Interligand H?Si interactions in tungsten silyl trihydride complexes

Article abstract of DOI:10.1016/j.jorganchem.2010.11.046

The dichloride complex Cp*(Am)WCl₂ (1, Am = [(iPrN) ₂CMe]^-) reacted with the primary silanes PhSiH ₃, (p-tolyl)SiH₃, (3,5-xylyl)SiH₃, and (C ₆F₅)SiH₃ to pro

Full text of DOI:10.1016/j.jorganchem.2010.11.046

Journal of Organometallic Chemistry 696 (2011) 1325e1330
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Interligand H/Si interactions in tungsten silyl trihydride complexes
*
Meg E. Fasulo, T. Don Tilley
Department of Chemistry, University of California Berkeley, Berkeley, CA 94720-1460, USA
a r t i c l e i n f o
a b s t r a c t
The dichloride complex Cp*(Am)WCl2 (1, Am [ [(iPrN)2CMe]ꢀ) reacted with the primary silanes PhSiH3,
(p-tolyl)SiH3, (3,5-xylyl)SiH3, and(C6F5)SiH3 to producetheW(VI) (silyl)trihydrides Cp*(Am)W(H)3(SiHPhCl)
(2), Cp*(Am)W(H)3(SiHTolylCl) (3), Cp*(Am)W(H)3(SiHXylylCl) (4), and Cp*(Am)W(H)3[SiH(C6F5)Cl] (5). In
an analogous manner, 1 reacted with PhSiH2Cl to give Cp*(Am)W(H)3(SiPhCl2) (6). Complex 6 can alterna-
tively be quantitatively produced from the reaction of 2 with Ph3CCl. NMR spectroscopic studies and X-ray
crystallography revealaninterligandH/Siinteraction between oneWeH andthe chlorosilyl group, which is
further supported by DFT calculations.
Article history:
Received 11 November 2010
Accepted 27 November 2010
Keywords:
Tungsten complexes
Silyl complexes
Amidinate ligand
Published by Elsevier B.V.
1. Introduction
interactions [13e16], and such species have been proposed as
intermediates in catalytic transformations of organosilanes
In recent years the use of amidinates as ligands for early tran-
sition metal complexes has gained considerable popularity [1e3].
Amidinates are easily synthesized and can be readily modified to
induce either small or drastic steric and electronic changes.
Futhermore, multiple methods for installing amidinate ligands
onto metal fragments have proven effective [4,5]. Amidinate-sup-
ported Group 4 complexes are active olefin polymerization cata-
lysts, and the amidinate ligand is not directly involved in observed
reactivity [6e9]. Recent work from Sita and co-workers with Group
6 complexes of the type Cp*(Am)MCl2 (Am ¼ [(iPrN)2CMe]ꢀ;
M ¼ Mo, W) [10] inspired the exploration of reactivity of Cp*(Am)
WCl2 (1) with organosilanes.
[17e20]. An interligand hypervalent interaction is described as
involving primarily electron donation from a metal hydride bond
into an antibonding orbital of a siliconeX bond, where X is a good
leaving group. This interaction results in elongation of the SieX
bond, shortening of the MeSi bond, and often but not always,
increased SieH coupling constants [15,21]. Such interactions have
been well documented for Ru, Ta, and Nb complexes [22e26].
2. Results and discussion
2.1. Reactions of primary silanes with Cp*(Am)WCl2
Research in this laboratory has focused on fundamental chem-
istry involving SieH activations and the formation of silylene
Complex 1 was found to react with a 5-fold excess of phenyl-
silane at 80 ꢁC over 24 h in toluene to give Cp*(Am)W(H)3(SiHRCl)
(2) as a light brown solid in 42% yield after recrystallization from
pentane at ꢀ30 ꢁC (Eq. (1)). The yield is significantly lowered by the
similar solubility properties of 2 and phenylsilane, making isolation
of pure 2 difficult. In an analogous manner, 1 was found to react
with p-tolylsilane, 3,5-xylylsilane, and (pentafluorophenyl)silane to
give complexes 3e5, respectively. Reactions with the bulkier
silanes MesSiH3, TripSiH3, and DMPSiH3 did not proceed, even with
heating at 80 ꢁC for one week, presumably for steric reasons.
The 1H NMR spectrum of 2 contains three chemically inequi-
valent hydride resonances at 5.24 ppm (JSiH ¼ < 7 Hz), 0.92 ppm
(JSiH ¼ 11.1 Hz), and ꢀ1.28 ppm (JSiH ¼ 24.6 Hz). The SieH resonance
at 8.41 ppm (JSiH ¼ 199.5 Hz) is shifted downfield relative to that of
the free silane (4.23 ppm). The 29Si NMR spectrum contains a single
resonance for the silyl ligand at 43.9 ppm. The isopropyl groups of
the ligand exhibit two methine resonances and four methyl
complexes. In particular, [(h
7-C5Me3(CH2)2)(dmpe)W(H)2][B
(C6F5)4]has been showntoperform double SieHactivations toresult
in high oxidation state silylene complexes of the type [Cp*(dmpe)
W ¼ SiR2][B(C6F5)4] [11,12]. Similar chemistry was envisioned to
occur with a Cp*(amidinate)W fragment, such as Cp*(Am)WR2.
Herein we present the synthesis of new tungsten complexes sup-
ported by the amidinate ligand (Am ¼ [(iPrN)2CMe]ꢀ) in which
a non-classical Si/H interaction is observed.
A number of interesting non-classical interactions have been
observed in organometallic complexes containing silicon, which
have been characterized as involving
s-complexes (h -
2- and h3
silane complexes), agostic interactions, and interligand hypervalent
* Corresponding author. Tel.: þ1 510 642 8939; fax: þ1 510 642 8940.
E-mail addresses: tdtilley@socrates.berkeley.edu, tdtilley@berkeley.edu(T.D. Tilley).
0022-328X/$ e see front matter Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2010.11.046

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M.E. Fasulo, T.D. Tilley / Journal of Organometallic Chemistry 696 (2011) 1325e1330
resonances, indicating C1 symmetry for the complex. Tungsten
satellites were observable for the hydride resonances, and the
WeH coupling constant for all hydrides of ca. 40 Hz is similar to
those reported for [C5Me5(dmpe)W(H)2]-based compounds [11,12].
The NMR data for complexes 3e5 follow similar trends (Table 1).
The NMR spectra were found to remain unchanged over the
temperature range of ꢀ50e80 ꢁC. Using the inversion recovery
method, the minimum T1 relaxation times were found to be 950
(Ha), 800 (Hb), and 980 ms (Hc), indicative of classical hydrides.
Complex6 canalternativelybesynthesized from reactionof 2 with
oneequivof trityl chlorideat 60 ꢁC for 4 h intoluene, quantitatively by
NMR spectroscopy (Eq. (3)). This method is a more convenient route
to the dichlorosilyl species. Complex 6 does not react further with
Ph3CCl in C6D6 at 100 ꢁC for 24 h. Thus, the SieH bond of 2 appears to
represent the most hydridic center in these type of complexes.
(3)
(1)
Comparison of the NMR spectra of complexes 2 and 6 allows for
definitive assignments of the hydride resonances (Fig. 1). Thus, the
resonance at ca. 5 ppm (Ha) observed in 2 and 6 corresponds to
a hydride ligand that is trans to the Cp* ligand. The shift at ca. 1 ppm
(Hb)for2and6correspondsto hydride ligands in close proximity tothe
Cl atom of the silyl ligand. The furthest upfield signal at ca. ꢀ1 ppm (Hc),
observed only in 2, correlates to the hydride nearest to the SieH group.
In complex 2, Hc exhibits the largest coupling to Si (JSiH ¼ 24.6 ppm).
This increased coupling is suggestive of a significant Si/HeW inter-
action (IHI). Hc is approximately trans to the Cl group on silicon,
allowing for overlap with the SieCl antibonding orbital. Two such
interactions are seen in complex 6with the Hb hydrides (JSiH ¼ 17.8 Hz).
Complexes 2e5 appear to be quite stable and relatively
unreactive. Heating at 100 ꢁC for 24 h in C6D6 resulted in no
detectable decomposition of 2 (by 1H NMR spectroscopy). Addition
of an excess of PMe3 to 2 gave no reaction with heating to 100 ꢁC for
24 h. Reactions with diphenylacetylene, benzophenone, aceto-
phenone, norbornene, and 3,3-dimethylbut-1-ene did not proceed
at room temperature but resulted in numerous unidentified
organometallic species upon heating to 80 ꢁC for 6 h.
2.3. Solid-state structure of 2
2.2. Reactions of secondary silanes with Cp*(Am)WCl2
Suitable crystals of 2 for single-crystal X-ray diffraction were
grown by slow evaporation of pentane at room temperature over
one week. The X-ray structure of 2 reveals a 3-legged piano stool
geometryof theCp*, amidinateligand, andsilyl ligands aboutW, and
the WeSi bond length of 2.490(4) Å is typical for a WeSi single bond
(Fig. 2). The N(1)eW(1)eN(2) angle of 63.5(4)ꢁ is as expected for an
amidinate ligand, and the silyl group is canted slightly towards N(2)
as seen by the N(1)eW(1)eSi(1) angle of 124.9(3)ꢁ and the N(2)eW
(1)eSi(1) angle of 113.3(3)ꢁ. The elongated SieCl bond length of
2.138(5) Å supports the identification of an interligand H/Si inter-
action between a WeH and the SieCl antibonding orbital. Due to
insufficient data, the hydrides were not located.
A similar compound, Cp*(CO)2W(H)2(SiHCl2), has been reported
in the literature [27]. Interestingly, this complex adopts a pseudo-
octahedral structure (with the Cp* ligand considered as occupying
a single site) and has a WeSi bond length of 2.4902(9) Å. This is
a significantly different geometry than that observed for 2. Addi-
tionally, both WeH bonds of Cp*(CO)2W(H)2(SiHCl2) interact much
more strongly with the silicon center, based on the Si/H distances
of 1.91(3) and 1.90(3) Å. Coupling constants were not reported for
this compound. Although two interligand hypervalent interactions
have been implicated for the lengthened SieCl bonds (2.0981(14)
and 2.1084(13) Å), the SieCl distance in 2 is slightly longer, indi-
cating a stronger interaction, and this would be consistent with
a more electron-rich W center in 2.
In reactions of primary silanes with complex 1, use of less than
5 equiv of RSiH3 resulted in a tertiary silyl-containing product (vida
infra). It was therefore of interest to explore the reactivity of 1 with
secondary silanes in order to isolate such species. Using the same
reaction conditions employed for the synthesis of 2e5, complex 1
was found to react with H2SiPhCl to afford Cp*(Am)W(H)3(SiPhCl2)
(6) as a light green solid in 27% isolated yield (Eq. (2)). The 1H NMR
spectrum reveals only two inequivalent hydride resonances, inte-
grating for three hydrides total, at 4.61 ppm (1H, JSiH ¼ 9.9 Hz) and
1.05 ppm (2H, JSiH ¼ 17.8 Hz). The 29Si NMR spectrum displays
a single resonance at 47.8 ppm. Interestingly, the isopropyl groups
of the amidinate ligand are equivalent, indicating that the ligand
lies on a plane of symmetry. Reactions of 2 with the secondary
silanes Ph2SiH2, Et2SiH2, and MesClSiH2 did not proceed after one
week of heating at 80 ꢁC in C6D6.
(2)
Table 1
NMR data for complexes 2e5.
Complex
d
1H (Ha) (2JSiH
)
d
1H (Hb) (2JSiH
)
d
1H (Hc) (2JSiH
)
d
1H (SiH) (1JSiH
)
d
29Si
Cp*(Am)WH3(SiHPhCl) (2)
Cp*(Am)WH3(SiHTolylCl) (3)
Cp*(Am)WH3(SiHXylylCl) (4)
Cp*(Am)WH3[SiH(C6F5)Cl] (5)
5.24 (<7)
5.35 (14.4)
5.39 (7.8)
4.74 (22.7)
0.92 (11.1)
0.95 (9.3)
0.94 (15.4)
0.58 (10.6)
ꢀ1.28 (24.6)
ꢀ1.15 (26.5)
ꢀ1.11 (31.9)
ꢀ1.61 (21.6)
8.41 (199.5)
8.44 (198.0)
8.43 (198.1)
8.52 (215.5)
43.9
43.2
43.3
22.1

M.E. Fasulo, T.D. Tilley / Journal of Organometallic Chemistry 696 (2011) 1325e1330
1327
Fig. 1. Assignment of hydrides based on NMR spectroscopy.
2.4. DFT calculations of 2
Because the hydride ligands of 2 were not located by X-ray
crystallography, DFT calculations at the B3LYP/LANL2DZ level of
theory were undertaken. Using the crystal structure as a starting
point, several different arrangements of the hydrides were mini-
mized, resulting in the lowest energy structure shown in Fig. 3. The
bond distances and angles are in agreement with those observed by
X-ray crystallography, including the elongated SieCl bond distance
of 2.16 Å. One hydride, Ha, is located trans to the Cp* centroid, with
a WeH bond distance of 1.69 Å. The other two hydride ligands
occupy the open pockets between the amidinate and silyl ligands.
The WeH group cis to Cl, Hb, is associated with a bond distance of
1.68 Å. The other hydride, Hc, is approximately trans (156ꢁ) to the Cl
atom on the silyl group and is involved with a slightly longer WeH
bond distance of 1.71 Å. Additionally, Hc is associated with the
shortest SieH distance (2.10 Å). These structural features correlate
well with the structure hypothesized from NMR data.
Fig. 3. Optimized geometry of Cp*(Am)W(H)3(SiHPhCl).
To further probe the nature of the H/Si interactions in 2, NMR
spinespin coupling predictions and NBO calculations were per-
formed. The following JSiꢀH values were found: Ha ¼ 2 Hz,
Hb ¼ 11 Hz, and Hc ¼ 39 Hz. These coupling constants agree very
well with experimentally obtained values (Ha ꢂ 7 Hz, Hb ¼ 11.1 Hz,
and Hc ¼ 24.6 Hz) and indicate that Hc has the strongest interaction
with Si. The other two hydride ligands show little SieH bonding.
Donation from the WeHc bonding orbital to the SieCl antibonding
orbital was found to be present in the NBO analysis. Additional
weak interactions between all WeH bonding orbitals and the WeSi
antibonding orbital were identified.
2.5. Proposed mechanism
Several experiments were conducted to probe the reaction
mechanism for the formation of a chlorosilyl ligand starting from
a primary silane. Under the reaction conditions of Eq. (1), lower
quantities of phenylsilane (2e4 equiv) resulted in unreacted 1,
complex 2, and a side product, Cp*(Am)W(H)3(SiPhCl2) (6), as
determined from an independently synthesized sample. For
example, 3 equiv of phenylsilane was found to react with 1 at 80 ꢁC
for 16 h to give 10% of 1, 20% of 6, and 70% of 2 by NMR spectros-
copy. The use of 5 equiv or more of phenylsilane cleanly yielded 2,
along with 1 equiv H2SiPhCl and 3 equiv of unreacted PhSiH3.
Complex 1 was heated to 80 ꢁC for 24 h with 25 equiv of PhSiH3 to
give only 2 and 1 equiv of PhSiH2Cl. Similarly, 1 was heated to 80 ꢁC
for 24 h with 25 equiv of PhSiH2Cl to give only 6 and 1 equiv of
PhSiHCl2. Thus, the complex with more chloro substituents on the
silyl group appears to be the most stable product. Additionally, the
formation of strong SieCl bonds appears to be a driving force of the
reaction. For comparison, the analogous treatment of 1 with 5 equiv
PhGeH3 in C6D6 for 24 h at 80 ꢁC results in no reaction.
The proposed mechanism, detailed in Fig. 4, involves a series of
SieH bond oxidative additions and SieCl bond reductive elimina-
tions. DFT calculations were performed to determine the thermody-
namic stability of each proposed intermediate, taking into account
both the complexes and organosilanes. The formation of Cp*(Am)
Fig. 2. Molecular structure of 2 displaying thermal ellipsoids at the 50% probability
level. H-atoms have been omitted for clarity. Selected bond lengths (Å): W(1)eSi
(1) ¼ 2.490(4), Si(1)eCl(1) ¼ 2.138(5), W(1)eN(1) ¼ 2.138(11), W(1)eN(2) ¼ 2.089(11).
Selected angles (deg.): N(1)eW(1)eN(2) ¼ 63.5(4), N(1)-W(1)eSi(1) ¼ 124.9(3), N(2)e
W(1)-Si(1) ¼ 113.3(3).

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M.E. Fasulo, T.D. Tilley / Journal of Organometallic Chemistry 696 (2011) 1325e1330
Fig. 4. Proposed mechanism for the formation of complex 2 (relative energies indicated).
WHCl from 1 and the subsequent formation of Cp*(Am)WH2 appear
to be essentially isoenergetic. Further reaction to form the isolable
product 2 is downhill by 15 kcal/mol. Formation of the Cp*(Am)
H3(SiH2Ph) is calculated to be ca. 3 kcal/mol less favorable than 2,
large enough to explain the exclusive observation of 2.
Multiple attempts to isolate or observe the Cp*(Am)WH2 species
were undertaken to gain further insight into the formation of 2. No
reaction was observed after heating 1 with an excess of Et3SiH in
C6D6 for 24 h at 80 ꢁC. Complex 1 was also unreactive towards
nBu3SnH under identical conditions. Conversely, reactions with
reagents such as LiEt3BH, LiAlH4, and NaBH4 resulted in complex
mixtures of products. Additionally, conversion of 1 to Cp*(Am)WR2
complexes using MeMgCl, Bn2Mg, nBuLi, and MeLi resulted in
multiple unidentified products. In all experiments, no evidence for
the targeted complex was observed.
glovebox. Olefin impurities were removed from pentane by treat-
ment with concentrated H2SO4, 0.5 N KMnO4 in 3 M H2SO4, and
NaHCO3. Pentane was then dried over MgSO4 and stored over
activated 4 Å molecular sieves, and dried over alumina. Thiophene
impurities were removed from benzene and toluene by treatment
with H2SO4 and saturated NaHCO3. Toluene and pentane were
dried over Na and distilled under N2. Benzene-d6 was dried by
vacuum distillation from Na/K alloy.Cp*(Am)WCl2 (1) was prepared
according to literature methods [10]. All other chemicals were
purchased from commercial sources and used without further
purification.
NMR spectra were recorded using Bruker AVB 400, AV-500 or
AV-600 spectrometers equipped with a 5 mm BB probe. Spectra
were recorded at room temperature and referenced to the residual
protonated solvent for 1H. 31P{1H} NMR spectra were referenced
relative to 85% H3PO4 external standard (
d
¼ 0). 13C{1H} NMR
spectra were calibrated internally with the resonance for the
solvent relative to tetramethylsilane. For 13C{1H} NMR spectra,
resonances obscured by the solvent signal are omitted. 29Si NMR
spectra were referenced relative to a tetramethylsilane standard
and obtained via 2D 1H 29Si HMBC unless specified otherwise.
Elemental analyses were performed by the College of Chemistry
Microanalytical Laboratory at the University of California, Berkeley.
3. Concluding remarks
In conclusion, a variety W(VI) silyl trihydride complexes are
accessable starting from the W(IV) complex, Cp*(Am)WCl2. Multiple
SieH bond activations are proposed for the formation of such
complexes. Limitations of silane activations appear to be driven by
steric bulk, and one driving force for the reaction seems to be the
formation of SieCl bonds. An interligand interaction between one
WeH bond and the silyl ligand is observed by NMR spectroscopy and
X-ray crystallography e specifically an increased SieH coupling
constant and elongated SieCl bond. DFT calculations support the
4.2. Cp*(Am)W(H)3(SiHPhCl) (2)
To
a 20 mL toluene solution of Cp*(Am)WCl2 (0.100 g,
experimental
findings.
Additionally,
Cp*(Am)WH3(SiHPhCl)
0.188 mmol) was added an excess of phenylsilane (0.108 g,
1.00 mmol). The reaction mixture was stirred at 80 ꢁC for 24 h, after
which the resulting transparent brown solution was evacuated to
dryness. The remaining brown residue was then dissolved in 15 mL
pentane, and the solution was filtered through Celite. The solution
was then concentrated to approximately 2 mL and cooled to
ꢀ35 ꢁC. The brown precipitate was isolated by decantation and
drying under vacuum to give a light tan solid in 42% yield (0.045 g,
undergoes SieH activation with CPh3Cl to selectively form Cp*(Am)
WH3(SiPhCl2). All attempts to synthesize complexes of the type Cp*
(Am)WR2 (R ¼ H, aryl, alkyl) have so far been unsuccessful. Reactions
of hydrosilanes inthis Cp*(Am)Wsystem appearto bestrongly driven
to hexavalent hydrido silyl species such as those described above.
4. Experimental
0.079 mmol). 1H NMR (C6D6, 600 MHz):
d
8.41 (1H, d, J ¼ 5.8 Hz,
4.1. General considerations
1JSiH ¼ 199.5 Hz, SiH), 8.16 (2H, d, J ¼ 7.4 Hz, ArH), 7.34 (2H, t,
J ¼ 7.4 Hz, ArH), 7.17 (1H, t, J ¼ 7.4 Hz, ArH), 5.24 (1H, m,
1JWH ¼ 34.0 Hz, WH), 3.24 (1H, sept, J ¼ 6.5 Hz, CHiPr2), 3.07 (1H,
sept, J ¼ 6.5 Hz, CHiPr2), 1.76 (15H, s, C5Me5), 1.26 (3H, s, CMe), 1.15
All experiments were carried out under a nitrogen atmosphere
using standard Schlenk techniques or an inert atmosphere (N2)

M.E. Fasulo, T.D. Tilley / Journal of Organometallic Chemistry 696 (2011) 1325e1330
1329
(3H, d, J ¼ 6.5, CHiPr2), 1.03 (3H, d, J ¼ 6.5, CHiPr2), 0.92 (1H, dd,
4.6. Cp*(Am)W(H)3(SiPhCl2) (6)
J ¼ 4.5 Hz, 9.5 Hz, 1JSiH ¼ 11.1 Hz, 1JWH ¼ 45.8 Hz, WH), 0.76 (3H, d,
J ¼ 6.5, CHiPr2), 0.58 (3H, d, J ¼ 6.5, CHiPr2), ꢀ1.28 (1H, m,
By a procedure analogous to that for 2, complex 6 was obtained
1
1JSiH ¼ 24.6 Hz, JWH ¼ 47.6 Hz, WH). 13C{1H} NMR (C6D6,
as a light green solid in 27% yield (0.040 g, 0.063 mmol). 1H NMR
150.9 MHz): 173.9 (CMe),151.7 (ArC),133.24 (ArC),127.9 (ArC),129.1
(ArC), 103.0 (C5Me5), 49.3 (CHiPr2), 49.0 (CHiPr2), 25.5 (CHiPr2), 24.9
(CHiPr2), 23.9 (CHiPr2), 23.8 (CHiPr2), 15.2 (CMe), 10.6 (C5Me5). 29Si
(C6D6, 600 MHz):
d
8.38 (2H, d, J ¼ 7.5 Hz, ArH), 7.34 (2H, t,
J ¼ 7.5 Hz, ArH), 7.09 (1H, t, J ¼ 7.4 Hz, ArH), 4.61 (1H, t, J ¼ 8.5,
1
1JSiH ¼ 9.9 Hz, JWH ¼ 25.7 Hz, WH), 3.16 (2H, sept, J ¼ 7.0 Hz,
NMR (C6D6, 99.4 MHz):
d
43.9. Anal. Calcd for C24H41N2ClSiW: C,
CHiPr2), 1.87 (15H, s, C5Me5), 1.19 (3H, s, CMe), 1.05 (2H, d, J ¼ 8.5,
1
47.65; H, 6.84; N, 4.63. Found: C, 47.54; H, 6.91; N, 4.57.
1JSiH ¼ 17.8 Hz, JWH ¼ 32.8 Hz, WH), 0.89 (12H, ov dd, J ¼ 7.0,
CHiPr2). 13C{1H} NMR (C6D6, 150.9 MHz): 173.9 (CMe), 151.7 (ArC),
133.24 (ArC), 127.9 (ArC), 129.1 (ArC), 103.0 (C5Me5), 49.3 (CHiPr2),
49.0 (CHiPr2), 25.5 (CHiPr2), 24.9 (CHiPr2), 23.9 (CHiPr2), 23.8
(CHiPr2), 15.2 (CMe), 10.6 (C5Me5). 29Si NMR (C6D6, 99.4 MHz):
4.3. Cp*(Am)W(H)3(SiH(Tolyl)Cl) (3)
By a procedure analogous to that for 2, complex 3 was obtained
as a light tan solid in 34% yield (0.040 g, 0.065 mmol). 1H NMR
d
47.8. Anal. Calcd for C24H40N2Cl2SiW: C, 45.08; H, 6.31; N, 4.38.
8.44 (1H, d, J ¼ 5.9 Hz, 1JSiH ¼ 198.0 Hz, SiH), 8.14
Found: C, 45.80; H, 6.24; N, 3.98.
(C6D6, 600 MHz):
d
(2H, d, J ¼ 7.8 Hz, ArH), 7.21 (2H, d, J ¼ 7.8 Hz, ArH), 5.35 (1H, m,
1
1JSiH ¼ 14.4 Hz, JWH ¼ 35.4 Hz, WH), 3.29 (1H, sept, J ¼ 6.6 Hz,
4.7. X-ray crystallography
CHiPr2), 3.16 (1H, sept, J ¼ 6.6 Hz, CHiPr2), 2.21 (3H, s, ArCH3), 1.81
(15H, s, C5Me5), 1.32 (3H, s, CMe), 1.18 (3H, d, J ¼ 6.6, CHiPr2), 1.07
(3H, d, J ¼ 6.6, CHiPr2), 0.95 (1H, dd, J ¼ 5.1 Hz, 9.5 Hz, 1JSiH ¼ 9.3 Hz,
1JWH ¼ 32.2 Hz, WH), 0.83 (3H, d, J ¼ 6.6, CHiPr2), 0.68 (3H, d, J ¼ 6.6,
CHiPr2), ꢀ1.15 (1H, m, 1JSiH ¼ 26.5 Hz, 1JWH ¼ 47.3 Hz, WH). 13C{1H}
NMR (C6D6, 150.9 MHz): 173.8 (CMe), 148.2 (ArC), 136.8 (ArC), 133.5
(ArC), 127.9 (ArC), 102.9 (C5Me5), 49.3 (CHiPr2), 49.0 (CHiPr2), 25.5
(CHiPr2), 25.1 (CHiPr2), 24.0 (CHiPr2), 23.9 (CHiPr2), 21.0 (ArCH3),
The X-ray analysis of 2 was carried out at UC Berkeley CHEXRAY
crystallographic facility. Measurements were made on an APEX CCD
area detector with graphite-monochromated Mo K
a radiation
(
l
¼ 0.71069 Å). Data was integrated and empirical absorption
corrections were made using the APEX2 program package. The
structure as solved by direct methods and expanded using Fourier
techniques. All calculations were performed using the SHELXTL
crystallographic package. Non-hydrogen atoms were refined
anisotropically and hydrogen atoms were placed in calculated
positions.
15.2 (CMe), 10.7 (C5Me5). 29Si NMR (C6D6, 99.4 MHz):
d 43.2. Anal.
Calcd for C26H45N2ClSiW: C, 48.51; H, 7.00; N, 4.53. Found: C, 49.01;
H, 6.68; N, 3.94.
4.8. Computational details
4.4. Cp*(Am)W(H)3(SiH(Xylyl)Cl) (4)
All calculations were performed in the molecular graphics and
computing facility of the College of Chemistry, University of Cal-
ifornia, Berkeley (NSF grant CHE-0233882). Calculations were
performed using the Gaussian ’09 suite of programs [28] at the
B3LYP/LANL2DZ level of theory with LANL2DZdp ECP polarization
functions for W [29]. The crystal structures of 1 and 2 were used as
starting geometries. Vibrational frequencies were calculated for all
converged structures and confirm that these structures lie on
a minimum. Graphical representations of the structures were
generated using Mercury. The natural bond orbital (NBO) program
in Gaussian 03 was utilized to determine the presence of a signifi-
cant interaction between the WeH bonding orbital and the SieCl
antibonding orbital.
By a procedure analogous to that for 2, complex 4 was obtained
as a light tan solid in 37% yield (0.041 g, 0.069 mmol). 1H NMR
(C6D6, 600 MHz):
d
8.43 (1H, d, J ¼ 6.0 Hz, 1JSiH ¼ 198.1 Hz, SiH), 7.88
1
(2H, s, ArH), 6.67 (1H, s, ArH), 5.39 (1H, m, JSiH ¼ 7.8 Hz,
1JWH ¼ 36.7 Hz, WH), 3.28 (1H, sept, J ¼ 6.5 Hz, CHiPr2), 3.19 (1H,
sept, J ¼ 6.5 Hz, CHiPr2), 2.28 (6H, s, ArCH3),1.81 (15H, s, C5Me5),1.34
(3H, s, CMe), 1.20 (3H, d, J ¼ 6.5, CHiPr2), 1.07 (3H, d, J ¼ 6.5, CHiPr2),
0.92 (1H, dd, J ¼ 5.5 Hz, 10.4 Hz, 1JSiH ¼ 7.4 Hz, 1JWH ¼ 35.4 Hz, WH),
0.86 (3H, d, J ¼ 6.5, CHiPr2), 0.78 (3H, d, J ¼ 6.5, CHiPr2), ꢀ1.11 (1H, m,
1JSiH ¼ 31.9 Hz, JWH ¼ 46.3 Hz, WH). 13C{1H} NMR (C6D6,
1
150.9 MHz): 173.7 (CMe), 151.1 (ArC), 135.7 (ArC), 131.4 (ArC), 129.4
(ArC), 102.9 (C5Me5), 49.3 (CHiPr2), 49.1 (CHiPr2), 25.5 (CHiPr2), 25.0
(CHiPr2), 24.0 (CHiPr2), 22.9 (CHiPr2), 21.29 (ArCH3), 21.27 (ArCH3),
15.3 (CMe), 10.6 (C5Me5). 29Si NMR (C6D6, 99.4 MHz):
d 43.3. Anal.
Acknowledgements
Calcd for C26H45N2ClSiW: C, 49.33; H, 7.17; N, 4.43. Found: C, 49.37;
H, 7.18; N, 4.22.
This work was supported by the National Science Foundation
under Grant No. CHE-0649583 and an NSF Graduate Fellowship to
M.E.F.
4.5. Cp*(Am)W(H)3(SiH(C6F5)Cl) (5)
By a procedure analogous to that for 2, complex 5 was obtained
Appendix A. Supplementary material
as a light tan solid in 35% yield (0.046 g, 0.0696 mmol). 1H NMR
(C6D6, 600 MHz):
d
8.52 (1H, br s, 1JSiH ¼ 215.5 Hz, SiH), 4.74 (1H, m,
CCDC 803373 contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
1
1JSiH ¼ 22.7 Hz, JWH ¼ 35.9 Hz, WH), 3.18 (1H, sept, J ¼ 6.5 Hz,
CHiPr2), 2.99 (1H, sept, J ¼ 6.5 Hz, CHiPr2), 1.73 (15H, s, C5Me5), 1.23
(3H, s, CMe), 1.10 (3H, d, J ¼ 6.5, CHiPr2), 0.98 (3H, d, J ¼ 6.5, CHiPr2),
0.66 (3H, d, J ¼ 6.5, CHiPr2), 0.58 (1H, m, JSiH ¼ 10.6 Hz,
1
1JWH ¼ 39.9 Hz, WH), 0.45 (3H, d, J ¼ 6.5, CHiPr2), ꢀ1.61 (1H, m,
References
1JSiH ¼ 21.6 Hz, JWH ¼ 45.8 Hz, WH). 13C{1H} NMR (C6D6,
1
150.9 MHz): 174.9 (CMe), 128.2 (ArC), 127.9 (ArC), 127.5 (ArC), 103.6
(C5Me5), 49.4 (CHiPr2), 48.6 (CHiPr2), 25.1 (CHiPr2), 24.4 (CHiPr2),
23.6 (CHiPr2), 23.5 (CHiPr2), 14.9 (CMe), 10.5 (C5Me5). 29Si NMR
[1] L.R. Sita, Angew. Chem. Int. Ed. 48 (2009) 2464e2472.
[2] R. Gomez, R. Duchateau, A.N. Chernega, J.H. Teuben, F.T. Edelmann,
M.L.H. Green, J. Organomet. Chem. 491 (1995) 153e158.
[3] J.M. Decker, S.J. Geib, T.Y. Meyer, Organometallics 18 (1999) 4417e4420.
[4] L.R. Sita, J.R. Babcock, Organometallics 17 (1998) 5228e5230.
[5] J. Barker, M. Kilner, Coord. Chem. Rev. 133 (1994) 219e300.
(C6D6, 99.4 MHz):
d 22.1. Anal. Calcd for C24H36N2ClFSiW: C, 41.48;
H, 5.22; N, 4.03. Found: C, 41.67; H, 5.13; N, 3.78.

1330
M.E. Fasulo, T.D. Tilley / Journal of Organometallic Chemistry 696 (2011) 1325e1330
[6] A. Epshteyn, E.F. Trunkely, D.A. Kissounko, J.C. Fettinger, L.R. Sita, Organo-
metallics 28 (2009) 2520e2526.
[7] P.P. Fontaine, A. Epshteyn, P.Y. Zavalij, L.R. Sita, J. Organomet. Chem. 692
(2007) 4683e4689.
[24] S.K. Ignatov, N.H. Rees, B.R. Tyrrell, S.R. Dubberley, A.G. Razuvaev,
P. Mountford, G.I. Nikonov, Chem. Eur. J. 10 (2004) 4991e4999.
[25] S.K. Ignatov, N.H. Rees, A.A. Merkoulov, S.R. Dubberley, A.G. Razuvaev,
P. Mountford, G.I. Nikonov, Chem. Eur. J. 14 (2008) 296e310.
[8] M.B. Harney, R.J. Keaton, J.C. Fettinger, L.R. Sita, J. Am. Chem. Soc. 128 (2006)
3420e3432.
[26] S.R. Dubberley, S.K. Ignatov, N.H. Rees, A.G. Razuvaev, P. Mountford,
G.I. Nikonov, J. Am. Chem. Soc. 125 (2002) 642e643.
[9] M.B. Harney, Y. Zhang, L.R. Sita, Angew. Chem. Int. Ed. 45 (2006) 2400e2404.
[10] P.P. Fontaine, B.L. Yonke, P.Y. Zavalij, L.R. Sita, J. Am. Chem. Soc. 132 (2010) 12273.
[11] B.V. Mork, T.D. Tilley, J. Am. Chem. Soc. 123 (2001) 9702e9703.
[12] B.V. Mork, T.D. Tilley, J. Am. Chem. Soc. 126 (2004) 4375e4385.
[13] J.Y. Corey, J. Braddock-Wilking, Chem. Rev. 99 (1998) 175e292.
[14] U. Schubert, Adv. Organomet. Chem. 30 (1990) 151e187.
[15] G.I. Nikonov, J. Organomet. Chem. 635 (2001) 24e36.
[16] C.M. Thomas, J.C. Peters, Angew. Chem. Int. Ed. 45 (2006) 776e780.
[17] C. Beddie, M.B. Hall, J. Am. Chem. Soc. 126 (2004) 13564e13565.
[18] B. Biswas, M. Sugimoto, S. Sakaki, Organometallics 18 (1999) 4015e4026.
[19] S. Sakaki, T. Takayama, M. Sumimoto, M. Sugimoto, J. Am. Chem. Soc. 2126
(2004) 3332e3348.
[27] H. Sakaba, T. Hirata, C. Kabuto, K. Kabuto, J. Organomet. Chem. 692 (2007)
402e407.
[28] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant,
J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi,
G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara,
K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, V. Bakken,
C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin,
R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth,
P. Salvador, J.J. Dannenberg, V. Zakrzewski, S. Dapprich, A.D. Daniels,
M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman,
J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu,
A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-
Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson,
W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian 03, Revision C.02.
Gaussian, Inc., Wallingford, CT, 2004.
[20] N. Schneider, M. Finger, C. Haferkemper, S. Bellemin-Laponnaz, P. Hofmann,
L.H. Gade, Angew. Chem. Int. Ed. 48 (2009) 1609e1613.
[21] S.B. Duckett,L.G. Kuzmina,G.I. Nikonov, Inorg. Chem. Commun.3(1999) 126e128.
[22] S.K. Ignatov, N.H. Rees, A.A. Merkoulov, S.R. Dubberley, A.G. Razuvaev,
P. Mountford, G.I. Nikonov, Organometallics 27 (2008) 5968e5977.
[23] A.L. Osipov, S.F. Vyboishchikov, K.Y. Dorogov, L.G. Kuzmina, J.A.K. Howard,
D.A. Lemenovskii, G.I. Nikonov, Chem. Commun. (2005) 3349e3351.
[29] C.E. Check, T.O. Faust, J.M. Bailey, B.J. Wright, T.M. Gilbert, L.S.J. Sunderlin,
Phys. Chem. A 105 (2001) 8111.