Half-sandwich dibenzyl complexes of scandium: Synthesis, structure, and styrene polymerization activity

Article abstract of DOI:10.1016/j.jorganchem.2007.06.020

Half-sandwich dibenzyl complexes of scandium have been prepared by stepwise treatment of scandium trichloride with lithium derivatives of silyl-functionalized tetramethylcyclopentadienes (C₅Me₄H)SiMe₂R (R = Me, Ph) and benzyl magnesium chloride. The resulting complexes [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)₂(THF)] and [Sc(η⁵-C₅Me₄SiMe₂Ph)(CH₂Ph)₂(1,4-dioxane)] show structure related to that of the corresponding bis(trimethylsilylmethyl) compounds [Sc(η⁵-C₅Me₄SiMe₂R)(CH₂SiMe₃)₂(THF)]. The four-coordinate complexes display η¹-coordinated benzyl ligands without significant interaction of the ipso-carbon of the phenyl moiety. Conversion of [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)₂(THF)] into the cationic species by treatment with triphenylborane in THF led to the formation of a stable charge separated complex [Sc(η⁵-C₅Me₄SiMe₃)(CH₂Ph)(THF)_x][BPh₃(CH₂Ph)]. Benzyl cation formed using [Ph₃C][B(C₆F₅)₄] in toluene resulted in a moderately active syndiospecific styrene polymerization catalyst.

Full text of DOI:10.1016/j.jorganchem.2007.06.020

Journal of Organometallic Chemistry 692 (2007) 4702–4707
www.elsevier.com/locate/jorganchem
Half-sandwich dibenzyl complexes of scandium: Synthesis,
structure, and styrene polymerization activity
*
Julia Hitzbleck, Klaus Beckerle, Jun Okuda
Institute of Inorganic Chemistry, RWTH Aachen University, Landoltweg 1, 52072 Aachen, Germany
Received 31 March 2007; received in revised form 4 June 2007; accepted 12 June 2007
Available online 23 June 2007
Abstract
Half-sandwich dibenzyl complexes of scandium have been prepared by stepwise treatment of scandium trichloride with lithium deriv-
atives of silyl-functionalized tetramethylcyclopentadienes (C5Me4H)SiMe2R (R = Me, Ph) and benzyl magnesium chloride. The resulting
complexes [Sc(g5-C5Me4SiMe3)(CH2Ph)2(THF)] and [Sc(g5-C5Me4SiMe2Ph)(CH2Ph)2(1,4-dioxane)] show structure related to that of
the corresponding bis(trimethylsilylmethyl) compounds [Sc(g5-C5Me4SiMe2R)(CH2SiMe3)2(THF)]. The four-coordinate complexes dis-
play g1-coordinated benzyl ligands without significant interaction of the ipso-carbon of the phenyl moiety. Conversion of [Sc(g5-
C5Me4SiMe3)(CH2Ph)2(THF)] into the cationic species by treatment with triphenylborane in THF led to the formation of a stable charge
separated complex [Sc(g5-C5Me4SiMe3)(CH2Ph)(THF)x][BPh3(CH2Ph)]. Benzyl cation formed using [Ph3C][B(C6F5)4] in toluene
resulted in a moderately active syndiospecific styrene polymerization catalyst.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Scandium; Benzyl complexes; Styrene polymerization; Metallocene catalysis
1. Introduction
the synthesis and structural characterization of scandium
half-sandwich dibenzyl complexes as well as their activity
as styrene polymerization catalysts.
Half-sandwich complexes of scandium have attracted
interest in the recent past as homogeneous polymerization
catalyst precursors for various olefinic monomers [1,2]. A
series of studies investigated the influence of ligand substi-
tution patterns on the polymerization activity and selectiv-
ity of these complexes [2]. Being electronically and
sterically more unsaturated when compared with metallo-
cene compounds, the combination of a bulky cyclopenta-
dienyl ligand with stabilizing alkyl groups such as
CH2SiMe3 or CH(SiMe3)2 was instrumental in developing
the chemistry of half-sandwich complexes of scandium
[1]. Only few structurally characterized benzyl complexes
of the rare-earth metals have been reported up to date
[2e,3], in contrast to the numerous half-sandwich benzyl
complexes of the group 4 metals [4]. We report here on
2. Results and discussion
2.1. Synthesis of dibenzyl complexes
Scandium half-sandwich complexes were obtained by
salt metathesis of the corresponding lithium tetramethyl-
cyclopentadienide [Li(C5Me4SiMe2R)] (R = Me, Ph) [5]
with anhydrous scandium trichloride in THF. The dichloro
complex [Sc(g5-C5Me4SiMe3)Cl2(THF)2] (1) was isolated
by extraction with pentane, whereas the SiMe2Ph substi-
tuted complex was prepared in situ. Addition of 2 equiv
of Grignard reagent [(PhCH2)MgCl(THF)x] to 1 at low
temperature followed by extraction with warm toluene
afforded [Sc(g5-C5Me4SiMe3)(CH2Ph)2(THF)] (2). The
slightly lower solubility of the analogous SiMe2Ph substi-
tuted complex required the precipitation of the magnesium
chloride by addition of 1,4-dioxane from the concentrated
*
Corresponding author. Tel.: +49 241 80 94645; fax: +49 241 80 92644.
E-mail address: jun.okuda@ac.rwth-aachen.de (J. Okuda).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.06.020

J. Hitzbleck et al. / Journal of Organometallic Chemistry 692 (2007) 4702–4707
4703
SiMe2R
SiMe2R
[ScCl3]
+
1) THF
1) 2 PhCH2MgCl/THF
Sc
Sc
Cl
THF
L
2) pentane
2) toluene
THF
[Li(C5Me4SiMe2R)]
R = Me, Ph
Cl
R = Me, 1
R = Me; L = THF, 2;
R = Ph; L = 1,4-dioxane, 3
Scheme 1.
1
THF solution. This work-up led to the isolation of the cor-
responding 1,4-dioxane containing complex [Sc(g5-
C5Me4SiMe2Ph)(CH2Ph)2(1,4-dioxane)] (3) (Scheme 1).
signals with a strong temperature dependence of the H
NMR chemical shift for the methylene protons. Heating
to temperature above ambient resulted in decomposition.
2.2. Structural characterization
2.2.2. Crystal structure analysis
Recrystallization of the compounds 2 and 3 from tolu-
ene led to isolation of single crystals suitable for X-ray dif-
fraction analysis. The solid state structures confirm the
composition and structure derived from 1H NMR spectro-
scopic data in solution. Perspective views of complexes 2
and 3 are shown in Fig. 1, Table 1 contains details regard-
ing the diffraction data and Table 2 compiles pertinent
bond parameters.
The compounds have been characterized by NMR spec-
troscopic and analytical methods. Elemental analysis of the
benzyl compounds 2 and 3 gave repeatedly poor results
with largely differing values for the carbon content for
identical crystalline samples. Complexometric titrations
showed scandium content in agreement with the calculated
values.
Both complexes 2 and 3 show the typical piano stool
geometry of half-sandwich complexes. The cyclopentadien-
yl ring is located on the apical position of a pseudo-tetra-
hedral coordination environment around the scandium
2.2.1. NMR spectroscopy
The dibenzyl complexes 2 and 3 show broad signals for
the benzylic protons at ambient temperature (1.80,
2.14 ppm for 2; 1.91, 2.23 ppm for 3), partially overlapping
with the signals of the methyl substituents on the cyclopen-
tadienyl ring. Cooling of a sample of 2 to ꢀ40 ꢁC resulted
in splitting of the broad signal for the diastereotopic meth-
ylene groups into an AB pattern (1.87, 2.15 ppm,
˚
˚
metal center (Sc–C(cent) 2.172 A 2, 2.163 A for 3), the two
benzyl ligands and the donor (THF 2, 1,4-dioxane 3) are
in the basal plane of the coordination sphere. The angles
between these ligands are roughly equal in case of the diox-
ane donor (103.1 1.0ꢁ for 3), whilst the smaller steric
demand of the THF donor results in slightly larger devia-
tions (102.5 3.5ꢁ for 2). The Sc–O bond distances are
1
2JHH = 9.6 Hz, 2). The H and 13C NMR spectroscopic
data are in agreement with those of other structurally char-
acterized scandium benzyl compounds and indicate r-
bonded benzyl groups in solution (chemical shift for benzyl
Cipso at 152.5 ppm for both 2 and 3) [3,6].
The ether coordination at the scandium metal center is
labile in solution at room temperature, resulting in broad
˚
similar in 2 and 3 (Sc–O(THF) 2.153(3) A, Sc–O(dioxane)
˚
2.139(2) A), albeit compound 3 exhibits somewhat shorter
scandium-ligand contacts. Due to the small size and the
steric saturation of the scandium metal center, the benzyl
ligands coordinate in a r-bond fashion (Sc–C 2.289(5),
Fig. 1. Molecular structure of [Sc(g5-C5Me4SiMe3) (CH2Ph)2(THF)] (2) and [Sc(g5-C5Me4 SiMe2Ph)(CH2Ph)2(1,4-dioxane)] (3).

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J. Hitzbleck et al. / Journal of Organometallic Chemistry 692 (2007) 4702–4707
Table 1
dium metal center (Cipso–C(21)–Sc 113.76ꢁ, 113.29ꢁ for 2;
117.39ꢁ, 117.42ꢁ for 3).
Experimental data for the crystal structure determination of the complexes
2 and 3
One benzyl-scandium distance is shorter in each com-
2
3
˚
˚
plex (D = 0.020 A 2, 0.024 A 3), a feature also reported in
the structurally related scandium b-diketiminato complex
[Sc(L)(CH2Ph)2] (L = C{C(tBu)N(2,6-iPr–C6H3)}2) [3g],
displaying an even larger difference with Sc–C distances
Crystal data
Formula
Formula weight
Crystal color
Crystal size, mm
Space group
C30H43OScSi
492.69
Colorless
C35H45O2ScSi
570.76
Colorless
˚
˚
of 2.203(7) A and 2.265(6) A. The analogous contact ion
pair
0.46 · 0.35 · 0.13 0.24 · 0.16 · 0.09
½ScfðL0Þðg1-CH2PhÞgfðg6-PhCH2ÞBðC6F5Þ3gꢁðL0 ¼
P21/c (no. 14)
20.421(8)
9.330(4)
15.101(6)
101.143(10)
2823(2)
P21/n (no. 14)
8.8054(18)
17.230(3)
21.313(4)
101.49(3)
3168.7(11)
4
˚
a (A)
CfCðMeÞNð2; 6-iPr–C6H3Þg2Þ on the other hand shows
˚
b (A)
˚
an intermediate Sc–C distance of 2.229(2) A despite the
˚
c (A)
charge effect in the cationic metal center [3e]. Other
structurally characterized benzyl complexes of the rare-
earth metals are [Ln(g5-C5Me5)(CH2Ph)2(THF)](Ln =
Y, Gd), [{Sm(g5-C5Me5)2((g6-CH2Ph)2K(THF)2}x] [3c],
[Ln(g5-C5Me5)2(CH2Ph)(THF)] (Ln = Ce,Sm) [3a,3b],
[(TMEDA)Y(CH2Ph)2Br2Li(TMEDA)] [3d], [Li{PhC(N-
b (ꢁ)
3
˚
V (A )
Z
4
l(Mo Ka) (mmꢀ1
)
0.322
0.299
Data collection
T, K
130(2)
0.71073
2.41–25.00
h, ꢀ23 to 24;
k, ꢀ11 to 10;
l, ꢀ11 to 17
120(2)
0.71073
2.28–25.00
h, ꢀ10 to 10;
k, ꢀ16 to 20;
l, ꢀ25 to 25
˚
k (A)
SiMe3)N(CH2)2NMe2}2Y(CH2Ph)2],
[(PhC(NSiMe3)N-
h Range
Index ranges
(CH2)3NMe2)2Y(CH2Ph)] [3f], [Y(C{CH2N(2,6-iPr–C6-
H3)}2) (THF)2(CH2Ph)] [3i], and [La(CH2Ph)3(THF)3] [3j].
2.3. Styrene polymerization activity
Solution and refinement
Number of reflections measured
Number of independent
reflections
16505
4950
21078
5591
For further investigation of the structure of the active
species in polymerization catalysis, compound 2 has been
converted into the corresponding cationic species. Addition
of BPh3 to a solution of 2 in THF led to fast transfer of one
benzyl ligand to boron under formation of the THF sol-
vated, charge separated ion pair [Sc(g5-C5Me4Si-
Me3)(CH2Ph)(THF)x][BPh3(CH2Ph)] (4). The NMR
spectroscopic data indicate again a r-bonded benzyl group
Number of observed reflections
Goodness-of-fit
3407 (I > 2r(I))
1.077
3912 (I > 2r(I))
1.030
0.0559, 0.1104
Final R indices Ra1, wR2b (observed 0.0868, 0.2081
data)
Final R indices Ra1, wR2b (all data) 0.1224, 0.2290
Largest e-maximum, e-minimum, 1.093, ꢀ0.538
0.0899, 0.1233
0.315, ꢀ0.338
ꢀ3
˚
e A
a
R(F) = RiFoj ꢀ j Fci/RjFoj.
remaining on the scandium metal center, while the other
2
2 1=2
b
RwðFÞ ¼ ½RðF2o ꢀ Fc2Þ =RwðF2oÞ ꢁ
.
1
benzyl ligand is bound to boron (2JBH = 5.3 Hz; JBC
=
35.6 Hz) (Scheme 2).
The dibenzyl compound 2 has been tested as a catalyst
for styrene polymerization (Scheme 3). Upon activation
with 1 equiv of trityl borate [Ph3C][B(C6F5)4] the resulting
cationic species showed syndiospecific polymerization
Table 2
Selected bond distances [A] and angles [ꢁ] of the complexes 2 and 3
˚
activity for styrene. The activity for
2 of 5.0 kg
2
3
(sPS) mol(Sc)ꢀ1 hꢀ1) was lower in comparison to the trim-
ethylsilylmethyl complex [Sc(g5-C5Me4SiMe3)(CH2Si-
Me3)2(THF)] (6.3 · 103 kg(sPS) mol(Sc)ꢀ1 hꢀ1) under the
same conditions [2g], [7]. The polystyrene obtained was
syndiotactic according to 13C NMR spectroscopic analysis
and melting temperature of between 267 and 273 ꢁC
(DSC). The poorer styrene polymerization activity of 2 in
comparison with the analogous trimethylsilylmethyl com-
plex could be ascribed to the higher tendency of the benzyl
ligand to coordinate to the metal center in the correspond-
ing cationic species. Under polymerization conditions, in a
weakly coordinating solvent such as toluene, the size of the
active site on the metal center would thus be decreased
compared to the alkyl complex and the monomer insertion
impeded. Precedence for such a behavior was reported by
Piers and co-workers for the scandium b-diketiminato dib-
enzyl complexes, which tend to form contact ion pairs
upon addition of B(C6F5)3 in non-coordinating solvents
Sc–C(21)
Sc–C(31)
Sc–O(41)
Sc–C(1)
Sc–C(2)
Sc–C(3)
Sc–C(4)
Sc–C(5)
2.289(5)
2.267(5)
2.153(3)
2.476(5)
2.493(5)
2.494(5)
2.500(5)
2.476(5)
2.279(3)
2.255(3)
2.139(2)
2.448(3)
2.466(3)
2.521(3)
2.496(3)
2.473(3)
C(21)–Sc–C(31)
C(21)–Sc–O(41)
C(31)–Sc–O(41)
105.38(19)
97.96(15)
104.17(15)
104.16(12)
102.80(10)
103.25(10)
˚
2.268(5) 2, 2.279(3), 2.255(3) A for 3) and no significant
interaction with the ipso-carbon atom of the phenyl ring
˚
can be detected (Sc–C 3.184, 3.152 A for 2, 3.200,
1
˚
3.245 A for 3). The g -coordination is also confirmed by
the rather wide angle between the phenyl ring and the scan-

J. Hitzbleck et al. / Journal of Organometallic Chemistry 692 (2007) 4702–4707
4705
SiMe3
SiMe3
BPh3
THF
Sc
Sc
[BPh3(CH2Ph)]
(THF)x
THF
2
4
Scheme 2.
SiMe3
SiMe3
[Ph3C][B(C6F5)4]
syndiotactic
polystyrene
Sc
Sc
[B(C6F5)4] -
THF
toluene
- Ph3CCH2Ph
THF
H2C
2
Scheme 3.
[3e]. The abstracted benzyl group remains in close proxim-
ity to the metal center by a g6-bonding interaction.
Activation of the dichloro complex 1 with MAO under
polymerization conditions analogous to the standard
[Ti(g5-C5Me5)Cl3] catalyst system [8] resulted only in a
small amount of atactic polystyrene [9]. Cationic rare earth
metal complexes are often discussed as isostructural models
of the active species in syndiospecific styrene polymeriza-
tion [Ti(g5-C5Me5)Me]+ [10]. The scandium system exhib-
its differing reactivity in the presence of excess of aluminum
alkyl. We could recently show that the related bis(alkyl)
complex [Sc(g5-C5Me4SiMe2(C6F5))(CH2SiMe3)2(THF)],
which has polymerization activity comparable to the
[Sc(g5-C5Me4SiMe3)(CH2SiMe3)2(THF)], also produces
only small amounts of aPS in the presence of MAO
[11].
titration [13]. The substituted cyclopentadienes (C5Me4H)-
SiMe2R (R = Me, Ph) [5] were prepared according to liter-
ature procedures; benzyl magnesium chloride was obtained
commercially as a THF solution.
3.1. [Sc(g5-C5 Me4SiMe3)Cl2(THF)2] (1)
Anhydrous scandium trichloride (2.396 g, 16.0 mmol)
was suspended in THF (50 mL) and a THF suspension
of Li(C5Me4SiMe3) (3.171 g, 16.0 mmol) in 40 mL was
slowly added at ꢀ78 ꢁC. The reaction mixture was allowed
to warm to room temperature over a period of two days.
The solvent was removed in vacuo, the residue extracted
with pentane (3 · 30 mL), and the extracts slowly cooled
to ꢀ20 ꢁC. Colorless needles of [Sc(g5-C5Me4Si-
Me3)Cl2(THF)2] (1) were isolated (6.774 g, 14.9 mmol,
1
93.1%). H NMR (200 MHz, [D6]benzene) d: 0.58 (s, 9H,
3. Experimental
SiMe3), 1.43 (t, 12H, b-THF), 2.23, 2.51 (s, 2 · 6H,
C5Me4), 3.54 (t, 12H, a-THF); 13C{1H} NMR d: 2.3
(SiMe3), 12.4, 15.8 (C5Me4), 25.6 (b-THF), 68.5 (a-THF),
128.3 (ipso-C5Me4), 129.0, 132.7 (C5Me4). Anal. Calc. for
C20H37Cl2O2ScSi (453.46): C, 52.98; H, 8.22; Sc, 9.91.
Found: C, 49.81; H, 7.62; Sc, 9.93%. The analysis indicate
partial loss of THF upon standing to form [Sc(g5-
C5Me4SiMe3)Cl2(THF)].
All operations were carried out under argon using stan-
dard Schlenk-line and glovebox techniques. Pentane was
distilled from sodium/triglyme benzophenone ketyl, THF,
and toluene from sodium benzophenone ketyl under argon.
NMR spectra were recorded on Varian Unity-500 (1H,
499.6 MHz; 13C, 125.6 MHz), Bruker Avance II 400 MHz
(1H, 400.1 MHz; 13C, 100.6 MHz), or Varian Mercury-
200 (1H, 200.1 MHz) spectrometers in [D6]benzene,
[D8]THF, [D8]toluene at 20 ꢁC, unless stated otherwise;
the chemical shifts were referenced to the residual solvent
resonances. Combustion analysis of crystalline samples
repeatedly gave poor results with inconsistent values from
run to run. This difficulty is attributed to the extreme sen-
sitivity of the material and has been described previously
[3f,12]. Metal analysis was performed by complexometric
3.2. [Sc(g5-C5Me4SiMe3)(CH2Ph)2(THF)] (2)
[Sc(g5-C5Me4SiMe3)Cl2(THF)2] (1.229 g, 2.71 mmol)
was dissolved in THF (20 mL) and cooled to ꢀ78 ꢁC. Ben-
zylmagnesium chloride (4.10 mL, 5.50 mmol; 20 wt% in
THF) was slowly added via syringe, the reaction mixture
was allowed to warm to room temperature, and stirred
overnight. The volatiles were removed in vacuo and the

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J. Hitzbleck et al. / Journal of Organometallic Chemistry 692 (2007) 4702–4707
residue extracted with pentane (3 · 20 mL), the extracts
concentrated and cooled to ꢀ40 ꢁC. Pale yellow crystals
of 2 deposited (0.315 g, 0.64 mmol, 23.6%). 1H NMR
(500 MHz, [D8]toluene) d: 0.39 (s, 9H, SiMe3), 0.96 (s,
4H, b-THF), 1.82, 2.18 (s, 2 · 6H, C5Me4), overlapping
with 1.80, 2.14 (m, 2 · 2H, CH2Ph), 3.12 (s, 4H, a-THF),
(0.012 g, 0.05 mmol) in [D8]THF (0.2 mL) and stored at
room temperature for 2 h. 1H NMR (200 MHz,
[D8]THF) d: 0.90 (s, 9H, SiMe3), 1.95, 2.10 (s, 12H,
C5Me4), 2.30 (s, 2H, CH2Ph), 2.47 (q, JBH = 5.3 Hz, 2H,
CH2B), 6.51–7.20 (m, 25H, Ph).
2
2
2
6.70 (t, JHH = 7.2 Hz, 2H, p-Ph), 6.82 (d, JHH = 7.6 Hz,
3.5. Styrene polymerization
2
4H, o-Ph), 7.04 (t, JHH = 7.6 Hz, 4H, m-Ph); 13C{1H}
NMR d: 2.4 (SiMe3), 11.6, 15.0 (C5Me4), 24.8 (b-THF),
58.8 (CH2Ph), 71.8 (a-THF), 118.0 (ipso-C5Me4), 118.9,
125.1, 128.5 (p-, o-, m-Ph), 128.2, 129.2 (C5Me4), 152.5
Toluene was dried over Na/benzophenone, distilled
under argon, degassed in three freeze-pump-thaw cycles
and stored over a sodium mirror. Styrene was dried over
CaH2 and stored in the glovebox at ꢀ40 ꢁC. Stock solu-
tions (5 mM) of the Sc catalyst precursor 2, the activator
([Ph3C][B(C6F5)4]) [A], and (AliBu3; 50 mM stock solution)
[Al] were prepared in toluene prior to use. In a typical poly-
merization experiment toluene (7 mL), AliBu3 (1 mL [Al]),
catalyst (1 mL [Sc]) and the activator (1 mL [A]) were suc-
cessively combined and stirred for 1 min during which the
solution changed its color from orange to light yellow or
colorless. Styrene (ꢂ1 mL, weight recorded) was added
and stirred rapidly for different periods of time (1–3 h,
recorded). The polymerization was terminated by addition
of acidified methanol (1 mL), the polymer washed with eth-
anol and dried under vacuum (ꢂ1 · 10ꢀ3 mm Hg) at 60 ꢁC
Samples were characterized by 1H and 13C NMR spectros-
copy as well as DSC analysis, showing formation of highly
syndiotactic polystyrene. 13C NMR (300 MHz, [D2]tetra-
chloroethane) d 40.6 (CH2CHPh), 43.7 (CH2CHPh),
125.7 (p-Ph), 127.7 (m-Ph), 128.0 (o-Ph), 145.4 (ipso-Ph).
DSC melting endotherms of various samples were recorded
between 267 and 273 ꢁC.
1
(ipso-C of Ph); H NMR ([D8]toluene, ꢀ40 ꢁC) d: 0.42 (s,
9H, SiMe3), 0.77 (s, 4H, b-THF), 1.73, 2.17 (s, 2 · 6H,
1
C5Me4), 1.87, 2.15 (d, JHH = 9.6 Hz, 2 · 2H, CH2Ph),
2
3.12 (s, 4H, a-THF), 6.70 (t, JHH = 7.2 Hz, 2H, p-Ph),
2
2
6.82 (d, JHH = 7.3 Hz, 4H, o-Ph), 7.04 (t, JHH = 7.0 Hz,
4H, m-Ph). Anal. Calc. for C30H43OScSi (492.69): Sc,
9.12. Found: Sc, 9.02%.
3.3. [Sc(g5-C5 Me4SiMe2Ph)(CH2Ph)2(1,4-dioxane)] (3)
n-Butyllithium (1.40 mL, 3.50 mmol; 2.5 M in hexanes)
was added to a THF solution (30 mL) of (C5Me4H)SiMe2Ph
(0.846 g, 3 30 mmol) at ꢀ78 ꢁC and subsequently warmed
up to room temperature over a period of 1 h. The mixture
was slowly added to a dispersion of scandium trichloride
(0.500 g, 3.30 mmol) in THF (20 mL) at ꢀ78 ꢁC and stirred
at room temperature overnight. The solvent was removed in
vacuo, the residue extracted with pentane (3 · 20 mL) and
toluene (20 mL) to give a yellow oil upon reduction of the
solvent volume. THF (20 mL) was added, the solution
cooled to ꢀ78 ꢁC and a solution of benzylmagnesium chlo-
ride (4.96 mL, 6.65 mmol; 20 wt% in THF) added dropwise.
The solution was warmed up to room temperature for 3 h
and the solution concentrated in vacuo. The oily residue
was triturated with 1,4-dioxane (10 mL) to precipitate
MgCl2(1,4-dioxane)2. Extraction with toluene (30 mL),
removal of the solvent and recrystallization from toluene
at ꢀ40 ꢁC gave yellow crystals of 3 (0.194 g, 0.34 mmol,
overnight. Activities for 2: 5.0 kg(sPS) mol(Sc)ꢀ1 hꢀ1
.
3.6. X-ray crystallographic analysis
Crystal data were collected on a Bruker CCD area-
detector diffractometer (graphite monochromated Mo Ka
radiation,) by use of u and x scans. The SMART program
package was used for the data collection and unit cell deter-
mination; processing of the raw frame data was performed
using SAINT; absorption corrections were applied with SAD-
ABS [14]. The structures were solved by direct methods and
refined against F2 using all reflections with the SHELXL-97
software package [15]. The non-hydrogen atoms were
refined anisotropically, hydrogen atoms were placed in cal-
culated positions.
1
10.2%). H NMR (500 MHz, [D6]benzene) d: 0.41 (s, 6H,
SiMe2), 1.83, 2.18 (s, 2 · 6H, C5Me4), 1.91, 2.23 (d,
2JHH = 8.9 Hz, 2 · 2H, CH2Ph), 3.10, 3.55 (br s, 2 · 4H,
2
dioxane), 6.77 (t, JHH = 7.3 Hz, 3H, p-Ph, p-CH2Ph),
6.91 (d, 2JHH = 8.2 Hz, 4H, o-CH2Ph), 7.00 (d,
2
2JHH = 8.2 Hz, 4H, o-Ph), 7.04 (t, JHH = 7.3 Hz, 2H, m-
2
Ph), 7.11 (t, JHH = 7.6 Hz, 4H, m-Ph); 13C{1H} NMR d:
2.4 (SiMe2), 11.7, 15.0 (C5Me4), 58.9 (CH2Ph), 67.9, 71.8
(dioxane), 118.9 (ipso-C5Me4), 125.1, 128.3, 129.3
(p-, o-, m-CH2Ph), 125.6, 128.3, 128.5 (p-, o-, m-Ph), 127.9,
128.1 (C5Me4), 152.5 (ipso-C of Ph). Anal. Calc. for
C35H45O2ScSi (570.76): Sc, 7.88. Found: Sc, 7.76%.
4. Supplementary material
CCDC 636934 and 636933 contain the supplementary
crystallographic data for 2 and 3. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223 336 033; or e-mail: deposit@
ccdc.cam.ac.uk.
3.4. [Sc(g5-C5 Me4SiMe3)(CH2Ph)(THF)x]
[BPh3(CH2Ph)] (4)
A solution of 2 (0.024 g, 0.05 mmol) in [D8]THF
(0.3 mL) was added to a solution of triphenylborane

J. Hitzbleck et al. / Journal of Organometallic Chemistry 692 (2007) 4702–4707
4707
(h) P.G. Hayes, W.E. Piers, M. Parvez, J. Am. Chem. Soc. 125 (2003)
5622–5623;
Acknowledgements
(i) A.G. Avent, F.G.N. Cloke, B.R. Elvidge, P.B. Hitchcock, Dalton
Trans. (2004) 1083–1096;
(j) S. Bambirra, A. Meetsma, B. Hessen, Organometallics 19 (2006)
3454–3462.
Financial support of this work by the European Com-
mission in the FP6 Project NMP3-CT-2005-516972, the
Fonds der Chemischen Industrie and the Deutsche For-
schungsgemeinschaft is gratefully acknowledged.
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