Hydrosilylation of dienes by yttrium hydrido complexes containing a linked amido-cyclopentadienyl ligand

Article abstract of DOI:10.1039/b406071g

The dimeric hydrido complex [Y(L)(THF)((μ-H)]₂ (2) containing the CH₂SiMe₂-linked amido-cyclopentadienyl ligand L = C₅Me₄CH₂SiMe₂NCMe₃ ^2- catalyzed the hydr

Full text of DOI:10.1039/b406071g

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F U L L P A P E R
Hydrosilylation of dienes by yttrium hydrido complexes
containing a linked amido-cyclopentadienyl ligand
Alexander A. Trifonov,† Thomas P. Spaniol and Jun Okuda*
Institute of Inorganic Chemistry, Aachen University of Technology (RWTH),
Prof.-Pirlet-Strasse 1, D-52056, Aachen, Germany. E-mail: jun.okuda@ac.rwth-aachen.de;
Fax: +49-241-8092644
Received 22nd April 2004, Accepted 9th June 2004
First published as an Advance Article on the web 28th June 2004
The dimeric hydrido complex [Y(L)(THF)(-H)]2 (2) containing the CH2SiMe2-linked amido-cyclopentadienyl ligand
L = C5Me4CH2SiMe2NCMe32− catalyzed the hydrosilylation of 1,5-hexadiene, 1,7-octadiene and vinylcyclohexene by
PhSiH3. As demonstrated for 1,7-octadiene, the product distribution of the hydrosilylation strongly depends on the molar
ratio of the reagents. In the absence of PhSiH3, the stoichiometric reaction of 2 with 1,5-hexadiene gave the isolable
crystalline cyclopentylmethyl complex [Y(L){CH2CH(CH2)4}(THF)] (3). Internal olefins such as trans-stilbene and
alkynes such as tert-butylacetylene were not hydrosilylated by 2. trans-Stilbene was inserted into the yttrium–hydride
bond of 2 to give the 1,2-diphenylethyl complex [Y(L){CH(CH2Ph)Ph}(THF)] (4). tert-Butylacetylene reacted with 2
to give the dimeric acetylide [Y(L)(CCCMe3)]2 (5). In an attempt to detect the monomeric hydrido species as a DME
adduct [Y(L)H(DME)], complex 2 was reacted with DME to form the sparingly soluble, dimeric 2-methoxyethoxy
complex [Y(L)(-OCH2CH2OMe-O)]2 (6) under C–O splitting.
Introduction
In contrast to the metallocene alkyl and hydrido complexes of
the rare-earth metals [Ln(5-C5R5)2X] (X = alkyl, H)1 analogous
complexes supported by the linked amido-cyclopentadienyl ligand
system [Ln(5:1-C5Me4ZNR)X]2 have been used only to a limited
degree as catalyst precursors for homogeneous alkene and alkyne
hydrometalation reactions.2d–f,3 We have recently reported that the
hydrido yttrium complexes [Y(5:1-C5Me4ZNCMe3)(THF)(-H)]2
(Z = SiMe2, CH2SiMe2) catalyze the hydrosilylation of 1-decene and
styrene by PhSiH3,3a previously reported for metallocene-based cat-
alysts.4 Extending the ancillary ligand backbone Z from the SiMe2
link to the longer CH2SiMe2 significantly increased the reactivity,5
although the ligand appears to be less “geometrically constrained”.6
We report here on the hydrosilylation of various dienes by PhSiH3
catalyzed by the alkyl complex [Y(L)(CH2SiMe3)(THF)] (1) with
L = (C5Me4CH2SiMe2NCMe3)2−, which, in the presence of PhSiH3,
forms the dimeric hydrido complex [Y(L)(THF)(-H)]2 (2) in situ.
In addition, we have studied the reactivity of the hydrido complex
2 towards various unsaturated substrates in order to compare the
reactivity with that of the [Y(5:1-C5Me4SiMe2NCMe3)(THF)(-
H)]27 and to gain insight into the catalytically active species of the
hydrosilylation reaction.
Scheme 1
what unexpected, since other catalysts such as metallocenes appear
to give selectively 1-phenylsilylmethylcyclopentane.3a,4
Without PhSiH3, however, the reaction of
2 with 1,5-
hexadiene at °C gives the cyclopentylmethyl complex
0
[Y(L){CH2CH(CH2)4}(THF)] (3) as a result of intramolecular
cyclization, as previously reported for the analogous reaction of
[Y(5:1-C5Me4SiMe2NCMe3)(THF)(-H)]2 to give [Y(5:1-
C5Me4SiMe2NCMe3){CH2CH(CH2)4}(THF)].7 Complex 3 was
isolated as extremely air- and moisture-sensitive colorless crystals
in 74% yield after crystallization from hexane at −30 °C. It is highly
soluble in aliphatic and aromatic hydrocarbons and gradually de-
composed in solution even under an atmosphere of argon at 0 °C
over a period of one day.
The 1H NMR spectrum of 3 at room temperature shows a doublet
of doublets at −0.11 ppm with characteristic coupling constants
(2JYH = 3.3 Hz, 3JHH = 8.0 Hz) due to the two protons of the methy-
lene group attached to the yttrium center. In the 13C{1H} NMR
spectrum a resonance at 47.9 ppm with a large coupling constant
1JYC = 52.5 Hz is observed for the corresponding carbon atom
(1JYC = 54.7 Hz for [Y(5:1-C5Me4SiMe2NCMe3){CH2CH(CH2)4}
(THF)]7). Variable-temperature 1H and 13C NMR spectroscopic data
for 3 indicate the presence of a labile THF ligand over the tempera-
ture range of +25 to −70 °C, resulting in an apparent mirror plane
within the molecule. No decoalescence of any of the diastereotopic
signals was observed even at −70 °C.
Results and discussion
Reaction of the hydrido complex 2 with dienes
The hydrido complex 2 catalyzed the hydrosilylation of 1,5-hexa-
diene with PhSiH3 (1:1 molar ratio) under standard conditions
(25 °C, 5 mol% 2 in hexane) to give an inseparable mixture of both
linear (6-phenylsilyl-1-hexene, 1,6-bis(phenylsilyl)hexane) and
cyclized products (1-phenylsilylmethylcyclopentane, 1-phenylsila-
cycloheptane) as well as involatile oligomer (Scheme 1). When the
reaction of 2 with equimolar amounts of 1,5-hexadiene and PhSiH3
in benzene-d6 was monitored by NMR spectroscopy, the characteris-
tic triplet at 5.50 ppm (JYH = 26.8 Hz) was recorded upon addition of
PhSiH3, indicating regeneration of the dimeric hydride. At the same
time, the multiplet due to the methylene protons of the PhSiH2CH2
group appeared at 1.16 ppm. The low chemoselectivity was some-
† Current address: G.A. Razuvaev Institute of Organometallic Chemistry of
RussianAcademy of Sciences, Tropinina str. 49, 603950, Nizhny Novgorod,
Russia.
T h i s j o u r n a l i s
©
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4
D a l t o n T r a n s . , 2 0 0 4 , 2 2 4 5 – 2 2 5 0
2 2 4 5

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Table 1 Crystallographic and refinement parameters for complexes 3, 4 and 6
Compound
3
4
6
Crystal data
Empirical formula
C26H48NOSiY
507.65
C34H50NOSiY
605.77
C38H72N2O4Si2Y2·0.5C4H8O
891.04
M/g mol−1
Crystal system
Space group
Crystal size/mm
a/Å
b/Å
c/Å
/°
/°
Monoclinic
P21/n (no. 14)
0.45 × 0.30 × 0.08
10.5235(7)
17.119(1)
16.244(1)
90
104.359(1)
90
2835.0(3)
4
Triclinic
P1 (no. 2)
0.50 × 0.45 × 0.13
9.2905(5)
18.017(1)
20.250(1)
86.247(6)
84.471(5)
79.076(6)
3308.8(3)
4
Triclinic
P1 (no. 2)
0.18 × 0.14 × 0.12
10.5434(7)
14.0024(9)
16.678(1)
69.103(1)
80.809(1)
79.444(1)
2249.4(2)
2
/°
V/Å3
Z
Dc/g cm−3
F(000)
/mm−1
T/K
1.189
1088
2.115
181(2)
1.216
1288
1.824
293(2)
1.316
944
2.660
183(2)
Data collection
2max/°
Index ranges
56.6
51.9
56.6
h, −14 to 14
k, −22 to 22
l, −21 to 21
h, 0 to 11
k, −21 to 22
l, −24 to 24
h, −14 to 14
k, −18 to 18
l, −22 to 22
Solution and refinement
No. of rflns. measd
No. of indep. rflns. (Rint)
No. of parameters
25422
7000 (0.0584)
278
13779
12943 (0.0608)
715
20801
10853 (0.0548)
473
GOF
0.911
0.976
0.872
Final R indices R1, wR2 (obsd. data)
Final R indices R1, wR2 (all data)
/e Å−3
0.0423/0.0948
0.0959/0.1071
0.593/−0.428
0.0613/0.0966
0.1911/0.1228
0.320/−0.476
0.0418/0.0729
0.0944/0.0833
0.624/−0.445
The molecular structure of 3 in the solid state was determined by
a crystal structure analysis on colorless crystals obtained by slow
cooling of a hexane solution to −30 °C. Crystallographic data are
compiled in Table 1. Fig. 1 shows the molecular structure that is
derived from a three-legged piano-stool configuration. The yttrium
atom is coordinated in pseudo-tetrahedral fashion by the cyclo-
pentadienyl ring, the chelating amido and cyclopentylmethyl li-
gands, as well as one THF molecule. Molecular parameters of 3 are
comparable with those of [Y(L){CH2SiMe3}(THF)].4 The Y–C17
bond distance of 2.423(3) Å is similar to the distance reported for
the related trimethylsilylmethyl derivative (2.425(2) Å), but slightly
longer than that in the complex [Y(5:1-C5Me4SiMe2NCMe3)-
(CH2SiMe3)(THF)] (2.388(7) Å).7b As expected, the length of the
terminal Y–C bond in 3 is much shorter than the distances between
yttrium and -carbon atoms in dimeric complexes with bridging
n-alkyl ligands of the type [Y(5:1-C5Me4SiMe2NCMe3)(-
CH2CH2R)]2.7d The slightly longer Y–O contact in 3 (2.344(2) Å)
comparedtothecorrespondingdistancein[Y(L){CH2SiMe3}(THF)]
(2.327(1) Å)3a may result from higher steric hindrance caused by the
cyclopentylmethyl ligand. Compound 3 has a monomeric structure
both in solution and in the crystalline state, probably due to an in-
creased steric demand of the tertiary -carbon atom compared with
the secondary -carbon atom.
The catalytic reaction of 1,7-octadiene with PhSiH3 in the
presence of 5 mol% of 2 did not give any cyclic organosilanes. We
found that the hydrosilylation reaction was strongly influenced by
the stoichiometric ratio of the diene to the silane PhSiH3 as well as
by the reaction time (Scheme 2).
When the reaction was carried out in the presence of a twofold
molar excess of PhSiH3, 1,7-octadiene was quantitatively converted
within 48 h to the product of the double primary (anti-Markovnikov)
addition, 1,8-bis(phenylsilyl)octane. The equimolar reaction of 1,7-
octadiene with PhSiH3 is less selective and resulted in the complete
conversion of the starting material within 2 h to a 70:27-mixture
of 8-phenylsilyl-1-octene and 1,8-bis(phenylsilyl)octane. When an
equimolar reaction mixture of PhSiH3 and 1,7-octadiene was left
standing at room temperature for 72 h, a highly viscous pale-yellow
oil was isolated in high yield instead of the volatile organosilanes.
Fig. 1 ORTEP
diagram
of
the
molecular
structure
of
[Y(L){CH2CH(CH2)4}(THF)] (3). Thermal ellipsoids are drawn at the 30%
probability level. Hydrogen atoms as well as C18b and C20b (which are split
positions due to disorder within this ligand) are omitted for the sake of clar-
ity. Selected bond lengths (Å) and bond angles (°): Y–N 2.235(2), Y–C17
2.423(3), Y–C1 2.598(3), Y–C2 2.608(3), Y–C3 2.656(3), Y–C4 2.649(3),
Y–C5 2.610(3), Y–O 2.344(2), CpCent–Y 2.335(3); CpCent–Y–N 106.1(1),
CpCent–Y–C17 113.4(1), CpCent–Y–O 110.1(1), N–Y–C17 118.0(1), N–Y–O
111.58(8), O–Y–C17 97.5(1).
After removal of all volatiles in vacuo, the oil was purified by flash
chromatography. The microanalytical data and the 1H and 13C NMR
spectra indicate that it is an oligomer consisting of [PhSiH(CH2)8]n
fragments. The degree of oligomerization was estimated to be
n ~ 20, based on one sharp peak corresponding to Mw = 4500 in the
gel permeation chromatogram.Apparently, the PhSiH2 group of ini-
2 2 4 6
D a l t o n T r a n s . , 2 0 0 4 , 2 2 4 5 – 2 2 5 0

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(2.342(5) Å for both crystallographically independent molecules)
are comparable to those observed in the complex mentioned above,
theY–O bond (Y1–O1 2.370(4) Å, Y2–O2 2.357(4) Å) is somewhat
longer (2.350(8) Å for [Y(L){CHMePh}(THF)]). The Y–C bond
in 4 (Y1–C17 2.519(5) Å, Y2–C51 2.478(5) Å) is similar to that in
[Y(L){CHMePh}(THF)] (2.52(1) Å).3a Aweak interaction between
the yttrium atom and the ipso ring carbon atom of the -phenyl
group is indicated by the interatomic distance of 2.985(5) Å (Y1–
C18) as well as of 3.064(5) Å (Y2–C52). Interaction between the yt-
trium atom and the aromatic ring is also indicated by the small angle
of 93.7(3)° (Y1–C17–C18) as well as of 99.1(4)° (Y2–C51–C52)
which is significantly smaller than that found for the 1-bonded
benzyl ligand in the complex [Cp*2Y(CH2Ph)(THF)] (Y–Cipso
3.444 Å, Y–C–Cipso 118.3(4)°).9 The bond distance between the
ipso-carbon atom and the two ortho-carbon atoms of the ring atoms
are slightly longer than the other bond lengths within the aromatic
ring (C18–C23 1.402(7) Å and C18–C19 1.410(7) Å as well as
C52–C57 1.397(8) Å and C52–C53 1.408(8) Å).
Scheme 2
tially formed 8-phenylsilyl-1-octene reacted with the double bond
of another 8-phenylsilyl-1-octene molecule under oligomerization.
1H NMR spectroscopic monitoring of the reaction of the
hydrido complex 2 with 1,7-octadiene at 0 °C indicated that the
conversion was complete within 45 min to give the derivative with
a cycloheptylmethyl ligand [Y(L){CH2CH(CH2)6}(THF)]. The
product is highly unstable in solution even at low temperatures
and decomposed readily. All attempts to isolate the complex in
analytically pure form failed.
Selective hydrosilylation of the vinylic double bond of 4-vinyl-1-
cyclohexene was achieved in the presence of 2 using two equivalents
of PhSiH3. The reaction led to the primary (anti-Markovnikov)
product 4-{2-(phenylsilyl)ethyl}cyclohex-1-ene4a in 93% yield
after 18 h. The reaction of 2 with 4-vinyl-1-cyclohexene in toluene
at 0 °C gave the insertion product which readily decomposed and
could not be isolated.
Reactions of the hydrido complex 2 with trans-stilbene
In contrast to well known reactions of rare-earth metal hydrides
with -olefins,1,8 the insertion of 1,2-disubstituted olefins into
Ln–H bonds is less investigated. 2 did not catalyze the hydro-
silylations of trans-stilbene. The yttrium hydrido complex [Y(5:
1-C5Me4SiMe2CMe3)(THF)(-H)]2 is inert against trans-stilbene
even at 60–80 °C over several hours.7b However, the yttrium hydride
2 slowly reacted with an equimolar amount of trans-stilbene in ben-
zene at room temperature over a period of 6 d (Scheme 3).
Fig. 2 ORTEP
diagram
of
the
molecular
structure
of
[Y(L){CH(CH2Ph)Ph}(THF)] (4). Thermal ellipsoids are drawn at the 30%
probability level. Only one of the two crystallographically independent mol-
ecules is shown. Hydrogen atoms are omitted for the sake of clarity. Selected
bond lengths (Å) and bond angles (°): Y1–N1 2.232(4), Y1–C17 2.519(5),
Y1–C1 2.587(5), Y1–C2 2.606(5), Y1–C3 2.662(5), Y1–C4 2.680(5), Y1–
C5 2.618(5), Y1–O1 2.370(4); N1–Y1–O1 97.5(2), N1–Y1–C17 114.3(2),
O1–Y1–C17 119.6(2), Y1–C17–C18 93.7(3), Y1–C17–C24 125.5(4).
The 1H NMR spectra at different temperatures indicate that the
coordinated THF ligands in 4 are labile on the NMR time scale. 1H
and 13C NMR spectroscopic data of 4 at room temperature show
four distinct singlets for the cyclopentadienyl methyl groups as
well as two singlets for the SiMe2 group, as expected for a chiral
molecule. The diastereotopic protons of the methylene group of the
CH2SiMe2 link give rise to two signals at 2.14 and 2.22 ppm in the
1H NMR spectrum. In the 13C NMR spectrum, the -carbon atom
of the CH(CH2Ph)Ph moiety bonded to the yttrium appears as a
doublet at 58.0 ppm with 1JYC = 25.0 Hz. The proton bonded to this
carbon atom is observed as a broadened multiplet at 2.75 ppm, while
the protons of the methylene group appear as doublets of doublets at
3.45 and 3.70 ppm, as part of a higher-order ABX pattern.
Scheme 3
The insertion product [Y(L){CH(CH2Ph)Ph}(THF)] (4) was
isolated as air- and moisture-sensitive crystals in 72% yield after
crystallization from hexane at −30 °C. It is soluble in aliphatic and
aromatic hydrocarbons. The crystal structure was determined by
X-ray diffraction. The unit cell contains two crystallographically in-
dependent molecules of similar structure.An ORTEPdiagram of the
structure of one molecule is shown in Fig. 2. The monomeric com-
plex contains a chiral yttrium center adopting a pseudo-tetrahedral
geometry similar to that found in 3, [Y(L){CH2SiMe3}(THF)],
and [Y(L){CHMePh}(THF)].3a Although the Y–N bond length
(Y1–N1 2.232(4) Å, Y2–N2 2.235(4) Å) and the Y–CpCent distance
Reactions of the hydrido complex 2 with tert-butylacetylene
The lanthanide alkyls and hydrides are known to react with termi-
nal alkynes to produce oligomeric acetylides which normally rear-
range in solution to give carbon–carbon coupled products.10 Since
hydrosilylation of alkynes by PhSiH3 was not observed using 2, it
D a l t o n T r a n s . , 2 0 0 4 , 2 2 4 5 – 2 2 5 0
2 2 4 7

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was assumed that a stoichiometric metalation reaction took place.
Complex 2 readily reacted with tert-butylacetylene in benzene at
room temperature under evolution of dihydrogen over a period of
30 min. The acetylide [Y(L)(CCCMe3)]2 (5) was isolated in 92%
yield after crystallization from hexane (Scheme 3).
Both molecules show crystallographic inversion symmetry. The yt-
trium atoms are coordinated by the linked amido-cyclopentadienyl
ligands and are assembled by two 2-methoxyethoxy fragments
forming an Y2O4 core with 2-bridging alkoxy oxygen atoms,
while the ether oxygen atoms are bonded to each yttrium center.
The bridging Y–O bonds are inequivalent with bond distances
between 2.329(2) Å (Y1–O1) and 2.251(2) Å (Y1–O1′) as well as
2.339(2) Å (Y2–O3) and 2.242(2) Å (Y2–O3′) for the second crys-
tallographically independent molecule. The Y–O distances in 6 are
close to the bridging bonds in the dimeric enolate complex [Y(5-
MeC5H4)2(-OCHCH2)]2.12 The coordinative bond between the
methoxy oxygen atom and the yttrium center (Y1–O2 2.424(2) Å,
Y2–O4 2.426(2) Å) is slightly shorter than the Y–O bond in [Y(5:
1-C5Me4SiMe2NCMe3)(CH2CH2CH2CH3)(DME)] (2.431(3) and
2.477(3) Å) or [Y(5:1-C5Me4SiMe2NCMe3)(C4H3O)(DME)]
(2.387(2) and 2.473(2) Å).7d
Thecolorlesscrystalsof5areextremelyair-andmoisture-sensitive
and highly soluble in aromatic solvents, but only sparingly soluble
in aliphatic hydrocarbons. The NMR spectra at room temperature
show C2h-symmetry: two singlets are observed in the 1H as well as
in the 13C NMR spectra in benzene-d6 for the eight cyclopentadienyl
methyl groups and one singlet is observed for the methyl groups as
well as for the methylene group of the CH2SiMe2-bridge. The 13C
NMR spectrum shows a triplet at 126.7 ppm with 1JYC = 25.5 Hz for
the -carbon atom of the acetylide group. The splitting due to the
Y–C coupling indicates a dimeric structure of 5 with two -bridging
alkynyl ligands interacting with the two yttrium centers. In contrast
to the metallocene acetylide derivatives of the rare earths,10c–f no
evidence for the formation of carbon–carbon coupled products were
found in the reaction mixture. The reactivity of the hydride 2 toward
acetylene is similar to that of the bis(benzamidinato) complexes10h,i
and is different from that of Cp*2LnR complexes. More recently,
however, for the catalytic alkyne dimerization using [Ln(5:1-
C5Me4CH2SiMe2NPh)(CH2SiMe3)(THF)2] (Ln = Y, Lu) alkynyl
derivatives [Y(5:1-C5Me4CH2SiMe2NPh)(CCR)]2 have been
identified as the active species.10j
The reaction of the hydrido complex 2 with DME
Previously we argued that the higher reactivity of 2 compared to
that of [Y(5:1-C5Me4SiMe2NCMe3)(THF)(-H)]2 was due to the
shift in the monomer–dimer equilibrium towards higher monomer
concentration for 2. More recently, the conversion of the dimeric
alkyl complexes [Y(5:1-C5Me4SiMe2NCMe3)(-CH2CH2R)]2
into the monomeric adducts [Y(5:1-C5Me4SiMe2NCMe3)(-
CH2CH2R)(L)] (L = THF, DME) have been observed by adding an
excess of THF or DME.7d In an attempt to generate the monomeric
yttrium hydride complex [Y(L)H(DME)], we have reacted 2 with
2 equivalents of DME in toluene at room temperature. The reac-
tion occurred with cleavage of one of the C–O bonds of the DME
molecule, resulting in the formation of sparingly soluble crystals of
the bridging 2-methoxyethoxy complex [Y(L)(-OCH2CH2OMe-
O)]2 (6) (Scheme 4). Evidently, the hydrido ligand as a strong
nucleophile attacks the methoxy function of DME, activated by the
Lewis-acidic yttrium center in [Y(L)H(DME)]. This is in analogy
to the ether cleavage reaction promoted by reagents such as BBr3
and Me3SiI.11
Fig. 3 ORTEP drawing and numbering scheme of the molecular structure
of {[Y(L)(µ2-OCH2CH2OCH3)}2(THF)0.5 (6) with thermal ellipsoids drawn
at the 30% probability level. Only one of two crystallographically indepen-
dent molecules is shown. Hydrogen atoms are omitted for the sake of clarity.
The atoms marked with a prime (′) correspond to the symmetry equivalent
positions (−x, 1 − y, 1 − z). Selected bond lengths (Å) and bond angles (°):
Y1–O1 2.329(2), Y1–O1′ 2.251(2), Y1–N1 2.299(3), Y1–O2 2.424(2), Y1–
C1 2.653(3), Y1–C2 2.658(3), Y1–C3 2.704(3), Y1–C4 2.678(3), Y1–C5
2.650(3), Y1–Y1′ 3.8000(7); O1′–Y1–N1 107.78(8), O1–Y1–O1′ 67.88(8),
O1′–Y1–O2 131.37(7).
Conclusion
The hydride complex [Y(L)(THF)(-H)]2 (2) when com-
pared with the more “constrained” analogue [Y(5:1-
C5Me4SiMe2NCMe3)(THF)(-H)]27 shows high reactivity towards
terminal olefinic double bonds, and as shown for trans-stilbene,
even towards an internal double bond. This may be ascribed to the
more open coordination sphere around the yttrium center despite the
longer CH2SiMe2 link in the backbone of the ligand. Moreover, the
-bond metathesis of the initially formed alkyl complex by PhSiH3
seems to be sufficiently fast so that even in the case of 1,5-hexadi-
ene, the cyclization to give 1-phenylsilylmethylcyclopentane is not
a predominant reaction.
Experimental
General considerations
All operations were performed under an inert atmosphere of argon
and by using standard Schlenk-line or glovebox techniques. After
drying over KOH, THF was distilled from sodium benzophenone
ketyl. Hexane and toluene were purified by distillation from sodium/
triglyme benzophenone ketyl. Complexes 1 and 2 were prepared as
reported earlier.3a All other commercially available chemicals were
used after appropriate purification. NMR spectra were recorded on
a Bruker DRX 400 spectrometer (1H, 400 MHz; 13C, 101 MHz) in
C6D6 at 25 °C, unless otherwise stated. Chemical shifts for 1H and
13C spectra were referenced internally according to the residual
solvent resonances and reported relative to tetramethylsilane. Gas
chromatographic analyses were performed on a Fisons GC 8000 Top
instrument using a capillary column (30 m × 0.32 mm). Elemental
Scheme 4
Crystallization of 6 from THF gave the THF hemi-solvate
[Y(L)(-OCH2CH2OMe-O)]2·0.5THF. Due to the low solubility
of 6 even in polar organic solvents such as THF or pyridine, only 1H
NMR spectroscopic data could be obtained (with difficulty). Single
crystals suitable for an X-ray diffraction analysis were obtained by
slow cooling of a THF solution from 40 to 20 °C. Crystallographic
data are compiled in Table 1. The unit cell contains two crystallo-
graphically independent molecules of similar structure. An ORTEP
diagram of the structure of one molecule of 6 is shown in Fig. 3.
2 2 4 8
D a l t o n T r a n s . , 2 0 0 4 , 2 2 4 5 – 2 2 5 0

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analyses were performed by the Microanalytical Laboratory in the
Chemistry Department of Mainz University.
(110 mg, 1.00 mmol), and the reaction mixture was stirred at ambient
temperature for 72 h. The resulting viscous solution was quenched
with 0.5 mL of methanol, diluted with hexane, and filtered. The
solvent was removed in vacuo to give a highly viscous pale-yellow
oil. The oil was purified by flash chromatography (silica gel, eluent
pentane) and heated in dynamic vacuum (190 °C/10−2 mmHg) to
remove all volatiles. 190 mg (87%) of the oligomer was obtained as
a pale-yellow oil (Found: C, 77.02; H, 10.11. C14H22Si requires C,
77.05; H, 10.07); H (CDCl3, 25 °C) 0.84 (m, 4 H, CH2Si), 1.22–1.44
(m, 12 H, CH2), 4.24 (qnt, 3JHH = 3.6 Hz, 1JSiH = 92.4 Hz) and 4.28
(t, 3JHH = 3.6 Hz) (together 1 H (ratio 4.7:1)), 7.34 (m, 3 H), 7.55
(m, 2 H). C (CDCl3, 25 °C) 11.5 (CH2Si), 24.3 (CH2), 28.9 (CH2),
32.7 (CH2), 127.6, 129.2, 134.4, 135.9 (ring C).
Hydrosilylation of 1,5-hexadiene (molar ratio
C6H10 :PhSiH3 = 1:1)
To a solution of 1 (25.5 mg, 50 mol) in 0.5 mLof hexane were added
sequentially PhSiH3 (108 mg, 1.00 mmol) and 1,5-hexadiene (82 mg,
1.00 mmol) The reaction mixture was stirred at ambient temperature.
Small aliquots were taken for GC analysis and the reaction was found
to be complete after 2 h. The reaction mixture was quenched with
0.5 mL of methanol, diluted with hexane, and filtered. The volatiles
were removed in vacuo to give a pale yellow oil. The oil was purified
by flash chromatography (silica gel, eluent: pentane) and distilled
in vacuo (250 °C/4 × 10−2 mmHg). Distillation afforded 110 mg
(58%) of volatile products, shown by GC and NMR to be a mixture
consisting of 6-phenylsilyl-1-hexene, 1,6-bis(phenylsilyl)hexane,
1-phenylsilylmethylcyclopentane, and 1-phenylsilacycloheptane.
The residue was identified as a mixture of oligomers, 80 mg (42%)
(Found: C, 75.42; H, 9.71. C12H18Si requires C, 75.77; H, 9.46); H
(CDCl3, 25 °C) 0.79 (m, 4 H, CH2Si), 1.29–1.39 (m, 8 H, CH2), 4.27
(m, 1 H), 7.25 (m, 3 H), 7.50 (m, 2 H).
Hydrosilylation of 4-vinyl-1-cyclohexene
To a solution of 1 (25.5 mg, 50 mol) in 0.5 mL of hexane were
added sequentially PhSiH3 (108 mg, 1.00 mmol) and 4-vinyl-1-cy-
clohexene (108 mg, 1.00 mmol). The reaction mixture was stirred at
ambient temperature. Small aliquots were taken for GC analysis and
the reaction was found to be complete after 18 h. The reaction mix-
ture was quenched with 0.5 mL of methanol, diluted with hexane,
and filtered. The volatiles were removed in vacuo to give a pale-
yellow oil. Purification by flash chromatography (silica gel, eluent
pentane) and Kugelrohr distillation in vacuo (160 °C/10−2 mmHg)
gave 200 mg (93%) of 4-{2-(phenylsilyl)ethyl}cyclohex-1-ene4a as
a colorless oil (Found: C, 77.32; H, 9.04. C14H20Si requires C, 77.76;
H, 9.24); H (CDCl3, 25 °C) 0.97 (m, 2 H, CH2Si), 1.17 (m, 1 H), 1.41
(m, 2 H), 1.57 (m, 1 H), 1.62 (m, 1 H), 1.72 (m, 1 H), 2.01 (m, 2 H),
Hydrosilylation of 1,7-octadiene (molar ratio
C8H14 :PhSiH3 = 1:2)
To a solution of 1 (25.5 mg, 50 mol) in 0.5 mL of hexane were
sequentially added PhSiH3 (217 mg, 2.00 mmol) and 1,7-octadiene
(110 mg, 1.00 mmol). The reaction mixture was stirred at ambient
temperature and small aliquots were taken for GC analysis. The re-
action was found to be complete after 48 h. The reaction mixture was
quenched with 0.5 mLof methanol, diluted with hexane, and filtered.
The volatiles were removed in vacuo to give a pale-yellow oil. Pu-
rification by flash chromatography (silica gel, eluent: pentane) and
Kugelrohr distillation in vacuo (230 °C/10−2 mmHg) gave 299 mg
(94%) of 1,8-bis(phenylsilyl)octane as a colorless oil (Found: C,
73.74; H, 9.52. C20H30Si2 requires C, 73.60; H, 9.19); H (CDCl3,
25 °C) 1.02 (m, 4 H, CH2Si), 1.34 (m, 4 H, CH2), 1.42 (m, 4 H, CH2),
1.54 (m, 4 H, CH2), 4.38 (t, 3JHH = 3.6 Hz, 1JSiH = 96 Hz, 4 H, SiH2),
7.47 (m, 6 H), 7.66 (m, 4 H). C (CDCl3, 25 °C) 10.3 (CH2Si), 25.3
(CH2), 29.4 (CH2), 33.1 (CH2), 128.2, 129.7, 133.0, 135.5 (C6H5).
EI MS m/z (%): 326 (8%, M+), 249 (32%, C14H25Si2+) 248 (100%,
C14H24Si2+), 170 (93%, C8H18Si2+), 139 (47%, C8H15Si+).
3
1
2.12 (m, 1 H), 4.25 (t, JHH = 3.6 Hz, JSiH = 96 Hz, 2 H, SiH2Ph),
5.62 (d, 3JHH = 10.4 Hz, 1 H, HCCH), 5.64 (d, 3JHH = 10.4 Hz, 1 H,
HCCH), 7.35 (m, 3 H, C6H5), 7.55 (m, 2 H, C6H5). C (CDCl3,
25 °C) 7.4 (CH2Si), 25.5 (CH2CH2Si), 28.7 (CH2), 31.7 (CH2), 32.1
(CH2), 36.4 (CH), 126.7 (HC), 127.3 (HC), 128.2, 129.7, 132.9,
135.4 (C6H5). EI MS m/z (%): 216 (15%, M+), 215 (66%, C14H19Si+),
+
137 (29%, C8H13Si+), 107 (100%, PhSiH2 ).
[Y(5:1-C5Me4CH2SiMe2NCMe3){CH2CH(CH2)4}(THF)] (3)
To a suspension of 2 (114 mg, 13 mol) in hexane (5 mL), was added
at 0 °C a solution of 1,5-hexadiene (22 mg, 26 mol) in hexane
(1 mL). The reaction mixture was stirred for 30 min, concentrated,
and cooled to −30 °C to give 97 mg (74%) of colorless crystals
(Found: C, 61.06; H, 9.96; N, 3.22. C26H48NOSiY requires C, 61.56;
H, 9.24; N 2.75); H (C7D8, 25 °C) −0.11 (dd, 2JYH = 4 Hz, 3JHH = 7 Hz,
2 H, YCH2), 0.44 (s, 6 H, SiCH3), 1.22 (m, 4 H, -CH2, THF), 1.24
(m, 2 H, C5H9, -CH2), 1.40 (s, 9 H, C(CH3)3), 1.71, 1.87 (m, 2 H,
C5H9, -CH2), 1.97 (m, 2 H, C5H9, -CH2), 2.02, 2.08 (s, 2 × 6 H, ring
CH3), 2.15 (s, 2 H, CH2Si), 2.31 (m, 1 H, YCH2CH), 3.36 (m, 4 H,
-CH2, THF). C (C7D8, 25 °C) 7.8 (NSiCH3), 10.7, 13.8 (ring CH3),
17.4 (CH2Si), 22.5 (-CH2, THF), 24.2, 25.2 (C5H9, -CH2), 31.4
(C5H9, -CH2), 34.6 (C(CH3)3), 40.1 (C5H9, -CH2), 43.1 (CH2CH),
47.9 (d, 1JYC = 52.5 Hz, YCH2), 53.0 (C(CH3)3), 69.7 (-CH2, THF),
114.2, 114.9, 122.6 (ring C), 136.9 (ring C attached to CH2).
Hydrosilylation of 1,7-octadiene (molar ratio
C8H14 :PhSiH3 = 1:1)
To a solution of 1 (25.5 mg, 50 mol) in 0.5 mL of hexane were
added sequentially PhSiH3 (108 mg, 1.00 mmol) and 1,7-octadiene
(110 mg, 1.00 mmol). The reaction mixture was stirred at ambient
temperature. Small aliquots were taken for GC analysis and the
reaction was found to be complete after 2 h. The reaction mixture
was quenched with 0.5 mL of methanol, diluted with hexane, and
filtered. The volatiles were removed in vacuo to give a pale-yellow
oil. The oil was purified by flash chromatography (silica gel, eluent:
pentane). Two products were separated by vacuum distillation.
The first product: (160 °C/10−2 mmHg) 8-phenylsilyl-1-octene,
colorless oil, 152 mg (70%). H (CDCl3, 25 °C) 0.93 (m, 2 H,
CH2Si), 1.24–1.45 (m, 8 H, CH2), 2.02 (m, 2 H, CH2CHCH2), 4.27
(m, 2 H, SiH2), 4.96 (m, 2 H, CH2CH), 5.78 (m, 1 H, CH2CH),
7.38 (m, 3 H), 7.57 (m, 2 H). C (CDCl3, 25 °C) 9.8 (CH2Si), 24.8
(CH2), 28.6 (CH2), 28.9 (CH2), 32.5 (CH2), 33.6 (CH2CHCH2),
114.0 (CH2CH), 127.7, 129.3, 132.6, 135.0 (C6H5), 138.9
(CH2CH). EI MS m/z (%): 218 (15%, M+), 217 (22%, C14H21Si+),
189 (34%, C12H17Si+), 140 (21%, C8H17Si+), 107 (100%, C6H7Si+).
Anal. Calc. for C14H22Si: C, 77.05; H, 10.08. Found: C, 77.48;
H, 10.18. The second product (230 °C/10−2 mmHg) was 1,8-
bis(phenylsilyl)octane, colorless oil, 60 mg (27%).
[Y(5:1-C5Me4CH2SiMe2NCMe3){CH(CH2Ph)Ph}(THF)] (4)
To a solution of 2 (126 mg, 148 mol) in benzene (5 mL) was added
at room temperature, a solution of trans-stilbene (53 mg, 295 mol)
in benzene (1 mL). The reaction mixture was stirred for 6 days at
room temperature. The solvent was evaporated in vacuo and the re-
sulting pale yellow solid residue was dissolved in hexane (10 mL).
The solution was concentrated (~5 mL) and cooled to −30 °C to give
128 mg (72%) of pale yellow crystals (Found: C, 67.64; H, 8.40; N,
2.70. C34H50NOSiY requires C, 67.46; H, 8.25; N 2.31); H (C7D8,
25 °C) 0.43, 0.59 (s, 2 × 3 H, SiCH3), 0.90 (br s, 4 H, -CH2, THF),
1.30 (s, 9 H, C(CH3)3), 1.91, 1.97, 2.16, 2.27 (s, 4 × 3 H, ring CH3),
2.14, 2.22 (s, 2 × 1 H, CH2Si), 2.75 (m, 1 H, YCHPhCH2Ph), 3.17 (br
s, 4 H, -CH2, THF), 3.45 (dd, 1 H, YCHPhCHHPh), 3.70 (dd, 1 H,
YCHPhCHHPh), 6.40 (br t, 1 H, 3JHH = 7.2 Hz, C6H5), 6.64 (br d, 2 H,
3JHH = 7.2 Hz, C6H5), 6.97 (br t, 2 H, 3JHH = 7.2 Hz, C6H5), 7.19–7.36
(m, 3 H, C6H5), 7.54 (br d, 2 H, 3JHH = 7.2 Hz, C6H5). C (C7D8, 25 °C)
Silanolytic oligomerization of 1,7-octadiene
To a solution of 25.5 mg (50 mol) of 1 in 0.5 mL of hexane were
added sequentially PhSiH3 (108 mg, 1.00 mmol) and 1,7-octadiene
D a l t o n T r a n s . , 2 0 0 4 , 2 2 4 5 – 2 2 5 0
2 2 4 9

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8.2, 8.6 (NSiCH3), 11.0, 11.4, 11.9, 13.3 (ring CH3), 17.9 (CH2Si), 24.7
(-CH2, THF), 34.0 (C(CH3)3), 38.2 (CH2Ph), 53.7 (C(CH3)3), 58.0 (d,
1JYC = 25.0 Hz,YCH), 71.7 (-CH2, THF), 114.6 (C6H5), 116.1, 116.3,
117.2 (C5Me4 ring C), 119.0, 124.8, 125.3, 126.1, 131.0, (C6H5), 137.8
(C5Me4 ring C attached to CH2), 146.7, 152.7 (ipso-C, C6H5).
Acknowledgements
Financial support by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie is gratefully acknowledged.
A. A. T. thanks the Alexander von Humboldt-Foundation for a
postdoctoral fellowship.
[Y(5:1-C5Me4CH2SiMe2NCMe3)(CCCMe3)]2 (5)
References
To a solution of 2 (300 mg, 352 mol) in benzene (5 mL) was added
at room temperature a solution of tert-butylacetylene (58 mg,
706 mol) in benzene (1 mL). Evolution of a hydrogen gas was
observed. The reaction mixture was stirred for 1 h, benzene was
evaporated in vacuo, and the resulting off-white solid was recrys-
tallized from hexane at 0 °C; colorless microcrystals, yield 281 mg
(92%) (Found: C, 60.14; H, 8.29. C22H38NSiY requires C, 60.53; H,
8.77%); H (C6D6, 25 °C) 0.55 (s, 6 H, SiMe2), 1.12 (s, 9 H, C(CH3)3),
1.62 (s, 9 H, C(CH3)3), 2.13, 2.21 (s, 2 × 6 H, ring CH3), 2.23 (s, 2 H,
CH2Si). C (C6D6, 25 °C) 8.7 (NSiCH3), 12.2, 13.2 (ring CH3), 18.2
(CH2Si), 28.7 (CCC(CH3)3), 31.2 (C(CH3)3), 37.7 (C(CH3)3), 54.5
(NC(CH3)3), 116.7, 118.2, 129.3 (ring C), 126.7 (t, 1JYC = 25.5 Hz,
YCC), 127.0 (s, YCC), 136.8 (ring C attached to CH2).
1 (a) G. A. Molander and J. A. C. Romero, Chem. Rev., 2002, 102, 2161;
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(f) P. J. Chirik and J. E. Bercaw, Metallocenes, ed. R. L. Halterman and
A. Togni, Wiley-VCH, Weinheim, Germany, 1998, p. 111.
2 (a) P. J. Shapiro, E. E. Bunel, W. P. Schaefer and J. E. Bercaw,
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and J. E. Bercaw, Synlett, 1990, 74; (c) P. J. Shapiro, W. D. Cotter,
W. P. Schaefer, J. A. Labinger and J. E. Bercaw, J. Am. Chem. Soc.,
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(f) Z. Hou, Bull. Chem. Soc. Jpn., 2003, 76, 2253.
3 (a) A. A. Trifonov, T. P. Spaniol and J. Okuda, Organometallics, 2001,
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(b) G. A. Molander and P. J. Nichols, J. Am. Chem. Soc., 1995, 117,
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Chem. Soc., 1995, 117, 157.
5 P. Voth, T. P. Spaniol and J. Okuda, Organometallics, 2003, 22, 3921.
6 For recent work on the effect of various bridges in group 4 “geometrically
constrained” catalysts, see: K. Kunz, G. Erker, S. Doering, S. Bredeau,
G. Kehr and R. Froehlich, Organometallics, 2002, 21, 1031.
7 (a) K. C. Hultzsch, T. P. Spaniol and J. Okuda, Angew. Chem., Int. Ed.,
1999, 38, 227; (b) K. C. Hultzsch, P. Voth, K. Beckerle, T. P. Spaniol and
J. Okuda, Organometallics, 2000, 19, 228; (c) S. Arndt, K. C. Hultzsch,
P. Voth, T. P. Spaniol and J. Okuda, Organometallics, 2000, 19, 4690;
(d) P. Voth, S. Arndt, T. P. Spaniol, J. Okuda, L. J. Ackerman and
M. L. H. Green, Organometallics, 2003, 22, 65.
[Y(5:1-C5Me4CH2SiMe2NCMe3)(µ-OCH2CH2OMe-O)]2 (6)
To a solution of 2 (300 mg, 0.35 mmol) in 5 mL of toluene was
added at room temperature a solution of DME (63 mg, 0.70 mmol)
in 0.5 mL of toluene. Over a period of 72 h, a colorless precipitate
formed and was isolated from the mother-liquor. Recrystallization
from THF gave colorless crystals as a THF solvate; yield 0.26 g
(83%) (Found: C, 53.53; H, 8.45; N, 3.09. C40H76N2O4.5Si2Y2 re-
quires C, 53.95; H, 8.53; N 3.14%); H (pyridine-d5, 55 °C) 0.48,
0.52 (s, 2 × 3 H, SiCH3), 1.44 (s, 9 H, C(CH3)3), 1.67 (m, 2 H, -CH2,
free THF), 2.02 (br s, 7 H, OCH2CH2OCH3), 2.10, 2.13 (s, 2 × 6 H,
ring CH3), 2.16 (s, 2 H, CH2Si), 3.69 (m, 2 H, -CH2, free THF). 13
C
NMR spectra could not be obtained due to low solubility.
Crystal structure analysis of 3, 4 and 6
Relevant crystallographic data for 3, 4 and 6 are summarized in
Table 1. The data of 3 and 6 were collected with a Bruker AXS
diffractometer, reduced and corrected for absorption with the
program system SMART.13 The data of 4 were collected with
an Enraf Nonius CAD4 diffractometer and the program system
WinGX was used for the data reduction and absorption correction
using psi-scans.14 The structures were solved by Patterson and
difference Fourier syntheses (SHELXS-86).15 Complexes 4 and
6 crystallize with two independent molecules in the unit cell.
The lattice of 6 contains disordered thf. All hydrogen atoms were
included into calculated positions with torsional refinement of the
methyl groups. Only the hydrogen atoms attached to C17 and C51,
which belong to the two crystallographically independent molecules
of 4, were refined in their position. All independent reflections were
8 X. Zhou and M. Zhu, J. Organomet. Chem., 2002, 647, 28.
9 A. Mandel and J. Magull, Z. Anorg. Allg. Chem., 1996, 622, 1913.
10 (a) W. J. Evans and A. L. Wayda, J. Organomet. Chem., 1980, 202,
C6; (b) T. J. Marks and R. D. Ernst, in Comprehensive Organometal-
lic Chemistry, ed. G. Wilkinson, F. G. A. Stone and E. W. Abel, Per-
gamon Press, Oxford, 1982, ch. 21; (c) K. H. Den Haan, Y. Wielstra
and J. H. Teuben, Organometallics, 1987, 6, 2053; (d) W. E. Evans,
R. A. Keyer and J. W. Ziller, Organometallics, 1993, 12, 2618;
(e) C. M. Forsyth, S. P. Nolan, S. L. Stern and T. J. Marks, Organo-
metallics, 1993, 12, 3618; (f) H. J. Heeres, J. Nijhoff and J. H. Teuben,
Organometallics, 1993, 12, 2609; (g) T. Dubé, J. Guan, S. Gambarotta
and G. P. A. Yap, Chem. Eur. J., 2001, 7, 374; (h) R. Duchateau,
C. T. van Wee and J. H. Teuben, Organometallics, 1996, 15, 2291;
(i) R. Duchateau, C. T. van Wee, A. Meetsma and J. H. Teuben, J. Am.
Chem. Soc., 1993, 115, 4931; (j) M. Nishiura, Z. Hou, Y. Wakatsuki,
T. Yamaki and T. Miyamoto, J. Am. Chem. Soc., 2003, 125, 1184.
11 M. V. Bhatt and S. U. Kulkarni, Synthesis, 1983, 249.
12 W. J. Evans, R. Dominguez and T. P. Hanusa, Organometallics, 1986, 5,
1291.
13 Siemens, ASTRO, SAINT and SADABS: Data Collection and
Processing Software for the SMART System, Siemens Analytical X-ray
Instruments Inc., Madison, WI, USA, 1996.
14 L. J. Farrugia, WinGX—Version 1.64.02, An Integrated System of
Windows Programs for the Solution, Refinement andAnalysis of Single-
crystal X-Ray Diffraction Data, J. Appl. Crystallogr., 1999, 32, 837.
15 G. M. Sheldrick, SHELXS-86, Program for Crystal Structure Solution,
University of Göttingen: Göttingen, Germany, 1986.
2
used in the refinement by full-matrix least-squares against all Fo
data (SHELXL-97).16 The non-hydrogen atoms were refined with
anisotropic thermal parameters. In the crystal structure of 3, split
positions for the atoms C18 and C20 of the cyclopentylmethyl
ligand where introduced which were refined with isotropic thermal
parameters. For the graphical representation, the program ORTEP-
III was used as implemented in the program system WINGX.
CCDC reference numbers 236764, 236765 and 236766 for 3, 4
and 6, respectively.
See http://www.rsc.org/suppdata/dt/b4/b406071g/ for crystallo-
graphic data in CIF or other electronic format.
16 G. M. Sheldrick, SHELXL-97, Program for Crystal Structure Refine-
ment, University of Göttingen: Göttingen, Germany, 1997.
2 2 5 0
D a l t o n T r a n s . , 2 0 0 4 , 2 2 4 5 – 2 2 5 0