Highly efficient hydrosilylation of alkenes by organoyttrium catalysts with sterically demanding amidinate and guanidinate ligands

Article abstract of DOI:10.1021/om800032g

The sterically demanding guanidine ArNHC(NMe₂)NAr (Ar = 2,6-diisopropylphenyl, HL) reacts with Y(CH₂SiMe₃) ₃(THF)₂ to give the yttrium dialkyl complex (L)Y(CH ₂SiMe₃)₂

Full text of DOI:10.1021/om800032g

Organometallics 2008, 27, 3131–3135
3131
Highly Efficient Hydrosilylation of Alkenes by Organoyttrium
Catalysts with Sterically Demanding Amidinate and Guanidinate
Ligands
Shaozhong Ge, Auke Meetsma, and Bart Hessen*
Center for Catalytic Olefin Polymerization, Stratingh Institute for Chemistry, UniVersity of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands
ReceiVed January 13, 2008
The sterically demanding guanidine ArNHC(NMe2)NAr (Ar ) 2,6-diisopropylphenyl, HL) reacts with
Y(CH2SiMe3)3(THF)2 to give the yttrium dialkyl complex (L)Y(CH2SiMe3)2(THF) (1), which was
structurally characterized. Electronic interaction of the -NMe2 group with the conjugated ligand backbone
can be inferred from structural and spectroscopic data. The new yttrium guanidinate complex 1 and its
related amidinate analogue [PhC(NAr)2]Y(CH2SiMe3)2(THF) (2) are highly active and selective catalysts
for alkene hydrosilylation with PhSiH3 (tof > 600 h-1 at 23 °C). For unfunctionalized olefins, full
selectivity toward anti-Markovnikov products was obtained. The more electron donating guanidinate
ligand affords the highest activities with heteroatom-functionalized substrates.
SiMe3]2 has been reported to catalyze the hydrosilylation of
1-hexene with a similar efficiency and full selectivity for the
anti-Markovnikov product, when a 25% excess of PhSiH3 and
5 mol % of catalyst are used.7j Here we describe highly efficient
and regioselective hydrosilylation catalysis by mono(amidinate)-
and mono(guanidinate)yttrium catalysts. The new guanidinate
catalyst shows a particularly good performance with heteroatom-
containing substrates.
Amidinates and guanidinates have been used extensively as
ligands in organometallic chemistry.8 In recent years, we have
used the sterically demanding amidinates [(C6R5)C(NAr)2]- (Ar
) 2,6-diisopropylphenyl; R ) H, F) to good effect as ligands
for rare-earth-metal catalysts for ethylene polymerization and
hydroamination-cyclization.9 Extension to sterically demanding
guanidinates, with an R2N- group on the ligand backbone,
should allow us to access catalysts that are less strongly electron
deficient, due to the possibility of the lone pair of the R2N-
group to interact with the conjugated NCN ligand moiety.8c Only
very recently, the first examples of mono(guanidinate)dialky-
Introduction
Metal-catalyzed hydrosilylation of alkenes is the most
straightforward and atom-economic way to synthesize orga-
nosilanes. These can be converted to the corresponding alcohols
by oxidation1 or used as monomers for the production of silicon-
based polymers, applied as rubbers, paper release coatings, and
pressure-sensitive adhesives.2 Pt-based catalysts are known to
catalyze hydrosilylation with very high efficiency,3 but when
RSiH3 is employed as the silylating reagent, they tend to form
mixtures of reduced olefin R′H, RR′SiH2, RR′2SiH, and
RR′3Si.3a Disubstituted dihydrosilanes RR′SiH2 are monomers
for the production of poly(silylenes), which exhibit electronic
properties similar to those of π-conjugated polymers due to
σ-electron delocalization over the polymer backbone.4 Catalysts
based on early transition metals,5 actinides,6 and rare-earth
metals7 have been reported to show good selectivity for PhRSiH2
in the hydrosilylation of olefins with PhSiH3. Nevertheless, the
low turnover frequency of these catalysts limits their application
in synthesis. To date, the most efficient catalyst from this family
is Me2SiCp′′2SmCH(SiMe3)2 (tof ) 120 h-1 at room temper-
ature for 1-hexene), remarkably with a high selectivity for the
Markovnikov product (76%).7c [Me2Si(C5Me4)(µ-PCy)LuCH2-
(7) (a) Sakakura, Y.; Lautenschlager, H. J.; Tanaka, M. J. J. Chem. Soc.,
Chem. Commun. 1991, 40. (b) Molander, G. A.; Julius, M. J. Org. Chem.
1992, 57, 6347. (c) Yu, P. F.; Brard, L.; Li, Y.; Marks, T. J. J. Am.
Chem. Soc. 1995, 117, 7157. (d) Molander, G. A.; Retsch, W. H. J. Am.
Chem. Soc. 1997, 119, 8817. (e) Molander, G. A.; Dowdy, E. D.; Noll,
B. C. Organometallics 1997, 17, 3754. (f) Takaki, K.; Sonoda, K.; Kousaka,
T.; Koshoji, G.; Shishido, T.; Takehira, K. Tetrahedron Lett. 2001, 42, 9211.
(g) Hou, Z.; Zhang, Y.; Tardif, O.; Wakatsuki, Y. J. Am. Chem. Soc. 2001,
123, 9216. (h) Voskoboynikov, A. Z.; Shestakova, A. K.; Beletskaya, I. P.
Organometallics 2001, 20, 2794. (i) Trifonov, A. A.; Spaniol, T. P.; Okuda,
J. Organometallics 2001, 20, 4869. (j) Tardif, O.; Nishiura, M; Hou, Z.
Tetrahedron 2003, 59, 10525. (k) Horino, Y.; Livinghouse, T. Organome-
tallics 2004, 23, 12. (l) Robert, D.; Trifonov, A. A.; Voth, P.; Okuda, J. J.
Organomet. Chem. 2006, 691, 4393.
* To whom correspondence should be addressed. E-mail: B.Hessen@
rug.nl.
(1) Marciniec, B.; Gulinski, J.; Urbaniac, W.; Kornetka, Z. W. Com-
prehensiVe Handbook on Hydrosilylation; Pergamon: Oxford, U.K., 1992.
(2) Lewis, L. N.; Stein, J.; Gao, Y.; Colborn, R. E.; Hutchins, G.
Platinum Met. ReV. 1997, 21, 66.
(3) (a) Speier, J. L. AdV. Organomet. Chem. 1979, 17, 407. (b) Speier,
J. L.; Webster, J. A.; Barnes, G. H. J. Am. Chem. Soc. 1956, 79, 974. (c)
Karstedt, B. D. U.S. Patent 3,715,334, 1973. (d) Marko´, I. E.; Ste´rin, S.;
Buisine, O.; Mignani, G.; Brandlard, P.; Tinant, B.; Delcercq, J.-P. Science
2002, 298, 204. (e) Marko´, I. E.; Michaud, G.; Berthon-Gelloz, G.; Buisine,
O.; Ste´rin, S. AdV. Synth. Catal. 2004, 346, 1429. (f) Buisine, O.; Berthon-
Gelloz, G.; Brie`re, J.-F.; Ste´rin, S.; Mignani, G.; Brandlard, P.; Tinant, B.;
Delcercq, J.-P.; Marko´, I. E. Chem. Commun. 2005, 3856.
(4) West, R. ComprehensiVe Organometallic Chemistry II; Elsevier:
Amsterdam, 1995; Vol. 2, p 77.
(5) (a) Harrod, J. F.; Yun, S. S. Organometallics 1987, 6, 1381. (b)
Kesti, M. R.; Waymouth, R. M. Organometallics 1992, 11, 1095.
(6) Dash, A. K.; Gourevich, I.; Wang, J. Q.; Wang, J.; Kapon, M.; Eisen,
M. S. Organometallics 2001, 20, 5084.
(8) (a) Barker, J.; Kilner, M. Coord. Chem. ReV. 1994, 133, 219. (b)
Edelmann, F. T. Coord. Chem. ReV. 1994, 137, 403. (c) Bailey, P. J.; Pace,
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Brusova, G. P.; Lemenovskii, D. A. Russ. Chem. ReV. 2006, 75, 351–374.
(9) (a) Bambirra, S.; van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben,
J. H. Chem. Commun. 2003, 522. (b) Bambirra, S.; Bouwkamp, M. W.;
Meetsma, A.; Hessen, B. J. Am. Chem. Soc. 2004, 126, 9182. (c) Bambirra,
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10.1021/om800032g CCC: $40.75
2008 American Chemical Society
Publication on Web 05/29/2008

3132 Organometallics, Vol. 27, No. 13, 2008
Scheme 1. Synthesis of the Ligand HL and Complex 1
Ge et al.
lyttrium compounds, [(SiMe3)2NC(NR)2]Y(CH2SiMe3)2(THF)2
this delocalization can be ruled out by the R-N-C-N dihedral
angles of around 90° and the corresponding elongation of the
R2N-C bond by about 0.1 Å relative to the other C-N bonds
in the ligand.
(R ) Cy,10a i-Pr10b), were reported.
Results and Discussion
Hydrosilylation of Terminal Alkenes Catalyzed by Yt-
trium Catalysts 1 and 2. The guanidinate complex 1 and the
amidinate complex 2 both proved to be highly effective catalysts
for alkene hydrosilylation reactions using PhSiH3 in small (4%)
excess (Scheme 2). A range of terminal alkenes were tested as
substrates, and the results are summarized in Table 1. For all
the substrates (3a-i), the reaction went essentially to completion
and Lewis basic acetal or 1,3-dithiane groups pose no problems.
No side reactions (such as olefin hydrogenation, dimerization
of alkenes, and dehydrogenative coupling of organosilanes,
which are known to occur with rare-earth-metal or actinide
catalysts6,7h) were observed for catalysts 1 and 2. Full selectivity
for anti-Markovnikov products was obtained when unfunction-
alized olefins were employed as substrates (entries 1-5). For
3,3-dimethylbut-1-ene (3e), the amidinate catalyst 2 is noticeably
faster than the guanidinate catalyst 1, probably due to the greater
steric demand of the ligand in the latter (see above). For alkenes
Catalyst Synthesis and Characterization. The guanidine
ArNHC(NMe2)NAr (Ar ) 2,6-diisopropylphenyl, HL) was
described previously in the patent literature as an insecticidal
agent and was synthesized by the reaction of the carbodiimide
ArNdCdNAr with dimethylamine under forcing conditions.11
We prepared HL in 85% isolated yield by hydrolysis of the
lithium guanidinate Li[Me2NC(NAr)2], which was generated by
reaction of LiNMe2 with 1 equiv of ArNdCdNAr in THF
(Scheme 1).
Reaction of HL with 1 equiv of Y(CH2SiMe3)3(THF)2 in
toluene afforded the colorless dialkyl complex (L)Y(CH2Si-
Me3)2(THF) (1) in 78% yield after crystallization from pentane
(Scheme 1). Room-temperature NMR spectra of 1 in C6D6
suggest an (averaged) C2V symmetry in solution, indicating fast
rearrangement around the metal center on the NMR time scale.
The YCH2 resonances (C6D6, 23 °C) for 1 are found at δ -0.31
ppm (1H, d, JYH ) 2.9 Hz) and δ 37.6 ppm (13C, dt, JCH
)
98.5 Hz, JYC ) 38.9 Hz). The latter is upfield-shifted relative
to the equivalent resonance in the related amidinate complex
[PhC(NAr)2]Y(CH2SiMe3)2(THF) (2; dt, 39.5 ppm, JCH ) 100.1
Hz, JYC ) 40.3 Hz),9a suggesting that the guanidinate is the
more electron donating of the two ligands. Compound 1 contains
only a single coordinated THF molecule, while there are two
in the related guanidinate yttrium dialkyl compounds
[(SiMe3)2NC(NR)2]Y(CH2SiMe3)2(THF)2 (R ) Cy,10a i-Pr10b).
This indicates that the ligand [Me2NC(NAr)2]- (L, Ar ) 2,6-
diisopropylphenyl) is the more sterically demanding of the three.
Compound 1 was characterized by single-crystal X-ray
diffraction, and its structure is shown in Figure 1. In overall
geometry, it is similar to the related amidinate complex 2.9a
The Y-C bond distances (2.388(2) and 2.407(2) Å) in 1 are
somewhat longer than those in 2 (2.374(4) and 2.384(4) Å).
The angles C1-N1-Y ) 137.40(19)° and C16-N2-Y )
138.89(18)° in 1 are noticeably smaller than the corresponding
angles (C8-N1-Y ) 144.25(19)°, C20-N2-Y ) 143.31(19)°)
in 2, indicating that the guanidinate L is more sterically
demanding than the amidinate ligand [PhC(Ar)2]-. There
appears to be considerable interaction of the lone pair of Me2N
with the conjugated NCN moiety, as seen from the following
structural features in 1:8c (i) The three C-N distances in the
CN3 guanidinate moiety are all very similar (C13-N1 )
1.342(4) Å, C13-N2 ) 1.359(4) Å, C13-N3 ) 1.367(4) Å);
(ii) the geometry around N in the Me2N- group is essentially
planar (angle sum at N3: 359.7°); (iii) the dihedral angle formed
by the planes C14-N2-C15 and N1-C13-N3 is only 27.3(4)°.
This interaction should make the yttrium center in 1 less electron
deficient than that in 2, which is confirmed by NMR spectros-
copy (see above). In the other reported guanidinate dialkylyt-
trium compounds [(RN)2CN(SiMe3)2]Y(CH2SiMe3)2(THF)2,10
Figure 1. Molecular structure of 1. Hydrogen atoms are omitted
for clarity, and thermal ellipsoids are drawn at the 50% probability
level. Selected interatomic distances (Å) and angles (deg): Y-N1
) 2.345(2), Y-N2 ) 2.338(2), Y-O ) 2.363(2), Y-C28 )
2.388(3), Y-C32 ) 2.407(3), C13-N1 ) 1.342(4), C13-N2 )
1.359(4), C13-N3 ) 1.367(4); N1-Y-N2 ) 57.47(8), N1-Y-O
) 88.66(8), N1-Y-C28 ) 114.29(9), N1-Y-C32 ) 132.45(9),
N2-Y-C28 ) 105.84(10), N2-Y-C32 ) 103.26(9), N2-Y-O
) 145.45(8), C28-Y-C32 ) 112.8(1), C28-Y-O ) 93.57(10),
C32-Y-O ) 94.76(10), C1-N1-Y ) 137.40(19), C16-N2-Y
) 138.89(18).

Organoyttrium Catalysts
Organometallics, Vol. 27, No. 13, 2008 3133
Scheme 2
Table 1. Hydrosilylation of Alkenes by Y-Based Catalysts 1 and 2a
with a 1,3-dithiane functionality (entries 6 and 7), the guanidi-
nate catalyst 1 is clearly the most efficient. Apparently, catalyst
2 is more susceptible to inhibition by (reversible) coordination
of the heteroatom, although as yet it cannot be determined
whether this is due to steric or electronic factors. 4,4-Diethoxy-
but-1-ene (3h) is remarkably rapidly hydrosilylated but now
yields predominantly the Markovnikov product (entry 8), and
differences between 1 and 2 are visible in both activity and
selectivity. The guanidinate catalyst 1 is clearly faster but yields
a 3:1 M:AM isomer mixture, whereas 2 has a 93% selectivity
for the branched product. As the olefin in substrate 3h is not
expected to have an electronic preference for 2,1-insertion into
an Y-H species (metal hydrides are the proposed active species
in rare-earth-metal-catalyzed hydrosilylation7h,k,12), the prefer-
ence for the branched (Markovnikov) product is likely to stem
from interaction of the substrate ether groups with the metal
center. The most stable chelate (with intramolecular Y-O
coordination), resulting from insertion of the olefin into the Y-H
bond, is likely to be the five-membered chelate (from 2,1-
insertion) rather than the six-membered chelate (from 1,2-
insertion). It could also be possible that ether coordination
precedes olefin insertion, in which case the geometry for 2,1-
insertion is likely to be the most favorable. Although we did
not succeed in observing organometallic intermediates in the
reactions, it can be expected that an increased affinity of the
metal for the ether function will lead to an increased selectivity
for the branched product 5h. This would lead to the conclusion
that the metal center in the guanidinate catalyst 1 is less
electrophilic than that in the amidinate catalyst 2, which is
consistent with the structural and spectroscopic observations
made above. Styrene requires a higher temperature (80 °C) to
give conversion and then yields the benzylic silane 5g as the
main product (entry 9). That styrene hydrosilylation is more
sluggish may be due to η3 coordination of the 1-phenylethyl
group formed by 2,1-insertion of styrene into a Y-H species.
An yttrium η3-1-phenylethyl complex was reported from the
reaction of styrene with [Y(η5:η1-C5Me4SiMe2NtBu)(THF)-
(µ-H)]2.13 Internal olefins (e.g., cis-4-octene and cyclohexene)
are not converted under the applied conditions.
a Reaction conditions: catalyst 1 or 2 (10 µmol), olefin (0.5 mmol),
PhSiH3 (0.52 mmol), 23 °C, solvent C6D6 (0.3 mL). b Determined by
1
GC-MS and in situ H NMR spectroscopy. c 80°C.
Table 2. Crystal Data and Data Collection Parameters of Complex 1
compd
1
formula
fw
C39H70N3OSi2Y
743.08
cryst color
cryst size (mm)
cryst syst
space group
a (Å)
colorless
0.56 × 0.46 × 0.42
orthorhombic
P212121
12.9822(8)
b (Å)
17.6370(11)
c (Å)
18.8875(12)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
90
90
90
4324.6(5)
Z
4
F
calcd, g cm-3
1.140
14.34
1600
2.67-26.37
(16, -20 to +22, -23 to +22
34 204
8832
Conclusions
µ, cm-1
F(000), electrons
θ range (deg)
index ranges(h,k,l)
no. of rflns collected
no. of unique rflns
no. of reflns with Fo g 4σ(Fo)
Rw(F2)
a, b
R (F)
T (K)
GOF
Yttrium catalysts with sterically demanding amidinate or
guanidinate ancillary ligands thus appear to be excellent catalysts
for the hydrosilylation of terminal alkenes with phenylsilane.
7374
(10) (a) Trifonov, A. A.; Lyubov, D. M.; Fukin, G. K.; Baranov, E. V.;
Kurskii, Y. A. Organometallics 2006, 25, 3935. (b) Lyubov, D. M.; Fukin,
G. K.; Trifonov, A. A. Inorg. Chem. 2007, 46, 11450.
(11) Neumann, W.; Bayer, O.; Unterstenhoefer, G.; Grewe, F. Ger.
Offen. DE 1192453, 1965.
0.0906
0.0468, 0.8703
0.0399
100(1)
1.023
(12) Evidence that hydride species of the type “(L)YH2” are the active
species in the present system was obtained from the reaction of
(L)Y(CH2SiMe3)2(THF) (1) with 2 equiv of PhSiH3. Although this did not
produce a stable, well-defined Y-hydride complex, the formation of 2 equiv
of PhSiH2CH2SiMe3 was observed, a clear indication of smooth Y-H
formation.
Significantly higher turnover frequencies (>600 h-1, 23 °C)
are achieved than with other rare-earth-metal or early-transition-
metal catalysts, and heteroatom-containing substrates can also
be converted with high efficiency. The performance of this
catalyst family with functionalized substrates may be tuned by
(13) Hultzsch, K. C.; Voth, P.; Beckerle, K.; Spaniol, T. P.; Okuda, J.
Organometallics 2000, 19, 228.

3134 Organometallics, Vol. 27, No. 13, 2008
Ge et al.
1H NMR (400 MHz, C6D6, δ): 7.08 (m, 6H, m-H, p-H Ph), 3.61
(sept, 4H, JHH ) 6.67 Hz, CH iPr), 3.56 (m, 4H, R-H THF), 2.01
(s, 6H, NCH3), 1.40 (d, 12H, JHH ) 6.97 Hz, CH3 iPr), 1.23 (d,
12H, JHH ) 6.97 Hz, CH3 iPr), 1.12 (m, 4H, ꢀ-H THF), 0.26 (s,
18H, Si(CH3)3), -0.31 (d, 4H, JHH ) 2.9 Hz, YCH2). 13C NMR
(100.6 MHz, C6D6, δ): 166.7 (s, NCN), 144.0 (s, ipso-C Ph), 142.4
modifying the electrophilicity of the catalyst (viz. amidinate vs
guanidinate).
Experimental Section
General Remarks. All reactions and manipulations of air- and
moisture-sensitive compounds were performed under a nitrogen
atmosphere using standard Schlenk, vacuum line, and glovebox
techniques, unless mentioned otherwise. Toluene and pentane
(Aldrich, anhydrous, 99.8%) were passed over columns of Al2O3
(Fluka), BASF R3-11-supported Cu oxygen scavenger, and mo-
lecular sieves (Aldrich, 4 Å). THF (Aldrich, anhydrous, 99.8%)
was dried over Al2O3 (Fluka). All solvents were degassed prior to
use and stored under nitrogen. C6D6 was vacuum-transferred from
Na/K alloy. NMR spectra were recorded on Varian Gemini VXR
300, Varian Gemini VXR 400, and Varian Inova 500 spectrometers
in NMR tubes equipped with a Teflon (Young) valve. The 1H NMR
spectra were referenced to resonances of residual protons in
deuterated solvents. The 13C NMR spectra were referenced to
carbon resonances of deuterated solvents and reported in ppm
relative to TMS (δ 0 ppm). GC-MS measurements were performed
on an HP 6890 series GC system coupled with an HP 5973 mass-
selective detector. Column: HP-5MS 5% phenyl methyl siloxane
30 m × 250 µm capillary column. Temperature profile: start at
35 °C (hold for 10 min), increase to 280 °C at a rate of 20 °C/min,
and then hold at 280 °C for 10 min. The olefins 1-hexene, 1-octene,
vinylcyclohexane, 4-vinyl-1-cyclohexene, and 3,3-dimethyl-1-
butene were commercial samples stirred for at least 4 h over Na/K
alloy and then distilled under nitrogen. Styrene was dried over
molecular sieves and distilled before use. Phenylsilane (Aldrich,
99%) was saturated with nitrogen and used as purchased. Bis(2,6-
diisopropylphenyl)carbodiimide (TCI Europe Organic Chemicals,
>98%) was used as purchased. 2-(3′-Butenyl)-2-methyl-1,3-
dithiane,14 2-(4′-pentenyl)-2-methyl-1,3-dithiane,14 and 4,4-di-
ethoxylbut-1-ene15 were prepared according to literature procedures.
Ligand (HL) Synthesis. To a solution of bis(2,6-diisopropy-
lphenyl)carbodiimide (3.62 g, 10 mmol) in THF (20 mL) was added
a solution of lithium dimethylamide (0.53 g, 10.4 mmol) in THF
(10 mL). The resulting solution was stirred for 2 h at room
temperature. Then water (0.20 g, 11 mmol) was added, and the
mixture was stirred for another 10 min. Diethyl ether (100 mL)
was added, and the mixture was dried over Na2SO4 and filtered.
The volatiles were removed under reduced pressure to yield the
title compound (3.47 g, 8.5 mmol, 85%) as an off-white solid, which
can be used without further purification. 1H NMR (300 MHz, C6D6,
δ): 7.26 (d, 2H, JHH ) 7.41 Hz, m-H Ph), 7.09 (m, 2H, p-H Ph),
7.00 (d, 2H, JHH ) 7.41 Hz, m-H Ph), 5.25 (s, 1H, NdCNH), 3.45
(sept, 2H, JHH ) 6.87 Hz, CH(CH3)2), 3.27 (sept, 2H, JHH ) 6.87
Hz, CH(CH3)2), 2.47 (s, 6H, N(CH3)2), 1.39 (d, 6H, JHH ) 6.49
Hz, CH(CH3)2), 1.37 (d, 6H, JHH ) 6.49 Hz, CH(CH3)2), 1.17 (br,
6H, CH(CH3)2), 0.97 (br, 6H, CH(CH3)2). 13C{1H} NMR (75.6
MHz, C6D6, δ): 152.2 (NCN), 151.3 (NCN), 144.9 (ipso-C Ph),
140.3 (o-C Ph), 127.0 (p-C Ph), 124.1 (m-C Ph), 123.5 (m-C Ph),
123.3 (p-C Ph), 39.4 (NCH3), 28.9 (CH iPr), 28.7 (CH iPr), 24.6
(CH3 iPr), 22.5 (CH3 iPr). Anal. Calcd for C27H41N3: C, 79.55; H,
10.14; N, 10.31. Found: C, 79.50; H, 10.19; N, 10.15.
(s, o-C Ph), 124.0 (d, JCH ) 156.3 Hz, m-C Ph), 123.9 (d, JCH
)
159.1 Hz, p-C Ph), 70.5 (t, JCH ) 150.2 Hz, R-C THF), 39.6 (q,
JCH ) 138.1 Hz, NCH3), 37.6 (dt, JYC ) 38.9 Hz, JCH ) 98.5,
YCH2), 28.1 (d, JCH ) 127.7 Hz, CH iPr), 25.9 (q, JCH ) 123.8
Hz, CH3 iPr), 24.9 (t, JCH ) 133.6 Hz, ꢀ-C THF), 23.8 (q, JCH
)
125.6 Hz, CH3 iPr), 4.4 (q, JCH ) 115.6 Hz, Si(CH3)3). Anal. Calcd
for C39H70N3OSi2Y: C, 63.12; H, 9.51; N, 5.66. Found: C, 62.95;
H, 9.56; N, 5.55.
General Procedure for Catalytic Hydrosilylation of Alkenes.
An NMR tube equipped with a Teflon Young valve was charged
in a glovebox with (L)Y(CH2SiMe3)2(THF) (1) or [PhC(NC6H3i-
Pr-2,6)2]Y(CH2SiMe3)2(THF) (2) (10 µmol), PhSiH3 (0.52 mmol),
olefin (0.5 mmol), and C6D6 (0.3 mL). The tube was closed and
taken out of the glovebox. The dispearance of the substrates and
formation of new organosilanes can be conveniently monitored by
NMR. The products were characterized by 1H (and for new
compounds 13C) NMR spectrometry and GC-MS.
Characterization of New Silanes. 2-(5′-Phenylsilylpentyl)-2-
methyl-1,3-dithiane (4f). 1H NMR (400 MHz, C6D6, δ): 7.49 (m,
2H), 7.19 (m, 3H), 4.45 (t, 2H, JHH ) 3.59 Hz, SiH2), 2.47 (m,
4H), 1.84 (m, 2H), 1.58 (m, 2H), 1.54 (s, 3H), 1.47 (m, 2H), 1.37
(m, 2H), 1.24 (m, 2H), 0.81 (m, 2H). 13C{1H} NMR (100.6 MHz,
C6D6, δ): 135.5 (m-C Ph), 132.7 (ipso-C Ph), 129.8 (p-C Ph), 128.3
(o-C Ph), 49.4 (S2CCH3), 42.0 (SCH2), 33.3, 28.1, 26.5, 25.6, 25.3,
24.5, 10.3 (SiH2CH2). GC-MS: m/z 310 (M+).
2-(3′-Phenylsilylpropyl)-2-methyl-1,3-dithiane (4g). 1H NMR
(400 MHz, C6D6, δ): 7.49 (m, 2H), 7.17 (m, 3H), 4.45 (t, 2H, JHH
) 3.70 Hz, SiH2), 2.42 (m, 4H), 1.93 (m, 2H), 1.69 (m, 2H), 1.54
(m, 2H), 1.48 (s, 3H), 0.80 (m, 2H). 13C{1H} NMR (100.6 MHz,
C6D6, δ): 135.5 (m-C Ph), 132.5 (ipso-C Ph), 129.9 (p-C Ph), 128.3
(o-C Ph), 49.3 (S2CCH3), 45.1 (SCH2), 28.0, 26.5, 25.5, 20.6, 10.4
(SiH2CH2). GC-MS: m/z 282 (M+). Retention time: 21.6 min.
2-(2′-Phenylsilylpropyl)-2-methyl-1,3-dithiane (5g). 1H NMR
(400 MHz, C6D6, δ): 4.41 (m, PhSiH2), 1.49 (s, S2CCH3), 1.15 (d,
JHH ) 7.35 Hz, SiH2CHCH3), other resonances are overlapped with
4g. GC-MS: m/z 282 (M+). Retention time: 21.3 min.
1,1-Diethoxyl-3-(phenylsilyl)butane (4h). 1H NMR (500 MHz,
C6D6, δ): 7.53 (m, 2H), 7.14 (m, 3H), 4.57 (t, 1H, JHH ) 5.89 Hz,
(C2H5O)2CH), 4.42 (m, 2H, SiH2), 3.49 (m, 2H), 3.32 (m, 2H),
1.90 (m, 1H), 1.69 (m, 1H), 1.36 (m, 1H), 1.10 (t, 6H, JHH ) 7.13
Hz, CH3), 1.06 (d, 3H, JHH ) 7.15 Hz, CH3). 13C NMR (125.7
MHz, C6D6, δ): 136.0 (d, JCH ) 158.6 Hz, m-C Ph), 132.3 (s, ipso-C
Ph), 129.8 (d, JCH ) 159.8 Hz, p-C Ph), 128.2 (d, JCH ) 157.8 Hz,
o-C Ph), 101.8 (d, JCH ) 158.1 Hz, O2CH), 60.9 (t, JCH ) 140.1
Hz, OCH2CH3), 60.5 (t, JCH ) 140.1 Hz, OCH2CH3), 37.5 (t, JCH
) 125.0 Hz, O2CHCH2), 16.6 (q, JCH ) 124.0 Hz, PhSiH2CHCH3),
15.6 (q, JCH ) 124.2 Hz, OCH2CH3), 12.7 (d, JCH ) 112.0 Hz,
PhSiH2CH). GC-MS: m/z 252 (M+). Retention time: 18.7 min.
1,1-Diethoxyl-4-(phenylsilyl)butane (5h). 1H NMR (500 MHz,
C6D6, δ): 7.47 (m, 2H), 7.13 (m, 3H), 4.38 (t, 1H, JHH ) 5.61 Hz,
(C2H5O)2CH), 4.45 (t, 2H, JHH ) 3.28 Hz, SiH2), 3.49 (m, 2H),
3.31 (m, 2H), 1.90 (m, 1H), 1.67 (m, 2H), 1.54 (m, 2H), 1.10 (t,
6H, JHH ) 7.13 Hz, CH3), 0.79 (m, 2H, CH2SiH2). 13C NMR (125.7
MHz, C6D6, δ): 135.5 (d, JCH ) 156.2 Hz, m-C Ph), 132.6 (s, ipso-C
Ph), 129.8 (d, JCH ) 159.8 Hz, p-C Ph), 128.3 (d, JCH ) 158.3 Hz,
o-C Ph), 102.6 (d, JCH ) 156.7 Hz, O2CH), 60.7 (t, JCH ) 140.1
Hz, OCH2CH3), 36.9 (t, JCH ) 125.0 Hz, O2CHCH2), 20.8 (t, JCH
) 122.1 Hz, SiH2CH2CH2), 15.6 (q, JCH ) 124.2 Hz, OCH2CH3),
10.2 (t, JCH ) 118.0 Hz, PhSiH2CH2). GC-MS: m/z 252 (M+).
Retention time: 18.3 min.
Synthesis of (L)Y(CH2SiMe3)2(THF) (1). To a solution of
Y(CH2SiMe3)3(THF)2 (268 mg, 0.541 mmol) in toluene (20 mL)
was added a solution of HL (221 mg, 0.541 mmol) in toluene (5
mL). The resulting solution was stirred for 20 min at room
temperature. Then volatiles were removed under reduced pressure
and the residue was dissolved in pentane (4 mL). Cooling to
-30 °C overnight afforded well-formed crystals. The mother liquor
was decanted and the solid was dried under vacuum, yielding the
title compound (316 mg, 0.415 mmol, 78%) as an off-white solid.
(14) Seebach, D.; Corey, E. J. J. Org. Chem. 1975, 40, 231.
(15) Cloux, R.; Schlosser, M. HelV. Chim. Acta 1984, 67, 1470.

Organoyttrium Catalysts
Organometallics, Vol. 27, No. 13, 2008 3135
Structure Determination of Compound 1. Suitable crystals
were obtained by crystallization from pentane. A crystal was
mounted on a glass fiber inside a drybox and transferred under an
inert atmosphere to the cold nitrogen stream of a Bruker SMART
APEX CCD diffractometer. Intensity data were collected with Mo
KR radiation (λ ) 0.710 73 Å). Intensity data were corrected for
Lorentz and polarization effects. A semiempirical absorption
correction was applied, based on the intensities of symmetry-related
reflections measured at different angular settings (SADABS16). The
structures were solved by Patterson methods, and extension of the
models was accomplished by direct methods applied to difference
structure factors, using the program DIRDIF.17 In a subsequent
difference Fourier synthesis all hydrogen atoms were located, the
positional and isotropic displacement parameters of which were
refined. All refinements and geometry calculations were performed
with the program packages SHELXL18 and PLATON.19 Crystal-
lographic data and the details of data collections and data refine-
ments are given in Table 2.
Acknowledgment. This investigation was financially sup-
ported by the Chemical Sciences Division of The Netherlands
Organization for Scientific Research (NWO-CW).
Supporting Information Available: Text giving additional
characterization data for the organosilanes and a CIF file giving
X-ray data for 1. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM800032G
(16) Sheldrick, G. M. SADABS Version 2, Empirical Absorption
Correction Program; University of Go¨ttingen, Go¨ttingen, Germany, 2000.
(17) Beurskens, P. T.; Beurskens, G.; De Gelder, R.; Garcia-Granda,
S.; Gould, R. O.; Israel, R.; Smits, J. M. M. The DIRDIF-99 Program
System; Crystallography Laboratory, University of Nijmegen, Nijmegen,
The Netherlands, 1999.
(18) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(19) Spek, A. L. PLATON, Program for the Automated Analysis of
Molecular Geometry, April 2000 Version; University of Utrecht, Utrecht,
The Netherlands.