Reactions of alkali metal and yttrium alkyls with a sterically demanding bis(aryloxysilyl)methane: Formation of aryloxide complexes by Si-O bond cleavage

Article abstract of DOI:10.1016/j.crci.2010.01.017

Reaction of bis(bromodimethylsilyl)methane (BrSiMe₂) ₂CH₂ (1) with two equivalents of 2,6-diisopropylphenol (Ar'OH) in the presence of the auxiliary base NEt₃ affords the bis(aryloxysilyl)methane (Ar'OSiMe₂

Full text of DOI:10.1016/j.crci.2010.01.017

C. R. Chimie 13 (2010) 593–602
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Full paper/Memoire
Reactions of alkali metal and yttrium alkyls with a sterically demanding
bis(aryloxysilyl)methane: Formation of aryloxide complexes by Si-O
bond cleavage
*
Andrew D. Cornish, David P. Mills, William Lewis, Alexander J. Blake, Stephen T. Liddle
School of Chemistry, University of Nottingham, University Park, Nottingham, Nottinghamshire NG7 2RD, United Kingdom
A R T I C L E I N F O
A B S T R A C T
Article history:
Reaction of bis(bromodimethylsilyl)methane (BrSiMe2)2CH2 (1) with two equivalents of
2,6-diisopropylphenol (Ar0OH) in the presence of the auxiliary base NEt3 affords the
bis(aryloxysilyl)methane (Ar0OSiMe2)2CH2 (2) as a colourless oil following work-up. The
reaction of 2 with [Li(Bun)] in the presence of [K(OBut)] promoted Si-O bond cleavage and
the sole isolable product from this reaction was found to be the colourless, crystalline
heterobimetallic complex [{Li(OAr0)}2{K(OAr0)}2(THF)4] (3). The in situ reaction of 2 with
one equivalent of [Li(Bun)] in the presence of one equivalent of [K(OBut)] and subsequent
Received 3 November 2009
Received in revised form 21 January 2010
Accepted after revision 28 January 2010
Available online 24 March 2010
Keywords:
Yttrium
addition to one equivalent of [Y(I)3(THF)3.5
]
afforded colourless, crystalline
Alkali metal
Organosilyl
Carbene
[Y(OAr0)(I)2(THF)3] (4) as the only isolable product. No reaction was observed between
[Y(Bn)3(THF)3] (Bn = CH2C6H5) and one equivalent of 2 in toluene at room temperature;
heating solutions led to decomposition and recovery of 2. In THF, the reaction between
2 and one equivalent of [Y(Bn)3(THF)3] resulted in Si-O bond cleavage with concomitant
Si-C bond formation to give (BnSiMe2)2CH2 (5) as a colourless oil and the colourless,
crystalline compounds [Y(OAr0)2(Bn)(THF)] (7), and [Y(OAr0)3(THF)2] (8) which were
separated by fractional crystallisation. In an attempt to prepare 7 by a rational route,
[Y(OAr0)2(I)(THF)2] (6) was prepared from the reaction of [Y(I)3(THF)3.5] with two
equivalents of [K(OAr0)]. However, although 6 could be prepared by a rational salt
elimination route, attempts to convert it to 7 resulted instead in 8 being recovered as the
only isolable product. This is proposed to be the result of Schlenk-type equilibria, which is
supported by the observation that dissolution of pure 6 in benzene results in the additional
presence of 8 in the 1H NMR spectrum over 12 h. Compound 7 was prepared rationally
from the reaction between [Y(Bn)3(THF)3] and two equivalents of HOAr0. However,
although crystalline 7 could be isolated in sufficient quantities for analysis, NMR spectra
were consistent with the formation of 8 in solution from Schlenk-type equilibria.
Compounds 2–8 have been variously characterised by X-ray diffraction, NMR and FTIR
spectroscopy, and CHN microanalyses.
Bond cleavage
Rare earth
´
ß 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
in the absence of a metal [1], we have recently reported
a range of yttrium derivatives of the bis(iminopho-
In an effort to expand the range of rare earth carbene
complexes which utilise a carbene that is not stable
sphorano)methane H2C(PPh2NSiMe3)2 (H2BIPM) [2],
exemplified by I-IV, Fig. 1, [3] and have reported
preliminary studies of their reactivity towards unsatu-
rated substrates [3c] and in salt elimination reactions to
generate the first unsupported yttrium-gallium bond
[3d].
* Corresponding author.
E-mail address: stephen.liddle@nottingham.ac.uk (S.T. Liddle).
1631-0748/$ – see front matter ß 2010 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2010.01.017

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A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
Fig. 1.
However, the electronic structure of BIPM2ꢀ is com-
lyl)methane (Ar0OSiMe2)2CH2 (2, Ar0 = 2,6-diisopropyl-
phenyl) and its reactions with alkali metal and yttrium
alkyls which reveal facile Si-O bond cleavage and Si-C
bond formation reactions.
plicated by the fact that several resonance forms are valid
[2–4] as exemplified by Fig. 2. Thus, BIPM2ꢀ can be
considered to adopt resonance structures analogous to: N-
heterocyclic carbenes (V and VI); a dipolar form with a
geminal carbon dianion and two anionic amides (VII); a
geminal carbon dianion and two imino groups (VIII); and a
carbodiphosphorane with two anionic amides (IX). The
later resonance form is particularly interesting because it is
predicated on the assignment of a P(V) oxidation state, but
an alternative and credible [5] assignment is that of two
amido-functionalised P(III) centres datively coordinated to
2. Results and discussion
2.1. Synthesis of 2
We selected (BrSiMe2)2CH2 (1) as a start point for the
synthesis of ligands of type XI as its synthesis was
reported previously by Barrau and Satge [6]. Accordingly,
treatment of ClSiMe2CH2Cl with PhMgBr afforded PhSi-
Me2CH2Cl, and conversion to the corresponding Grignard
and reaction with Me2SiHCl gave PhSiMe2CH2SiHMe2,
which delivered 1 in good yield following treatment with
bromine and vacuum distillation. We noted that the use of
1.1 equivalents of PhMgBr was necessary to ensure
excellent (ꢁ85 %) yields in the first step. Subsequent
reaction of 1 with two equivalents of Ar0OH (Ar0 = 2,6-
diisopropylphenyl) in the presence of the auxiliary base
triethylamine afforded (Ar0OSiMe2)2CH2 (2) as a colour-
less oil in 85 % yield following separation from the
Et3N.HBr by-product and work-up, Fig.4. The NMR spectra
of 2 is straightforward as would be expected, and the
CH2 resonates as a singlet at 0.23 ppm in the 1H NMR
spectrum and a single resonance in the 29Si NMR spectrum
is observed at 15.21 ppm.
a
zero-valent carbon centre (X), Fig. 2. Whilst DFT
calculations have delivered insight into the electronic
structure of the BIPM2ꢀ dianion and suggest the Nꢀ-P+-
C2ꢀ-P+-Nꢀ dipolar resonance form is prevalent [3,4], the
possibility of a captodative carbodiphosphorane assign-
ment [5a] cannot be dismissed [3b].
Consequently, we turned our attention towards an
analogous silicon system because this would remove the
P(III)/P(V) assignment problem since an unambiguous
oxidation state of IV would be clear-cut for silicon. In
order to retain a valence isoelectronic ligand framework
which would still be dianionic following double depro-
tonation, RO rather than RN groups would be required.
We therefore targeted
a
bis(aryloxysilyl)methane
(H2BASM) exemplified by XI, Fig. 3. Herein, we report
the synthesis of the sterically demanding bis(aryloxysi-

A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
595
Fig. 2.
2.2. Solid state structure of 2
in tris-alkyl rare earth chemistry [9]. However, treatment
of 2 with [Li(Bun)] in the presence of [K(OBut)] does not
afford the corresponding potassium alkyl. Rather, the
superbasic mixture is apparently too aggressive and
instead promotes Si-O bond cleavage. Although the exact
fate of 2 is not clear it seems likely that the silicon centres
in 2 are functionalised with a mixture of butyl and tert-
butoxy groups as colourless crystals of the complex
shown to be [{Li(OAr0)}2{K(OAr0)}2(THF)4] (3) were
isolated from THF as the sole isolable product in 50 %
yield, Fig. 4. Although this fragmentation is unfortunate,
ligand fragmentation was not entirely unexpected as
Lappert showed that although alkali metal complexes
of {CH(SiMe3)(SiMe2OMe)}ꢀ could be obtained in
crystalline form, the corresponding bis-methoxy
CH2(SiMe2OMe)2 compound fragmented on lithiation
Colourless single crystals of 2 were grown from hexane
at ꢀ80 8C; the molecular structure is illustrated in Fig. 5
and selected bond lengths are compiled in Table 1. The
structure is unremarkable; the Si-O and O-Caryl bond
distances average 1.6676(12) and 1.3837(18) A, respec-
tively, which, for example, compares favourably to
˚
observed Si-O and O-Caryl bond lengths of 1.677 and
t
˚
1.366 A, respectively, in (Bu )3SiCH(SiMe3)SiMe2OC6F4-4-
Me [7].
2.3. Synthesis of 3
Encouraged by the fact that Lappert disclosed that
(Me3Si)2CH2 could be deprotonated by [Li(Bun)] in the
presence of [K(OBut)] to give the corresponding potas-
sium alkyl [8], we initially sought to access alkali metal
derivatives of 2 to employ in subsequent salt elimination
chemistry, since mono-functionalised bis(organosilyl)-
methanides have been successfully prepared and utilised
to give the expected complex [Li{CH(SiMe2OMe)2}] as
1
the minor product (4 %) and the tris-methoxy compound
[Li{C(SiMe2OMe)3}]2 as the major product (64 %) [10].
Germane to these observations are that the fragmenta-
tion of methoxy-functionalised tris(triorganosilyl)-
methanide complexes by electropositive metals has
been observed previously [11] and the cleavage of Si-O
linkages in vacuum joint grease has ample precedent
[12]. The room temperature 1H and 13C NMR spectra of
3 in THF exhibits only one Ar0 environment and a variable
temperature study between +25 8C and ꢀ80 8C showed
little variation and no de-coalescence which indicates
facile and fast exchange of the aryloxide groups in
solution compared to the NMR time-scale.
Fig. 3.

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A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
Fig. 4. Synthesis of 1–8. Complexes 6 and 8 have been prepared by rational routes.
Fig. 5. Molecular structure of 2 with selective labelling. Hydrogen atoms omitted for clarity.
2.4. Solid state structure of 3
compared to potassium; the lithium centres, although
only three-coordinate, maximise their contacts to the
hard aryloxide ligands whereas the softer potassium
The molecular structure of 3 is shown in Fig. 6 and
selected bond lengths are listed in Table 1. Complex
3 crystallises as a tetrametallic, di-lithium di-potassium
aggregate. Although the crystallographic data were poor
the identity and connectivity of 3 is clear-cut. The complex
is constructed around a centrosymmetric Li2O2 core which
resides over an inversion centre and each three-coordinate
lithium centre bridges to another aryloxide which in turn
bridges to a potassium centre. The coordination sphere of
each potassium centre is completed by the oxygen atoms
of two molecules of THF, an h6-interaction with the phenyl
ring of the aryloxide associated with the Li2O2 core and an
h1-interaction with the second Ar0 ligand. The construction
of 3 is entirely in line with the hard nature of lithium
centres engage mainly with the soft
p-systems of the
aryloxide ligands. The Li-O, K-Oaryl, and K-OTHF bond
lengths are unremarkable [13]. The h6-K-Caryl bond
˚
distances span the range 3.169(5)-3.303(7)
A (av.
˚
˚
3.238 A) and compare favourably to the 3.1–3.9 A range
of reported h6-K-Caryl bond distances in the literature [14].
However, the h1-K-Caryl distance of 3.359(5) A is rather
˚
longer than the h6-K-Caryl range.
2.5. Synthesis of 4
Before the true identity of the product of the reaction
between 2 and [Li(Bun)]/[K(OBut)] was known, we treated

A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
597
Table 1
order to confirm the structure, colourless single crystals of
4 were grown from a solution in toluene.
Selected bond lengths for 2, 3.C4H8O, 4, 7.C6H5CH3, and 8.
2
C(1)-Si(1)
Si(1)-O(1)
O(1)-C(4)
1.8655(16)
1.6717(12)
1.3825(19)
C(1)-Si(2)
Si(2)-O(2)
O(2)-C(18)
1.8559(16)
1.6635(12)
1.3849(18)
2.6. Solid state structure of 4
The molecular structure of 4 is illustrated in Fig. 7 and
selected bond lengths are given in Table 1. Complex
4 crystallises on a crystallographic two-fold rotation axis
which intersects the O(1)-Y(1)-O(2) axis, which is there-
fore rigorously linear by definition. The complex is
approximately octahedral at yttrium which is coordinated
to the oxygen atom of the aryloxide, two iodides, and three
THF molecules. Surprisingly, only two Y-OAr0 containing
complexes have been crystallographically authenticated to
3.C4H8O
Li(1)-O(1)
Li(1)-O(2)
K(1)-O(3)
K(1)ꢂ ꢂ ꢂC(1)
K(1)ꢂ ꢂ ꢂC(3)
K(1)ꢂ ꢂ ꢂC(5)
K(1)ꢂ ꢂ ꢂC(13)
1.888(11)
1.803(11)
2.707(5)
3.159(6)
3.258(8)
3.329(10)
3.323(6)
Li(1)-O(1A)
K(1)-O(2)
1.840(10)
2.642(5)
2.664(5)
3.185(7)
3.310(10)
3.254(7)
K(1)-O(4)
K(1)ꢂ ꢂ ꢂC(2)
K(1)ꢂ ꢂ ꢂC(4)
K(1)ꢂ ꢂ ꢂC(6)
4
Y(1)-O(1)
Y(1)-I(1A)
Y(1)-O(3)
2.046(3)
2.9868(4)
2.319(3)
Y(1)-I(1)
2.9868(4)
2.393(4)
2.319(3)
date, namely [Y(OAr0){Al( -Me)(Me)2OAr0}2] by Anwander
m
Y(1)-O(2)
Y(1)-O(3A)
[16] and [Y{C6H3-2,6-(C6H4-2-OMe)2}(OAr0)2(THF)] by
Rabe [17]. Complex 4 is thus the first mono-OAr0 complex
of yttrium and is notable for its kinetic stability. The Y(1)-
7.C6H5CH3
Y(1)-C(1)
Y(1)-O(1)
Y(1)-O(3)
2.416(5)
2.099(2)
2.323(3)
Y(1)ꢂ ꢂ ꢂC(2)
Y(1)-O(2)
Y(1)-O(4)
2.935(4)
2.099(2)
2.332(3)
˚
O(1) bond length of 2.046(3) A compares with bond
˚
distances of 2.023 and 2.100/2.122 A, respectively for the
two aforementioned aryloxide complexes [16,17]. The
Y(1)-I bond lengths are comparable to those observed in
[Y(I)3(THF)3.5] [18] and the Y(1)-THF bond lengths are
unremarkable.
8
Y(1)-O(1)
Y(1)-O(3)
Y(1)-O(5)
2.086(2)
2.085(2)
2.344(3)
Y(1)-O(2)
Y(1)-O(4)
2.069(3)
2.351(3)
2.7. Synthesis of 5–8
an in situ mixture of 2 and [Li(Bun)]/[K(OBut)] with
[Y(I)3(THF)3.5]. Colourless crystals were isolated in 47 %
yield and subsequently identified as the complex
[Y(OAr0)(I)2(THF)3] (4), Fig. 8. The 1H and 13C NMR spectra
exhibited resonances consistent with a mono-aryloxide
complex which is noteworthy because monomeric, mono-
aryloxide-di-halide rare earth complexes are few in
number, and usually result from the use of aryloxides
that are considerably more sterically demanding than
diisopropylphenyl as otherwise dimers are isolated [15]. In
Since a superbasic mixture of [Li(Bun)]/[K(OBut)] was
apparently too aggressive for 2, we switched our attention
to [Y(Bn)3(THF)3] (Bn = CH2C6H5) [4c]. Since [Y(Bn)3(THF)3]
and 2 do not react in toluene which is apparently due to the
low solubility of the tribenzyl in arene solvents, we tested
the reaction of [Y(Bn)3(THF)3] and 2 in THF. However, facile
Si-O bond cleavage was observed again; although the
resonance associated with the CH2 group was essentially
unchanged in the 1H NMR spectrum, the 29Si NMR
Fig. 6. Molecular structure of 3.C4H8O with selective labelling of symmetry unique atoms. Hydrogen atoms omitted for clarity. Multi-hapto interactions are
shown as dashed lines.

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A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
amount (ꢁ10 %) of 8 in addition to the resonances for 6.
Such an equilibrium could explain why 7 is not available
from 6.
2.8. Solid state structure of 7.C6H5CH3
A very small crop of crystals of 7.C6H5CH3 suitable for X-
ray diffraction were grown from toluene; the molecular
structure is shown in Fig. 8 and selected bond lengths are
complied in Table 1. Complex 7.C6H5CH3 crystallises as a
monomer with an approximately square based pyramidal
geometry at yttrium such that the benzyl carbon occupies
the axial site. One molecule of toluene co-crystallises in the
lattice. In addition to the Y(1)-C(1) bond distance of
˚
2.416(5) A, which compares with Y-CBn bond lengths
˚
spanning the range 2.452(3)-2.463(3) A in [Y(Bn)3(THF)3]
˚
[3c], a Y(1)ꢂ ꢂ ꢂC(2)ipso distance of 2.935(4) A is suggestive of
an h2-bonding mode of benzyl which is congruent with the
compressed Y(1)-C(1)-C(2) angle of 95.9(3)8 and Yꢂ ꢂ ꢂCipso
˚
contact distance of 2.921(4) A in II [3c]. The Y(1)-O(1) and
˚
Y(1)-O(2) bond lengths of 2.099(2) and 2.099(2) A are
significantly longer than the Y-OAr0 bond distance in
4 reflecting the more sterically crowded environment at
yttrium in 7.C6H5CH3 compared to 4. The steric crowding
may also be reflected in the fact the two Y-O-Cipso bond
angles at O(1) and O(2) deviate from linear to 166.8(2) and
169.4(2)8, respectively, which contrasts to the linear Y-O-
Cipso bond angle in 4.
2.9. Solid state structure of 8
Fig. 7. Molecular structure of 4 with selective labelling of symmetry
unique atoms. Hydrogen atoms omitted for clarity.
Crystals of 8 suitable for X-ray crystallography were
obtained from toluene; the molecular structure is
illustrated in Fig. 9 and selected bond lengths are given
in Table 1. Complex 8 crystallises as a monomer with
approximately trigonal bipyramidal geometry at yttrium
where the two coordinated THF molecules occupy the
axial sites leaving the three aryloxides to occupy the more
spacious equatorial positions. Overall, the structure is
very similar to the lanthanum, praseodymium, samarium,
gadolinium, dysprosium, erbium, and lutetium congeners
[19,20]. Interestingly, the cerium analogue has also been
isolated as a tris-THF adduct [21], the dimeric solvent free
analogues have been characterised for lanthanum,
neodymium, samarium, and dysprosium [19a,d,e], and
monomeric mono-THF and THF-free analogues are
known for dysprosium [19a]. The Y(1)-O(1), Y(1)-O(2),
and Y(1)-O(3) bond lengths of 2.086(2), 2.069(3), and
spectrum revealed a resonance at 1.17 ppm showing the
formation of (BnSiMe2)2CH2 (5). The assertion of benzyl-
aryloxide exchange was supported by the isolation of two
new compounds by fractional crystallisation, namely
[Y(OAr0)2(Bn)(THF)] (7) and [Y(OAr0)3(THF)2] (8). However,
for 7 only enough material to obtain an X-ray diffraction
data set was isolated. We therefore prepared [Y(OAr0)2
(I)(THF)2] (6) from the reaction between [Y(I)3(THF)3.5] and
two equivalents of [K(OAr0)] then treated it with one
equivalent of [K(Bn)]. However, this route produced 8 as
the sole isolable product, presumably from Schlenk-type
ligand exchange. Unfortunately, X-ray diffraction quality
crystals of 6 have not been obtained. Complex 7 was
prepared rationally from the reaction of [Y(Bn)3(THF)3]
and two equivalents of HOAr0 and was isolated as
colourless crystals in 9 % yield. This low yield may be
explained by the fact that solution NMR spectra of 7 are
essentially identical to that of 8, which is presumably the
result of facile Schlenk-type equilibria in solution. Com-
plex 8 can also be prepared from the reaction of one
equivalent of [K(OAr0)] with 6 or three equivalents of
[K(OAr0)] with [Y(I)3(THF)3.5]. Surprisingly, although com-
plex 4 appears to be kinetically stable in solution with
respect to ligand exchange, dissolution of pure 6, as
evidenced by NMR and CHN, in d6-benzene results in the
establishment of a Schlenk-type equilibria over 12 h and
the observation of resonances attributable to a small
0
˚
2.085(2) A compare well to the observed Y-OAr bond
distances in 6. The two long and one shorter Y-O bond
lengths match a trend in Y-O-Cipso bond angles; the angles
at O(1), O(2), and O(3) of 174.7(3), 153.7(2), and 174.6(3)8
are counter intuitive because conventional logic would
suggest a shorter and stronger Y-O bond would be
anticipated from a more linear Y-O-Cipso arrangement.
However, we suggest the bond distances are not
indicative of bond strength but rather of the sterically
crowded environment at yttrium which forces the polar
Y-O-Cipso bond angles to deviate from linear since the
energy profile for bending in such ionic bonds would be
expected to be rather flat.

A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
599
Fig. 8. Molecular structure of 7.C6H5CH3 with selective labelling. Hydrogen atoms omitted for clarity. Multi-hapto interactions are shown as dashed lines.
Fig. 9. Molecular structure of 8 with selective labelling. Hydrogen atoms omitted for clarity.
3. Summary and conclusions
of [Li(Bun)/K(OBut)] 2 undergoes Si-O bond cleavage to
give [{Li(OAr0)}2{K(OAr0)}2(THF)4] (3) and addition of
[Y(I)3(THF)3.5] results in the isolation of [Y(OAr0)(I)2(THF)3]
(THF)3] (4). The reaction of 2 with [Y(Bn)3(THF)3] in THF
results in Si-O bond cleavage and Si-C bond formation to
In summary, we have prepared a new bis(aryloxysi-
lyl)methane (Ar0OSiMe2)2CH2 (2) and have tested it in
reactions with electropositive metal alkyls. In the presence

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A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
give (BnSiMe2)2CH2 (5), [Y(OAr0)2(Bn)(THF)] (7), and
[Y(OAr0)3(THF)2] (8). The complex [Y(OAr0)2(I)(THF)2] (6),
was prepared by a rational route, but attempts to prepare
7 from it resulted in the isolation of 8 and pure 6 was found
to slowly establish a Schlenk-type equilibrium with 8 in
m-Ar-CH). 13C{1H} NMR (d-chloroform, 298 K):
d 3.30
(Si(CH3)2), 6.53 (CH2Si2), 23.59 (CH(CH3)2), 27.10
(CH(CH3)2), 122.13 (p-Ar-C), 123.53 (m-Ar-C), 139.13 (o-
Ar-C) and 149.58 (ipso-Ar-C). 29Si NMR (d-chloroform,
298K):
d 15.21. IR v
=cmꢀ1 (Nujol): 1589 (w), 1362 (m),
benzene. Complex
[Y(Bn)3(THF)3] and two equivalents of HOAr0 but was
found to convert to in solution by Schlenk-type
7
was prepared rationally from
1330 (m), 1260 (s), 1196 (m), 1098 (m), 1047 (br, s), 918
(s), 814 (br, s), 756 (m).
8
equilibria. We are currently investigating the behaviour
of 2 towards [Li(But)] in pentane and are investigating
the synthesis of the bis(aryloxysilyl)bromomethane
(Ar0OSiMe2)2CHBr. The latter would enable low tempera-
ture lithium-halide exchange to take place and this would
represent a milder route to the corresponding alkali metal
bis(aryloxysilyl)methanides that would be less prone to
ligand fragmentation reactions.
4.3. Preparation of [{Li(OAr0)}2{K(OAr0)}2(THF)4] (3)
[Li(Bun)] (2 ml, 2.5 M in hexane) was added dropwise to
a pre-cooled (ꢀ78 8C) mixture of 2 (2.42 g, 5 mmol) and
[K(OBut)] (0.56 g, 5 mmol) in THF (20 ml). The mixture was
allowed to slowly warm to room temperature with stirring
over 18 hours. Volatiles were removed in vacuo and the
resulting white solid was washed with hexane (20 ml) to
afford 3. Crude yield: 2.05 g, 75 %. Crystals suitable for X-
ray crystallography were grown from THF (5 ml) at ꢀ25 8C.
Yield 1.36 g, 50 %. Anal Calcd for C64H100K2Li2O8: C, 70.53;
4. Experimental
4.1. General
H, 9.25. Found: C, 70.49; H, 9.31. 1H NMR (d8-THF, 298 K):
d
1.04 (d, 48H, JHH = 6.80 Hz, CH(CH3)2), 3.44 (sept, 8H,
JHH = 6.80 Hz, CH(CH3)2), 6.07 (t, 4H, JHH = 7.60 Hz, p-Ar-CH)
and 6.63 (d, 8H, JHH = 7.60 Hz, m-Ar-CH). 13C{1H} NMR (d8-
All manipulations were carried out using standard
Schlenk techniques, or an MBraun UniLab glovebox, under
an atmosphere of dry nitrogen. Solvents were dried by
passage through activated alumina towers and degassed
before use. All solvents were stored over potassium
mirrors (with the exception of THF which was stored over
THF, 298 K):
(p-Ar-C), 122.54 (m-Ar-C), 135.77 (o-Ar-C) and 164.47
(ipso-Ar-C). 7Li NMR (d8-THF, 298 K): =cmꢀ1
d 24.14 (CH(CH3)2), 27.23 (CH(CH3)2), 111.14
d
ꢀ0.83. IR
v
(Nujol): 1583 (m), 1345 (s), 1281 (m), 1263 (m), 1155 (w),
1137 (w), 1105 (w), 1042 (w), 886 (m), 849 (m), 802 (w),
763 (s), 752 (s).
˚
activated 4 A molecular sieves). Deuterated solvents were
distilled from potassium or CaH2, degassed by three
freeze-pump-thaw cycles and stored under nitrogen. The
compounds (BrSiMe2)2CH2 [6], [Y(I)3(THF)3.5
]
[18],
4.4. Preparation of [Y(OAr0)(I)2(THF)3] (4)
[Y(Bn)3(THF)3] [3c], [K(OAr0)] [13], and [K(Bn)] [22] were
prepared according to published procedures. Triethyla-
mine was distilled from calcium hydride. Ar0OH was stored
THF (30 ml) was added to a pre-cooled (ꢀ78 8C) mixture
of [Y(I)3(THF)3.5] (2.83 g, 3.92 mmol) and in situ formed 3
(2.05 g, 1.88 mmol). The mixture was allowed to slowly
warm to room temperature with stirring over 24 h. The
solution was filtered and volatiles were removed in vacuo
and the resulting off-white solid was recrystallised from
toluene (4 ml) to afford 4 as colourless crystals. Yield: 1.36 g,
47 %. Anal Calcd for C24H41I2O4Y: C, 40.02; H, 5.74. Found: C,
˚
over 4 A sieves. All other chemicals were purchased from
Aldrich and were used as supplied.
1H, 13C, and 29Si NMR spectra were recorded on a Bruker
400 spectrometer operating at 400.2, 100.6, and 79.5 MHz,
respectively; chemical shifts are quoted in ppm and are
relative to TMS (1H, 13C, and 29Si). FTIR spectra were
recorded on a Bruker Tensor 27 spectrometer. Elemental
microanalyses were carried out by Mr Stephen Boyer at the
Microanalysis Service, London Metropolitan University,
UK.
39.98; H, 5.67. 1H NMR (d6-benzene, 298 K):
d 1.45 (m, 12H,
OCH2CH2), 1.58 (d, 12H, CH(CH3)2 JHH = 6.00 Hz), 4.08 (m,
12H, OCH2CH2), 4.52 (br, 2H, CH(CH3)2), 7.10 (t, 1H,
JHH = 7.60 Hz, p-Ar-CH) and 7.35 (d, 2H, JHH = 7.60 Hz,
m-Ar-CH). 13C{1H} NMR (d6-benzene, 298 K):
d 24.96
4.2. Preparation of (Ar0OSiMe2)2CH2 (2)
(br, CH(CH3)2 and OCH2CH2), 26.38 (CH(CH3)2), 71.25
(OCH2CH2), 118.62 (p-Ar-C), 123.36 (m-Ar-C), 137.63 (o-
Ar0OH (10.36 ml, 55.2 mmol) in diethyl ether (30 ml)
was added to a pre-cooled (ꢀ78 8C) mixture of (BrSi-
Me2)2CH2 (8.00 g, 27.6 mmol) and NEt3 (7.89 ml,
55.2 mmol) in diethyl ether (50 ml). The mixture was
allowed to warm slowly to room temperature with stirring
over 18 hours. The mixture was filtered and volatiles were
removed in vacuo to afford 2 as a colourless oil. Yield:
11.21 g, 84 %. Crystals suitable for a X-ray crystallography
were grown from hexane (10 ml) at ꢀ80 8C. Anal Calcd for
Ar-C) and 157.58 (ipso-Ar-C). IR v
=cmꢀ1 (Nujol): 1588 (m),
1336 (s), 1267 (s), 1208 (m), 1173 (m), 1100 (m), 1039 (m),
1008 (s), 920 (m), 890 (m), 854 (s), 751 (m), 723 (m).
4.5. Preparation of [Y(OAr0)2(I)(THF)2] (6)
THF (30 ml) was added to a pre-cooled (ꢀ78 8C) mixture
of [Y(I)3(THF)3.5] (1.89 g, 2.61 mmol) and [K(OAr0)] (1.13 g,
5.22 mmol). The mixture was allowed to slowly warm to
room temperature with stirring over 24 h. The solution
was filtered and volatiles were removed in vacuo and the
resulting off-white solid was recrystallised from toluene
(4 ml) to afford 6 as colourless crystals. Yield: 0.94 g, 51 %.
Anal Calcd for C43H66IO5Y: C, 58.77; H, 7.57. Found: C,
C
29H48O2Si2: C, 71.90; H, 9.92. Found: C, 72.00; H, 10.00. 1H
NMR (d-chloroform, 298 K):
d 0.23 (s, 2H, CH2Si2), 0.46 (s,
12H, Si(CH3)2), 1.32 (d, 24H, JHH = 6.90 Hz, CH(CH3)2),
3.37 (sept, 4H, JHH = 6.90 Hz, CH(CH3)2), 7.09 (t, 2H,
JHH = 7.40 Hz, p-Ar-CH) and 7.19 (d, 4H, JHH = 7.50 Hz,

A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
601
Table 2
Crystallographic data for 2–4, 7.C6H5CH3, and 8.
2
3.C4H8O
4
7.C6H5CH3
8
Formula
C
29H48O2Si2
C68H108K2Li2O9
1161.62
C24H41I2O4Y
736.28
C46H65O4Y
770.89
C44H67O5Y
764.89
Fw
484.85
Cryst size, mm
Cryst syst
Space group
0.37 ꢃ 0.19 ꢃ 0.10
Triclinic
P-1
0.30 ꢃ 0.18 ꢃ 0.13
Monoclinic
P21/c
0.40 ꢃ 0.40 ꢃ 0.21
Orthorhombic
Pbcn
0.32 ꢃ 0.30 ꢃ 0.21
Monoclinic
P21/c
0.47 ꢃ 0.39 ꢃ 0.29
Monoclinic
P21
˚
a, A
9.6735(7)
12.2705(8)
13.8619(9)
70.965(1)
74.690(1)
87.871(1)
1498.05(18)
2
10.705(2)
9.2246(10)
17.924(2)
13.8410(7)
17.6892(10)
18.6316(10)
9.6919(5)
˚
b, A
17.677(4)
19.3180(10)
12.1546(6)
˚
c, A
21.243(4)
17.868(2)
a,8
b
,8
120.060(8)
107.996(2)
109.519(2)
g,8
3
˚
V, A
3479.2(12)
2
2954.4(6)
4
4338.5(4)
4
2144.90(19)
2
Z
rcalcd, g cmꢀ3
, mmꢀ1
1.075
1.109
1.655
1.180
1.184
m
0.140
0.187
4.088
1.383
1.400
No. of reflections measd
No. of unique reflns, Rint
No. of reflns with F2 > 2
13385
24847
16698
22477
7053
6764, 0.0200
6060
6145, 0.0984
3750
3377, 0.0499
2414
7614, 0.0317
5820
4609, 0.0260
4291
s
(F2)
Transmn coeff range
0.90–0.98
0.0508, 0.1181
0.0570, 0.1221
1.108
0.79–0.98
0.1260, 0.2640
0.1667, 0.2787
1.127
0.26–0.46
0.0376, 0.0821
0.0662, 0.0920
1.037
0.63–0.73
0.0417, 0.0989
0.0620, 0.1087
1.035
0.54–0.67
0.0302, 0.0694
0.0322, 0.0698
0.890
R, Rw (F2 > 2
s)
a
a
R, Rw (all data)
Sa
Parameters
310
352
145
468
463
ꢀ3
˚
Max., min. diff map, e A
0.493, ꢀ0.188
P
0.373, ꢀ0.493
1.062, ꢀ0.436
2
0.656, ꢀ0.306
0.380, ꢀ0.210
1=2
P
P
P
P
2
2
1=2
a
Conventional R ¼ jjFoj ꢀ jFcjj= jFoj; Rw ¼ ½ wðFo2 ꢀ Fc2Þ = wðFo2Þ ꢄ ; S ¼ ½ wðFo2 ꢀ Fc2Þ =no: data ꢀ no: paramsÞꢄ
for all data.
58.66; H, 7.67. 1H NMR (d6-benzene, 298 K):
d
1.22 (m, 8H,
69.01; H, 8.94. 1H NMR (d6-benzene, 298 K):
d 1.22 (m, 8H,
OCH2CH2), 1.54 (d, 24H, JHH = 6.40 Hz, CH(CH3)2), 3.91 (m,
8H, OCH2CH2), 4.00 (br, 4H, CH(CH3)2), 7.09 (t, 2H,
JHH = 7.60 Hz, p-Ar-CH) and 7.34 (d, 4H, JHH = 7.60 Hz, m-
OCH2CH2), 1.45 (d, 24H, JHH = 6.80 Hz, CH(CH3)2), 3.66
(sept, 4H, JHH = 6.80 Hz, CH(CH3)2), 3.91 (m, 8H, OCH2CH2),
7.08 (t, 2H, JHH = 7.40 Hz, p-Ar-CH) and 7.33 (d, 4H,
JHH = 7.60 Hz, m-Ar-CH). 13C{1H} NMR (d6-benzene,
Ar-CH). 13C{1H} NMR (d6-benzene, 298 K):
d 23.96
(CH(CH3)2), 24.75 (OCH2CH2), 27.41 (CH(CH3)2), 71.93
(OCH2CH2), 118.49 (p-Ar-C), 123.11, 125.46 (m-Ar-C),
298 K): d 23.63 (CH(CH3)2), 25.00 (OCH2CH2), 27.41
(CH(CH3)2), 71.59 (OCH2CH2), 117.49 (p-Ar-C), 122.94,
2
136.13 (o-Ar-C) and 157.68 (br, ipso-Ar-C). IR
v
=cmꢀ1
(m-Ar-C), 135.93 (o-Ar-C) and 157.92 (d, JCY = 5.03 Hz,
(Nujol): 1586 (w), 1334 (m), 1261 (s), 1209 (m), 1145 (m),
1042 (m), 1013 (m), 935 (m), 889 (m), 859 (m), 802 (m),
753 (m).
ipso-Ar-C). IR v
=cmꢀ1 (Nujol): 1586 (m), 1332 (s), 1209 (m),
1041 (m), 1016 (m), 888 (m), 863 (s), 753 (m).
4.8. X-ray Crystallography
4.6. Preparation of [Y(OAr0)2(Bn)(THF)2] (7)
Crystal data for compounds 2, 3.C4H8O, 4,
7.C6H5CH3 and 8 are given in Table 2, and further details
of the structure determinations are in the Supporting
Information. Bond lengths are listed in Table 1. Crystals
were examined on a Bruker AXS SMART APEX CCD area
A solution of HOAr0 (0.75 ml, 4 mmol) in THF (10 ml)
was added to a solution of [Y(Bn)3(THF)3] (1.24 g, 2 mmol)
in THF (10 ml) dropwise at ꢀ78 8C. The solution was
allowed to warm to room temperature and then stirred for
24 hours. Volatiles were removed in vacuo to yield a brown
oil. The brown oil was washed with hexane (10 ml) to yield
a white solid. Yield: 0.1 g, 9 %. Anal. calcd for C39H57O4Y: C,
detector diffractometer using graphite-monochromated
˚
a radiation (l = 0.71073 A). Intensities were inte-
MoK
grated from a sphere of data recorded on narrow (0.38)
frames by rotation. Cell parameters were refined from
69.03; H, 8.41. Found: C, 68.88; H, 8.34. IR
v
=cmꢀ1 (Nujol):
v
1459 (s), 1377 (s), 1331 (s), 1262 (w), 1209 (s), 1016 (w),
863 (s), 799 (s) 753 (s) and 692 (s).
the observed positions of all strong reflections in each data
set. Semi-empirical absorption corrections based on
symmetry-equivalent and repeat reflections were applied.
The structures were solved variously by direct or Patterson
methods and were refined by full-matrix least-squares on
all unique F2 values, with anisotropic displacement
parameters for all non-hydrogen atoms, and with con-
strained riding hydrogen geometries; Uiso(H) was set at 1.2
(1.5 for methyl groups) times Ueq of the parent atom. The
largest features in final difference syntheses were close to
heavy atoms and were of no chemical significance. The
Flack parameters for 8 refined to ꢀ0.017(5) confirming
that the correct absolute structure had been adopted. The
4.7. Preparation of [Y(OAr0)3(THF)2] (8)
THF (10 ml) was added to a pre-cooled (ꢀ78 8C) mixture
of 6 (0.76 g, 0.86 mmol) and [K(Bn)] (0.11 g, 0.86 mmol).
The mixture was allowed to slowly warm to room
temperature with stirring over 18 h. The solution was
filtered and volatiles were removed in vacuo and the
resulting off-white solid was recrystallised from toluene
(2 ml) to afford 8 as colourless crystals. Yield: 0.26 g, 59 %.
Anal Calcd for C44H67O5Y: C, 69.09; H, 8.83. Found: C,

602
A.D. Cornish et al. / C. R. Chimie 13 (2010) 593–602
(c) L. Orzechowski, G. Jansen, S. Harder, J. Am. Chem. Soc 128 (2006)
14676.
[5] (a) M. Alcarazo, C.W. Lehmann, A. Anoop, W. Thiel, A. Fu¨rstner, Nature
Chem 1 (2009) 295;
data for 3.C4H8O were persistently weak and of poor
quality, despite several attempts at recrystallisation under
different conditions, resulting in a high R1 but the chemical
connectivity is unambiguous. Disorder of coordinated THF
in 7.C6H5CH3 could not be modelled. The data for 8 were
weak and/or absent at high angle but the structure is
unambiguous. Programs were Bruker AXS SMART (control)
and SAINT (integration) [23], and SHELXTL was employed
for structure solution and refinement and for molecular
graphics [24]. Disordered lattice THF in 3 which could not
be modelled was treated with the Platon SQUEEZE
procedure [25].
¨
(b) R. Tonner, F. Oxler, B. Neumu¨ller, W. Petz, G. Frenking, Angew.
Chem. Int. Ed 45 (2006) 8038.
[6] J. Barrau, N.B. Hamida, A. Agrebi, J. Satge, Organometallics 8 (1989)
1585.
[7] N. Wiberg, T. Passler, K. Polborn, J. Organomet. Chem 531 (1997) 47.
[8] P.B. Hitchcock, A.V. Khvostov, M.F. Lappert, J. Organomet. Chem 663
(2002) 263.
[9] A.G. Avent, C.F. Caro, P.B. Hitchcock, M.F. Lappert, Z. Li, X.-H. Wei, Dalton
Trans (2004) 1567.
[10] F. Antolini, P.B. Hitchcock, M.F. Lappert, X.-H. Wei, Organometallics 22
(2003) 2505.
[11] (a) L.J. Bowman, K. Izod, W. Clegg, R.W. Harrington, J. Organomet.
Chem 692 (2007) 806;
(b) L.J. Bowman, K. Izod, W. Clegg, R.W. Harrington, Organometallics
25 (2006) 2999;
Acknowledgements
(c) L.J. Bowman, K. Izod, W. Clegg, R.W. Harrington, J.D. Smith, C.
Eaborn, Dalton Trans (2006) 502.
[12] I. Haiduc, Organometallics 23 (2004), 3 and references therein.
[13] T.J. Boyle, N.L. Andrews, M.A. Rodriguez, C. Campana, T. Yiu, Inorg.
Chem 42 (2003) 5357.
We thank the Royal Society, the UK EPSRC, and the
University of Nottingham for supporting this work.
[14] (a) S.T. Liddle, P.L. Arnold, Dalton Trans (2007) 3305;
(b) G.C. Forbes, A.R. Kennedy, R.E. Mulvey, B.A. Roberts, R.B. Rowlings,
Organometallics 21 (2002) 5115;
Appendix A. Supplementary material
(c) W. Clegg, E.K. Cope, A.J. Edwards, F.S. Mair, Inorg. Chem 37 (1998)
2317;
(d) G.W. Rabe, S. Kheradmandan, G.P.A. Yap, Inorg. Chem 37 (1998)
6541;
Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.crci.
2010.01.017.
(e) K.W. Klinkhammer, Chem. Eur. J 3 (1997) 1418.
[15] (a) X. Xu, Z. Zhang, Y. Yao, Y. Zhang, Q. Shen, Inorg. Chem 46 (2007)
9379;
References
(b) G.B. Deacon, G.D. Fallon, C.M. Forsyth, S.C. Harris, P.C. Junk, B.W.
Skelton, A.H. White, Dalton Trans (2006) 802;
(c) A.A. Trifonov, M.N. Bochkarev, H. Schumann, S. Dechert, Z. Nat-
urforsch B 58 (2003) 389;
(d) G.B. Deacon, G. Meyer, D. Stellfeldt, Eur. J. Inorg. Chem (2000) 1061;
(e) E.N. Kirillov, A.A. Trifonov, S.E. Nefedov, I.L. Eremenko, F.T. Edel-
mann, M.N. Bochkarev, Z. Naturforsch B 54 (1999) 1379;
(f) N. Guiseppone, J. Collin, A. Domingos, I. Santos, J. Organomet. Chem
590 (1999) 248;
[1] (a) J. Scott, H. Fan, B.F. Wicker, A.R. Fout, M.-H. Baik, D.J. Mindiola, J. Am.
Chem. Soc 130 (2008) 14438;
(b) R. Litlabø, M. Zimmermann, K. Saliu, J. Takats, K.W. To¨rnroos, R.
Anwander, Angew. Chemie, Int. Ed 47 (2008) 9560;
(c) M. Zimmermann, J. Takats, G. Kiel, K.W. To¨rnoos, R. Anwander,
Chem. Commun. (2008) 612;
(d) H.M. Dietrich, K.W. To¨rnroos, R. Anwander, J. Am. Chem. Soc 128
(2006) 9298;
(g) Y. Yao, Q. Shen, J. Sun, Polyhedron 17 (1998) 519;
(h) Z. Hou, A. Fujita, T. Yoshimura, A. Jesorka, Y. Zhang, H. Yamazaki, Y.
Wakatsuki, Inorg. Chem 35 (1996) 7190.
(e) T. Cantat, F. Jaroschik, L. Ricard, P. Le Floch, F. Nief, N. Me´zailles,
Organometallics 25 (2006) 1329;
(f) L. Andrews, H.-G. Cho, Organometallics 25 (2006) 4040;
(g) T. Cantat, F. Jaroschik, F. Nief, L. Ricard, N. Me´zailles, P. Le Floch,
Chem Commun (2005) 5178;
[16] A. Fischbach, E. Herdtweck, R. Anwander, G. Eickerling, W. Scherer,
Organometallics 22 (2003) 499.
[17] G.W. Rabe, M. Zhang-Presse, F.A. Riederer, G.P.A. Yap, Inorg. Chem 42
(2003) 3527.
(h) K. Aparna, M. Ferguson, R.G. Cavell, J. Am. Chem. Soc 122 (2000)
726;
[18] K. Izod, S.T. Liddle, W. Clegg, Inorg. Chem 43 (2004) 214.
[19] (a) T.J. Boyle, S.D. Bunge, P.G. Clem, J. Richardson, J.T. Dawley, L.A.M.
Ottley, M.A. Rodriguez, B.A. Tuttle, G.R. Avilucea, R.G. Tissot, Inorg.
Chem 44 (2005) 1588;
(i) M.N. Bochkarev, A.V. Protchenko, L.N. Zakharov, G.K. Fukin, Y.T.
Struchkov, J. Organomet. Chem 501 (1995) 123;
(j) H. Schumann, J. Mu¨ ller, J. Organomet. Chem 169 (1979) C1.
[2] (a) N.D. Jones, R.G. Cavell, J. Organomet. Chem 690 (2005) 5485;
(b) R.G. Cavell, R.P. Kamalesh Babu, K. Aparna, J. Organomet. Chem
617–618 (2001) 158;
(c) R. Appel, I. Ruppert, Z. Anorg, Allg. Chem 406 (1974) 131.
[3] (a) A.J. Wooles, D.P. Mills, W. Lewis, A.J. Blake, S.T. Liddle, Dalton Trans
39 (2010) 500;
(b) Z. Xie, K. Chui, Q. Yang, T.C.W. Mak, J. Sun, Organometallics 17
(1998) 3937;
(c) D.L. Clark, J.C. Gordon, J.G. Watkin, J.C. Huffman, B.D. Zwick, Poly-
hedron 15 (1996) 2279;
(d) R.J. Butcher, D.L. Clark, S.K. Grumbine, R.L. Vincent-Hollis, B.L. Scott,
J.G. Watkin, Inorg. Chem 34 (1995) 5468;
(b) D.P. Mills, A.J. Wooles, J. McMaster, W. Lewis, A.J. Blake, S.T. Liddle,
Organometallics 28 (2009) 677;
(c) D.P. Mills, O.J. Cooper, J. McMaster, W. Lewis, S.T. Liddle, Dalton
Trans (2009) 4547;
(d) S.T. Liddle, D.P. Mills, B.M. Gardner, J. McMaster, C. Jones, W.D.
Woodul, Inorg. Chem 48 (2009) 3520;
(e) S.T. Liddle, J. McMaster, J.C. Green, P.L. Arnold, Chem. Commun
(2008) 1747.
(e) D.M. Barnhart, D.L. Clark, J.C. Gordon, J.C. Huffman, R.L. Vincent, J.G.
Watkin, B.D. Zwick, Inorg. Chem 33 (1994) 3487.
[20] T.J. Boyle, L.A.M. Ottley, Chem. Rev 108 (2008), 1896 and references
therein.
[21] T.J. Boyle, L.J. Tribby, S.D. Bunge, Eur. J. Inorg. Chem (2006) 4553.
[22] M. Schlosser, J. Hartmann, Angew. Chemie, Int. Ed 12 (1973) 508.
[23] Bruker smart and saint; Bruker AXS Inc., Madison, Wisconsin, 2001.
[24] G.M. Sheldrick, SHELXTL Acta Cryst. Sect. A 64 (2008) 112.
[25] A.L. Spek, University of Utrecht, The Netherlands, 2000.
[4] (a) L. Orzechowski, G. Jansen, M. Lutz, S. Harder, Dalton Trans. (2009)
2958;
(b) L. Orzechowski, S. Harder, Organometallics 26 (2007) 2144;