Insertion reactions into the metal-alkyl and metal-amido bonds of 1,3-di(silyl-η-amido)cyclopentadienyl titanium and zirconium complexes

Article abstract of DOI:10.1021/om048984e

The synthesis of the methyl complexes [M{η⁵-C ₅H₃-1,3-(SiMe₂-η-NtBu)₂}Me] (M = Ti, Zr) and the results of the insertion reactions into their metal-methyl bonds have been investigated and compared with

Full text of DOI:10.1021/om048984e

2424
Organometallics 2005, 24, 2424-2432
Insertion Reactions into the Metal-Alkyl and
Metal-Amido Bonds of
1,3-Di(silyl-η-amido)cyclopentadienyl Titanium and
Zirconium Complexes
Jesu´s Cano, Mar´ıa Sudupe, Pascual Royo,* and Marta E. G. Mosquera
Departamento de Quı´mica Inorga´nica, Facultad de Quı´mica, Universidad de Alcala´,
Campus Universitario, E-28871 Alcala´ de Henares, Spain
Received December 22, 2004
The synthesis of the methyl complexes [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}Me] (M ) Ti, Zr)
and the results of the insertion reactions into their metal-methyl bonds have been
investigated and compared with the similar reactions previously reported for related metal-
amido [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}(NMe2)] (M ) Ti, Zr) and metal-benzyl [M{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}(CH2Ph)] (M ) Ti, Zr) compounds. The structural characterization of
the resulting η2-iminocarbamoyl [Zr{η5-C5H3-1,3-(SiMe2-η-NtBu)2}{η2-C(NMe2)dN(2,6-
Me2C6H3)}], η2-iminoacyl [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}(η2-CR′dNR)] (M ) Zr, R ) 2,6-
Me2C6H3, R′ ) CH2Ph, Me; M ) Zr, R ) tBu, R′ ) Me; M ) Ti, R ) 2,6-Me2C6H3, R′ ) Me),
and alkoxo [Zr{η5-C5H3-1,3-(SiMe2-η-NtBu)2}{OC(CH2Ph)Ph2}] complexes and of the asym-
metrical bicyclic enediamido compound [Ti(η5-C5H3-1,3-{(SiMe2-η-NtBu)(SiMe2-NtBu-C(η-
NR)dC(Me)(η-NR)}] (R ) 2,6-Me2C6H3), formed by coupling iminoacyl and iminocarbamoyl
ligands, is also described. The molecular structures of the zirconium complexes [Zr{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}Me] and [Zr{η5-C5H3-1,3-(SiMe2-η-NtBu)2}{η2-C(CH2Ph)dN(2,6-Me2C6H3)}]-
and the titanium derivative [Ti(η5-C5H3-1,3-{(SiMe2-η-NtBu)(SiMe2-NtBu-C(η-NR)dC(Me)-
(η-NR)}] (R ) 2,6-Me2C6H3) have been determined by X-ray diffraction studies.
Introduction
We have reported previously9,10 a new class of group
4 metal complexes with a tridentate cyclopentadienyl
ligand tethered by two silyl-η-amido groups. These
The migratory insertion of unsaturated molecules into
the metal-alkyl bonds of transition metal complexes is
one of the most important organometallic reactions
employed to form C-C bonds under mild conditions.
Many catalytic applications and stoichiometric trans-
formations are based on the reactivity of the products
resulting from these basic insertion reactions.1 Versatile
transformations of acyl and particularly iminoacyl
systems have been reported for cyclopentadienyl group
42,3 and group 54 metal complexes, and important
carbonylation reactions are known for late transition
metal compounds.5,6 Insertion of isocyanides into metal-
amido bonds has been less widely studied,7 and such
insertions are only exceptionally8 preferred to insertions
into metal-alkyl bonds.
(3) (a) Choukroun, R.; Lorber, C.; Lepetit, C.; Donnadieu, B. Orga-
nometallics 2003, 22, 1995. (b) Lutz, M.; Haukka, M.; Pakkanen, T.
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Martin, A.; Mena, M.; Pellinghelli, M. A.; Royo, P.; Serrano, R.;
Tiripicchio, A. J. Chem. Soc., Dalton Trans. 1993, 2117 (e) Berg, F. J.;
Petersen, J. L. Organometallics 1991, 10, 1599. (f) Tilley, T. D. J. Am.
Chem. Soc. 1985, 107, 4084. (g) Campion, B. K.; Falk, J.; Tilley, T. D.
J. Am. Chem. Soc. 1987, 109, 2049.
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I.; Gomez-Sal, M. P.; Royo, P. Organometallics 2001, 20, 4623. (c)
Alcalde, M. I.; Gomez-Sal, M. P.; Royo, P. Organometallics 1999, 18,
546. (d) Alcalde, M. I.; Gomez-Sal, P.; Martin, A.; Royo, P. Organo-
metallics 1998, 17, 1144. (e) Gomez, M.; GomezSal, P.; Jimenez, G.;
Martin, A.; Royo, P.; SanchezNieves, J. Organometallics 1996, 15, 3579.
(f) Galakhov, M. V.; Gomez, M.; Jimenez, G.; Pellinghelli, M. A.; Royo,
P.; Tiripicchio, A. Organometallics 1994, 13, 1564. (g) Galakhov, M.
V.; Gomez, M.; Jimenez, G.; Royo, P.; Pellinghelli, M. A.; Tiripicchio,
A. Organometallics 1995, 14, 2843.
* Corresponding author. Tel: 34918854765. Fax: 34 918854683.
E-mail: pascual.royo@uah.es.
(5) Kiss, G. Chem. Rev. 2001, 101, 3435.
(6) Sugihara, T.; Yamaguchi, M.; Nishizawa, M. Chem.-Eur. J. 2001,
7, 1589.
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C.; Baumgartner, J.; Marschner, C. Organometallics 2003, 22, 3723.
(b) Zhang, Y. H.; Keaton, R. J.; Sita, L. R. J. Am. Chem. Soc. 2003,
125, 8746. (c) Martins, A. M.; Ascenso, J. R.; de Azevedo, C. G.; Dias,
A. R.; Duarte, M. T.; da Silva, J. F.; Veiros, L. F.; Rodrigues, S. S.
Organometallics 2003, 22, 4218. (d) Thorn, M. G.; Lee, J.; Fanwick, P.
E.; Rothwell, I. P. J. Chem. Soc., Dalton Trans. 2002, 3398. (e) Barriola,
A. M.; Cano, A. M.; Cuenca, T.; Fernandez, F. J.; GomezSal, P.;
Manzanero, A.; Royo, P. J. Organomet. Chem. 1997, 542, 247. (f)
Campora, J.; Buchwald, S. L.; Gutierrezpuebla, E.; Monge, A. Orga-
nometallics 1995, 14, 2039. (g) Bendix, M.; Grehl, M.; Frohlich, R.;
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11, 122. (i) Bochmann, M.; Wilson, L. M.; Hursthouse, M. B.; Short, R.
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Richeson, D. S. Organometallics 2000, 19, 2573. (c) Broder, C. K.;
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10.1021/om048984e CCC: $30.25 © 2005 American Chemical Society
Publication on Web 04/07/2005

Cyclopentadienyl Ti and Zr Complexes
Organometallics, Vol. 24, No. 10, 2005 2425
Chart 1
Scheme 1
the structural characterization of the resulting η2-
iminocarbamoyl [Zr{η5-C5H3-1,3-(SiMe2-η-NtBu)2}{η2-
C(NMe2)dN(2,6-Me2C6H3)}], η2-iminoacyl [M{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}(η2-CR′)NR)] (M ) Zr, R ) 2,6-
Me2C6H3, R′ ) CH2Ph, Me; M ) Zr, R ) tBu, R′ ) Me;
M ) Ti, R ) 2,6-Me2C6H3, R′ ) Me), alkoxo [Zr{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}{OC(CH2Ph)Ph2}], and enediamido
[Ti{η5-C5H3-1-(SiMe2-η-NtBu)-3-[SiMe2-NtBu-C(η-NR)d
C(Me)(η-NR)]}] complexes by elemental analysis, NMR
spectroscopy, and X-ray diffraction methods.
doubly silyl-bridged group 4 metal (CG) amido chelates
activated with MAO are efficient catalysts for ethene
polymerization despite generating cationic species with-
out the alkyl group required for the insertion reaction.
Subsequently, a related singly silyl-η-amido zirconium
dicyclopentadienyl compound was reported,11 which was
also found to be an efficient catalyst for olefin polym-
erization when treated with aluminum activators. Simi-
lar observations have been made more recently for
12
Co(I)-R alkyl compounds when treated with B(C6F5)3
or MAO13 and for Co(I)-Cl compounds, without alkyl
groups, which show ethene polymerization activity when
treated with LiB(C6F5)4.14
Results and Discussion
Synthesis and Characterization of Methyl Com-
plexes. The metal-amido [M{η5-C5H3-1,3-(SiMe2-η-
NtBu)2}(NMe2)] (M ) Ti 1, Zr 2) and metal-benzyl
[M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}(CH2Ph)] (M ) Ti 3, Zr
4) complexes were easily accessible by deprotonation of
the di(silylamino)cyclopentadiene C5H4[SiMe2(NHtBu)]2
with strongly basic metal amides [M(NMe2)4]18 and
metal benzyls [M(CH2Ph)4]19 as reported previously.9,10
However a different synthetic method has to be used to
prepare the related methyl derivatives [M{η5-C5H3-1,3-
(SiMe2-η-NtBu)2}Me] (M ) Ti 5, Zr 6). They were easily
obtained by total alkylation of the mono-cyclopenta-
dienyl complexes [M{η5-C5H3-1,3-(SiMe2NHtBu)2}Cl3]20
(M ) Ti, Zr) using excess MgClMe, followed by thermal
deprotonation with elimination of methane, as shown
in Scheme 1. This reaction pathway is consistent with
the intermediate formation of the dimethyl compound
[Ti{η5-C5H3-1,3-(SiMe2-η-NtBu)(SiMe2NHtBu)}Me2],
Following the same analogy15,16 used to relate the
silyl-η-amido complexes to bent metallocene systems,
the di(silyl-η-amido)cyclopentadienyl compounds might
be related to tris(cyclopentadienyl)17 systems. An analy-
sis of the frontier orbitals based on DFT calculations10
carried out for this model predicts the high energy of
the LUMO orbital of the formally 16-electron [M{η5-
C5H3-1,3-(SiMe2-η-NR)2}R′] species, which can be used
to coordinate the unsaturated insertion reagent (CO,
OCPh2, CNR), and only when strongly σ-donor ligands
are used does its occupation provide a weak interaction.
Moreover, this is the orbital involved in the η2-coordina-
tion of the resulting iminoacyl and iminocarbamoyl
ligands.
Generally, a low tendency to undergo insertion reac-
tions should be expected for these types of di(silyl-η-
amido)cyclopentadienyl complexes. It was therefore
convenient to study the reactivity of the neutral di(silyl-
η-amido)cyclopentadienyl complexes represented in Chart
1 and their capacity to undergo insertion reactions of
various unsaturated molecules into their unique metal-
alkyl and metal-amido bonds.
1
which was detected by its H NMR spectrum (Ti-Me
singlets at δ 0.69 and 0.78) after stirring the solution
for 12 h at room temperature, although the alternative
pathway with initial deprotonation of at least one of the
NHtBu groups followed by salt elimination cannot be
ruled out.
These methyl compounds were isolated as light yellow
5 and light brown 6 solids in 98% and 85% yield,
respectively, and were identified by NMR spectroscopy
as Cs symmetric molecules with two equivalent Cp-silyl-
η-amido ligands. Crystals of 6 suitable for X-ray dif-
fraction studies were obtained by recrystallization from
pentane at -35 °C. The molecular structure of 6 is
depicted in Figure 1, and selected bond distances and
angles are summarized in Table 1.
The crystal structure of 6 is the first example of a
neutral zirconium compound with a tridentate cyclo-
pentadienyl ligand tethered by two silyl-η-amido groups
and confirms that the zirconium atom is in a pseudo-
tetrahedral coordination mode largely similar to that
found for the related benzyl titanium complex [Ti{η5-
We report herein the synthesis of the new methyl
derivatives [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}Me] (M )
Ti, Zr) and the use of these and the already reported9,10
benzyl [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}(CH2Ph)] (M )
Ti, Zr) and amido [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}-
(NMe2)] (M ) Ti, Zr) complexes for a comparative study
of the insertion reactions into their metal-methyl,
metal-benzyl, and metal-amido bonds. We also report
(10) Cano, J.; Royo, P.; Jacobsen, H.; Blacque, O.; Berke, H.;
Herdtweck, E. Eur. J. Inorg. Chem. 2003, 2463.
(11) Jin, J. Z.; Wilson, D. R.; Chen, E. Y. X. Chem. Commun. 2002,
708.
(12) Gibson, V. C.; Humphries, M. J.; Tellmann, K. P.; Wass, D. F.;
White, A. J. P.; Williams, D. J. Chem. Commun. 2001, 2252.
(13) Kooistra, T. M.; Knijnenburg, Q.; Smits, J. M. M.; Horton, A.
D.; Budzelaar, P. H. M.; Gal, A. W. Angew. Chem., Int. Ed. 2001, 40,
4719.
(14) Steffen, W.; Blomker, T.; Kleigrewe, N.; Kehr, G.; Frohlich, R.;
Erker, G. Chem. Commun. 2004, 1188.
(15) Hoffmann, R. Angew. Chem., Int. Ed. Engl. 1982, 21, 711.
(16) Williams, D. N.; Mitchell, J. P.; Poole, A. D.; Siemeling, U.;
Clegg, W.; Hockless, D. C. R.; Oneil, P. A.; Gibson, V. C. J. Chem. Soc.,
Dalton Trans. 1992, 739.
(17) Jacobsen, H.; Berke, H.; Brackemeyer, T.; Eisenblatter, T.;
Erker, G.; Frohlich, R.; Meyer, O.; Bergander, K. Helv. Chim. Acta
1998, 81, 1692.
(18) Lappert, M. F.; Power, P. B.; Sanger, A. R.; Srivastava, R. C.
Metal and Metalloid Amines; Ellis Horwood: Chinchester, 1980.
(19) Zucchini, U.; Albizzat, E.; Giannini, U. J. Organomet. Chem.
1971, 26, 357.
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Chem. 2004, 3074.

2426 Organometallics, Vol. 24, No. 10, 2005
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 6, 9, and 13
Cano et al.
6
9
13
2.0891
M-Cga
M-N(1)
M-N(2)
M-L
2.1457
2.1932
2.123(2)
2.112(2)
2.318(3) (C10)
2.163(4)
2.167(4)
2.175(4) (N3)
2.271(5) (C30)
1.728(4)
1.739(4)
1.286(6)
1.985(3)
1.936(3) (N4)
2.028(3) (N3)
1.762(3)
N(1)-Si(1)
N(2)-Si(2)
C(30)-N(30)
C(40)-N(4)
M-C(30)
1.738(2)
1.735(3)
1.740(3)
1.410(4)
1.397(4)
2.334(3)
M-C(40)
2.385(3)
C(30)-C(40)
Cg-M-N(1)
Cg-M-N(2)
Cg-M-L
1.411(5)
101.23
100.52
100.51
101.21
105.54
120.37 (N3)
124.38 (N4)
110.90 (C10)
142.86 (C30)
109.64 (N3)
M-N(1)-Si(1)
M-N(2)-Si(2)
N(1)-Si(1)-C(1)
N(2)-Si(2)-C(4)
N(1)-M-N(2)
N(1)-M-L
104.26(12)
104.92(11)
103.80(13)
104.47(14)
94.49(14)
95.52(12)
94.84(12)
131.32(10)
128.16(14)
106.16(10) (C10)
105.77(10) (C10)
100.02(16) C(30)
95.59(16) C(30)
108.52(15)(N3)
111.44(15) (N3)
69.1(3)
N(2)-M-L
106.38(12) (N3)
111.69(11) (N4)
N(3)-C(30)-M(1)
C(30)-N(3)-M(1)
C(40)-N(4)-M(1)
N(3)-M(1)-C(1)
77.4(3)
86.97(16)
86.24(18)
33.54(15)
a Cg denotes the centroid of the ring.
higher electron donation of the double silylamido bridge10
to the metal center.
The Cg-Zr-N [100.52°, 101.23°], Zr-N-Si
[104.26(12)°, 104.92(11)°], and C-Si-N [95.52(12)°,
94.84(12)°] angles of the chelated cyclic systems are in
the normal range found for related compounds11,21-29
or for the cationic doubly bridged complex [Zr{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}{(CH2Ph)B(C6F5)3}]:10 Cg-Zr-N
[100.84°, 101.20°], Zr-N-Si [105.56(8)°, 105.68(8)°], and
C-Si-N [93.65(8)°, 92.94(9)°].
Insertion Reactions. We have studied the insertion
reactions of carbon monoxide (CO), benzophenone
(OCPh2), and the isocyanides CNR (R ) tBu, 2,6-
Me2C6H3) into the metal-amido and metal-alkyl bonds
of the di(silyl-η-amido)cyclopentadienyl titanium and
zirconium [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}R] (M ) Ti,
Zr; R ) NMe2, Me, CH2Ph) complexes.
We first observed that CO did not react with any of
these compounds. This lack of reactivity may be due to
the weak electron-donating character of CO, which
prevents the coordination of the unsaturated substrate
to the metal center in the step before the migratory
Figure 1. Molecular structure of complex [Zr{η5-C5H3-1,3-
(SiMe2-η-NtBu)2}Me], 6. Thermal ellipsoids are drawn at
the 30% probability level. Hydrogen atoms are omitted for
the sake of clarity.
C5H3-1,3-(SiMe2-η-NtBu)2}(CH2Ph)].10 The N-M-N
angle is slightly more open in 6 [131.32(10)°] than in
the cationic species [M{η5-C5H3-1,3-(SiMe2-η-NtBu)2}-
{(CH2Ph)B(C6F5)3}]9,10 [Ti 126.89(6)°, Zr 126.3(2)°] or in
the benzyl titanium compound [Ti{η5-C5H3-1,3-(SiMe2-
η-NtBu)2}(CH2Ph)] [128.05(6)°].9
(22) Okuda, J.; Schattenmann, F. J.; Wocadlo, S.; Massa, W.
Organometallics 1995, 14, 789.
The Zr-N distances for the silyl-η-amido ligands
[2.123(2) and 2.112(2) Å] are slightly longer than those
observed in the singly silyl-bridged bis(dimethylamido)
derivative [Zr(η5-C5Me4SiMe2-η-NtBu)(NMe2)2]21 for the
Zr-NtBu [2.010(4) Å] and for the Zr-NMe2 [2.060(5),
2.064(4) Å] bonds. However, the Cg-Zr distance [2.1457
Å] is shorter than that observed [2.233 Å] in the same
complex. These differences are in agreement with the
(23) Li, L. T.; Metz, M. V.; Li, H. B.; Chen, M. C.; Marks, T. J.;
Liable-Sands, L.; Rheingold, A. L. J. Am. Chem. Soc. 2002, 124, 12725.
(24) Ciruelos, S.; Sebastian, A.; Cuenca, T.; Gomez-Sal, P.; Manza-
nero, A.; Royo, P. J. Organomet. Chem. 2000, 604, 103.
(25) Gentil, S.; Pirio, N.; Meunier, P.; Gallucci, J. C.; Schloss, J. D.;
Paquette, L. A. Organometallics 2000, 19, 4169.
(26) Hair, G. S.; Jones, R. A.; Cowley, A. H.; Lynch, V. Inorg. Chem.
2001, 40, 1014.
(27) Kloppenburg, L.; Petersen, J. L. Organometallics 1997, 16,
3548.
(28) Herrmann, W. A.; Morawietz, M. J. A.; Priermeier, T. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1946.
(29) Mu, Y.; Piers, W. E.; MacQuarrie, D. C.; Zaworotko, M. J. Can.
J. Chem.-Rev. Can. Chim. 1996, 74, 1696.
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L. Organometallics 1996, 15, 1572.

Cyclopentadienyl Ti and Zr Complexes
Organometallics, Vol. 24, No. 10, 2005 2427
Scheme 2
Scheme 3
tions8 the metal-alkyl bonds undergo preferential
insertion of organic isocyanides.
As it would be expected, the formally 18-electron
dimethylamido derivatives 1 and 2 did not react with
CNtBu after being treated for several days at temper-
atures higher than 100 °C. As shown in Scheme 3, the
insertion reaction was only observed for the zirconium
complex 2, despite its stronger Zr-N bond, when its
toluene solution treated with CN(2,6-Me2C6H3) was
heated for 4 h at 100 °C, whereas the titanium complex
1 was recovered unchanged under the same conditions.
The different reactivity observed for the titanium and
zirconium complexes is consistent with the steric hin-
drance of the bulkier CNtBu ligand and the larger size
of the zirconium atom.
insertion.1 It is also consistent with the absence of a
vacant metal orbital in the formally 18-electron metal-
amido compounds if the three amido ligands are con-
sidered as three-electron donors and the high energy of
the vacant metal orbital in the 16-electron metal-alkyl
complexes.
The resulting iminocarbamoyl complex [Zr{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}{η2-C(NMe2)dN(2,6-Me2C6H3)}] (8)
was isolated as a yellow oily solid and characterized by
elemental analysis and NMR spectroscopy.
Benzophenone did not react with the amido titanium
and zirconium complexes despite its more electron-
donating character. However, insertion was observed
when it was added to a toluene solution of the benzyl
zirconium complex 4 (see Scheme 2), where the conver-
sion into the alkoxo derivative [Zr{η5-C5H3-1,3-(SiMe2-
η-NtBu)2}{OC(CH2Ph)Ph2}] (7) was complete after heat-
ing for 3 h at 50 °C. Complex 7 was isolated as a yellow
microcrystalline solid and characterized by elemental
analysis and NMR spectroscopy. However, a similar
reaction into the zirconium-methyl bond of complex 6
did not occur, as expected from an electronic perspective
due to the lower electron-withdrawing effect of the
methyl substituent. Insertion of benzophenone also was
not observed in the titanium methyl 5 and benzyl 3
complexes, probably due to the steric crowding associ-
ated with the smaller radius of the titanium atom.
The 1H NMR spectrum of complex 7 shows the
expected signals for the equivalent silyl-η-amido arms
and one singlet at δ 3.61 due to the equivalent meth-
ylene protons of the benzyl group which is bound to a
Csp3 atom and observed in the 13C spectrum as a low-
field-shifted resonance at δ 88.3, which corresponds to
an alkoxo ligand. This behavior confirms that the
structure of complex 7 is similar to those described
below for complexes 8 and 9.
The isocyanides CNR (R ) tBu, 2,6-Me2C6H3) are
much more reactive substrates, consistent with their
higher electron-donating capacity, although remarkable
differences in reactivity are related to their different
electrophilic character and steric requirements, the less
electronegative and bulkier R substituents providing the
less reactive substrates, particularly for the more
protected titanium compounds. This is consistent with
the lower reactivity observed for the more bulky and
less electrophilic CNtBu compared with the more reac-
tive CN(2,6-Me2C6H3) for any of the insertion reactions
studied. On the other hand, the higher π-bonding
contribution makes the metal-amido bond more resis-
tant to insertion reactions, and with very few excep-
The 1H and 13C NMR spectra are consistent with the
structure proposed in Scheme 3 for compound 8. The
metal, the carbon, and the two nitrogen atoms of the
η2-iminocarbamoyl moiety are located in a plane of
symmetry responsible for the equivalency of both NtBu
ligands (δ 0.38) and the two aryl-methyl groups of the
iminoacyl Me2ArN (δ 2.04) fragment. Nevertheless, the
two methyl groups of the migrated dimethylamido
ligand are not equivalent and appear as two singlets in
the 1H NMR spectrum at δ 2.03 and 2.95. This behavior
is consistent with the location of both amido-methyl
groups in the plane of symmetry, indicating the high
barrier of rotation of the C(sp2)-NMe2 bond due to a
significant π-bonding contribution. The most relevant
features observed in the 13C NMR spectrum of 8 are the
low-field signal (δ 213.7) due to the ipso carbon of the
η2-iminocarbamoyl ligand and the low value of the
difference ∆(δCtert - δCMe)30 of 18.4, indicating the
small π-bonding contribution of the bridging silylamido
ligands, which is lower for the more electron-donating
iminocarbamoyl ligands than for the iminoacyl deriva-
tives described below.
The benzyl complexes 3 and 4 did not react when their
toluene solutions were heated with CNtBu at temper-
atures between 20 and 120 °C for several days. However
insertion of CN(2,6-Me2C6H3) into the zirconium-benzyl
bond of complex 4 was observed to give a quantitative
conversion into the η2-iminoacyl complex [Zr{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}{η2-C(CH2Ph)dN(2,6-Me2C6H3)}] (9)
after heating to 60 °C for 4 h (see Scheme 2). Complex
9 was isolated as a brown solid and identified by
elemental analysis and NMR spectroscopy; its molecular
structure was determined by X-ray diffraction studies.
The 1H and 13C NMR spectra of 9 show the presence
of one tBu (δ 1.21) and two SiMe2 (δ 0.46 and 0.66)
(30) The difference ∆(δCtert - δCMe) in M-NtBu moieties defines
the π-bonding contribution in the M-N bond. Wigley, D. E. In Progress
in Inorganic Chemistry; John Wiley & Sons Inc: New York, 1994; Vol.
42, p 239.

2428 Organometallics, Vol. 24, No. 10, 2005
Cano et al.
Scheme 4
complex 6. This is consistent with the less pπ(N)-dπ-
(Zr) and Cp-dπ(Zr) π-bonding contribution due to the
lower electron deficiency of the metal center in a
formally 18-electron species containing a three-electron-
donor iminoacyl ligand.
The crystal structure confirms that the Zr1-C30-
N3 cycle, the methylene group C31, and the ring ipso
carbon connected to N3 are coplanar (max. deviation
0.054 Å). The nitrogen (N3) and the carbon (C30) atoms
maintain a trigonal-planar environment and are sp2
hybridized, consistent with the angle sums of 359.3° and
357.9°, respectively.
The orientation of the imino-N facilitates the interac-
tion between the lone pair of its pπ orbital with the
LUMO metal orbital to complete the 18-electron con-
figuration. The monoinsertion reaction in singly bridged
compounds produces a pseudo-square-pyramidal coor-
dination.31 However, the diinsertion in the dialkyl
derivative [Zr{η5-C5Me4(SiMe2-η-NtBu)}Me2] affords a
pseudo-octahedral configuration27 in which, depending
on the R substituent of the isocyanide, one atom of the
iminoacyl groups occupies the axial or the equatorial
position. When R ) tBu, one of the imido-N atoms is in
the axial position trans to the cyclopentadienyl ring, but
when R is a less sterically demanding group (2,6-
Me2C6H3), one of the imido-N fragments is located in
an equatorial position.
Figure 2. Molecular structure of complex [Zr{η5-C5H3-1,3-
(SiMe2-η-NtBu)2}{η2-C(CH2Ph)dN(2,6-Me2C6H3)}], 9. Ther-
mal ellipsoids are drawn at the 30% probability level.
Hydrogen atoms are omitted for the sake of clarity.
singlets corresponding to two symmetrical SiMe2NtBu
units of a Cs symmetric molecule in which the Zr and
the N and C atoms of the iminoacyl ligand define the
plane of symmetry where the aryl and benzyl-meth-
ylidene carbon atoms are also contained. This structural
disposition is similar to that proposed above for the
related iminocarbamoyl derivative 8 and is consistent
with the equivalency of the two aryl-methyl and tBu
groups observed as singlets at δ 1.85 and 1.21, respec-
tively, in the 1H NMR spectrum of 8. In contrast to the
behavior discussed above for the iminocarbamoyl com-
plex 8, the free rotation of the C(sp2)-CH2Ph bond also
makes the two benzyl methylidene protons observed as
one singlet at δ 3.72 equivalent. The most significant
signal in the 13C NMR spectrum is that observed at δ
265 for the ipso carbon of the η2-iminoacyl ligand.
The structure proposed for complex 9 was finally
confirmed by the X-ray diffraction studies of a single
crystal obtained by recrystallization from pentane at
-35 °C.
The molecular structure of 9 is represented in Figure
2 along with the labeling system, and bond distances
and angles are summarized in Table 1. The zirconium
center of complex 9 shows a profoundly distorted tri-
gonal bipyramidal coordination in which the equatorial
plane is defined by the iminoacyl-N3 and the two
silylamido-N1 and -N2 atoms and the apical positions
are occupied by the cyclopentadienyl ring and the
iminoacyl-C30 atom. However the constrained Zr1-
C30-N3 cycle due to the η2-coordination of the imino-
acyl ligand with a short C30-N3 double bond is
responsible for the distortion observed for C30, which
is located at a Cg-Zr1-C30 angle of 142.86° (37° away
from the linear disposition) rather than occupying the
axial position trans to the cyclopentadienyl ring. The
silylamido Zr1-N1 and Zr1-N2 [2.163(4) and 2.167(4)
Å], the ring-centroid Zr-Cg [2.1932 Å], and the Zr-
CCp [between 2.494(5) and 2.518(5) Å] bond distances
are slightly longer than those observed for the methyl
The 13C NMR spectrum is also consistent with this
proposal and provides additional evidence for the high
electron density of the metal resulting from the η2-
coordination of the iminoacyl ligand, as shown by the
low value of the difference (∆δ ) 19.1),30 which is an
indication of the low π-bonding contribution of the
bridging silylamido ligand.
We may conclude that the reactivity of the metal-
benzyl bonds is similar to that observed for the related
metal-amido bonds, despite being formally 16-electron
compounds with one vacant metal orbital. The reactivity
found for OCPh2 and CN(2,6-Me2C6H3) follows the order
of their σ-donor character, whereas the steric hindrance
of the bulkier CNtBu ligand may explain its lack of
reactivity. Similar electronic effects together with the
smaller radius of the titanium and the steric require-
ments of the ligands used for insertion may be invoked
to justify the lack of reactivity of the benzyl-titanium
complex 3.
When similar reactions were studied for the sterically
less demanding methyl complexes 5 and 6, insertion of
isocyanide was feasible for both zirconium and titanium
complexes when the isocyanides CNR (R ) 2,6-Me2C6H3,
tBu) were used. As shown in Scheme 4, addition of 1
equiv of CNR to toluene solutions of the zirconium
complex 6 gave the iminoacyl complexes [Zr{η5-C5H3-
1,3-(SiMe2-η-NtBu)2}(η2-CMedNR)] (R ) 2,6-Me2C6H3
(31) Amor, F.; Butt, A.; du Plooy, K. E.; Spaniol, T. P.; Okuda, J.
Organometallics 1998, 17, 5836.

Cyclopentadienyl Ti and Zr Complexes
Organometallics, Vol. 24, No. 10, 2005 2429
Scheme 5
10, tBu 11). Formation of 10 proceeded cleanly at room
temperature, whereas heating at 50 °C was required to
obtain 11 and complete transformation was observed
after 12 h. Complexes 10 and 11 were isolated as light
brown solids and characterized by elemental analysis
Figure 3. Molecular structure of complex 13. Thermal
ellipsoids are drawn at the 30% probability level. Hydrogen
atoms are omitted for the sake of clarity.
1
and NMR spectroscopy. The H and 13C NMR spectra
This proposal was confirmed by the molecular struc-
ture determined by X-ray diffraction studies on a single
crystal of 13 isolated from a pentane solution cooled to
-20 °C. Figure 3 shows a drawing of the molecular
structure of 13, and selected bond lengths and angles
are listed in Table 1.
are consistent with the structure found for complex 8,
with two symmetric silyl-η-amido arms and the η2-
iminoacyl ligand located in the plane of symmetry.
Although no reaction was observed for the methyl
titanium complex 5 with CNtBu, a slow and more
complex reaction was observed when 1 equiv of CN(2,6-
Me2C6H3) was added to a toluene solution of complex 5
heated to 75 °C for 24 h. As shown in Scheme 5, the
insertion led initially to the formation of the corre-
sponding iminoacyl complex 12, unreacted starting
material, and a new compound 13, which was the
unique reaction product when 4 equiv of excess CN(2,6-
Me2C6H3) were added and the reaction mixture heated
at 120 °C for 24 h. Pure compound 12 could not be
isolated, whereas the new complex 13 was isolated as a
red crystalline solid and identified by elemental analysis
and NMR spectroscopy. The molecular structure of 13
was also determined by X-ray diffraction methods.
The 1H and 13C NMR spectra of 13 show the presence
of two tBu (δ 0.84 and 0.99), four SiMe (δ 0.43, 0.53,
0.66, and 0.67), and four aryl-Me (δ 1.85, 2.05, 2.41, and
2.69) singlets corresponding to an asymmetric molecule.
In addition, two resonances at δ 111.8 and 128.1 were
observed in the gHMBC spectrum which were assigned
to an asymmetric chelating -N-CdC-N- moiety. These
spectral features are consistent with the presence of an
asymmetric enediamido ligand formed by coupling of
two C(sp2) atoms, one from the η2-iminoacyl ligand,
resulting from the insertion of CNAr into the Ti-Me
bond, and the other from the η2-iminocarbamoyl ligand,
resulting from insertion of a second molecule of CNAr
into the Ti-NtBu bond of one of the silyl-η-amido arms.
The formation of the intermediate compound was de-
tected when the reaction was monitored by 13C NMR
spectroscopy in a Teflon-valved NMR tube. On heating
at 90 °C for 48 h, a mixture of 12, 13, and this
intermediate complex, with its characteristic η2-iminoa-
cyl (δ 246) and η2-iminocarbamoyl (δ 212) signals, was
observed. To the best of our knowledge, this is a unique
example of coupling reaction between iminoacyl and
iminocarbamoyl ligands to give a type of the known
diazabutadiene complexes containing a 2-methyl-3-
amido-dad ligand in which TiN2C2 framework “flipping”
is prevented by the bond to the pendant silyl-η-amido
bridge.
The titanium atom is at the center of a distorted
pseudotetrahedral coordination defined by the centroid
of the η5-cyclopentadienyl ring, the N of the appended
silyl-η-amido ligand, and the two N-donors of an asym-
metric-chelating enediamido ligand generated by the
intramolecular C,C-coupling of the η2-iminoacyl and η2-
iminocarbamoyl groups. The Ti-Cg distance [2.0891 Å],
where Cg is the centroid of the cyclopentadienyl ligand,
and the Ti-N2 bond distance [1.984(3) Å] for the
pendant silyl-η-amido ligand are similar to those found
for singly bridged dimethylamido derivatives [Ti(η5-C5-
Me4SiMe2-η-NtBu)(NMe2)2].21 The Ti-N3 and Ti-N4
distances [1.936(3) and 2.028(3) Å] for the enediamido
ligand are significantly different, the Ti-N3 bond
distance being similar to the Ti-N2 bond, whereas the
Ti-N4 distance is unexpectedly 0.09 Å longer. The
N(4)-C(40) and N(3)-C(30) bond distances of 1.397(4)
and 1.410(4) Å are consistent with the presence of single
C-N bonds, and the C30-C40 distance of 1.411(5) Å is
in the range expected for a CdC double bond. The five-
membered TiN2C2 ring of the dad ligand is folded along
the N(3)-N(4) axis by 65.8°, providing the less favorable
prone orientation observed for dad-Ti compounds in
solution,32,33 forced by the bond to the pendant amido
group, in contrast with the supine conformation reported
for group 4 enediamido complexes.27,32-34 The Ti-C30
and Ti-C40 bond lengths of 2.334(3) and 2.385(3) Å are
in the range expected for the π-coordination to the
CdC bond to the titanium center.
Conclusions
We have found that the di(silyl-η-amido)cyclopenta-
dienyl titanium and zirconium complexes are rather
(32) Amor, F.; Gomez-Sal, P.; Royo, P.; Okuda, J. Organometallics
2000, 19, 5168.
(33) Scholz, J.; Hadi, G. A.; Thiele, K. H.; Gorls, H.; Weimann, R.;
Schumann, H.; Sieler, J. J. Organomet. Chem. 2001, 626, 243.
(34) Pindado, G. J.; Thornton-Pett, M.; Bochmann, M. J. Chem. Soc.,
Dalton Trans. 1998, 393.

2430 Organometallics, Vol. 24, No. 10, 2005
Cano et al.
(NtBuipso), 115.5 (C5H3-ipso), 126.4 (C5H3), 130.1 (C5H3). Anal.
Found: C 55.99, H 9.39, N 7.16. Calc: C 56.22, H 9.44, N 7.28.
Preparation of [Zr{η5-C5H3-1,3-[SiMe2-η-NtBu)]2}Me]
(6). MgClMe (0.49 mL, 1.49 mmol), 3 M in THF, was added to
a solution of [Zr{η5-C5H3-1,3-(SiMe2NHtBu)2}Cl3] (0.25 g, 0.49
mmol) in toluene (50 mL) at -78 °C. The reaction mixture was
then warmed to room temperature and stirred under reflux
for 12 h. The solvent was then removed under vacuum, and
the residue was extracted into hexane (2 × 25 mL). After
filtration and removal of the solvent, complex 6 was isolated
as a light brown solid (0.18 g, 0.42 mmol, 85%). 1H NMR (300
MHz, C6D6, 20 °C, TMS): δ 0.13 (s, 3H, ZrMe), 0.45 (s, 6H,
SiMe), 0.46 (s, 6H, SiMe), 1.28 (s, 18H, NtBu), 6.58 (br s, 3H,
C5H3). 13C NMR (300Mz, C6D6, 20 °C, TMS): 2.6 (SiMe), 3.0
(SiMe), 26.4 (ZrMe), 35.3 (tBuN), 55.3 (NtBuipso), 115.5
(C5H3-ipso), 123.8 (C5H3), 131.6 (C5H3). Anal. Found: C 49.93,
H 8.41, N 6.55. Calc: C 50.53, H 8.48, N 6.55.
stable molecules with a very low acidic character that
show the metal center sterically protected by two bulky
tBu groups. For these reasons their M-NMe2, M-Bz,
and M-Me bonds show a limited reactivity where only
selected reagents and favorable conditions produce
insertion reactions. The absence of reactivity observed
for insertion of CO might be associated with the low
σ-donor capacity of this ligand, and the reactivity found
for OCPh2 and CNR follows the order of their σ-donor
character. The lack of reactivity of the benzyl- and the
dimethylamido-titanium complexes in comparison with
the higher reactivity observed for the zirconium deriva-
tives demonstrates that these insertion reactions are
controlled by steric requirements. The M-NMe2 and
M-CH2Ph bonds are sterically more protected and less
reactive than the M-Me bonds, justifying the idea that
only CN(2,6-Me2C6H3) can be inserted into the Zr-
NMe2 and Zr-CH2Ph bonds.
Preparation of [Zr{η5-C5H3-1,3-[SiMe2-η-NtBu)]2}{η-
OC(CH2Ph)(C6H5)2}] (7). A solution of 4 (0.53 g, 1.05 mmol)
in toluene (40 mL) was added to a suspension of benzophenone
(126 mg, 1.05 mmol) in the same solvent at room temperature.
The mixture was stirred for 3 h at 50 °C. After removal of the
solvent under vacuum the residue was extracted into hexane
(25 mL), and after filtration and removal of the hexane
complex 7 (0.62 g, 0.91 mmol, 95%) was isolated as a yellow
microcrystalline solid. 1H NMR (300 MHz, C6D6, 20 °C,
TMS): δ 0.52 (s, 6H, SiMe2), 0.55 (s, 6H, SiMe2), 1.34 (s, 18H,
NtBu), 3.61 (s, 2H, CH2Ph), 5.59 (m, 1H, C5H3), 6.91 (m, 2H,
C5H3), 6.9-7.7 (m, 15H, C6H5). 13C NMR (300 MHz, C6D6, 20
°C, TMS): δ 3.4 (SiMe2), 3.4 (SiMe2), 36.1 (NtBu), 50.4 (CH2-
Ph), 55.2 (NtBu), 88.3 (OCipso), 118.6 (C5H3-ipso), 120.8 (C5H3),
126.3 (C5H3), 127-131 (15C, Ph), 135.5 (C6H3-ipso), 137.8
(C6H3-ipso), 148.1 (C6H5-ipso). Anal. Found: C 64.33, H 7.63, N
3.91. Calc: C 64.76, H 7.34, N 4.08.
The steric hindrance of the bulkier CNtBu ligand may
explain its lack of reactivity with the benzyl- and
dimethylamido-zirconium complexes.
The higher electron-withdrawing effect of Bz in rela-
tion to Me groups could explain why benzophenone (a
weak σ-donor ligand) reacts with [Zr{η5-C5H3-1,3-(SiMe2-
η-NtBu)2}(CH2Ph)] (4) but not with [Zr{η5-C5H3-1,3-
(SiMe2-η-NtBu)2}Me] (6). The milder conditions required
in all of the insertion reactions with CN(2,6-Me2C6H3),
compared with CNtBu, may be due to its lower steric
demands and the higher electrophilic character of its
carbon atom involved in the nucleophilic migratory
insertion.
The reaction of 5 with excess CN(2,6-Me2C6H3) pro-
ceeds via a double insertion reaction that leads to the
formation of an intermediate species containing η2-
iminoacyl and η2-iminocarbamoyl ligands, which un-
dergo an unprecedented further CdC coupling reaction
to produce an asymmetrical bicyclic enediamido com-
plex.
Preparation of [Zr{η5-C5H3-1,3-[SiMe2-η-NtBu)]2}{η2-
C(NMe2)dN(2,6-Me2C6H3)}] (8). CN(2,6-Me2C6H3) (0.12 g,
0.92 mmol) was added to a solution of 2 (0.42 g, 0.92 mmol) in
toluene (40 mL). The mixture was heated for 4 h at 100 °C.
The solvent was removed under vacuum, and the residue was
extracted into pentane (25 mL). After filtration and removal
of the solvent complex 8 was isolated as a yellow oil (0.49 g,
1
0.83 mmol, 91%). H NMR (300 MHz, C6D6, 20 °C, TMS): δ
0.57 (s, 6H, SiMe2), 0.72 (s, 6H, SiMe2), 1.38 (s, 18H, NtBu),
2.04 (s, 3H, NMe2), 2.05 (s, 6H, Me2C6H3), 2.95 (s, 3H, NMe2),
6.11 (m, 2H, C5H3), 7.18 (m, 1H, C5H3). 13C NMR (300 MHz,
C6D6, 20 °C, TMS): δ 3.1 (SiMe2), 5.7 (SiMe2), 19.8 (Me2C6H3),
36.5 (NtBu), 45.0 (NMe2), 54.9 (NtBu), 119.3 (C5H3-ipso), 120.2
(C5H3), 124.9 (C5H3), 128.3 (C6H3), 130.6 (C6H3), 131.4 (C6H3),
150.2 (C6H3-ipso), 213.7 (CNipso). Anal. Found: C 57.57, H 8.31,
N 9.41. Calc: C 57.18, H 8.23, N 9.53.
Experimental Section
General Procedures. All manipulations were performed
under an inert atmosphere of argon using standard Schlenk
techniques or a drybox. Solvents used were previously dried
and freshly distilled under argon: tetrahydrofuran from
sodium benzophenone ketyl; toluene from sodium; hexane from
sodium-potassium amalgam. Unless otherwise stated, re-
agents were obtained from commercial sources and used as
received. 1H and 13C NMR spectra were recorded on a Varian
Unity VXR-300 or Varian Unity 500 Plus instruments. Chemi-
Preparation of [Zr{η5-C5H3-1,3-[SiMe2-η-NtBu)]2}{η2-
C(CH2Ph)dN(2,6-Me2C6H3)}] (9). A solution of 4 (0.41 g, 0.81
mmol) in toluene (40 mL) was added to a suspension of CN-
(2,6-Me2C6H3) (0.11 g, 0.81 mmol) in the same solvent at room
temperature. The mixture was stirred for 4 h at 60 °C. After
removal of the solvent under vacuum the residue was extracted
into hexane (25 mL), and after filtration and removal of the
hexane complex 9 (0.44 g, 0.70 mmol, 86%) was isolated as a
1
cal shifts, in ppm, are measured relative to residual H and
13C resonances for benzene-d6 used as solvent [7.15 (1H) and
128.0 (13C)], and coupling constants are in Hz. C, H, and N
analysis were carried out with a Perkin-Elmer 240 C analyzer.
Preparation of [Ti{η5-C5H3-1,3-[SiMe2-η-NtBu)]2}Me]
(5). MgClMe (0.35 mL, 1.05 mmol), 3 M in THF, was added to
a solution of [Ti{η5-C5H3-1,3-(SiMe2NHtBu)2}Cl3] (0.16 g, 0.3
mmol) in toluene (50 mL) to -78 °C. The reaction mixture was
then warmed to room temperature and stirred under reflux
for 12 h. The solvent was then removed under vacuum, and
the residue was extracted into hexane (2 × 50 mL). After
filtration and removal of the solvent, complex 5 was isolated
as a light yellow solid (0.12 g, 0.32 mmol, 98%). 1H NMR (300
MHz, C6D6, 20 °C, TMS): δ 0.41 (s, 6H, SiMe), 0.42 (s, 6H,
SiMe), 0.59 (s, 3H, TiMe), 1.40 (s, 18H, NtBu), 6.46 (m, 1H,
C5H3), 6.61 (m, 2H, C5H3). 13C NMR (300Mz, C6D6, 20 °C,
TMS): 1.4 (SiMe), 1.9 (SiMe), 34.7 (NtBu), 39.5 (TiMe), 57.8
1
light brown solid. H NMR (300 MHz, C6D6, 20 °C, TMS): δ
0.46 (s, 6H, SiMe2), 0.66 (s, 6H, SiMe2), 1.21 (s, 18H, NtBu),
1.85 (s, 6H, Me2C6H3), 3.72 (s, 2H, CH2Ph), 6.21 (m, 1H, C5H3),
7.3 (m, 2H, C5H3), 6.82-7.30 (m, 8H, C6H5). 13C NMR (300
MHz, C6D6, 20 °C, TMS): δ 2.9 (SiMe2), 5.2 (SiMe2), 18.9
(Me2C6H3), 36.4 (NtBu), 46.7 (CH2Ph), 55.5 (NtBu), 119.3
(C5H3), 119.6 (C5H3-ipso) 126.1 (C5H3), 126.8 (C6H5), 128.3
(C6H5), 128.6 (C6H5), 128.7 (C6H5), 130.8 (C6H5), 131.7 (C6H5),
135.9 (C6H3-ipso), 147.5 (C6H5-ipso), 265.0 (CNipso). Anal.
Found: C, 62.31 H 7.83, N 6.53. Calc: C 62.40, H 7.78, N 6.62.
Preparation of [Zr{η5-C5H3-1,3-[SiMe2-η-NtBu)]2)}{η2-
CMedN(2,6-Me2C6H3)}] (10). Toluene (20 mL) was added to
a mixture of complex 6, [Zr{η5-C5H3-1,3-(SiMe2-η-NtBu)2}Me]

Cyclopentadienyl Ti and Zr Complexes
Organometallics, Vol. 24, No. 10, 2005 2431
Table 2. Crystallographic Data for the X-ray Structural Analysis of 6, 9, and 13
6
9
13
empirical formula
fw
C18 H36 N2 Si2 Zr
427.89
colorless/block
0.71 0.479 0.433
monoclinic
C33 H49 N3 Si2 Zr
635.15
yellow/prism
0.561 0.443 0.108
monoclinic
P21/c (No.14)
11.119(2)
C36 H54 N4 Si2 Ti
646.91
orange/block
0.412 0.396 0.194
triclinic
color, shape
cryst size (mm)
cryst syst
space group
a (Å)
P21/n (No.14)
11.3691(15)
13.9028(9)
P1h (No.2)
9.7722(10)
11.3369(4)
17.0066(16)
98.372(6)
102.866(10)
99.863(7)
1776.2(3)
2
b (Å)
19.430(4)
15.805(2)
c (Å)
15.137(2)
R (deg)
â (deg)
108.131(12)
106.355(11)
γ (deg)
V (Å3)
2273.8(4)
4
3276.4(10)
4
Z
T (K)
200
200
200
F
calcd (mg m-3
)
1.250
1.288
1.210
F000
904
1344
696
radiation
λ (Å)
Mo
Mo
Mo
0.71073
0.591
0.71073
0.434
0.71073
µ (mm-1
)
0.338
θ range (deg)
3.06-27.50
(14,+18/-17, (19
18 641
5211/0.0727
3843
208
3.01-27.53
(14, (25, (20
27 467
7529/0.1751
4388
350
3.04-27.50
(12, (14, (22
36 668
data collected (h,k,l)
no. of reflns collected
no. of indep reflns/Rint
no. of obsd reflns [I> 2σ(I)]
no. of params refined
R1 (obsd/all)
8058/0.0663
5192
388
0.0402/0.0683
0.0886/0.1001
1.065
0.0636/0.1359
0.1210/0.1446
1.020
0.0641/0.1097
0.1466/0.1654
1.023
wR2 (obsd/all)
GOF
max./min. ∆F (e Å-3
)
0.847/-0.540
0.534/-0.653
0.551/-0.449
(0.55 g, 1.29 mmol), and xylyl isocyanide, CN(2,6-Me2C6H3)
(0.16 g, 1.29 mmol). The reaction mixture was then stirred
for 12 h at room temperature. The solvent was removed under
vacuum and the residue extracted into pentane (20 mL). After
filtration and removal of the solvent complex 10 was isolated
as a light brown solid (0.66 g, 1.19 mmol, 93%). 1H NMR (300
MHz, C6D6, 20 °C, TMS): δ 0.47 (s, 6H, SiMe), 0.69 (s, 6H,
SiMe), 1.30 (s, 18H, tBuN), 1.82 (s, 6H, Me2C6H3), 2.05 (s, 3H,
CMe), 6.28 (m, 2H, C5H3), 6.88-6.98 (m, 3H, C6H3) 7.14 (m,
1H, C5H3). 13C NMR (300Mz, C6D6, 20 °C, TMS): 3.0 (SiMe),
4.9 (SiMe), 18.4 (Me2C6H3), 23.4 (CMe), 36.3 (tBuN), 55.6
(NtBuipso), 119.2 (C5H3), 119.6 (C5H3-ipso), 126.0 (C5H3), 128.6
(C6H3), 132.0 (C6H3), 147.1 (C6H3-ipso), 267.1 (CNipso). Anal.
Found: C 57.61, H 8.28, N 7.41. Calc: C 58.01, H 8.11, N 7.52.
Preparation of [Ti(η5-C5H3{(SiMe2-η-NtBu)(SiMe2-NtBu-
C(η-NR)dC(Me)(η-NR)}], R ) (2,6-Me2C6H3) (13). Four
equivalents of CN(2,6-Me2C6H3) (0.23 g, 1.80 mmol) were
added to a solution of 5 (0.17 g, 0.45 mmol) in toluene (15 mL)
at room temperature. The reaction mixture was heated to 75
°C for 24 h and to 120 °C for another 24 h. The solvent was
then removed under vacuum and the residue extracted into
pentane (20 mL). After filtration and removal of the solvent
complex 13 was isolated as a red solid (0.23 g, 0.35 mmol, 80%).
1H NMR (300 MHz, C6D6, 20 °C, TMS): 0.43 (s, 3H, SiMe),
0.53 (s, 3H, SiMe), 0.66 (s, 6H, SiMe), 0.84 (s, 9H, tBu), 0.99
(s, 9H, tBu), 1.85 (s, 3H, CMe), 2.05 (s, 3H, Me2C6H3), 2.41 (s,
3H, Me2C6H3), 2.69 (s, 3H, Me2C6H3), 2.71 (s, 3H, Me2C6H3),
5.92 (m, 1H, C5H3), 6.83 (m, 1H, C5H3), 6.84 (m, 1H, C6H3),
6.84 (m, 1H, C6H3), 6.87 (m, 2H, C6H3), 7.01 (m, 1H, C5H3),
7.02 (m, 2H, C6H3). 13C NMR (300 MHz, C6D6, 20 °C, TMS):
1.7 (SiMe), 2.9 (SiMe), 4.0 (SiMe), 7.0 (SiMe), 19.4 (CMe), 20.7
(Me2C6H3), 21.8 (Me2C6H3), 23.9 (Me2C6H3), 24.3 (Me2C6H3),
32.0 (NtBu), 33.6 (NtBu), 55.2 (NtBuipso), 59.2 (NtBuipso), 110.9
(C5H3-ipso), 111.8 (CMeipso), 119.7 (C5H3), 121.6 (C5H3-ipso), 122.2
(C5H3), 123.5 (C5H3), 124.4 (C6H3), 126.8 (C6H3), 127.3 (C6H3),
128.1 (CdCMeipso), 128.6 (C6H3), 129.7 (C6H3), 130.9 (C6H3),
133.2 (C6H3), 133.3 (C6H3), 147.6 (C6H3-ipso), 151.1 (C6H3-ipso).
Anal. Found: C 66.84, H 8.41, N 8.76. Calc: C 66.84, H 8.41,
N 8.66.
Crystal Structure Determination. Selected crystals of
6, 9, and 13 were mounted on the top of a glass fiber using
perfluoropolyether oil and cooled to 200 K. Data collection was
performed on a Nonius KappaCCD single-crystal diffractome-
ter. Crystal structure was solved by direct methods and refined
using full-matrix least squares on F2. All non-hydrogen atoms
were anisotropically refined except for three carbon atoms in
a disordered phenyl ring in compound 9. All H atoms were
placed in calculated positions and refined using a riding model.
Crystallographic data and details of refinement of 6, 9, and
13 are summarized in Table 2.
Preparation of [Zr{η5-C5H3-1,3-[SiMe2-η-NtBu)]2)}{η2-
CMedNtBu}] (11). CNtBu (0.034 g, 0.40 mmol) was added
to a solution of 6 (0.17 g, 0.41 mmol) in toluene (20 mL) at
room temperature. The reaction mixture was then heated to
50 °C and stirred for 12 h. The solvent was then removed
under vacuum and the residue extracted into pentane (20 mL).
After filtration and removal of the solvent complex 11 was
isolated as a light brown oily solid (0.18 g, 0.36 mmol, 91%).
1H NMR (300 MHz, C6D6, 20 °C, TMS): δ 0.48 (s, 6H, SiMe),
0.70 (s, 6H, SiMe), 1.07 (s, 9H, tBuN), 1.20 (s, 18H, tBuN),
2.55 (s, 3H, CMe), 6.67 (m, 2H, C5H3), 7.23 (m, 1H, C5H3). 13
C
NMR (300Mz, C6D6, 20 °C, TMS): 2.8 (SiMe), 5.4 (SiMe), 24.3
(CMe), 29.7 (CNtBu), 36.3 (tBuN), 55.3 (NtBuipso), 62.2 (CMe3),
117.4 (C5H3-ipso), 120.1 (C5H3), 132.9 (C5H3), 258.6 (CMe). Anal.
Found: C 53.92, H 8.94, N 7.97. Calc: C 54.06, H 8.88, N 8.22.
Formation of [Ti{η5-C5H3-1,3-[SiMe2-η-NtBu)]2)}{η2-
CMedN(2,6-Me2C6H3)}] (12). Transformation of complex 5
into complex 12 is slow, and it is not complete although more
than 1 equiv was added to a solution of complex 5 in benzene
and the reaction mixture heated to 70 °C. Formation of
complex 13 was observed before the transformation of 5 into
12 was complete. Isolation of complex 12 was not possible. 1H
NMR of 12 (300 MHz, C6D6, 20 °C, TMS): δ 0.45 (s, 6H, SiMe),
0.71 (s, 6H, SiMe), 1.33 (s, 18H, tBuN), 1.78 (s, 6H, Me2C6H3),
2.14 (s, 3H, CMe), 6.20 (m, 2H, C5H3), 6.80-7.1 (m, 3H,
Me2C6H3), 7.30 (m, 1H, C5H3).
Acknowledgment. The authors acknowledge MEC
(project MAT2004-02614) and DGU-CM (project GR/

2432 Organometallics, Vol. 24, No. 10, 2005
Cano et al.
lengths, bond angles, and thermal displacement parameters
for complex 6, 9, and 13 in CIF format. This material is
available free of charge via the Internet at http://pubs.acs.org.
MAT/0622/2004) for financial support. J.C. and M.S.
acknowledge CAM and MECD, respectively, for fellow-
ships.
Supporting Information Available: Tables of crystal
data, data collection parameters, atomic coordinates, bond
OM048984E