Synthons for Coordinatively Unsaturated Complexes of Tungsten, and Their Use for the Synthesis of High Oxidation-State Silylene Complexes

Article abstract of DOI:10.1021/ja030548g

Reduction of Cp*WCl₄ afforded the metalated complex (η⁶-C₅Me₄CH₂)(dmpe)W(H)Cl (1) (Cp* = C₅Me₅, dmpe = 1,2-bis(dimethylphosphino)ethane). Reactions with CO and H₂ suggested that 1 is in equilibrium with the 16-electron species [Cp*(dmpe)WCl], and 1 was also shown to react with silanes R ₂SiH₂ (R₂ = Ph₂ and PhMe) to give the tungsten(IV) silyl complexes Cp*(dmpe)(H)(Cl)W(SiHR₂) (6a, R₂ = Ph₂; 6b, R₂ = PhMe). Abstraction of the chloride ligand in 1 with LiB(C₆F₅)₄ gave a reactive species that features a doubly metalated Cp* ligand, [(η ⁷-C₅Me₃(CH₂) ₂)(dmpe)W(H)₂][B(C₆F₅)₄] (4). In its reaction with dinitrogen, 4 behaves as a synthon for the 14-electron fragment [Cp*(dmpe)W]⁺, to give the dinuclear dinitrogen complex {[Cp*(dmpe)W]₂(μ-N₂)}{B(C ₆F₅)₄}₂ (5). Hydrosilanes R ₂SiH₂ (R₂ = Ph₂, PhMe, Me ₂, Dipp(H); Dipp = 2,6-diisopropylphenyl) were shown to react with 4 in double Si-H bond activation reactions to give the silylene complexes [Cp*(dmpe)H₂W=SiR₂][B(C₆F ₅)₄] (8a-d). Compounds 8a,b (R₂ = Ph ₂ and PhMe, respectively) were also synthesized by abstraction of the chloride ligands from silyl complexes 6a,b. Dimethylsilylene complex 8c was found to react with chloroalkanes RCI (R = Me, Et) to liberate trialkylchlorosilanes RMe₂SiCl. This reaction is discussed in the context of its relevance to the mechanism of the direct synthesis for the industrial production of alkylchlorosilanes.

Full text of DOI:10.1021/ja030548g

Published on Web 03/16/2004
Synthons for Coordinatively Unsaturated Complexes of
Tungsten, and Their Use for the Synthesis of High
Oxidation-State Silylene Complexes
Benjamin V. Mork and T. Don Tilley*
Contribution from the Department of Chemistry, UniVersity of California, Berkeley,
Berkeley, California 94720-1460
Received September 22, 2003; E-mail: tdtilley@socrates.berkeley.edu
Abstract: Reduction of Cp*WCl4 afforded the metalated complex (η6-C5Me4CH2)(dmpe)W(H)Cl (1) (Cp* )
C5Me5, dmpe ) 1,2-bis(dimethylphosphino)ethane). Reactions with CO and H2 suggested that 1 is in
equilibrium with the 16-electron species [Cp*(dmpe)WCl], and 1 was also shown to react with silanes
R2SiH2 (R2 ) Ph2 and PhMe) to give the tungsten(IV) silyl complexes Cp*(dmpe)(H)(Cl)W(SiHR2) (6a, R2
) Ph2; 6b, R2 ) PhMe). Abstraction of the chloride ligand in 1 with LiB(C6F5)4 gave a reactive species that
features a doubly metalated Cp* ligand, [(η7-C5Me3(CH2)2)(dmpe)W(H)2][B(C6F5)4] (4). In its reaction with
dinitrogen, 4 behaves as a synthon for the 14-electron fragment [Cp*(dmpe)W]+, to give the dinuclear
dinitrogen complex {[Cp*(dmpe)W]2(µ-N2)}{B(C6F5)4}2 (5). Hydrosilanes R2SiH2 (R2 ) Ph2, PhMe, Me2,
Dipp(H); Dipp ) 2,6-diisopropylphenyl) were shown to react with 4 in double Si-H bond activation reactions
to give the silylene complexes [Cp*(dmpe)H2WdSiR2][B(C6F5)4] (8a-d). Compounds 8a,b (R2 ) Ph2 and
PhMe, respectively) were also synthesized by abstraction of the chloride ligands from silyl complexes 6a,b.
Dimethylsilylene complex 8c was found to react with chloroalkanes RCl (R ) Me, Et) to liberate
trialkylchlorosilanes RMe2SiCl. This reaction is discussed in the context of its relevance to the mechanism
of the direct synthesis for the industrial production of alkylchlorosilanes.
Introduction
and diaryl silylene complexes have been synthesized, and these
feature ruthenium,3 osmium,4 iridium,5 and platinum6 in rela-
Transition-metal silylene complexes are of interest as silicon
analogues of metal carbenes, and as possible intermediates in a
number of metal-catalyzed transformations involving organo-
silicon compounds.1 In metal carbene chemistry, it is well
established that the reactivity and electronic structure of the CR2
ligand (R ) H, alkyl, or aryl) is highly dependent on the nature
of the metal fragment to which it is bound.2 Late transition-
metal carbene complexes are typically electrophilic at carbon,
while early metal centers often give rise to nucleophilic carbene
ligands. To date, a number of base-free transition-metal dialkyl
tively high dn configurations (n g 6). In general, these silylene
complexes have been shown to be very electrophilic at silicon.
Thus, it is of interest to investigate silylene complexes involving
early transition-metal centers with low dn configurations. Such
species may exhibit novel chemical properties for the metal
silylene fragment, opening pathways to new transformations for
organosilicon compounds.
Our efforts to synthesize base-free silylene complexes of the
more electropositive early transition elements initially focused
on the group 6 metals, and herein we report the synthesis and
study of silylene complexes of the type [Cp*(dmpe)(H)2Wd
SiR2][B(C6F5)4] (Cp* ) η5-C5Me5, dmpe ) Me2PCH2CH2PMe2,
R2 ) Ph2, Me2, PhMe, Dipp(H); Dipp ) 2,6-diisopropylphenyl).
These compounds were prepared with the use of new, reactive
tungsten complexes featuring metalated Cp* ligands, and the
synthesis of this class of silylene complexes was communicated
previously.7 Ueno, Ogino, and co-workers have also recently
(1) (a) Tilley, T. D. In The Silicon-Heteroatom Bond; Patai, S., Rappoport, Z.,
Eds.; Wiley: New York, 1991; p 245. (b) Tilley, T. D. In The Chemistry
of Organic Silicon Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New
York, 1989; p 1415. (c) Tilley, T. D. Comments Inorg. Chem. 1990, 10,
37. (d) Zhang, Z. Y.; Sanchez, R.; Pannell, K. H. Organometallics 1995,
14, 2605. (e) Sharma, H. K.; Pannell, K. H. Chem. ReV. 1995, 95, 1351.
(f) Pannell, K. H.; Cervantes, J.; Hernandez, C.; Cassias, J.; Vincenti, S.
Organometallics 1986, 5, 1056. (g) Pannell, K. H.; Rozell, J. M.; Hernandez,
C. J. Am. Chem. Soc. 1989, 111, 4482. (h) Pannell, K. H.; Wang, L. J.;
Rozell, J. M. Organometallics 1989, 8, 550. (i) Tobita, H.; Ueno, K.; Ogino,
H. Bull. Chem. Soc. Jpn. 1988, 61, 2797. (j) Ueno, K.; Tobita, H.; Ogino,
H. Chem. Lett. 1990, 369. (k) Haynes, A.; George, M. W.; Haward, M. T.;
Poliakoff, M.; Turner, J. J.; Boag, N. M.; Green, M. J. Am. Chem. Soc.
1991, 113, 2011. (l) Tanaka, Y.; Yamashita, H.; Tanaka, M. Organome-
tallics 1995, 14, 530. (m) Mitchell, G. P.; Tilley, T. D.; Yap, G. P. A.;
Rheingold, A. L. Organometallics 1995, 14, 5472. (n) Mitchell, G. P.;
Tilley, T. D. Organometallics 1996, 15, 3477. (o) Tamao, K.; Sun, G. R.;
Kawachi, A. J. Am. Chem. Soc. 1995, 117, 8043.
(3) Grumbine, S. K.; Mitchell, G. P.; Straus, D. A.; Tilley, T. D.; Rheingold,
A. L. Organometallics 1998, 17, 5607.
(4) Wanandi, P. W.; Glaser, P. B.; Tilley, T. D. J. Am. Chem. Soc. 2000, 122,
972.
(5) (a) Peters, J. C.; Feldman, J. D.; Tilley, T. D. J. Am. Chem. Soc. 1999,
121, 9871. (b) Klei, S. R.; Tilley, T. D.; Bergman, R. G. J. Am. Chem.
Soc. 2000, 122, 1816.
(2) (a) Crabtree, R. H. The Organometallic Chemistry of the Transition Metals,
2nd ed.; Wiley-Interscience: New York, 1994. (b) 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. (c) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple
Bonds; Wiley-Interscience: New York, 1988.
(6) (a) Feldman, J. D.; Mitchell, G. P.; Nolte, J. O.; Tilley, T. D. J. Am. Chem.
Soc. 1998, 120, 11184. (b) Mitchell, G. P.; Tilley, T. D. Angew. Chem.,
Int. Ed. 1998, 37, 2524.
(7) Mork, B. V.; Tilley, T. D. J. Am. Chem. Soc. 2001, 123, 9702.
9
10.1021/ja030548g CCC: $27.50 © 2004 American Chemical Society
J. AM. CHEM. SOC. 2004, 126, 4375-4385
4375

A R T I C L E S
Mork and Tilley
reported a low-valent, base-free tungsten silylene complex,
Cp*W(CO)2(dSiMes2)(SiMe3).8
We have been interested in defining the reactivity patterns
for these new high oxidation-state silylene complexes and
making comparisons to those observed for their late metal
counterparts. Our studies have shown that these compounds,
like late metal silylenes, feature highly Lewis-acidic silicon
centers. However, reactions with chloroalkanes have produced
the first example of insertion of a metal-bound silylene into a
C-Cl bond to liberate a trialkylchlorosilane. This homogeneous
reaction demonstrates a proposed step in the direct synthesis,
the metal-catalyzed heterogeneous reaction that is the primary
industrial source of organosilanes.9
Figure 1. ORTEP diagram of Cp*-metalated complex 1.
Table 1. Selected Distances (Å) and Angles (deg) for 1
Results and Discussion
Bond Distances
W-P1
W-P2
W-Cl
W-C1
W-C2
2.405(2)
2.464(2)
2.522(2)
2.338(8)
2.16(1)
W-C3
W-C4
W-C5
W-C6
2.316(8)
2.395(9)
2.316(8)
2.344(9)
We have previously established routes to platinum and iridium
silylene complexes that involve activation of two silicon-
hydrogen bonds of a hydrosilane, via oxidative addition and
subsequent R-elimination.5,6b This route requires access to
unsaturated metal centers. For example, a 14-electron metal
fragment is required for formation of an 18-electron silylene
dihydride complex directly from a hydrosilane (eq 1). Given
the promise of this silylene-extrusion reaction as a general route
to metal silylene complexes, we sought to synthesize d0
examples via reactions of hydrosilanes with coordinatively
unsaturated but inherently electron-rich fragments of the type
[Cp*L2W]+.10
Bond Angles
P1-W-P2
P1-W-C6
P1-W-Cl
Cl-W-C6
81.38(8)
90.6(2)
85.74(7)
81.5(2)
P2-W-Cl
P2-W-C6
W-C6-C1
78.25(7)
158.6(2)
64.1(5)
The 1H NMR spectrum of 1 in benzene-d6 is consistent with
a low-symmetry structure. Four individual doublet resonances
are observed for the dmpe methyl groups at δ 0.98, 1.23, 1.29,
and 1.53, and the intact ring methyl groups resonate separately
at δ 2.12, 2.07, 2.06, and 1.82. The 31P{1H} NMR spectrum of
1 features two resonances at δ 10.8 (JPW ) 233 Hz) and 18.6
(JP′W ) 253 Hz), confirming the binding of the dmpe ligand to
a low-symmetry metal center. The structure of 1 was confirmed
by X-ray crystallography, and an ORTEP diagram of the
molecule is shown in Figure 1. The geometry of 1 in the solid
state supports the C1 symmetry observed for the complex by
solution NMR spectroscopy, and the binding of the (η6-C5Me4-
CH2) ligand is reminiscent of that observed by Legzdins and
co-workers for (η6-C5Me4CH2)W(NO)(CH2CMe3)(PMe3).13,14
The π-bound fragment in 1 is best described as an η5-
cyclopentadienyl:η1-alkyl ligand, although it seems to exhibit
partial tetramethylfulvene character, having a shortened C1-
C6 bond length of 1.41(1) Å (intermediate between single and
double CC bond lengths). Selected bond distances and angles
from the crystal structure of 1 are listed in Table 1, and details
of the data collection are summarized in Table 2.
LnM + H2SiR2 f Ln(H)2MdSiR2
(1)
Tungsten Complexes Featuring Metalated Pentamethyl-
cyclopentadienyl Ligands. A 14-electron [Cp*L2W]+ cation
might be produced by halide ion abstraction from a formally
16-electron precursor of the type Cp*L2WCl. Complexes of this
type are rare, but Baker and co-workers have prepared Cp*-
(PMe3)(η2-Me2PCH2)W(H)Cl, which appears to be in equilib-
rium with Cp*(Me3P)2WCl.11 In an attempt to synthesize the
related complex Cp*(dmpe)WCl as a precursor to the [Cp*-
(dmpe)W]+ fragment, Cp*WCl412 was reduced in benzene with
3.0 equiv of Na/Hg (0.8% w/w) in the presence of dmpe (eq
2). The chelating diphosphine ligand was not metalated in the
reaction; however, an intramolecular C-H bond activation took
place at the Cp* ligand, to produce the hydrido chloride complex
(η6-C5Me4CH2)(dmpe)W(H)Cl (1). This reduction proceeded
over 16 h at 60 °C and resulted in isolation of 1 in 83% yield
after recrystallization from pentane.
By analogy to Cp*(PMe3)(η2-Me2PCH2)W(H)Cl, it seemed
likely that 1 would be in equilibrium with the 16-electron
intermediate Cp*(dmpe)WCl. In support of this, reaction of 1
with carbon monoxide at 70 °C over 24 h resulted in formation
of the adduct Cp*(dmpe)W(CO)Cl (2). Compound 2 was
isolated in 68% yield after recrystallization from Et2O, and its
(10) In this discussion, a d0 silylene complex is one in which invocation of two
metal-based electrons in bonding to the silylene ligand results in a d0
electron configuration.
(11) Baker, R. T.; Calabrese, J. C.; Harlow, R. L.; Williams, I. D. Organome-
tallics 1993, 12, 830.
(12) Murray, R. C.; Blum, L.; Liu, A. H.; Schrock, R. R. Organometallics 1985,
4, 954.
(8) Ueno, K.; Asami, S.; Watanabe, N.; Ogino, H. Organometallics 2002, 21,
1326.
(9) (a) Catalyzed Direct Reactions of Silicon; Lewis, K. M., Rethwisch, D.
G., Eds.; Elsevier: Amsterdam, 1993. (b) Clarke, M. P. J. Organomet.
Chem. 1989, 376, 165. (c) Walter, H.; Roewer, B.; Bohmmhammel, K. J.
Chem. Soc., Faraday Trans. 1996, 92, 4605. (d) Okamoto, M.; Onodera,
S.; Okano, T.; Suzuki, E.; Ono, Y. J. Organomet. Chem. 1997, 531, 67.
(13) Debad, J. D.; Legzdins, P.; Rettig, S. J.; Veltheer, J. E. Organometallics
1993, 12, 2714.
(14) For other examples of metalated Cp* compounds see: (a) Bercaw, J. E. J.
Am. Chem. Soc. 1974, 96, 5087. (b) Bulls, A. R.; Schaefer, W. P.; Serfas,
M.; Bercaw, J. E. Organometallics 1987, 6, 1219. (c) Schock, L. E.; Brock,
C. P.; Marks, T. J. Organometallics 1987, 6, 232.
9
4376 J. AM. CHEM. SOC. VOL. 126, NO. 13, 2004

Synthons for Complexes of Tungsten
A R T I C L E S
Table 2. Details of Crystallographic Data Collection
compound
1
4
5
6b
7
8c
empirical formula C16H31ClP2W
C40H31BF20P2W
1148.25
C46H35BF21N
1258.36
C23H42ClP2SiW
626.91
C35H50P2SiW
744.66
C42H39BF20P2SiW
1208.42
FW
504.66
crystal size (mm)
color
crystal system
space group
a (Å)
b (Å)
c (Å)
0.18 × 0.15 × 0.13 0.45 × 0.25 × 0.20 0.17 × 0.06 × 0.04 0.20 × 0.13 × 0.10 0.21 × 0.18 × 0.15 0.30 × 0.15 × 0.12
orange
orange
green
orange
yellow
orange
monoclinic
P21/c (No. 14)
8.7200(2)
16.6120(3)
13.9440(1)
90
102.536(1)
90
1971.73(6)
4
monoclinic
P21/c (No. 14)
15.2193(2)
15.9706(2)
17.2664(3)
90
96.322(1)
90
4171.27(9)
4
triclinic
monoclinic
P21/a (No. 14)
17.2867(2)
9.2357(2)
17.8766(4)
90
115.65(1)
90
2572.83
4
orthorhombic
Pbca (No. 61)
18.3293(1)
17.9586(4)
20.4990(1)
90
orthorhombic
Pca21 (No. 29)
27.4880(1)
15.5223(2)
21.3367(3)
90
P-1 (No. 2)
12.822(1)
14.878(1)
15.005(1)
114.902(1)
110.473(1)
94.868(1)
2340.1(1)
2
R (°)
â (°)
90
90
γ (°)
90
6747.6(2)
8
168(1)
TeXsan
90
9103.9(3)
8
155(1)
TeXsan
V (Å3)
Z
temp (K)
solution/
refinement
software
R
169(1)
TeXsan
153(1)
TeXsan
122(1)
SHELX-TL
142(1)
TeXsan
0.033
0.045
0.046
0.117
0.051
0.023
0.030
wR2
RW
Rall
0.037
0.055
1.41
0.042
0.067
1.39
0.069
0.082
1.42
0.022
0.087
0.65
0.037
0.036
1.47
0.063
1.08
GOF
Scheme 1
IR spectrum exhibits a CO stretching absorbance at 1789 cm-1
,
indicating that the metal center is quite electron-rich and strongly
π back-donating. This reaction suggests that the C-H bond
reductive elimination/oxidative addition equilibrium shown in
Scheme 1 is active for the “tucked Cp*” ligand in compound
1. The existence of this equilibrium was further evidenced by
the synthesis of the dihydride Cp*(dmpe)W(H)2Cl (3) via
reaction of 1 with excess dihydrogen at 90 °C. Reaction of 1
with deuterium gas (1 atm) at 110 °C over 10 days produced
exclusively the dideuteride complex Cp*(dmpe)W(D)2Cl (3-
Figure 2. ORTEP diagram of the cation in 4. Hydrogen atoms are removed
for clarity.
1
The H NMR spectrum of 4 in fluorobenzene/benzene-d6
(10:1) reveals a mirror-symmetric structure for the cation. Two
singlets are observed for the intact ring methyl groups at δ 1.85
(3H) and 1.68 (6H), and the diastereotopic ring methylene
groups exhibit a multiplet and a singlet at δ 2.64 and 1.77,
respectively. The resonance for the symmetry-equivalent tung-
sten hydride ligands is observed at δ -2.11, as a doublet of
doublets (with 183W satellites) due to coupling to two inequiva-
lent phosphorus nuclei (JHP ) 58 Hz, JHP′ ) 38 Hz, JHW ) 49
Hz). The spectroscopic properties of 4 are therefore consistent
with the structure depicted in eq 3, and this was confirmed by
X-ray crystallographic analysis.
1
2
d2), as shown by H and H NMR spectroscopy. These results
indicated that this equilibrium could be utilized in activation of
hydrosilanes by 1 to form tungsten-silicon bonds.
The prospect of Si-H bond activation by derivatives of
compound 1 prompted us to attempt the synthesis of a more
highly activated species, by abstraction of the chloride ligand
in 1. Reaction of 1 with the fluorinated borate salt Li(OEt2)3B-
(C6F5)4 in fluorobenzene under argon resulted in a quantitative
reaction within minutes and the precipitation of lithium chloride.
Spectroscopic characterization of the new orange complex
determined its identity to be the doubly metalated (or “doubly
tucked”) Cp* complex [(η7-C5Me3(CH2)2)(dmpe)W(H)2]-
[B(C6F5)4] (4, eq 3). The cation 4 is an isomer of the desired
14-electron cation Cp*(dmpe)W+, which was envisioned as a
“synthon” or synthetic equivalent of such a species.
The ion pair 4 was crystallized by liquid-liquid diffusion of
pentane into the product fluorobenzene solution at room
temperature over 2 d. In this manner, 4 was isolated as orange
crystals in 70% yield. An X-ray diffraction analysis was
performed on a crystal of 4, and an ORTEP diagram of the
cation is shown in Figure 2. The C5Me3(CH2)2 ligand in this
complex can be described as an η5-cyclopentadienyl dialkyl
moiety, and the binding of the C5 ring is “slipped” significantly
to accommodate the two W-C bonds to ring methylene carbons.
This is manifested in a range of W-Cring distances from 2.152(9)
to 2.474(9) Å. There is a slight shortening observed for the C3-
C8 and C4-C9 bonds attributable to a small amount of η3-
allyl:η4-butadiene character for the ligand. Similar geometric
9
J. AM. CHEM. SOC. VOL. 126, NO. 13, 2004 4377

A R T I C L E S
Mork and Tilley
Table 3. Selected Distances (Å) and Angles (deg) for the Cation
in 4
Bond Distances
W-P1
W-P2
W-Cl
W-C2
W-C3
W-C4
2.452(2)
2.450(2)
2.474(9)
2.338(8)
2.152(9)
2.16(1)
W-C5
W-C8
W-C9
C3-C8
C4-C9
2.35(1)
2.36(1)
2.34(1)
1.44(2)
1.41(2)
Bond Angles
P1-W-P2
P1-W-C8
P1-W-C9
81.78(7)
144.1(4)
144.0(4)
W-C8-C3
W-C9-C4
P2-W-C8
P2-W-C9
63.9(5)
64.7(6)
92.3(3)
91.0(3)
Figure 3. ORTEP diagram of the dication of 5. Hydrogen atoms are
removed for clarity.
parameters have been observed in other doubly metalated Cp*
complexes.15,16 Selected bond distances and angles from the
structure of 4 are listed in Table 3, and crystallographic details
are listed in Table 2.
diazenido(2-) character.17 The near linearity of the W-N-N
bond angle (176.0(7)°) suggests significant π electron delocal-
ization across the W2N2 core. The formally tungsten(III)
dinuclear complex is diamagnetic, presumably due to pairing
of the odd electrons in an orbital that is delocalized over the
W-N-N-W moiety. Schrock et al. have published a molecular
orbital analysis for the π bonding in the related dinuclear
complexes [W(Cp*)Me2X]2(µ-N2), which is consistent with the
observed diamagnetic nature of 5 as well as the observed W-N
and N-N bond lengths.18
The cation of 4 is a synthon for the [Cp*(dmpe)W]+ frag-
ment due to the reversibility of the Cp* methyl group activations.
Evidence for this reactivity was observed in the reaction of 4
with dinitrogen. Exposure of an orange fluorobenzene solution
of 4 to 1 atm of N2 at room temperature caused the solution to
darken within minutes. Allowing the mixture to stand at room
temperature overnight resulted in the isolation of green, X-ray
quality crystals of the compound [Cp*(dmpe)W(µ-N2)W
(dmpe)Cp*][B(C6F5)4]2 (5, eq 4). The dicationic dinitrogen
complex exhibits a symmetric structure by NMR spectroscopy
in acetonitrile-d3. For example, two doublet resonances (at δ
1.64 and 1.40) are observed for the dmpe methyl groups in
the 1H NMR spectrum of 5, and a single resonance with tung-
sten satellites is observed in the 31P{1H} NMR spectrum at
δ 7.8.
Silyl and Silylene Complexes from Reactions of Hydro-
silanes with (η6-C5Me4CH2)(dmpe)W(H)Cl. The equilib-
rium shown in Scheme 1 suggested that 1 might be reactive
toward hydrosilanes via oxidative addition of an Si-H bond
to the intermediate 16-electron tungsten(II) complex. In fact,
this process may be employed as a route to new tungsten
silyl complexes. The reaction of diphenylsilane with 1 at 90 °C
over 35 min resulted in formation of the new tungsten(IV) silyl-
(hydrido)chloride complex Cp*(dmpe)(H)(Cl)W(SiHPh2) (6a,
eq 5). The corresponding reaction with phenylmethylsilane
proceeds similarly to give the orange phenylmethylsilyl com-
plex Cp*(dmpe)(H)(Cl)W(SiHMePh) (6b). The latter complex
exhibits an unsymmetrical dmpe ligand by 31P{1H} NMR
spectroscopy, displaying two resonances for the phosphorus
nuclei at δ 11.8 and 8.0 (JPP ) 16 Hz), and the 29Si{1H}
NMR spectrum exhibits a resonance for the silicon center
as a doublet of doublets at δ 11.8 (JSiP ) 11 Hz, JSiP′ ) 5 Hz).
1
The H NMR spectrum of 6b displays the appropriate ligand
resonances, including a doublet of doublet resonance for
its tungsten hydride ligand at δ 3.81 (JHP ) 71 Hz, JHP′ ) 59
Hz). The spectroscopic properties of 6a are very similar to
those of 6b, including a downfield-shifted 1H NMR resonance
for its hydride ligand at δ 4.62 (JHP ) 59 Hz, JHP′ ) 46 Hz).
These unusual 1H NMR chemical shifts appear related to
the fact that the hydride ligands are located in positions
trans to the centroids of the Cp* ligands. Schrock and co-
workers have reported anomalously downfield-shifted methyl
resonances in the 1H NMR spectra of [Cp*WMe4]+ and
Cp*WMe5, and these signals were attributed to the methyl
The identity of 5 was confirmed by an X-ray crystallographic
analysis, and an ORTEP diagram of the dication is shown in
Figure 3. The structure of the dication has crystallographic
inversion symmetry, with an inversion center located at the
centroid of the N-N bond. The N-N distance of 1.22(1) Å is
more than 0.1 Å longer than that in free dinitrogen, and the
symmetry-related W-N bond distances are 1.888(5) Å. In
comparison to other dinuclear transition-metal dinitrogen com-
plexes, these values suggest that the bridging ligand has
(17) See, for example: (a) Hidai, M.; Mizobe, Y. Chem. ReV. 1995, 95, 1115.
(b) Fryzuk, M. D.; Johnson, S. A. Coord. Chem. ReV. 2000, 200-202,
379. (c) Shih, K.-Y.; Schrock, R. R.; Kempe, R. J. Am. Chem. Soc. 1994,
116, 8804.
(18) O’Regan, M. B.; Liu, A. H.; Finch, W. C.; Schrock, R. R.; Davis, W. M.
J. Am. Chem. Soc. 1990, 112, 4331.
(15) Cloke, F. G. N.; Green, J. C.; Green, M. L. H.; Morley, C. P. J. Chem.
Soc., Chem. Commun. 1985, 14, 945.
(16) (a) Carter, S. T.; Clegg, W.; Gibson, V. C.; Kee, T. P.; Sanner, R. D.
Organometallics 1989, 8, 253. (b) Gibson, V. C.; Kee, T. P.; Carter, S. T.;
Sanner, R. D.; Clegg, W. J. Organomet. Chem. 1991, 418, 197.
9
4378 J. AM. CHEM. SOC. VOL. 126, NO. 13, 2004

Synthons for Complexes of Tungsten
A R T I C L E S
Figure 5. ORTEP diagram of the silyl complex 7. Hydrogen atoms (except
hydrides) are omitted for clarity.
Figure 4. ORTEP diagram of the silyl complex 6b. Hydrogen atoms are
omitted for clarity.
Scheme 2
groups that are trans to the Cp* ligand centroids in these
compounds.19
The connectivity of compound 6b was confirmed by an X-ray
diffraction study, and an ORTEP diagram of the molecular
structure is shown in Figure 4. Details of the data collection
are listed in Table 2. This structure features a tungsten-silicon
bond distance of 2.549(3) Å, which is in the range of W-Si
bond distances observed in reported tungsten silyl complexes.
The hydride ligand in 6b was not located in the electron density
map, although it is almost certainly in a position trans to the
Cp* centroid, as the remaining ligands form a four-legged piano
stool type structure.
Compounds 6a and 6b were synthesized as precursors to
tungsten silylene complexes, and their reactivities were explored
in this regard. Reactions of compound 6a or 6b with an
alkylating agent such as benzyl Grignard were examined as
routes to silylene hydride complexes via reductive elimination
of alkane from an intermediate alkyl(silyl)hydride complex
according to Scheme 2. Alkylation of 6a with BnMgCl(OEt2)
(Bn ) -CH2Ph) in benzene proceeded quantitatively to produce
a new yellow species that was isolated in good yield by
crystallization from pentane. However, no toluene was observed
in the reaction mixture, and the isolated product features a benzyl
group (by 1H NMR spectroscopy), observed as a singlet
resonance for the PhCH2 group at δ 2.93. Characterization of
the product from this reaction revealed its identity as the tungsten
silyl complex Cp*(dmpe)(H)2W(SiPh2Bn) (7), isolated as yellow
crystals in 67% yield.
coordinate tungsten(IV) silyl dihydride complex, and the hydride
ligands were located and their coordinates were refined. The
Cp*, dmpe, silyl, and a single hydride form the basis of a four-
legged piano stool type structure, and the second hydride ligand
caps the P2SiH face (in a position trans to the Cp* centroid).
The details of the data collection for the structure of 7 are listed
in Table 2. The W-Si bond distance in this structure is 2.576-
(3) Å and is in the expected range for W-Si single bonds. It is
noteworthy that the complex has apparent mirror-symmetry by
1H NMR spectroscopy and therefore is not stereochemically
rigid in solution. That is, the hydride ligands appear as one
1
resonance in the H NMR spectrum, and no single hydride is
fixed in a position trans to the Cp* centroid.
The mechanism for the formation of 7 probably involves an
inner-sphere redistribution of substituents at silicon. Reductive
elimination of a silicon-carbon bond in the silyl-benzyl
intermediate could form an intermediate Si-H complex
[Cp*(dmpe)(H)W(η2-H-SiPh2Bn)], which would decompose
to 7 via Si-H oxidative addition. If silane were completely
eliminated from the coordination sphere of the metal, one would
expect other (sterically accessible) silanes present to scramble
into the product that is formed. However, when this reaction
occurred in the presence of 10 equiv of PhSiH3, the diphenyl-
benzylsilyl product formed quantitatively. This suggests that
complete elimination of Ph2BnSiH from the coordination sphere
of the metal does not occur. As this alkylation reaction did not
produce a silylene complex, we pursued alternate methods for
converting 6a to such a species. Abstraction of the chloride
ligand in these tungsten silyls proved successful in this regard.
The structure of complex 7 was confirmed by X-ray diffrac-
tion analysis, and an ORTEP diagram of the molecule is shown
in Figure 5. The structure can be described as a pseudo eight-
(19) Liu, A. H.; Murray, R. C.; Dewan, J. C.; Santarsiero, B. D.; Schrock, R.
R. J. Am. Chem. Soc. 1987, 109, 4282.
9
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A R T I C L E S
Mork and Tilley
Scheme 3
Figure 6. ORTEP diagram of one of the cations in the structure of silylene
complex 8c. The counterion and hydrogen atoms are omitted for clarity.
Table 4. Selected Distances (Å) and Angles (deg) for the Cations
in 8c
Exchange of the chloride ligand in complex 6a for the
noncoordinating anion B(C6F5)4 was achieved by reaction of
-
Bond Distances
W1-P1
W1-P2
W1-Si1
2.475(2)
2.476(2)
2.358(2)
W2-P3
W2-P4
W2-Si2
2.487(2)
2.431(3)
2.354(3)
the silyl complex with 1 equiv of Li(OEt2)3B(C6F5)4. Upon
mixing fluorobenzene solutions of the two reagents, a reaction
immediately occurred, as evidenced by formation of the white
LiCl precipitate and a color change to slightly darker orange.
The 29Si{1H} NMR spectrum of the new product showed a
single broad resonance at δ 277, and this downfield chemical
shift suggests that this product is the 18-electron silylene
dihydride complex [Cp*(dmpe)(H)2WdSiPh2][B(C6F5)4] (8a,
Scheme 3). The 1H NMR spectrum of the new complex features
a multiplet resonance at δ -3.97 for the two symmetry
equivalent hydride ligands. As shown in Scheme 3, this reaction
also proceeds cleanly for phenylmethyl silyl complex 6b, to
produce the phenylmethylsilylene complex 8b (29Si{1H} NMR
in PhF: δ 297). These reactions likely proceed via unobserved
intermediate 16-electron silyl hydride cations. A 1,2-hydride
migration from silicon to the metal would then give the observed
silylene dihydride product (Scheme 3).
Bond Angles
P1-W1-P2
P1-W1-Si1
P2-W1-Si1
75.23(7)
97.77(7)
97.00(8)
P3-W2-P4
P3-W2-Si2
P4-W2-Si2
76.08(8)
97.37(9)
108.6(1)
at δ 13.4 (JPW ) 221 Hz). The characterization of 8c as a
silylene complex was confirmed by its downfield-shifted peak
at δ 314 in the 29Si{1H} NMR spectrum.
Although the spectroscopic evidence supported the description
of 8a and 8b as silylene complexes, a confirmation of their
structures by X-ray crystallography was desired. Unfortunately,
the complexes were isolated as microcrystalline solids that are
not suitable for single-crystal diffraction studies. Furthermore,
attempted syntheses of silyl derivatives analogous to 6, which
might serve as precursors to silylene complexes, were unsuc-
To establish the geometry for these tungsten silylenes,
complex 8c was studied by X-ray diffraction techniques. Slow
liquid-liquid diffusion of pentane into a fluorobenzene solution
of 8c produced orange, X-ray quality crystals of the dimethyl-
silylene complex. The solid-state structure has two cation/anion
pairs in its asymmetric unit, and an ORTEP diagram of one of
the cations is shown in Figure 6. In each cation, the silylene
ligand is planar with the sum of the angles around silicon center
being essentially 360° (359.4(6)° and 359.5(8)°). The two
independent cations possess very short tungsten-silicon bond
distances (2.358(2) and 2.354(3) Å). For comparison, a range
of 2.389-2.708 Å for W-Si bond lengths was determined by
a search of the Cambridge structural database. The structural
parameters observed here (Table 4) are in keeping with those
observed for reported transition-metal silylene complexes.3-6,8
Tungsten silylenes 8a and 8b were also synthesized by
reactions of 4 with Ph2SiH2 and PhMeSiH2, respectively, and
this method is the more convenient route for their preparation.
In each case, the reaction is complete in 1 h at 60 °C in
fluorobenzene. These reactions likely proceed via the unob-
served 16-electron cation [η6-(C5Me4CH2)(dmpe)W(H)]+, which
is likely in equilibrium with 4 (Scheme 4). The proposed
i
cessful with Me2SiH2 and Pr2SiH2. For example, Me2SiH2
reacted with 1 in benzene at 60 °C to give an inseparable mixture
i
of products, and Pr2SiH2 does not react with 1 at 60 °C.
Decomposition of the reagents was observed at temperatures
above 80 °C. An alternate route to silylene complexes
related to 8a-b was therefore desired. Such a method was
discovered, involving reactions of hydrosilanes with the reactive
complex 4.
Silylene Complexes by Direct, Double Si-H Bond Activa-
tion Reactions. At 60 °C in fluorobenzene, 4 reacts with
dimethylsilane over 1 h under argon to form the silylene
complex [Cp*(dmpe)(H)2WdSiMe2][B(C6F5)4] (8c), isolated in
65% yield after crystallization from fluorobenzene/pentane (eq
6). The 1H NMR spectrum of the dimethylsilylene complex in
PhF exhibits a single resonance for two equivalent, silicon-bound
methyl groups at δ 0.89, and there are two doublets for the
equivalent pairs of dmpe methyl groups at δ 1.42 and 1.12.
The dmpe ligand is also symmetric by 31P{1H} NMR spectros-
copy, featuring only one singlet resonance with 183W satellites
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Synthons for Complexes of Tungsten
A R T I C L E S
ligand.21 To investigate the possibility of WH‚‚‚Si interactions
Scheme 4
2
in these compounds, the JHSi coupling constants were deter-
1
mined from H-detected, 1D 29Si HMQC BIRD filtered NMR
experiments. Because these coupling constants (7, 17, 17, and
15 Hz for 8a, b, c, and d, respectively) are less than 20 Hz, it
would appear that there is little or no interaction between the
hydride and silylene ligands in these compounds.
Reactivity of the Tungsten Silylene Complexes. In light of
the electrophilicity of the silicon centers in late metal silylene
complexes,2-6 it was of interest to probe the Lewis-acidity of
the silicon centers in these new tungsten compounds. Reaction
of dimethylsilylene complex 8c with 1 equiv of pyridine in
fluorobenzene resulted in an immediate color change of the
solution to red. The new product was isolated by crystallization
from fluorobenzene/pentane, and its spectroscopic characteriza-
tion is consistent with its identity as the pyridine adduct [Cp*-
(dmpe)(H)2WSiMe2(py)][B(C6F5)4] (9). Complex 9 has a29Si-
{1H} NMR resonance at δ 85, signifying that the silicon center
is four coordinate.8,22 The pyridine ligand appears to be strongly
bound to a Lewis-acidic silicon center, and drying the crystals
of 9 under vacuum overnight did not result in removal of the
coordinated pyridine. From this result, it appears that silylene
complexes 8 behave similarly to late transition-metal silylenes
with respect to Lewis-acidic behavior at silicon.
Additional studies with these complexes were designed to
discover chemical reactivities that differ from those of the known
silylene complexes, and this was achieved in reactions of 8c
with chloroalkanes. Recently, we reported the reaction of an
osmium silylene complex with benzyl chloride, which proceeds
by chlorine atom transfer to silicon and a net oxidation of the
osmium center.4 Interest in the reactions of silylene complexes
with chloroalkanes is derived from the fact that surface-bound
copper silylenes are postulated as intermediates in the direct
synthesis of alkylhalosilanes.9 Studies on this heterogeneous
process suggest that, in the course of the reaction, surface-bound
silylenes insert into the C-Cl bonds of chloroalkanes to give
the observed products. We were interested in the reactions of
these new tungsten silylene complexes with chloroalkanes and
have observed a related reaction in which a tungsten-bound
silylene inserts into a C-Cl bond.
mechanism of Scheme 4 is supported by the observation that
diphenylsilane-d2 reacted with 4 to form [Cp*(dmpe)(D)2Wd
SiPh2][B(C6F5)4], having greater than 90% deuterium incorpora-
tion at the tungsten hydride positions (by H and H NMR
spectroscopy). Given the utility of this hydrosilane activation
reaction, we pursued the synthesis of silylene complexes from
primary (monosubstituted) silanes.
Nearly all known examples of metal silylene complexes
lacking donor stabilization feature silicon centers with alkyl or
aryl substituents at silicon. Recently, Tessier and co-workers
reported the generation in solution of a metal silylene complex
with a hydride substituent at silicon, [(Et3P)3(H)2IrdSi(H)(C6H3-
Mes2-2,6)][B(C6F5)4].20 It is of interest to synthesize more
examples of hydrosilylene complexes and to probe the chemistry
and spectroscopic properties of Si-H groups on sp2-hybridized
silicon centers.
1
2
Reactions of 4 with the monosubstituted silanes PhSiH3 and
MesSiH3 (Mes ) 2,4,6-trimethylphenyl) resulted in complex
mixtures of products from which no clean compounds could
be isolated. However, reaction of 4 with DippSiH3 (Dipp )
2,6-diisopropylphenyl) proceeded cleanly over 1 h at 60 °C in
fluorobenzene to give the silylene complex [Cp*(dmpe)(H)2Wd
Si(H)Dipp] (8d). It seems likely that the steric bulk of the
isopropyl groups of the Dipp ligand is necessary to stabilize
1
Heating a fluorobenzene solution of 8c and excess (ap-
proximately 5 equiv) MeCl to 70 °C for 30 min in a sealed
this type of complex. The H NMR spectrum of 8d features a
uniquely downfield-shifted Si-H resonance at δ 10.83 (JHSi
)
1
NMR tube resulted in a red solution. The H NMR spectrum
167 Hz, JHW ) 17 Hz), as well as a multiplet for its dihydride
ligands at δ -4.01. Analogously to complexes 8a-c, the 31P-
{1H} NMR spectrum of 8d features a single resonance with a
chemical shift of δ 12.3 (JPW ) 209 Hz). The 1H, 29Si HMQC
2D NMR spectrum of 8d revealed a resonance at δ 286 that is
coupled strongly to the Si-H proton (JHSi ) 167 Hz). Complex
8d was isolated as an analytically pure orange solid by removing
the volatiles under reduced pressure.
To investigate possible H-H and Si-H interligand bonding
interactions in complexes 8a-d, various spectroscopic methods
were employed. On the basis of 1H NMR T1 relaxation
experiments, the hydride ligands in these complexes appear to
be classical in nature. Using the null method, the T1(min) values
for the dhydride ligands in 8a, b, c, and d were determined to
be in the range of 600-800 ms. Such T1 values suggest classical
dihydride character, rather than the presence of a dihydrogen
of this mixture displayed a resonance for Me3SiCl (78% yield
by internal cyclooctane standard), the product of insertion of
dimethylsilylene into the C-Cl bond of MeCl. It seemed that
the reaction formed paramagnetic tungsten products, as only
trace diamagnetic impurities are observed spectroscopically.
Isolation of the major metal-containing product (10) was
achieved by crystallization, and the red crystals were analyzed
by X-ray diffraction. The solid-state structure of this new
complex identified it as the tungsten(V) dichlorohydride com-
plex [Cp*(dmpe)W(H)Cl2][B(C6F5)4] (10, eq 7). The structure
is of sufficient quality to conclusively determine connectivity;
however, disorder of the Cp* and dmpe ligands in the cation
prevented refinement of accurate metric parameters. The hydride
(21) Crabtree, R. H.; Bonneviot, L. J. Am. Chem. Soc. 1986, 108, 4032.
(22) For examples of donor-stabilized tungsten silylene complexes: (a) Ueno,
K.; Sakai, M.; Ogino, H. Organometallics 1998, 17, 2138. (b) Sakaba, H.;
Tsukamoto, M.; Hirata, T.; Kabuto, C.; Horino, H. J. Am. Chem. Soc. 2000,
122, 11511.
(20) Simons, R. S.; Gallucci, J. C.; Tessier, C. A.; Youngs, W. J. J. Organomet.
Chem. 2002, 654, 224.
9
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A R T I C L E S
Mork and Tilley
ligand was not located in the structure; however, its location
was inferred to be in the open coordination site at the tungsten
center of the cation. Further confirmation of the presence of a
hydride ligand in 10 was obtained by IR spectroscopy, which
revealed a W-H stretching absorbance at 1879 cm-1. In the
course of reaction, the tungsten is oxidized from tungsten(IV)
to tungsten(V), and more than 1 equiv of MeCl is involved in
this transformation. It was therefore of interest to explore the
reactions of 8c with a stoichiometric quantity of chloroalkane.
This is a significant advancement toward a more diverse
collection of silylene complexes and the beginning of the study
of the chemistry of these new species.
It seems that the reactivity of early metal silylenes is distinct
from that of their late metal analogues. The dimethylsilylene
complex 8c was shown to react with chloroalkanes in a fashion
that parallels the proposed mechanism for the direct synthesis.
This is an unprecedented example of silylene insertion into a
C-Cl bond by a discrete molecular silylene complex, and it
provides support for the proposed intermediacy of metal
silylenes in that process. In contrast, the osmium silylene
complex [Cp*(Me3P)2OsdSiMe2]+ acquires a chlorine radical
from PhCH2Cl to form the osmium(III) cation [Cp*(Me3P)2-
(SiMe2Cl)]+,4 and there is no Si-C bond formation observed.
These reactions highlight the potential for early metal silylene
complexes to exhibit new and potentially useful reactivities.
The electrophilicity observed for the silicon centers in these
compounds inspires interest in synthesizing analogues with more
strongly π-donating metal centers. Therefore, the possibility of
silylene chemistry with more electropositive early transition
metals such as tantalum and zirconium is a subject of continuing
exploration.
Experimental Section
Using a glass bulb of known volume, 1 equiv of MeCl was
introduced to a sample of 8c, and the NMR tube was sealed
and heated at 70 °C for 30 min (eq 8). A 1H NMR spectrum of
the resulting orange/brown solution revealed the presence of
Me3SiCl in 82% yield and a mixture of diamagnetic metal-
containing products. Under the same conditions, EtCl reacted
with 8c to produce an orange/brown solution and EtMe2SiCl
(76% yield) by 1H and 29Si{1H} NMR spectroscopy. The
tungsten complexes formed in these reactions have not been
identified, and these may include paramagnetic species.
General. All experiments were performed under an atmosphere of
dry argon using standard Schlenk techniques or in a drybox under
nitrogen. Fluorobenzene was distilled from P2O5, and pentane was
distilled from sodium/benzophenone. To remove olefin impurities,
pentane was pretreated with concentrated H2SO4, 0.5 N KMnO4 in 3
M H2SO4, NaHCO3, and then anhydrous MgSO4. Benzene-d6 was
distilled from Na/K alloy. m-Fluorotoluene was vacuum transferred from
CaH2 and degassed prior to use. The reagents Li(Et2O)2.5B(C6F5)4,23
Cp*WCl4,12 and 1,2-bis(dimethylphosphino)ethane24 were synthesized
according to published procedures. Other chemicals were obtained from
commercial suppliers and used as received. Elemental analyses were
performed by the Microanalytical Laboratory in the College of
Chemistry at the University of California, Berkeley. FT-infrared spectra
were recorded as KBr pellets or Nujol mulls on a Mattson FTIR 3000
instrument.
NMR Measurements. Routine 1H, 13C{1H}, 31P{1H}, and 29Si{1H}
NMR spectra were recorded at 298 K on either a Bruker DRX-500
instrument equipped with a 5 mm broad band probe and operating at
500.1 MHz (1H), 125.8 MHz (13C), 202.5 MHz (31P), and 99.4 MHz
(29Si) or a Bruker AMX-400 instrument operating at 400.1 MHz (1H),
100.6 MHz (13C), or 61.4 MHz (2H). Chemical shifts are reported in
ppm downfield from internal SiMe4 (1H, 13C, 29Si), and external 85%
H3PO4 (31P); coupling constants are given in hertz. Samples of 2, 3a-
c, and 4 were prepared as 0.4 mL solutions in a 10:1 mixture of
fluorobenzene/benzene-d6 to obtain a deuterium lock signal. Bruker
XWINNMR software (ver. 2.1) was used for all data processing. T1-
(min) measurements were made for dihydride protons in 3a-c using
m-fluorotoluene as the solvent.
X-ray Crystallography. The single-crystal X-ray analysis of
compound 1 was carried out by Dr. Fred Hollander and Dr. Dana
Caulder at the UC Berkeley CHEXRAY crystallographic facility.
Structural analyses of compounds 4, 5, 6b, 7, 8c, and 10 were carried
out by the authors using the same facility. Measurements were made
on a Bruker SMART CCD area detector with graphite monochromated
Mo KR radiation (λ ) 0.71069 Å). Data were integrated by the program
SAINT and were analyzed for agreement using XPREP. Empirical
absorption corrections were made using SADABS. Structures were
Concluding Remarks
The metalated Cp* complexes 1 and 4 are sources of the
reactive fragments Cp*(dmpe)WCl and [Cp*(dmpe)W]+, re-
spectively. Reactions of these species with small molecules
suggested that they might be useful in Si-H bond activations
toward the syntheses of silyl and silylene complexes of tungsten.
Both 1 and 4 react with hydrosilanes, and this reactivity has
provided a route to a new class of formally d0 silylene complexes
of the type [Cp*(dmpe)(H)2WdSiR2][B(C6F5)4] (8).
Spectroscopic studies indicate that these complexes are
accurately described as silylene dihydrides, and a reaction with
pyridine has shown them to be electrophilic at silicon. This
electrophilicity suggests that the silylene ligands in these
complexes may be described as neutral, two-electron donor
ligands that receive stabilization by π back-bonding from the
tungsten center. By this description of the bonding, the tungsten
centers are d2 and in the +4 oxidation state. Silylene complexes
8 represent the first instances of donor-free silylene ligands
coordinated to transition metals that have only two d-electrons.
(23) Massey, A. G.; Park, A. J. J. Organomet. Chem. 1964, 2, 245.
(24) Burt, R. J.; Chatt, J.; Hussain, W.; Leigh, G. J. J. Organomet. Chem. 1979,
182, 203.
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Synthons for Complexes of Tungsten
A R T I C L E S
solved by direct methods and expanded using Fourier techniques.
Calculations for the structures of complex 5 was performed using the
SHELX-TL software package. For the remainder of the structures, all
calculations were performed using the teXsan crystallographic software
package. Details of data collections and refinements are in Table 2
and in the Supporting Information CIF files.
for 18 h at 90 °C resulted in a red solution. Removal of the volatiles
under reduced pressure and recrystallization from 4 mL of ether at -30
°C over 12 h resulted in isolation of 0.120 g of orange/red crystals of
1
2 (81% yield). H NMR (benzene-d6): δ 2.17 (s, 15H, C5Me5), 1.49
(m, 2H, 2PCH2), 1.36 (m, 12H, 4PMe), 1.40 (m, 2H, 2PCH2), -6.17
(m, 2H, WH2, JHP ) 65 Hz, JHW ) 60 Hz). 13C NMR (benzene-d6): δ
92.8 (s, C5Me5), 31.8 (t, 2PCH2, JCP ) 21 Hz), 24.4 (virtual t, 2PMe,
JCP ) 21 Hz), 13.9 (s, C5Me5), 11.3 (virtual t, 2PMe, JCP ) 13 Hz).
31P{1H} NMR (benzene-d6): δ 23.1 (s, JPW ) 156 Hz). IR (KBr, cm-1):
1841 m (νWH), 1827 m (νWH). Anal. Calcd for C16H33ClP2W: C, 37.93;
H, 6.56. Found: C, 38.00; H, 6.69.
(η6-C5Me4CH2)(dmpe)W(H)Cl (1). A round-bottomed Schlenk flask
was charged with 70.1 g of Na/Hg amalgam (0.8% w/w, 24.4 mmol),
1.36 mL of dmpe (8.14 mmol), 50 mL of benzene, and a magnetic
stirbar. In a separate 100 mL Schlenk tube was agitated Cp*WCl4 (3.75
g, 8.14 mmol) to a slurry in 75 mL of benzene. With continued agitation,
the orange slurry was quickly added via cannula to the amalgam and
dmpe with vigorous stirring. Immediately upon addition, the reaction
became dark green, and a mild exotherm occurred. Within 5 min of
rapid stirring, the slurry had changed color to brown/red, and it was
allowed to stir for 1 h at ambient temperature. The mixture was heated
to 60 °C, was stirred for 16 h, and then was allowed to cool to room
temperature. The supernatant was filtered away from the salts and
mercury to give a dark red solution. Removal of benzene in vacuo
yielded a dark red waxy solid. Pentane (25 mL) was added and removed
under reduced pressure to aid in removal of benzene from the product.
Further drying under vacuum yielded 3.40 g (83%) of 1 as a red/brown
solid. The product is of sufficient purity to be used in subsequent
reactions. Orange/red X-ray quality crystals of 1 were obtained by
recrystallization from pentane. 1H NMR (benzene-d6): δ 3.82 (d, 1H,
η6-C5Me4CH2, JHP ) 9 Hz), 2.69 (s, 1H, η6-C5Me4CH2), 2.12 (s, 3H,
η6-C5Me4CH2), 2.07 (s, 3H, η6-C5Me4CH2), 2.06 (s, 3H, η6-C5Me4CH2),
1.82 (s, 3H, η6-C5Me4CH2), 1.70 (m, 1H, PCH2), 1.54 (m, 1H, PCH2),
1.53 (d, 3H, PMe, JHP ) 8 Hz), 1.35 (m, 1H, PCH2), 1.29 (d, 3H,
PMe, JHP ) 9 Hz), 1.23 (d, 3H, PMe, JHP ) 9 Hz), 1.03 (m, 1H, PCH2),
0.98 (d, 3H, PMe, JHP ) 7 Hz), -8.25 (dd, 1H, W-H, JHP ) 42 Hz,
JHP′ ) 73 Hz, JHW ) 42 Hz). 13C{1H} NMR (benzene-d6): δ 110.5 (s,
η6-C5Me4CH2), 109.4 (s, η6-C5Me4CH2), 102.4 (s, η6-C5Me4CH2), 87.2
(s, η6-C5Me4CH2), 86.3 (s, η6-C5Me4CH2), 60.2 (t, η6-C5Me4CH2, JCP
) 8 Hz), 34.6 (dd, PCH2, JCP ) 11 Hz, JCP′ ) 28 Hz), 32.4 (dd, PCH2,
JCP ) 28 Hz, JCP′ ) 12 Hz), 24.3 (dd, PMe, JCP ) 3 Hz, JCP′ ) 40 Hz),
18.5 (dd, PMe, JCP ) 3 Hz, JCP′ ) 26 Hz), 16.7 (s, η6-C5Me4CH2),
15.2 (d, PMe, JCP ) 20 Hz), 13.0 (s, η6-C5Me4CH2), 12.9 (s, η6-C5Me4-
CH2), 12.6 (s, η6-C5Me4CH2), 11.3 (d, PMe, JCP ) 25 Hz). 31P{1H}
NMR (benzene-d6): δ 18.6 (s, JPW ) 253 Hz), 10.8 (s, JPW ) 233
Hz). IR (KBr, cm-1): 1896 m (νWH). Anal. Calcd for C16H31P2ClW:
C, 38.08; H, 6.19. Found: C, 38.36; H, 6.49.
Cp*(dmpe)W(D)2Cl (3-d2). A sealable NMR tube was charged with
0.013 g (26 µmol) of 1 and 0.4 mL of benzene-d6. The solution was
degassed with three freeze-pump-thaw cycles, and then the tube was
backfilled with 1 atm of deuterium gas. Heating the tube at 110 °C in
an oil bath for 10 d resulted in quantitative conversion of 1 to the
dideuteride complex 3-d2. The complex’s NMR spectra are identical
to those of dihydride 3, except that there is no hydride resonance in
the 1H NMR spectrum, and the 31P{1H}NMR spectrum shows coupling
to the two deuterium nuclei. 2H NMR (benzene-d6): δ -6.10 (t, WD2,
JDP ) 8 Hz). 31P{1H} NMR (benzene-d6): δ 23.0 (quintet, 183W
satellites, JPW ) 156 Hz, JPD ) 8 Hz).
[(η7-C5Me3(CH2)2)(dmpe)W(H)2][B(C6F5)4] (4). To a sealable
reaction flask was added 0.100 g (0.198 mmol) of 1 and 0.173 g (0.198
mmol) of Li(Et2O)2.5B(C6F5)4. The sealed flask was fitted to a vacuum
transfer apparatus on a Schlenk line, and 3 mL of fluorobenzene was
vacuum transferred onto the solids at -78 °C. The flask was backfilled
with argon and warmed to room temperature, and the orange solution
was allowed to stir for 1 h. The mixture was filtered into another
Schlenk flask under argon, and 4 mL of pentane was layered upon the
fluorobenzene solution. After the mixture was left standing for 1 d,
orange crystals had precipitated. The supernatant was decanted via
cannula, and the crystals were dried under vacuum to give 0.159 g of
1
2 in 70% yield. H NMR (fluorobenzene): δ 2.64 (s, 2H, η7-C5Me3-
(CH2)2), 1.85 (s, 3H, η7-C5Me3(CH2)2), 1.77 (m, 2H, η7-C5Me3(CH2)2),
1.71 (m, 2H, PCH2), 1.68 (s, 6H, η7-C5Me3(CH2)2), 1.60 (m, 2H, PCH2),
1.28 (d, 6H, PMe2, JHP ) 10 Hz), 1.07 (d, 6H, PMe2, JHP ) 9 Hz),
-2.11 (dd, 2H, W(H)2, JHP ) 38 Hz, JHP′ ) 58 Hz, JHW ) 49 Hz).
31P{1H} NMR (fluorobenzene): δ 14.7 (s, JPW ) 142 Hz), 11.3 (s,
JPW ) 207 Hz). 13C{1H} NMR (fluorobenzene): δ 150.4, 148.5, 138.2,
136.4 (m, B(C6F5)4), 109.7 (s, η7-C5Me3(CH2)2), 108.9 (d, η7-C5Me3-
(CH2)2), JCP ) 21 Hz), 106.4 (s, η7-C5Me3(CH2)2), 51.0 (dd, η7-C5-
Me3(CH2)2), JCP ) 2 Hz, JCP′ ) 6 Hz), 32.2 (dd, PCH2, JCP ) 9 Hz,
JCP′ ) 38 Hz), 30.4 (dd, PCH2, JCP ) 7 Hz, JCP′ ) 34 Hz), 20.0 (d,
PMe2, JCP ) 35 Hz), 17.3 (d, PMe2, JCP ) 33 Hz), 11.3 (s, η7-C5Me3-
(CH2)2), 10.2 (s, η7-C5Me3(CH2)2). IR (Nujol, cm-1): 1861 w (νWH),
1843 w (νWH). Anal. Calcd for C40H31BF20P2W: C, 41.84; H, 2.72.
Found: C, 41.90; H, 2.90.
Cp*(dmpe)W(CO)Cl (2). A solution of 0.100 g (0.198 mmol) of
compound 1 in 3 mL of toluene was added to a sealable flask. This
solution was placed under vacuum for 15 s, and the flask was then
backfilled with 1 atm of carbon monoxide. Heating the sealed reaction
vessel for 24 h at 70 °C resulted in a red solution. Removal of the
volatiles under reduced pressure and recrystallization from 3 mL of
ether at -30 °C over 12 h resulted in isolation of 0.072 g of orange/
red microcrystalline 3 (68% yield). 1H NMR (benzene-d6): δ 1.78 (s,
{[Cp*(dmpe)W]2(µ-N2)}{B(C6F5)4}2 (5). To 0.200 g (0.396 mmol)
of 1 and 0.360 g (0.396 mmol) of Li(OEt2)3B(C6F5)4 was added 10
mL of fluorobenzene under nitrogen. The mixture changed color from
orange to dark orange/brown within minutes and was allowed to stand.
After 24 h, green crystals had formed on the sides of the flask, and
there was a fine white precipitate of LiCl present. The supernatant was
decanted via cannula, and the green crystals were washed three times
with 5 mL of pentane. With each wash, the mixture was slurried and
the fine LiCl was removed as a suspension with the wash pentane.
Drying the crystals under vacuum for 8 h gave 0.238 g of 5 (59%
yield). 1H NMR (acetonitrile-d3): δ 2.08 (s, 15H, C5Me5), 1.8 (m, 4H,
15H, C5Me5), 1.58 (d, 3H, PMe, JHP ) 9 Hz), 1.46 (d, 3H, PMe, JHP
)
9 Hz), 1.3 (m, 2H, 2PCH2), 1.2 (m, 1H, PCH2), 1.12 (d, 3H, PMe, JHP
) 8 Hz), 0.76 (d, 3H, PMe, JHP ) 7 Hz), 0.73 (m, 1H, PCH2). 13C
NMR (benzene-d6): δ 244.4 (dd, WCO, JCP ) 18 Hz, JCP′ ) 4 Hz),
100.7 (d, C5Me5, JCP ) 2 Hz), 35.8 (dd, PMe, JCP ) 33 Hz, JCP′ ) 16
Hz), 28.7 (dd, PMe, JCP ) 29 Hz, JCP′ ) 13 Hz), 21.3 (dd, PCH2, JCP
) 40 Hz, JCP′ ) 2 Hz), 20.5 (d, PCH2, JCP ) 32 Hz), 19.2 (dd, PMe,
JCP ) 16 Hz, JCP′ ) 3 Hz), 14.5 (dd, PMe, JCP ) 25 Hz, JCP′ ) 3 Hz),
12.0 (d, C5Me5, JCP ) 1 Hz). 31P{1H} NMR (benzene-d6): δ 23.8 (s,
JPW ) 266 Hz), 19.2 (s, JPW ) 297 Hz). IR (Nujol, cm-1): 1789 m
(νCO). Anal. Calcd for C17H31ClOP2W: C, 38.33; H, 5.87. Found: C,
38.58; H, 5.92.
2PCH2), 1.64 (d, 6H, 2PMe, JHP ) 10 Hz), 1.40 (d, 6H, 2PMe, JHP
)
10 Hz). 31P{1H} NMR (acetonitrile-d3): δ 7.8 (s, tungsten satellites,
JPW ) 374 Hz). 13C{1H} NMR (acetonitrile-d3): δ 149.9 (br, B(C6F5)4),
147.9 (br, B(C6F5)4), 138.2 (br, B(C6F5)4), 136.2 (br, B(C6F5)4), 107.3
(s, C5Me5), 37.1 (m, 2PCH2), 21.5 (m, 2PMe), 14.4 (m, 2PMe), 12.7
(s, C5Me5). Anal. Calcd for C40H31NBF20P2W: C, 41.34; H, 2.69; N,
1.21. Found: C, 41.49; H, 2.73; N, 1.09.
Cp*(dmpe)W(H)2Cl (3). A solution of 0.148 g (0.293 mmol) of
compound 1 in 3 mL of toluene was added to a 10 mL sealable flask.
The mixture was placed under vacuum for 15 s, and the flask was then
backfilled with 1 atm of hydrogen. Heating the sealed reaction vessel
9
J. AM. CHEM. SOC. VOL. 126, NO. 13, 2004 4383

A R T I C L E S
Mork and Tilley
Cp*(dmpe)(H)W(SiPh2H)Cl (6a). Diphenylsilane (0.401 g, 2.18
mmol) was dissolved in 10 mL of toluene, and the resulting solution
was added via cannula to a solution of 1 (1.00 g, 1.98 mmol) in 20 mL
of toluene. The orange mixture was heated for 35 min at 90 °C, resulting
in precipitation of some of the product as an orange microcrystalline
solid. Toluene was then removed under reduced pressure, and the orange
product was washed with 3 × 15 mL pentane. Compound 6a was
isolated as 0.837 g of a light orange solid (61% yield). 1H NMR
(methylene chloride-d2): δ 7.98 (m, 2H, o-Ph), 7.82 (m, 2H, o-Ph),
7.12 (m, 2H, p-Ph), 7.05 (m, 4H, m-Ph), 5.44 (s, 1H, SiH), 4.62 (dd,
1H, WH, JHP ) 59 Hz, JHP′ ) 46 Hz), 1.82 (s, 15H, C5Me5), 1.70 (d,
3H, PMe, JHP ) 9 Hz), 1.63 (m, 1H, PCH2), 1.55 (m, 1H, PCH2), 1.45
(d, 3H, PMe, JHP ) 8 Hz), 1.40 (d, 3H, PMe, JHP ) 9 Hz), 1.30 (m,
2H, 2PCH2), 1.16 (d, 3H, PMe, JHP ) 7 Hz). 13C{1H} NMR (methylene
chloride-d2): δ 151.8, 149.8 (i-Ph), 137.4, 135.6 (o-Ph), 126.8, 126.1
(m-Ph), 126.0, 125.9 (p-Ph), 95.5 (C5Me5), 38.5 (m, PCH2), 30.4 (m,
PCH2), 18.5 (m, PMe), 18.4 (m, PMe), 18.3 (m, PMe), 13.7 (d, PMe,
JCP ) 17 Hz), 11.4 (s, C5Me5). 31P{1H} NMR (methylene chloride-d2):
δ 8.6 (d, 183W satellites, JPP ) 15 Hz, JPW ) 205 Hz), 7.9 (d, 183W
satellites, JPP ) 15 Hz, JPW ) 240 Hz). 1H, 29Si HMQC (benzene-d6):
δ 9.3 (Si-H, JHSi ) 157 Hz). IR (Nujol, cm-1): 2026 m (νSiH), 1910
w (νWH). Anal. Calcd for C28H43ClP2SiW: C, 48.41; H, 6.29. Found:
C, 48.45; H, 6.44.
[Cp*(dmpe)(H)2WdSiPh2][B(C6F5)4] (8a). A sealable reaction flask
was charged with 0.100 g (0.198 mmol) of 1, 0.173 g (0.198 mmol) of
Li(Et2O)2.5B(C6F5)4, and 0.040 g (0.217 mmol) of Ph2SiH2 and sealed
in a drybox. On a Schlenk line, 3 mL of fluorobenzene was added to
the flask via cannula, and the orange solution was heated at 70 °C for
1 h. The solution was then filtered into a 10 mL Schlenk tube to remove
LiCl, and 5 mL of pentane was layered onto the product solution via
cannula. Overnight, the product precipitated as the liquids diffused
together. The supernatant was filtered away, and the product was dried
under reduced pressure for 6 h, yielding 0.192 g of 8a as an orange/
1
yellow solid (73% yield). H NMR (fluorobenzene): δ 7.63 (d, 4H,
o-Ph, JHH ) 7 Hz), 7.34 (t, 4H, m-Ph, JHH ) 7 Hz), 7.28 (m, 2H,
p-Ph), 1.86 (s, 15H, C5Me5), 1.36 (m, 2H, 2PCH2), 1.34 (d, 6H, 2PMe,
JHP ) 8 Hz), 1.19 (d, 6H, 2PMe, JHP ) 7 Hz), 1.15 (m, 2H, 2PCH2,
JHP ) 8 Hz), -3.97 (m, 2H, W(H)2, JHW ) 47 Hz). 13C{1H} NMR
(fluorobenzene): δ 150.9 (s, SiPh), 150.4, 148.6, 138.3, 136.3 (m,
B(C6F5)4), 134.6, 130.9, 128.7 (s, SiPh), 100.3 (s, C5Me5), 32.3 (m,
2PCH2), 27.5 (m, 2PMe), 17.1 (m, 2PMe), 12.5 (s, C5Me5). 31P{1H}
NMR (fluorobenzene): δ 13.5 (s, JPW ) 204 Hz). 29Si{1H} NMR
(fluorobenzene): δ 277 (br). IR (KBr, cm-1) 1900 w br (νWH). Anal.
Calcd for C52H43BF20P2SiW: C, 46.94; H, 3.26. Found: C, 47.33; H,
3.44.
[Cp*(dmpe)(D)2WdSiPh2][B(C6F5)4] (8a-d2). A sealable NMR tube
was charged with 0.020 g (40 µmol) of 1, 0.0074 g (0.040 µmol) of
Ph2SiD2, and 0.036 g (40 µmol) of Li(Et2O)3B(C6F5)4 in 0.4 mL of
fluorobenzene. The tube was then heated at 70 °C for 1 h, resulting in
a yellow/orange solution of 8a-d2 and a small amount of precipitated
LiCl. The complex’s NMR spectra are identical to those of the silylene
dihydride 8a, except that there is only a trace hydride resonance in the
1H NMR spectrum, and the 31P{1H}NMR spectrum shows coupling to
the two deuterium nuclei. 2H NMR (fluorobenzene): δ 1.87 (t,
integrates to 0.18D, JDH ) 1.8 Hz), -3.65 (m, 2D, WD2). 31P{1H}
NMR (fluorobenzene): δ 13.7 (quintet, 183W satellites, JPW ) 200 Hz,
JPD ) 5 Hz).
Cp*(dmpe)(H)W(SiHPhMe)Cl (6b). Phenylmethylsilane (0.280 g,
2.29 mmol) was dissolved in 10 mL of toluene, and the resulting
solution was added via cannula to a solution of 1 (1.00 g, 1.98 mmol)
in 20 mL of toluene. The orange solution was heated at 100 °C for 30
min and then allowed to cool to room temperature. The volatile material
was removed under reduced pressure, and the orange solid was washed
twice with 10 mL of cold pentane. Drying the product under vacuum
gave 6b as 0.630 g of a light orange solid (51% yield). 1H NMR
(benzene-d6): δ 8.28 (m, 2H, o-Ph), 7.35 (m, 2H, m-Ph), 7.20 (m, 1H,
p-Ph), 5.28 (m, 1H, Si-H), 3.81 (dd, 1H, W-H, JHP ) 71 Hz, JHP′
)
59 Hz), 1.79 (s, 15H, C5Me5), 1.64 (d, 3H, PMe, JHP ) 11 Hz), 1.26
(d, 3H, PMe, JHP ) 12 Hz), 1.2 (m, 1H, PCH2), 1.1 (m, 1H, PCH2),
0.95 (d, 3H, PMe, JHP ) 9 Hz), 0.9 (m, 1H, PCH2), 0.89 (d, 3H, SiMe,
JHH ) 5 Hz), 0.5 (m, 1H, PCH2), 0.44 (d, 3H, PMe, JHP ) 9 Hz).
13C{1H} NMR (benzene-d6): δ 154.3, 135.8, 127.6, 126.8 (s, Ph), 95.5
(s, C5Me5), 38.7 (dd, PMe, JCP ) 40 Hz, JCP′ ) 8 Hz), 30.7 (dd, PMe,
JCP ) 34 Hz, JCP′ ) 8 Hz), 18.9 (m, PCH2), 18.7 (m, PCH2), 17.7 (m,
PMe), 14.3 (m, PMe), 11.6 (s, C5Me5), 2.5 (s, SiMe). 31P{1H} NMR
(benzene-d6): δ 11.8 (d, JPP ) 16 Hz, JPW ) 207 Hz), 8.0 (d, JPP ) 16
[Cp*(dmpe)(H)2WdSiPhMe][B(C6F5)4] (8b). A sealable reaction
flask was charged with 0.100 g (0.198 mmol) of 1, 0.173 g (0.198
mmol) of Li(Et2O)2.5B(C6F5)4, and 0.027 g (0.217 mmol) of PhMeSiH2
and sealed in a drybox. On a Schlenk line, 3 mL of fluorobenzene was
added to the flask via cannula, and the orange solution was heated at
70 °C for 1 h. The solution was then filtered into a 10 mL Schlenk
tube to remove LiCl, and 5 mL of pentane was layered onto the product
solution via cannula. Overnight, the product precipitated as the liquids
diffused together. The supernatant was filtered away, and the product
was dried under reduced pressure for 6 h, yielding 0.178 g of 8b as an
Hz, JPW ) 254 Hz). 29Si{1H} NMR (benzene-d6): δ 11.8 (dd, JSiP
)
11 Hz, JSiP′ ) 5 Hz). IR (KBr, cm-1): 1900 w (νWH). Anal. Calcd for
1
C23H41ClP2SiW: C, 44.06; H, 6.59. Found: C, 43.79; H, 6.49.
orange/yellow solid (70% yield). H NMR (fluorobenzene): δ 7.76
(d, 2H, o-Ph, JHH ) 7 Hz), 7.40 (t, 2H, m-Ph, JHH ) 7 Hz), 7.33 (m,
1H, p-Ph), 1.87 (s, 15H, C5Me5), 1.47 (d, 6H, 2PMe, JHP ) 9 Hz),
1.35 (m, 2H, 2PCH2), 1.30 (s, 3H, SiMe), 1.18 (d, 6H, 2PMe, JHP ) 8
Hz), 1.08 (m, 2H, 2PCH2), -4.02 (m, 2H, W(H)2, JHW ) 48 Hz). 13C-
{1H} NMR (fluorobenzene): δ 150.7 (s, SiPh), 150.4, 148.5, 138.3,
136.3 (m, B(C6F5)4), 133.9, 131.6, 128.9 (s, SiPh), 100.6 (s, C5Me5),
32.1 (m, 2PCH2), 28.4 (m, 2PMe), 25.3 (s, SiMe), 16.8 (m, 2PMe),
12.5 (s, C5Me5). 31P{1H} NMR (fluorobenzene): δ 13.3 (s, JPW ) 201
Hz). 29Si{1H} NMR (fluorobenzene): δ 297 (m). IR (KBr, cm-1): 1900
w br (νWH). Anal. Calcd for C47H41BF20P2SiW: C, 44.43; H, 3.25.
Found: C, 45.59; H, 3.00. Repeated attempts to obtain satisfactory
elemental analysis on compound 8b were unsuccessful, possibly due
to residual fluorobenzene in the sample that could not be removed under
vacuum (Anal. Calcd for 8b‚(PhF)0.5: C, 45.54; H, 3.32).
[Cp*(dmpe)(H)2WdSiMe2][B(C6F5)4] (8c). A sealable reaction
flask was charged with 0.100 g (0.198 mmol) of 1 and 0.173 g (0.198
mmol) of Li(Et2O)2.5B(C6F5)4. On a Schlenk line, 3 mL of fluorobenzene
was vacuum transferred onto the solids at -20 °C. The headspace of
the flask was then backfilled with an excess of dimethylsilane
(approximately 20 mL at 1 atm, 0.9 mmol) and sealed. The mixture
was allowed to stir for 1 h at 70 °C, and the orange solution was filtered
Cp*(dmpe)(H)2W(SiPh2Bn) (7). To a slurry of 0.150 g (0.217
mmol) of 6a in 10 mL of C6H6 was added 2.2 mL (0.22 mmol) of a
1.0 M solution of BnMgCl in Et2O. Immediately upon addition, the
solution changed color from orange to yellow, and a white precipitate
of MgCl2 was formed. The volatile material was removed in vacuo,
and the yellow product was extracted into 6 mL of toluene. The solution
was filtered and concentrated to 1 mL and was cooled to -30 °C
overnight. Yellow crystals of the product 7 were isolated in 67% yield
(0.162 g) by decanting the supernatant via cannula and drying under
1
vacuum. H NMR (benzene-d6): δ 7.78 (d, 4H, o-Ph), 7.28 (t, 4H,
m-Ph), 7.22 (m, 2H, Ar-H), 7.01 (m, 2H, Ar-H), 6.95 (m, 1H, Ar-
H), 6.91 (m, 2H, Ar-H), 2.93 (s, 2H, SiCH2Ph), 1.77 (s, 15H, C5Me5),
1.31 (d, 6H, 2PMe, JHP ) 8 Hz), 1.04 (d, 6H, 2PMe, JHP ) 7 Hz), 0.9
(m, 2H, 2PCH2), 0.8 (m, 2H, 2PCH2), -6.16 (t, 2H, W(H)2, JHP ) 35
Hz, JHW ) 31 Hz, JHSi ) 12 Hz). 13C{1H} NMR (benzene-d6): δ 148.0,
145.8, 138.1, 129.1, 127.2, 126.4, 126.0, 125.7 (s, Ar), 91.1 (s, C5-
Me5), 41.7 (s, SiCH2Ph), 35.6 (m, 2PMe), 26.6 (m, 2PMe), 16.7 (m,
2PCH2), 12.1 (s, C5Me5). 31P{1H} NMR (benzene-d6): δ 14.33 (s, 183
W
satellites, JPW ) 244 Hz). 29Si{1H} NMR (benzene-d6): δ 28.6 (s). IR
(KBr, cm-1): 1932 w (νWH), 1861 m (νWH). Anal. Calcd for C35H50P2-
SiW: C, 56.45; H, 6.77. Found: C, 56.56; H, 7.01.
9
4384 J. AM. CHEM. SOC. VOL. 126, NO. 13, 2004

Synthons for Complexes of Tungsten
A R T I C L E S
into a 10 mL Schlenk flask to remove LiCl. Pentane (5 mL) was
carefully layered onto the product solution, and the flask was stoppered.
Over 7 d at room temperature, the pentane diffused into the fluoroben-
zene solution, precipitating 0.156 g (65% yield) of 8c as orange crystals.
1H NMR (fluorobenzene): δ 1.83 (s, 15H, C5Me5), 1.42 (d, 6H, 2PMe,
JHP ) 8 Hz), 1.40 (m, 2H, 2PCH2), 1.20 (m, 2H, 2PCH2), 1.12 (d, 6H,
stand at room temperature. Red crystals formed overnight, and the
supernatant was decanted via cannula. The crystals were dried under
reduced pressure to give 0.109 g of 9 (68% yield). 1H NMR
(fluorobenzene): δ 8.38 (m, 2H, o-py), 7.35 (m, 1H, p-py), 7.21 (m,
2H, m-py), 1.69 (s, 15H, C5Me5), 1.44 (m, 2H, 2PCH2), 1.23 (d, 6H,
2PMe, JHP ) 8 Hz), 1.18 (m, 2H, 2PCH2), 1.08 (d, 6H, 2PMe, JHP
)
2PMe, JHP ) 7 Hz), 0.89 (s, 6H, SiMe2), -5.90 (m, 2H, W(H)2, JHW
)
7 Hz), 0.54 (s, 6H, SiMe2), -8.25 (dd, 2H, W(H)2, JHP ) 21 Hz, JHP′
) 36 Hz, JHW ) 47 Hz). 13C{1H} NMR (fluorobenzene): δ 150.4,
148.5, 138.2, 136.3 (m, B(C6F5)4), 149.9, 145.5, 137.2 (s, py), 95.5 (s,
C5Me5), 34.0 (dd, 2PCH2, JHP ) 12 Hz, JHP′ ) 21 Hz), 26.1 (dd, 2PMe,
JHP ) 6 Hz, JHP′ ) 33 Hz), 20.1 (d, 2PMe, JHP ) 22 Hz), 17.5 (s,
SiMe2), 13.3 (s, C5Me5). 31P{1H} NMR (fluorobenzene): δ 15.5 (s,
JPW ) 245 Hz). 29Si{1H} NMR (fluorobenzene): δ 85 (m). IR (KBr,
cm-1): 1870 w (νWH), 1844 w (νWH). Anal. Calcd for C47H44BF20NP2-
SiW: C, 43.85; H, 3.44. Found: C, 44.10; H, 3.31.
48 Hz). 13C{1H} NMR (fluorobenzene): δ 150.4, 148.6, 138.7, 136.3
(m, B(C6F5)4), 100.3 (s, C5Me5), 32.7 (m, 2PCH2), 29.7 (m, 2PMe),
27.1 (s, SiMe2), 17.2 (m, 2PMe), 12.5 (s, C5Me5). 31P{1H} NMR
(fluorobenzene): δ 13.4 (s, JPW ) 221 Hz). 29Si{1H} NMR (fluoroben-
zene): δ 314 (t, JSiP ) 11 Hz). IR (KBr, cm-1): 1949 vw br (νWH),
1868 vw br (νWH). Anal. Calcd for C42H39BF20P2SiW: C, 41.74; H,
3.25. Found: C, 42.02; H, 3.53.
[Cp*(dmpe)(H2)WdSi(H)Dipp][B(C6F5)4] (8d). A Schlenk flask
was charged with 0.100 g (0.198 mmol) of 1, 0.173 g (0.198 mmol) of
Li(Et2O)2.5B(C6F5)4, and 0.038 g (0.198 mmol) of DippSiH3, and 4 mL
of fluorobenzene was added to the flask via cannula. The orange
solution was heated at 70 °C for 1 h. The solution was then filtered to
remove LiCl, and the volatile materials were removed under reduced
pressure, giving 8d as an orange oily solid. The flask was then cooled
to -196 °C to solidify the oil. With a bar magnet, the stirbar was
employed to scrape the solid from the walls of the flask. Drying this
material under vacuum at low temperature for 5 min and at room
temperature for 1 h yielded 0.151 g of 8d (57% yield) as an orange
[Cp*(dmpe)W(H)Cl2][B(C6F5)4] (10). A sealable flask was charged
with 0.060 g (0.050 mmol) of 8c in 0.8 mL of fluorobenzene. The
solution was degassed, and the headspace was backfilled with 1 atm
of MeCl. Heating the flask in an oil bath at 70 °C for 30 min gave a
red-colored solution. The product solution was layered with 2 mL of
pentane and allowed to stand overnight, resulting in formation of red
crystals of 10. The product was isolated by decanting the supernatant
and drying under vacuum to give 0.024 g (44% yield) of 10 as red
1
crystals. Compound 10 exhibits no H or 31P{1H} NMR resonances
due to its paramagnetism. EPR (fluorobenzene): g ) 1.97 (complex
1
powder. H NMR (fluorobenzene): δ 10.83 (s, 1H, SiH, JHSi ) 167
multiline pattern observed due to hyperfine coupling to 35Cl, 37Cl, 31P,
Hz, JHW ) 17 Hz), 3.09 (septet, 2H, 2CHMe2, JHH ) 7 Hz), 1.98 (s,
15H, C5Me5), 1.50 (d, 2PMe, JHP ) 8 Hz), 1.5 (m, 2H, 2PCH2), 1.4
(m, 2H, 2PCH2), 1.25 (d, 12H, 2CHMe2, JHH ) 7 Hz), 1.21 (d, 6H,
2PMe, JHP ) 8 Hz), -4.1 (m, 2H, W(H)2, JHW ) 39 Hz). 13C{1H}
NMR (fluorobenzene): δ 151.4 (Ar-Dipp), 150.4, 148.6 (br, B(C6F5)4),
145.0 (Ar-Dipp), 138.3, 136.5 (br, B(C6F5)4), 132.0, 123.6 (Ar-Dipp),
101.0 (C5Me5), 36.0 (2CHMe2), 32.5 (m, 2PCH2), 28.1 (m, 2PMe),
24.4 (2CHMe2), 16.2 (m, 2PMe), 12.1 (C5Me5). 31P{1H} NMR
1
and H ligands). IR (Nujol, cm-1): 1879 vw (νWH). Anal. Calcd for
C40H32BCl2F20P2W: C, 39.37; H, 2.64. Found: C, 39.76; H, 2.63.
Acknowledgment. We thank the National Science Foundation
for their generous support of this work, and Dr. Rudi Nunlist
for valuable discussions. We also thank Drs. Fred Hollander
and Dana Caulder of the CHEXRAY X-ray crystallography
facility at U.C. Berkeley for obtaining the crystal structure of
1.
1
(fluorobenzene): δ 12.3 (s, JPW ) 209 Hz). H, 29Si HMQC (fluo-
robenzene): δ 286 (SiH, JSiH ) 167 Hz). IR (KBr, cm-1): 2118 w
(νSiH), 1864 w (νWH). Anal. Calcd for C52H51BF20P2SiW: C, 46.58; H,
3.83. Found: C, 46.96; H, 4.00.
Supporting Information Available: Infrared spectral data for
the reported complexes (PDF), and crystallographic information
files (CIF) for 1, 4, 5, 6b, 7, 8c, and 10. This material is available
free of charge via the Internet at http://pubs.acs.org.
[Cp*(dmpe)(H)2WdSiMe2(py)][B(C6F5)4] (9). To a solution of
0.150 g (0.124 mmol) of 8c in 4 mL of fluorobenzene was added 12
µL (0.15 mmol) of pyridine, and the solution immediately changed
color from orange to dark red. Pentane (6 mL) was carefully layered
on top of the red solution, and the flask was sealed and allowed to
JA030548G
9
J. AM. CHEM. SOC. VOL. 126, NO. 13, 2004 4385