Yttrium alkyl complex with a linked bis(amidinate) ancillary ligand

Article abstract of DOI:10.1021/om0008124

The dilithium salt of a linked bis(amidinate) dianionic ligand, Li₂[Me₃SiNC(Ph)N(CH₂)₃-NC(Ph)NSiMe₃] (1), was prepared by reaction of dilithiated N,N′-bis(trimethylsilyl)-1,3-diaminopropane with benzonitrile. Reaction of 1 with YCl₃(THF)_3.5 gave [Me₃SiNC(Ph)N-(CH₂)₃NC(Ph)NSiMe₃]YCl(THF)₂ (2), which, by reaction with Li[CH(SiMe₃)₂], was converted to the alkyl complex [Me₃SiNC(Ph)N(CH₂)₃NC(Ph) NSiMe₃]Y[CH(SiMe₃)₂](THF) (3). A structure determination of 3 showed that linking together the amidinate functionalities opens up the coordination sphere to allow the bonding of an additional molecule of THF not present in the unbridged bis(amidinate) analogue [PhC(NSiMe₃)₂]₂ Y[CH(SiMe₃)₂].

Full text of DOI:10.1021/om0008124

782
Organometallics 2001, 20, 782-785
Yttr iu m Alk yl Com p lex w ith a Lin k ed Bis(a m id in a te)
An cilla r y Liga n d †
Sergio Bambirra, Auke Meetsma, Bart Hessen,* and J an H. Teuben
Center for Catalytic Olefin Polymerization, Stratingh Institute for Chemistry and Chemical
Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
Received September 20, 2000
The dilithium salt of a linked bis(amidinate) dianionic ligand, Li2[Me3SiNC(Ph)N(CH2)3-
NC(Ph)NSiMe3] (1), was prepared by reaction of dilithiated N,N′-bis(trimethylsilyl)-1,3-
diaminopropane with benzonitrile. Reaction of 1 with YCl3(THF)3.5 gave [Me3SiNC(Ph)N-
(CH2)3NC(Ph)NSiMe3]YCl(THF)2 (2), which, by reaction with Li[CH(SiMe3)2], was converted
to the alkyl complex [Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3]Y[CH(SiMe3)2](THF) (3). A struc-
ture determination of 3 showed that linking together the amidinate functionalities opens
up the coordination sphere to allow the bonding of an additional molecule of THF not present
in the unbridged bis(amidinate) analogue [PhC(NSiMe3)2]2Y[CH(SiMe3)2].
Sch em e 1
In tr od u ction
Linking two anionic ancillary ligands together by a
covalent bridge as a means of determining complex
geometry and limiting ligand mobility has been a very
useful concept in transition-metal chemistry. The prime
example for this is provided by the ansa-bis(indenyl)
complexes first designed by Brintzinger et al.1 and
highly successful in the stereoregular catalytic polym-
erization of propene.2 This approach has since been
applied to various other anionic functionalities such as
amides and aryloxides.3 The N,N′-bis(trimethylsilyl)
benzamidinate monoanionic ligand has been extensively
used in the past as an ancillary in main group and
transition-metal chemistry.4 We recently developed a
method to prepare N-functionalized N′-SiMe3-benz-
amidinates by reaction of various lithium mono(trim-
ethylsilyl)amides with benzonitrile.5 This approach also
is useful for the preparation of covalently linked bis-
(amidinate) ancillary ligands. Here we describe the
synthesis of a yttrium alkyl complex with a linked bis-
(amidinate) ligand and show that the linking of the two
amidinate moieties results in a different ligand geom-
etry and a different coordination behavior of the metal
center compared to analogous complexes with two
unlinked amidinate ligands.
Resu lts a n d Discu ssion
The synthesis of the N,N′-bis(trimethylsilyl)amidinate
ligand by reaction of the amide Li[N(SiMe3)2] with
benzonitrile (proceeding via attack of the amide on the
nitrile carbon followed by a trimethylsilyl shift) was first
reported by Sanger.6 This method can be extended to a
range of mono(trimethylsilyl) amides Li[N(SiMe3)R] to
yield the lithium salts of functionalized benzamidinates
Li[PhC(NSiMe3)(NR)].5,7 This approach can also be used
to prepare linked bis(amidinate) salts. Deprotonation
of the N,N′-bis(trimethylsilyl)-1,3-diaminopropane Me3-
Si(H)N(CH2)3N(H)SiMe3 with 2 equiv of n-BuLi, fol-
lowed by reaction with 2 equiv of benzonitrile in a THF/
pentane mixture, yields the linked bis(benzamidinate)
salt Li2[Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3] (1, Scheme
1). The compound was isolated analytically pure in 69%
yield as a white solid containing 0.5 equiv of THF per
formula unit.
Reaction of the dilithium salt 1 with YCl3(THF)3.5 in
THF, followed by extraction with pentane, afforded the
corresponding yttrium bis(amidinate) monochloride com-
plex with two coordinated molecules of THF, [Me3SiNC-
(Ph)N(CH2)3NC(Ph)NSiMe3]YCl(THF)2 (2, Scheme 2), as
analytically pure material in 57% isolated yield. By
reaction with Li[CH(SiMe3)2] the chloride and one of the
† Netherlands Institute for Catalysis Research (NIOK) Publication
No. RUG-00-4-5.
(1) (a) Wild, F. R. W. P.; Zsolnai, G.; Huttner, G.; Brintzinger, H.
H. J . Organomet. Chem. 1982, 232, 233. (b) Wild, F. R. W. P.;
Wasiucionek, M.; Huttner, G.; Brintzinger, H. H. J . Organomet. Chem.
1985, 288, 63.
(2) (a) Ewen, J . A. J . Am. Chem. Soc. 1984, 106, 6355. (b) Kaminski,
W.; Ku¨lper, K.; Brintzinger, H. H.; Wild, F. R. W. P. Angew. Chem.,
Int. Ed. Engl. 1985, 24, 507. (c) Brintzinger, H. H.; Fischer, D.;
Mu¨lhaupt, R.; Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed.
Engl. 1995, 34, 1143, and references therein.
(3) For recent examples, see: (a) Gountchev, T. I.; Tilley, T. D.
Organometallics 1999, 18, 2896. (b) Lee, C. H.; La, Y.-H.; Park, J . W.
Organometallics 2000, 19, 344. (c) Baumann, R.; Stumpf, R.; Davis,
W. M.; Liang, L.-C.; Schrock, R. R. J . Am. Chem. Soc. 1999, 121, 7822.
(d) Ko, B.-T.; Wu, C.-C.; Lin, C.-C. Organometallics 2000, 19, 1864. (e)
Gielens, E. E. C. G.; Dijkstra, T. W.; Berno, P.; Meetsma, A.; Hessen,
B.; Teuben, J . H. J . Organomet. Chem. 1999, 591, 88.
(4) For reviews on this chemistry, see: (a) Edelmann, F. Coord.
Chem. Rev. 1994, 137, 403. (b) Barker, J .; Kilner, M. Coord. Chem.
Rev. 1994, 133, 219.
(6) (a) Sanger, A. R. Inorg. Nucl. Chem. Lett. 1973, 9, 351. (b) Boere´,
R. T.; Oakley, R. T.; Reed, R. W. J . Organomet. Chem. 1987, 331, 161.
(7) Bambirra, S.; Brandsma, M. J . R.; Brussee, E. A. C.; Meetsma,
A.; Hessen, B.; Teuben, J . H. Organometallics 2000, 19, 3197.
(5) Brandsma, M. J . R.; Brussee, E. A. C.; Meetsma, A.; Hessen, B.;
Teuben, J . H. Eur. J . Inorg. Chem. 1998, 1867.
10.1021/om0008124 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 01/26/2001

Yttrium Alkyl Complex
Organometallics, Vol. 20, No. 4, 2001 783
Sch em e 2
Ta ble 1. Selected In ter a tom ic Dista n ces (Å) a n d
An gles (d eg) for 3 (for on e of th e tw o in d ep en d en t
m olecu les in th e u n it cell)
Y(1)-N(1)
Y(1)-N(2)
Y(1)-C(24)
2.488(6)
2.308(8)
2.410(8)
Y(1)-N(3)
Y(1)-N(4)
Y(1)-O(1)
2.298(7)
2.469(7)
2.395(7)
N(1)-Y(1)-N(2)
N(3)-Y(1)-N(4)
N(2)-Y(1)-N(3)
N(1)-Y(1)-N(4)
Y(1)-C(24)-Si(3)
Y(1)-C(24)-Si(3)
56.7(2)
56.5(2)
74.9(2)
163.0(2)
121.3(4)
106.1(4)
N(1)-Y(1)-C(24)
N(2)-Y(1)-C(24)
N(3)-Y(1)-C(24)
N(4)-Y(1)-C(24)
O(1)-Y(1)-C(24)
Si(3)-C(24)-Si(4)
89.6(2)
110.8(3)
101.3(3)
104.4(2)
145.1(3)
118.5(4)
amidinate moieties are each dihapto bound through the
nitrogen atoms, with the Y-N-C-N units only deviat-
ing slightly from planarity (dihedral angles Y(1)-N(1)-
C(4)-N(2) ) -15.6(7)°, Y(1)-N(4)-C(14)-N(3) ) -7.0-
(7)°). By comparing the bis(amidinate)Y geometry in 3
with that of the structurally characterized p-methoxy-
benzamidinate derivative of the unbridged bis(ami-
dinate) complex 4, [(p-MeOC6H4)C(NSiMe3)2]2Y[CH-
(SiMe3)2] (5),8a it can be seen that the amidinates
respond to the tethering in two ways. In 3 there is now
a substantial difference in Y-N distance for the amidi-
nate nitrogens attached to the bridge compared to those
attached to the SiMe3 group (the former being 0.18 Å
shorter). In 5, all Y-N bond distances are around 2.33
( 0.01 Å. In addition, the tethering of the amidinate
functionalities in 3 restricts the angle between the two
Y-N-C-N planes, which is now only 24.7(4)°, com-
pared to 75.6(2)° in 5. This opens up the coordination
sphere of Y and allows for the coordination of an
additional molecule of THF in 3. One notable feature is
the large C(24)-Y(1)-O(1) angle of 145.1(3)°. The gap
left open in this way is occupied by a Si-Me group of
the bis(trimethylsilylmethyl) ligand, which is distorted,
Y(1)-C(24)-Si(4) ) 106.1(4)° compared to Y(1)-C(24)-
Si(3) ) 121.3(4)°, to result in relatively short distances
Y(1)‚‚‚Si(4) ) 3.415(3) Å and Y(1)‚‚‚C(28) ) 3.299(12)
Å. This distortion of the alkyl group in 3 is less
pronounced than similar types of distortions observed
in mono- and bis-η5-C5Me5 yttrium and lanthanide bis-
(trimethylsilyl)methyl complexes,9 but such a distortion
is completely absent in 5.
F igu r e 1. Molecu la r str u ctu r e of [Me3SiNC(P h )N-
(CH2)3NC(P h )NSiMe3]Y[CH(SiMe3)2](THF ) (3). Th er -
m a l ellip soid s a r e d r a w n a t th e 30% level.
THF molecules in 2 can be replaced by the sterically
demanding bis(trimethylsilyl)methyl group to give the
alkyl complex [Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3]Y-
[CH(SiMe3)2](THF) (3, Scheme 2). The presence of a
coordinated molecule of THF in 3 is a marked contrast
with the nonbridged bis(amidinate) yttrium alkyl [PhC-
(NSiMe3)2]2Y[CH(SiMe3)2] (4) reported previously by our
group,8 which is free from coordinated base or salt. The
low-temperature 1H NMR spectrum of 3 (-60 °C,
toluene-d8 solvent) shows two multiplets (2H each) for
the diastereotopic NCH2 methylene protons and two
multiplets (1H each, one overlapped by THF) for the
diastereotopic central CH2 group of the ligand backbone,
as well as one singlet each for the alkyl and amidinate
SiMe3 groups and two well-separated doublets for the
phenyl o-protons. These data indicate an averaged Cs
symmetry of the complex and slow rotation around the
1
ligand C-Ph bond at this temperature. The H and 13C
NMR resonances of the Y-CH group in 3, δ -0.34 ppm
1
(2J YH ) 1.8 Hz) and δ 35.8 ppm (1J YC ) 32 Hz, J CH
)
93 Hz), are downfield by 0.6 ppm and upfield by 7.7
ppm, respectively, relative to the resonances in un-
bridged, base-free 4.
The two 1,2-cyclohexanediyl-linked bis(amidinate)
titanium compounds (including an unusual bis(amidi-
nate) titanium arene complex) reported by Hagadorn
and Arnold10 and the compounds 2 and 3 described here
are thus far the only complexes known with a chelating
tethered bis(amidinate) ancillary ligand system. One
bimetallic complex with a bridging linked bis(amidinate)
A crystal structure determination of 3 (Figure 1,
pertinent interatomic distances and angles in Table 1)
confirms the monomeric nature of the complex and the
chelating bonding mode of the linked bis(amidinate)
ligand. The unit cell contains two independent molecules
that do not differ significantly in geometry; only one of
the two molecules is shown, and its geometrical param-
eters are used for the discussion of the structure. The
(9) (a) Klooster, W. T.; Brammer, L.; Schaverien, C. J .; Budzelaar,
P. H. M. J . Am. Chem. Soc. 1999, 121, 1381, and references therein.
(b) For comparison with (C5Me5)2Y[CH(SiMe3)2] see: Den Haan, K.
H.; De Boer, J . L.; Teuben, J . H.; Spek, A. L.; Kojic-Prodic, B.; Hays,
G. R.; Huis, R. Organometallics 1986, 5, 1726.
(10) Hagadorn, J . R.; Arnold, J . Angew. Chem., Int. Ed. 1998, 37,
1729.
(8) (a) Duchateau, R.; Van Wee, C. T.; Meetsma, A.; Van Duijnen,
P. Th.; Teuben, J . H. Organometallics 1996, 15, 2279. (b) Duchateau,
R.; Van Wee, C. T.; Meetsma, A.; Teuben, J . H. J . Am. Chem. Soc.
1993, 115, 4931.

784 Organometallics, Vol. 20, No. 4, 2001
Bambirra et al.
p-Ph), 68.2 (t, J ) 148 Hz, R-CH2 THF), 51.0 (t, J ) 134 Hz,
NCH2), 32.62 (t, J ) 123 Hz, CH2), 25.3 (t, J ) 132 Hz, â-CH2
THF), 3.3 (q, J ) 118 Hz, SiMe3). Anal. Calcd for C27H42N4-
LiO0.5Si2: C, 63.53; H, 8.10; N, 11.85; Li, 2.94. Found: C, 63.45;
H, 8.11; N, 11.68; Li, 2.99.
ligand, derived from the reaction of an R,ω-bis(carbo-
diimide) with CpTiMe3, has also been described.11 These
few examples already show that substantial differences
in geometry and reactivity can be achieved by covalently
linking amidinate functionalities. It is expected that the
linked bis(amidinate) ligand system, together with the
linked aminopyridinato12 and aminotroponiminate13
ligands, will form an interesting set of ancillary ligands
for new transition-metal and lanthanide chemistry.
Syn th esis of [Me3SiNC(P h )N(CH2)3NC(P h )NSiMe3]YCl-
(THF )2 (2). To a stirred suspension of YCl3(THF)3.5 (0.94 g,
2.1 mmol) in 30 mL of THF was added 0.99 g (2.1 mmol) of
solid 1 in portions. The resulting yellowish solution was stirred
overnight. Subsequently, the solvent was removed in vacuo
and the remaining solid stripped of residual THF by stirring
with 20 mL of pentane, which was then pumped off. The solid
was extracted with pentane (5 × 40 mL), and the volume of
the extract was reduced to 20 mL. Cooling to -30 °C yielded
Con clu sion
The reaction of lithium trimethylsilylamides with
benzonitrile to give lithium (mono)trimethylsilyl ben-
zamidinates can also be used to obtain tethered bis-
(amidinate) ligands, as shown by the synthesis of the
1,3-propanediyl-bridged species 1. The two yttrium
complexes synthesized with this ligand, the chloride 2
and the alkyl 3, represent only the second example of
complexes with a chelating bis(amidinate) ancillary
ligand. The linking of the two amidinate functionalities
alters the relative orientation of the amidinates in the
complex and opens up the metal coordination sphere
relative to the analogous unbridged systems.
1
colorless crystals of 2 (0.82 g, 1.19 mmol, 57%). H NMR (300
3
MHz, C6D6, 25 °C): δ 7.42 (br, 4H, o-Ph), 7.17 (t, 4H, J HH
)
3
7.5 Hz, m-Ph), 7.07 (t, 2H, J HH ) 6.9 Hz, p-Ph), 3.94 (br m, 8
H, R-CH2 THF), 3.13 (m, 2 H, NCHH), 2.94 (m, 2 H, NCHH),
1.57 (m, 1H, CHH), 1.43 (br m, 8H, â-CH2 THF), 1.39 (m, 1H,
CHH), 0.30 (s, 18H, SiMe3). 13C NMR (75.4 MHz, C6D6, 25
°C): δ 178.9 (s, NCN), 138.7(s, Ph C), 128.3 (d, J ) 154 Hz,
o-Ph), 127.2 (d, J ) 158 Hz, m-Ph), 126.4 (d, J ) 154 Hz, p-Ph),
69.9 (t, J ) 148 Hz, R-CH2 THF), 48.4 (t, J ) 133 Hz, NCH2),
32.6 (br, CH2), 25.5 (t, J ) 132 Hz, â-CH2 THF), 3.6 (q, J )
118.3 Hz, SiMe3). Anal. Calcd for C31H50N4YClO2Si2: C, 53.86;
H, 7.29; N, 8.10; Y, 12.86. Found: C, 54.23; H, 7.40; N, 8.25;
Y, 12.93.
Syn t h esis of [Me3SiNC(P h )N(CH2)3NC(P h )NSiMe3]Y-
[CH(SiMe3)2] (THF ) (3). To a stirred solution of 2 (0.48 g,
0.7 mmol) in 10 mL of THF was added 0.17 g (0.7 mmol) of
Li[CH(SiMe3)2]. The resulting colorless solution was stirred
for 3 h, after which the solvent was removed in vacuo. The
remaining solid was stripped of residual THF by stirring with
5 mL of pentane, which was then pumped off. The residue was
extracted with pentane (2 × 40 mL) and the volume of the
extract reduced to 10 mL. Cooling to -20 °C overnight yielded
0.33 g (0.44 mmol, 64%) of colorless crystalline 3. 1H NMR
(500 MHz, C7D8, -60 °C): δ 7.48 (d, 2H, 3J HH ) 7.3 Hz, o-Ph),
Exp er im en ta l Section
Gen er a l In for m a tion . All experiments were performed
under nitrogen atmosphere using standard glovebox and
Schlenk techniques. Deuterated solvents, C6D6, C7D8, and
THF-d8 (Aldrich), were dried over Na/K alloy and vacuum
transferred before use. Pentane and THF were distilled from
14
Na or Na/K alloy before use. The compounds YCl3(THF)3.5
,
16
Li[CH(SiMe3)2],15 and (CH2)3(NHSiMe3)3 were prepared ac-
cording to literature procedures. Benzonitrile (Aldrich) was
degassed and dried over molecular sieves (4 Å) before use. The
amines H2N(CH2)3NH2 and HN(SiMe3)2 (Aldrich) were used
as purchased. NMR spectra were run on Varian VXR-300 or
Unity 500 spectrometers. Elemental analyses were performed
by the Microanalytical Department of the University of
Groningen. Every value is the average of at least two inde-
pendent determinations.
3
7.11-6.99 (m, 6 H, m- and p-Ph), 6.91 (d, 2H, J HH ) 7.3 Hz,
o-Ph), 3.77 (m, 4 H, R-CH2 THF), 3.06 and 2.96 (m, 2H each,
NCH2), 1.39 (m, 1H, CHH), 1.25 (m, 5H, CHH and â-CH2
THF), 0.68 (s, 18H, CSiMe3), 0.14 (s, 18H, NSiMe3), -0.34 (d,
2J YH ) 1.8, Hz, 1H, YCH). 13C NMR (75.4 MHz, C6D6, 25 °C):
δ 179.5 (s, NCN), 138.6 (s, Ph C), 128.3 (d, J ) 157 Hz, o-Ph),
128.1 (d, J ) 160 Hz, m-Ph), 126.8 (d, J ) 160 Hz, p-Ph), 68.9
(t, J ) 145 Hz, R-CH2 THF), 47.8 (t, J ) 134 Hz, NCH2), 35.8
Syn th esis of Li2[Me3SiNC(P h )N(CH2)3NC(P h )NSiMe3]‚
(THF )0.5 (1). To a solution of Me3Si(H)N(CH2)3N(H)SiMe3 (7.5
g, 34.3 mmol) in 30 mL of pentane was slowly added a solution
of n-BuLi in hexane (26.0 mL, 2.5 M, 70.0 mmol). The reaction
mixture was stirred overnight; then 30 mL of THF was added
to the yellow suspension. Benzonitrile (7.0 mL, 69.0 mmol) was
then added dropwise to the solution. The reaction mixture was
stirred for 5 h, after which the solvent was removed in vacuo.
The remaining crystalline solid was rinsed with 20 mL of
pentane and dried to give 11.2 g (23.7 mmol, 69%) of the title
compound. H NMR (300 MHz, C6D6, 25 °C): δ 7.40 (d, J HH
) 6.9 Hz, 4H, o-Ph), 7.27 (t, 3J HH ) 7.3 Hz, 4H, m-Ph), 7.09 (t,
3J HH ) 7.3 Hz, 2H, p-Ph), 3.59 (m, Hz, R-CH2 THF), 3.23 (t,
3J HH ) 4.67 Hz, 4H, NCH2), 1.66 (br p, 2H, CH2), 1.38 (m,
â-CH2 THF), 0.10 (s, 18H, NSiMe3). 13C NMR (75.4 MHz, C6D6,
25 °C): δ 179.4 (s, NCN), 142.3 (s, Ph C), 128.4 (d, J ) 160
Hz, o-Ph), 127.2 (d, J ) 159 Hz, m-Ph), 126.7 (d, J ) 160 Hz,
1
1
(dd, J YC ) 32 Hz, J CH ) 93 Hz, YCH), 33.3 (t, J ) 125 Hz,
CH2), 25.5 (t, J ) 131 Hz, â-CH2 THF), 5.6 (q, J ) 117 Hz,
CSiMe3), 3.8 (q, J ) 118 Hz, NSiMe3). Anal. Calcd for C34H61N4-
YOSi4: C, 54.95; H, 8.27; N, 7.54; Y, 11.96. Found: C, 54.03;
H, 8.08; N, 7.75; Y, 11.76. The carbon content determined for
3 is consistently and reproducibly too low, whereas reasonable
values are obtained for the other elements. We have observed
this behavior previously in other Y[CH(SiMe3)2] compounds.7
It may be associated with the formation of inert carbide
species.
1
3
Cr ysta l Str u ctu r e Deter m in a tion . A summary of crys-
tallographic data is given in Table 2. A suitable crystal of 3
was obtained by cooling a pentane solution to -20 °C, mounted
using inert handling techniques into the cold nitrogen stream
of an Enraf-Nonius CAD-4F diffractometer. The unit cell
parameters were obtained from a least-squares treatment of
22 reflections in the range 16.77° < θ < 21.56°. The |E|
distribution statistics indicated a non-centrosymmetric space
group. Space group P21 was determined from considerations
of the unit cell parameters, statistical analyses of intensity
distributions, and (where appropriate) systematic absences.
Examination of the final atomic coordinates with respect to
molecular symmetry and coordinate equivalence suggested a
centrosymmetric space group (P21/c), but the systematic
extinction condition h0l: l ) 2n+1 was heavily violated.
(11) Babcock, J . R.; Incarvito, C.; Rheingold, A. L.; Fettinger, J . C.;
Sita, L. R. Organometallics 1999, 18, 5729.
(12) Noss, H.; Oberthu¨r, M.; Fischer, C.; Kretschmer, W. P.; Kempe,
R. Eur. J . Inorg. Chem. 1999, 2283.
(13) (a) Roesky, P. W. Inorg. Chem. 1998, 37, 4507. (b) Roesky, P.
W.; Bu¨rgstein, M. R. Inorg. Chem. 1999, 38, 5629.
(14) Freeman, J . H.; Smith, M. L. J . Inorg. Nucl. Chem. 1958, 7,
224.
(15) Wiberg, N.; Wagner, G. Chem. Ber. 1986, 119, 1455.
(16) Birkofer, L.; Ku¨hlthau, H. P.; Ritter, A. Chem. Ber. 1960, 93,
2810.

Yttrium Alkyl Complex
Organometallics, Vol. 20, No. 4, 2001 785
Ta ble 2. Cr ysta llogr a p h ic Da ta a n d Deta ils of
Str u ctu r e Refin em en t P r oced u r e for 3
the model extended by direct methods applied to difference
structure factors (DIRDIF).18 Hydrogen atoms were included
in the final refinement, introduced in calculated positions and
riding on their carrier atoms. Flack’s x refinement19 gave an
ambiguous result, probably due to enantiomorphic twinning.
Enantiomorph twin refinement resulted in a value of 0.72(2).
All calculations were performed using the SHELXL20 and
PLATON21 programs.
formula
fw
C34H61N4OSi4Y
743.12
cryst dimens, mm
space group
temp, K
0.20 × 0.25 × 0.50
P21, No. 4
130
a, Å
b, Å
c, Å
18.763(1)
10.205(1)
22.391(2)
106.383(7)
1.198
â, deg
Ack n ow led gm en t. This work was generously sup-
ported by ExxonMobil Chemical Company.
Dc, g cm-3
formula Z
4
radiation (λ, Å)
no. of total rflns
no. of unique rflns
no. of obsd rflns (Fo > 4.0σ(Fo))
no. of params
µ, cm-1
0.710 73
9745
9453
7119
818
15.6
0.1128
0.0322, 8.0825
0.72(2)
0.0487
Su p p or tin g In for m a tion Ava ila ble: Full details of the
crystal structure determination of 3 including positional and
thermal parameters. This material is available free of charge
via the Internet at http://pubs.acs.org.
2
a
wR(Fo
)
OM0008124
weighting scheme:ba, b
Flack’s x, twin ratio
R(F)c
(17) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.
(18) Beurskens, P. T.; Beurskens, G.; Bosman, W. P.; De Gelder,
R.; Garc´ıa-Granda, S.; Gould, R. O.; Israe¨l, R.; Smits, J . M. M. The
DIRDIF-97 program system; Crystallography Laboratory, University
of Nijmegen: Nijmegen, The Netherlands, 1997.
min, max resid density, e/Å3
-0.54, 0.60(9)
wR(F2) ) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]]1/2 for Fo > 0. w )
a
2
2
b
1/[σ2(Fo2) + (aP)2 + bP] and P ) [max(Fo2,0) + 2Fc2]/3. c R(F) ) ∑
(||Fo| - |Fc||)/∑|Fo| for Fo > 4.0 σ (Fo).
(19) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
(20) Sheldrick, G. M. SHELX-97. Program for the Solution and
Refinement of Crystal Structures; University of Go¨ttingen: Go¨ttingen,
Germany, 1997.
(21) Spek, A. L. PLATON. Program for the Automated Analysis of
Molecular Geometry, Version March 1998; University of Utrecht:
Utrecht, The Netherlands.
Intensity data were corrected for Lorentz and polarization
effects, scale factor and absorption (DIFABS)17 and reduced
to Fo2. The structure was solved by Patterson methods and