Synthesis, structures, and olefin polymerization capability of vanadium(4+) imido compounds with fac-N3 donor ligands

Article abstract of DOI:10.1021/ic060454i

One-pot reactions of V(NMe₂)₄ with a range of primary alkyl- and arylamines RNH₂ and Me₃SiCl afforded the corresponding five-coordinate vanadium(4+) imido compounds V(NR)Cl ₂(NHMe₂)₂ [R = 2,6-C₆H ₃ⁱPr₂ (1a, previously reported), 2-C ₆H₄^tBu (1b), 2-C₆H ₄CF₃ (1c), ^tBu (1d), Ad (Ad = adamantyl, 1e)]. The crystal structures of 1b (two diamorphic forms) and 1c featured N-H...Cl hydrogen-bonded chains. Reaction of 1a-e with the neutral face-capping, N₃ donor ligands TACN (TACN = 1,4,7- trimethyltriazacyclononane) or TPM [TPM = tris(3,5-dimethylpyrazolyl)methane] gave the corresponding six-coordinate complexes V(NR)(TACN)Cl₂ (2a-e) and V(NR)(TPM)Cl₂ (3a-e). The X-ray structures of 2b, 2c, 2d, 3b, 3c, and 3e were determined. When activated with methylaluminoxane, certain of the complexes V(NR)(TPM)Cl₂ (3) formed moderately active ethylene polymerization catalysts, whereas none of the compounds V(NR)(TACN)Cl ₂ (2) were active.

Full text of DOI:10.1021/ic060454i

Inorg. Chem. 2006, 45, 6411−6423
Synthesis, Structures, and Olefin Polymerization Capability of
Vanadium(4 ) Imido Compounds with fac-N3 Donor Ligands
+
Helen R. Bigmore,† Martin A. Zuideveld,‡ Radoslaw M. Kowalczyk,§ Andrew R. Cowley,†
Mirko Kranenburg,| Eric J. L. McInnes,§ and Philip Mountford*,†
Chemistry Research Laboratory, UniVersity of Oxford, Mansfield Road, Oxford OX1 3TA, U.K.,
DSM Research, P.O. Box 18, 6160 MD Geleen, The Netherlands, EPSRC c. w. EPR SerVice
Centre, School of Chemistry, The UniVersity of Manchester, Oxford Road, Manchester M13 9PL,
U.K., and DSM Elastomers, Global R&D, P.O. Box 1130, 6160 BC Geleen, The Netherlands
Received March 16, 2006
One-pot reactions of V(NMe2)4 with a range of primary alkyl- and arylamines RNH2 and Me3SiCl afforded the
i
corresponding five-coordinate vanadium(4
reported), 2-C6H4 Bu (1b), 2-C6H4CF3 (1c), Bu (1d), Ad (Ad
+
) imido compounds V(NR)Cl2(NHMe2)2 [R
)
2,6-C6H3 Pr2 (1a, previously
t
t
)
adamantyl, 1e)]. The crystal structures of 1b (two
e with the neutral face-
1,4,7-trimethyltriazacyclononane) or TPM [TPM tris(3,5-
dimethylpyrazolyl)methane] gave the corresponding six-coordinate complexes V(NR)(TACN)Cl2 (2a e) and
V(NR)(TPM)Cl2 (3a e). The X-ray structures of 2b, 2c, 2d, 3b, 3c, and 3e were determined. When activated with
diamorphic forms) and 1c featured N−H‚‚‚Cl hydrogen-bonded chains. Reaction of 1a−
capping, N3 donor ligands TACN (TACN
)
)
−
−
methylaluminoxane, certain of the complexes V(NR)(TPM)Cl2 (3) formed moderately active ethylene polymerization
catalysts, whereas none of the compounds V(NR)(TACN)Cl2 (2) were active.
Introduction
families of the types Ti(NR)(TACN)Cl2 (II, where TACN
) 1,4,7-trimethyltriazacyclononane; Chart 1)10 and Ti(NR)-
(TPM)Cl2 [III, where TPM ) tris(3,5-dimethylpyrazolyl)-
methane].11 When activated with methylaluminoxane (MAO),
some of the compounds II and III were the most productive
imido-based ethylene homopolymerization precatalysts re-
ported to date (productivities of up to ca. 103 kg mol-1 h-1
bar-1 at ambient temperature and ca. 105 kg mol-1 h-1 bar-1
at 100 °C). Interestingly, the two different classes of catalysts
showed a quite different dependence of productivity on the
imido nitrogen substituent, especially at higher temperatures.
The TACN-supported systems showed the highest produc-
tivities when the N-R substituent was a bulky alkyl group
Among the many types of homogeneous non-cyclopen-
tadienyl Ziegler-Natta polymerization catalysts,1-7 imido
compounds (bearing the formally dianionic NR2- ligand)
have also been of interest.8 Starting from the versatile
synthons Ti(NR)Cl2(NHMe2)2 (I;9 Chart 1), we recently
prepared and evaluated two titanium(4+) imido catalyst
* To whom correspondence should be addressed. E-mail:
philip.mountford@chem.oxford.ac.uk (P.M.).
† University of Oxford.
‡ DSM Research.
§ The University of Manchester.
| DSM Elastomers.
(1) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int.
Ed. 1999, 38, 429.
t
[tBu, CMe2CH2 Bu, or adamantyl (Ad)], whereas the TPM-
supported systems were much less active for these substit-
uents and showed their highest productivities for bulky ortho-
(2) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. ReV. 2000, 100,
1169.
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S. R.; Sealey, A. J.; Cowley, A. R.; Skinner, M. E. G.; Mountford, P.
Inorg. Chem. 2005, 44, 2882.
t
substituted aryl groups (e.g., 2-C6H4 Bu, 2-C6H4CF3, and 2,6-
i
C6H3 Pr2). This has been attributed to the topological
(10) Adams, N.; Arts, H. J.; Bolton, P. D.; Cowell, D.; Dubberley, S. R.;
Friederichs, N.; Grant, C.; Kranenburg, M.; Sealey, A. J.; Wang, B.;
Wilson, P. J.; Cowley, A. R.; Mountford, P.; Schro¨der, M. Chem.
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Sealey, A. J.; Selby, J. D.; Zuideveld, M.; Cowley, A. R.; Mountford,
P. Chem. Commun. 2006, 436.
10.1021/ic060454i CCC: $33.50
Published on Web 07/08/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 16, 2006 6411

Bigmore et al.
Chart 1
differences between the macrocyclic (TACN) and podand-
like (TPM) fac-N3 donor ligands.11
In this paper, we describe synthetic, structural, and
polymerization studies of new vanadium(4+) imido synthons
of the type V(NR)Cl2(NHMe2)2 and their TACN and TPM
derivatives.
Given the excellent productivities of the titanium(4+)
systems II and III, we were interested in extending these
catalyst families to vanadium, a metal also of considerable
interest in the context of Ziegler-Natta polymerization
catalysis.4,12,13 Imidovanadium(5+) catalysts of the type
V(NR)(Ln)X2 (X ) halide, alkyl, or other monoanionic
ligand)8 have been known for over a decade with supporting
ligands or ligand sets Ln including tris(pyrazolyl)borate,14,15
cyclopentadienyl,16-18 aryloxide19-22 and ketimide.23 In con-
trast to these extensive studies of imidovanadium(5+)
systems, there has been only one very brief preliminary
communication of vanadium(4+) imido catalysts, this being
Results and Discussion
Synthesis and Solid-State Structures of New Imidobis-
(dimethylamine) Compounds V(NR)Cl2(NHMe2)2. The
titanium(4+) imido catalyst families Ti(NR)(TACN)Cl2 (II)10
and Ti(NR)(TPM)Cl2 (III)11 (R ) alkyl or aryl; Chart 1)
were readily prepared from the desired fac-N3 donor and the
new imidobis(dimethylamine) precursors Ti(NR)Cl2(NHMe2)2.9
An analogous approach was also successful for the synthesis
of a series of terminal titanium hydrazido(2-) complexes
Ti(NNPh2)(fac-N3)Cl2 from Ti(NNPh2)Cl2(NHMe2)2.32 We
anticipated that a similar strategy would be viable for
preparing the vanadium(4+) imido analogues V(NR)(fac-
N3)Cl2 (fac-N3 ) TACN or TPM).
i
for Lorber’s V(N-2,6-C6H3 Pr2)(X)2(NHMe2)2 (X ) NMe2
or Cl), which gave productivities of up to ca. 60 kg mol-1
h-1 bar-1 when activated with EtAlCl2 or MAO.24 Further-
more, vanadium(4+) Ziegler-Natta catalysts in general have
not yet been extensively studied,1,4,12,13,25-31 and there have
therefore been few direct comparisons of the polymerization
behavior of vanadium(4+) d1 catalyst systems with their
isostructural titanium(4+) d0 analogues.26,28,29
Lorber et al. have recently prepared potentially suitable
vanadium(4+) arylimido complexes V(NAr)Cl2(NHMe2)2
i
[Ar ) Ph, C6F5, 2,6-C6H3R2 (R ) Me, Pr (1a), Cl)],33 via
“one-pot” syntheses from V(NMe2)4, ArNH2, and Me3SiCl
in 73-96% yield. Pyridine, bipyridine, and tetramethyleth-
ylenediamine adducts of the V(NR)Cl2 moiety were obtained
from some of these complexes. However, bulky alkylimido
compounds (e.g., with tert-butyl or Ad) were not reported,
nor were arylimido compounds with larger ortho substituents
(namely, tert-butyl and CF3). Such substituents were the most
important in the titanium imido catalyst families II and III.
We therefore extended Lorber’s method to prepare the
homologous compounds V(NR)Cl2(NHMe2)2 [R ) 2-C6H4tBu
(1b), 2-C6H4CF3 (1c), tBu (1d), or Ad (1e)] as green or brown
air- and moisture-sensitive solids as summarized in eq 1.
The arylimido compounds were obtained in somewhat higher
yield (91 and 90%) than the alkylimido analogues (64 and
67%), which may reflect the differences in solubility.
(12) Hagen, H.; Boersma, J.; van Koten, G. Chem. Soc. ReV. 2002, 31,
357.
(13) Gambarotta, S. Coord. Chem. ReV. 2003, 237, 229.
(14) Scheuer, S.; Fischer, J.; Kress, J. Organometallics 1995, 14, 2627.
(15) Casagrande, A. C. A.; Tavares, T. T. d. R.; Kuhn, M. C. A.;
Casagrande, O. L.; dos Santos, J. H. Z.; Teranishi, T. J. Mol. Catal.
A 2004, 212, 267.
(16) Chan, M. C. W.; Chew, K. C.; Dalby, C. I.; Gibson, V. C.; Kohlmann,
A.; Little, I. R.; Reed, W. Chem. Commun. 1998, 1673.
(17) Coles, M. P.; Dalby, C. I.; Gibson, V. C.; Little, I. R.; Marshall, E.
L.; Ribeiro da Costa, M. H.; Mastroianni, S. J. Organomet. Chem.
1999, 591, 78.
(18) Sato, Y.; Nakayama, Y.; Yasuda, H. J. Appl. Polym. Sci. 2005, 97,
1008.
(19) Hagen, H.; Bezemer, C.; Boersma, J.; Kooijman, H.; Lutz, M.; Spek,
A. L.; van Koten, G. Inorg. Chem. 2000, 39, 3970.
(20) Nomura, K.; Sagara, A.; Imanishi, Y. Chem. Lett. 2001, 36.
(21) Nomura, K.; Sagara, A.; Imanishi, Y. Macromolecules 2002, 35, 1583.
(22) Wang, W.; Yamada, J.; Fujiki, M.; Nomura, K. Catal. Commun. 2003,
4, 159.
(23) Yamada, J.; Nomura, K. Organometallics 2005, 24, 3621.
(24) Lorber, C.; Donnadieu, B.; Choukroun, R. J. Chem. Soc., Dalton Trans.
2000, 4497.
(25) Motevalli, M.; Shah, D.; Shah, S. A. A.; Sullivan, A. C. Organome-
tallics 1994, 13, 4109.
(26) Choukroun, R.; Douziech, B.; Pan, C.; Dahan, F.; Cassoux, P.
Organometallics 1995, 14, 4471.
(27) Desmangles, N.; Gambarotta, S.; Bensimon, C.; Davis, S.; Zahalka,
H. J. Organomet. Chem. 1998, 562, 53.
(28) Witte, P. T.; Meetsma, A.; Hessen, B. Organometallics 1999, 18, 2944.
(29) Lorber, C.; Donnadieu, B.; Choukroun, R. Organometallics 2000, 19,
1963.
(30) Nakayama, Y.; Bando, H.; Sonobe, Y.; Suzuki, Y.; Fujita, T. Chem.
Lett. 2003, 32, 766.
(31) Lorber, C.; Wolff, F.; Choukroun, R.; Vendier, L. Eur. J. Inorg. Chem.
2005, 2850.
The new compounds 1b-e all feature ν(N-H) bands in
their IR spectra; these data are summarized in Table 1 along
6412 Inorganic Chemistry, Vol. 45, No. 16, 2006

Vanadium(4+) Imido Compounds with fac-N3 Donor Ligands
t
Table 1. Selected IR Data for the Compounds V(NR)Cl2(NHMe2)2
(1a-e)
and more electron-releasing nature of the 2-C6H4 Bu sub-
stituent compared to 2-C6H4CF3. The structurally character-
ized V(NR)Cl2(NHMe2)2 complexes described by Lorber (R
ν(N-H) (cm-1
)
i
b
compd (NR group)
Nujola
CH2Cl2
) 2,6-C6H3Me2 or 2,6-C6H3 Pr2) had analogous features (e.g.,
VdNim bond lengths of 1.654(3) and 1.656(4) Å),33 and in
general the distances and angles about the centers in 1b and
1c are consistent with previously reported ranges.34,35
i
1a (R ) 2,6-C6H3 Pr2)
3273c
3255
3263
3235
3233
3289
3289
3289
3293
3293
t
1b (R ) 2-C6H4 Bu)
1c (R ) 2-C6H4CF3)
1d (R ) tBu)
1e (R ) Ad)
Whereas Lorber’s imidobis(dimethylamine) compounds
showed no significant intramolecular interactions according
to X-ray crystallography, the supramolecular structures of
1b and 1c are dominated by N-H‚‚‚Cl hydrogen bonding
between the NHMe2 and Cl ligands of neighboring com-
plexes. Figures 2 and 3 illustrate the extended packing in
1b and 1c, respectively, with each molecule donating two
N-H‚‚‚Cl hydrogen bonds and accepting two and each
vanadium being a common member of two eight-membered
rings. Broadly analogous hydrogen-bonded structures were
found for Ti(NR)Cl2(NHMe2)2 (R ) iPr, Ph, 2,3,5,6-C6Cl4H),
while 1c is isomorphic with Ti(N-2-C6H4CF3)Cl2(NHMe2)2.9
a Nujol mull between NaCl plates. b CH2Cl2 solution, 0.1-mm-path-length
NaCl cell. c Additional band of slightly higher intensity at 3262 cm-1
.
with those for 1a. In a CH2Cl2 solution, the values are 3289
(arylimides) and 3293 cm-1 (alkylimides), but in the solid
state (Nujol mull). they span a wider range (3233-3273
cm-1). These observations can be interpreted as reflecting
the rather different N-H‚‚‚Cl hydrogen-bonded solid-state
structures formed, whereas in solution, the compounds are
discretely monomeric. The titanium imido compounds Ti-
(NR)Cl2(NHMe2)2 in general showed analogous features.9,32
The four new compounds 1b-e gave the expected electron
paramagnetic resonance (EPR) spectra as liquid or frozen
solutions (discussed below).
The supramolecular structure of 1c consists of infinite
N-H‚‚‚Cl hydrogen-bonded bilayers (pairs of vanadium
centers in the different chains are related by local noncrys-
tallographic inversion operations) running parallel to the
crystallographic b axis. The estimated N-H‚‚‚Cl distances
(average 2.72 Å; range 2.65-2.79 Å) may be categorized
as “intermediate” according to the notation of Brammer,
Orpen, and co-workers36 and are somewhat less than the sum
of the van der Waals radii for hydrogen and chlorine (2.95
Å37). The supramolecular structures of the diamorphs of 1b
differ from each other and also from that of Ti(N-2-C6H4tBu)-
Cl2(NHMe2)2. Both forms of 1b exist as infinite N-H‚‚‚Cl
hydrogen-bonded chains with the same average estimated
H‚‚‚Cl distances (average 2.62 Å and range 2.60-2.64 Å
for the two diamorphs). These are again “intermediate” in
length compared to N-H‚‚‚Cl hydrogen-bonded systems in
general.36 The chains for the monoclinic variant run parallel
to the crystallographic b axis, whereas in the orthorhombic
form, they run approximately parallel to the a axis. The two
forms of 1b differ most significantly in the relative orienta-
tions of the aryl nitrogen substituents along the chains, with
those of the monoclinic form oriented in the same direction
and those in the orthorhombic diamorph alternating “up” and
“down”. Interestingly, while both vanadium diamorphs form
infinite chains, molecules of the titanium analogue Ti(N-2-
The X-ray crystal structures of the two compounds V(NR)-
t
Cl2(NHMe2)2 [R ) 2-C6H4 Bu (1b) or 2-C6H4CF3 (1c)] have
been determined. Principal bond distances and angles are
compared in Table 2, and the views of the molecular
structures are collected in Figure 1. Details of the structure
determinations are given in the Experimental Section and
Table 7 and will not be further discussed. However, it should
be noted that for the purposes of discussion of the N-H‚‚‚Cl
bonding we refer in all instances to geometrically positioned
(N-H ) 0.87 Å; sp3-hybridized nitrogen) NHMe2 hydro-
gens.
Both compounds are monomeric and five-coordinate in
the solid state (ignoring for the moment any supramolecular
interactions). Crystals of 1b exist as two different diamorphs,
monoclinic and orthorhombic. The molecular structure of
the monoclinic form is shown in Figure 1, and a view of the
orthorhombic diamorph is given in the Supporting Informa-
tion (Figure S1). While the supramolecular structures differ
(see below), there are no significant differences between the
two diamorphs of 1b at the molecular level. Crystals of 1c
consist of two crystallographically independent molecules
in the unit cell (again no significant differences between
them), one being shown in Figure 1 and the other given in
the Supporting Information (Figure S2).
t
C6H4 Bu)Cl2(NHMe2)2 exist as discrete N-H‚‚‚Cl hydrogen-
bonded dimers in the solid state. A dimeric N-H‚‚‚Cl
hydrogen-bonded vanadium(4+) imido compound has been
reported previously.38
The geometries at vanadium are approximately trigonal-
bipyramidal (NHMe2 groups axial) with NimdVsCl angles
in the range 105.67(7)-112.39(6)° and NimdVsNam angles
in the range 97.91(8)-104.48(9)°. The VdNim bond lengths
are 1.657(4)-1.6628(17) Å, with VdNimsC angles in the
range 161.10(18)-174.9(3)°, indicating a formally linear
imido bond. The V-ligand distances in 1b appear in general
to be slightly longer than those for 1c, reflecting the bulkier
The solid-state IR spectra (powders as Nujol mulls, Table
1) feature ν(N-H) bands at 3263 cm-1 for 1c and 3255 cm-1
(34) Allen, F. H.; Kennard, O. Chem. Des. Autom. News 1993, 8, 1 and
31.
(35) Fletcher, D. A.; McMeeking, R. F.; Parkin, D. J. Chem. Inf. Comput.
Sci. 1996, 36, 746 (The United Kingdom Chemical Database Service).
(36) Aullo´n, G.; Bellamy, D.; Brammer, L.; Bruton, E. A.; Orpen, A. G.
Chem. Commun. 1998, 653.
(37) Bondi, A. J. Phys. Chem. 1964, 68, 441.
(38) Pugh, S. M.; Blake, A. J.; Gade, L. H.; Mountford, P. Inorg. Chem.
2001, 40, 3992.
(32) Parsons, T. B.; Hazari, N.; Cowley, A. R.; Green, J. C.; Mountford,
P. Inorg. Chem. 2005, 8442.
(33) Lorber, C.; Choukroun, R.; Donnadieu, B. Inorg. Chem. 2002, 41,
4217.
Inorganic Chemistry, Vol. 45, No. 16, 2006 6413

Bigmore et al.
t
Figure 1. Displacement ellipsoid plots (25% probability) of (a) V(N-2-C6H4 Bu)Cl2(NHMe2)2 (1b) as found in the monoclinic diamorph and (b) one of the
two crystallographically independent molecules of V(N-2-C6H4CF3)Cl2(NHMe2)2 (1c). Hydrogen atoms bound to carbon are omitted and N-H atoms are
drawn as spheres of the arbitrary radius. Views of 1b found in the orthorhombic diamorph and of the other crystallographically independent molecule of 1c
are provided in the Supporting Information.
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
which at first sight suggest two N-H environments. Similar
data were reported before for Ti(N-2-C6H4 Bu)Cl2(NHMe2)2,
t
V(N-2-C6H4 Bu)Cl2(NHMe2)2 (1b, Monoclinic and Orthorhombic
t
Diamorphs) and V(N-2-C6H4CF3)Cl2(NHMe2)2 (1c)a
the X-ray structure (vide supra) of which features one
N-H‚‚‚Cl hydrogen-bonded N-H group and one “free”
N-H per titanium center.9 However, the X-ray structure of
1a reported by Lorber appears to show no significant
N-H‚‚‚Cl contacts, and the IR data (Nujol) reported previ-
ously for 1a are identical within error to those in Table 1
recorded by us. One explanation could be that the sample
used for the X-ray structure was of a rather different solid-
state form than that obtained from the reaction mixture.
Synthesis and Characterization of the Precatalyst
Families V(NR)(fac-N3)Cl2 [fac-N3 ) TACN (2) or TPM
(3)]. The reaction between a benzene solution of 1a and
TACN heated to 80 °C resulted in the precipitation and
subsequent isolation of the target compound V(N-2,6-
C6H3iPr2)(TACN)Cl2 (2a) in 73% yield. This general protocol
was extended to afford the compounds V(NR)(TACN)Cl2
(2b-e) and V(NR)(TPM)Cl2 (3a-e) as red or green air- and
moisture-sensitive solids in 39-73% isolated yields (Scheme
1). Full details of the characterizing data are provided in the
Experimental Section, and detailed experimental procedures
are provided in the Supporting Information. Compounds 2
and 3 are the first vanadium imido complexes of TACN or
TPM. The isoelectronic oxo complex V(O)(TACN)Cl2 has
been reported previously.39 Vanadium TACN complexes in
general are well-known, whereas vanadium TPM complexes
are very rare.40 The vanadium(2+) sandwich cation [V{HC-
(pz)3}2]2+ has been described,41 and a series of VFe3S4
clusters [formally containing vanadium(3+)] capped with
tris(pyrazolyl)methanesulfonate ligands have also been pre-
pared, namely, [{O3SC(pz)3}VFe3S4X3]2- (X ) Cl, SEt, S-4-
1b
monclinic
orthorhombic
Lengths
1.6628(17) 1.657(4) [1.659(4)]
2.3253(6)
2.3299(6)
2.1567(17) 2.137(5) [2.167(5)]
2.1580(17) 2.148(4) [2.149(4)]
1.390(3)
2.63
1c
VdNim
V-Cl
1.6584(19)
2.3326(7)
2.3441(7)
2.153(2)
2.156(2)
1.404(3)
2.64
2.3193(14) [2.3190(15)]
2.3184(16) [2.3311(16)]
V-Nam
Nim-C
1.388(5) [1.381(5)]
2.67 [2.65]
2.79 [2.75]
NamH‚‚‚Cl
2.60
2.61
Angles
N
imdV-Nam 104.48(9)
97.91(8)
98.00(8)
109.51(6)
112.39(6)
138.09(2)
164.08(7)
163.65(15)
142
100.9(2) [101.0(2)]
98.25(17) [98.48(18)]
108.04(13) [108.57(13)]
110.53(13) [110.38(13)]
141.40(9) [141.04(10)]
160.8(2) [160.5(2)]
174.9(3) [174.1(3)]
141 [142]
98.07(9)
NimdV-Cl
105.67(7)
110.39(8)
143.90(3)
Cl-V-Cl
Nam-V-Nam 157.45(9)
VdNim-C
Nam-H‚‚‚Cl
161.10(18)
144
145
147
136 [138]
a Values in brackets for 1c correspond to the other crystallographically
independent molecule in the unit cell. Parameters involving N-H‚‚‚Cl
interactions are calculated assuming N-H ) 0.87 Å and an sp3-hybridized
N
am. “Nam” and “Nim” refer to the amino (NHMe2) and imido (VdNR)
nitrogens, respectively.
for 1b, consistent with the different average estimated
N-H‚‚‚Cl distances of 2.72 and 2.62 Å, respectively. As
mentioned, the titanium compound Ti(N-2-C6H4CF3)Cl2-
(NHMe2)2 is isomorphic with 1c. This had an average
estimated N-H‚‚‚Cl distance of 2.74 Å and showed a ν-
(N-H) (Nujol mull) IR band at 3264 cm-1. The solid-state
IR spectra of the alkylimido compounds V(NR)Cl2(NHMe2)2
[R ) tBu (1d) and Ad (1e)] showed ν(N-H) bands at 3235
and 3233 cm-1, suggesting that the N-H‚‚‚Cl interactions
are more developed in these systems compared to 1b and
1c. The solid-state IR spectrum of 1a (Table 1) featured two
partially resolved ν(N-H) bands at 3273 and 3262 cm-1,
(39) Fiedler, D.; Miljanic, O. S.; Welch, E. J. Acta Crystallogr., Sect. E
2002, 58, m347.
(40) Bigmore, H. R.; Lawrence, S. C.; Mountford, P.; Tredget, C. S. Dalton
Trans. 2005, 635 (Perspective Article review).
(41) Mani, F. Inorg. Chim. Acta 1980, 38, 97.
6414 Inorganic Chemistry, Vol. 45, No. 16, 2006

Vanadium(4+) Imido Compounds with fac-N3 Donor Ligands
t
Figure 2. Extended interaction diagrams for V(N-2-C6H4 Bu)Cl2(NHMe2)2 (1b) showing a portion of the infinite N-H‚‚‚Cl hydrogen-bonded chains.
Hydrogen atoms bound to carbon are omitted, and all atoms are drawn as spheres of the arbitrary radius. (a) Monoclinic form, symmetry operators: B, x,
1
1
1
1
y + 1, z; C, x, y - 1, z. (b) Orthorhombic form, symmetry operators: B, x + /2, y, -z + /2; C, x - 1, y, z; D x - /2, y, -z + /2.
Scheme 1. Synthesis of V(NR)(TACN)Cl2 (2a-e) and
V(NR)(TPM)Cl2 (3a-e)
Figure 3. Extended interaction diagram for V(N-2-C6H4CF3)Cl2(NHMe2)2
(1c) showing a portion of the infinite N-H‚‚‚Cl hydrogen-bonded bilayers.
Hydrogen atoms bound to carbon are omitted, and all atoms are drawn as
spheres of the arbitrary radius. Symmetry operators: A, x, y + 1, z; B, x,
y - 1, z.
C6H4Me, O-4-C6H4Me).42 Tris(pyrazolyl)borate-supported
vanadium(5+) imido compounds are somewhat better es-
tablished, as mentioned above, and three have been structur-
ally characterized.14,43
The X-ray crystal structures for the TACN compounds
t
(42) Fomitchev, D. V.; McLauchlan, C. C.; Holm, R. H. Inorg. Chem. 2002,
V(NR)(TACN)Cl2 [R ) 2-C6H4 Bu (2b), 2-C6H4CF3 (2c),
41, 958.
or tBu (2d)] have been determined. Selected bond distances
(43) Oshiki, T.; Mashima, K.; Kawamura, S.; Tani, K.; Kitaura, K. Bull.
Chem. Soc. Jpn. 2000, 73, 1735.
and angles are presented in Table 3, and views of the
Inorganic Chemistry, Vol. 45, No. 16, 2006 6415

Bigmore et al.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
V(NR)(TACN)Cl2 [R ) 2-C6H4 Bu (2b), 2-C6H4CF3 (2c), or Bu (2d)]
The X-ray crystal structures for the TPM compounds
t
t
i
t
V(NR)(TPM)Cl2 [R ) 2,6-C6H3 Pr2 (3a), 2-C6H4 Bu (3b),
2-C6H4CF3 (3c), or Ad (3e)] have also been determined.
Selected bond distances and angles are compared in Table
4, and views of the molecular structures are given in Figure
5. As for the TACN homologues, all four compounds exist
as monomeric, six-coordinate complexes in the solid state.
The tridentate TPM ligand is facially coordinating through
three of the six pyrazolyl ring nitrogens. The remainder of
the coordination sphere is again completed by the imido and
two chloride ligands. The VdNimsC bond angles fall in the
range 157.48(16)-172.8(3)° and so may also be considered
linear. A comparison of the VdNimsC bond angles for the
three arylimido groups (3a-c) shows that the more bulky
ortho groups in 3b and 3c have led to slightly more bent
VdNimsC linkages compared to that found in 3a [162.9(3)
and 157.48(16)° vs 172.8(3)°, respectively). This apparent
steric effect is highlighted further when considering the
adamantylimido ligand in 3e, which has an associated Vd
NimsC angle of 158.7(4)° [159.4(4)° for the second orienta-
tion of the disordered Ad group]. The imido nitrogen
substituent bends “down” away from the TPM ligand in 3c
and 3e, whereas for 3b, the aryl group bends “up” toward
the TPM, presumably reflecting the repulsion between the
o-tert-butyl group and the chloride ligands.
2b
Lengths
2.354(2)
2.204(2)
2.215(2)
1.704(2)
2.3845(7)
2.3872(2)
2c
2d
V(1)-N(1)
V(1)-N(2)
V(1)-N(3)
V(1)-N(4)
V(1)-Cl(1)
V(1)-Cl(2)
2.3379(17)
2.2063(17)
2.2011(16)
1.6925(17)
2.3766(6)
2.3801(6)
2.340(8)
2.209(8)
2.218(8)
1.657(2)
2.4030(7)
2.4011(7)
Angles
Cl(1)-V(1)-Cl(2)
Cl(1)-V(1)-N(1)
Cl(1)-V(1)-N(2)
Cl(1)-V(1)-N(3)
Cl(1)-V(1)-N(4)
Cl(2)-V(1)-N(1)
Cl(2)-V(1)-N(2)
Cl(2)-V(1)-N(3)
Cl(2)-V(1)-N(4)
N(1)-V(1)-N(2)
N(1)-V(1)-N(3)
N(1)-V(1)-N(4)
N(2)-V(1)-N(3)
N(2)-V(1)-N(4)
N(3)-V(1)-N(4)
V(1)-N(4)-C(10)
93.33(2)
86.72(6)
162.23(6)
90.64(6)
99.83(7)
84.82(5)
90.82(6)
161.19(6)
94.71(7)
76.45(8)
77.05(7)
173.45(8)
80.18(8)
97.04(9)
102.72(8)
158.92(17)
92.65(2)
86.21(4)
162.98(5)
93.91(5)
93.07(6)
89.43(5)
89.75(5)
164.46(5)
100.60(6)
76.97(6)
76.98(6)
169.97(7)
79.97(7)
103.05(7)
93.10(7)
159.21(15)
92.67(3)
89.76(15)
91.44(18)
165.35(16)
97.54(7)
88.33(15)
165.03(19)
92.81(16)
96.72(7)
77.3(2)
76.8(2)
170.89(16)
80.0(2)
96.99(19)
95.30(16)
170.20(18)
molecular structures are collected in Figure 4. All three
compounds exist as monomeric, six-coordinate complexes
in the solid state. In each case, the TACN ligand is
κ3-coordinated, with the remainder of the coordination sphere
occupied by the imido ligand and two cis-chloride ligands.
Minor disorder in the TACN rings of all three was
satisfactorily resolved. Compound 2d is isomorphic with Ti-
(NtBu)(TACN)Cl2 (both obtained as CH2Cl2 solvates).
As in the V(NR)(TACN)Cl2 complexes, there is significant
lengthening of the V-N bond trans to the imido ligand
[V(1)-N(1) ) 2.262(3)-2.328(3) Å compared with V(1)-
N(3) ) 2.1500(17)-2.170(3) Å and V(1)-N(5) ) 2.1513-
(17)-2.170(3) Å]. As was also found in the V(NR)(TACN)-
Cl2 systems, the alkylimido ligand leads to a shorter VdNim
bond length compared to the arylimides [1.663(3) Å (3e)
compared to 1.677(3)-1.686(3) Å]. In general, the V-NTACN
distances in the compounds 2 are longer than those in
comparable TPM-supported complexes 3 (for example, the
average V-NTACN distance in 2b is 2.258 Å, whereas that
in 3b is 2.200 Å). A similar feature was noted recently for
the titanium(4+) complexes Ti(NtBu)(TACN)Cl2 (average
Ti-NTACN ) 2.377 Å)10 and Ti(NtBu)(TPM)Cl2 (average
Ti-NTPM ) 2.291 Å)44 and also the compounds Sc(TACN)-
(CH2SiMe3)3 (average Sc-NTACN ) 2.463 Å) and Sc(TPM)-
(CH2SiMe3)3 (average Sc-NTPM ) 2.420 Å).45
The compound 3a is isomorphic with Kress’s tris-
(pyrazolyl)borate vanadium(5+) compound V(N-2,6-C6H3iPr2)-
(Tp*)Cl2 [Tp* ) HB(Me2pz)3].14 The V-Cl (average 2.298
Å) and V-NTp* (average 2.147 Å) distances in the Tp*
compound are shorter, as expected, than those in 3a (average
V-Cl ) 2.389 Å; average V-NTPM ) 2.217 Å) because
the former contains vanadium(5+) and the fac-N3 ligand
carries a formal negative charge. Surprisingly, however, the
VdNim distance in 3a of 1.677(3) Å is shorter than that in
the Tp* homologue [VdNim ) 1.693(4) Å]. Analogous
features were seen in the related compound V(N-2,6-C6H3-
A comparison of the V(1)-N(4) distances in the three
structures shows that the tert-butylimido ligand in 2d has
the shortest VdNim bond [1.657(2) Å compared with 1.704-
(2) and 1.6925(17) Å]. The longest V-Cl distances are also
found for 2d, highlighting the electron-releasing properties
of the alkylimido group in comparison to the arylimido
groups, as is generally observed. The VdNim bond lengths
lie within the previously reported range for vanadium(4+)
imido compounds (1.623-1.730 Å, average 1.679 Å, for 18
entries in the Cambridge Structural Database34,35). The Vd
NimsC bond angles fall in the range 158.92(17)-170.20-
(18)°, indicating formally linear imido linkages and that the
imido groups are acting as four-electron donors. The
comparatively low VdNimsCipso angles for 2b [158.92(17)°]
and 2c [159.21(15)°] are attributed to steric repulsions
between the bulky ortho substituents and the other ligands
present. The V-N bond lengths trans to the imido ligands
are significantly longer than the other two V-N bonds
[V(1)-N(1) ) 2.3379(17)-2.354(2) Å compared with
V(1)-N(2) ) 2.204(2)-2.209(8) Å and V(1)-N(3) )
2.215(2)-2.2011(16) Å] due to the strong trans influence
of imido ligands. This is consistent with the structures of
10
the titanium(4+) complexes Ti(NR)(TACN)Cl2 and with
that of the V-N bond length trans to the oxo ligand in V(O)-
(TACN)Cl2.39 A number of vanadium TACN complexes have
been structurally characterized previously (26 entries in the
Cambridge Structural Database34,35).
(44) Lawrence, S. C. D. Phil. Thesis, University of Oxford, Oxford, U.K.,
2003.
(45) Tredget, C. S.; Lawrence, S. C.; Ward, B. D.; Howe, R. G.; Cowley,
A. R.; Mountford, P. Organometallics 2005, 24, 3136.
6416 Inorganic Chemistry, Vol. 45, No. 16, 2006

Vanadium(4+) Imido Compounds with fac-N3 Donor Ligands
Figure 4. Displacement ellipsoid plots (25% probability) of (a) V(N-2-C6H4 Bu)(TACN)Cl2 (2b), (b) V(N-2-C6H4CF3)(TACN)Cl2 (2c), and (c) V(NtBu)-
t
(TACN)Cl2 (2d). Hydrogen atoms and CH2Cl2 of crystallization (for 2d) are omitted. The minor orientations of the disordered TACN ligands are also not
shown.
i
t
Table 4. Selected Bond Lengths (Å) and Angles (deg) for V(NR)(TPM)Cl2 [R ) 2,6-C6H3 Pr2 (3a), 2-C6H4 Bu (3b), 2-C6H4CF3 (3c), or Ad (3e,
Values for the Other Orientation of the NAd Group Given in the Supporting Information)]a
3a
3b
Lengths
3c
3e
V(1)-N(1)
V(1)-N(3)
V(1)-N(5)
V(1)-N(7)
V(1)-Cl(1)
V(1)-Cl(2)
2.328(3)
2.155(3)
2.169(3)
1.677(3)
2.3860(10)
2.3920(10)
2.272(3) [2.262(3)]
2.170(3) [2.166(3)]
2.170(3) [2.160(3)]
1.684(3) [1.686(3)]
2.3832(10) [2.3702(11)]
2.3893(10) [2.3932(11)]
2.3186(17)
2.1500(17)
2.1513(17)
1.6795(17)
2.3675(6)
2.3686(6)
2.302(2)
2.179(2)
2.175(2)
1.663(3)
2.4024(9)
2.4137(8)
Angles
Cl(1)-V(1)-Cl(2)
Cl(1)-V(1)-N(1)
Cl(1)-V(1)-N(3)
Cl(1)-V(1)-N(5)
Cl(1)-V(1)-N(7)
Cl(2)-V(1)-N(1)
Cl(2)-V(1)-N(3)
Cl(2)-V(1)-N(5)
Cl(2)-V(1)-N(7)
N(1)-V(1)-N(3)
N(1)-V(1)-N(5)
N(1)-V(1)-N(7)
N(3)-V(1)-N(5)
N(3)-V(1)-N(7)
N(5)-V(1)-N(7)
V(1)-N(7)-C(17)
93.48(4)
86.31(8)
164.48(8)
90.48(8)
99.33(11)
86.82(8)
94.74(4) [94.69(4)]
87.73(8) [86.64(8)]
166.72(9) [165.84(9)]
90.14(8) [89.82(9)]
99.65(11) [100.68(11)]
85.57(8) [85.86(8)]
89.01(8) [89.49(9)]
164.26(9) [165.07(9)]
101.12(11) [101.09(11)]
79.85(11) [80.16(11)]
79.67(11) [80.20(11)]
169.50(13) [169.36(13)]
83.07(11) [82.93(12)]
92.09(13) [91.76(13)]
92.77(13) [92.01(14)]
162.9(3) [162.9(3)]
92.50(2)
86.19(4)
165.18(5)
89.53(5)
93.96(6)
87.67(4)
91.46(5)
166.87(5)
96.16(6)
79.71(6)
79.52(6)
176.15(7)
83.48(6)
99.80(8)
96.64(7)
157.48(16)
96.16(3)
83.98(6)
163.08(7)
89.08(7)
94.45(11)
83.52(6)
89.49(7)
162.27(7)
95.02(10)
80.82(9)
80.19(9)
177.72(10)
81.08(9)
100.95(12)
101.47(12)
158.7(4)
86.19(8)
164.97(8)
100.71(11)
78.56(11)
78.96(11)
170.23(13)
83.27(11)
95.18(13)
92.94(13)
172.8(3)
a Values in brackets for 3b correspond to the other crystallographically independent molecule in the unit cell.
Me2)(Tp*)Cl2 [VdNim ) 1.687(3) Å; average V-Cl ) 2.296
Å; V-NTp* ) 2.153 Å].43 We speculate that the tighter
binding of the Tp* and chlorine ligands in the vanadium-
(5+) complexes leads to a destabilizing effect on the Vd
NAr moiety, but further work would be needed to confirm
this.
Inorganic Chemistry, Vol. 45, No. 16, 2006 6417

Bigmore et al.
i
t
Figure 5. Displacement ellipsoid plots (25% probability) of (a) V(N-2,6-C6H3 Pr2)(TPM)Cl2 (3a), (b) V(N-2-C6H4 Bu)(TPM)Cl2 (3b), (c) V(N-2-C6H4-
CF3)(TPM)Cl2 (3c), and (d) V(NAd)(TPM)Cl2 (3e, one orientation of the disordered Ad group shown). Hydrogen atoms and CH2Cl2 of crystallization (for
3b, 3c, and 3e) are omitted. A view of the other crystallographically independent molecule of 3b are provided in the Supporting Information.
It is interesting to compare the orientations of the imido
orientation may be chosen to best minimize the repulsions
between the o-CF3 substituent and the chloride ligands at
the shorter metal-ligand bond distances in 3c. The shortest
F‚‚‚H distance is 2.36 Å [associated angle F(2)‚‚‚H(93)-
C(9) ) 144 °; C-H bond orientations determined from a
Fourier difference map and hydrogen atoms placed with an
ideal C-H ) 1.08 Å]. This is less than the sum of the van
der Waals radii for fluorine and hydrogen (2.5-2.7 Å) but
lies at the long end of the range of F‚‚‚H distances considered
to be significant (F‚‚‚H hydrogen-bond interactions are in
general deemed to be very weak).47,48
N-aryl group in the compounds V(N-2-C6H4R)(TACN)Cl2
t
[R ) Bu (2b) or CF3 (2c)], V(N-2-C6H4R)(TPM)Cl2 [R )
tBu (3b) or CF3 (3c)], and the corresponding structurally
characterized titanium analogues Ti(N-2-C6H4R)(TPM)-
Cl2.11,46 In the TACN compounds 2b and 2c, the bulky ortho
substituent is oriented to one side of the VCl2 moiety,
whereas in 3b and also both Ti compounds Ti(N-2-C6H4R)-
(TPM)Cl2 (R ) tBu or CF3), the ortho groups are projected
down, i.e., directly away from the TPM ligand, and lie under
the VCl2 or TiCl2 moieties. This allows the C6 ring carbons
to lie within the cleft formed by the two Me2pz rings [those
containing N(3), N(4) and N(5), N(6) in Figure 5b]. The same
orientating effect is seen in 3a and 3c [and also V(N-2,6-
C6H3R2)(Tp*)Cl2 (R ) Me, iPr)14,43], with the aryl ring lying
in the plane that bisects the Cl-V-Cl angle.
EPR Studies. The EPR spectra of V(NR)Cl2(NHMe2)2
(1b-e), 2a-e, and 3a-e in a CH2Cl2/toluene (ca. 9:1, v/v)
solution were recorded at 295 and 120 K. Details of the
spectral features are summarized in Table 5. The EPR
parameters listed were extracted from spectral simulations.
All frozen solution spectra show hyperfine structure typical
Unusually, at least based on the structures of 3b and Ti-
(N-2-C6H4R)(TPM)Cl2 (R ) tBu or CF3) the o-CF3 substitu-
ent in 3c is not oriented away from the TPM ligand but
instead lies in the cleft between two Me2pz rings. This
7
of vanadium(4+) (51V, I ) /2, 100% natural abundance)
with anisotropy of the g matrices (g factor) and A matrices
(47) Howard, J. A. K.; Hoy, V. J.; O’Hagan, D.; Smith, G. T. Tetrahedron
1996, 52, 12613.
(48) Dunitz, J. D.; Taylor, R. Chem.sEur. J. 1997, 3, 89.
(46) Sealey, A. J. D. Phil. Thesis, University of Oxford, Oxford, U.K.,
2004.
6418 Inorganic Chemistry, Vol. 45, No. 16, 2006

Vanadium(4+) Imido Compounds with fac-N3 Donor Ligands
Table 5. EPR Data for V(NR)Cl2(NHMe2)2 (1), V(NR)(TACN)Cl2 (2),
and V(NR)(TPM)Cl2 (3) in a CH2Cl2/Toluene (ca. 9:1, v/v) Solution [R
arylimido systems. The effect is rather small, however, and
may be because the 3d orbital containing the unpaired
electron (in the local xy plane of 1-3, z axis defined as
above) lies orthogonal to the principal 3dπ-2pπ bonding
orbitals (involving 3dxz and 3dyz in the same coordinate
system). This is also consistent with the lack of hyperfine
coupling to the imido nitrogen.
i
t
t
) 2,6-C6H3 Pr2 (a), 2-C6H4 Bu (b), 2-C6H4CF3 (c), Bu (d), or Ad (e)]a
292 K solution
120 K frozen solution
gyy gzz giso Axx Ayy Azz
compd
giso
Aiso
gxx
1b
1c
1d
1e
2a
2b
2c
2d
2e
3a
3b
3c
3d
3e
1.973
1.971
1.973
1.975
1.972
1.969
1.972
1.973
1.975
1.973
1.973
1.974
1.972
1.973
94 1.986 1.985 1.948 1.973 56 58 168
93 1.986 1.985 1.947 1.973 55 56 167
101 1.988 1.986 1.945 1.973 58 59 172
97 1.988 1.987 1.945 1.973 58 59 172
95 1.986 1.979 1.947 1.971 60 58 167
93 1.990 1.977 1.946 1.971 59 56 166
94 1.983 1.976 1.952 1.970 61 61 167
97 1.989 1.983 1.946 1.973 61 59 171
97 1.990 1.983 1.945 1.973 62 59 171
96 1.987 1.979 1.944 1.970 62 62 169
98 1.987 1.981 1.945 1.971 63 63 170
95 1.987 1.979 1.949 1.972 61 62 168
100 1.989 1.981 1.940 1.970 64 65 174
100 1.990 1.984 1.942 1.972 64 65 174
Ethylene Polymerization Studies. Representative ex-
amples of the three vanadium(4+) imido familes V(NR)-
Cl2(NHMe2)2 (1), V(NR)(TACN)Cl2 (2), and V(NR)(TPM)-
Cl2 (3) were screened for ethylene polymerization using
MAO cocatalyst (Al:V ) 1500:1) initiated at 22-24 °C,
these being conditions identical with those used for room-
temperature screening of the corresponding TACN- and
TPM-supported titanium imido precatalysts Ti(NR)(fac-N3)-
Cl2.10,11 Disappointingly, none of the TACN catalysts as-
sessed (2a-d) showed any polymerization activity under
these conditions, whereas the titanium analogues gave
a Experimental errors ∆gii ) (0.001 and ∆Aii ) (2.
t
productivities of up to 760 kg mol-1 h-1 bar-1 (R ) Bu).
The polymerization results for catalysts of the types 1 and 3
are summarized in Table 6. Assessment of 3b with MAO
activation at 55 °C showed a productivity of 28 kg mol-1
h-1 bar-1 comparable to that obtained at the lower temper-
ature (30 kg mol-1 h-1 bar-1). None of the systems showed
any significant productivity when activated with Et2AlCl
(Al:V ) 1000:1).
The imidobis(dimethylamine) precatalysts 1a, 1b, and 1d
(entries 1-3, Table 6) gave modest productivities of 9-16
kg mol-1 h-1 bar-1, each forming high-Mw polyethylene (PE)
with fairly broad Mw/Mn values in the range of 4.5-6.0. The
ethylene uptake traces were all rather similar (Figure S7 of
the Supporting Information) and showed a very sluggish
uptake over the 30 min of the polymerization run. The
productivity of 16 kg mol-1 h-1 bar-1 for 1a is comparable
to the figure reported by Lorber (59 kg mol-1 h-1 bar-1 for
a 10-min run time). From the polymer yield and Mn, it can
be estimated that no more than ca. 15% of the vanadium
centers in catalysts 1 are productive and may be considerably
fewer.
i
Figure 6. EPR spectra (black lines) of V(N-2,6-C6H3 Pr2)(TACN)Cl2 (2a)
[top, frozen solution (120 K); bottom, solution at 295 K] and their
simulations (red lines). The solvent is a CH2Cl2/toluene (ca. 9:1, v/v)
mixture. Spectra were recorded at 9.450-GHz (X-band) frequency with a
microwave power of 2 mW and a modulation amplitude of 0.5 mT.
The TPM-supported catalysts V(NR)(TPM)Cl2 (3a-d)
also showed generally low productivities in the range 6-30
kg mol-1 h-1 bar-1 (entries 4-7, Table 6). However, unlike
the results for the imido-diamine systems 1, the TPM-
supported catalysts showed ethylene uptakes (Figure 7) and
PE molecular weight distributions (Figure 8), which varied
significantly with the imido R substituent. The observation
that the arylimides 3a-c had productivities some 3-5 times
that of 3d mirrors the situation for the MAO-activated
titanium imido systems Ti(NR)(TPM)Cl2 (R ) tBu, 230 kg
(hyperfine splitting). The 295 K spectra comprise eight
hyperfine lines characteristic of the interaction of the unpaired
(vanadium-centered) electron with the 51V nucleus. By way
of example, the frozen- and liquid-solution EPR spectra of
2a are shown in Figure 6.
The frozen-solution spectra are rhombic, consistent with
the molecular symmetries in each case and consistent with
retention of the solid-state structures in solution. The local
crystal fields are dominated by the imido ligands (defining
the local z axes). The g and A values are consistent with
vanadium(4+) imido compounds in general.33,38,49 The Aiso
and Azz values for the arylimido compounds (1-3, suffixes
a-c) are slightly but persistently smaller than those for the
alkylimides (suffixes d and e), suggesting a slightly greater
degree of covalency (or 3d electron delocalization) in the
t
i
mol-1 h-1 bar-1; R ) 2-C6H4 Bu, 2-C6H4CF3, or 2,6-C6H3 -
Pr2, 810-1170 kg mol-1 h-1 bar-1). However, while the
overall trend in the relative productivity as a function of the
imido nitrogen substituent is similar for the vanadium(4+)
and titanium(4+) systems, the latter are clearly much more
productive under very similar conditions.
The tert-butylimido catalyst system 3d/MAO showed little
or no ethylene uptake after the first ca. 5 min (on average,
only about 0.1 PE chains per precatalyst metal center was
(49) Lorber, C.; Choukroun, R.; Donnadieu, B. Inorg. Chem. 2003, 42,
673.
Inorganic Chemistry, Vol. 45, No. 16, 2006 6419

Bigmore et al.
Table 6. Ethylene Polymerization Data for Imido Vanadium Catalystsa
yield of
PE (g)
productivity
Mw
Mn
entry
precatalyst
(kg mol-1 h-1 bar-1
)
(g mol-1
)
(g mol-1
)
Mw/Mn
i
1
2
3
4
5
6
7
V(N-2,6-C6H3 Pr2)Cl2(NHMe2)2 (1a)
0.25
0.14
0.15
0.29
0.45
0.29
0.09
16
9
1 355 000
1 535 000
1 545 000
165 500
b
298 500
299 000
258 000
2 730
b
4.5
5.1
6.0
61
b
t
V(N-2-C6H4 Bu)Cl2(NHMe2)2 (1b)
V(NtBu)Cl2(NHMe2)2 (1d)
10
19
30
19
6
i
V(N-2,6-C6H3 Pr2)(TPM)Cl2 (3a)
t
V(N-2-C6H4 Bu)(TPM)Cl2 (3b)
V(N-2-C6H4CF3)(TPM)Cl2 (3c)
c
c
c
5.5
V(NtBu)(TPM)Cl2 (3d)
755 500
138 500
a Conditions: 6 bar C2H4, 5 µmol of precatalyst, MAO, Al:V ) 1500:1, 250 mL of toluene, 30 min, initiation temperature ) 22-24 °C; yields are the
average of two runs in each case. b Bimodal polymer. High-Mw fraction (18 wt %): Mn ) 240 500, Mw ) 1 270 000, Mw/Mn ) 5.3. Low-Mw fraction (82
wt %): Mn ) 670, Mw ) 840, Mw/Mn ) 1.3. c Bimodal polymer. High-Mw fraction (58 wt %): Mn ) 187 000, Mw ) 1 145 000, Mw/Mn ) 6.1. Low-Mw
fraction (42 wt %): Mn ) 745, Mw ) 1085, Mw/Mn ) 1.5.
sufficiently soluble in hot (100 °C) 1,2-C6D4Cl2 to allow
analysis by 1H NMR spectroscopy. End-group analysis and
integration found a Mn of ca. 800 [cf. 670 by gel permeation
chromatography (GPC; Table 6)] and that ca. 35% of the
chains were terminated by vinyl groups. Therefore, under
these conditions and polymerization run time, chain transfer
to monomer is significant but transfer to aluminum is
dominant.
The Mw and molecular weight distributions for PE
produced by the vanadium(4+) TPM-supported catalyst
systems differ significantly from those for the titanium(4+)
analogues Ti(NR)(TPM)Cl2.11 In particular, the titanium
i
Figure 7. Ethylene uptake by the V(NR)(TPM)Cl2 [R ) 2,6-C6H3 Pr2
t
t
t
(3a), 2-C6H4 Bu (3b), 2-C6H4CF3 (3c), Bu (3d)]/MAO catalyst systems.
analogues of 3b (R ) 2-C6H4 Bu) and 3c (R ) C6H4CF3)
gave PE with Mw ) 843 000 and 1 107 000 and Mw/Mn
values of 7.0 and 3.6, respectively, under comparable
conditions. Unfortunately, the PE formed by the titanium
analogue of 3b under the same polymerization conditions
was too insoluble for analysis by NMR spectroscopy, and
so an exact comparison with 3b/MAO cannot be made.46
The lower (or lack of) activity of vanadium-based Zie-
gler-Natta catalysts in general compared to their titanium
or other group 4 analogues is well-known and attributed in
general to deactivation via reduction pathways.12,13 Gibson
has explicitly demonstrated that cyclopentadienyl-supported
vanadium(5+) imido catalysts probably deactivate via reduc-
tive bimolecular pathways.16,50 The superior productivity of
the bulkier imido catalyst 3b may be connected with these
observations.
Figure 8. Molecular weight distributions determined by GPC for the PEs
i
t
produced by V(NR)(TPM)Cl2 [R ) 2,6-C6H3 Pr2 (3a), 2-C6H4 Bu (3b),
t
2-C6H4CF3 (3c), Bu (3d)].
The poor behavior of the vanadium(4+) catalysts V(NR)-
(fac-N3)Cl2 (2 and 3) in comparison with the corresponding
(and highly productive) isostructural titanium(4+) systems
is also consistent with previous reports. Choukroun et al.
found that [Cp2VMe]+ is unreactive toward ethylene po-
lymerization26 in contrast to the titanocenium analogues.51
It was also reported that a diamide-supported vanadium(4+)
catalyst (MAO activation) had a productivity that was only
ca. 10% of that of the titanium analogue.29 Hessen and co-
workers have shown that the MAO-activated vanadium(4+)
constrained geometry catalyst (CGC) V(η,5η1-C5H4CH2-
CH2NiPr)Cl2 had a productivity that was ca. 40% of the
corresponding titanium(4+) system; moreover, the PE formed
produced), whereas all three arylimides 3a-c maintained
some productivity over the full 30 min run time, with the
bulkier precatalyst 3b being superior (Figure 7). The PE
formed with 3a/MAO has a very broad molecular weight
distribution indeed (Figure 8), whereas that formed with 3b/
MAO is effectively bimodal. The PE formed with 3c/MAO
had features reminiscent of that from 3b/MAO but with a
more dominant high-Mw part. The PE produced with 3d/
MAO was of quite high Mw and had a broad molecular
weight distribution. The very low Mw fraction (ca. 80 wt %
of the total) of the PE formed with 3b has a narrow Mw/Mn
value of 1.3, while the high-Mw fraction has a broader Mw/
Mn of 5.3. The low-Mw part may be estimated to represent
110 chains per total metal present and the high-Mw part only
ca. 0.1 chains per metal center. The low-Mw fraction was
(50) Chan, M. C. W.; Cole, J. M.; Gibson, V. C.; Howard, J. K. Chem.
Commun. 1997, 2345.
(51) Bochmann, M. J. Chem. Soc., Dalton Trans. 1996, 255.
6420 Inorganic Chemistry, Vol. 45, No. 16, 2006

Vanadium(4+) Imido Compounds with fac-N3 Donor Ligands
V(NR)Cl2(NHMe2)2 (1b-e). (a) General Procedure. To a
toluene solution (15 mL) of V(NMe2)4 (ca. 1-5 mmol) and RNH2
(1 equiv) at room temperature was slowly added Me3SiCl (8 equiv).
The resulting solution was heated at 100 °C for 16 h. Volatiles
were removed and the resulting solids washed with pentane (2 ×
10 mL) and dried in vacuo. The target compounds were obtained
as analytically pure air- and moisture-sensitive green or brown
solids. Full details are provided in the Supporting Information.
with the vanadium catalyst had a Mw that was significantly
lower [Mn ) 4900 for vanadium(4+) vs 59 500 for titanium-
(4+)].28
Conclusions
We have found that bulky alkyl- and arylimido-diamine
complexes V(NR)Cl2(NHMe2)2 (1) may be accessed via the
straightforward route first described by Lorber only for less
sterically demanding aryl substituents. However, unlike the
previous arylimido homologues,33 1b and 1c show extensive
N-H‚‚‚Cl hydrogen bonding in the solid state. The first
TACN- and TPM-supported imido vanadium compounds
were readily prepared from 1, and a number of their X-ray
structures have been determined. The EPR spectra for 1-3
were rather similar but nonetheless did show a small
dependence of the g values and hyperfine couplings A on
the nature of the imido nitrogen substituent. The TACN-
supported compounds 2 were inactive as ethylene polym-
erization precatalysts, and the TPM-supported homologues
3 were only moderately active, generally giving PEs with
broad molecular weight distributions. The most active
catalyst 3b produced predominately very low Mw PE. These
differences in comparison with the highly active TACN- and
TPM-supported titanium(4+) analogues are consistent with
previous literature reports for vanadocene, CGC, and dia-
mide-based vanadium(4+) catalyst systems. The low (or lack
of) activity of the catalysts in general is consistent with
previous reports for vanadium-based Ziegler-Natta systems.
t
(b) Data for 1b (R ) 2-C6H4 Bu). Yield: 91%. IR (NaCl plates,
Nujol, cm-1): 3583(w), 3255(s), 1584(w), 1401(m), 1293(m), 1092-
(m), 1047(m), 1014(s), 899(m), 800(m), 761(s), 722(w), 665(w).
IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3289. Anal. Found (calcd
for C14H27Cl2N3V): C, 46.7 (46.8); N, 11.6 (11.7); H, 7.4 (7.6).
t
EI-MS: m/z 147 (95%; [N-2-C6H4 Bu]+), 69 (93%; [tBu]+). FI-
MS: m/z 358 (5%; [M]+), 313 (22%; [M - NHMe2]+). FI-HRMS
t
for V(N-2-C6H4 Bu)Cl2(NHMe2)2. Found (calcd for C14H27-
Cl2N3V): 358.1010 (358.1022).
(c) Data for 1c (R ) 2-C6H4CF3). Yield: 90%. IR (NaCl plates,
Nujol, cm-1): 3263(s), 1591(m), 1563(m), 1338(s), 1312(s), 1255-
(m), 1153(m), 1134(s), 1107(s), 1057(s), 1030(s), 897(m), 800-
(m), 759(s). IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3289. Anal.
Found (calcd for C11H18Cl2F3N3V): C, 35.5 (35.6); N, 11.4 (11.3);
H, 5.0 (4.9). FI-MS: m/z 370 (15%; [M]+), 324 (100%; [M -
NHMe2 - H]+).
(d) Data for 1d (R ) tBu). Yield: 64%. IR (NaCl plates, Nujol,
cm-1): 3235(s), 1613(w), 1401(w), 1358(m), 1238(s), 1212(m),
1122(m), 1091(m), 1029(s), 903(m), 801(m), 722(w), 665(w). IR
(NaCl cell, CH2Cl2, ν(N-H), cm-1): 3293. Anal. Found (calcd
for C8H23Cl2N3V): C, 33.9 (33.9); N, 14.8 (14.8); H, 8.1 (8.2).
FI-MS: m/z 282 (7%; [M]+), 248 (7%; [M - 2Cl]+), 236 (45%;
[M - C3H9 - H]+). FI-HRMS for V(NtBu)Cl2(NHMe2)2. Found
(calcd for C8H23Cl2N3V): 282.0718 (282.0709).
(e) Data for 1e (R ) Ad). Yield: 67%. IR (NaCl plates, Nujol,
cm-1): 3293(w), 3233(s), 1599(w), 1302(m), 1224(m), 1115(w),
1099(m), 1026(m), 987(m), 896(m), 843(w), 811(w), 722(w), 665-
(w). IR (NaCl cell, CH2Cl2, ν(N-H), cm-1): 3293. Anal. Found
(calcd for C14H29Cl2N3V): C, 46.7 (46.6); N, 11.7 (11.6); H, 8.0
(8.1). FI-MS: m/z 360 (3%; [M]+), 314 (15%; [M - NHMe2 -
H]+).
Experimental Section
General Methods and Instrumentation. All air- and moisture-
sensitive operations were carried out using standard Schlenk-line
(Ar) and drybox (N2) techniques. Protio and deutero solvents were
purified, dried, and distilled using conventional techniques. IR
spectra were recorded on a Perkin-Elmer Paragon 1000 FT-IR
spectrometer as Nujol mulls between NaCl windows and, in some
instances, as CH2Cl2 solutions using a 0.1-mm-path-length NaCl
cell. All data are quoted in wavenumbers (cm-1). Mass spectra were
recorded on a Micromass GCT TOF Instrument using a solid probe
inlet temperature program. All data are quoted in a mass/charge
ratio (m/z). The X-band (9.450-GHz) EPR spectra were recorded
at 120 and 295 K using a commercial Bruker EMX spectrometer.
The EPR spectra have been analyzed using commercial Bruker
programs WINEPR and XSophie. Polymer characterization was
carried out by Rapra Technology. Elemental analyses were carried
out by the analytical laboratory of the Inorganic Chemistry
Laboratory, University of Oxford, or by the Elemental Analysis
Service, London Metropolitan University.
V(NR)(TACN)Cl2 (2a-e). (a) General Procedure. To a
benzene solution (30 mL) of V(NR)Cl2(NHMe2)2 (ca. 0.5-2 mmol)
was added TACN (1 equiv). The reaction mixture was heated at
80 °C for 3 h then left stirring at room temperature for 16 h. The
reaction mixture was filtered and the precipitate washed with
benzene (2 × 10 mL) then dried in vacuo. The target compounds
were obtained as analytically pure air- and moisture-sensitive green
or red solids. Full details are provided in the Supporting Information.
i
(b) Data for 2a (R ) 2,6-C6H3 Pr2). Yield: 73%. IR (NaCl
plates, Nujol, cm-1): 1420(w), 1307(w), 1157(w), 1067(m), 1006-
(m), 959(w), 890(w), 801(m), 788(m), 759(w). Anal. Found (calcd
for C21H38Cl2N4V): C, 53.8 (53.8); N, 11.9 (12.0); H, 8.2 (8.2).
EI-MS: m/z 467 (7%; [M]+), 292 (3%; [M - (N-2,6-C6H3 Pr2)]+).
i
Starting Materials. The compounds V(NMe2)4,52 V(N-2,6-
t
i
C6H3 Pr2)Cl2(NHMe2)2,33 TACN,53 and TPM54 were prepared
(c) Data for 2b (R ) 2-C6H4 Bu). Yield: 44%. IR (NaCl plates,
Nujol, cm-1): 1491(w), 1426(m), 1293(w), 1228(w), 1159(w),
1091(m), 1066(m), 1009(s), 951(w), 896(w), 788(m), 771(s). Anal.
Found (calcd for C19H34Cl2N4V): C, 51.7 (51.8); N, 12.7 (12.7);
H, 7.9 (7.8). EI-MS: m/z 439 (10%; [M]+), 292 (4%; [M - (N-
according to the literature methods. Liquid primary amines and Me3-
SiCl were predried over freshly ground CaH2 and distilled prior to
use. All other compounds and reagents were purchased from
commercial chemical suppliers and used without further purification.
t
t
2-C6H4 Bu)]+). EI-HRMS for V(N-2-C6H4 Bu)Cl2(TACN). Found
(calcd for C19H34Cl2N4V): 439.1582 (439.1600).
(52) Bradley, D. C.; Gitlitz, M. H. J. Chem. Soc. (A) 1969, 980.
(53) Madison, S. A.; Batal, D. J. (Unilever PLC, U.K.; Unilever NV). U.S.
Patent 5,284,944, 1994, p 21 ff.
(54) Reger, D. L.; Grattan, T. C.; Brown, K. J.; Little, C. A.; Lamba, J. J.
S.; Rheingold, A. L.; Sommer, R. D. J. Organomet. Chem. 2000, 607,
120.
(d) Data for 2c (R ) 2-C6H4CF3). Yield: 70%. IR (NaCl plates,
Nujol, cm-1): 1590(w), 1555(w), 1324(s), 1300(w), 1159(m), 1119-
(s), 1061(s), 1029(m), 1006(m), 959(w), 895(w), 789(m), 765(w),
682(m). Anal. Found (calcd for C16H25Cl2F3N4V): C, 42.4 (42.5);
Inorganic Chemistry, Vol. 45, No. 16, 2006 6421

Bigmore et al.
t
Table 7. X-ray Data Collection and Processing Parameters for V(N-2-C6H4R)Cl2(NHMe2)2 [R ) Bu (1b, Monoclinic and Orthorhombic Diamorphs)
t
i
or CF3 (1c)], V(N-2-C6H4R)(TACN)Cl2 [R ) Bu (2b) or CF3 (2c)], V(NtBu)(TACN)Cl2‚CH2Cl2 (2d‚CH2Cl2), V(N-2,6-C6H3 Pr2)(TPM)Cl2 (3a),
t
V(N-2-C6H4 Bu)(TPM)Cl2‚2.59CH2Cl2 (3b‚2.59CH2Cl2), and V(N-2-C6H4CF3)(TPM)Cl2 (3c‚CH2Cl2)
1b
monclinic
orthorhombic
C14H27Cl2N3V
1c
2b
2c
empirical
formula
fw
temp (K)
wavelength (Å)
space group
a (Å)
C14H27Cl2N3V
C11H18Cl2F3N3V
C19H34Cl2N4V
C16H25Cl2F3N4V
359.23
150
359.23
150
0.710 73
Pbca
12.8825(2)
15.5435(3)
19.5799(3)
90
371.12
150
0.710 73
Pna21
16.0311(2)
6.4901(2)
32.2426(4)
90
440.35
150
452.24
150
0.710 73
P21/n
7.4288(2)
16.5641(4)
15.6021(3)
90
91.9069(10)
90
0.710 73
C2/c
29.9098(8)
6.4650(2)
19.8323(6)
90
101.2391(11)
90
3761.37(19)
8
0.710 73
P21/n
9.2784(3)
14.4815(5)
15.9747(7)
90
98.0961(13)
90
2125.05(14)
4
b (Å)
c (Å)
R (deg)
â (deg)
90
90
90
90
γ (deg)
V (Å3)
3920.66(11)
8
1.217
3354.63(12)
8
1.470
1918.80(8)
4
1.565
Z
d(calcd) (Mg m-3
)
1.269
0.807
1.376
0.729
abs coeff (mm-1
)
0.774
0.932
0.831
R indices: R1, Rw
0.0320, 0.0350
0.0308, 0.0381
0.0347, 0.0351
0.0331, 0.0344
0.0339, 0.0417
[I > 3σ(I)]a
2d‚CH2Cl2
3a
3b‚2.59CH2Cl2
3c‚CH2Cl2
empirical
formula
fw
temp (K)
wavelength (Å)
space group
a (Å)
C13H32Cl2N4V‚CH2Cl2
C28H39Cl2N7V‚2.59CH2Cl2
C26H35Cl2N7V‚CH2Cl2
C23H26Cl2F3N7V
449.19
150
0.710 73
Pbca
15.1314(2)
14.3736(2)
19.9057(3)
90
595.51
150
0.710 73
Cc
17.7339(4)
9.4865(3)
19.4753(5)
90
116.7186(11)
90
787.10
150
0.710 73
P1h
10.2032(2)
18.9895(2)
20.5245(3)
79.5401(6)
86.8265(6)
74.5594(6)
3796.36(10)
4
664.28
150
0.710 73
Pbca
16.2732(2)
16.0207(2)
22.7571(2)
90
b (Å)
c (Å)
R (deg)
â (deg)
90
90
90
90
γ (deg)
V (Å3)
4329.34(11)
8
1.378
2926.55(14)
4
1.352
5932.96(12)
8
1.487
Z
d(calcd) (Mg m-3
)
1.387
0.802
abs coeff (mm-1
)
0.956
0.552
0.741
R indices: R1, Rw
0.0407, 0.0480
0.0387, 0.0412
0.0646, 0.0801
0.0343, 0.0391
[I > 3σ(I)]a
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) x{∑w(|Fo| - |Fc|)2/∑w|Fo| .
i
N, 12.4 (12.4); H, 5.4 (5.6). EI-MS: m/z 451 (100%; [M]+), 292
(5%; [M - (N-2-C6H4CF3)]+).
(e) Data for 2d (R ) tBu). Yield: 61%. IR (NaCl plates, Nujol,
cm-1): 1499(m), 1355(m), 1297(m), 1241(m), 1207(w), 1157(w),
1073(m), 1009(s), 895(w), 789(m), 749(w), 687(m). Anal. Found
(calcd for C13H30Cl2N4V): C, 42.8 (42.9); N, 15.3 (15.4); H, 8.2
(8.3). EI-MS: m/z 363 (83%; [M]+), 292 (100%; [M - NtBu]+).
(b) Data for 3a (R ) 2,6-C6H3 Pr2). Yield: 43%. IR (NaCl
plates, Nujol, cm-1): 1567(m), 1412(m), 1306(m), 1270(m), 1112-
(w), 1050(m), 977(w), 863(m), 801(m), 761(m), 707(m). Anal.
Found (calcd for C28H39Cl2N7V): C, 56.5 (56.5); N, 16.4 (16.5);
H, 6.8 (6.6). EI-MS: m/z 594 (7%; [M]+), 175 (16%; [N-2,6-
i
i
C6H3 Pr2]+). EI-HRMS for V(N-2,6-C6H3 Pr2)Cl2(TPM). Found
(calcd for C28H39Cl2N7V): 594.2059 (594.2084).
t
(f) Data for 2e (R ) Ad). Yield: 42%. IR (NaCl plates, Nujol,
cm-1): 1599(w), 1498(w), 1302(m), 1227(m), 1157(w), 1097(m),
1073(m), 1010(m), 991(w), 894(w), 789(m), 749(w), 685(m). Anal.
Found (calcd for C19H36Cl2N4V): C, 51.5 (51.6); N, 12.7 (12.7);
H, 8.2 (8.2). EI-MS: m/z 441 (100%; [M]+), 292 (24%; [M - (N-
Ad)]+). EI-HRMS for V(NAd)Cl2(TACN). Found (calcd for C19H36-
Cl2N4V): 441.1745 (441.1757).
(c) Data for 3b (R ) 2-C6H4 Bu). Yield: 50%. IR (NaCl plates,
Nujol, cm-1): 1567(s), 1417(m), 1307(s), 1269(s), 1165(w), 1090-
(m), 1046(m), 917(w), 867(m), 820(m), 748(m), 710(m). Anal.
Found (calcd for C26H35Cl2N7V): C, 55.0 (55.0); N, 17.3 (17.3);
H, 6.2 (6.2). EI-MS: m/z 566 (3%; [M]+), 147 (43%; [N-2-
C6H4 Bu]+). EI-HRMS for V(N-2-C6H4 Bu)Cl2(TPM). Found (calcd
for C26H35Cl2N7V): 566.1792 (566.1771).
t
t
V(NR)(TPM)Cl2 (3a-e). (a) General Synthetic Procedure. To
a benzene solution (20 mL) of V(NR)Cl2(NHMe2)2 (ca. 0.5-2
mmol) was added a solution of HC(Me2pz)3 (1 equiv) in benzene
(10 mL). The reaction mixture was heated at 80 °C for 6 h, allowed
to cool, and filtered, and the precipitate was washed with benzene
(2 × 10 mL). The product was dried in vacuo. The target
compounds were obtained as analytically pure air- and moisture-
sensitive green or red solids. Full details are provided in the
Supporting Information.
(d) Data for 3c (R ) 2-C6H4CF3). Yield: 39%. IR (NaCl plates,
Nujol, cm-1): 1731(w), 1567(m), 1413(m), 1336(m), 1309(m),
1165(m), 1101(s),1027(s), 912(w), 860(m), 799(s), 768(m), 701-
(w), 665(w). Anal. Found (calcd for C23H26Cl2F3N7V): C, 47.7
(47.7); N, 16.9 (16.9); H, 4.5 (4.5). EI-MS: m/z 579 (5%; [M -
H]+).
(e) Data for 3d (R ) tBu). Yield: 55%. IR (NaCl plates, Nujol,
cm-1): 1565(s), 1417(m), 1304(s), 1234(m), 1209(w), 1106(m),
6422 Inorganic Chemistry, Vol. 45, No. 16, 2006

Vanadium(4+) Imido Compounds with fac-N3 Donor Ligands
1045(s), 913(m), 861(m), 804(m), 703(m), 681(m), 665(w). Anal.
Found (calcd for C20H31Cl2N7V): C, 49.0 (48.9); N, 19.8 (19.9);
H, 6.2 (6.4).
(f) Data for 3e (R ) Ad). Yield: 46%. IR (NaCl plates, Nujol,
cm-1): 3090(w), 1567(s), 1417(s), 1393(s), 1311(s), 1304(s), 1273-
(s), 1203(w), 1099(m), 1045(s), 987(w), 913(m), 869(m), 861(m),
827(m), 712(m), 677(s). Anal. Found (calcd for C26H37Cl2N7V):
C, 54.9 (54.8); N, 17.3 (17.2); H, 6.6 (6.6). EI-MS: m/z 384 (5%;
[M - Cl - N-C10H15]+), 298 (7%; [HC(Me2pz)3]+).
Polymerization Procedures. To a glass Bu¨chi 1-L autoclave
was added MAO (5 mL, 10% in toluene (w/w), 7.5 mmol) made
up to 200 mL with toluene. The solution was stirred at 1000 rpm
for 5 min. The precatalyst (5 µmol) was dissolved in toluene (50
mL), added to the reactor, and activated by stirring with the MAO
solution for 30 min at 1000 rpm. The reaction vessel was placed
under full vacuum for 10 s, the stirring was increased to 1500 rpm,
and the reactor was placed under a dynamic pressure of 6 bar of
ethylene. After 30 min, the autoclave was isolated and the pressure
was released. A total of 5 mL of methanol was added, followed by
50 mL of water (with stirring). The mixture was acidified to pH 1
using a solution of 10% HCl in methanol and stirred for 1 h. The
precipitated polymers were filtered, washed with water (1000 mL),
and dried to constant weight at room temperature.
highly anisotropic, which was taken as evidence of disorder. In
each case, a second conformation of the ring was identified using
difference Fourier maps. Coordinates, anisotropic thermal param-
eters, and site occupancies were refined for the disordered carbon
atoms. Similarity restraints were applied to the lengths of chemically
similar bonds [standard uncertainty (su) 0.02 Å] and to chemically
similar angles (su 2°), assuming the ring to have regular threefold
rotational symmetry. Similarity restraints were also applied to the
thermal parameters of directly bonded pairs of atoms. The site
occupancy factor for the major and minor orientations were as
follows: 0.659 and 0.341 (2b); 0.780 and 0.220 (2c); 0.695 and
0.305 (2d). For 3b, the coordinates, isotropic displacement param-
eters, and site occupancies of the carbon and chlorine atoms of the
disordered solvent molecules were refined subject to restraint of
the C-Cl bond lengths to 1.77(2) Å and of the Cl-C-Cl angles
to 112(2)°. Similarity restraints were applied to the displacement
parameters of directly bonded pairs of atoms. The high values of
the minimum and maximum residual electron densities suggest that
the model does not fully agree with the diffraction data. Because
the minima and maxima lie close to the chlorine atoms of the
disordered solvent, the disagreement is presumed to be due to an
oversimplified model of the disorder and to be of no chemical
significance. For 3e, it was clearly apparent that the Ad group was
disordered, and this was modeled as being due to disorder over
two positions related by the local mirror plane of the {V(TPM)-
Cl2} moiety. Coordinates, anisotropic thermal parameters, and site
occupancies were refined for the disordered carbon atoms, subject
to restraint of chemically equivalent bond lengths and angles to
their common means (su’s 0.02 Å and 2°, respectively). A difference
Fourier map showed the presence of a further molecule of solvent,
which was disordered over two orientations. The coordinates,
anisotropic displacement parameters, and site occupancies of its
carbon and chlorine atoms were refined subject to restraint of the
C-Cl bond lengths to 1.77(2) Å and the Cl-C-Cl angles to 112-
(2)°.
Crystal Structure Determinations of V(N-2-C6H4R)Cl2-
t
(NHMe2)2 [R ) Bu (1b, Monoclinic and Orthorhombic Di-
amorphs) or CF3 (1c)], V(N-2-C6H4R)(TACN)Cl2 [R ) tBu (2b)
or CF3 (2c)], V(NtBu)(TACN)Cl2‚CH2Cl2 (2d‚CH2Cl2), V(N-2,6-
i
t
C6H3 Pr2)(TPM)Cl2 (3a), V(N-2-C6H4 Bu)(TPM)Cl2‚2.59CH2Cl2
(3b‚2.59CH2Cl2), V(N-2-C6H4CF3)(TPM)Cl2‚CH2Cl2 (3c‚CH2Cl2),
and V(NAd)(TPM)Cl2‚2CH2Cl2 (3e‚2CH2Cl2). Crystal data col-
lection and processing parameters are given in Table 7. Crystals
were mounted on glass fibers using perfluoropolyether oil and
cooled rapidly in a stream of cold N2 using an Oxford Cryosystems
CRYOSTREAM unit. Diffraction data were measured using an
Enraf-Nonius Kappa CCD diffractometer. Intensity data were
processed using the DENZO-SMN package.55 The structures were
solved using the direct methods program SIR92,5656 which located
all non-hydrogen atoms. Subsequent full-matrix least-squares
refinement was carried out using the CRYSTALS program suite.57
Coordinates and anisotropic thermal parameters of all non-hydrogen
atoms were refined (see additional comments below). Hydrogen
atoms bonded to carbon were placed geometrically, while the N-H
atoms were located from Fourier difference maps and refined
isotropically. However, for the purposes of geometric comparisons
with literature compounds such as Ti(NR)Cl2(NHMe2)2, geometric
N-H placement using a distance of 0.87 Å was used (see Table
1). Weighting schemes and other corrections were applied as
appropriate. For 2b-d, the displacement parameters of the carbon
atoms of the triazacyclononane ring were abnormally large and
A full listing of atomic coordinates, bond lengths and angles,
and displacement parameters for all of the structures has been
deposited at the Cambridge Crystallographic Data Center (12 Union
Road, Cambridge CB2 1EZ, U.K., tel +44 1223 336408, fax +44
1223 336033).
Acknowledgment. We thank EPSRC and DSM Research
for support.
Supporting Information Available: X-ray crystallographic data
in CIF format for the structure determinations of 1b (two diamor-
phs), 1c, 2b, 2c, 2d‚CH2Cl2, 3a, 3b‚2.59CH2Cl2, 3c‚CH2Cl2, and
3e‚2CH2Cl2, full synthetic procedures for compounds 1b-e, 2a-
e, and 3a-e, further cell packing diagrams for 1b and 1c, plots of
the orthorhombic form of 1b and the other crystallographically
independent molecules of 1c and 3b, and ethylene uptake traces.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(55) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode; Academic press: New York, 1997.
(56) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435.
(57) Betteridge, P. W.; Cooper, J. R.; Cooper, R. I.; Prout, K.; Watkin, D.
J. J. Appl. Crystallogr. 2003, 36, 1487.
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