Synthesis, structure and hydrosilylation activity of neutral and cationic rare-earth metal silanolate complexes

Article abstract of DOI:10.1039/b512285f

Rare-earth metal alkyl tri(tert-butoxy)silanolate complexes [Ln{μ,η²-OSi(O^tBu)₃}(CH ₂SiMe₃)₂]₂ (Ln = Y (1), Tb (2), Lu (3)) were prepared via protonolysis of the appropriate tris(alkyl) complex [Ln(CH₂SiMe₃)₃(thf)₂] with tri(tert-butoxy)silanol in pentane. Crystal structure analysis revealed a dinuclear structure for 1 with square pyramidal geometry at the yttrium centre. The silanolate ligand coordinates in an η²-bridging coordination mode giving a 4-rung truncated ladder and non-crystallographic inversion centre. Addition of two equiv. of 12-crown-4 to a pentane solution of 1 or 3 respectively gave [Ln{OSi(O^tBu)₃}(CH₂SiMe ₃)₂(12-crown-4)]·12-crown-4 (Ln = Y (4), Lu (5)). Crystal structure analysis of 5 showed a slightly distorted octahedral geometry at the lutetium centre. The silanolate ligand adopts an η¹- terminal coordination mode, whilst the crown ether unit coordinates in an unusual κ³-fashion. Reaction of 1-3 with [NEt ₃H]⁺[BPh₄]^- in thf yielded the cationic derivatives [Ln{OSi(O^tBu)₃}(CH ₂SiMe₃)(thf)₄]⁺[BPh ₄]^- (Ln = Y (6), Tb (7) and Lu (8)); coordination of crown ether led to compounds of the form [Ln{OSi(O^tBu)₃} (CH₂SiMe₃)(L)(thf)_n]⁺[BPh ₄]^- (Ln = Y, Lu, L = 12-crown-4, n = 1 (9, 10); Ln = Y, Lu, L = 15-crown-5, n = 0 (11, 12)). Reaction of 1 with [NMe₂PhH] ⁺[B(C₆F₅)₄]^-, [Al(CH ₂SiMe₃)₃] or BPh₃ in thf gave the ion pairs [Y{OSi(O^tBu)₃}(CH₂SiMe ₃)(thf)₄]⁺[A]^- ([A]^- = [B(C₆F₅)₄]^- (13), [Al(CH ₂SiMe₃)₄]^- (14), [BPh ₃(CH₂SiMe₃)]^- (15)), whilst two equiv. [NMe₂PhH]⁺[BPh₄]^- with 1 in thf produced the dicationic ion triple [Y{OSi(O^tBu) ₃}(thf)₆]²⁺[BPh₄]^- ₂ (16). Crystal structure analysis revealed that 16 is mononuclear with pentagonal bipyramidal geometry at the yttrium centre. The silanolate ligand coordinates in an η¹-terminal fashion. All diamagnetic compounds have been characterized by NMR spectroscopy. 1, 3, 4, 6 and 13 were tested as olefin hydrosilylation pre-catalysts with a variety of substrates; 1 was found to be highly active in 1-decene hydrosilylation. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b512285f

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis, structure and hydrosilylation activity of neutral and cationic
rare-earth metal silanolate complexes†
Benjamin R. Elvidge, Stefan Arndt, Thomas P. Spaniol and Jun Okuda*
Received 30th August 2005, Accepted 9th November 2005
First published as an Advance Article on the web 6th December 2005
DOI: 10.1039/b512285f
2
Rare-earth metal alkyl tri(tert-butoxy)silanolate complexes [Ln{l,g -OSi(OtBu)3}(CH2SiMe3)2]2
(Ln = Y (1), Tb (2), Lu (3)) were prepared via protonolysis of the appropriate tris(alkyl) complex
[Ln(CH2SiMe3)3(thf)2] with tri(tert-butoxy)silanol in pentane. Crystal structure analysis revealed a
dinuclear structure for 1 with square pyramidal geometry at the yttrium centre. The silanolate ligand
2
coordinates in an g -bridging coordination mode giving a 4-rung truncated ladder and
non-crystallographic inversion centre. Addition of two equiv. of 12-crown-4 to a pentane solution of 1
or 3 respectively gave [Ln{OSi(OtBu)3}(CH2SiMe3)2(12-crown-4)]·12-crown-4 (Ln = Y (4), Lu (5)).
Crystal structure analysis of 5 showed a slightly distorted octahedral geometry at the lutetium centre.
1
The silanolate ligand adopts an g -terminal coordination mode, whilst the crown ether unit coordinates
in an unusual j3-fashion. Reaction of 1–3 with [NEt3H]+[BPh4]− in thf yielded the cationic derivatives
[Ln{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[BPh4]− (Ln = Y (6), Tb (7) and Lu (8)); coordination of crown
ether led to compounds of the form [Ln{OSi(OtBu)3}(CH2SiMe3)(L)(thf)n]+[BPh4]− (Ln = Y, L u , L =
12-crown-4, n = 1 (9, 10); Ln = Y, L u , L = 15-crown-5, n = 0 (11, 12)). Reaction of 1 with [NMe2PhH]+-
[B(C6F5)4]−, [Al(CH2SiMe3)3] or BPh3 in thf gave the ion pairs [Y{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[A]−
([A]− = [B(C6F5)4]− (13), [Al(CH2SiMe3)4]− (14), [BPh3(CH2SiMe3)]− (15)), whilst two equiv.
[NMe2PhH]+[BPh4]− with 1 in thf produced the dicationic ion triple [Y{OSi(OtBu)3}(thf)6]2+[BPh4]−
2
(16). Crystal structure analysis revealed that 16 is mononuclear with pentagonal bipyramidal geometry
1
at the yttrium centre. The silanolate ligand coordinates in an g -terminal fashion. All diamagnetic
compounds have been characterized by NMR spectroscopy. 1, 3, 4, 6 and 13 were tested as olefin
hydrosilylation pre-catalysts with a variety of substrates; 1 was found to be highly active in 1-decene
hydrosilylation.
catalysts,5 or in some cases as molecular precursors for the
Introduction
preparation of metal silicate materials.6 Despite this interest and
Neutral rare-earth metal dialkyl complexes incorporating a single
although the first transition metal complexes containing the
monoanionic spectator ligand [Ln(LnX)R2Lꢀm] (LnX = monoan-
monoanionic tri(tert-butoxy)silanolate ligand were reported in
ionic ligand, Lꢀm = neutral ligand)1 and cationic rare-earth metal
1969,7 rare-earth metal examples are limited to La complexes that
mono(alkyl) complexes [Ln(LnX)RLꢀm]+[A]− (A = anion)2 are
model silicate-grafted rare-earth metal aluminates active in iso-
prene polymerisation,8 homoleptic tris{tri(tert-butoxy)silanolate}
of increasing importance in organo–rare-earth metal chemistry.
complexes,9 pre-catalysts for the ring-opening of lactones10 and
various Sm species.11 Cationic rare-earth metal siloxy complexes
are not known2,4 and Group 4 analogues are rather scarce.12
We present here neutral and cationic rare-earth metal alkyl
complexes supported by the tri(tert-butoxy)silanolate ligand and
their assessment as pre-catalysts for olefin hydrosilylation.
For instance, recent studies of cationic rare-earth metal alkyl
complexes incorporating trimethylsilylmethyl and methyl ligands
have implicated the dicationic methyl complex as the active species
in ethylene and 1-hexene polymerisation.3 Many heteroleptic
neutral and cationic rare-earth metal alkyls rely on the Cp-ligand
framework to stabilise the metal centre, although recently non-Cp
ligands based on alkoxy, aryloxy, amido and related functionalities
have also been applied.4 More specifically, rare-earth and transi-
tion metal complexes of ligands derived from silanol [SiR3(OH)],
silanediol [SiR2(OH)2], a,x-siloxanediol [O(SiR2OH)2], silanetriol
Results and discussion
[SiR(OH)3] and incompletely condensed silsesquioxane [SiRO3/2
]
Neutral complexes
2n
have been used as soluble “model compounds” for silica-supported
2
The syntheses of [Ln{l,g -OSi(OtBu)3}(CH2SiMe3)2]2 (Ln = Y (1),
Tb (2), Lu (3)) cleanly proceeded from equimolar amounts of the
appropriate rare-earth metal tris(alkyl) [Ln(CH2SiMe3)3(thf)2]13
and the silanol HOSi(OtBu)3 in pentane at room temperature
(Scheme 1).14 1–3 are highly soluble in all common aliphatic,
aromatic and ethereal solvents and represent rare examples of
thf-free non-cyclopentadienyl rare-earth metal alkyl complexes.4
Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1,
D-52074, Aachen, Germany. E-mail: jun.okuda@ac.rwth-aachen.de
† Electronic supplementary information (ESI) available: VT and 1H NMR
spectra of 1, 4, 9, 16; time–conversion plots for catalytic hydrosily-
lation, molecular structure of [Sc{OSi(OtBu)3}(CH2SiMe3)2]. See DOI:
10.1039/b512285f
890 | Dalton Trans., 2006, 890–901
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
Scheme 1
X-Ray diffraction quality crystals of 1 were grown by evapo-
ration of a hexamethyldisiloxane solution at room temperature. 1
is dimeric in the crystalline state, with bridging silanolate oxygen
atoms between the yttrium centres, which are related by a non-
crystallographic inversion centre (Fig. 1, Table 1).15 The Y–C
side, arising from the chelation of one tert-butoxy functionality
to each metal, giving overall a 4-rung truncated ladder. This
second set of 4-membered rings is almost flat (dihedral angle
Y(1)–O(1)–O(2)–Si(3) = 177.76(18)◦ and Y(2)–O(5)–O(6)–Si(6) =
174.7(2)◦) but extremely strained at the metal (O(1)–Y(1)–O(2) =
62.33(11)◦). The central core is asymmetric, with the Y(1)–O(6)
and Y(2)–O(2) chelate-free edge contacts shorter than Y(1)–
O(2) and Y(2)–O(6). There is a slight elongation of the Si–O
separation for the two atoms involved in the 4-membered chelate
(Si(6)–O(5) = 1.674(4) vs. Si(6)–O(6) = 1.615(3), Si(6)–O(7) =
˚
bond lengths (Y(1)–C(1) = 2.386(5), Y(1)–C(5) = 2.366(5) A)
˚
are within the 2.35(1)–2.45(2) A range typical of neutral yttrium
trimethylsilylmethyl complexes (Table 2).16 The geometry at each
yttrium centre is best described as square pyramidal, with one
trimethylsilylmethyl group occupying the apical position. As well
as the puckered 4-membered ring (dihedral angle Y(2)–O(2)–
O(6)–Y(1) = 161.08(14)◦) described by these yttrium and oxygen
atoms, there are also two other 4-membered rings on either
˚
1.609(4), Si(6)–O(8) = 1.603(3) A and Si(3)–O(1) = 1.675(44)
vs. Si(3)–O(2) = 1.613(3), Si(3)–O(3) = 1.603(3), Si(3)–O(4) =
˚
1.611(3) A).
Table 1 Crystal data for 1, 5 and 16a
1
5
16
Chemical formula
Formula weight
T/K
C40H98O8Si6Y2
1053.54
110(2)
0.71073
C28H65LuO8Si3·C8H16O4
C84H115B2O10SiY·C4H8O
965.26
110(2)
0.71073
1495.48
110(2)
0.71073
Monoclinic, P21/c (no. 14)
˚
k/A
¯
Crystal system, space group
Monoclinic, P21/n (no. 14)
Triclinic, P1 (no. 2)
˚
a/A
15.406(3)
20.736(4)
19.089(4)
90
103.003(4)
90
5942(2)
4
1.178
11.9494(7)
13.9573(9)
14.4939(9)
86.7120(10)
76.0020(10)
88.5490(10)
2341.5(3)
2
13.0500(12)
25.186(2)
25.083(2)
90
94.606(2)
90
8217.6(12)
4
1.209
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
D
Calc./Mg m−3
)
1.369
0.0392, 0.0967
0.0459, 0.1109
R(Fo2), Rw(Fo2) [I > 2r(I)]
R(Fo2), Rw(Fo2) (all data)
0.0661, 0.1216
0.167, 0.1511
0.0479, 0.0969
0.1011, 0.1144
a R(Fo2) and Rw(Fo2) are the final R indices.
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 890–901 | 891
©

View Article Online
◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for 1, 5 and 16
1
5
16
Y(1)–C(1)
Y(1)–C(5)
Y(1)–O(1)
Y(1)–O(2)
2.386(5)
2.366(5)
2.352(3)
2.370(3)
2.211(3)
Lu–C(9)
Lu–C(13)
Lu–O(1)
Lu–O(2)
Lu–O(3)
Lu–O(9)
O(2)–Lu–O(9)
C(13)–Lu–O(3)
C(9)–Lu–O(1)
2.374(4)
2.373(4)
2.445(3)
2.370(3)
2.477(3)
Y–O(1)
Y–O(5)
Y–O(6)
Y–O(7)
Y–O(8)
Y–O(9)
Y–O(10)
O(1)–Y–O(10)
Y–O(1)–Si
2.0705(15)
2.4257(15)
2.3802(15)
2.3892(15)
2.3730(15)
2.4216(16)
2.4102(15)
Y(1)–O(6)
C(1)–Y(1)–C(5)
O(2)–Y(1)–O(6)
O(1)–Y(1)–O(2)
O(1)–Si(3)–O(2)
113.2(2)
2.060(3)
73.59(12)
62.33(11)
95.99(17)
154.19(13)
159.42(14)
154.41(14)
178.72(6)
162.30(9)
1
via lone pair donation from two oxygen atoms at the same g -
coordinated silanolate ligand (“B”, Scheme 1) or by the union of
2
two terminally-bonded g -complexes (“A”, Scheme 1).
1 and 3 give rise to single resonances for all chemically equivalent
1
groups at room temperature in C7D8 in the 1H and 13C{ H}
NMR spectra; characteristic doublets were seen for the yttrium
methylene groups of 1 (dH − 0.33 ppm, J(YH) = 3.4 Hz; dC
39.5 ppm, J(YC) = 43.0 Hz). At low temperature, the coordination
of one tert-butoxy group to the yttrium centre is resolved (DG‡ =
51.5 0.1 kJ mol−1), giving rise to two singlets of rather different
1
chemical shift values (Dd = 0.15 ppm) in a 2 : 1 ratio in the H
NMR spectrum, consistent with the X-ray data. Furthermore,
at low temperature the diastereotopic yttrium methylene protons
give rise to an AB quartet (J(HH) = 11.0 Hz, J(YH) coupling
not resolved, DG‡ = 52.6 0.1 kJ mol−1). A single resonance was
noted in the 29Si NMR spectra for the silanolate ligand in the
neutral species 1, within the range reported for the free ligand and
other similar silanols, whose chemical shift values show a small
solvent dependency.18 The 89Y NMR spectrum of 1 (C6D6, 298
K: dY 863.2 ppm) gave a single resonance of a similar chemical
shift value to the previously reported neutral tris(alkyl) complex
[Y(CH2SiMe3)3(thf)2].19
Fig. 1 Molecular structure of 1 (ellipsoids drawn at the 50% probability
level, hydrogen atoms and methyl groups omitted for clarity).
1
2
A
mixture of terminal-g -coordinating and bridging-g -
Temperature-dependent behaviour in solution has been noted
for [Zn{OSi(OtBu)3}2]2, which is dimeric in the solid state
coordinating modes were observed in the series of seven crystal-
lographically characterized Sm compounds recently published.11b
No terminal-g - or bridging-g -coordinating modes of this ligand
have been found for the rare-earth metals.8–11 However, since the
homoleptic zinc and hafnium compounds co-crystallise as two
1
2
2
1
with inequivalent bridging and terminal g - and g -coordinated
silanolate units.20 At room temperature in C7D8 a single resonance
1
1
was observed for the tert-butoxy groups in the H and 13C{ H}
NMR spectra, assigned to a monomeric formulation, whilst at
low temperature two singlets of intensity ratio 1 : 1 were observed.
2
1
1
isomeric forms [M{g -OSi(OtBu)3}{g -OSi(OtBu)3}3] and [M{g -
OSi(OtBu)3}4] (M = Zr, Hf: isotypic), the energy difference
1
1
2
The existence of a stable, monomeric, terminally g -coordinated
between terminal g - and g -coordination modes may be rather
small.17 Asymmetric bimetallic central cores involving two or
more bridging silanolate oxygen atoms are common across the
structure for 1 is highly unlikely however, given the ubiquity
of thf or other ethers when the trimethylsilylmethyl ligand is
used;1–4 base-free 3-coordinate rare-earth metal alkyl compounds
are known commonly only for the larger bis(trimethylsilyl)methyl
ligand, e.g. [Ln{CH(SiMe3)2}3].21 Thus a dimeric (or higher order)
structure in aromatic solution is the most likely, with the rapidly
exchanging tert-butoxy groups “frozen-out” within the dinuclear
structure at lower temperatures.
above series of Sm compounds.11b In [Sm{l,g -OSi(OtBu)3}{g -
2
1
OSi(OtBu)3}2]2, in which one chelate arm coordinates each metal
centre, and [Cp*Sm{l,g -OSi(OtBu)3}3Sm], in which all three
2
chelates appear at the non-Cp Sm centre, the longer Sm–O
bond is always at the four-membered ring created by the chelate.
Furthermore, in a similar manner to 1 all Sm compounds show
an elongation of the chelating Si–O separation with respect
to the other Si–O distances. The elongated Si–O and M–O
contacts can be assigned to charge delocalisation across the 4-
membered M–O–Si–O ring. A similar elongation at the chelating
Two resonances of 2 : 1 intensity arising from the tert-butoxy
groups of very similar chemical shift value (Dd = 0.02 ppm) were
observed for 1 and 3 in thf-d8 solution at room temperature;
1
the tert-butoxy region of the H NMR spectrum of 1 remained
essentially unchanged at −70 ◦C. Three separate sets of signals
of varying intensity arising from the LnCH2SiMe3 (Ln = Y, L u )
Si–O unit was observed for [La{l,g -OSi(OtBu)3}(l-MeAlMe2)(l-
2
Me2AlMe2)2],8 whilst an asymmetric M2O2 core was also observed
for [Nd(OSiHtBu2)2(l-OSiHtBu2)]2, which may chelate via an
agostic Nd–H interaction.9 Dimerization in 1 may formally occur
1
1
13
groups were also observed in both the H and { H} C NMR
spectra of both 1 and 3. After 24 h at room temperature, the
892 | Dalton Trans., 2006, 890–901
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
two upfield resonances arising from both 1 and 3 remained in a
1 : 4 ratio, but the downfield resonance had almost disappeared.
We assume that the downfield resonance represents the dimeric
species, which is slowly broken-up into monomeric units by thf.
At −70 ◦C, an AB quartet of doublets (dH − 1.05 ppm, J(HH) =
11.3 Hz, J(YH) = 2.4 Hz, DG‡ = 47.3 0.1 kJ mol−1) and a doublet
(dH − 0.92 ppm, d, J(YH) = 2.7 Hz) were observed for 1.22
The addition of different amounts of thf to a C6D6 solution
of 1 at room temperature gave both the thf-adduct of the dimeric
complex and the monomeric thf-complex† (Scheme 2). Two equiv.
of thf gave a small low-frequency shift of the Y–CH2SiMe3 group
resonances from the thf-free compound 1 (dH − 0.27 ppm (CH2),
0.37 ppm (SiMe3)) to the dimeric species with coordinated thf
(dH − 0.35 ppm (CH2), 0.33 ppm (SiMe3)). A small amount of
monomeric thf-adduct (dH − 0.71 ppm (CH2), 0.27 ppm (SiMe3))
was also observed. This complex predominated in the presence of
25 equiv. of thf (dH − 0.73 ppm (CH2), 0.29 ppm (SiMe3)). When 40
equiv. of thf were added, three different peaks of varying intensity
around dH − 0.75 ppm were observed, in a similar manner to
the spectrum of 1 in thf-d8. The extent to which the monomeric
or dimeric structures are preferred was only slightly affected by
heating to 80 C. [Cp*Sm{l,g -OSi(OtBu)3}3Sm] gives rise to a
single broad peak (dH 3.10 ppm) for the tert-butoxy groups in C6D6
at room temperature and to additional signals arising from the
same groups when dissolved in thf-d8 (dH 2.08, 1.50, 3.20 ppm),11b
an effect attributed to the formation of the monomeric complexes
[SmCp*{OSi(OtBu)3}(thf)x] and [Sm{OSi(OtBu)3}2(thf)x].
Fig. 2 Molecular structure of 5 (ellipsoids drawn at the 50% probability
level, hydrogen atoms and lattice 12-crown-4 omitted for clarity, only one
of two disordered positions at O(11) and O(12) shown).
◦
2
complexes,24 whilst the Lu–O(12-crown-4) separations (Lu–O(1) =
˚
2.445(3), Lu–O(2) = 2.370(3), Lu–O(3) = 2.477(3) A) are
slightly shorter than those in the previously reported seven-
coordinate tris(alkyl) complex [Lu(CH2SiMe3)3(12-crown-4)] (Lu–
23
˚
O(12-crown-4): 2.52(1)–2.60(1) A).
In both aromatic and chlorinated hydrocarbon solution the
neutral 12-crown-4 compounds 4 and 5 give rise to an AB
1
quartet in the H NMR spectrum (4 (C7D8): J(HH) = 11.5 Hz,
J(YH) = 3.2 Hz; 5 (C6D6): J(HH) = 11.7 Hz) in a similar
manner to the low temperature case for 1. Y–H coupling was
also resolved for 4 (J(YH) = 3.2 Hz). Surprisingly given the
asymmetrical j3-coordination mode of 12-crown-4 shown in the
crystal structure of 5, two higher-order multiplets were observed
in the 1H NMR spectrum (4 (C7D8): dH 2.80, 3.68 ppm; 5 (C6D6):
dH 2.95, 3.81 ppm) suggestive of symmetrical j4-coordination of
12-crown-4.23 Either the crown ether adopts a j3-coordination
mode in solution with a “carousel” rotation that is rapid on the
NMR timescale, as observed for [Sc(CH2SiMe3)3(12-crown-4)],19
or greater coordination sphere flexibility in solution allows for a
j4-coordination mode. Trace amounts of 1 and 3 respectively were
also noted in the spectra. Integration of the spectra indicated one
free and one coordinated 12-crown-4 per metal centre, consistent
with elemental analysis and the result of the crystal structure
determination for 5.25 In thf-d8 a single, broad resonance was
observed for the 12-crown-4 unit of 4 (dH 3.66 ppm), whilst two
resonances arising from the Y–CH2 group were found (dH − 0.95,
−0.79 ppm, d, J(YH) = 2.9 Hz), in a similar manner to 1 in
thf-d8. We attribute this to fluxional 12-crown-4 coordination, as
previously observed for [Y(CH2SiMe3)3(12-crown-4)].23
Scheme 2
The crown-ether adducts [Ln{OSi(OtBu)3}(CH2SiMe3)2(12-
crown-4)]·(12-crown-4)n (Ln = Y (4), Lu (5)) were isolated from
1 and 3 with 2 equiv. of 12-crown-4 respectively in pentane at
−30 ◦C. The extra equivalent of 12-crown-4 (n = 1 by NMR
spectroscopy and EA for 4 and 5), was presumably promoted
by the low temperature conditions and cannot be excluded
by using stoichiometric amounts of this reagent. The use of
[Y(CH2SiMe3)3(12-crown-4)]23 as a starting material for 4 failed
to give a pure product.
Crystals of 5 suitable for X-ray diffraction were grown
in pentane at −30 ◦C. 5 is monomeric in the crystalline
1
state and the silanolate ligand adopts an g -terminal coordi-
nation mode (Fig. 2). Only three oxygens of the 12-crown-
4 unit coordinate to the metal centre. This j3-bonding mode
was observed for [Sc(CH2SiMe3)3(12-crown-4)]19 but not for
[Ln(CH2SiMe3)3(12-crown-4)] (Ln = Y, Lu), which are isostruc-
tural and exhibit symmetrical j4-coordination of 12-crown-4.23
The geometry at the lutetium centre is distorted octahedral,
the O(2)–Lu–O(9), C(13)–Lu–O(3) and C(9)–Lu–O(1) angles are
all slightly less than 180◦ (Table 2). The Lu–C bond lengths
Monocationic complexes
The cationic alkyl species [Ln{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[BPh4]−
(Ln = Y (6), Tb (7), Lu (8)) were isolated from an equimolar
thf solution of 1–3 respectively and [NEt3H]+[BPh4]− (Scheme 1).
Furthermore, a suspension of 6 or 8 in heptane with a slight excess
of 12-crown-4 or 15-crown-5 yielded the crown ether-adducts
˚
(Lu–C(9) = 2.374(4), Lu–C(13) = 2.373(4) A) are within the
˚
2.29(2)–2.40(1) A range typical of lutetium trimethylsilylmethyl
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 890–901 | 893
©

View Article Online
[Ln{OSi(OtBu)3}(CH2SiMe3)(12-crown-4)(thf)]+[BPh4]− (Ln =
Y (9), Lu (10)) and [Ln{OSi(OtBu)3}(CH2SiMe3)(15-crown-
5)]+[BPh4]− (Ln = Y (11), Lu (12)) respectively as colourless
microcrystals. The ion pairs 6–12 are highly soluble in chlorinated
and ethereal solvents, but insoluble in aromatic and aliphatic
hydrocarbons. Monocationic thf-complexes of yttrium supported
by the anions [B(C6F5)4]− (13), [Al(CH2SiMe3)4]− (14) and
[BPh3(CH2SiMe3)]− (15) were also synthesized and characterized
by NMR spectroscopy. Whilst the synthesis of 15 proceeded
rapidly at room temperature, 14 required 24 h for complete
conversion to the cation. Synthesis of the 12-crown-4 supported
yttrium monocationic complex 9 was also possible at room
temperature in thf-d8 from 4 with one equiv. of [NEt3H]+[BPh4]−
with concomitant SiMe4 formation.
6, 13–15 than for the neutral compound 1, which is also consistent
with our earlier observations of similar compounds and can
be assigned to a shorter Y–C separation.19 The low intensity
resonances were assigned on the basis of their chemical shift values
as minor bis(alkyl) [Ln(CH2SiMe3)2(thf)n]+[A]− and bis(silanolate)
[Ln{OSi(OtBu)3}2(thf)n]+[A]− impurities (Scheme 3). An equilib-
rium between major and minor compounds in solution can be
excluded, since their ratios do not change with temperature in
common NMR solvents. Major and minor products were noted,
but the very similar solubility of the three species prevented their
separation by re-crystallisation.26
We observed that the ions in compounds 6, 8–15 are separated
by solvent molecules in solution, since NMR spectroscopy (1H,
1
13C{ H}, 11B, 19F, 27Al) gave rise to resonances indicative of high-
symmetry anions. Furthermore, the 11B chemical shift values for
the [BPh4]− anion were independent of the cation present. Two
resonances of very similar chemical shift value were found for the
silanolate group of the monocationic species (14: dSi − 99.6 ppm,
d, J(YSi) = 10.6 Hz and 100.1 ppm, d, J(YSi) = 9.6 Hz), consistent
1
with the observations in the 1H and 13C{ H} NMR spectra of two
tert-butoxy resonances of slightly different chemical shift values.
The 89Y NMR spectrum of 14 (thf-d8, 298 K: dY 666.2 ppm) gave a
single resonance of a similar chemical shift value to the previously
reported cationic bis(alkyl) complexes [Y(CH2SiMe3)2(thf)4]+[A]−,
the low frequency shift with respect to 1 consistent with increasing
nuclear charge and with the reported pattern for cationic yttrium
complexes.19
Scheme 3
The bis(alkyl) co-product may form by reaction of the Lewis
or Brønsted acid with the silanolate functionality rather than
the alkyl group, as noted in the attack of MAO at the Ti–
or Zr–silsesquioxane bond in [MCpꢀꢀ{(c-C5H9)7Si8O13}(CH2Ph)2]
1H NMR studies of the monocationic species 6, 8–15 in thf-d8
and CD2Cl2 revealed two resonances arising from the tert-butoxy
groups of very similar chemical shift values (Dd = 0.02 ppm). Two
clearly resolved peaks of different intensity arising from Ln–CH2
(Cpꢀꢀ = C5H3(SiMe3)2).27 However, the H, 11B and 27Al NMR
1
spectroscopic studies for 6, 8–15 indicated the formation of
[Al(CH2SiMe3)4]− and [BPh3(CH2SiMe3)]− alone,19 while the
known yttrium tris(silanolate) species [Y{OSi(OtBu)3}3(thf)0.5]
failed to react with BPh3 or [NEt3H]+[BPh4]− in thf at room
temperature overnight.28
1
and SiMe3 protons were observed in the H NMR spectrum in
thf-d8 and CD2Cl2 for all diamagnetic monocationic complexes,
the relative intensities of which are a sensitive function of the
metal and anion, whilst 9–12 gave rise to corresponding sets
of resonances for the diastereotopic protons at the crown ether
ligand. The diastereotopic Y–CH2 protons were not resolved at the
low temperature limit for 6 in thf-d8 or CD2Cl2. The high intensity
resonances arise from the respective title compounds, the 1H and
Redistribution of [Ln(CH2SiMe3)2(thf)n]+[A]− to give a mixture
of cationic bis(alkyl) and bis(silanolate) species is possible; such
processes have been recognised for some time for rare-earth metal
complexes.29 Furthermore, although the siloxyaluminium alkyl
cations [Al2{l-OSi(OR)3}2Me3(NMe2Ph)]+[B(C6F5)4]− (R = Bu,
t
1
13C{ H} NMR chemical shift values for which show a slight anion
SiMe3) and [Al2{l-OSi(tBuMe2)}2Me3(NMe2Ph)]+[B(C6F5)4]−,
prepared by the addition of half an equiv. per alu-
minium of [NMe2PhH]+[B(C6F5)4]− to the dimeric species
[Al{l-OSi(OR)3}Me2]2 and [Al{l-OSi(tBuMe2)}Me2]2, are stable
dependency (Table 3), which has been observed in our previous
studies of rare-earth metal alkyl cations.19 The J(YC) coupling
constants are also much larger for the monocationic compounds
Table 3 Selected NMR data for neutral, mono- and dicationic Y tri(tert-butoxy)silanolate complexes
Compound
d (1H) LnCH2 [ppm]
J(YH)/Hz
d (13C) LnCH2 [ppm]
J(YC)/Hz
d (89Y) [ppm]
Neutral yttrium complexes
1 (C6D6)
1 (thf-d8)
−0.33
3.4
3.1–3.4
39.5
22.3, 26.7
43.0
45.1, 38.6
863.2
—
−1.03, −1.00, −0.92
Monocationic yttrium complexes
6 (thf-d8)
13 (thf-d8)
14 (thf-d8)
15 (thf-d8)
−0.86
−0.79
−0.83
−0.88
3.4
3.4
3.4
3.4
29.6
30.1
30.2
—
47.6
46.0
46.3
—
—
—
666.2
—
Dicationic yttrium complexes
16 (C5D5N)
—
—
—
—
133.6
894 | Dalton Trans., 2006, 890–901
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
at room temperature,30 reaction of the similar dimeric species
[(AlMe2)2{l-OSi(1,3,5-C6H2Me3)3}(l-Me)] with one equiv. per
aluminium of [NMe2PhH]+[B(C6F5)4]− gave redistribution to
[AlMe2(NMe2Ph)2]+[B(C6F5)4]−, [Al{OSi(1,3,5-C6H2Me3)3}2Me]
and other minor products.31
We sought a rational synthesis of the monocationic species
[Lu{OSi(OtBu)3}2(thf)4]+[BPh4]− using [Lu(CH2SiMe3)2(thf)4]+-
[BPh4]− as a starting material19 in order to compare its NMR
data with those above. Thus reaction of [Lu(CH2SiMe3)2(thf)4]+-
[BPh4]− with two equiv. of HOSi(OtBu)3 in thf gave [Lu{OSi-
(OtBu)3}2(thf)4]+[BPh4]− as a microcrystalline solid in 84% yield.
The signals arising from the tert-butoxy methyl groups in both the
1
1H and 13C{ H} NMR spectra correspond exactly with one of the
two resonances observed for these groups in the spectra of 7.32
Dicationic complex
A thf solution of the yttrium alkyl 1 with two equiv. of
[NMe2PhH]+[BPh4]− gave the thf-soluble alkyl-free dication
Fig. 3 Molecular structure of 16 (ellipsoids drawn at the 50% probability
level, hydrogen atoms, borate anions and lattice THF omitted for clarity).
[Y{OSi(OtBu)3}(thf)6]2+[BPh4]− (16) in 65% yield. The dicationic
2
species 16 in thf-d8 gave two resonances arising from the tert-
butoxy groups of very similar chemical shift value (Dd = 0.01 ppm).
A single, sharp resonance was observed for the tert-butoxy groups
in C5D5N, whilst a single resonance was noted in the 29Si NMR
spectrum (thf-d8, 298 K: dSi − 103.3 ppm, d, J(YSi) = 9.9 Hz).
The 89Y NMR spectrum of 16 (C5D5N, 298 K: dY 133.6 ppm) gave
a single resonance highly shifted to lower frequency with respect
to the neutral and monocationic complexes. 16 reacted with one
equiv. of LiCH2SiMe3 in thf-d8 to give immediate formation of
a mixture of 6 and 1 at room temperature; addition of a second
equiv. of LiCH2SiMe3 yielded 1 (Scheme 4).33
O(3)–Si–O(1)–Y and O(4)–Si–O(1)–Y being 52.6(3)◦ and 64.5(3)◦
1
respectively. Terminal g -coordinated silanolate units are known
2
for both Sm and Gd, whilst there are no terminal g -coordinated
silanolate units reported for the rare-earth metals.8–11
Olefin hydrosilylation
Catalytic olefin hydrosilylation using rare-earth metal complexes
has recently been developed, although there are relatively few
active pre-catalysts free of Cp-ligands known.35 Whilst a com-
parative study of olefin hydroamination with neutral and cationic
rare-earth metal complexes has been reported,36 no such studies
concerning hydrosilylation have yet appeared in the literature.2
We found that a catalytic amount of 1 in C6D6 gave com-
plete hydrosilylation of 1-decene by PhSiH3 (40 equiv., 100%
linear product) at room temperature after 2 h. Very high initial
conversions are observed and the percentage conversion after
a given time varies little between 10 and 40 equiv. with the
same solvent volume (see ESI† for time–conversion plots).37
Neither catalytic amounts of 4 in C6D6, 6 in thf-d8, 13 in C6D6
nor 1/B(C6F5)3 in C6D6 gave measurable activities under the
same conditions. A catalytic quantity of 13 in C6D5Br gave
30% conversion after 20 h at room temperature (43 equiv,
100% linear product). Piers et al. have noted that, in the case
of [Sc{ArNC(Me)CHC(Me)NAr}(Me)(solv)]+[B(C6F5)4]− (Ar =
2,6-iPr2C6H3), C6H5Br coordinates much more weakly to the metal
centre than C6H6, which may explain the difference in reactivity
noted between these two solvents in hydrosilylation with 13 as
pre-catalyst.38
Scheme 4
Despite repeated attempts in a variety of solvents, it was not
possible to grow X-ray quality crystals of the alkyl cations 6–
15. However, X-ray crystallography of crystals of 16 (see Fig. 3)
grown at −30 ◦C in thf indicated that this compound is monomeric
in the crystalline state, adopting a slightly distorted pentagonal
bipyramidal geometry (O(1)–Y–O(10) = 178.72(6)◦). The Y–O(Si)
˚
bond length (2.0705(15) A, Table 2) is as expected somewhat
shorter than that found in the neutral congener 1; the Y–O(thf)
bond lengths in 16 are within the normal range reported for
Y–O(thf) bond lengths at cationic yttrium centres.34 The apical
Hydrosilylation of 40 equiv. of 1-decene catalysed by 3 required
6 days for 90% conversion. Hydrosilylation of styrene (20 equiv.)
with 1 in C6D6 gave 30% conversion to a mixture of regioisomers
after 18 h at room temperature, but failed to show significant
further conversion 2 days later. A deep yellow colouration was
observed during the course of this reaction, likely to arise from
metal–ligand charge transfer due to coordination of the aromatic
ring to the relatively open metal centre.39
1
silanolate functionality is g -coordinated (Y–O(tBu) = 4.7393(15)
˚
(O2), 4.2170(15) (O3), 4.4066(16) (O4) A, Fig. 3) and cants slightly
away from linearity (Y–O(1)–Si = 162.30(9)◦). This bend in the
Y–O(1)–Si axis and the pseudo mirror plane that bisects O(3)
and O(4) through O(2)–Si–O(1)–Y (torsion angle = 176.1(3)◦)
results in two inequivalent sets of tert-butoxy groups (O(4) =
O(3) (cis to Y) = O(2) (trans to Y)), the torsion angles involving
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 890–901 | 895
©

View Article Online
A series of reactions were carried out in order to probe the nature
of the active species derived from 1 and 13. 1 reacted completely
with 2 equiv. PhSiH3 after 3 h at 25 ◦C with co-formation
of PhSiH2(CH2SiMe3). Addition of 20 equiv. of 1-decene and
PhSiH3 to this solution initiated olefin hydrosilylation at a reduced
rate from that observed directly from the alkyl complex. The
formation of PhSiH2(CH2SiMe3) supports the hypothesis of a
hydride intermediate, however no Y–H signals were observed in
the 1H NMR spectrum.40
yttrium, terbium and lutetium (ALFA or Strem) were used as
received. All other chemicals were commercially available and used
after appropriate purification. NMR spectra were recorded on a
Varian Unity 500 spectrometer (1H, 500 MHz, 13C, 125.6 MHz,
11B, 160.3 MHz, 29Si, 99.2, 27Al, 130.2, 19F 470.1 MHz) or on
a Bruker DRX 400 spectrometer (89Y, 19.6 MHz). Chemical
1
shifts for H and 13C NMR spectra were referenced internally
using the residual solvent resonances and reported relative to
tetramethylsilane. 11B NMR spectra were referenced externally to a
1 M solution of NaBH4 in D2O. 19F NMR spectra were referenced
externally to CCl3F. 27Al spectra were referenced externally to a
1.1 M solution of Al(NO3)3 in D2O. 29Si spectra were referenced
externally to a 1% solution of SiMe4 in CDCl3. 89Y spectra were
referenced externally to a 1 M solution of YCl3 in D2O. Elemental
analyses were performed by the Microanalytical Laboratory of
the Johannes Gutenberg-University, Mainz, Germany. The results
show values low for carbon content, despite acceptable H and
Ln measurements. We ascribe this difficulty, also observed by
other workers, to the extreme sensitivity of the material and to
the possibility of metal carbide formation during combustion.43
Metal analysis was performed by complexometric titration and
gave satisfactory results for all compounds.44 The sample (20 to
30 mg) was dissolved in acetonitrile (2 mL) and titrated with
a 0.005 M aqueous solution of EDTA using xylenol orange as
indicator and a 1 M ammonium acetate buffer solution (20 mL).
The inactivity of the cationic species under most conditions
was also explored by NMR-scale reactions. 6 reacted completely
with 2 equiv. of PhSiH3 in thf-d8 after 24 h at 25 ◦C with
concomitant PhSiH2(CH2SiMe3) evolution, as did 13 in C6D6,
however neither any reactivity of these solutions with 1-decene,
nor any hydride resonances were observed. Addition of one
equiv. of B(C6F5)3 to a C6D6 solution of 1 gave rapid and
1
complete loss of all Y–CH2 resonances in the H NMR spec-
trum and yielded highly complicated 19F and 1H NMR spec-
tra. The yttrium tris(silanolate) species [Y{OSi(OtBu)3}3(thf)0.5]
reacted with 1.5 equiv. of B(C6F5)3 in C6D6 to give, according
to NMR spectroscopy, the “inorganic” contact-ion pair [Y{OSi-
(OtBu)3}2{l-OSi(OtBu)3}B(C6F5)3(thf)n]41 and [B(C6F5)3(thf)].42
Thus not only is the postulated alkyl cation [Y{OSi(OtBu)3}-
(CH2SiMe3)(C6D6)n]+[B(C6F5)3(CH2SiMe3)]− likely to rapidly de-
compose on formation at room temperature, but also the Y–
O(silanolate) bond is subject to attack by B(C6F5)3 in aromatic
solvents.
Syntheses
[Y{OSi(OtBu)3}(CH2SiMe3)2] (1).
A solution of HOSi-
Conclusions
(OtBu)3 (536 mg, 2025 lmol) in pentane (20 mL) was added
to a solution of [Y(CH2SiMe3)3(thf)2] (1002 mg, 2025 lmol) in
pentane (20 mL) at 25 ◦C and stirred for 1 h. The volatiles
were removed under reduced pressure and the resultant slightly
sticky, colourless solid dissolved in hexamethyldisiloxane (20 mL).
Removal of all volatiles under reduced pressure and drying in
vacuo resulted in a colourless, microcrystalline solid (925 mg, 1800
lmol, 90%). Crystals suitable for X-ray diffraction were grown
by slow evaporation to dryness of a concentrated hexamethyldis-
iloxane solution. Found: C, 43.94, 43.82; H, 9.62, 9.44; Y, 16.74.
C20H49O4Si3Y requires: C, 45.60; H, 9.38; Y, 16.88%. dH (C7D8, 298
K) −0.33 (d, J(YH) = 3.36 Hz, 2 × 2 H, YCH2SiMe3), 0.30 (s, 2 ×
9 H, YCH2SiMe3), 1.49 (s, 3 × 9 H, SiOC(CH3)3). dH (C7D8,
213 K) −0.27 (d, 2 × 1 H, J(HH) = 11.0 Hz, YCH2SiMe3),
−0.21 (d, 2 × 1 H, J(HH) = 11.0 Hz, YCH2SiMe3), 0.45 (s, 2 ×
9 H, YCH2SiMe3), 1.39 (s, 2 × 9 H, free SiOC(CH3)3), 1.54 (s,
1 × 9 H, coordinated SiOC(CH3)3). The J(YH) coupling was
not resolved at the low temperature limit. dH (thf-d8, 298 K)
−1.03 (d, 1.05 × 2 H, J(YH) = 3.1 Hz, YCH2SiMe3), −1.00
(d, 0.4 × 2 H, J(YH) = 3.4 Hz, YCH2SiMe3), −0.92 (d, 0.55 ×
2 H, J(YH) = 3.1 Hz, YCH2SiMe3), −0.14, −0.13 (major), −0.09
(s, 2 × 9 H, YCH2SiMe3), 1.30 (s, 1 × 9 H, SiOC(CH3)3), 1.32
(s, 2 × 9 H, SiOC(CH3)3). dH (thf-d8, 203 K) −1.09 (d, 1.5 ×
1 H, J(HH) = 11.3 Hz, YCH2SiMe3), −1.04 (d, 0.1 × 2 H,
J(YH) = 2.4 Hz, YCH2SiMe3), −1.00 (d, 1.5 × 1 H, J(HH) =
11.3 Hz, YCH2SiMe3), −0.92 (d, 0.4 × 2 H, J(YH) = 2.7 Hz,
YCH2SiMe3), −0.12, −0.07 (s, 2 × 9 H, YCH2SiMe3), 1.30 (s,
1 × 9 H, SiOC(CH3)3), 1.34 (s, 2 × 9 H, SiOC(CH3)3). dC (C6D6,
298 K) 4.7 (YCH2SiMe3), 31.8 (SiOC(CH3)3), 39.5 (d, J(YC) =
43.0 Hz, YCH2SiMe3), 77.0 (SiOC(CH3)3). dC (thf-d8, 298 K) 4.4,
We have demonstrated that stable, thf-free neutral rare-earth
2
metal dialkyl complexes [Ln{l,g -OSi(OtBu)3}(CH2SiMe3)2]2 can
be prepared from the appropriate rare-earth metal tris(alkyl)
complex with tri(tert-butoxy)silanol for Ln = Y, T b a n d L u .
We have also shown that monocationic, mono(alkyl) complexes
[Ln{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[A]− (Ln = Y, T b, L u ) a r e
isolable species with a variety of anions, although they are
contaminated by a small amount of the rearranged bis(alkyl)
and bis(silanolate) monocations. It is also possible to synthesize
an yttrium silanolate dication [Y{OSi(OtBu)3}(thf)6]2+[BPh4]−
,
2
reaction of which with two equiv. of trimethylsilylmethyl lithium
regenerates the neutral bis(alkyl) species. Whilst hydrosilyla-
2
tion of 1-decene with the neutral yttrium complex [Y{l,g -
OSi(OtBu)3}(CH2SiMe3)2]2 proceeds rapidly at room temperature
in C6D6 solution, the analogous lutetium complex gives a very
slow reaction under identical conditions. Hydrosilylation catalysis
using the monocationic yttrium complexes appears to depend on
the extent of the ion pair separation, as both the nature of the
solvent and the anion influenced the activity.
Experimental
General
All operations were performed under an inert atmosphere of
argon using standard Schlenk-line or glovebox techniques. thf and
toluene were distilled from sodium benzophenone ketyl. Pentane
and heptane were purified by distillation from sodium/triglyme
benzophenone ketyl. Anhydrous trichlorides of scandium,
896 | Dalton Trans., 2006, 890–901
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
4.6 (major), 4.8 (YCH2SiMe3), 22.3 (minor) (d, J(YC) = 45.1 Hz,
YCH2SiMe3), 26.7 (major) (d, J(YC) = 38.6 Hz, YCH2SiMe3),
32.1 (major), 32.2 (SiOC(CH3)3), 71.2, 71.3 (major) (SiOC(CH3)3).
dSi (C6D6, 298 K) −4.12, −4.16 (CH2SiMe3), −95.85 (YOSi). dY
(C6D6, 298 K) 863.2.
(d, J(YC) = 43.8 Hz, YCH2SiMe3), 32.4, 32.5 (SiOC(CH3)3), 71.2
(br) (12-crown-4), 71.4 (SiOC(CH3)3).
[Lu{OSi(OtBu)3}(CH2SiMe3)2(12-crown-4)]·12-crown-4
(5).
A solution of 12-crown-4 (52 mg, 294 lmol) in pentane (1 mL)
was added to a solution of 3 (90 mg, 147 lmol) in pentane
(2 mL) and vigorously shaken. After removal of trace colourless,
insoluble impurities by filtration, the clear, colourless solution
was cooled to −30 ◦C for 3 days. Removal of the supernatant
liquid and drying for 30 min at 298 K yielded the title compound
as colourless crystals (80 mg, 82 lmol, 56%). Found: Lu, 17.17.
C36H81LuO12Si3 requires: Lu, 18.13%. dH (C6D6, 298 K) −0.73 (d,
J(HH) = 11.7 Hz, 2 × 1 H, LuCH2SiMe3), −0.56 (d, J(HH) =
11.7 Hz LuCH2SiMe3), 0.39 (s, 2 × 9 H, LuCH2SiMe3), 1.53 (s,
3 × 9 H, SiOC(CH3)3), 3.49 (s, 16 H, 12-crown-4), 2.94, 3.80
(m, 16 H, 12-crown-4). dC (C6D6, 298 K) 5.2 (YCH2SiMe3), 32.0
(LuCH2SiMe3), 32.3 (SiOC(CH3)3), 68.1, 71.3, 71.5 (12-crown-4).
[Tb{OSi(OtBu)3}(CH2SiMe3)2] (2). A solution of HOSi-
(OtBu)3 (88 mg, 333 lmol) in pentane (10 mL) was added to a
solution of [Tb(CH2SiMe3)3(thf)2] (188 mg, 333 lmol) in pentane
(10 mL) at 25 ◦C and stirred for 30 min. The volatiles were removed
under reduced pressure and the resultant slightly sticky, colourless
solid dissolved in hexamethyldisiloxane (25 mL). Removal of
15 mL solvent under reduced pressure and recrystallisation at
−30 ◦C resulted in a colourless, crystalline solid (160 mg, 268 lmol,
81%). Found: Tb 26.00, C20H49O4Si3Tb requires: Tb, 26.63%.
[Lu{OSi(OtBu)3}(CH2SiMe3)2] (3). A solution of HOSi-
(OtBu)3 (520 mg, 1966 lmol) in pentane (15 mL) was added
to a solution of [Lu(CH2SiMe3)3(thf)2] (1142 mg, 1966 lmol)
in pentane (15 mL) at 25 ◦C and stirred for 30 min. The
volatiles were removed under reduced pressure and the resultant
slightly sticky, colourless solid dissolved in hexamethyldisiloxane
(25 mL). Removal of 15 mL solvent under reduced pressure and
recrystallisation at −30 ◦C resulted in a colourless, crystalline
solid (578 mg, 944 lmol, 48%). Found: C, 35.19; H, 7.59; Lu,
28.64. C20H49LuO4Si3 requires: C, 39.20; H, 8.06; Lu, 28.55%. dH
(C6D6, 298 K) −0.49 (s, 2 × 2 H, LuCH2SiMe3), 0.38 (s, 2 ×
9 H, LuCH2SiMe3), 1.49 (s, 3 × 9 H, SiOC(CH3)3). dH (thf-d8,
298 K) −1.16 (s, 1.35 × 2 H, LuCH2SiMe3), −1.15 (s, 0.45 ×
2 H, LuCH2SiMe3), −1.14 (s, 0.2 × 2 H, LuCH2SiMe3), −0.10
(major), −0.09 (s, 2 × 9 H, LuCH2SiMe3), 1.31 (s, 1 × 9 H,
SiOC(CH3)3), 1.32 (s, 2 × 9 H, SiOC(CH3)3). dC (C6D6, 298 K)
5.1 (LuCH2SiMe3), 32.0 (SiOC(CH3)3), 45.9 (LuCH2SiMe3). The
peak arising from SiOC(CH3)3 was not detected.
[Y{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[BPh4]− (6). A solution of
[NEt3H]+[BPh4]− (401 mg, 952 lmol) in thf (15 mL) was added
to a solution of 1 (501 mg, 952 lmol) in thf (15 mL) at 0 ◦C and
stirred for 1 h at the same temperature. The volatiles were removed
under reduced pressure and the resultant colourless solid dried for
2 h in vacuo to give a colourless, microcrystalline solid (901 mg,
860 lmol, 90%). Found: C, 62.13, 62.01; H, 8.69, 8.91; Y, 8.30.
C56H90BO8Si2Y requires: C, 64.23; H, 8.66; Y, 8.49%. dH (thf-d8,
298 K) −0.86 (d, J(YH) = 3.4 Hz, 1.25 × 2 H, YCH2SiMe3), −0.78
(d, J(YH) = 3.1 Hz, 0.75 × 2 H, YCH2SiMe3), −0.09, −0.06 (s,
9 H, YCH2SiMe3), 1.32, 1.33 (s, 3 × 9 H, SiOC(CH3)3), 6.73 (t,
J(HH) = 7.2 Hz, 4 H, 4-Ph), 6.86 (m, 8 H, 3-Ph), 7.27 (s (br), 8 H,
2-Ph). dH (CD2Cl2, 298 K) −0.86 (d, J(YH) = 3.4 Hz, 1.25 × 2 H,
YCH2SiMe3), −0.10 (s, 9 H, YCH2SiMe3), 1.29, 1.31 (s, 3 × 9 H,
SiOC(CH3)3), 1.97 (s, 4 × 4 H, b-thf), 3.99 (s, 4 × 4 H, a-thf), 6.87
(t, J(HH) = 7.0 Hz, 4 × 1 H, 4-Ph), 7.02 (m, 4 × 2 H, 3-Ph), 7.30
(m (br), 4 × 2 H, 2-Ph). dH (CD2Cl2, 263 K) −0.88 (d, J(YH) =
3.4 Hz, 1.25 × 2 H, YCH2SiMe3), −0.77 (d, J(YH) = 3.1 Hz,
0.75 × 2 H, YCH2SiMe3), −0.10, −0.06 (s, 9 H, YCH2SiMe3),
1.28, 1.30 (s, 3 × 9 H, SiOC(CH3)3), 1.99 (s, 4 × 4 H, b-thf), 4.01
(s, 4 × 4 H, a-thf), 6.89 (t, J(HH) = 7.2 Hz, 4 × 1 H, 4-Ph), 7.04
(m, 4 × 2 H, 3-Ph), 7.30 (m (br), 4 × 2 H, 2-Ph). dC (thf-d8, 298 K)
3.9, 4.1 (YCH2SiCH3), 29.6 (d, J(YC) = 47.6 Hz, YCH2SiCH3),
32.0, 32.1 (SiOC(CH3)3), 72.0, 72.1 (SiOC(CH3)3), 121.6 (Ph-4),
125.5 (Ph-3), 136.9 (Ph-2), 164.9 (q, J(BC) = 49.6 Hz, Ph-1). dB
(thf-d8, 298 K) −6.6.
[Y{OSi(OtBu)3}(CH2SiMe3)2(12-crown-4)]·12-crown-4 (4).
A
solution of 12-crown-4 (200 mg, 1140 lmol) in pentane (5 mL)
was added to a solution of 1 (300 mg, 570 lmol) in pentane (5 mL)
and vigorously shaken. After removal of trace colourless, insoluble
impurities by filtration, the clear, colourless solution was cooled
overnight to −30 ◦C. Removal of the supernatant liquid and drying
for 30 min at 298 K yielded the title compound as colourless
crystals (200 mg, 228 lmol, 80%). Found: C, 45.78; H, 8.68; Y,
10.03. C36H81O12Si3Y requires: C, 49.18; H, 9.29; Y, 10.11%. dH
(CD2Cl2, 298 K) −1.04 (dd, J(HH) = 11.2 Hz, J(YH) = 3.2 Hz,
2 × 1 H, YCH2SiMe3), −0.88 (dd, J(HH) = 11.2 Hz, J(YH) =
3.2 Hz, 2 × 1 H, YCH2SiMe3), −0.12 (s, 2 × 9 H, YCH2SiMe3),
1.32 (s, 3 × 9 H, SiOC(CH3)3), 3.62 (s, 16 H, 12-crown-4), 3.72,
4.22 (m, 16 H, 12-crown-4). dH (C7D8, 298 K) −0.64 (dd, J(HH) =
11.2 Hz, J(YH) = 3.2 Hz, 2 × 1 H, YCH2SiMe3), −0.47 (dd,
J(HH) = 11.2 Hz, J(YH) = 3.2 Hz, 2 × 1 H, YCH2SiMe3), 0.32
(s, 2 × 9 H, YCH2SiMe3), 1.53 (s, 3 × 9 H, SiOC(CH3)3), 3.44 (s,
16 H, 12-crown-4), 2.88, 3.73 (m, 16 H, 12-crown-4). dH (thf-d8,
298 K) −0.95 (d, 1.7 × 2 H, J(YH) = 2.9 Hz, YCH2SiMe3), −0.79
(d, 0.3 × 2 H, J(YH) = 2.9 Hz, YCH2SiMe3), −0.12 (s, 1.7 × 9 H,
YCH2SiMe3), −0.12 (s, 0.3 × 9 H, YCH2SiMe3), 1.32 (s, 1 × 9 H,
SiOC(CH3)3), 1.34 (s, 2 × 9 H, SiOC(CH3)3), 3.44 (s (br), 32 H,
12-crown-4). dC (C6D6, 298 K) 5.2 (YCH2SiMe3), 27.4 (d, J(YC) =
40.1 Hz, YCH2SiMe3), 32.4 (SiOC(CH3)3), 67.1, 71.1 (12-crown-
4), 71.2 (SiOC(CH3)3). dC (thf-d8, 298 K) 5.0 (YCH2SiMe3), 26.6
[Tb{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[BPh4]− (7). A solution
of [NEt3H]+[BPh4]− (113 mg, 268 lmol) in thf (15 mL) was added
to a solution of 2 (160 mg, 268 lmol) in thf (15 mL) at −78 ◦C and
stirred for 30 min at 0 ◦C and overnight at room temperature. The
volatiles were removed under reduced pressure and the resultant
colourless, waxy solid dried for 30 min in vacuo and washed with
pentane (2 × 15 mL) to give a colourless, microcrystalline solid
(200 mg, 179 lmol, 67%). Found: Tb, 14.01, C56H90BO8Si2Tb
requires: Tb, 14.23%.
[Lu{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[BPh4]− (8). A solution
of [NEt3H]+[BPh4]− (379 mg, 898 lmol) in thf (20 mL) was
added to a solution of 3 (550 mg, 898 lmol) in thf (20 mL) at
0
◦C and stirred for 1 h at the same temperature. The volatiles
were removed under reduced pressure and the resultant colourless
solid dried for 2 h in vacuo to give a colourless, microcrystalline
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 890–901 | 897
©

View Article Online
solid (810 mg, 715 lmol, 80%). Found: C, 57.12; H, 8.56; Lu,
15.25. C56H90BLuO8Si2 requires: C, 59.35; H, 8.00; Lu, 15.44%.
dH (CD2Cl2, 298 K) −1.00 (major), −0.97 (s, 2 H, LuCH2SiMe3),
−0.06 (major), −0.04 (s, 9 H, LuCH2SiMe3), 1.29, 1.32 (s, 3 ×
9 H, SiOC(CH3)3), 1.97 (s, 4 × 4 H, b-thf), 3.99 (s, 4 × 4 H, a-
thf), 6.87 (t, J(HH) = 7.0 Hz, 4 × 1 H, 4-Ph), 7.02 (m, 4 × 2 H,
3-Ph), 7.30 (m (br), 4 × 2 H, 2-Ph). dC (CD2Cl2, 298 K) 4.0,
4.3 (major) (LuCH2SiCH3), 25.7 (b-thf), 32.0, 32.1 (SiOC(CH3)3),
32.8 (LuCH2SiCH3), 71.7 (a-thf), 72.1, 72.2 (SiOC(CH3)3), 122.1
(Ph-4), 126.0 (Ph-3), 136.4 (Ph-2), 164.3 (q, J(BC) = 50.0 Hz,
Ph-1). dB (thf-d8, 298 K) −6.6.
(d, J(YH) = 3.1 Hz, 0.7 × 2 H, YCH2SiMe3), −0.89 (d, J(YH) =
3.4 Hz, 0.3 × 2 H, YCH2SiMe3), −0.12 (major), −0.09 (minor)
(s, 9 H, YCH2SiMe3), 1.28, 1.30 (s, 3 × 9 H, SiOC(CH3)3), 3.54,
3.94 (m, 0.7 × 20 H, 15-crown-5), 3.61, 4.15 (m, 0.3 × 20 H,
15-crown-5), 3.45, 3.75 (m, 0.05 × 20 H, 15-crown-5), 6.93 (t,
J(HH) = 7.3 Hz, 4 × 1 H, 4-Ph), 7.07 (m, 4 × 2 H, 3-Ph), 7.37 (m
(br), 4 × 2 H, 2-Ph). dC (CD2Cl2, 298 K) 4.1 (YCH2SiCH3), 26.3
(d, J(YC) = 45.5 Hz, YCH2SiCH3), 32.0 (SiOC(CH3)3), 69.2,
69.4, 69.6, 71.6, 71.7 (15-crown-5, SiOC(CH3)3), 122.4 (Ph-4),
126.2 (Ph-3), 136.3 (Ph-2), 164.2 (q, J(BC) = 49.7 Hz, Ph-1). dB
(CD2Cl2, 298 K) −6.7.
[Y{OSi(OtBu)3}(CH2SiMe3)(12-crown-4)(thf)]+[BPh4]− (9).
A
[Lu{OSi(OtBu)3}(CH2SiMe3)(15-crown-5)]+[BPh4]− (12).
A
solution of 12-crown-4 (39 mg, 220 lmol) in heptane (1 mL) was
added to a suspension of 5 (202 mg, 193 lmol) in heptane (10 mL)
and stirred rapidly for 1 h at room temperature. The supernatant
liquid was removed and the resultant colourless microcrystalline
solid dried in vacuo for 1 h to give 6 (166 mg, 170 lmol, 89%).
Found: C, 61.18, 60.97; H, 8.59, 8.45; Y, 8.81. C52H82BO9Si2Y
requires: C, 62.02; H, 8.21; Y, 8.83%. dH (CD2Cl2, 298 K) −0.98
(d, J(YH) = 2.8 Hz, 0.88 × 2 H, YCH2SiMe3), −0.86 (d, J(YH) =
3.1 Hz, 0.12 × 2 H, YCH2SiMe3), −0.13 (major), −0.12 (minor)
(s, 9 H, YCH2SiMe3), 1.27, 1.29 (s, 3 × 9 H, SiOC(CH3)3), 1.97
(s, 1 × 4 H, b-thf), 3.32, 3.74 (m, 0.88 × 16 H, 12-crown-4), 3.38,
3.96 (m, 0.16 × 16 H, 12-crown-4), 3.12, 3.66 (m, 0.02 × 16 H,
12-crown-4), 4.07 (s, 1 × 4 H, a-thf), 6.93 (t, J(HH) = 7.3 Hz, 4
H, 4-Ph), 7.08 (m, 4 × 2 H, 3-Ph), 7.38 (m (br), 4 × 2 H, 2-Ph). dC
(CD2Cl2, 298 K) 3.9 (YCH2SiCH3), 25.7 (b-thf), 27.8 (d, J(YC) =
44.6 Hz, YCH2SiCH3), 31.8 (SiOC(CH3)3), 67.7 (a-thf), 68.0, 70.0,
71.5, 71.6, 71.6 (12-crown-4, SiOC(CH3)3), 122.4 (Ph-4), 126.1
(Ph-3), 136.3 (Ph-2), 164.3 (q, J(BC) = 49.7 Hz, Ph-1). dB (CD2Cl2,
298 K) −6.7.
solution of 15-crown-5 (41 mg, 186 lmol) in heptane (1 mL) was
added to a suspension of 7 (204 mg, 180 lmol) in heptane (10 mL)
and stirred rapidly for 1 h at room temperature. The supernatant
liquid was removed and the resultant colourless microcrystalline
solid washed with a 1 : 5 thf : heptane mixture and dried in vacuo
for 1 h (143 mg, 134 lmol, 72%). Found: C, 55.57; H, 8.47; Lu,
16.32. C50H78BLuO9Si2 requires: C, 56.38; H, 7.38; Lu, 16.43%.
dH (CD2Cl2, 298 K) −1.18, −1.11 (major) (s, 2 H, LuCH2SiMe3),
−0.12 (major), −0.09 (s, 9 H, LuCH2SiMe3), 1.28, 1.30 (s, 3 × 9 H,
SiOC(CH3)3), 3.54, 3.95 (m, 0.62 × 20 H, 15-crown-5), 3.61, 4.15
(m, 0.26 × 20 H, 15-crown-5), 3.45, 3.75 (m, 0.12 × 20 H, 15-
crown-5), 6.92 (t, J(HH) = 7.0 Hz, 4 × 1 H, 4-Ph), 7.06 (m, 4 ×
2 H, 3-Ph), 7.36 (m (br), 4 × 2 H, 2-Ph). dC (CD2Cl2, 298 K)
4.3 (LuCH2SiCH3), 29.1 (major), 36.8 (LuCH2SiCH3), 31.9, 32.0
(SiOC(CH3)3), 69.2, 69.5, 69.7, 69.9, 70.5 (15-crown-5), 71.6, 71.7
(SiOC(CH3)3), 122.4 (Ph-4), 126.1 (Ph-3), 136.3 (Ph-2), 164.3 (q,
J(BC) = 49.0 Hz, Ph-1). dB (thf-d8, 298 K) −6.6.
[Y{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[B(C6F5)4]− (13). A solu-
tion of 1 in thf (30 mL) was added to [NMe2PhH]+[B(C6F5)4]−
(200 mg, 379 lmol) and stirred for 10 min at this temperature,
30 min at 0 ◦C and 15 min at room temperature. The volatiles were
removed under reduced pressure and the resultant pale yellow oil
dried for 30 min in vacuo. Pentane was added and the resultant
oily dispersion stirred for 30 min at room temperature, cooled
to −78 ◦C, at which temperature a colourless microcrystalline
solid was observed. Removal of the liquid phase via cannula and
drying of the solid in vacuo gave 10 as a colourless, microcrystalline
solid (440 mg, 313 lmol, 83%). Found: C, 44.65; H, 3.89; Y, 6.54.
C56H70BF20O8Si2Y requires: C, 47.80; H, 5.01; Y, 6.32%. dH (C6D6,
298 K after 18 h at 298 K) −0.86 (d, J(YH) = 3.4 Hz, 1.5 × 2 H,
YCH2SiMe3), −0.80 (d, J(YH) = 3.1 Hz, 0.5 × 2 H, YCH2SiMe3),
0.16, 0.18 (s, 9 H, YCH2SiMe3), 1.31 (s, 3 × 9 H, SiOC(CH3)3),
1.51 (s, 4 × 4 H, b-thf), 3.66 (s, 4 × 4 H, a-thf). dH (thf-d8,
298 K) −0.79 (d, J(YH) = 3.4 Hz, 1.5 × 2 H, YCH2SiMe3),
−0.69 (d, J(YH) = 3.4 Hz, 0.5 × 2 H, YCH2SiMe3), 0.09, 0.02
(s, 9 H, YCH2SiMe3), 1.32, 1.33 (s, 3 × 9 H, SiOC(CH3)3). dC
(thf-d8, 298 K) 3.8, 4.0 (major) (YCH2SiCH3), 30.1 (d, J(YC) =
46.0 Hz, YCH2SiCH3), 31.8, 31.9, 32.0 (SiOC(CH3)3), 71.7, 72.1,
72.2 (SiOC(CH3)3), 125.0 (m (br), C6F5-1), 137.9 (m, C6F5-3, C6F5-
[Lu{OSi(OtBu)3}(CH2SiMe3)(12-crown-4)(thf)]+[BPh4]− (10).
A solution of 12-crown-4 (31 mg, 178 lmol) in heptane (1 mL) was
added to a suspension of 7 (202 mg, 178 lmol) in heptane (10 mL)
and stirred rapidly for 1 h at room temperature. The supernatant
liquid was removed and the resultant colourless microcrystalline
solid washed with a 1 : 5 thf : heptane mixture and dried in vacuo
for 1 h (148 mg, 145 lmol, 81%). Found: C, 53.23; H, 6.86; Lu,
15.71. C52H82BLuO9Si2 requires: C, 57.13; H, 7.56; Lu, 16.01%. dH
(CD2Cl2, 298 K) −1.14 (br, major), −1.10 (s, 2 H, LuCH2SiMe3),
−0.13 (major), −0.11 (s, 9 H, LuCH2SiMe3), 1.26, 1.28 (s, 3 ×
9 H, SiOC(CH3)3), 1.97 (s, 4 H, b-thf), 3.05–4.30 (m, 20 H, 12-
crown-4 and thf), 6.93 (t, J(HH) = 7.2 Hz, 4 × 1 H, 4-Ph), 7.07
(m, 4 × 2 H, 3-Ph), 7.37 (m (br), 4 × 2 H, 2-Ph). dC (thf-d8, 298 K)
4.2 (LuCH2SiCH3), 25.7 (a-thf), 30.9 (LuCH2SiCH3), 31.8, 31.9
(SiOC(CH3)3), 67.1, 67.9, 68.1, 68.2, 70.1 (12-crown-4, b-thf), 71.7,
71.8 (SiOC(CH3)3), 121.6 (Ph-4), 125.5 (Ph-3), 136.9 (Ph-2), 164.9
(q, J(BC) = 49.0 Hz, Ph-1). dB (thf-d8, 298 K) −6.6.
[Y{OSi(OtBu)3}(CH2SiMe3)(15-crown-5)]+[BPh4]−
(11). A
solution of 15-crown-5 (49 mg, 220 lmol) in heptane (1 mL) was
added to a suspension of 5 (201 mg, 178 lmol) in heptane (10 mL)
and stirred rapidly for 1 h at room temperature. The supernatant
liquid was removed and the resultant colourless microcrystalline
solid dried in vacuo for 1 h to give 8 (142 mg, 140 lmol, 76%).
Trace thf was noted in the 1H NMR spectrum (0.25 equiv.).
Found: C, 60.32, 60.33; H, 8.50, 8.42; Y, 8.87. C50H78BO9Si2Y
requires: C, 61.34; H, 8.03; Y, 9.08%. dH (CD2Cl2, 298 K) −0.93
1
4), 148.9 (d, JCF = 243.4 Hz, C6F5-2). dB (thf-d8, 298 K) −16.7.
dF (C6D6, 298 K after 18 h at 298 K) −166.2, −162.1, −131.6.
dF (thf-d8, 298 K) −168.5, −165.0, −132.8. dSi (thf-d8, 298 K)
−0.2 (CH2SiMe3), −99.8 (d, J(YSi) = 9.7 Hz, SiOC(CH3)3), 100.2
(SiOC(CH3)3).
898 | Dalton Trans., 2006, 890–901
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
1H NMR spectra with relatively short delay and acquisition times
(typically d1 = 0.2 s, nt = 32) were taken at regular intervals and
the degree of conversion calculated from the relative intensities of
the product and starting material resonances.
[Y{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[Al(CH2SiMe3)4]− (14).
A
solution of Al(CH2SiMe3)3 (241 mg, 835 lmol) in thf (0.5 mL)
was added to a thf solution (2 mL) of 1 (440 mg, 835 lmol)
at room temperature and left for 24 h at this temperature. The
volatiles were removed from the resultant pale green solution and
the resultant pale green/yellow oil dried for 1 h in vacuo. Due to
the difficulty of handling this material, the yield and elemental
analysis were not determined. dH (thf-d8, 298 K) −1.29 (m (br),
4 × 2 H, AlCH2SiMe3), −0.83 (d, J(YH) = 3.4 Hz, 1.75 ×
2 H, YCH2SiMe3), −0.74 (d, J(YH) = 3.1 Hz, 0.25 × 2 H,
YCH2SiMe3), −0.17 (s, 4 × 9 H, AlCH2SiMe3), −0.13, −0.08
(s, 9 H, YCH2SiMe3), 1.27, 1.29 (s, 3 × 9 H, SiOC(CH3)3). dC
(thf-d8, 298 K) 1.7 (sextet, AlCH2SiMe3, J(AlC) = 63.0 Hz), 2.8,
3.9, 4.0 (AlCH2SiMe3, YCH2SiMe3), 30.2 (d, J(YC) = 46.3 Hz,
YCH2SiCH3), 31.9, 32.0 (SiOC(CH3)3), 72.0, 72.1 (SiOC(CH3)3).
dAl (thf-d8, 298 K) 150.1. dSi (thf-d8, 298 K) −0.2 (CH2SiMe3),
−99.6 (d, J(YSi) = 10.6 Hz, SiOC(CH3)3), 100.1 (d, J(YSi) =
9.6 Hz, SiOC(CH3)3). dY (thf-d8, 298 K) 666.2.
Crystallography
X-Ray diffraction data were collected on a Bruker CCD platform
diffractometer equipped with a CCD detector. The SMART
program package was used to determine the unit-cell parameters
and for data collection; the raw frame data was processed
using SAINT and SADABS to yield the reflection data file.45
Subsequent calculations were carried out using the SHELXS and
SHELXL programs.46 Analytical scattering factors for neutral
atoms were used throughout the analysis.47 The structures of 1,
5 and 16 were solved by direct methods and Fourier difference
analyses. Hydrogen atoms were included at calculated positions.
The structure of [Sc{OSi(OtBu)3}(CH2SiMe3)2],15† was solved by
isotypic replacement using the coordinates of 1.
[Y{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[BPh3(CH2SiMe3)]− (15).
thf-d8 was added to a mixture of 1 (50 mg, 95 lmol) and BPh3
(23 mg, 95 lmol) at room temperature. Spectra were measured
after standing for 30 min at room temperature. dH (thf-d8, 298
K) −0.88 (d, J(YH) = 3.4 Hz, 1 × 2 H, YCH2SiMe3), −0.80
(d, J(YH) = 3.1 Hz, 1 × 2 H, YCH2SiMe3), −0.48 (s, 1 × 9 H,
BCH2SiMe3), −0.09, −0.06 (s, 9 H, YCH2SiMe3), 0.18 (q,
J(BH) = 5.0 Hz, 1 × 2 H, BCH2SiMe3), 1.33, 1.32 (s, 3 × 9 H,
SiOC(CH3)3), 6.66 (t, J(HH) = 7.2 Hz, 4 × 1 H, 4-Ph), 6.83 (m,
CCDC reference numbers 282721–282724.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b512285f
Acknowledgements
We would like to thank the Deutsche Forschungsgemeinschaft
(DFG) and the Fonds der Chemischen Industrie for financial
support, Prof. Dr U. Englert for X-ray measurements, Dr
B. Mathiasch and Mr T. Gossen for NMR measurements and
Mr I. Peckermann and Mr H.-B. Mieskes for synthetic work.
◦
4 × 2 H, 3-Ph), 7.37 (m (br), 4 × 2 H, 2-Ph). dB (thf-d8, 25 C)
−10.4 (major), 73.3 (minor).
[Y{OSi(OtBu)3}(thf)6]2+[BPh4]− (16). thf (20 mL) was added
2
to a mixture of 1 (263 mg, 500 lmol) and [NMe2PhH]+[BPh4]−
(552 mg, 1250 lmol) at −78 ◦C, warmed slowly to room
temperature and stirred overnight. The volatiles were removed
under reduced pressure and the resultant pale yellow oil dried for
30 min in vacuo. This solid was washed with diethyl ether (20 mL)
and heptane (20 mL) and dried for 1 h in vacuo to yield a fine,
off-white powder (460 mg, 323 lmol, 65%). Single crystals were
grown from a highly concentrated thf solution at −30 ◦C. Found:
C, 63.76; H, 7.12; Y, 6.52. C84H115B2O10SiY requires: C, 70.88;
H, 8.14; Y, 6.25%. dH (thf-d8, 298 K) 1.31, 1.32 (s, 3 × 9 H,
SiOC(CH3)3), 6.76 (t, J(HH) = 7.0 Hz, 8 × 1 H, 4-Ph), 6.90
(m, 8 × 2 H, 3-Ph), 7.29 (m (br), 8 × 2 H, 2-Ph). dH (C5D5N,
298 K) 1.52 (s, 3 × 9 H, SiOC(CH3)3), 1.62 (m, 6 × 4 H, b-thf),
3.66 (s, 6 × 4 H, a-thf), 7.10 (t, J(HH) = 7.0 Hz, 8 × 1 H, 4-Ph),
7.26 (m, 8 × 2 H, 3-Ph), 8.05 (m (br), 8 × 2 H, 2-Ph). dC (thf-d8,
298 K) 32.2, 32.3 (SiOC(CH3)3), 73.4, 72.2 (SiOC(CH3)3), 121.9
(Ph-4), 125.7 (Ph-3), 136.9 (Ph-2), 164.9 (q, J(BC) = 49.8 Hz, Ph-
1). dC (C5D5N, 298 K) 26.0 (b-thf), 32.2, 32.4 (SiOC(CH3)3), 68.0
(a-thf), 72.4, 73.2 (SiOC(CH3)3), 122.5 (Ph-4), 126.3 (Ph-3), 137.3
(Ph-2), 164.0 (q, J(BC) = 48.7 Hz, Ph-1). dB (thf-d8, 298 K) −6.6.
dB (C5D5N, 298 K) −4.25. dSi (thf-d8, 298 K) −103.3 (d, J(YSi) =
9.9 Hz, YOSi). dY (C5D5N, 298 K) 133.6.
References and notes
1 S. Arndt and J. Okuda, Chem. Rev., 2002, 102, 1953.
2 S. Arndt and J. Okuda, Adv. Synth. Catal., 2005, 347, 339.
3 (a) S. Arndt, T. P. Spaniol and J. Okuda, Angew. Chem., Int. Ed., 2003,
42, 5075; (b) B. D. Ward, S. Bellemin-Laponnaz and L. H. Gade, Angew.
Chem., Int. Ed., 2005, 44, 1668.
4 (a) W. E. Piers and D. J. H. Emslie, Coord. Chem. Rev., 2002, 233, 131;
(b) F. T. Edelmann, D. M. M. Freckmann and H. Schumann, Chem.
Rev., 2002, 102, 1851; (c) J. Gromada, J. F. Carpentier and A. Mortreux,
Coord. Chem. Rev., 2004, 248, 397.
5 (a) F. J. Feher, J. Am. Chem. Soc., 1986, 108, 3850; (b) W. A. Hermann,
R. Anwander and V. Dufaud, Angew. Chem., Int. Ed. Engl., 1994, 33,
1285; (c) R. Murugavel, A. Voigt, M. G. Walawalkar and H. W. Roesky,
Chem. Rev., 1996, 96, 2205; (d) J. Annand, H. C. Aspinall and A. Steiner,
Inorg. Chem., 1999, 38, 3941; (e) L. King and A. C. Sullivan, Coord.
Chem. Rev., 1999, 189, 19; (f) H. C. Aspinall and J. Annand, J. Chem.
Soc., Dalton Trans., 2000, 1867; (g) G. G. Hlatky, Chem. Rev., 2000,
100, 1347; (h) H. C. L. Abbenhuis, Chem. Eur. J., 2000, 6, 25; (i) V.
Lorenz, A. Fischer, S. Giessman, J. W. Gilje, Y. K. Gunko, K. Jacob
and F. T. Edelmann, Coord. Chem. Rev., 2000, 206–207, 321; (j) Y. K.
Gunko, R. Reilly, F. T. Edelmann and H. G. Schmidt, Angew. Chem.,
Int. Ed., 2001, 40, 1279; (k) V. Lorenz, A. Fischer and F. T. Edelmann,
J. Organomet. Chem., 2002, 647, 245; (l) R. Duchateau, Chem. Rev.,
2002, 102, 3525; (m) C. Cope´ret, M. Chabanas, R. P. Saint-Arroman
and J.-M. Basset, Angew. Chem., Int. Ed., 2003, 42, 156; (n) R. W. J. M.
Hanssen, R. A. van Santen and H. C. L. Abbenhuis, Eur. J. Inorg.
Chem., 2004, 675.
6 (a) K. W. Terry and T. D. Tilley, Chem. Mater., 1991, 3, 1001; (b) K. W.
Terry, P. K. Ganzel and T. D. Tilley, Chem. Mater., 1992, 4, 1290;
(c) R. Murugavel, V. Chandrasekhar and H. W. Roesky, Acc. Chem.
Res., 1996, 29, 183; (d) R. Murugavel, M. Bhattachargee and H. W.
Roesky, Appl. Organomet. Chem., 1997, 13, 227; (e) J. Jarupatrakorn,
M. P. Coles and T. D. Tilley, Chem. Mater., 2005, 17, 1818.
Hydrosilylation
In a typical experiment, an NMR tube was charged with 0.03 mmol
pre-catalyst, 0.30–1.20 mmol PhSiH3, 0.30–1.20 mmol olefin and
0.5 mL C6D6. In order to determine the progress of the reaction,
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 890–901 | 899
©

View Article Online
7 (a) Y. Abe and I. Kijima, Bull. Chem. Soc. Jpn., 1969, 42, 1148; (b) Y.
Abe and I. Kijima, Bull. Chem. Soc. Jpn., 1970, 43, 466; (c) I. Kijima,
T. Yamamoto and Y. Abe, Bull. Chem. Soc. Jpn., 1971, 44, 3193; (d) Y.
Abe, K. Hayama and I. Kijima, Bull. Chem. Soc. Jpn., 1972, 45, 1258.
8 A. Fischbach, M. G. Klimpel, M. Widenmeyer, E. Herdtweck,
W. Scherer and R. Anwander, Angew. Chem., Int. Ed., 2004, 43,
2234.
9 A. Fischbach, G. Eickerling, W. Scherer, E. Herdtweck and R.
Anwander, Z. Naturforsch., Teil B, 2004, 1353.
10 (a) S. Ko, Y. Wakatsuki and M. Nishiura (Institute of Physical and
Chemical Research, Japan), Jpn. Pat., 11 255 776 A2, 1999S. Ko, Y.
Wakatsuki and M. Nishiura, Chem. Abstr., 1999, 131, 229166; (b) M.
Nishiura, Z. Hou, T. Imamoto and Y. Wakatsuki, Kidorui, 1998, 32,
294.
(f) [Lu(CH2SiMe3)2(12-crown-4)(thf)]+[B(CH2SiMe3)Ph3]−: Lu–C =
˚
2.340(2), 2.354(2) A, see: S. Arndt, T. P. Spaniol and J. Okuda,
Chem. Commun., 2002, 896; (g) [Lu(CH2SiMe3)3(12-crown-4)]: Lu–C =
5
1
˚
2.36(1) − 2.40(1) A, see ref. 15; (h) [Ln{g :g -C5Me4SiMe2(OC4H3-
˚
2)}(CH2SiMe3)2(thf)]: Lu–C = 2.374(4), 2.381(4) A, see: S. Arndt, T. P.
Spaniol and J. Okuda, Organometallics, 2003, 22, 775.
25 The waxy off-white solid tentatively assigned as the 15-crown-5
analogue of 4, synthesized in an analogous manner, gave rise to very
similar resonances to 4 in the 1H NMR spectrum for the alkyl and
silanolate groups (C6D6), however the crown ether region was rather
poorly resolved. Selected NMR data: dH (C6D6, 298 K) −0.58 (dd,
J(HH) = 11.0 Hz, J(YH) = 3.2 Hz, 2 × 1 H, YCH2SiMe3), −0.48
(dd, J(HH) = 11.0 Hz, J(YH) = 3.2 Hz, 2 × 1 H, YCH2SiMe3), 0.42
(s, 2 × 9 H, YCH2SiMe3), 1.55 (s, 3 × 9 H, SiOC(CH3)3), 3.15, 3.49,
3.66 (s (br), 20 H, 15-crown-5). dC (C6D6, 298 K) 5.1 (YCH2SiMe3),
28.8 (d, J(YC) = 40.7 Hz, YCH2SiMe3), 32.3 (SiOC(CH3)3), 69.6 ((br),
15-crown-5), 71.4 (SiOC(CH3)3).
11 (a) Z. Hou and Y. Wakatsuki, J. Organomet. Chem., 2002, 647, 61;
(b) M. Nishiura, Z. Hou and Y. Wakatsuki, Organometallics, 2004, 23,
1359.
12 (a) R. Duchateau, R. A. van Santen and G. P. A. Yap, Organometallics,
2000, 19, 809; (b) M. D. Skowronska-Ptasinska, R. Duchateau, R. A.
van Santen and G. P. A. Yap, Organometallics, 2001, 20, 3519; (c) G.
Jimenez, P. Royo, T. Cuenca and M. Galakhov, Organometallics, 2001,
20, 5237; (d) V. Amo, R. Andre´s, E. de Jesu´s, F. J. de la Mata, J. C. Flores,
R. Go´mez, M. P. Go´mez-Sal and J. F. C. Turner, Organometallics, 2005,
24, 2331.
13 [Ln(CH2SiMe3)3(thf)n] (n = 2 for Ln = Lu, Sc; n = 2, 3 for Ln = Y, T b )
were prepared according to literature procedures: (a) M. F. Lappert
and R. Pearce, J. Chem. Soc., Chem. Commun., 1973, 126; (b) W. J.
Evans, J. C. Brady and J. W. Ziller, J. Am. Chem. Soc., 2001, 123, 7711;
(c) H. Schumann, D. M. M. Freckmann and S. Dechert, Z. Anorg. Allg.
Chem., 2002, 628, 2422.
26 Complexometric titration gave results for all cationic species consistent
with the alkyl-silanolate formulation, although simple rearrangement
does not affect the elemental composition.
27 (a) R. Duchateau, U. Cremer, R. J. Harmsen, S. I. Mohamud, H. C. L.
Abbenhuis, R. A. van Santen, A. Meetsma, S. K.-H. Thiele, M. F. H.
van Tol and M. Krankenburg, Organometallics, 1999, 18, 5447; (b) R.
Duchateau, H. C. L. Abbenhuis, R. A. van Santen, S. K.-H. Thiele and
M. F. H. van Tol, Organometallics, 1998, 17, 5222.
28 The synthesis of [Y{OSi(OtBu)3}3] from [Y{N(SiMe3)2}3] and
HOSi(OtBu)3 has been reported: R. Anwander, Top. Organomet.
Chem., 1999, 2, 1. We found that the use of [Y(CH2SiMe3)3(thf)2]
under similar conditions led to the inclusion of a small amount of
thf: [Y{OSi(OtBu)3}3(thf)n] (n = 0.5–0.6) after recrystallisation from
pentane.
14 Synthesis of the scandium analogue was hampered by the formation
of various by-products tentatively assigned by NMR spectroscopy
and complexometric titration as [Sc{OSi(OtBu)3}2(CH2SiMe3)] and
[Sc{OSi(OtBu)3}3]. The successful synthesis required thf solvent and
low temperature conditions to give [Sc{OSi(OtBu)3}(CH2SiMe3)2] in a
very low yield.
29 (a) T. D. Tilley, A. Zalkin, R. A. Andersen and D. H. Templeton,
Inorg. Chem., 1981, 20, 551; (b) H. C. Aspinall, D. C. Bradley, M. B.
Hursthouse, K. D. Sales, N. P. C. Walker and B. Hussain, J. Chem. Soc.,
Dalton Trans., 1989, 623.
30 O. Wrobel, F. Schaper, U. Wieser, H. Gregorius and H. H. Brintzinger,
Organometallics, 2003, 22, 1320.
15 The molecular structure of [Sc{OSi(OtBu)3}(CH2SiMe3)2] is isotypic to
◦
˚
that of 1. Selected bond lengths (A) and angles ( ): Sc(1)–C(1) 2.225(3),
Sc(1)–C(5) 2.192(3), Sc(1)–O(1) 2.207(2), Sc(1)–O(2) 2.213(2), Sc(1)–
O(6) 2.063(2); C(1)–Sc(1)–C(5) 109.96(13), O(1)–Sc(1)–O(2) 66.57(8),
O(2)–Sc(1)–O(6) 74.69(8), O(1)–Si(3)–O(2) 94.64(11). Further details
are given in the ESI†.
31 O. Wrobel, F. Schaper and H. H. Brintzinger, Organometallics, 2004,
23, 900.
32 An attempted synthesis of [Lu{OSi(OtBu)3}(CH2SiMe3)(thf)4]+[BPh4]−
from equimolar amounts of HOSi(OtBu)3 and [Lu(CH2SiMe3)2-
(thf)3]+[BPh4]− in thf gave a very poor yield of an impure colour-
less microcrystalline solid. The major product was assigned as
16 D. J. Emslie, W. E. Piers, M. Parvez and R. McDonald, Organometallics,
1
[Lu{OSi(OtBu)3}2(thf)4]+[BPh4]− by H NMR spectroscopy, although
2002, 21, 4226 and references cited therein.
17 K. W. Terry, C. G. Lugmair and T. D. Tilley, J. Am. Chem. Soc., 1997,
119, 9745.
some low intensity Lu–CH2SiMe3 resonances were also detected.
The attempted synthesis of [Lu{OSi(OtBu)3}2(CH2SiMe3)(thf)n] from
two equiv. of HOSi(OtBu)3 and [Lu(CH2SiMe3)3(thf)2] resulted in a
mixture of products both in C6D6 at room temperature and pentane
at −78 ◦C.
18 J. Beckmann, D. Dakternieks, A. Duthie, M. L. Larchin and E. R. T.
Tiekink, Appl. Organomet. Chem., 2003, 17, 52.
19 B. R. Elvidge, S. Arndt, P. M. Zeimentz, T. P. Spaniol and J. Okuda,
Inorg. Chem., 2005, 44, 6777.
33 Similar reactivity of [Ln(C5Me5)2]+[BPh4]− compounds has been
demonstrated: (a) W. J. Evans, C. A. Seibel and J. W. Ziller, J. Am.
Chem. Soc., 1998, 120, 6745; (b) W. J. Evans, J. M. Perotti and J. W.
Ziller, J. Am. Chem. Soc., 2005, 127, 3894.
20 K. Su, T. D. Tilley and M. J. Sailor, J. Am. Chem. Soc., 1996, 118,
3459.
21 P. B. Hitchcock, M. F. Lappert, R. G. Smith, R. A. Bartlett and P. P.
Power, J. Chem. Soc., Chem. Commun., 1988, 1007.
34 (a) [Y(CH2SiMe3)2(thf)4]+[Al(CH2SiMe3)4]−, 2.354(4)–2.479(4) and
[Y(CH3)(thf)6]2+[BPh4]−2, 2.352(3)–2.427(3): ref. 2; (b) [YCl(OCMe3)-
(thf)5]+[BPh4]−, 2.391(5)–2.422(5): W. J. Evans, J. M. Olofson and J. W.
Ziller, J. Am. Chem. Soc., 1990, 112, 2308; (c) [YCl2(thf)5]+[YCl4(thf)2]−,
2.368(5)–2.382(6): P. Sobota, J. Utko and S. Szafert, Inorg. Chem., 1994,
33, 5203; (d) [YCl2(thf)5]+[C2B9H12]−, 2.309(7)–2.401(7): K. Y. Chiu,
Z. Y. Zhang, T. C. W. Mak and Z. W. Xie, J. Organomet. Chem., 2000,
614, 107.
22 Coalescence of a second low intensity resonance was also observed at
a similar temperature, but the coupling pattern at low temperature was
obscured by the larger multiplet. See ESI† for VT spectra.
23 S. Arndt, P. M. Zeimentz, T. P. Spaniol, J. Okuda, M. Honda and K.
Tatsumi, Dalton Trans., 2003, 3622.
˚
24 (a) [LuCp2(CH2SiMe3)(thf)]: Lu–C = 2.376(16) A, see: H. Schumann,
W. Genthe and N. Bruncks, Angew. Chem., Int. Ed. Engl., 1981,
20, 129; H. Schumann, W. Genthe, N. Bruncks and J. Pickardt,
35 (a) T. Sakakura, H.-J. Lautenschlaeger and M. Tanaka, J. Chem. Soc.,
Chem. Commun., 1991, 40; (b) G. A. Molander and M. Julius, J. Org.
Chem., 1992, 57, 6347; (c) P.-J. Fu, L. Brard, Y. Li and T. J. Marks,
J. Am. Chem. Soc., 1995, 117, 7157; (d) T. I. Gountchev and T. D.
Tilley, Organometallics, 1999, 18, 5661; (e) A. A. Trifonov, T. P. Spaniol
and J. Okuda, Dalton Trans., 2004, 2245 and references cited therein.
36 F. Lauterwasser, P. G. Hayes, S. Brase, W. E. Piers and L. L. Schafer,
Organometallics, 2004, 23, 2234.
5
Organometallics, 1982, 1, 1194; (b) [Li(thf)3]+[Lu(g -C5Me5)-
−
˚
(CH2SiMe3){CH(SiMe3)2}Cl] : Lu–C = 2.314(18), 2.344(18) A (two
crystallographically independent molecules), see: H. van der Hei-
jden, P. Pasman, E. J. M. de Boer, C. J. Schaverien and A. G.
Orpen, Organometallics, 1989, 8, 1459; (c) [(C6H3(Me2NCH2)2-
˚
2,6)Lu(l-Cl)(CH2SiMe3)]2: Lu–C = 2.39(3) A, see: M. P. Hoger-
¨
heide, D. M. Grove, J. Boersma, J. T. B. H. Jastrzebski, H. Kooi-
jman, A. L. Spek and G. van Koten, Chem. Eur. J., 1995, 1,
37 Under comparative conditions, the neutral tris(alkyl) [Y(CH2SiMe3)3-
(thf)2] very rapidly deposited an off-white, insoluble solid. 1H NMR
spectroscopy of the supernatant liquid indicated 90% hydrosilylated
olefin (linear product), 10% non-hydrosilylated olefin.
343; (d) [Li(thf)4]+[Lu(CH2SiMe3)2(OC6H3 Bu2-2,6)2]−·2thf: Lu–C =
t
˚
2.29(2), 2.42(3) A, see: W. J. Evans and R. N. R. Broomhall-
Dillard, J. Organomet. Chem., 1998, 569, 89; (e) [Lu(CH2SiMe3)3(thf)2]:
˚
Lu–C = 2.346(3) − 2.380(3) A, see: H. Schumann, D. M. M.
38 P. G. Hayes, W. E. Piers and M. Parvez, J. Am. Chem. Soc., 2003, 125,
Freckmann and S. Dechert, Z. Anorg. Allg. Chem., 2002, 628, 2422;
5622.
900 | Dalton Trans., 2006, 890–901
This journal is
The Royal Society of Chemistry 2006
©

View Article Online
39 (a) P. Voth, S. Arndt, T. P. Spaniol, J. Okuda, A. J. Ackermann and
M. L. H. Green, Organometallics, 2003, 22, 65; (b) P. Voth, T. P. Spaniol
and J. Okuda, Organometallics, 2003, 22, 3921.
1045; (b) S. Bambirra, M. J. R. Brandsma, E. A. C. Brussee, A.
Meetsma, B. Hessen and J. H. Teuben, Organometallics, 2000, 19,
3197.
40 M. Ephritikine, Chem. Rev., 1997, 97, 2193.
44 S. Arndt, T. P. Spaniol and J. Okuda, Organometallics, 2003, 22, 775
41 Selected NMR data for [Y{OSi(OtBu)3}2{l-OSi(OtBu)3}B(C6F5)3-
(thf)n]/[B(C6F5)3(thf)]: dH (C6D6, 298 K) 1.31, 1.42, 1.54, 1.57 (s, 9 × 9
H and 0.5 × 4 H, SiOC(CH3)3, b-thf), 3.77 (0.5 × 4 H,a-thf). dB (C6D6,
298 K) −5.2 (thf–B(C6F5)3), 3.0 (OSi(OtBu)3–B(C6F5)3). dF (C6D6,298
K) −129.8, −132.6, −154.4, −162.3, −164.5, −167.4.
and references therein.
45 ASTRO, SAINT and SADABS. Data Collection and Processing Soft-
ware for the SMART System, Siemens Analytical X-ray Instruments
Inc., Madison, WI, USA, 1996.
46 (a) G. M. Sheldrick, SHELXS-86, Program for Crystal Structure
Solution, University of Go¨ttingen, Germany, 1986; (b) G. M. Sheldrick,
SHELXL-97, Program for Crystal Structure Refinement, University of
Go¨ttingen, Germany, 1997.
42 (a) L. H. Doerrer and M. L. H. Green, J. Chem. Soc., Dalton Trans.,
1999, 4325; (b) L. H. Doerrer, A. J. Graham, D. Haussinger and
M. L. H. Green, J. Chem. Soc., Dalton Trans., 2000, 813.
43 (a) J. P. Mitchell, S. Hajela, S. K. Brookhart, K. I. Hardcastle,
L. M. Henling and J. E. Bercaw, J. Am. Chem. Soc., 1996, 118,
47 International Tables for X-Ray Crystallography, Kluwer Academic
Publishers, Dordrecht, 1992, vol. C.
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 890–901 | 901
©