Synthesis, structure, and reactivity of cyclopentadienyl-free trimethylsilylmethyl yttrium di-tert-butylphenoxide complexes

Article abstract of DOI:10.1016/S0022-328X(98)00777-3

The chemistry of yttrium with the trimethylsilylmethyl/2,6-di-tert-butyl-phenoxide ligand combination has been examined. The anionic dialkyl-diaryloxide complexes, {(Me₃SiCH₂)₂Ln(OC₆H₃ ^tBu₂-2,6)₂}^- (Ln=Y, Lu), were prepared and their reactivity and that of the neutral dialkyl-aryloxide complex (Me₃SiCH₂)₂Y(OC₆H₃ ^tBu₂-2,6)(THF)₂, 1, has been studied and compared with cyclopentadienyl-containing organolanthanide complexes. {(Me₃SiCH₂)₂Y(OC₆H₃ ^tBu₂-2,6)₂}{[(THF)₃Li] ₂Cl}, 2, was prepared from the reaction of YCl₃ with two equivalents of LiCH₂SiMe₃ and two equivalents of LiOC₆H₃^tBu₂-2,6 and crystallized with an unusual cation which can be viewed as a LiCl adduct of [Li(THF)_x]⁺. [(Me₃SiCH₂)₂Lu(OC₆H₃ ^tBu₂-2,6)₂][Li(THF)₄](THF) ₂, 3, was prepared analogously and crystallized with a conventional cation. Both 2 and 3 have distorted tetrahedral coordination geometries around the metals. Ring-opening polymerization of ε-caprolactone was observed for 1-3, but only complex 1 was found to polymerize ethylene. NMR and mass spectroscopic analyses show that the more reactive complex 1 also exhibits metallation reactivity with pyridine, toluene, phenylacetylene, CH₃CN, Me₂CHCN, PhCN, and PhCH₂CN and insertion chemistry with Me₃CNC, CO, CO₂, PhNCO, and PhNCS. However, isolation of the organometallic products has been difficult due to the complexity of the reaction mixtures.

Full text of DOI:10.1016/S0022-328X(98)00777-3

Journal of Organometallic Chemistry 569 (1998) 89–97
Synthesis, structure, and reactivity of cyclopentadienyl-free
trimethylsilylmethyl yttrium di-tert-butylphenoxide complexes1
William J. Evans *, Randy N.R. Broomhall-Dillard, Joseph W. Ziller
Department of Chemistry, Uni6ersity of California, Ir6ine, Ir6ine, CA 92697, USA
Received 17 March 1998
Abstract
The chemistry of yttrium with the trimethylsilylmethyl/2,6-di-tert-butyl-phenoxide ligand combination has been examined. The
anionic dialkyl–diaryloxide complexes, {(Me3SiCH2)2Ln(OC6H3 Bu2-2,6)2}− (Ln=Y, Lu), were prepared and their reactivity and
t
t
that of the neutral dialkyl–aryloxide complex (Me3SiCH2)2Y(OC6H3 Bu2-2,6)(THF)2, 1, has been studied and compared with
t
cyclopentadienyl-containing organolanthanide complexes. {(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}{[(THF)3Li]2Cl}, 2, was prepared
t
from the reaction of YCl3 with two equivalents of LiCH2SiMe3 and two equivalents of LiOC6H3 Bu2-2,6 and crystallized with an
unusual cation which can be viewed as a LiCl adduct of [Li(THF)x]+. [(Me3SiCH2)2Lu(OC6H3 Bu2-2,6)2][Li(THF)4](THF)2, 3,
t
was prepared analogously and crystallized with a conventional cation. Both 2 and 3 have distorted tetrahedral coordination
geometries around the metals. Ring-opening polymerization of m-caprolactone was observed for 1–3, but only complex 1 was
found to polymerize ethylene. NMR and mass spectroscopic analyses show that the more reactive complex 1 also exhibits
metallation reactivity with pyridine, toluene, phenylacetylene, CH3CN, Me2CHCN, PhCN, and PhCH2CN and insertion
chemistry with Me3CNC, CO, CO2, PhNCO, and PhNCS. However, isolation of the organometallic products has been difficult
due to the complexity of the reaction mixtures. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Cyclopentadienyl-free; Trimethylsilylmethyl; Yttrium; Di-tert-butylphenoxide; Polymerization; Metallation
1. Introduction
alkoxide and aryloxide ligands are attractive because
they offer strong metal oxygen bonds which can stabi-
lize complexes of these electropositive metals, relatively
few alkyl complexes are known in which the only
supporting co-ligands are OR or OAr groups [34–38].
We are aware of only six examples in this class which
have been characterized by X-ray crystallography:
{(Me3SiCH2)x (Me3CO)1−x Y(v-OCMe3)4[Li(THF)]4
Currently, there is considerable interest [1,2] in devel-
oping the chemistry of organometallic yttrium and lan-
thanide alkyl and hydride complexes involving
solubilizing and stabilizing ancillary ligands other than
the commonly used cyclopentadienyl ligands [3–6].
Many types of alternative ancillary ligand systems have
been studied, including alkoxides and aryloxides [7–14],
cyclooctatetraenides [15], carboranes [16–18], polypyra-
zolylborates [19–23], amides [24,25], phosphides
[26,27], porphyrins [28], aza-crowns [29], benzamidi-
nates [30,31], and alkoxyamides [32,33]. Although
(v4-Cl)}[Y(CH2SiMe3)4]
[34],
(Me3SiCH2)Y[(v-
CH2)2SiMe2][(v-OCMe3)Li(THF)2]2 [35], [(Me3SiCH2)2-
Sm(OC6Hi3Pr2-2,6)3][Li(THF)]2 [36], [(Me3Si)2CH]La[v-
(OC6Ht2Bu2-4,6)2] [37], {[(Me3Si)2CH]2Y(vOCMe3)2}
t
{Li(THF)} [38], and (Me3SiCH2)2Y(OC6-H3 Bu2-2,6)
t
(THF)2 [38]. Since (Me3SiCH2)2Y(OC6H3 Bu2-2,6)
(THF)2, 1, can be synthesized by a straightforward
reagent-efficient route [38] (Eq. (1)), we have chosen to
examine its reactivity which includes polymerization,
metallation, and insertion reactions.
* Corresponding author. Tel.: +1 949 8245174; fax: +1 949
8242210; e-mail: wevans@uci.edu
1 Dedicated to Professor Akira Nakamura, whose broad contribu-
tions to organometallic chemistry have greatly enriched the field.
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00777-3

90
W.J. E6ans et al. / Journal of Organometallic Chemistry 569 (1998) 89–97
t
YCl3+2LiCH2SiMe3+LiOC6H3 Bu2-2,6
THF
LiCH2SiMe3 (0.150 g 1.593 mmol) was added to form a
slightly cloudy, pale yellow solution. After another 5
min, LiOC6H3 Bu2-2,6 (0.338 g, 1.593 mmol) was added
t
“ (Me3SiCH2)2Y(OC6H3 Bu2-2,6)(THF)2
(1)
t
t
Since this (Me3SiCH2)/(OC6H3 Bu2-2,6) ligand com-
bination provides a reactive complex, we have also
expanded on the synthetic chemistry of this ligand set.
The preparation of an anionic ‘ate’ complex was exam-
ined since this type of species is common in this area of
chemistry ([11]c, [34–36,38]) and such species could be
accessible from 1. Accordingly, the dialkyldiaryloxide
and the mixture was stirred for 12 h. THF was removed
from the slightly cloudy, pale yellow solution by rotary
evaporation and the resulting oily solid was extracted
with toluene (10 ml). The toluene soluble fraction was
separated by centrifugation from an off-white powder
and was dried to a white solid (0.010 g) which was
discarded. The off-white powder was extracted with
THF (10 ml) producing a pale yellow solution and a
white powder. The pale yellow solution was dried by
rotary evaporation to an off-white powder (0.703 g,
yttrium complex {(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}−
t
was synthesized. We also examined the lutetium analog,
[(Me3SiCH2)2Lu(OC6H3 Bu2-2,6)2]−, to verify the usual
t
t
assumption that yttrium and the late lanthanides are
similar and to determine if this heavier metal would be
advantageous in the characterization of reaction prod-
ucts [39]. The reaction chemistry of these ‘ate’ com-
plexes has also been examined and is compared with
that of 1.
85%), which analyzed for {(Me3SiCH2)2Y-(OC6H3 Bu2-
2,6)2}{[(THF)2Li]2Cl}(LiCl), i.e. the partially desol-
vated LiCl adduct of 2, see below. Anal Calc. for
C52H96YO6Si2Li3Cl2: C, 58.08; H, 9.00; Y, 8.27. Found:
C, 58.6; H, 9.0; Y, 8.5. Colorless crystals of
t
{(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}{[(THF)3Li]2Cl}, 2,
suitable for X-ray diffraction were grown from a con-
centrated THF solution at −38°C over a period of
1
2. Experimental section
several weeks. H-NMR (THF-d8) l 6.94 (d, 4H, m-
OC6Ht3 Bu2-2,6), 6.29 (t, 2H, p-OC6H3 Bu2-2,6), 1.46 (s,
t
t
All of the chemistry described below was performed
under nitrogen with rigorous exclusion of air and water
using standard Schlenk, vacuum line and glove box
techniques. Solvents, including C6D6 and THF-d8
(Cambridge Isotopes), were dried and distilled [40] and
36H, OC6H3 Bu2-2,6), −0.09 (s, 18H, CH2Si(CH3)3),
−0.57 (d, 4H, CH2SiMe3, JY–C–H=3.7 Hz). 13C-NMR
(THF-d8) l 164.2, 138.2, 124.5, 114.7 (phenoxide), 68.2
t
(THP), 35.6 (OC6H3 Bu2-2,6), 32.1 (CH2Si(CH3)3), 26.3
(THF), 4.9 (CH2Si(CH3)3). IR (KBr): 3072 w, 3053 w,
2952 s, 2886 m, 1582 w, 1459 w, 1410 s, 1384 m, 1355
w, 1263 s, 1235 w, 1199 w, 1104 w, 1044 s, 887 m, 861
YCl3 and LuCl3 (Rhoˆne-Poulenc) were dried [41] as
t
described
previously.
(Me3SiCH2)2Y(OC6H3 Bu2-
2,6)(THF)2, 1, was prepared as previously described
[38]. Ethylene, carbon monoxide, and hydrogen (re-
search grade, Matheson) were used as purchased. Car-
bon dioxide (99.999%, Matheson) was subjected to
three freeze–pump–thaw cycles before use. Pyridine
(Acros) was dried and distiled from CaH2 before use.
Toluene-d8 (Cambridge Isotopes), phenylacetylene, ace-
tonitrile, iso-propylnitrile, benzonitrile, phenylacetoni-
trile, tert-butyl-iso-nitrile, phenyl iso-cyanate, and
s, 820 m, 749 m, 655 w cm−1
.
2.2. Synthesis of
[(Me3SiCH2)2Lu(OC6H3 Bu2-2,6)2][Li(THF)4](THF)2, 3
t
In a glove box, LuCl3 (0.149 g, 0.531 mmol) was
added to THF (15 ml) and stirred. After 5 min,
LiCH2SiMe3 (0.100 g, 1.062 mmol) was added to form
a slightly cloudy, pale yellow solution. After another 5
t
˚
phenyl iso-thiocyanate (Acros) were dried over 4A
molecular sieves and vacuum distiled before use. H-
min, LiOC6H3 Bu2-2,6 (0.225, 1.062 mmol) was added
1
and the mixture was stirred for 12 h. THF was removed
from the slightly cloudy, pale yellow solution by rotary
evaporation, and the resulting oily solid was extracted
with toluene (10 ml). The toluene soluble fraction was
separated by centrifugation from an off-white powder
and was dried to a white solid (0.278 g, 50%), which
and 13C-NMR spectra were recorded on General Elec-
tric GN500, Omega 500, and Bruker DRX-400 spec-
trometers. Infrared spectra were obtained on Perkin
Elmer 1600 FTIR and MIDAC Prospect FTIR spec-
trophotometers. GC-MS data were obtained on a
Micromass Autospec instrument running in the EI
mode. Carbon and hydrogen analytical data were ob-
tained on a Carlo Erba EA1108 and metal analysis was
obtained by complexometric titration [42].
t
analyzed for [(Me3SiCH2)2Lu(OC6H3 Bu2-2,6)2][Li-
(THF)4](LiCl), the partially desolvated LiCl adduct of
3, see below. Anal. Calc. for C52H96LuO6Si2Li2Cl: C,
56.89; H, 8.81; Lu, 15.94. Found: C, 56.9; H, 8.4; Lu,
t
16.5. Colorless crystals of [(Me3SiCH2)2Lu(OC6H3 Bu2-
t
2.1. Synthesis of {(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}
{[(THF)3Li ]2Cl}, 2
2,6)2][Li(THF)4](THF)2, 3, suitable for X-ray diffrac-
tion were grown from a concentrated toluene–THF
solution at −38°C over a period of several weeks.
1H-NMR (THF-d8) l 6.93 (d, 4H, m-OC6H3 Bu2-2,6),
t
In a glove box, YCl3 (0.156 g, 0.797 mmol) was
added to THF (15 ml) and stirred. After 5 min,
t
6.28 (t, 2H, p-OC6H3 Bu2-2,6), 1.45 (s, 36H,

W.J. E6ans et al. / Journal of Organometallic Chemistry 569 (1998) 89–97
91
t
OC6H3 Bu2-2,6), −0.09 (s, 18H, CH2Si(CH3)3), −0.73
evaporation. The reaction products were extracted with
toluene and THF and analyzed by NMR and IR
spectroscopy. Since the spectroscopic data indicated
mixtures of products, elemental analysis on single pure
products was not obtainable.
For reactions with gaseous substrates, 1 (0.330–0.489
mmol) was dissolved in a mixture of toluene (10 ml)
and THF (1 ml) in a 50 ml round bottom flask
equipped with an adapter with a greaseless stopcock.
The flask was attached to a vacuum line, degassed, and
the substrate was admitted to a pressure of 1 atm. After
the solution was stirred for up to 12 h, the flask was
returned to the glove box and the solution was worked
up as described above.
(s, 4H, CH2SiMe3). 13C-NMR (THF-d8) l 138.4, 124.5,
114.7 (phenoxide), 68.2 (THF), 39.2, 35.6 (OC6H3 Bu2-
t
2,6),
32.1
(CH2Si(CH3)3),
26.4
(THF),
5.1
(CH2Si(CH3)3). IR (KBr): 3073 w, 3053 w, 2950 s, 2886
m, 1583 w, 1459 w, 1410 s, 1384 m, 1356 w, 1265 s,
1235 w, 1200 w, 1104 w, 1042 s, 867 s, 820 m, 749 m,
657 w cm−1
.
2.3. Reactions with m-caprolactone
In three separate reactions, m-caprolactone (ca. 2 ml,
18 mmol) was added to solutions of 0.025 g of 1 (0.041
mmol) in toluene (1 ml), 2 (0.022 mmol) in THF (1 ml),
and 3 (0.021 mmol) in toluene (1 ml). The solutions
were mixed, and rapidly (1–5 min) produced gelatinous
solids which hardened over 1 h to yellow poly(m-
caprolactone).
2.7. X-ray data collection, structure determination, and
t
refinement for {(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}
{[(THF)3Li ]2Cl}, 2
A colorless crystal of approximate dimensions 0.13×
0.37×0.58 mm was mounted on a glass fiber and
transferred to a Siemens P4 diffractometer. The deter-
mination of Laue symmetry, crystal class, unit cell
parameters and the crystal’s orientation matrix were
carried out according to standard procedures [43]. In-
tensity data were collected at 163 K using a 2q-ꢀ scan
technique with Mo–Kh radiation. The raw data were
processed with a local version of CARESS [44] which
employs a modified version of the Lehman–Larsen
algorithm to obtain intensities and standard deviations
from the measured 96-step peak profiles. Subsequent
calculations were carried out using the SHELXTL pro-
gram [45]. All 9394 data were corrected for absorption
[46] and for Lorentz and polarization effects and placed
on an approximately absolute scale. There were no
systematic absences nor any diffraction symmetry other
than the Friedel condition. The centrosymmetric tri-
2.4. Reaction of 1 with ethylene
Complex 1 (0.100 g, 0.163 mmol) was stirred under
ethylene (70 psi) in toluene (10 ml). After 18 h, brown–
white solids were present in the reaction vessel.
Methanol (15 ml) was added to the reaction mixture
followed by H2O (25 ml). Filtration and drying of the
off-white solids yielded 0.130 g of material insoluble in
hot toluene.
2.5. NMR tube reactions
For reactions with liquid substrates, 1 (0.015–0.110
mmol) was dissolved in a mixture of THF-d8 (ten
drops) and C6D6 (1 ml) in an NMR tube, and two
equivalents of substrate were added via a microsyringe.
The NMR tubes were evacuated to the vapor pressure
of the solvent and sealed. The H-NMR spectra were
taken after 30 min and were monitored for several
weeks.
1
(
clinic space group P1 was assigned and later deter-
mined to be correct. Experimental details appear in
Table 1.
For reactions with gaseous substrates, 1 (0.05 mmol)
was dissolved in a mixture of THF-d8 (ten drops) and
C6D6 (1 ml) in an NMR tube modified with a gas-inlet;
greaseless stopcock valve. The NMR tubes were at-
tached to a vacuum line, degassed by three freeze–
pump–thaw cycles, and the substrate was admitted to a
pressure of 1 atm. The tubes were sealed and the
1H-NMR spectra were taken after 30 min and were
monitored for several weeks.
The structure was solved by direct methods and
refined on F2 by full-matrix least-squares techniques.
The analytical scattering factors for neutral atoms were
used throughout the analysis [47]. Hydrogen atoms
were included using a riding model. Unfortunately, the
limited quality of the crystal prevented a better refine-
ment from being achieved. At convergence, wR2=
0.2036 and GOF=1.053 for 668 variables refined
against all 8866 unique data. (As a comparison for
refinement on F, R1=0.0758 for those 5199 data with
I\2.0|I.)
2.6. Preparati6e scale reactions
For reactions with liquid substrates, 1 (0.163–0.366
mmol) was dissolved in a mixture of toluene (10 ml)
and THF (1 ml). Two equivalents of substrate were
added via a microsyringe and the reactions were stirred
for up to 12 h. Volatiles were removed by rotary
2.8. X-ray data collection, structure determination, and
refinement for
[(Me3SiCH2)2Lu(OC6H3 Bu2-2,6)2][Li(THF)4](THF)2, 3
t
A colorless crystal of approximate dimensions 0.20

92
W.J. E6ans et al. / Journal of Organometallic Chemistry 569 (1998) 89–97
t
×0.23×0.30 mm was handled as described for 2. All
6025 data were corrected for Lorentz and polarization
effects, and were placed on an approximately absolute
scale. The diffraction symmetry was mmm with the
systematic and the systematic absences are consistent
with either space group Pna21 or Pnma. It was later
determined that the non-centrosymmetric space group
Pna21 was correct. At convergence, wR2=0.1781 and
GOF=1.013 for 314 variables refined against 6023
unique data. (As a comparison for refinement on F,
R1=0.0638 for those 3854 data with I\2.0|I.) The
high R value is indicative of poor crystal quality.
(Me3SiCH2)2Y(OC6H3 Bu2-2,6)(THF)2,
1,
readily
formed with this ‘small alkyl–large aryloxide’ ligand
combination according to Eq. (1) [38]. In contrast, the
combination of the larger alkyl, (Me3Si)2CH, and the
alkoxide, OCMe3, preferentially formed the anionic,
tetra-ligand ‘ate’ complex [(Me3Si)2CH]2Y(v-OCMe3)2-
Li(THF), as shown in Eq. (2) [38].
YCl3+2 LiCH(SiMe3)2+2 LiOCMe3
THF
“ [(Me3Si)2CH]2Y(v-OCMe3)2Li(THF)
(2)
To determine if an anionic complex analogous to
that in Eq. (2) could be made with the (Me3SiCH2)–
t
(OC6H3 Bu2-2,6) ligand combination, the reaction of
3. Results and discussion
YCl3 with two equivalents of LiCH2SiMe3 and two
t
equivalents of LiOC6H3 Bu2-2,6 in THF was conducted.
3.1. Synthesis
The H- and 13C-NMR data on the THF soluble reac-
1
tion product were consistent with the presence of the
Previous studies of yttrium alkyl alkoxide and ary-
loxide complexes showed that the neutral complex
anticipated
dialkyl–diaryloxide
complex,
{(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}−: the alkyl and ary-
loxide ligands were present in a 1:1 ratio and the
methylene resonance due to the CH2SiMe3 groups was
a doublet which displayed characteristic yttrium cou-
pling with JY–C–H=3.7 Hz [35,38,48–50]. Although
the anionic organometallic portion of 2 was easily
characterized by NMR, little information could be
obtained about the cation in solution. Moreover, ele-
mental analysis of the crude product indicated the
presence of LiCl as a contaminant. Since the complex
was only soluble in THF, complete separation of the
LiCl was difficult. However, recrystallization of this
material led to the isolation of the desired complex
t
Table 1
Experimental data for the X-ray diffraction studies of {(Me3SiCH2)2-
t
Y(OC6H3 Bu2-2,6)2}{[(THF)3Li]2CI}, 2, and (Me3SiCH2)2Lu(OC6-
t
H3 Bu2-2,6)2}[Li(THF)4](THF)2, 3
Compound
2
3
Formula
C60H112ClLi2O8Si2Y
1155.92
163
Triclinic
P1
11.543(10)
16.335(12)
18.99(2)
94.42(6)
97.19(3)
106.07(5)
3390(5)
C
60H112LiO8Si2Lu
Formula weight
Temperature (K)
Crystal system
Space group
1199.59
158
Orthorhombic
Pna21
20.760(4)
16.557(8)
19.327(6)
90
90
90
6644(4)
4
1.199
(
˚
a (A)
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
which
formed
with
the
unusual
cation
{[(THF)3Li]2Cl}+ (Eq. (3)).
THF
YCl3+2 LiCH2SiMe3+2 LiOC6H3 Bu2-2,6 “
3
˚
t
V (A )
Z
2
Dcalc. (g cm−3
q Range (°)
)
1.132
2.00–22.50
0.981
{(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}−{[(THF)3Li]2Cl}+
2
t
2.11–25.0
1.568
(3)
v(Mo–Kh) (mm−1
)
Reflections collected
Independent reflec-
tions
Observed reflections
(I\2|I)
Data/restraints/
parameters
Goodness-of-fit
Final R indices
(I\2|I)a
9394
6025
A reaction analogous to Eq. (3) was examined with
lutetium to determine if the chemistry paralleled that of
yttrium. This is usually the case [39], but detailed
comparisons had not been made in an alkyl alkoxide or
aryloxide system. Since these systems proved to be
challenging (see below), we sought to determine if
lutetium would offer any advantages. The reaction of
LuCl3 with two equivalents of LiCH2SiMe3 and two
8866 (Rint=0.0495)
6025 (Rint=0.000)
5199
6023
8866/0/668
6023/1/314
1.053
1.013
R1=0.0758,
wR2=0.1695
R1=0.1465,
wR2=0.2036
R1=0.0638,
wR2=0.0477
R1=0.1151,
wR2=0.0781
None
t
R indices (all data)
equivalents of LiOC6H3 Bu2-2,6 in THF formed a
product whose NMR spectra were consistent with the
presence of the analogous anionic dialkyl–diaryloxide
Absorption correction Semi-empirical from
„-scans
complex, {[Me3SiCH2]2Lu(OC6H3 Bu2-2,6)2}−. The 1H-
t
˚
Diffractometer, Siemens P4; radiation, Mo–Kh (u=0.710730 A).
NMR spectrum of the lutetium product is very similar
to that of 2 except that the methylene resonance is
shifted slightly upfield and displays no metal-to-alkyl
coupling as expected for lutetium in comparison to
Monochomator, highly oriented graphite.
Scan type, 2q-ꢀ; scan width, 1.2°; scan speed, 3.0° min−1
a R1=SꢀFoꢁ−ꢁFcꢀ/SꢁFoꢁ.
.
wR2=[S[w(F2o−F2c)2/S{w(Fo2)2}]1/2
.

W.J. E6ans et al. / Journal of Organometallic Chemistry 569 (1998) 89–97
93
t
˚
Table 2
2.094(3) A Y–O(OC6H3 Bu2-2,6) distance in 2 is also
˚
Selected bond distances (A) and angles (°) for {(Me3SiCH2)2Y-
equivalent within error limits to the analogous Y–O
lengths in structures of other coordination numbers: 1
(2.084(11) A) [38], Y(OC6H3 Bu2-2,6)3 (2.00(2) A)
([13]b), and (C5Me5)Y(OC6H3 Bu2-2,6)2 (2.096(4) and
t
(OC6H3 Bu2-2,6)2}{[(THF)3Li]2Cl}, 2, and {(Me3SiCH2)2Lu(OC6-
t
H3 Bu2-2,6)2}[Li(THF)4](THF)2, 3
t
˚
˚
t
Complex 2
Complex 3
˚
2.059(3) A) ([14]a).
Y(1)–O(1)
Y(1)–O(2)
Y(1)–C(29)
Y(1)–C(33)
Si(1)–C(29)
Si(2)–C(33)
2.091(5)
2.097(5)
2.404(8)
2.420(8)
1.843(9)
1.835(8)
Lu(1)–O(1)
Lu(1)–O(2)
Lu(1)–C(29)
Lu(1)–C(33)
Si(1)–C(29)
Si(2)–C(33)
2.079(8)
2.075(9)
2.42(3)
2.29(2)
1.83(2)
1.85(2)
The lutetium aryloxide and alkyl bond distances in 3
(Fig. 2) are similar to those in 2 when differences in
ionic radii are taken into consideration [51]. The aver-
age Lu–C(CH2SiMe3) bond distance of 2.36(7) A in 3
is consistent with the analogous distances in
(C5H5)2Lu(CH2SiMe3)(THF) (2.376(17) A) [52], and the
2.329(15) A average distance for the two independent
molecules of {(C5Me5)Lu(CH2SiMe3)[CH(SiMe3)2]Cl}
{Li(THF)2} [53].
Although the structures of the organometallic anions
of 2 and 3 are similar, different cations are found in the
crystals isolated for X-ray crystallography. The
[Li(THF)4]+ cation in 3 is conventional and consists of
a lithium atom tetrahedrally coordinated by four THF
ligands with normal Li–O bond distances. However, in
complex 2 a {[(THF)3Li]2Cl}+ cation is isolated. This
species is effectively a LiCl adduct of the [Li(THF)4]+
cation in 3. It consists of two lithium atoms tetrahe-
drally coordinated by three THF ligands and linked by
a bridging chloride atom with a Li–Cl–Li angle of
˚
˚
O(1)–Y(1)–O(2)
O(1)–Y(1)–C(29)
O(1)–Y(1)–C(33)
O(2)–Y(1)–C(29)
O(2)–Y(1)–C(33)
110.9(2)
111.4(2)
108.0(2)
107.8(2)
114.0(2)
O(1)–Lu(1)–O(2)
110.4(3)
˚
O(1)–Lu(1)–C(29) 112.6(7)
O(1)–Lu(1)–C(33) 109.3(7)
O(2)–Lu(1)–C(29) 105.8(8)
O(2)–Lu(1)–C(33) 115.1(7)
C(29)–Lu(1)–C(33) 103.5(5)
C(29)–Y(1)–C(33) 104.5(3)
Li(1)–Cl(1)
Li(2)–Cl(1)
Li(1)–O(3)
Li(1)–O(4)
Li(1)–O(5)
Li(2)–O(6)
Li(2)–O(7)
Li(2)–O(8)
2.263(13)
2.27(2)
1.90(2)
1.98(2)
1.92(2)
1.94(2)
1.93(2)
1.98(2)
Li(1)–O(3)
Li(1)–O(4)
Li(1)–O(5)
Li(1)–O(6)
1.93(4)
1.83(4)
2.04(4)
1.74(4)
Li(1)–Cl(1)–Li(2)
151.9(6)
yttrium. As in the yttrium synthesis, the crude product
had analytical data which indicated contamination with
LiCl. However, since this lutetium product was soluble
in toluene, recrystallization gave a LiCl-free product
with a conventional [Li(THF)4]+ counter-cation as
shown in Eq. (4).
˚
151.9(6)° and an average Li–Cl distance of 2.267(4) A.
This cation has been previously observed in
{[(C5H5)2Zr(PPh)]2}{[(THF)3Li]2Cl} [54], but in this
case the cation has a 180° Li–Cl–Li angle and equiva-
˚
lent Li–Cl distances of 2.246(17) A.
THF
t
3.3. Reacti6ity
LuCl3+2 LiCH2SiMe3+2 LiOC6H3 Bu2-2,6 “
[(Me3SiCH2)2Lu(OC6H3 Bu2-2,6)2]−[Li(THF)4]+(THF)2
t
The reactivity of complexes 1–3 was examined with a
variety of substrates whose reaction chemistry with
cyclopentadienyl-containing alkyl complexes is well
characterized [4–6]. Each of the complexes 1–3 was
observed to polymerize m-caprolactone. This is not un-
usual reactivity considering that both alkyl and alkox-
ide complexes of electropositive metals ring open
polymerize this substrate [55]. Reactivity with ethylene,
a substrate also readily polymerized by cyclopentadi-
enyl-containing lanthanide alkyls [56], was more lim-
ited. Only the neutral complex (Me3SiCH2)2Y(OC6-
(4)
3.2. Structure
Complexes 2 and 3 crystallize with nearly identical
four coordinate, distorted tetrahedral geometries
around yttrium and lutetium, respectively. The respec-
tive yttrium and lutetium O(1)–Ln–O(2) angles of
110.9(2) and 110.4(3)° and the C(29)–Ln–C(33) angles
of 104.5(3) and 103.5(5)° in complexes 2 and 3 are
within experimental error (Table 2).
t
H3 Bu2-2,6)(THF)2, 1, was observed to initiate the poly-
˚
The 2.404(4) and 2.420(8) A Y–C(CH2SiMe3) bond
merization of ethylene. Complex 1 did not initiate the
polymerization of butadiene at 15 psi or propylene at
60 psi at room temperature.
lengths in 2 (Fig. 1) are within the error limits of the
analogous distances in five coordinate (Me3SiCH2)2Y-
t
˚
(OC6H3 Bu2-2,6)(THF)2, 1 (2.411(13) and 2.427(16) A)
Further reactivity studies with this alkyl/aryloxide
ligand combination were confined to 1 since it was
found to be the most reactive and since it was found
that the lithium aryloxide complex [(THF)Li(OC6-
[38], and are similar to those in four coordinate
[Y(CH2SiMe3)4]− (2.382(8)–2.420(9) A), eight coordi-
˚
nate [(CsH5)2Y(CH2SiMe3)2]− (2.42(2)
A
average)
˚
([48]a), and seven coordinate (4,13-diaza-18-crown-
t
˚
6)Y(CH2SiMe3) (2.45(2) A) ([29]a). The average
H3 Bu2-2,6)]2 [57], readily forms in these systems. Since

94
W.J. E6ans et al. / Journal of Organometallic Chemistry 569 (1998) 89–97
t
Fig. 1. Thermal ellipsoid plot of {(Me3SiCH2)2Y(OC6H3 Bu2-2,6)2}{[(THF)3Li]2Cl}, 2, drawn at the 50% probability level.
Me3SiCH2CO]2, and Me3SiCH2CO2H were observed.
The fact that these insertion coupled products have no
deuterium indicates that the ligands formed by insertion
react with hydrogen sources in the system and are lost
from the metal before deuterolysis. This is consistent
this lithium complex often is the first product to crystal-
lize from solution, the lithium-containing anions 2 and
3 were less desirable for reactivity studies. This also
made it necessary to prepare 1 with exact reagent
stoichiometries.
1
with the complexity observed in H-NMR spectra of
these reaction products.
Complex 1 exhibits metallation reactivity with pheny-
lacetylene and pyridine as determined by the formation
1
Insertion chemistry also occurs with 1 and PhNCO
of Me4Si in the H-NMR spectra of reaction mixtures
1
and PhNCS. H-NMR analysis shows that these reac-
and by the loss of Y–C–H coupling in the CH2SiMe3
resonance. The product mixture obtained from the
phenylacetylene reaction exhibited an infrared absorp-
tion at 2047 cm−1, which is consistent with the pres-
tions are rapid and inserted products PhN(H)C(ꢁO)-
CH2SiMe3 and PhN(H)C(ꢁS)CH2SiMe3 were found in
the mass spectra of the deuterolyzed products. Ligand
fragmentation resulting in loss of SiMe3 was also found
in these systems, since PhN(H)C(ꢁO)CH3 and
PhN(H)C(ꢁS)CH3 were identified among the reaction
products. Both the lack of deuterium incorporation
into the inserted products and the ligand fragmentation
are consistent with the high degree of reactivity in these
systems and with the fact that inserted organometallic
products were not isolated for analysis by X-ray crys-
tallography.
ence of
a
(CꢀCPh)− ligand. Unfortunately, the
1H-NMR spectra of these products contained several
resonances in the aromatic region and a single metal-
lated product could not be isolated from either reac-
tion. Even at lowered temperatures complicated
product mixtures were observed. Control reactions
showed no evidence for metallation of the toluene
solvent (or benzene or THF) at room temperature.
Complex 1 also forms SiMe4 when it is treated with
nitriles, RCN (R=Me, Me2CH, Ph, PhCH2). However,
these reactions appeared to be even more complicated
than the other metallations.
Complex 1 was found to have reactivity comparable
with that of the most reactive of cyclopentadienyl lan-
thanide and yttrium alkyl complexes. Although metal-
lation of PhCꢀCH is quite facile with a variety of
cyclopentadienyl-containing lanthanide alkyl complexes
[58–61], metallation of pyridine ([61]a, [62–64]) and
acetonitrile [65,66] has been observed only for the more
reactive C5Me5-supported alkyls, (C5Me5)2LnR(THF)x
t
When 1 was treated with BuNC, CO, and CO2, the
1H-NMR spectra revealed rapid loss of the yttrium-
alkyl coupling and a downfield shift of the methylene
resonances in each case. The alkyl and aryloxide reso-
nances were broad in these spectra suggesting the pres-
ence of many products and single organometallic
products were not isolated. Evidence for insertion of
each of these substrates into the Y–CH2SiMe3 bond of
1 was obtained from the mass spectra of deuterolyzed
reaction mixtures. Signals for Me3SiCH2C(H)ꢁNCMe3,
t
(x=0 ,1). The insertion of BuNC [66–68], Co [64,69],
and CO2 [68,70–72] in Ln–R bonds has also been
previously observed in cyclopentadienyl-containing lan-
thanide alkyl complexes, but these reactions often are
less complicated and give better yields of a single

W.J. E6ans et al. / Journal of Organometallic Chemistry 569 (1998) 89–97
95
t
Fig. 2. Ball and stick plot of {(Me3SiCH2)2Lu(OC6H3 Bu2-2,6)2}[Li(THF)4](THF)2, 3.
References
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containing lanthanide alkyls [4–6], no reaction was
observed between 1 and H2 in either toluene or THF at
ambient temperatures. Reduced reactivity of alkyls to
hydrogen in alkoxide-substituted complexes has been
observed previously ([9]b, [14]a).
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Acknowledgements
For support of this research, we thank the Division
of Chemical Sciences of the Office of Basic Energy
Sciences of the Department of Energy.

96
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