Mononuclear tris(aminopyridinato)zirconium alkyl, aryl, and alkynyl complexes

Article abstract of DOI:10.1021/om9507282

The reaction of 3 equiv of 4-methyl-2-((trimethylsilyl)amino)pyridine (TMS-AP-H) with (Me₂N)₂-ZrCl₂(THF)₂ or the in situ lithiation of TMS-AP-H followed by addition of ZrCl₄ affords (TMS-AP)₃Zr-Cl (1) in high yield. The X-ray analysis of 1 reveals a mononuclear zirconium complex coordinated by six nitrogen atoms with an overall 3-fold molecule symmetry. The η²-coordinated aminopyridinato ligands arrange in a propeller-like fashion. The reactions of 1 with MeLi, phenyllithium, and (phenylethynyl)lithium afford the corresponding σ-alkyl, -aryl, and -alkynyl complexes ((TMS-AP)₃Zr-Me (2), (TMS-AP)₃Zr-Ph (3), and (TMS-AP)₃Zr-C≡CPh (4). X-ray diffraction studies of 4 establish its monomeric structure, a long Zr-C bond distance, and a sterically shielded alkynyl ligand.

Full text of DOI:10.1021/om9507282

Organometallics 1996, 15, 1071-1074
1071
Mon on u clea r Tr is(a m in op yr id in a to)zir con iu m Alk yl,
Ar yl, a n d Alk yn yl Com p lexes
Rhett Kempe,* Simon Brenner, and Perdita Arndt
MPG AG “Komplexkatalyse” an der Universita¨t Rostock, Buchbinderstrasse 5-6,
18055 Rostock, Germany
Received September 13, 1995X
Summary: The reaction of 3 equiv of 4-methyl-2-((tri-
methylsilyl)amino)pyridine (TMS-AP-H) with (Me2N)2-
ZrCl2(THF)2 or the in situ lithiation of TMS-AP-H
followed by addition of ZrCl4 affords (TMS-AP)3Zr-Cl
(1) in high yield. The X-ray analysis of 1 reveals a
mononuclear zirconium complex coordinated by six
nitrogen atoms with an overall 3-fold molecule sym-
metry. The η2-coordinated aminopyridinato ligands
arrange in a propeller-like fashion. The reactions of 1
with MeLi, phenyllithium, and (phenylethynyl)lithium
afford the corresponding σ-alkyl, -aryl, and -alkynyl
complexes ((TMS-AP)3Zr-Me (2), (TMS-AP)3Zr-Ph (3),
and (TMS-AP)3Zr-CtCPh (4). X-ray diffraction studies
of 4 establish its monomeric structure, a long Zr-C bond
distance, and a sterically shielded alkynyl ligand.
(TMS-AP) ligand with a “maximal steric angle” of 144° 8
to gives rise to a propeller-like C3 symmetric complex
fragment containing a reactive pocket similar to those
observed for tripod chelating ligands. Herein is reported
the synthesis and structure of the first mononuclear
zirconium complex that contains aminopyridinato
ligands:9 (TMS-AP)3Zr-Cl and its σ-alkyl, -aryl, and
-alkynyl derivatives.
Resu lts a n d Discu ssion
The reaction of 3 equiv of TMS-AP-H with mixed
chloro(dialkylamido)zirconium complexes like (Me2N)2-
ZrCl2(THF)2 (easily accessible by reacting Zr(NMe2)4
with ZrCl4 in the presence of THF10 ) affords the
colorless crystalline compound 1 (eq 1). A small amount
Me2NH2Cl is observed as a byproduct. 1H and 13C NMR
spectra are indicative of an overall C3 molecular sym-
metry, and elemental analysis is consistent with the
formula (TMS-AP)3Zr-Cl.
In tr od u ction
1-3
Amido-based tripod ligand systems
that form
stable early transition metal complexes have gained a
lot of attention. The ligands in these complexes shield
a large sector of the coordination sphere and thus
provide a “reactive pocket” for metal-supported activa-
tion and transformation reactions. Such complexes
have been shown to activate small molecules like
dinitrogen,4 to give rise to unusual transformation
reactions,5 and to provide access to stable polar metal-
metal bonds.6 With regard to their catalytic applica-
tions, we are currently examining the chemistry of early
transition metal complexes that are reactive due to
strained η2-coordinated aminopyridinato ligands.7 We
expect the 4-methyl-2-((trimethylsilyl)amino)pyridinato
X Abstract published in Advance ACS Abstracts, December 15, 1995.
(1) Gudat, D.; Verkade, J . G. Organometallics 1989, 8, 2772.
Lensink, C.; Xi, S. K.; Daniels, L. M.; Verkade, L. G. J . Am. Chem.
Soc. 1989, 111, 3478. Naiini, A. A.; Menge, W. M. P. B.; Verkade, J .
G. Inorg. Chem. 1991, 30, 5009. Duan, Z.; Verkade, J . G. Inorg. Chem.
1995, 34, 1576. Cummins, C. C.; Schrock, R. R.; Davis, W. M.
Organometallics 1992, 11, 1452. See also refs 4 and 5.
(2) J ohnson, A. R.; Wanandi, P. W.; Cummins, C. C.; Davis, W. M.
Organometallics 1994, 13, 2907. Wanandi, P. P.; Davis, W. M.;
Cummins, C. C.; Russell, M. A.; Dean, E. W. J . Am. Chem. Soc. 1995,
117, 2110. Laplaza, C. E.; Odom, A. L.; Davis, W. M.; Protasiewicz, J .
D. J . Am. Chem. Soc. 1995, 117, 4999.
(3) Schubart, M.; Findeisen, B.; Gade, L. H.; Li, W.-S.; McPartlin,
M. Chem. Ber. 1995, 128, 329. Schubart, M.; O’Dwyer, L.; Gade, L.
H.; Li, W.-S.; McPartlin, M. Inorg. Chem. 1994, 33, 3893. Memmler,
H.; Gade, L. H.; Lauher, J . W. Inorg. Chem. 1994, 33, 3064. Gade, L.
H.; Becker, C.; Lauher, J . W. Inorg. Chem. 1993, 32, 2308. Gade, L.
H.; Mahr, N. J . Chem. Soc., Dalton Trans. 1993, 489.
(4) Shih, K.-Y.; Schrock, R. R.; Kempe, R. J . Am. Chem. Soc. 1994,
116, 8804. Kol, M.; Schrock, R. R.; Kempe, R.; Davis, W. M. J . Am.
Chem. Soc. 1994, 116, 4382. Laplaza, C. E.; Cummins, C. C. Science
1995, 268, 861.
The common synthetic procedure of ligand lithiation
followed by adding of zirconium chloride leads to 1 in a
high-yield reaction (eq 2). This observation is in con-
trast to synthetic protocols of titanium aminopyridinato
complexes,7 where only very low yields could be ob-
tained.
(8) The “maximal steric angle” was defined as the angle between
the outermost H atoms of the pyridine ring, the metal at which the
aminopyridinato ligand coordinates, and the outermost H atom of the
substituent at the amido nitrogen in relation to the cone angle
approach, which is widely used to evaluate the bulkiness of ligands.
See also: Brown, T. L.; Lee, K. J . Coord. Chem. Rev. 1993, 128, 89.
(9) To the best of our knowledge, among the very few examples of
mononuclear transition metal complexes that contain aminopyridinato
ligands was no group 3 or 4 transition metal complex detected.
Chakravarty, A. R.; Cotton, F. A.; Shamshoum, E. S. Inorg. Chim. Acta
1984, 86, 5. Calhorda, M. J .; Carrondo, M. A. A. F. D. C. T.; Gomes da
Costa, R.; Dias, A. R.; Duarte, M. T. L. S.; Hursthouse, M. B. J .
Organomet. Chem. 1987, 320, 53. Edema, J . J . H.; Gambarotta, S.;
Meetsma, A; Spek, A. L.; Veldman, N. Inorg. Chem. 1991, 30, 2062.
(10) Brenner, S.; Kempe, R.; Arndt, P. Z. Anorg. Allg. Chem. 1996,
in press.
(5) Cummins, C. C.; Schrock, R. R.; Davis, W. M. Inorg. Chem. 1994,
33, 1448. Christou, V.; Arnold, J . Angew. Chem., Int. Ed. Engl. 1993,
32, 1450. Cummins, C. C.; Schrock, R. R.; Davis, W. M. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 756. Cummins, C. C.; Lee, J .; Schrock, R. R.;
Davis, W. M. Angew. Chem., Int. Ed. Engl. 1992, 31, 1501.
(6) Friedrich, S.; Memmler, H.; Gade, L. H.; Li, W.-S.; McPartlin,
M. Angew. Chem., Int. Ed. Engl. 1994, 33, 678.
(7) Kempe, R.; Arndt, P. Inorg. Chem. 1996, in press.
0276-7333/96/2315-1071$12.00/0 © 1996 American Chemical Society

1072 Organometallics, Vol. 15, No. 3, 1996
Notes
Suitable crystals for X-ray diffraction studies of 1 can
be obtained by slowly cooling a saturated ether solution
to -30 °C. The single-crystal X-ray structure analysis
of 1 establishes its monomeric structure as shown in
Figure 1 including principal bond distances and angles.
Some important crystallographic features are listed in
Table 1. 1 crystallizes in the quite uncommon cubic
lattice system and is oriented along a 3-fold crystal-
lographic axis. The Zr-Cl vector coincides with this
axis, and the aminopyridinato ligands arrange in a
propeller-like fashion around it. This kind of C3 sym-
metric mononuclear zirconium complex coordinated by
six nitrogen atoms constitutes a new structural type of
zirconium complexes.11 The Npyridine-C-Namido angle
(110.8(3)°) reflects the strained bonding situation. The
Zr-N2 distance (2.324(2) Å) is well in the range of such
Zr-Npyridine bonds (2.39(1) Å).12 The Zr-N1 bond length
(2.209(2) Å) is approximately 0.1 Å shorter than the
averaged Zr-Namido distance (2.11(1) Å)13 and indicates
a weak amido bond. The nitrogen atoms have an almost
planar geometry, as has been found in virtually all
structurally characterized transition metal amido com-
plexes.14 The interest in the tris(aminopyridinato)-
zirconium moiety is focused on the stabilization of
σ-alkyl, -aryl, and -alkynyl complexes in order to study
the stability of the zirconium carbon bonds with regard
to metal-supported C-C coupling reactions which might
lead to catalytic applications. The reactions of 1 with
MeLi, phenyllithium, and (phenylethynyl)lithium afford
the corresponding organometallic complexes, (TMS-
AP)3Zr-Me (2), (TMS-AP)3Zr-Ph (3), and (TMS-AP)3Zr-
CtCPh (4), as shown in Scheme 1. 1H and 13C NMR
spectra are in accordance with the formulations, and
elemental analyses are consistent. An X-ray crystal
structure analysis of 4 was carried out in order to
evaluate the steric protection of the aminopyridinato
ligand core with respect to the Zr-C and the CtC triple
bond. Suitable crystals for X-ray diffraction studies of
4 could be obtained by slowly cooling a saturated ether
solution to -30 °C. A perspective ORTEP drawing of
the molecular structure of 4 is shown in Figure 2
including key bond distances and angles. Crystal-
lographic details are listed in Table 1. The molecular
structure of 4 is characterized by a monomeric propeller-
like ligand core which is largely in accordance with the
F igu r e 1. Structural representation of 1. Hydrogen atoms
are omitted for clarity. The thermal ellipsoids correspond
to 40% probability. Selected bond distances and angles:
Zr-N(1) 2.209(2), Zr-N(2) 2.324(2), Zr-Cl 2.5160(14);
N(1)-Zr-N(2) 59.59(9), N(1)-Zr-Cl 86.25(6), N(2)-Zr-
Cl 131.22(6), C(6)-N(2)-C(1) 120.2(3), N(2)-C(1)-N(1)
110.8(3).
Ta ble 1. Cr ysta llogr a p h ic Deta ils of th e X-r a y
Cr ysta l Str u ctu r e An a lysis of 1 a n d 4
compd
cryst system
space group
a, Å
b, Å
c, Å
1
4
cubic
Pa3h
19.423(2)
monoclinic
P21/n (No. 14)
11.914(2)
20.364(2)
17.419(2)
100.48 (1)
4102.4(9)
4
â, deg
V, Å3
7327.4(1.3)
24
Z
cryst size, mm
fw
0.4 × 0.4 × 0.2 0.4 × 0.3 × 0.3
663.36
1.203
4.92
730.30
1.167
3.80
F
calcd, g cm-3
µ, cm-1 (Mo KR)
F(000)
2779
1536
T, K
173
293
θ range, deg
2.3 < θ < 23.2
2.3 < θ < 25.0
scan type
ω/2θ
ω/2θ
no. of reflcns
no. of unique reflcns
5058
1741
7659
7284
no. of obsd reflcns (I > 2σ(I)) 1358
4706
351
0.214
0.073
no. of params
115
wR2 (all data)
R value (I > 2σ(I))
0.093
0.032
bond lengths and angles observed for 1. 4 is the first
monoalkynylzirconium complexes,15 characterized by
X-ray analysis, which has an amido ligand core. The
Zr-Calkynyl distance (2.281(7)Å) is slightly longer than
the averaged Zr-Csp bond (2.237(13)Å)16 length and
indicates a weak Zr σ-alkynyl bond. The molecular
structure of 4 verifies that the sterically demanding
trimethylsilyl substituents of the ligand core do protect
the metal-carbon bond.
Several conclusions can be drawn from this study.
First, aminopyridinato ligands can stabilize a new type
of monomolecular zirconium complexes due to the
strained η2 binding mode. Second, the tris(aminopy-
ridinato)zirconium moiety forms stable alkyl, aryl, and
alkynyl complexes. Third, the sterically demanding
TMS groups of the ligand protect the metal-carbon
σ-bonds by a propeller-like arrangement. We are con-
tinuing to explore the potential utility of aminopyridi-
nato ligands for organometallic chemistry and extend
our studies to other early transition metals.
(11) Chisholm, M. H.; Hammond, C. E.; Huffman, J . C. Polyhedron
1988, 7, 2515.
(12) Sample mean and standard deviation of 18 Zr-Npy bonds
distances by using QUEST and VISTA.19
(13) Sample mean and standard deviation of 66 Zr-Namido bond
distances by using QUEST and VISTA.19
(14) Lappert, M. F.; Power, P. P.; Sanger, A. R.; Srivastava, R. C.
Metal and Metalloid Amides; Ellis Norwood Ltd.: Chichester, England,
1980.
(15) Wielstra, Y.; Gambarotta, S.; Meetsma, A.; de Boer, J . L.;
Chiang, M. Y. Organometallics 1989, 8, 2696. Hou, Z.; Breen, T. L.;
Stephan, D. W. Organometallics 1993, 11, 3158. Lemke, F. R.; Szalda,
D. J .; Bullock, R. M. J . Am. Chem. Soc. 1991, 113, 8466. Walsh, P. J .;
Hollander, F. J .; Bergman, R. G. J . Organomet. Chem. 1992, 428, 13.
(16) Sample mean and standard deviation of 6 Zr-Csp bond dis-
tances by using QUEST and VISTA.19

Notes
Organometallics, Vol. 15, No. 3, 1996 1073
Sch em e 1. Syn th esis of Tr is(a m in op yr id in a to)zir con iu m σ-Alk yl, -Ar yl, a n d -Alk yn yl Com p lexes
materials were performed with rigorous exclusion of oxygen
and moisture in dried Schlenk-type glassware on a dual
manifold Schlenk line, interfaced to a high-vacuum line, or in
an argon-filled Vacuum Atmospheres glovebox (mBraun lab-
master 130) with a high-capacity recirculator (<1.5 ppm O2).
Solvents (Aldrich) and NMR solvents (Cambridge Isotope
Laboratories all 99 atom % D) were freshly distilled from
sodium tetraethylaluminate.
Exp er im en ta l Section
Ma ter ia ls a n d P r oced u r es. 4-Methyl-2-((trimethylsilyl)-
amino)pyridine7 was prepared according to a previously pub-
lished procedure. All other reagents were obtained commer-
cially and used as supplied. All manipulations of air-sensitive
P h ysica l Mea su r em en ts. NMR spectra were recorded on
a Bruker ARX 400 instrument with variable-temperature unit.
1H and 13C chemical shifts are referenced to the solvent
resonances and reported relative to TMS. 29Si chemical shifts
are reported relative to TMS. Melting points were determined
in sealed capillaries on a Bu¨chi 535 apparatus. Elemental
analysis were performed with a Leco CHNS-932 elemental
analyzer. X-ray diffraction data were collected on a CAD4
MACH3 diffractometer using graphite-monochromated Mo KR
radiation. The crystals were mounted in a cold nitrogen
stream or sealed inside a capillary. An absorption correction
was carried out by a ψ-scan. The structure was solved by
direct methods (SHELXS-86)17 and refined by full-matrix least-
squares techniques against F2 (SHELXL-93).18 XP (Siemens
Analytical X-ray Instruments, Inc.) was used for structure
representations.
(TMS-AP )3Zr -Cl (1). To a solution of 4-methyl-2-((tri-
methylsilyl)amino)pyridine (6.56 mL, 22.4 mmol) in ether (35
mL) was added slowly via syringe a 1.6 M hexane solution of
MeLi (14 mL, 22.4 mmol) at -70 °C. The mixture was allowed
to warm to room temperature over a period of 20 min, ZrCl4
(1.74 g, 7.46 mmol) was added over a period of 20 min, and
the mixture was stirred for a further 5 h. A white solid
precipitated. The solution was filtered, and the volume was
reduced under vacuum to approximately 10 mL. Cooling to
-30 °C overnight afforded a colorless crystalline material.
Yield: 4.11 g, 6.18 mmol, 83%. 1H NMR (303 K, C6D6) (δ):
7.26 (d, J ) 5.6 Hz, 1H, H-6); 6.24 (s, 1 H, H-3); 5.86 (d, J )
5.6 Hz, 1 H, H-5); 1.76 (s, 3 H, Me); 0.43 (s, 9 H, SiMe3). 13C
NMR (303 K, C6D6) (δ): 168.1 (C-2); 152.0 (C-4); 142.1 (C-6);
112.2 (C-3); 111.4 (C-5), 21.7 (Me); 1.2 (SiMe3). Anal. Calcd
F igu r e 2. Perspective ORTEP drawing of the molecular
structure of 4. All non- hydrogen atoms are represented
by thermal ellipsoids drawn to encompass 40% probability.
Selected bond distances and angles: C(1)-C(2) 1.184(9),
C(1)-Zr 2.281(7), C(2)-C(3) 1.453(9), C(20)-N(1) 1.356-
(8), C(20)-N(2) 1.359(7), C(24)-N(2) 1.338(8), C(30)-N(3)
1.354(8), C(30)-N(4) 1.368(8), C(34)-N(4) 1.340(8), C(40)-
N(5) 1.351(8), C(40)-N(6) 1.354(8), C(40)-C(41) 1.424(9),
C(44)-N(6) 1.335(7), N(1)-Si(1) 1.730(5), N(1)-Zr 2.210-
(5), N(2)-Zr 2.318(5), N(3)-Zr 2.198(5), N(4)-Zr 2.299(5),
N(5)-Zr 2.202(5), N(6)-Zr 2.314(5); C(2)-C(1)-Zr 170.2-
(7), C(1)-C(2)-C(3) 176.9(8), N(1)-C(20)-N(2) 110.0(5),
N(3)-C(30)-N(4) 110.1(5), N(5)-C(40)-N(6) 110.9(5),
C(30)-N(3)-Si(2) 128.1(4),), N(3)-Zr-N(5) 121.8(2), N(3)-
Zr-N(1) 118.5(2), N(5)-Zr-N(1) 119.0(2), N(3)-Zr-N(4)
59.4(2), N(5)-Zr-N(4) 138.9(2), N(1)-Zr-N(4) 80.7(2),
N(3)-Zr-N(6) 81.4(2), N(5)-Zr-N(6) 59.1(2), N(1)-Zr-
N(6) 141.0(2), N(4)-Zr-N(6) 82.6(2), N(3)-Zr-N(2) 139.9-
(2), N(5)-Zr-N(2) 80.2(2), N(1)-Zr-N(2) 58.7(2), N(4)-
Zr-N(2) 81.7(2), N(6)-Zr-N(2) 84.1(2).
(17) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(18) Sheldrick G. M. SHELXL-93: A program for crystal structure
refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1993.
(19) QUEST, VISTA: program’s for structure search and bond
parameter statistics; Cambridge Crystallographic Data Center: Cam-
bridge, U.K., 1994.

1074 Organometallics, Vol. 15, No. 3, 1996
Notes
for C27H45ClN6Si3Zr: C, 48.79; H, 6.82; N, 12.64. Found: C,
49.07; H, 6.42; N, 12.65.
Calcd for C33H50N6Si3 Zr: C 56.12; H, 7.14; N, 11.94. Found:
C, 56.13; H,7.33; N, 11.94.
(TMS-AP )3Zr -CtCP h (4). To a solution of phenylacety-
lene (109 µL, 1.00 mmol) in ether (30 mL) was added slowly
via syringe a 1.6 M hexane solution of MeLi (0.62 mL, 1.00
mmol) at -70 °C. The mixture was allowed to warm to room
temperature and was stirred over a period of 1 h. 1 (0.66 g,
1.00 mmol) was added slowly, and the mixture was stirred for
a further 18 h. A white solid precipitated. The solution was
filtered, and the volume was reduced under vacuum to
approximately 10 mL. Cooling to -30 °C afforded over night
a colorless crystalline material. Yield: 0.49 g, 0.67 mmol, 67%.
1H NMR (303 K, C6D6) (δ): 7.75 (d, J ) 8.7 Hz, 2 H, o-Ph);
7.35 (d, J ) 5.4 Hz, 3H, H-6); 7.11 (tr, 2 H, m-Ph); 6.98 (tr, 1
H, p-Ph); 6.26 (s, 3 H, H-3); 5.89 (d, J ) 5.4 Hz, 3 H, H-5);
1.77 (s, 9 H, Me); 0.51 (s, 27 H, SiMe3). 13C NMR (303 K, C6D6)
(δ): 168.2 (C-2); 151.8 (C-4); 142.8 (C-6); 111.9, 111.6 (C-3, C-5),
21.3 (Me); 0.9 (SiMe3); 152.5, 103.9 (CtC); 131.4, 128.5, 126.3
((TMS-AP )3Zr -Me (2). To a solution of 1 (0.33 g, 0.50
mmol) in ether (30 mL) was added slowly via syringe a 1.6 M
hexane solution of MeLi (310 µL, 0.50 mmol) at -70 °C. The
mixture was allowed to warm to room temperature over a
period of 20 min and stirred for another 3 h. A white solid
precipitated. The solution was filtered, and the volume was
reduced under vacuum to approximately 10 mL. Cooling to
-30 °C afforded overnight a colorless crystalline material.
Yield: 0.206 g, 0.32 mmol, 64%. 1H NMR (303 K, C6D6) (δ):
7.38 (d, J ) 5.6 Hz, 3 H, H-6); 6.26 (s, 3 H, H-3); 5.85 (d, J )
5.6 Hz, 3 H, H-5); 1.76 (s, 9 H, Me); 0.93 (s, 3 H, Me-Zr); 0.38
(s, 27 H, SiMe3). 13C NMR (303 K, C6D6) (δ): 168.9 (C-2); 151.4
(C-4); 142.8 (C-6); 112.0 (C-3), (111.5 C-5), 47.6 (Me-Zr); 21.6
(Me); 1.1 (SiMe3). Anal. Calcd for C28H48N6Si3Zr: C, 52.21;
H, 7.51; N, 13.05. Found: C, 52.19; H, 7.60; N, 13.06.
(TMS-AP )3Zr -P h (3). To a solution of 1 (0.41 g, 0.62
mmol) in ether (30 mL) was added slowly via syringe a 1.8 M
hexane solution of phenyllithium (350 µL, 0.63 mmol) at -70
°C. The color changed to light yellow immediately. The
mixture was allowed to warm to room temperature over a
period of 30 min and stirred for another 18 h. A white solid
precipitated. The solution was filtered, and the volume was
reduced under vacuum to approximately 10 mL. Cooling to
-30 °C afforded overnight a yellow crystalline material.
Yield: 0.30 g, 0.42 mmol, 68%. 1H NMR (303 K, C6D6) (δ):
7.97 (d, J ) 7.9 Hz, 2 H, o-Ph); 7.64 (d, J ) 5.7 Hz, 3 H, H-6);
7.30 (tr, 2 H, m-Ph); 7.20 (m, 1 H, p-Ph); 6.30 (s, 3 H, H-3);
5.92 (d, J ) 5.7 Hz, 3 H, H-5); 1.76 (s, 9 H, Me); 0.20 (s, 27 H,
SiMe3). 13C NMR (303 K, C6D6) (δ): 190.5 (ipso-Ph); 171.3 (C-
2); 151.7 (C-4); 143.7 (C-6); 135.9 (o-Ph); 126.7 (m-Ph); 126.0
(p-Ph); 112.7 (C-3); 111.4 (C-5), 21.6 (Me); 1.3 (SiMe3). Anal.
(o-, m-, p-Ph); 127.3 (ipso-Ph). IR (Nujol): 2078 (CtC) cm-1
.
Anal. Calcd for C35H50N6Si3Zr: C, 57.56; H, 6.90; N, 11.51.
Found: C, 57.28; H, 6.80; N, 11.52.
Ack n ow led gm en t. We thank Prof. U. Rosenthal for
generous support and helpful discussions. Financial
support by the Fonds der Chemischen Industrie and the
Max-Planck-Gesellschaft is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, positional parameters, full bond distances and angles,
and thermal parameters (16 pages). Ordering information is
given on any current masthead page.
OM9507282