Chemistry of group 4 metals supported by carbazole ligation

Article abstract of DOI:10.1039/b008592h

A series of new derivatives of titanium and zirconium containing carbazole ligation have been isolated and studied. Treatment of [Zr(NMe₂)₄] with carbazole (cbH) leads to the adduct [Zr(cb)₂(NMe₂)₂(NHMe₂)]. Structural studies (trigonal bipyramidal with axial cb and NMe₂) show the Zr-N(carbazole) distances to be 0.15 A longer than the Zr-NMe₂ distances. This is consistent with almost negligible nitrogen-p to metal-d π-bonding from the carbazole ligands. Treatment of [M(CH₂Ph)₄] (M = Ti or Zr) with cbH leads to the derivatives [Zr(cb)₄] and [Ti(cb)₂(CH₂Ph)₂]. The latter reacts with 2,6-dimethylphenyl isocyanide (xyNC) to generate the corresponding bis(iminoacyl) derivative, the iminoacyl carbon chemical shift of δ 246.9 in the ¹³C NMR of which indicates η²-C,N binding. The reaction of the more bulky alkyl substrate [Ti(CH₂SiMe₃)₄] with cbH at 100 °C the reaction produces a sparingly soluble, red crystalline product identified as the alkylidene bridged dimer [(cb)₂Ti(p-CHSiMe₃)₂Ti(cb)₂] which was structurally characterized. Treatment of it with xyNC (>3 equivalents) produces a single organometallic species [(cb)Ti(g-cb)-(μ-xyNCCSiMe₃ {μ-xyNCC(SiMe₃)CHNxy)Ti(cb)] and one equivalent of free carbazole. The molecular structure could only be elucidated by a solid state structure that shows it to be dinuclear, containing a total of three equivalents of isocyanide within two distinct bridging units. Two terminal and one non-symmetrically bridged carbazole ligand are also present. The reaction of [TiCpCl₃] with potassium carbazolate (Kcb) leads to formation of [TiCp(cb)Cl₂] (structurally characterized) which can readily be converted into the dimethyl [TiCp(cb)Me₂].

Full text of DOI:10.1039/b008592h

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Chemistry of Group 4 metals supported by carbazole ligation
Patrick N. Riley, Phillip E. Fanwick and Ian P. Rothwell*
Department of Chemistry, 1393 Brown Building, Purdue University, West Lafayette,
IN 47907-1393, USA
Received 24th October 2000, Accepted 30th October 2000
First published as an Advance Article on the web 22nd December 2000
A series of new derivatives of titanium and zirconium containing carbazole ligation have been isolated and studied.
Treatment of [Zr(NMe2)4] with carbazole (cbH) leads to the adduct [Zr(cb)2(NMe2)2(NHMe2)]. Structural studies
(trigonal bipyramidal with axial cb and NMe2) show the Zr–N(carbazole) distances to be 0.15 Å longer than the
Zr–NMe2 distances. This is consistent with almost negligible nitrogen-p to metal-d π-bonding from the carbazole
ligands. Treatment of [M(CH2Ph)4] (M = Ti or Zr) with cbH leads to the derivatives [Zr(cb)4] and [Ti(cb)2(CH2Ph)2].
The latter reacts with 2,6-dimethylphenyl isocyanide (xyNC) to generate the corresponding bis(iminoacyl) derivative,
the iminoacyl carbon chemical shift of δ 246.9 in the 13C NMR of which indicates η2-C,N binding. The reaction of
the more bulky alkyl substrate [Ti(CH2SiMe3)4] with cbH at 100 ЊC the reaction produces a sparingly soluble, red
crystalline product identified as the alkylidene bridged dimer [(cb)2Ti(µ-CHSiMe3)2Ti(cb)2] which was structurally
characterized. Treatment of it with xyNC (>3 equivalents) produces a single organometallic species [(cb)Ti(µ-cb)-
(µ-xyNCCSiMe3){µ-xyNCC(SiMe3)CHNxy)Ti(cb)] and one equivalent of free carbazole. The molecular structure
could only be elucidated by a solid state structure that shows it to be dinuclear, containing a total of three equivalents
of isocyanide within two distinct bridging units. Two terminal and one non-symmetrically bridged carbazole ligand
are also present. The reaction of [TiCpCl3] with potassium carbazolate (Kcb) leads to formation of [TiCp(cb)Cl2]
(structurally characterized) which can readily be converted into the dimethyl [TiCp(cb)Me2].
shown to undergo transamination reactions with amines
Introduction
resulting in the displacement of the more volatile dimethyl-
Complexes with ancillary cyclopentadienyl groups, a class of
amine group.17 The addition of two equivalents of carbazole to
ligands pioneered by Wilkinson and Birmingham,1 have
dominated many of the developments in the area of early d-
a toluene solution of [Zr(NMe2)4]18 at 100 ЊC produces the di-
substituted compound [Zr(cb)2(NMe2)2(NHMe2)] 1 (Scheme 1).
block metal chemistry. The search for new ligand systems to
replace the cyclopentadienyl ligand has been a major area of
recent research in inorganic and organometallic chemistry.
Specifically, there has been considerable interest in the organo-
metallic chemistry of the Group 4–6 metals associated with
“hard” donor ligation.2–4 Within this context the search for
new types of amido ligation is also a rapidly expanding area
of chemistry with chelating, tripodal and hybrid metallocene–
amide ligands all being developed to support novel organo-
metallic and inorganic chemistry at early transition metal
centers.5–12
In the context of this background we have been exploring
the inorganic and in particular organometallic chemistry of
ligands derived from the carbazole (cbH) nucleus. This is a
class of ligands that have so far been underutilized.13,14 The
choice of the carbazole ligand was stimulated by an expectation
that the presence of the two co-planar aryl rings would decrease
nitrogen-p to metal-d π donation, possibly leading to deriv-
atives that exhibit different chemistry than found with more
strongly π-donating dialkylamido ligation. We have previously
studied niobium and tantalum derivatives supported by carb-
azole ligation and have isolated many interesting complexes
including a ditantalum hexahydride compound and “1,3-di-
metallabenzenes”.15 In this paper we report the synthesis of
Scheme 1
a mixed carbazole–amide zirconium complex and of organo-
titanium derivatives supported by carbazole ligation. Some
The reaction was performed under an N2 atmosphere and the
aspects of this work have been communicated.16
evolved NHMe2 allowed to escape via the mercury bubbler of
a Schlenk vacuum system. Compound 1 was obtained as a pale
white crystalline material, which was only sparingly soluble in
aromatic solvents. The 3-tert-butylcarbazole derivative [Zr-
(cb-3But)2Zr(NMe2)2(NHMe2)] 2 was found to be significantly
more soluble in hydrocarbon solvents and saturated C6D6
Results and discussion
Synthesis and spectroscopic characterization of compounds
The tetra-amido zirconium compound [Zr(NMe2)4] has been
DOI: 10.1039/b008592h
J. Chem. Soc., Dalton Trans., 2001, 181–186
This journal is © The Royal Society of Chemistry 2001
181

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Scheme 2
solutions were sufficiently concentrated to detect the NMe2 and
δ 12.32, not quite as far downfield as the signals of dimeric 6.23
t-butyl carbons by 13C NMR spectroscopy.
The insolubility of 6 precluded its analysis by 13C NMR
spectroscopy.
The reaction of the zirconium tertra-benzyl [Zr(CH2Ph)4]19
with an excess of carbazole in benzene at 105 ЊC produces the
tetra-substituted derivative [Zr(cb)4] 3 (Scheme 1) and four
equivalents of toluene. Compound 3 is obtained as a yellow
crystalline material, which has very limited solubility in hydro-
carbon solvents. Unfortunately, the crystals obtained were not
The formation of the alkylidene-bridged dimer 6 occurs
by a still undetermined pathway. The reaction mixture has
yet to produce the anticipated product [Ti(cb)2(CH2SiMe3)2].
Attempts to trap this compound by conducting the reaction in
the presence of donor ligands such as pyridine or phosphines
have failed. One possible pathway for the formation of 6 is
an α-hydrogen abstraction within [Ti(cb)2(CH2SiMe3)2] and
finally dimerization. A less likely alternative is formation of
[Ti(cb)3(CH2SiMe3)] followed by elimination of free carbazole.
Treatment of compound 6 with xyNC (>3 equivalents)
slowly (1H NMR) produces a single organometallic species
[(cb)Ti(µ-cb)(µ-xyNCCSiMe3){µ-xyNCC(SiMe3)CHNxy)Ti-
(cb)] 7 (Scheme 2) and one equivalent of free carbazole. The
molecular structure of 7 could only be elucidated by a solid
state structure that shows it to be dinuclear, containing a
total of three equivalents of isocyanide within two distinct
bridging units. Two terminal and one non-symmetrically
bridged carbazole ligand are also present. The structural
parameters lead us to propose the resonance picture for 7
1
satisfactory for an X-ray diffraction study. However, the H
NMR spectrum does show the expected carbazole resonances.
Although monitoring the reaction in C6D6 solvent by 1H NMR
spectroscopy showed the formation of intermediate sub-
stitution products it was not possible to isolate them as pure
materials. Presumably, carbazole does not possess the steric
bulk necessary to selectively produce either the mono, bis or tris
substitution products.
In contrast to the above zirconium chemistry the addition
of carbazole (2 equivalents) to hydrocarbon solutions of [Ti-
(CH2Ph)4] led to the bis(benzyl) compound [Ti(cb)2(CH2Ph)2]
4 in moderate yield (Scheme 1). The spectroscopic data on
4 indicate that the benzyl ligands are η1 bound.20 Solutions
of 4 react with two equivalents of 2,6-dimethylphenyl iso-
cyanide (xyNC) to produce the bis(η2-iminoacyl) complex 5
(Scheme 1). The iminoacyl carbon chemical shift of δ 246.9 in
the 13C NMR spectrum indicates η2-C,N binding, and is within
the range of δ 215–263 found for Group 4 metal η2-iminoacyl
compounds.21
1
shown in Scheme 2. In the H NMR spectrum of 7 six well
resolved signals are observed for the ortho-methyl groups
indicating slow rotation of the three xylyl groups on the NMR
timescale.
Although the exact sequence of events leading to compound
7 is presently unknown, reasonable elementary steps for its
formation can be proposed (Scheme 2). Shown are possible
pathways for the formation of the two bridging units in 7.
Based upon the structural studies (see below) one of the
bridging units in 7 is best described as an amido-alkyne ligand.
The unit may have originated via initial α-hydrogen abstraction
to produce an alkylidyne intermediate or by hydrogen abstrac-
tion from an initially formed iminoacyl. In both cases the
The reaction of the more bulky alkyl substrate [Ti(CH2-
1
SiMe3)4]22 with carbazole is slow (as monitored by H NMR)
at ambient temperatures. At 100 ЊC it produces a sparingly
soluble, red crystalline product identified as the alkylidene
bridged dimer [(cb)2Ti(µ-CHSiMe3)2Ti(cb)2] 6 (Scheme 2). In
the 1H NMR spectrum of 6 a singlet at δ 14.75 can be assigned
to the alkylidene proton. The terminal alkylidene complex
[Ti(C H ) (᎐CHCMe )(PMe )] has its Ti᎐CH resonance at
᎐
᎐
5
5
2
3
3
182
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Table 1 Selected bond distances (Å) and angles (Њ) for [Zr(cb)2-
(NMe2)2(NHMe2)] 1
Table 2 Selected bond distances (Å) and angles (Њ) for [Ti(cb)2-
(η2-xyNCCH2Ph)2] 5
Zr–N(11)
Zr–N(21)
Zr–N(3)
2.213(3)
2.196(3)
2.022(4)
Zr–N(4)
Zr–N(5)
2.034(4)
2.439(4)
Ti–N(1)
Ti–N(2)
Ti–C(1)
C(1)–N(1)
2.017(2)
2.150(2)
2.067(3)
1.268(4)
Ti–N(31)
Ti–N(41)
Ti–C(2)
2.008(2)
2.030(2)
2.065(3)
1.281(4)
C(2)–N(2)
N(3)–Zr–N(4)
N(3)–Zr–N(11)
N(4)–Zr–N(11)
N(3)–Zr–N(5)
N(11)–Zr–N(5)
112.5(1)
90.2(1)
102.8(1)
84.6(1)
N(3)–Zr–N(21)
N(4)–Zr–N(21)
N(21)–Zr–N(11)
N(4)–Zr–N(5)
N(21)–Zr–N(5)
129.0(1)
117.1(1)
90.0(1)
90.1(1)
84.1(1)
N(1)–Ti–N(2)
C(1)–Ti–C(2)
100.54(9)
119.0(1)
N(31)–Ti–N(41)
108.5(1)
167.0(1)
hydrogen abstraction takes place by a carbazole ligand. The
other bridging unit corresponds to the insertion of two
equivalents of isocyanide into an alkylidene bridge combined
with a 1,2-hydrogen shift. The transfer of adjacent hydrogen to
iminoacyl carbon atoms has precedence.21 What is not known
is which of the two bridging units is formed first. Mechanistic
studies of the reaction pathway are hindered by the low solu-
bility of 6, i.e. during the reaction it is essentially swamped by a
large excess of xyNC throughout the reaction.
All of the above reactions involve introduction of the
carbazole ligand by protonation of suitable leaving groups by
parent carbazole. However, an alternative approach makes use
of the reagent potassium carbazolate (Kcb) which can readily
be prepared from KOH and carbazole. Hence the reaction
of [TiCpCl3] with Kcb leads to formation of [TiCp(cb)Cl2] 8
(Scheme 3). This compound is easily isolated in high yield as a
Fig. 1 Molecular structure of [Zr(cb)2(NMe2)2NHMe2)] 1.
Scheme 3
red-purple crystalline solid. The solution NMR spectroscopic
properties are as expected with single C5H5 and cb resonances.
1
In the H NMR spectrum the C5H5 protons resonate at δ 5.79
which compares well with the range of δ 5.6–5.8 for Cp protons
found in [TiCp(OAr)Cl2] derivatives isolated previously in our
laboratory.24
Treatment of [TiCp(cb)Cl2] 8 with 2 equivalents of MeLi
leads to the corresponding dimethyl compound [TiCp(cb)Me2]
9 (Scheme 3) as a red solid in good yield. The solution NMR
properties of 9 are as expected with single resonances for
the C5H5 and methyl protons. Attempts to isolate single crystals
for an X-ray diffraction study have thus far been unsuccessful.
Additional alkylation reactions with other lithium reagents
including PhLi, LiCH2CMe3 and LiCH2SiMe3 have failed to
produce isolable products. The reaction of [TiCp(cb)Cl2] 8 with
2 equivalents of PhMgCH2Cl at Ϫ78.0 ЊC produced a complex
mixture, within which was identified the known compound
[TiCp(CH2Ph)3]. It appears that the carbazole ligand is labile to
substitution.
Fig. 2 Molecular structure of [Ti(cb)2(xyNCCH2Ph)2)] 5.
of Zr–amide bonds and indicative of a significant degree of
Me2N-to-Zr π bonding.25 The >0.15 Å difference is significant
and bears out the expectation that carbazole is a weaker
π donor than dialkylamido ligands. The even longer Zr–
N(amine) distance of 2.439(4) Å is consistent with a Zr–N(sp3)
single bond and compares well with related Zr–N(neutral
donor) distances reported.12c
The molecular structure of compound 5 is shown in Fig. 2
(Table 2). It is one of the few structurally characterized Group
4 metal complexes that contain two iminoacyl ligands.26
The coordination geometry and iminoacyl parameters in 5 are
similar to that found in other Group 4 metal bis(η2-iminoacyl)
compounds,21,26 the only significant difference being the non-
parallel orientation of the iminoacyl units in 5.
Structural studies
The compounds 1, 5, 6, 7 and 8 were all subjected to single-
crystal X-ray diffraction analysis. The molecular structure
of 1 is shown in Fig. 1, and selected structural parameters
can be found in Table 1. The coordination geometry about the
zirconium atom corresponds to a distorted trigonal bipyramid
with an axial carbazole and dimethylamine ligand. The Zr–
N(carbazole) distances are 2.213(3) and 2.196(3) Å respectively.
The Zr–N(NMe2) distances are 2.022(4) and 2.034(4) Å, typical
J. Chem. Soc., Dalton Trans., 2001, 181–186
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Table 3 Selected bond distances (Å) and angles (Њ) for [(cb)2Ti-
(µ-CHSiMe3)2Ti(cb)2] 6
Table 4 Selected bond distances (Å) and angles (Њ) for [(cb)Ti(µ-cb)-
(µ-xyNCCSiMe3){µ-xyNCC(SiMe3)CHNxy)Ti(cb)] 7
Ti(1)–Ti(2)
Ti(1)–N(11)
Ti(1)–C(8)
Ti(2)–C(7)
Ti(2)–N(31)
Ti(2)–N(5)
Ti(2)–C(7)
C(7)–N(6)
C(3)–C(4)
N(1)–C(2)
2.804(2)
2.006(7)
1.970(8)
2.16(1)
2.018(7)
1.950(8)
2.16(1)
1.34(1)
1.44(1)
1.37(1)
Ti(1)–N(1)
Ti(1)–N(31)
Ti(1)–C(7)
Ti(2)–N(21)
Ti(2)–N(6)
Ti(2)–C(4)
C(7)–C(8)
C(4)–N(5)
C(2)–C(3)
2.064(7)
2.321(7)
2.097(9)
2.013(8)
1.936(7)
2.250(9)
1.34(1)
Ti ؒ ؒ ؒ TiЈ
Ti–N(29)
TiЈ–C(30)
2.9504(8)
1.969(2)
2.035(2)
Ti–N(19)
Ti–C(30)
1.950(2)
2.026(2)
N(19)–Ti–N(29)
Ti–C(30)–TiЈ
113.29(7)
93.17(9)
C(30)–Ti–C(30)Ј
N(29)–Ti–C(30)
86.83(9)
114.20(8)
1.31(1)
1.38(1)
N(11)–Ti(1)–N(1)
N(11)–Ti(1)–N(31)
N(11)–Ti(1)–C(8)
N(31)–Ti(1)–N(1)
N(1)–Ti(1)–C(8)
Ti(1)–N(1)–C(2)
Ti(1)–C(8)–C(7)
Ti(1)–C(7)–Ti(2)
101.2(3)
87.0(3)
106.4(3)
143.3(3)
99.3(3)
112.8(5)
76.0(5)
82.3(3)
N(21)–Ti(2)–N(6)
N(21)–Ti(2)–N(31)
N(6)–Ti(2)–N(5)
N(5)–Ti(2)–N(21)
N(6)–Ti(2)–N(31)
Ti(2)–N(6)–C(7)
Ti(2)–N(5)–C(4)
N(5)–C(4)–C(3)
96.9(3)
106.4(3)
117.3(3)
104.0(3)
116.8(3)
80.3(5)
84.8(5)
127.7(8)
Fig. 3 Molecular structure of [(cb)2Ti(µ-CHSiMe3)2Ti(cb)2] 6.
Fig. 3 (Table 3) shows the molecular structure for compound
6. The molecule is dimeric and consists of a crystallographically
imposed center of inversion. The coordination geometry
around each titanium atom is distorted tetrahedral. The
structural parameters for the 1,3-dimetallacyclobutane unit in 6
are similar to those found in related molecules and in particular
the methylidene bridged [(Cy2N)2Ti(µ-CH2)2Ti(NCy2)2].3 For
example the Ti–C(30) distances of 2.026(2) and 2.035(2) (Å)
in 6 compare well with the Ti–CH2 distances of 2.020(5) and
2.016(5) Å in Gamboratta’s complex.
Fig. 4 Molecular structure of [(cb)Tu(µ-cb)(µ-xyNCCSiMe3){µ-xy-
NCC(SiMe3)CHNxy)Ti(cb)] 7.
The molecular structure of compound 7 is shown in Fig. 4
(Table 4). The first non-symmetrically bridging carbazole
ligand with distances of 2.018(7) and 2.321(7)Å to the titanium
metal centers is observed. An interesting feature of the molecu-
lar structure of 7 concerns the distances within the iminoacyl
component. Specifically the Ti–N(5) and Ti–C(4) distances lead
to a value of Ϫ0.3 Å for the parameter d(Ti–N) Ϫ d(Ti–C).21
This value combined with the long C(4)–N(5) distance are
consistent with the much debated amido-carbene resonance
picture.27 The second nitrogen atom within this bridging unit
possess an amido type interaction [Ti(1)–N(1) 2.064(7)Å]. The
other bridging unit within this molecule can be described as
an amido-alkyne ligand (with some contribution from an
iminoacyl ligand). This group is bound to Ti(2) via the amido
nitrogen atom while the alkyne unit is strongly η2 bound to
Ti(1) resulting in a metallacyclopropene ring. Identical ligands
have been formed by addition of xyNC to trimethylsilyl-
methylidyne bridges in 1,3-dimetallacyclobutadiene derivatives
of Nb, Ta.15b
Fig. 5 Molecular structure of [TiCp(cb)Cl2] 8.
[TiCp*(NMe2)3],28 once again indicative of a less π-donating
carbazole ligand.
Experimental
All operations were carried out under a dry nitrogen atmos-
phere or in vacuo either in a Vacuum Atmosphere Dri-Lab or by
standard Schlenk techniques. Hydrocarbon solvents were dried
by distillation from sodium–benzophenone and stored under
dry nitrogen. The compounds 3-tert-butylcarbazole,29 Kcb,30
[Zr(NMe2)4],18 [Zr(CH2Ph)4],19 [Ti(CH2Ph)4],19 [Ti(CH2Si-
Me3)4],22 and [TiCpCl3]31 were prepared by literature methods.
9H-Carbazole was purchased from Aldrich Chemical Com-
pany, 2,6-dimethylphenyl isocyanide from Fluka Chemical
The solid state structure (Fig. 5) of compound 8 revealed
a pseudo-tetrahedral coordination environment around the
titanium metal center. The Ti-N(11) distance of 1.969(3)Å
(Table 5) is similar to the titanium–carbazole distance found
in other compounds isolated in this series. This distance is
slightly longer (ca. 0.05 Å) than the Ti–N values of
1.912(9) and 1.923(14) Å reported for the related compound
184
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Table 5 Selected bond distances (Å) and angles (Њ) for [TiCp(cb)Cl2] 8
affording a red solid. The solid was washed with hexane (25 mL)
and dried in vacuo. Calc. for C56H48N4Ti: C, 81.54; H, 5.87; N,
6.79. Found: C, 78.65; H, 5.77; N, 6.00%. H NMR (C6D6,
30 ЊC): δ 1.46 (s, MeC6H3), 3.69 (s, CH2Ph) and 6.39–8.02
(m, aromatics). 13C NMR (C6D6, 30 ЊC): δ 18.46 (MeC6H3),
43.49 (CH2Ph) and 246.9 (xyNC).
1
Ti–N(11)
Ti–Cl(1)
Ti–Cl(2)
Ti–C(1)
1.969(3)
2.236(2)
2.239(1)
2.300(5)
Ti–C(2)
Ti–C(3)
Ti–C(4)
Ti–C(5)
2.311(5)
2.329(5)
2.351(5)
2.341(5)
N(11)–Ti–Cl(1)
Cl(1)–Ti–Cl(1)
Cp–Ti–Cl(1)
102.3(1)
101.53(6)
116.3(3)
N(11)–Ti–Cl(2)
Cp–Ti–N(11)
Cp–Ti–Cl(2)
106.2(1)
115.2(2)
113.8(2)
[(cb)2Ti(ꢀ-CHSiMe3)2Ti(cb)2] 6. To a benzene (15 mL)
solution of [Ti(CH2SiMe3)4] (1.00 g, 2.25 mmol) was added
2.4 equivalents of carbazole (0.93 g, 5.56 mmol). The brown
solution was heated at 100 ЊC for 5 days during which time red
crystals precipitated. They were washed with hexane (10 mL)
and dried in vacuo. Yield: 0.74 g (71%). Calc. for C56H52N4-
Si2Ti2: C, 72.09; H, 5.62; N, 6.01. Found: C, 71.76; H, 5.55;
Company. The H and 13C NMR spectra were recorded on
Varian Associates Gemini 200 and General Electric QE-300
spectrometers and referenced to protio impurities of com-
mercial benzene-d6. Microanalyses were obtained in-house at
Purdue University.
1
1
N, 5.94%. H NMR (C6D6, 30 ЊC): δ Ϫ0.50 (s, µ-CHSiMe3),
14.75 (s, µ-CHSiMe3) and 6.6–7.8 (m, aromatics).
Syntheses
[(cb)Ti(ꢀ-cb)(ꢀ-xyNCCSiMe3){ꢀ-xyNCC(SiMe3)CHNxy)-
Ti(cb)] 7. To a toluene (5 mL) solution of [Ti(cb)2(µ-CHSi-
Me3)2Ti(cb)2] (0.10 g, 0.11 mmol) was added 3.0 equivalents of
2,6-dimethylphenyl isocyanide (0.04 g, 0.33 mmol). The brown
solution was heated at 100 ЊC for 12 h, removed and allowed to
cool slowly during which time red crystals precipitated. They
were washed with hexane (10 mL) and dried in vacuo. Calc.
for C71H74N6Si2Ti2: C, 73.69; H, 5.92; N, 7.26. Found: C, 73.52;
[Zr(cb)2(NMe2)2(NHMe2)] 1. To a toluene solution (20 mL)
of [Zr(NMe2)4] (1.00 g, 3.74 mmol) was added carbazole
(1.31 g, 7.83 mmol). The light yellow solution was heated at
100 ЊC for 24 h under N2, while allowing the evolving NHMe2
to escape via a mercury bubbler. Upon cooling a light white
solid precipitated. The solid was washed with hexane (25 mL)
and dried in vacuo. Yield: 1.57 g (75%). Calc. for C30H35N5Zr:
C, 64.71; H, 6.34; N, 12.58. Found: C, 64.46; H, 6.05; N,
1
H, 6.04; N, 7.14%. H NMR (C6D6, 30 ЊC): δ Ϫ0.14, Ϫ0.03
(s, CSiMe3); 1.17, 1.64, 1.66, 2.45, 2.47, 2.55 (s, MeC6H3).
1
11.87%. H NMR (C6D6, 30 ЊC): δ 2.92 (s, NMe2, 6 H), 1.40
(br, HNMe2, 6 H) and 7.21–8.16 (m, aromatics, 16 H).
[TiCp(cb)Cl2] 8. To a benzene (50 mL) solution of [TiCpCl3]
(2.00 g, 9.12 mmol) was added 1.1 equivalents of 9-potassio-
carbazole (2.06 g, 10.03 mmol) over 15 min. The green solution
became red and was stirred for 3.5 h, filtered, concentrated
in vacuo, and layered with hexane (1:1). The red crystals that
precipitated were washed with hexane (25 mL) and dried
in vacuo. Yield: 2.38 g (70%). Calc. for C19H13Cl2NTi: C, 61.00;
H, 3.50; Cl, 18.95; N, 3.74. Found: C, 61.01; H, 3.64; Cl, 18.84;
N, 4.08%. 1H NMR (C6D6, 30 ЊC): δ 5.79 (s, C5H5) and 6.6–7.8
(m, aromatics).
[Zr(cb-3But)2(NMe2)2(NHMe2)] 2. To a toluene solution (20
mL) of [Zr(NMe2)4] (1.00 g, 3.74 mmol) was added 3-tert-
butylcarbazole (1.75 g, 7.84 mmol). The light yellow solution
was heated at 100 ЊC for 24 h under N2, while allowing the
evolving NHMe2 to escape via a mercury bubbler. Upon
cooling a white solid precipitated. The solid was washed with
1
hexane (25 mL) and dried in vacuo. Yield: 1.98 g (85%). H
NMR (C6D6, 30 ЊC): δ 2.96 (s, NMe2, 6 H), 1.10 (br, HNMe2),
1.42 (s, CMe3, 9H) and 7.20–8.14 (m, aromatics, 16 H). 13C
NMR (C6D6, 30 ЊC): δ 32.4 (CMe3), 34.9 (CMe3) and 43.0
(NMe2).
[TiCp(cb)Me2] 9. To
a toluene (50 mL) solution of
[Zr(cb)4] 3. To a benzene (15 mL) solution of [Zr(CH2Ph)4]
(0.35 g, 0.77 mmol) was added an excess of carbazole (0.54 g,
3.2 mmol). The brown solution was heated at 105 ЊC for 18 h,
removed and allowed to cool slowly during which time yellow
crystals precipitated. They were washed with hexane (25 mL)
and dried in vacuo. Yield: 0.32 g (55%). Calc. for C48H32N4Zr:
C, 76.26; H, 4.27; N, 7.41. Found: C, 76.28; H, 3.98; N, 7.19%.
1H NMR (C6D6, 30 ЊC): δ 7.73 (d, cb ortho) and 6.8–7.4 (m,
aromatics).
[TiCp(cb)Cl2] (1.35 g, 3.61 mmol) at Ϫ78 ЊC was added a 1.4 M
diethyl ether solution of MeLi (4.15 g, 7.94 mmol) drop-
wise over 15 min. The red solution turned darker red after the
addition was complete. It was allowed to warm to room
temperature and stirred for 6 h. The solution was filtered, the
solvent removed in vacuo and the red solid recrystallized from
1
pentane. Yield: 0.68 g (61%). H NMR (C6D6, 30 ЊC): δ 1.47
(s, Ti(CH3)2, 6 H); 5.74 (s, C5H5, 10 H) and 7.04–8.08 (m,
aromatics, 16 H). 13C NMR (C6D6, 30 ЊC): δ 72.0 (CH3) and
115.3 (C5H5).
[Ti(cb)2(CH2Ph2)2] 4. To a solution of PhCH2MgCl (15.52 g,
0.103 mol) in diethyl ether (200 mL) cooled to Ϫ55 ЊC was
slowly added TiCl4 (4.65 g, 0.025 mol) in hexane (30 mL).
The resulting red mixture was stirred for 0.5 h at Ϫ40 ЊC before
carbazole (8.18 g, 0.05 mol) was added rapidly. Toluene
(200 mL) was added to aid stirring and the red solution
stirred for 18 h at 25 ЊC. The solvent was removed in vacuo to
yield a dark brown-red solid. Extraction of the solid with
benzene and filtration gave a red solution. Removal of benzene
in vacuo produced a red solid that was washed with hexane
X-Ray data collection and reduction
Crystal data and data collection parameters are contained
in Table 6. A suitable crystal was mounted on a glass fiber in
a random orientation under a cold stream of dry nitrogen.
Preliminary examination and final data collection were per-
formed with Mo-Kα radiation (λ = 0.71073 Å) on a Nonius
KappaCCD diffractometer. Lorentz and polarization correc-
tions were applied32 and an empirical absorption correction
using SCALEPACK.33 Intensities of equivalent reflections
were averaged. The structure was solved using the program
PATTY in DIRDIF 92.34 The remaining atoms were located in
succeeding Fourier difference syntheses. Hydrogen atoms were
included in the refinement but restrained to ride on the atom to
which they are bonded. The structure was refined by full-matrix
least squares where the function minimized was Σw(|Fo|2 Ϫ
|Fc|2)2. Scattering factors were taken from ref. 35. Refinement
1
(25 mL) to yield the product. Yield: 3.80 g (28%). H NMR
(C6D6, 30 ЊC): δ 3.24 (s, CH2Ph) and 6.58–7.91 (m, aromatics).
13C NMR (C6D6, 30 ЊC): δ 98.3 (s, CH2Ph).
[Ti(cb)2(xyNCCH2Ph)2] 5. To a toluene (10 mL) solution of
[Ti(cb)2(CH2Ph)2] (0.18 g, 0.32 mmol) was added 2.0 equiv-
alents of 2,6-dimethylphenyl isocyanide (0.08 g, 0.64 mmol).
The red mixture was stirred for 24 h then cooled to Ϫ15 ЊC
J. Chem. Soc., Dalton Trans., 2001, 181–186
185

View Article Online
Table 6 Crystal data and data collection parameters for complexes 1 and 5–8
1
–
1
5ؒ2C6H6
6
7
8
Formula
Formula weight
C30H35N5Zr
556.87
C59H51N4Ti
863.99
C56H52N4Si2Ti2
933.04
Ti2C71H68N6Si2
1157.35
TiC17H13NCl2
350.11
Space group
P21/n (no. 14)
12.0969(8)
16.3502(13)
14.6666(6)
C2/c (no. 15)
37.221(10)
12.153(3)
21.069(9)
P1 (no. 2)
10.0663(17)
10.481(2)
13.170(3)
109.165(15)
104.984(15)
93.619(15)
1251.1(10)
1
P21/n (no. 14)
12.7883(17)
33.329(5)
R3 (no. 148)
33.5339(12)
33.5339(12)
33.5339(12)
a/Å
b/Å
c/Å
α/Њ
14.616(3)
β/Њ
110.339(4)
104.23(3)
96.755(13)
γ/Њ
V/Å3
Z
2720.0(6)
4
9237(10)
8
6186(3)
4
7018(8)
18
T/K
R
RW
203
0.063
0.162
203
0.045
0.112
296
0.036
0.041
233
0.074
0.184
296
0.069
0.150
was performed on a AlphaServer 2100 using SHELXS 97.36
Crystallographic drawings were done using ORTEP.37
CCDC reference number 186/2266.
13 (a) G. Mosges, F. Hampel, M. Kaupp and von Rague P. Schleyer,
J. Am. Chem. Soc., 1992, 114, 10880; (b) D. Barr, A. J. Edwards,
P. R. Raithby, M.-A. Rennie and K. Verhorvoort, J. Chem. Soc.,
Chem. Commun., 1994, 1627; (c) N. Kuhn, M. Schulten, R. Boese
and D. Blaser, J. Organomet. Chem., 1991, 421, 1.
14 W. J. Evans, G. W. Rabe and J. W. Ziller, Organometallics, 1994,
13, 1641; G. B. Deacon, C. M. Forsyth, B. M. Gatehouse and
P. A. White, Aust. J. Chem., 1990, 43, 795; C. T. Abrahams,
G. B. Deacon, B. M. Gatehouse and G. N. Ward, Acta Crystallogr.,
Sect. C, 1994, 50, 504.
Acknowledgements
We thank the National Science Foundation (Grant CHE-
0078405) for financial support of this research.
15 (a) R. D. Profilet, P. E. Fanwick and I. P. Rothwell, Polyhedron,
1992, 11, 1559; (b) P. N. Riley, R. D. Profilet, P. E. Fanwick and
I. P. Rothwell, Organometallics, 1996, 15, 5502; (c) P. N. Riley,
R. D. Profilet, M. M. Salberg, P. E. Fanwick and I. P. Rothwell,
Polyhedron, 1998, 17, 773.
16 P. N. Riley, P. E. Fanwick and I. P. Rothwell, Chem. Commun., 1997,
1109.
17 M. F. Lappert, P. P. Power, A. R. Sanger and R. C. Srivastava, Metal
and Metalloid Amides, John Wiley, New York, 1980.
18 G. M. Diamond, R. F. Jordan, J. L. Petersen, J. Am. Chem. Soc.,
1996, 118, 8024.
19 G. R. Davies, J. A. J. Jarvis, B. T. Kilbourn and A. J. P. Piols,
Chem. Commun., 1971, 677; G. R. Davies, J. A. J. Jarvis and B. T.
Kilbourn, Chem. Commun., 1971, 1511.
References
1 G. W. Wilkinson and J. M. Birmingham, J. Am. Chem. Soc., 1954,
76, 4281.
2 P. W. Wanandi, W. D. Davis and C. C. Cummins, J. Am. Chem. Soc.,
1995, 117, 2110; R. K. Minhas, L. Scoles, S. Wong and S.
Gambarotta, Organometallics, 1996, 15, 1113; J. D. Scollard and
D. H. McConville, Organometallics, 1995, 14, 5478; K. Aoyagi,
P. K. Gantzel, K. Kalai and T. D. Tilley, Organometallics, 1996, 15,
923; A. D. Horton, J. de With, A. J. van der Linden and H. van de
Weg, Organometallics, 1996, 15, 2672; B. Tsuie, D. C. Swenson,
R. F. Jordan and J. P. Petersen, Organometallics, 1997, 16, 1392.
3 L. Scoles, R. Minhas, R. Duchateau, J. Jubb and S. Gambarotta,
Organometallics, 1994, 13, 4978.
4 R. P. Planalp, R. A. Andersen and A. Zalkin, Organometallics, 1983,
2, 16.
5 J. D. Scollard and D. H. McConville, J. Am. Chem. Soc., 1996, 118,
10008; P. Sinnema, L. van der Veen, A. L. Spek, N. Veldman and
J. H. Teuben, Organometallics, 1997, 16, 4245.
20 S. L. Latesky, A. K. McMullen, I. P. Rothwell and J. C. Huffman,
Organometallics, 1985, 4, 902.
21 I. P. Rothwell and L. D. Durfee, Chem. Rev., 1988, 88, 1059.
22 M. R. Collier, M. F. Lappert and R. Pearce, J. Chem. Soc., Dalton
Trans., 1973, 445.
6 C. E. Laplaza, A. R. Johnson and C. C. Cummins, J. Am. Chem.
Soc., 1996, 118, 709; A. L. Odom and C. C. Cummins, Organo-
metallics, 1996, 15, 898; C. E. Laplaza, W. M. Davis and C. C.
Cummins, Organometallics, 1995, 14, 577; C. E. Laplaza,
A. L. Odom, W. M. Davis, C. C. Cummins and J. D. Protasiewicz,
J. Am. Chem. Soc., 1995, 117, 4999; C. E. Laplaza and C. C.
Cummins, Science, 1995, 268, 861; A. R. Johnson, P. W. Wanandi,
C. C. Cummins and W. M. Davis, Organometallics, 1994, 13, 2907;
A. L. Odom, C. C. Cummins and J. D. Protasiewicz, J. Am. Chem.
Soc., 1995, 117, 6613.
7 L. Scoles, K. B. P. Ruppa and S. Gambarotta, J. Am. Chem. Soc.,
1996, 118, 2529; P. Berno and S. Gambarotta, Organometallics,
1995, 14, 2159; R. K. Minhas, Y. Ma, J.-I. Song and S. Gambarotta,
Inorg. Chem., 1996, 35, 1866.
23 H. van der Heijden and B. Hessen, J. Chem. Soc., Chem. Commun.,
1995, 145.
24 M. G. Thorn, J. S. Vilardo, P. E. Fanwick and I. P. Rothwell, Chem.
Commun., 1998, 2427; J. S. Vilardo, M. G. Thorn, P. E. Fanwick and
I. P. Rothwell, Chem. Commun., 1998, 2425.
25 M. H. Chisholm, C. E. Hammond and J. C. Huffman, Polyhedron,
1988, 7, 2515.
26 L. R. Chamberlain, L. D. Durfee, P. E. Fanwick, L. M. Kobriger,
S. L. Latesky, A. K. McMullen, I. P. Rothwell, K. Folting,
J. C. Huffman, W. E. Streib and R. Wang, J. Am. Chem. Soc., 1987,
109, 390.
27 K. Tatsumi, A. Nakamura, P. Hofmann, P. Stauffert and
R. Hoffmann, J. Am. Chem. Soc., 1985, 107, 4440.
28 A. Martin, M. Mena, C. Yelamos and R. Serrano, J. Organomet.
Chem., 1994, 467, 79.
29 B. Robinson, The Fisher Indole Synthesis, Wiley-Interscience, New
York, 1982.
30 H. Appler, J. Organomet. Chem., 1988, 350, 217.
31 I. M. M. Fussing, D. Pletcher and R. J. Whitby, J. Organomet.
Chem., 1994, 470, 109.
8 T. H. Warren, R. R. Schrock and W. M. Davis, Organometallics,
1996, 15, 562.
9 W. M. Vaughan, K. A. Abboud and J. M. Boncella, J. Am. Chem.
Soc., 1995, 117, 11015; D. D. VanderLende, K. A. Abboud and
J. M. Boncella, Organometallics, 1994, 13, 3378; D. D. VanderLende,
K. A. Abboud and J. M. Boncella, Polym. Prepr. (Am. Chem.
Soc., Div. Polym. Chem.), 1994, 35, 691; A. D. Horton, J. de With,
A. J. van der Linden and H. van de Weg, Organometallics, 1996, 15,
2672; D. M. Hoffman and S. Suh, J. Chem. Soc., Chem. Commun.,
1993, 714.
32 P. C. McArdle, J. Appl. Crystallogr., 1996, 239, 306.
33 Z. Otwinowski and W. Minor, Methods Enzymol., 1996, 276.
34 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman,
S. Garcia-Granda, R. O. Gould, J. M. M. Smits and C. Smykalla,
The DIRDIF 92 Program System, Technical Report, Crystallography
Laboratory, University of Nijmegen, 1992.
10 R. R. Schrock, Acc. Chem. Res., 1997, 30, 9.
11 J. G. Verkade, Acc. Chem. Res., 1993, 26, 483.
12 (a) D. D. Devore, F. J. Timmers, D. L. Hasha, R. K. Rosen,
T. J. Marks, P. A. Deck and C. L. Stern, Organometallics, 1995, 14,
3132; (b) K. E. du Plooy, U. Moll, S. Wocadlo, W. Massa and
J. Okuda, Organometallics, 1995, 14, 3129; (c) D. W. Carpenetti,
L. Kloppenburg, J. T. Kupec and J. L. Petersen, Organometallics,
1996, 15, 1572.
35 International Tables for Crystallography, Kluwer Academic
Publishers, Dordrecht, 1992, vol. C, Tables 4.2.6.8 and 6.1.1.4.
36 G. M. Sheldrick, SHELXS 97, A Program for Crystal Structure
Refinement, University of Göttingen, 1997.
37 C. K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge
National Laboratory, Oak Ridge, TN, 1976.
186
J. Chem. Soc., Dalton Trans., 2001, 181–186