping

agents (L) lead to isolable [N₃N_F]W(L) species, leads us

to conclude that some irreversible side reaction com-

petes with dinitrogen binding. Further evidence in

support of this conclusion is that the unidentified

paramagnetic product formed upon reduction of [N₃N_F]W-

(OTf) under dinitrogen or argon is found in trace

quantities, even in reactions that yield [N₃N_F]W(L)

species in relatively high yield, presumably as a conse-

quence of competition between the side reaction and the

reaction that yields [N₃N_F]W(L) species. However, we

also have not yet been able to prepare [N₃N]W(N₂);

therefore, the failure to form [N₃N_F]W(N₂) ultimately

may be traceable to a more profound difference between

Mo and W complexes that contain triamidoamine ligands.

It also should be noted that we have not observed [N₃N_F]-

Mo(N₂) to date, since oxidation of {[N₃N_F]Mo(N₂)}^-

yields {[N₃N_F]Mo}₂(µ-N₂).¹Therefore, we cannot predict

whether reduced back-bonding to dinitrogen in hypo-

thetical [N₃N_F]Mo(N₂) relative to [N₃N]Mo(N₂) in fact

would limit its stability with respect to loss of dinitro-

gen.

One of the curious aspects of the work reported here

is that some reductions to give M(III) species fail, even

though the product can be formed via another route,

while reductions to give M(III) species in the presence

of other substrates are smooth. An example is the failure

to reduce [N₃N]MoCl with magnesium to give known

[N₃N]Mo(CO), while [N₃N]Mo(C₂H₄) can be formed

smoothly. Another example is that [N₃N_F]W(CN-t-Bu)

can be synthesized by reduction of [N₃N_F]W(OTf) or

[N₃N_F]WCl in the presence of t-BuNC, while [N₃N_F]W-

(CO) can only be prepared by reduction of [N₃N_F]W-

(OTf). One logical mechanism of reduction is one-

electron reduction of the M(IV) triamidoamine complex,

followed by loss of an anion (chloride or triflate) to give

a trigonal-monopyramidal M(III) complex and binding

of the substrate (in either order). The other is initial

displacement of chloride or triflate by the substrate

followed by reduction of the resulting cation. For

example, we know that [N₃N_F]M(OTf) complexes react

with isocyanides to yield cationic species, so reduction

of [N₃N_F]M(OTf) in the presence of isocyanides almost

certainly proceeds via cationic species. However, in some

situations more reducible cationic species might form

to only a small extent, depending on the substrate in

question and the leaving group on the metal, and might

not be accessible if a poorer leaving group (chloride

instead of triflate) or a substrate that is a poor nucleo-

phile is employed. Nevertheless, the finding that [N₃N]-

Formation of M(II) anionic carbonyl complexes and

siloxycarbyne complexes upon addition of chlorotri-

methylsilane to them is not surprising in light of the

propensity for tungsten and molybdenum triamido-

amine complexes to form strong MtE bonds (E ) CR,

N, P, As).¹⁰In general, however, siloxycarbyne com-

plexes are rare.³³Perhaps the best known examples

have the formula M(CO)(COSiR₃)(DMPE)₂(M ) V,³⁴

Ta,^35,36Nb³⁵) and have been isolated as intermediates

in the reductive coupling of CO to form alkoxy alkynes

at V, Ta, and Nb centers.

Formation of [N₃N_F]WtCOV(Mes)₃by addition of

V(Mes)₃to [N₃N_F]W(CO) is related to the formation of

siloxycarbyne complexes. Related reactions involving

the (Mes)₃V fragment are known. For example, V(Mes)₃

has been employed to bind dinitrogen in putative

(Mes)₃V(N₂) to yield [(Mes)₃V(µ-N₂)V(Mes)₃], which can

be further reduced to yield complexes of the type

[(Mes)₃V(µ-N₂)V(Mes)₃]^n-(n ) 1, 2).³⁷Two equivalents

of (Mes)₃V(THF) also have been employed to remove an

oxygen atom from a chromium nitrosyl to give a chro-

mium(VI) nitride and (Mes)₃V(µ-O)V(Mes)₃.³⁸However,

we believe that the formation of [N₃N_F]WtCOV(Mes)₃

may be the only example of such a reaction in which

vanadium remains in the product and in which vana-

dium has been oxidized by one electron, at least the only

example of such a product that has been confirmed

through an X-ray study.

Formation of a cyanide complex via dealkylation of

an isocyanide complex has some precedent in the

literature. For example, upon being refluxed in ethanol,

[(t-BuNC)₇Mo]²⁺loses a carbonium ion to form [(t-

BuNC)₆Mo(CN)]⁺.³⁹Reaction of [(t-BuNC)₇Mo]²⁺with

zinc in THF yields [(t-BuNC)₄Mo(t-BuHNCCNH-t-Bu)-

(CN)]⁺, a product in which both reductive coupling and

dealkylation of the isocyanide ligands has occurred.⁴⁰

Perhaps the most closely related to the formation of

[N₃N]Mo(CN) is formation of trans-Mo(CN)₂(Me₈[16]-

aneS₄) (Me₈[16]aneS₄) 3,3,7,7,11,11,15,15,-octamethyl-

1,5,9,13-tetrathiacyclohexadecane) from Mo(CN)(t-BuNC)-

(Me₈[16]aneS₄) at -30 °C.²¹

A comparison of the IR stretching frequencies in

[N₃N]Mo(CN-t-Bu) (1838 cm^-1), [N₃N]Mo(CNAr) (1740

cm^-1), [N₃N_F]Mo(CN-t-Bu) (1787 cm^-1), and [N₃N_F]Mo-

(CNAr) (1777 cm^-1) suggests that the first is somewhat

high if all species are isostructural. Since [N₃N_F]W(CN-

(33) Dickson, R. S.; Ibers, J . A. J . Am. Chem. Soc. 1972, 94, 2988.

(34) Protasiewicz, J . D.; Lippard, S. J . J . Am. Chem. Soc. 1991, 113,

6564.

(35) Vrtis, R. N.; Liu, S.; Rao, C. P.; Bott, S. G.; Lippard, S. J .

Organometallics 1991, 10, 275.

(36) Protasiewicz, J . D.; Bronk, B. S.; Masschelein, A.; Lippard, S.

J . Organometallics 1994, 13, 1300.

(37) Ferguson, R.; Solari, E.; Floriani, C.; Osella, D.; Ravera, M.;

Re, N.; Chiesi-Villa, A.; Rizzoli, C. J . Am. Chem. Soc. 1997, 119, 10104.

(38) Odom, A. L.; Cummins, C. C.; Protasiewicz, J . D. J . Am. Chem.

Soc. 1995, 117, 6613.

(39) Giandomenico, C. M.; Hanau, L. H.; Lippard, S. J . Organome-

tallics 1982, 1, 142.

(40) Dewan, J . C.; Giandomenico, C. M.; Lippard, S. J . Inorg. Chem.

1981, 20, 4069.

1144 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

t-Bu) (1684 cm^-1) has been shown to contain a bent

isocyanide ligand, we suspect that [N₃N_F]W(CNAr)

(1679 cm^-1) is structurally analogous. Unfortunately,

none of the [N₃N]Mo(CNR) or [N₃N_F]Mo(CNR) com-

plexes has been structurally characterized, and there-

fore we cannot say with certainty whether all species

have a bent isocyanide. [N₃N]Mo(CN-t-Bu) would seem

most likely to have a linear isocyanide on the basis of

IR data and the fact that the tert-butyl isocyanide

probably is most resistant to bending in the crowded

coordination pocket in [N₃N]Mo(CN-t-Bu). Interestingly,

the production of cyanide by dealkylation in this cir-

cumstance would not require extensive rehybridization

about nitrogen. Therefore, a linear isocyanide in [N₃N]-

Mo(CN-t-Bu) might help explain the instability of [N₃N]-

Mo(CN-t-Bu) compared to the other isocyanide com-

plexes reported here.

becomes an 18-electron complex. The loss of the π bond

is reflected in the lengthening of the W-N_eqbond

distances in comparison with those of a typical C₃-

symmetric TREN complex. A seven-coordinate complex

can be prepared only when the metal is tungsten and

the ligand is tert-butyl isocyanide. Presumably both the

ability of W to form stronger bonds than Mo and the

strong electron donor properties of tert-butyl isocyanide

are necessary to overcome the steric and electronic

barriers associated with expansion of the coordination

sphere.

Other triamidoamine ethylene complexes of the type

reported here are known, in particular [N₃N]Ta-

(C₂H₄)^41,42and [N₃N_F]Re(C₂H₄).^32,43We were somewhat

surprised that {[N₃N_F]W(C₂H₄)}OTf is isolable, since

{[N₃N]Mo(C₂H₄)}OTf apparently loses ethylene and

coordinates triflate to yield [N₃N]Mo(OTf). However, the

result is consistent with a greater degree of back-

bonding from the more reducing tungsten(IV) center to

the ethylene ligand in {[N₃N_F]W(C₂H₄)}OTf than in

hypothetical {[N₃N]Mo(C₂H₄)}OTf, despite the presence

of the more electron-withdrawing [N₃N_F]^3-ligand. It is

not surprising that [N₃N_F]Mo(C₂H₄) cannot be isolated,

because it combines the less reducing Mo(III) center

with the electron-poor [N₃N_F]^3-ligand.

Overall we were pleased to find that both [N₃N_F]Mo

and [N₃N_F]W chemistry resemble [N₃N]Mo chemistry

and that differences could be readily understood in

terms of periodic differences between Mo and W. We

were also surprised to find the extent to which higher

coordination numbers can be achieved in [N₃N_F]^3-

complexes and are eager to determine whether [N₃N_F]^3-

or related complexes therefore might be useful as

catalysts in some simple catalytic reactions. Unfortu-

nately, however, we have not been able to answer the

question as to why the dinitrogen chemistry of [N₃N_F]-

Mo is accessible (although [N₃N_F]Mo(N₂) has not been

observed), while the dinitrogen chemistry of [N₃N_F]W

so far has not been observed. In fact, there is still no

example of a triamidoamine complex of tungsten that

contains dinitrogen. We hope to revisit this question in

the future as we explore the chemistry of accessible

triamidoamine complexes of both metals that contain

aryl substituents on the amido nitrogens other than

C₆F₅.¹¹

One of the most interesting aspects of the present

study is the large number of complexes with coordina-

tion number greater than 5 that can be prepared,

especially when the metal is tungsten. There appear to

be two classes of six-coordinate complexes that contain

a triamidoamine ligand. In one class are complexes in

which the C₃symmetry of the TREN ligand is main-

tained, and two additional ligands occupy the apical

pocket. Structurally characterized complexes of this type

include [N₃N]W(cyclo-CHCH₂CH₂CH₂), [N₃N]W(C₅H₈)-

(H),⁸and [N₃N]W(CO)(H).¹⁴The two ligands in the

apical pocket rotate rapidly with respect to the [N₃N]

ligand framework on the NMR time scale; therefore, the

NMR spectra of these complexes appear to be C₃-

symmetric. We place the {[N₃N_F]M(CNR)₂}OTf com-

plexes in this category.

Six-coordinate complexes in the second category adopt

a pseudo-octahedral coordination geometry around the

metal center in which an added ligand joins the three

amide ligands in the equatorial plane. Prior to the

current study, the only structurally characterized com-

plex of this type was [N₃N_F]W(O)(3,5-Me₂C₆H₃);²

{[N₃N_F]W(CO)₂}Na(ether)₃has a similar structure.

Compounds that have not been structurally character-

ized but that we believe adopt similar structures on the

basis of NMR data include [N₃N]Mo(NTMS)(Me),⁴

[N₃N]Mo(NMe)(Me),⁴and [N(CH₂CH₂NSiMe₃)₂(CH₂-

CH₂NCH₃)]Mo{NN(CH₃)₂}(CH₃).⁶In complexes of this

type a mirror plane passes through the unique ligand

in the equatorial plane and the amide trans to it, and

the ligand trans to the amine donor contains triply

bound or pseudo triply bound C, N, or O. However, NMR

spectra of complexes in solution are sometimes consis-

tent with the complexes being C₃-symmetric on the

NMR time scale, as in [N₃N_F]W(O)(3,5-Me₂C₆H₃). In

complexes with this geometry the M-N_eqπ bond that

is lost must be compensated by multiple bonding

between the metal and the axial ligand.

Exp er im en ta l P r oced u r es

Gen er a l Deta ils. All experiments were conducted under

nitrogen in a Vacuum Atmospheres drybox, using standard

Schlenk techniques, or on a high-vacuum line (<10^-4Torr).

Glassware was dried in a 135 °C oven overnight. Pentane was

washed with HNO₃/H₂SO₄(5/95 v/v), sodium bicarbonate, and

water, dried over CaCl₂, and then distilled from sodium

benzophenone with tetraglyme under nitrogen. Ether and THF

were purified by sparging with nitrogen and passing through

alumina columns.⁴⁴Reagent grade benzene was distilled from

sodium benzophenone under nitrogen. Toluene was distilled

from molten sodium. Methylene chloride was distilled from

CaH₂. All solvents were stored in the drybox over activated 4

The only seven-coordinate complex containing a tri-

amidoamine ligand to be prepared up to this point was

[N₃N]WH₃.¹⁴Hydride ligands are small enough to fit

into the apical pocket of that trigonally symmetric

complex. This is not possible in {[N₃N_F]W(CN-t-Bu)₃}-

BPh₄; thus, one of the isocyanides takes up a position

in the triamido plane. As in the case of {[N₃N_F]W(CO)₂}-

Na(ether)₃, one of the two W-N(amide) π-bonds must

be sacrificed, and {[N₃N_F]W(CN-t-Bu)₃}BPh₄therefore

(41) Freundlich, J .; Schrock, R. R.; Cummins, C. C.; Davis, W. M.

J . Am. Chem. Soc. 1994, 116, 6476.

(42) Freundlich, J . S.; Schrock, R. R.; Davis, W. M. Organometallics

1996, 15, 2777.

(43) Neuner, B.; Schrock, R. R. Organometallics 1996, 15, 5.

(44) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;

Timmers, F. J . Organometallics 1996, 15, 1518.

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1145

Å molecular sieves. Deuterated solvents were freeze-pump-

thaw-degassed and vacuum-transferred from an appropriate

drying agent.

(ν_CO); µ ) 1.77 µ_B(SQUID). Anal. Calcd for C₁₆H₃₉N₄Si₃MoO:

C, 39.73; H, 8.13; N, 11.58. Found: C, 39.54; H, 8.18; N, 11.55.

[N₃N]MotCOSiMe₃. [N₃N]Mo(CO) (100 mg, 0.21 mmol)

was dissolved in 5 mL of THF. Magnesium powder (20 mg,

0.87 mmol) and TMSCl (45 µL, 0.36 mmol) were added, and

the mixture was stirred for 3.5 h. The solvent was removed in

vacuo and the residue extracted with 7 mL of pentane. The

pentane solution was filtered through a pad of Celite, and the

volume was reduced to 3 mL. The pentane solution was cooled

to -20 °C to give the product as pale yellow needles: yield

105 mg (91%); ¹H NMR δ 3.48 (t, NCH₂CH₂N), 3.24 (t, NCH₂-

CH₂N), 0.49 (s, SiMe₃), 0.40 (s, SiMe₃); ¹³C NMR δ 208.34

(MoCOSiMe₃), 53.53 (NCH₂CH₂N), 52.56 (NCH₂CH₂N), 5.07

(SiMe₃), 2.55 (SiMe₃). Anal. Calcd for C₁₉H₄₈N₄Si₄MoO: C,

40.98; H, 8.69; N, 10.06. Found: C, 40.69; H, 8.70; N, 10.07.

[N₃N]Mo(CN-t-Bu ). [N₃N]Mo(N₂) (150 mg, 0.31 mmol) was

dissolved in 5 mL of toluene, and the solution was cooled to

-20 °C. t-BuNC (39 mg, 0.47 mmol) was added to the solution,

which was stirred overnight. The solvent was removed in vacuo

to give an orange residue. The product was obtained as rust-

colored needles upon recrystallization of the crude product

from diethyl ether: yield 160 mg (96%); ¹H NMR δ 13.37 (CH₂),

3.76 (t-Bu), 0.12 (SiMe₃), -39.00 (CH₂); IR (Nujol) cm^-11838

(br, ν_NC); µ ) 1.74 µ_B(SQUID).

[N₃N]Mo(CNAr ). [N₃N]Mo(N₂) (75 mg, 0.16 mmol) was

dissolved in 4 mL of toluene, and the solution was cooled to

-20 °C. 2,6-Me₂C₆H₃NC (25 mg, 0.19 mmol) was dissolved in

1 mL of toluene and the solution added to the stirred solution

of [N₃N]Mo(N₂). After 1 h the toluene was removed in vacuo

and the residue was extracted with 7 mL of hexamethyldisi-

loxane. After filtering, the solution was cooled to -20 °C to

afford the product as red plates: yield 56 mg (62%, not

optimized); ¹H NMR δ 61.90 (NCH₂CH₂N, ∆ν_1/2) 509 Hz),

37.15 (Ar H, ∆ν_1/2) 138 Hz), 1.87 (SiMe₃, ∆ν_1/2) 47 Hz), -0.66

(CH₃, ∆ν_1/2) 156 Hz), -29.81 (NCH₂CH₂N, ∆ν_1/2) 276 Hz),

-68.85 (Ar H, ∆ν_1/2) 882 Hz); IR (Nujol) cm^-11740 (ν_NC). Anal.

Calcd for C₂₄H₄₈N₅Si₃Mo: C, 49.12; H, 8.24; N, 11.93. Found:

C, 48.93; H, 8.31; N, 11.82.

{[N₃N]Mo(CN-t-Bu )}OTf. [N₃N]Mo(CN-t-Bu) (110 mg, 0.20

mmol) was dissolved in 4 mL of THF, and the solution was

cooled to -20 °C. [FeCp₂]OTf (68 mg, 0.20 mmol) was added

to the solution, and the reaction mixture was stirred for 25

min. The solvent was removed in vacuo, and the residue was

washed with 20 mL of pentane in order to remove ferrocene.

The residue was dried to give the product as a burnt-orange

powder: yield 129 mg (92%); ¹H NMR (THF-d₈) δ 12.83

(SiMe₃), 9.28 (t-Bu), -29.38 (CH₂), -98.14 (CH₂); ¹⁹F NMR

(THF-d₈) δ -78.64 (CF₃SO₃); IR (THF) cm^-12147 (ν_NC); µ )

2.71 µ_B(SQUID).

[N₃N]Mo(CN). [N₃N]Mo(CN-t-Bu) (65 mg, 0.12 mmol) was

dissolved in 6 mL of toluene. The solution was sealed in a low-

pressure glass bomb and was heated to 86 °C for 36 h, during

which time the color changed from orange to yellow. The

solvent was removed, and the yellow solid was washed with

cold pentane: yield 51 mg (88%); ¹H NMR δ 7.73 (SiMe₃),

-25.7 (CH₂), -112.4 (CH₂); µ ) 2.73 µ_B(SQUID). Anal. Calcd

for C₁₆H₃₉N₅Si₃Mo: C, 39.89; H, 8.16; N, 14.54. Found: C,

39.72; H, 8.31; N, 14.55.

NMR data were obtained at 300 or 500 MHz (¹H), 125.8

1

MHz (¹³C), and 282 MHz (¹⁹F). H and ¹³C data are listed in

parts per million downfield from tetramethylsilane and were

referenced using the solvent peak. ¹⁹F NMR are listed in parts

per million downfield of CFCl₃as an external standard.

Coupling constants are given in hertz; routine couplings are

not listed. Spectra were obtained at 25 °C in C₆D₆unless

otherwise noted. Magnetic susceptibility measurements were

done by NMR using the Evans method⁴⁵as modified by Sur,⁴⁶

with (Me₃Si)₂O as an internal standard, or in the solid state

using a SQUID magnetometer, as described below. Elemental

analyses (C, H, N) were performed on a Perkin-Elmer 2400

CHN analyzer in our own laboratory, by Microlytics Analytical

Laboratories of Deerfield, MA, or by Kolbe Microanalytical

Laboratory, Mulheim an der Ruhr, Germany. X-ray data were

collected on a Bruker SMART/CCD diffractometer; general

experimental details are described in the literature.⁴⁷

[N₃N]MoCl,⁵[N₃N]Mo(N₂),⁶[N₃N]WCl, [N₃N_F]MoCl, [N₃N_F]W-

(OTf), and [N₃N_F]Mo(OTf)¹were synthesized as described in

the literature, except WCl₄(dme)⁴⁸was employed for the

synthesis of the tungsten chloride. [Cp₂Fe]OTf⁴⁹was prepared

as described in the literature, while [Cp₂Fe]BPh₄and [Cp₂Fe]-

BAr^Fwere prepared in a manner analogous to the literature

4

preparation of 1,1′-dimethylferrocenium tetraphenylborate.⁵⁰

NaBAr^F₄was prepared by the method of Brookhart.⁵¹V(Mes)₃-

(THF) was prepared as described by Seidel and Kreisel.²⁴

Sodium amalgam (0.5 wt %) was freshly prepared from sodium

spheres and triply distilled mercury (Strem). CO (99.99%) and

ethylene (polymer grade) were purchased from Matheson and

used directly from the cylinder. ¹³CO was purchased from

Cambridge Isotope Laboratories. Other reagents were pur-

chased from commercial vendors and used as received.

SQUID Ma gn etic Su scep tibility Mea su r em en ts. Mea-

surements were carried out on a Quantum Design SQUID

magnetometer. Data were obtained at a field strength of 5000

G. Straws and gel caps (Gelatin Capsule No. 4 Clear) were

purchased from Quantum Design. The sample was prepared

in the drybox by the following method. A gel cap and a square

of Parafilm were weighed. The sample was placed in the gel

cap and the Parafilm inserted above it. The gel cap was closed,

and the mass of the sample was ascertained by weighing the

loaded gel cap. The gel cap was placed in a straw, which was

then mounted on the sample rod and placed in the magne-

tometer. Two runs were performed on the sample, one from 5

to 300 K and a second from 300 to 5 K. Measurements were

made at the following increments: 5-10 K (every 1 K), 10-

20 K (every 2 K), 20-50 K (every 3 K), 50-100 K (every 5 K),

100-200 K (every 10 K), 200-300 K (every 20 K).

[N₃N]Mo(CO). [N₃N]Mo(N₂) (100 mg, 0.21 mmol) was

dissolved in 5 mL of benzene and sealed in a 25 mL bomb.

The solution was subjected to two freeze-pump-thaw cycles,

and 1 equiv of carbon monoxide was introduced. Over 15 min

the solution changed color from orange-red to emerald green.

After 3 h the solvent was removed in vacuo and the residue

extracted with 5 mL of pentane. The pentane solution was

cooled to -20 °C to give the product as green needles: yield

[N₃N]Mo(C₂H₄). [N₃N]MoCl (650 mg, 1.32 mmol) was

dissolved in 15 mL of THF, and the solution was placed in a

glass bomb with a stirring bar and magnesium powder (64 mg,

2.67 mmol). The vessel was sealed and subjected to three

freeze-pump-thaw cycles in order to remove any dinitrogen

present. Ethylene (∼5 equiv) was condensed onto the frozen

solution. The solution was thawed and stirred for 12 h, during

which time the color changed from orange-red to purple. The

solvent was removed in vacuo, and the residue was extracted

with 20 mL of pentane. The extract was filtered through Celite

and the pentane was removed from the filtrate in vacuo. The

purple solid was recrystallized from hexamethyldisiloxane at

-20 °C to afford the product as purple needles: yield 623 mg

1

85 mg (85%); H NMR δ 13.17 (CH₂), -2.03 (SiMe₃), -38.04

(CH₂); IR (Nujol) cm^-11841, 1832 (ν_CO); IR (pentane) cm^-11859

(45) Evans, D. F. Chem. Commun. 1959, 2003.

(46) Sur, S. K. J . Magn. Reson. 1989, 82, 169.

(47) Rosenberger, C.; Schrock, R. R.; Davis, W. M. Inorg. Chem.

1997, 36, 123.

(48) Persson, C.; Andersson, C. Inorg. Chim. Acta 1993, 203, 235.

(49) Schrock, R. R.; Sturgeoff, L. G.; Sharp, P. R. Inorg. Chem. 1983,

22, 2801.

(50) J ordan, R. F.; LaPointe, R. E.; Bradley, P. K.; Baezinger, N.

Organometallics 1989, 8, 2892.

(51) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992,

11, 3920.

1146 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

(97%); ¹H NMR δ 3.63 (SiMe₃); µ ) 1.73 µ_B(SQUID). Anal.

Calcd for C₁₇H₄₃N₄Si₃Mo: C, 42.21; H, 8.96; N, 11.58. Found:

C, 42.39; H, 9.31; N, 11.55.

high-vacuum line. It was degassed three times by a freeze-

pump-thaw cycle, and CO (2.05 mmol, 4 equiv) was intro-

duced by vacuum transfer at 77 K. The reaction flask was then

sealed and warmed to room temperature, and the solution was

stirred for 2.5 h. The volatile components were removed in

vacuo, and the red residue was extracted with dichlo-

romethane. The solution was filtered through Celite and the

volume reduced to ∼ 4 mL. Pentane (10 mL) was layered on

top of the dichloromethane solution, and the sample was stored

at -40 °C for 3 days. The red crystalline product was isolated

by decanting off the mother liquor: yield 330 mg in two crops

(76%); ¹H NMR δ 29.3 (br s, ∆_1/2) 553, NCH₂N), -19.2 (br s,

[N₃N_F]Mo(CO)Na (15-cr ow n -5). A two-chamber reaction

vessel was charged with 0.5% Na/Hg (7 g, 1.5 mmol Na) in

one chamber, and a suspension of [N₃N_F]Mo(OTf) (443 mg, 0.5

mmol) in THF (10 mL) in the other chamber. The vessel was

degassed via three freeze-pump-thaw cycles and refilled with

CO (400 mmHg, 2 mmol). The reaction mixture was stirred

for 2 h, during which time all of the insoluble triflate dissolved

to yield an orange solution. The vessel was pumped back into

the drybox, and the reaction mixture was decanted from the

excess amalgam. A solution of 15-crown-5 (132 mg, 0.6 mmol)

in 2 mL of THF was added. The mixture was stirred for 1 h,

the THF was removed, and the residue was dissolved in

toluene. The salts were filtered off, and the toluene solution

was concentrated to 1 mL. Pentane (0.5 mL) was added, and

the solution was cooled to -40 °C overnight to yield orange

crystals. The mother liquor was decanted off, and the crystals

were washed three times with pentane: yield 328 mg (0.325

∆

) 415, NCH₂N); ¹⁹F NMR δ -132.1 (br s, ∆_1/2) 277),

1/2

-170.5 (s); IR (Nujol) cm^-11846 (ν_CO); µ_eff) 2.6 µ_B(Evans

method). Anal. Calcd for C₂₅H₁₂N₄F₁₅OW: C, 35.19; H, 1.42;

N, 6.57. Found: C, 35.45; H, 1.45; N, 6.74.

Obser va tion of {[N₃N_F]W(CO)₂}Na L₃(L ) THF , Eth er ).

A 50 mL Schlenk flask was charged with 0.5% Na/Hg (5.75 g,

1.25 mmol Na), [N₃N_F]W(OTf) (487 mg, 0.5 mmol), and 15 mL

of THF. The vessel was degassed by performing three freeze-

pump-thaw cycles and refilled with CO (300 mmHg, 1.75

mmol). When the reaction mixture was thawed to room

temperature, the color turned deep purple immediately, and

all of the insoluble triflate dissolved. ¹⁹F NMR (THF) δ -151.43

(br s, 2, F_o), -151.68 (br s, 4, F_o), -170.17 (t, 4, F_m), -171.05

(t, 2, F_m), -175.60 (t, 2, F_p), -177.18 (t, 1, F_p); ¹³C NMR (THF)

δ 246.24 (t, ¹³CO, J _WC) 112), 242.39 (t, ¹³CONa, J _WC) 215);

IR (Nujol) cm^-11926 (CO), 1716 (CONa); IR (THF) cm^-11952

1

mmol, 65%); H NMR δ 3.73 (t, 6, CH₂), 3.19 (s, 20, crown),

2.22 (t, 6, CH₂); ¹³C NMR δ 226.69 (CO), 143.50 (d, C_o, J _CF

)

240), 140.32 (br s, C_ipso), 138.20 (d, C_m, J _CF) 245), 135.40 (d,

C_p, J _CF) 231), 70.21 (crown), 56.46 (CH₂), 53.27 (CH₂); ¹⁹F

NMR δ -151.73 (d, 6, F_o), -168.81 (t, 6, F_m), -174.56 (t, 3,

F_p); IR (Nujol) 1701 cm^-1(ν_CO). Anal. Calcd for C₃₅H₃₂F₁₅N₄O₆-

NaMo: C, 41.68; H, 3.20; N, 5.56. Found: C, 41.55; H, 3.21;

N, 5.43.

(ν_CO), 1726 (ν_CONa); 1895 (ν _CO), 1682 (ν _CONa). ¹³C-labeled

material was prepared in an analogous fashion using ¹³CO.

The reaction can also be performed in ether. When an ether

solution was stored for several months at -40 °C, crystals were

obtained that were suitable for an X-ray diffraction study.

[N₃N_F]W(CO)Na (15-cr ow n -5). Purple {[N₃N_F]W(CO)₂}Na-

(THF)₃was prepared as described above from 292 mg of

[N₃N_F]W(OTf) (0.3 mmol) and 3.45 g of Na/Hg (0.75 mmol).

Prolonged exposure of the THF solution to vacuum left a yellow

solid. The yellow solid was dissolved in toluene, and a solution

of 15-crown-5 (79 mg, 0.36 mmol) was added, which resulted

in precipitation of more sodium salts and a darkening of the

solution from yellow to orange. After 30 min, the reaction was

filtered through Celite, and the solution was concentrated to

2 mL. Adding an equal volume of pentane and cooling the

mixture to -40 °C resulted in the formation of orange crystals.

The mother liquor was decanted off, and the crystals were

obtained: yield 194 mg (0.177 mmol, 59%); ¹H NMR δ 3.63 (t,

6, CH₂), 2.86 (s, 20, crown), 2.20 (t, 6, CH₂); ¹³C NMR (THF) δ

224.20 (t, ¹³CO, J _CW) 270), 144.87, 142.97, 140.29, 138.63

(C₆F₅), 69.34 (crown), 57.55 (CH₂), 53.93 (CH₂); ¹⁹F NMR δ

-151.96 (d, 6, F_o), -168.89 (t, 6, F_m), -173.85 (t, 3, F_p); IR

13

[N₃N_F]MotCOSiMe₃. A two-chamber reaction vessel was

charged with [N₃N_F]W(OTf) (443 mg, 0.5 mmol) and THF (8

mL) in one chamber and 0.5% Na/Hg (5.75 g, 1.25 mmol. Na)

in the other. The vessel was degassed by performing three

freeze-pump-thaw cycles and refilled with CO (400 mmHg,

2 mmol). The reaction mixture was thawed and stirred for 2

h to yield a dark orange solution. The vessel was pumped back

into the drybox, and the reaction mixture was decanted from

the excess amalgam. A solution of chlorotrimethylsilane (82

mg, 0.75 mmol) in THF (2 mL) was added to the reaction

mixture, resulting in a color change to pale yellow and the

precipitation of a white powder. THF was removed, and the

residue was dissolved in ether. The salts were filtered off, and

the ether solution was cooled to -40 °C. Colorless crystals (211

mg, 0.25 mmol, 50%) were collected in two crops: ¹H NMR δ

3.37 (t, 6, CH₂), 2.13 (t, 6, CH₂), -0.49 (s, 9, SiMe₃); ¹³C NMR

δ 212.44 (CO), 142.81 (d, C_o, J _CF) 244), 137.97 (br s, C_ipso),

137.93 (d, C_m, J _CF) 248), 137.09 (d, C_p, J _CF) 246), 57.34

(CH₂), 52.78 (CH₂), -1.61 (SiMe₃); ¹⁹F NMR δ -150.40 (d, 6,

F_o), -165.23 (t, 6, F_m), -165.91 (t, 3, F_p). Anal. Calcd for

C

₂₈H₂₁F₁₅N₄OSiMo: C, 40.11; H, 2.52; N, 6.68. Found: C,

39.87; H, 2.58; N, 6.75.

(Nujol) cm^-11628 (ν_CO), 1592 (ν _CO), 1564 (ν

_O). Anal. Calcd

13

13 18

[N₃N_F]Mo(CO). A solution of [N₃N_F]Mo(CO)Na(15-crown-

5) (252 mg, 0.25 mmol) in THF (6 mL) was cooled to -40 °C.

Ferrocenium tetraphenylborate (126 mg, 0.25 mmol) was

added as a solid, and the color of the reaction mixture

immediately changed from orange to green. After the mixture

was stirred for 1 h at room temperature, THF was removed,

and the residue was dissolved in ether. Sodium tetraphenylbo-

rate was removed by filtration. The ether was removed in

vacuo, and the residue was washed several times with pentane

to remove ferrocene and yield 158 mg (0.206 mmol, 83%) of

spectroscopically pure green powder. Analytically pure mate-

rial was obtained by recrystallization from a mixture of ether

and pentane at -40 °C: ¹H NMR δ 12.85 (br s, CH₂), -23.90

(br s, CH₂); ¹⁹F NMR δ -126.8 (br s, F_m), -167.00 (s, F_p); IR

(Nujol) cm^-11889 (ν_CO); µ_eff) 2.1 µ_B(Evans method). Anal.

Calcd for C₂₅H₁₂F₁₅N₄OMo: C, 39.24; H, 1.58; N, 7.32. Found:

C, 39.16; H, 1.65; N, 7.26.

C

for C₃₅H₃₂F₁₅N₄O₆NaW: C, 38.34; H, 2.94; N, 5.11. Found: C,

38.21; H, 3.08; N, 4.96.

[N₃N_F]WtCOSiMe₃. A solution of [N₃N_F]W(CO) (100 mg,

0.117 mmol) in 5 mL of THF was added to 0.5% Na/Hg

amalgam (539 mg, 0.117 mmol). The reaction mixture was

stirred for 1 h, at which point ¹⁹F NMR indicated clean

formation of the anion. The reaction mixture was filtered, and

trimethylsilyl chloride (18 µL, 0.14 mmol, 1.2 equiv) was added.

The reaction mixture was stirred for 3 h, the volatile compo-

nents were removed in vacuo, and the brown residue was

extracted with dichloromethane. The solution was filtered

through Celite and the volume reduced to ∼4 mL. Pentane

(10 mL) was layered on top of the dichloromethane solution,

and the sample was stored at -40 °C for 15 h. Brown blocks

were isolated by decantation of the mother liquor: yield 73

1

mg (67%); H NMR δ 3.33 (t, 6, NCH₂N), 2.10 (t, 6, NCH₂N),

[N₃N_F]W(CO). A 100 mL round-bottomed flask was charged

with [N₃N_F]W(OTf) (500 mg, 0.513 mmol), 25 mL of THF, 0.5%

Na/Hg amalgam (2.36 g, 0.513 mmol, 1 equiv), and a stir bar.

The flask was fitted with a vacuum adapter and attached to a

-0.487 (s, 9, SiMe₃); ¹⁹F NMR δ -151.1 (s, 6, F_o), -165.7 (s, 9,

F_mand F_p); ¹³C NMR δ 216.9 (WtCOSiMe₃), 144.8 (C₆F₅),

141.6 (C₆F₅), 139.3 (C₆F₅), 137.2 (C₆F₅), 136.0 (C₆F₅), 56.8

(NCH₂N), 52.1 (NCH₂N), -1.4 (Si(CH₃)₃). Anal. Calcd for

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1147

C₂₈H₂₁N₄F₁₅OSiW: C, 36.30; H, 2.28; N, 6.05. Found: C, 35.92;

H, 2.18; N, 5.99.

(OTf) was removed by filtration, and crystals were grown from

dichloromethane at -40 °C. Orange crystals were collected and

dried in vacuo: yield 573 mg (0.6 mmol, 82%); ¹H NMR δ 41.7

(br s, 2, meta), 31.8 (br s, 6, CH₂), 8.7 (br s, 6, Ar Me), -25.1

(br s, 6, CH₂), -33.1 (br s, 1, para); ¹⁹F NMR δ -82.6 (br s, 6,

F_o), -134.9 (br s, 3, F_p), -161.1 (s, 6, F_m); IR (Nujol) cm^-11679

(ν_NC). Anal. Calcd for C₃₃H₂₁F₁₅N₅W: C, 41.44; H, 2.21; N, 7.32.

Found: C, 41.54; H, 2.34; N, 7.23.

[N₃N_F]W(CO)V(Mes)₃. [N₃N_F]W(CO) (100 mg, 0.117 mmol)

and V(mesityl)₃(THF) (56 mg, 0.12 mmol) were placed in a vial,

and toluene (4 mL) was added. The deep black solution was

stirred for 1 h, at which point ¹⁹F NMR showed complete

conversion to product. The reaction mixture was filtered and

the volume of the toluene reduced to ∼2 mL. Pentane was

layered on and the vial cooled to -40 °C. After 15 h, black

crystals had formed and were isolated by decanting the mother

liquor: yield 130 mg in two crops (88%); ¹H NMR δ 17.5 (br s,

[N₃N_F]Mo(CN-n -Bu ). [N₃N_F]MoCl (200 mg, 0.259 mmol)

and 0.5% sodium amalgam (1.19 g, 0.259 mmol) were added

to a vial. A solution of n-butyl isocyanide (27 µL, 0.26 mmol)

in 10 mL of THF was added all at once. The reaction mixture

was stirred for 3 h, at which point ¹⁹F NMR showed the

reaction to be complete. This mixture was then filtered, and

the volatile components were removed from the filtrate in

vacuo. The product was recrystallized from dichloromethane

by layering pentane on top and cooling the sample to -40 °C.

After 15 h large reddish needles formed, which were isolated

by decanting away the mother liquor: yield 162 mg (76%); ¹H

NMR δ 5.7 (br s, ∆_1/2) 81, 6, NCH₂N), 5.2 (br s, ∆_1/2) 25,

n-butyl), 4.0 (br s, ∆_1/2) 12, n-butyl), -0.1 (br s, ∆_1/2) 25,

n-butyl), -27.6 (br s, ∆_1/2) 94, 6, NCH₂N); ¹⁹F NMR δ -67

(br s, ∆_1/2) 716, 6, F_o), -144.0 (s, 3, F_p), -161.2 (s, 6, F_m); IR

(Nujol) cm^-11790 (ν_NC); µ_eff) 2.3 µ_B(Evans method). Anal.

Calcd for C₂₉H₂₁N₅F₁₅Mo: C, 42.46; H, 2.58; N, 8.54. Found:

C, 42.14; H, 2.55; N, 8.53.

∆

1/2

) 22, 9, mesityl Me_p), 16.2 (br s, ∆_1/2) 300, 18, mesityl

Me_o), 6.6 (br s, ∆_1/2) 45, 6, mesityl H_m), 3.38 (s, 6, NCH₂N),

2.06 (s, 6, NCH₂N); ¹⁹F NMR δ -153.2 (s, 6, F_o), -162.9 (s, 3,

F_p), -164.3 (s, 6, F_m); IR (KBr) cm^-12916, 2867, 1587, 1501,

1278, 985, 851, 756, 729; µ_eff) 2.1 µ_B(Evans method). Anal.

Calcd for

C₅₉H₅₃N₄F₁₅OVW: C, 52.34; H, 3.95; N, 4.14.

Found: C, 52.28; H, 3.77; N, 3.96.

[N₃N_F]Mo(CN-t-Bu ). A 50 mL round-bottom flask was

charged with [N₃N_F]Mo(OTf) (2.22 g, 2.5 mmol) and 0.5% Na/

Hg (11.5 g, 2.5 mmol of Na). A solution of tert-butyl isocyanide

(208 mg, 2.5 mmol) in THF (25 mL) was added, and the

reaction mixture was stirred vigorously for 1 h. All of the

[N₃N_F]Mo(OTf) dissolved to give a red solution. THF was

removed in vacuo, and the residue was redissolved in dichlo-

romethane. Na(OTf) was removed by filtration, and crystals

were grown from 10 mL of dichloromethane at -40 °C. Orange

crystals were collected and dried in vacuo: yield 1.63 g (1.98

{[N₃N_F]W(CN-t-Bu )}BAr ^F₄. A solution of [N₃N_F]W(CN-t-

Bu) (363 mg, 0.4 mmol) in CH₂Cl₂(16 mL) was cooled to -40

°C. [Cp₂Fe]BAr^F(420 mg, 0.4 mmol) was added as a solid,

1

mmol, 79%); H NMR δ 11.1 (br s, 9, t-Bu), 6.6 (br s, 6, CH₂),

4

-28.2 (br s, 6, CH₂); ¹⁹F NMR δ -59.8 (br s, 6, F_o), -143.6 (br

s, 3, F_p), -159.7 (s, 6, F_m); IR (Nujol) cm^-11787 (ν_NC). Anal.

Calcd for C₂₉H₂₁F₁₅N₅Mo: C, 42.46; H, 2.58; N, 8.54. Found:

C, 42.40; H, 2.63; N, 8.44.

which resulted in an immediate color change from orange to

red. The volume was reduced to 3 mL, and an equal volume

of pentane was added. Red crystals were formed upon cooling

to -40 °C for 2 h. The crystals were collected and dried in

vacuo: yield 570 mg (0.32 mmol, 80%); ¹H NMR (CDCl₃) δ 7.38

(s, 4, BAr^Fpara), 7.17 (s, 8, BAr^Fortho), 0.70 (br s, 9, t-Bu),

[N₃N_F]W(CN-t-Bu ). [N₃N_F]WCl (700 mg, 0.813 mmol) and

0.5% Na/Hg amalgam (3.74 g, 0.813 mmol) were added to a

100 mL round-bottomed flask, and a solution of tert-butyl

isocyanide (92 µL, 0.813 mmol) in 20 mL of THF was added.

A ¹⁹F NMR spectrum showed the reaction to be complete after

1 h. The solution was decanted from the amalgam, and the

volatile components were removed in vacuo. The orange-brown

residue was extracted with dichloromethane, and the extract

was filtered through Celite. The volume was reduced until the

solution was saturated (∼20 mL), and the solution was then

chilled to -40 °C overnight. Orange plates of the product were

4

-28.1 (br s, 6, CH₂), -55.0 (br s, 6, CH₂); ¹⁹F NMR (CDCl₃) δ

-62.8 (s, 24, BAr^F₄) -98.6 (br s, 6, F_m), -148.3 (br s, 3, F_p); IR

(Nujol) cm^-12136 (ν_NC); µ_eff) 2.8 µ_B(Evans method). Anal.

Calcd for C₆₁H₃₃BF₃₉N₅W: C, 41.36; H, 1.88; N, 3.95. Found:

C, 41.44; H, 1.90; N, 3.92.

{[N₃N_F]W(CN-t-Bu )}BP h ₄. This complex was synthesized

in a manner similar to that used to prepare {[N₃N_F]W(CN-t-

Bu)}BAr^F^-, starting from [N₃N_F]W(CN-t-Bu) (307 mg, 0.338

4

mmol) and [Cp₂Fe]BPh₄(171 mg, 0.338 mmol). The red product

(223 mg, 0.182 mmol, 54%) crystallized out of dichloromethane

upon cooling the solution to -40 °C; IR (Nujol) cm^-12133 (ν_NC).

{[N₃N_F]W(CNAr )}BAr ^F₄. This complex was synthesized in

a manner similar to that used to prepare {[N₃N_F]W(CN-t-Bu)}-

1

isolated by decantation: yield 683 mg in two crops (92%); H

NMR δ 13.6 (br s, ∆_1/2) 67, t-Bu), 8.0 (br s, ∆_1/2) 132,

NCH₂N), -25.8 (br s, ∆_1/2) 99, NCH₂N); ¹⁹F NMR δ -77.0

(br s, ∆_1/2) 86, F_o), -142.5 (s, F_m), -161.2 (s, F_p); IR (Nujol)

cm^-11684 (ν_NC); µ_eff) 2.2 µ_B(Evans method); µ ) 1.74(1) µ_B

(SQUID). Anal. Calcd for C₂₉H₂₁F₁₅N₅W: C, 38.35; H, 2.33;

N, 7.71. Found: C, 38.20; H, 2.22; N, 7.75.

[N₃N_F]Mo(CNAr ). This complex was synthesized in a

manner similar to that used to prepare [N₃N_F]Mo(CN-t-Bu),

starting from [N₃N_F]Mo(OTf) (900 mg, 1.015 mmol), 0.5% Na/

Hg (4.67 g, 1.015 mmol Na), and a solution of 2,6-dimeth-

ylphenyl isocyanide (133 mg, 1.015 mmol) in THF (10 mL).

Orange crystals (605 mg 0.70 mmol, 69%) were collected and

dried in vacuo after crystallization from 4 mL of dichlo-

romethane overnight at -40 °C: ¹H NMR δ 32.1 (br s, 2, H_m),

26.2 (br s, 6, CH₂), 6.4 (br s, 6, Ar Me), -22.7 (br s, 6, CH₂),

-27.9 (br s, 1, H_p); ¹⁹F NMR δ -72.0 (br s, 6, F_o), -141.3 (br

s, 3, F_p), -160.5 (s, 6, F_m); IR (Nujol) cm^-11777 (ν_NC). Anal.

Calcd for C₃₃H₂₁F₁₅N₅Mo: C, 45.64; H, 2.44; N, 8.06. Found:

C, 45.72; H, 2.40; N, 8.01.

BAr^F^-, starting from [N₃N_F]W(CNAr) (287 mg, 0.3 mmol) and

4

[Cp₂Fe]BAr^F₄(315 mg, 0.3 mmol), yielding 453 mg (0.25 mmol,

83%) of product as red crystals: ¹H NMR (CDCl₃) δ 46.51(s,

6, Ar Me), 41.12 (s, 2, meta), 7.39 (s, 4, BAr^Fpara), 7.15 (s, 8,

4

BAr^F₄ortho), -27.8 (br s, 6, CH₂), -55.2 (br s, 6, CH₂), -70.56

(s, 1, para); ¹⁹F NMR (CDCl₃) δ -62.8 (s, 24, BAr^F₄) -105.6

(br s, 6, F_m), -148.3 (br s, 3, F_p); IR (Nujol) cm^-12066 (ν_NC);

µ_eff) 2.8 µ_B(Evans method). Anal. Calcd for C₆₅H₃₃BF₃₉N₅W:

C, 42.91; H, 1.83; N, 3.85. Found: C, 43.04; H, 1.91; N, 3.96.

{[N₃N_F]Mo(CN-t-Bu )}BAr ^F₄. This green crystalline com-

plex was synthesized in a manner similar to that used to

prepare {[N₃N_F]W(CN-t-Bu)}BAr^F₄, starting from [N₃N_F]Mo-

(CN-t-Bu) (328 mg, 0.4 mmol) and [FeCp₂]BAr^F(420 mg, 0.4

4

mmol): yield 591 mg (0.35 mmol, 88%). No pentane was

required for crystallization: ¹H NMR (CDCl₃) δ 7.8 (br s, t-Bu),

7.61 (s, 4, BAr^F₄H_o), 7.48 (s, 8, BAr^F₄H_p), -20.2 (br s, 6, CH₂),

-80.7 (br s, 6, CH₂); ¹⁹F NMR (CDCl₃) δ -63.1 (s, BAr^F₄) -82.5

[N₃N_F]W(CNAr ). A 10 mL reaction vial was charged with

[N₃N_F]W(OTf) (714 mg, 0.73 mmol) and 0.5% Na/Hg (3.37 g,

0.73 mmol of Na). A solution of 2,6-dimethylphenyl isocyanide

(96 mg, 0.73 mmol) in THF (10 mL) was added, and the

reaction mixture was stirred vigorously for 1 h. All of the solid

triflate dissolved to give a red solution. THF was removed in

vacuo, and the residue was dissolved in dichloromethane. Na-

(br s, F_m), -154.5 (br s, F_p); IR (Nujol) cm^-12184 (ν_NC); µ_eff

)

3.1 µ_B(Evans method). Anal. Calcd for C₆₁H₃₃BF₃₉N₅Mo: C,

43.52; H, 1.98; N, 4.16. Found: C, 43.38; H, 2.08; N, 3.90.

{[N₃N_F]Mo(CNAr )}BAr ^F₄‚CH₂Cl₂. This complex was syn-

thesized in a manner similar to that used to prepare [N₃N_F]-

Mo(CN-t-Bu)}BAr^F₄, starting from [N₃N_F]Mo(CNAr) (304 mg,

1148 Organometallics, Vol. 19, No. 6, 2000

Greco et al.

0.35 mmol) and [FeCp₂]BAr^F(367 mg, 0.35 mmol): yield 513

Bu)₂}OTf, starting from [N₃N_F]Mo(OTf) (443 mg, 0.5 mmol)

and a solution of tert-butyl isocyanide (125 mg, 1.5 mmol) in

THF (8 mL). No color changes were observed during the course

of reaction. The orange product (303 mg, 0.28 mmol, 57%) was

collected, washed with ether, and dried in vacuo: ¹H NMR

(CDCl₃, 0 °C) δ 4.06 (br s, 6, CH₂), 3.65 (br s, 6, CH₂), 1.15 (br

s, 18, t-Bu); ¹³C NMR (CDCl₃) δ 144.57 (C₆F₅), 142.67 (C₆F₅),

138.19 (C₆F₅), 136.17 (C₆F₅), 58.45 (CH₂), 56.76 (CH₂), 30.71

(t-Bu), 29.67 (t-Bu); ¹⁹F NMR (CDCl₃) δ -78.80 (s, 3, OTf),

-147.98 (br s, 6, F_o), -159.07 (br s, 3, F_p), -162.92 (br s, 6,

F_m). IR (Nujol) cm^-12162, 2136 (ν_NC). Anal. Calcd for

4

mg (0.28 mmol, 81%) of green crystals. The product crystallizes

immediately upon formation, and 1 equiv of dichloromethane

is present in the lattice: ¹H NMR (CDCl₃) δ 38.8 (s, 6, Ar Me),

36.9 (s, 2, H_m), 7.68 (s, 8, BAr^FH_o), 7.56 (s, 4, BAr^FH_p), 5.30

4

(CH₂Cl₂), -21.0 (br s, 6, CH₂), -44.01 (s, 1, H_p), -81.2 (br s,

6, CH₂); ¹⁹F NMR (CDCl₃) δ -62.7 (s, 24, BAr^F₄) -89.1 (br s,

6, F_m), -150.3 (br s, 3, F_p); IR (Nujol) cm^-12133 (ν_NC); µ_eff

)

3.3 µ_B(Evans method). Anal. Calcd for C₆₆H₃₅BCl₂F₃₉N₅Mo:

C, 43.64; H, 1.94; N, 3.86. Found: C, 43.67; H, 2.06; N, 3.79.

{[N₃N_F]W(CN-t-Bu )₂}OTf. (a ) F r om [N₃N_F]W(CN-t-Bu ).

A solution of [N₃N_F]W(CN-t-Bu) (136 mg, 0.15 mmol, in THF

(5 mL)) was cooled to -40 °C. Ferrocenium triflate (50 mg,

0.15 mmol) was added as a solid, and the reaction mixture

was warmed to room temperature with stirring. The color

turned from orange to deep red as soon as the [FeCp₂]OTf

dissolved. Within 5 min, yellow solid [N₃N_F]W(OTf) began to

precipitate out. [N₃N_F]W(OTf) (68 mg, 0.07 mmol, 47%) of

triflate was collected by filtration. The mother liquor was

concentrated to dryness and extracted with ether in order to

remove ferrocene. The insoluble product (78 mg, 0.074 mmol,

49%) was collected and washed several times with ether: ¹H

NMR (CDCl₃) δ 4.09 (t, 6, CH₂), 3.76 (t, 6, CH₂), 1.09 (s, 18,

t-Bu); ¹³C NMR (CDCl₃) δ 157.33 (WCtN), 144.02 (C₆F₅),

142.11 (C₆F₅) 140.34 (C₆F₅), 138.48 (C₆F₅), 134.96 (C₆F₅), 63.71

(CH₂), 59.88 (t-BuC), 53.93 (CH₂), 30.22 (t-BuMe); ¹⁹F NMR

(CDCl₃) δ -78.80 (s, 3, OTf), -147.93 (s, 6, F_o), -158.68 (t, 3,

F_p), -162.09 (s, 6, F_m); IR (Nujol) cm^-12111 and 2104 (ν_NC).

Anal. Calcd for C₃₅H₃₀F₁₈N₆O₃SW: C, 36.86; H, 2.65; N, 7.37.

Found: C, 37.08; H, 2.78; N, 7.46.

(b) F r om [N₃N_F]W(OTf) a n d ter t-Bu tyl Isocya n id e.

[N₃N_F]W(OTf) (779 mg, 0.8 mmol) was added slowly as a solid

to a solution of tert-butyl isocyanide (140 mg, 1.68 mmol) in

THF (10 mL). The solution initially turned green, but it

became dark orange upon addition of all of the isocyanide. The

reaction was stirred for 30 min before THF was removed in

vacuo. The residue was extracted with ether, and the insoluble

product (801 mg, 0.702 mmol, 88%) was collected, washed with

ether, and dried in vacuo.

{[N₃N_F]W(CNAr )₂}OTf. [N₃N_F]W(OTf) (779 mg, 0.8 mmol)

was added as a solid to a solution of 2,6-dimethylphenyl

isocyanide (210 mg, 1.6 mmol) in THF (8 mL). The solution

turned red, and all of the triflate dissolved. After 30 min,

pentane (4 mL) was added in order to precipitate the product

as a green powder (817 mg, 0.66 mmol, 83%), which was

collected, washed with ether and pentane, and dried in

vacuo: ¹H NMR (CDCl₃) δ 7.20 (t, 2, H_p), 7.07 (d, 4, H_m), 4.18

(s, 6, CH₂), 3.92 (s, 6, CH₂), 2.12 (br s, 12, Me_o); ¹³C NMR

(CDCl₃) δ 174.70 (WCtN), 142.45 (d, C_o, J _CF) 251), 138.97

(d, C_p, J _CF) 257), 137.28 (d, C_m, J _CF) 257), 134.50 (br s, C_ipso),

134.62 (Ar), 130.75 (Ar), 128.47 (Ar), 125.73 (Ar), 62.96 (CH₂),

54.20 (CH₂), 17.42 (ArCH₃); ¹⁹F NMR (CDCl₃) δ -78.81 (s, 3,

OTf), -146.88 (s, 6, F_o), -158.31 (t, 3, F_p), -162.53 (s, 6, F_m);

IR (Nujol) cm^-12096, 2058 (ν_NC). Anal. Calcd for C₄₃H₃₀F₁₈N₆O₃-

SW: C, 41.74; H, 2.45; N, 6.80. Found: C, 41.79; H, 2.36; N,

6.70.

C

₃₅H₃₀F₁₈N₆O₃SMo: C, 39.94; H, 2.87; N, 7.98. Found: C,

39.83; H, 2.94; N, 7.99.

{[N₃N_F]Mo(CNAr )₂}OTf. This complex was synthesized in

a manner similar to that used to prepare {[N₃N_F]W(CNAr)₂}-

OTf, starting from [N₃N_F]Mo(OTf) (709 mg, 0.8 mmol) and 2,6-

dimethylphenyl isocyanide (315 mg, 2.4 mmol). The product

(589 mg, 0.51 mmol, 64%) was isolated as a yellow powder.

¹H NMR (CDCl₃, 0 °C) δ 7.16 (t, 2, H_p), 7.05 (d, 4, H_m), 4.28 (s,

6, CH₂), 3.97 (s, 6, CH₂), 2.01 (s, 12, Me_o); ¹³C NMR (CDCl₃) δ

172.38 (MoCtN), 141.83 (d, C_o, J _CF) 249), 138.53 (d, C_p, J _CF

) 255), 137.32 (d, C_m, J _CF) 253), 134.89 (br s, C_ipso), 134.28

(Ar), 131.09 (Ar), 128.58 (Ar), 124.96 (Ar), 63.36 (CH₂), 54.28

(CH₂), 17.49 (ArCH₃); ¹⁹F NMR (CDCl₃) δ -78.86 (s, 3, OTf),

-147.28 (s, 6, F_o), -158.24 (t, 3, F_p), -162.44 (s, 6, F_m); IR

(Nujol) cm^-12116, 2095 (ν_NC). Anal. Calcd for C₄₃H₃₀F₁₈N₆O₃-

SMo: C, 44.96; H, 2.63; N, 7.32. Found: C, 45.11; H, 2.57; N,

7.21.

{[N₃N_F]W(CN-t -Bu )₃}OTf. [N₃N_F]W(OTf) (390 mg, 0.4

mmol) was added as a solid to a stirred solution of tert-butyl

isocyanide (133 mg, 1.6 mmol) in THF (5 mL). The reaction

mixture turned green immediately, and all triflate dissolved

within 5 min. The mixture was stirred for 15 min, and 3 mL

of pentane was added in order to precipitate the lime green

product, which was collected, washed with ether and pentane,

and dried in vacuo: yield 421 mg (0.34 mmol, 86%). Analyti-

cally pure material was obtained by recrystallization from

dichloromethane and pentane in the presence of excess iso-

cyanide: ¹H NMR (CDCl₃, -20 °C, 500 MHz) δ 4.21 (s, 2), 4.08

(m, 2), 3.89 (m, 2), 3.54 (m, 4), 3.27 (s, 2), 1.68 (s, 9, t-Bu),

1.07 (s, 18, t-Bu); ¹³C NMR (CDCl₃) δ 150.49 (WCtN), 146.04

(C₆F₅), 144.41 (C₆F₅), 144.14 (C₆F₅), 142.45 (C₆F₅), 140.32

(C₆F₅), 139.20 (C₆F₅), 138.27 (C₆F₅), 137.02 (C₆F₅), 135.44

(C₆F₅), 68.70 (CH₂), 64.45 (CH₂), 60.11 (CH₂), 59.23 (CH₂),

59.06 (CH₂), 58.19 (CH₂), 31.41 (t-Bu), 30.49 (t-Bu); ¹⁹F NMR

(THF, 470 MHz) δ -78.80 (s, 3, (OTf)), -145.58 (br s, 2, F_o),

-145.82 (br s, 2, F_o), -147.76 (br s, 2, F_o), -163.25 (t, 2, F_m),

-165.03 (t, 4, F_m), -166.30 (t, 2, F_p), -167.47 (t, 1, F_p); ¹⁹F

NMR (CDCl₃) δ -146.38 (br s, 2, F_o), -147.53 (d, 2, F_o),

-148.90 (br s, 2, F_o), -161.39 (t, 2, F_m), -163.49 (t, 2, F_m),

-164.23 (t, 2, F_m), -165.52 (br s, 3, F_p); IR (Nujol) cm^-12178,

2145 (ν_NC). Anal. Calcd for C₄₀H₃₉F₁₈N₇O₃SW: C, 39.26; H,

3.21; N, 8.01. Found: C, 39.06; H, 3.29; N, 7.88.

{[N₃N_F]W(CN-t-Bu )₃}BP h ₄. A solution of tert-butyl isocya-

nide (37 mg, 0.45 mmol) in THF (4 mL) was added to solid

{[N₃N_F]W(CN-t-Bu)}BPh₄(184 mg, 0.15 mmol), which dis-

solved as it reacted to give a green solution. The solution was

cooled to -40 °C, which resulted in the crystallization of green

{[N₃N_F]W(CNAr )₂}BAr ^F₄. 2,6-Dimethylphenyl isocyanide

(20 mg, 0.152 mmol) was added to a solution of {[N₃N_F]W-

(CNAr)}BAr^F₄(182 mg, 0.1 mmol) in CH₂Cl₂(4 mL). The color

changed immediately from red to yellow. After removal of CH₂-

Cl₂, the residue was dissolved in ether. Addition of pentane

resulted in the precipitation of the product as a yellow powder

(153 mg, 0.078 mmol, 78%), which was collected, washed with

pentane, and dried in vacuo: ¹H NMR (CDCl₃) δ 7.70 (br s, 8,

BAr^Fortho), 7.52 (br s, 4, BAr^Fpara), 7.16 (t, 2, H_p), 7.05 (d,

1

product (210 mg, 0.15 mmol, 100%); H NMR (CDCl₃, -3 °C,

500 MHz) δ 7.36 (br s, 8, BPh₄ortho), 7.01 (t, 8, BPh₄meta),

6.87 (t, 4, BPh₄para), 4.04 (s, 2), 3.66 (m, 2), 3.10 (m, 2), 2.88

(m, 2), 2.78 (br s, 4), 1.62 (s, 9, t-Bu), 1.00 (s, 18, t-Bu); ¹⁹F

NMR (THF) δ -144.94 (br s, 2, F_o), -145.85 (d, 2, F_o), -147.47

(br s, 2, F_o), -162.22 (t, 2, F_m), -164.10 (t, 2, F_m), -164.38 (t,

2, F_m), -165.60 (t, 2, F_p), -166.44 (t, 1, F_p); ¹⁹F NMR (CDCl₃)

δ -144.41 (br s, 2, F_o), -146.17 (d, 2, F_o), -147.24 (br s, 2, F_o),

-159.45 (t, 2, F_m), -161.51 (t, 2, F_m), -162.38 (t, 2, F_m),

-163.59 (br s, 3, F_p); IR (Nujol) cm^-12175, 2140 (ν_NC).

[N₃N_F]W(C₂H₄). A 100 mL round-bottomed flask was

charged with [N₃N_F]W(OTf) (500 mg, 0.513 mmol), sodium

amalgam (2.60 g, 0.564 mmol of Na), and THF (50 mL). It was

4

4, H_m), 4.15 (s, 6, CH₂), 3.48 (s, 6, CH₂), 2.01 (br s, 12, Me_o);

¹⁹F NMR (CDCl₃) δ -62.66 (s, 24, BAr^F₄), -146.90 (s, 6, F_o),

-156.18 (t, 3, F_p), -160.95 (s, 6, F_m); IR (Nujol) cm^-12112,

2072 (ν_NC).

{[N₃N_F]Mo(CN-t-Bu )₂}OTf. This complex was synthesized

in a manner similar to that used to prepare {[N₃N_F]W(CN-t-

Triamidoamine Complexes of Mo and W

Organometallics, Vol. 19, No. 6, 2000 1149

fitted with a vacuum adapter, sealed, and attached to a high-

vacuum line. After degassing by freeze-pump-thawing, eth-

ylene (∼40 mmol) was introduced by vacuum transfer. The

reaction vessel was sealed, and the contents were warmed to

room temperature and stirred for 1 h. The solution was

decanted off the amalgam, filtered, concentrated to dryness,

and extracted with CH₂Cl₂. The brown product was recrystal-

lized from dichloromethane by layering a concentrated solution

with pentane and storing the sample at -40 °C for 15 h: yield

attached to a Bruker SMART/CCD diffractometer. A total of

15 746 reflections were collected, of which 5147 were deter-

mined to be unique. Integration of greater than a half-

hemisphere of data using the SAINT program revealed

monoclinic Laue symmetry. Systematic absences indicated

P2₁/c as the space group. Solution (direct methods) and

refinement of the structure was performed with the ShelXTL

set of programs. Only W, V, O, N, and F atoms were refined

anisotropically; hydrogen atoms were placed in an idealized

position and refined using a riding model. Crystallographic

details are provided in Table 2 and selected interatomic

distances and angles in Table 6.

346 mg (79%) in two crops; ¹⁹F NMR δ -100 (v br s, ∆_1/2

)

2,500, 6, F_o), -137 (br s, ∆_1/2) 650, 6, F_m), -152.1 (br s, ∆_1/2

) 140, 3, F_p); µ_eff) 1.8 µ_B(Evans method). Anal. Calcd for

C

₂₆H₁₆N₄F₁₅W: C, 36.60; H, 1.89; N, 6.57. Found: C, 36.54;

X-r a y Str u ctu r e of [N₃N_F]W(CN-t-Bu ). An orange crystal

was mounted in oil and placed in a cold stream of nitrogen

attached to a Bruker SMART/CCD diffractometer. A total of

9917 reflections were collected, of which 4215 were determined

to be unique. Integration of greater than a half-hemisphere

of data using the SAINT program revealed monoclinic Laue

symmetry. Systematic absences indicated P2₁/c as the space

group. Solution (direct methods) and refinement of the struc-

ture was performed with ShelXTL set of programs. All non-

hydrogen atoms were refined anisotropically; hydrogen atoms

were placed in idealized positions and refined using a riding

model. Crystallographic details are provided in Table 2 and

selected interatomic distances and angles in Table 6.

X-r a y Str u ctu r e of {[N₃N_F]W(CN-t-Bu )₃}BP h ₄. A green

crystal was mounted in oil and placed in a cold stream of

nitrogen attached to a Bruker SMART/CCD diffractometer. A

total of 29 930 reflections were collected, of which 10 559 were

determined to be unique. An empirical absorption correction

from ψ-scans was applied. Integration of greater than a half-

hemisphere of data using the SAINT program revealed mono-

clinic Laue symmetry. Systematic absences indicated P2₁/c as

the space group. Solution (direct methods) and refinement of

the structure was performed with the ShelXTL set of pro-

grams. All non-hydrogen atoms were refined anisotropically;

hydrogen atoms were placed in idealized positions and refined

using a riding model. Three molecules of THF were found in

the asymmetric unit. Crystallographic details are provided in

Table 4 and selected interatomic distances and angles in Table

7.

H, 2.03; N, 6.36.

{[N₃N_F]W(C₂H₄)}OTf. Ferrocenium triflate (83 mg, 0.23

mmol) was added as a solid to a solution of [N₃NF]W(C₂H₄)

(200 mg, 0.234 mmol) in 8 mL of THF. The solution turned

deep red instantly. After 15 min, the solution was filtered and

the THF was removed in vacuo. The ferrocene was sublimed

away from the product onto a -78 °C probe. The solid which

remained was recrystallized from dichloromethane by addition

of pentane to give the product as a red solid: yield 215 mg

(91%); ¹H NMR δ 4.42 (br s, 6, NCH₂CH₂N), 3.96 (br s, 6,

NCH₂CH₂N), 3.10 (s, 4, C₂H₄); ¹⁹F NMR (CDCl₃) δ -78 (br s,

3, (OTf)), -143.7 (s, 6, F_o), -152.7 (s, 3, F_p), -159.8 (s, 6, F_m).

Anal. Calcd for C₂₇H₁₆N₄F₁₈O₃SW: C, 32.35; H, 1.61; N, 5.59.

Found: C, 32.53; H, 1.63; N, 5.46.

X-r a y Str u ctu r e of [N₃N]Mo(CN). A yellow crystal was

mounted in oil and placed in a cold stream of nitrogen attached

to a Bruker SMART/CCD diffractometer. A total of 11 177

reflections were collected, of which 2052 were determined to

be unique. Integration of greater than a half-hemisphere of

data using the SAINT program revealed tetragonal Laue

symmetry. Systematic absences indicated P4h2₁m as the space

group. Solution (direct methods) and refinement of the struc-

ture was performed with the ShelXTL set of programs. All non-

hydrogen atoms were refined anisotropically; hydrogen atoms

were placed in idealized positions and refined using a riding

model. A 0.5 equiv amount of ether was found in the unit cell.

Crystallographic details are provided in Table 2 and selected

interatomic distances and angles in Table 3.

X-r a y Str u ctu r e of {[N₃N_F]W(CO)₂}Na (eth er )₃. A purple

crystal was mounted in oil and placed in a cold stream of

nitrogen attached to a Bruker SMART/CCD diffractometer. A

total of 9266 reflections were collected, of which 6264 were

determined to be unique. An empirical absorption correction

from ψ-scans was applied. Integration of greater than a half-

hemisphere of data using the SAINT program revealed triclinic

Laue symmetry and P1h as the space group. Solution and

refinement of the structure was performed with the ShelXTL

set of programs. Patterson methods were employed to locate

the tungsten atom, while subsequent difference Fourier cal-

culations revealed the positions of the remaining non-hydrogen

atoms. All non-hydrogen atoms were refined anisotropically;

hydrogen atoms were placed in idealized positions and refined

using a riding model. Disorder in one arm of one of the

coordinated ether molecules was modeled over two positions.

Crystallographic details are provided in Table 4 and selected

interatomic distances and angles in Table 5.

Ack n ow led gm en t. R.R.S. is grateful to the National

Institutes of Health (Grant No. GM 31978) for research

support. G.E.G. thanks Pete Bonitatebus for mounting

and collecting data on the crystal of {[N₃N_F]W(CN-t-

Bu)₃}BPh₄, J onathan Goodman for help in solving the

structure of {[N₃N_F]W(CO)₂}Na(ether)₃, and J ane Brock

for helpful discussions. We also thank the National

Science Foundation for funds to help purchase a de-

partmental Bruker SMART/CCD diffractometer.

Su p p or tin g In for m a tion Ava ila ble: Tables of crystal

data and structure refinement, atomic coordinates, bond

lengths and angles, anisotropic displacement parameters, and

torsion angles for [N₃N]Mo(CN), {[N₃N_F]W(CO)₂}Na(ether)₃,

[N₃N_F]W(CO)V(Mes)₃, [N₃N_F]W(CN-t-Bu), and {[N₃N_F]W(CN-

t-Bu)₃}BPh₄. This material is available free of charge via the

Internet at http://pubs.acs.org.

X-r a y Str u ctu r e of [N₃N_F]W(CO)V(Mes)₃. A black crystal

was mounted in oil and placed in a cold stream of nitrogen

OM990748U

Article Doi

Synthesis of [(Me3SiNCH2CH2)3N]3- and [(C6F5NCH2CH2)3N] 3- complexes of molybdenum and tungsten that contain CO, isocyanides, or ethylene

DOI: 10.1021/om990748u

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om990748u

Full text of DOI:10.1021/om990748u

Products guided by the article

R&D Labs maybe for 262854-64-8

Relevant to this article

Hot Product