Neutral and cationic vanadium (III) Alkyl and allyl complexes with a cyclopentadienyl-amine ancillary ligand

Article abstract of DOI:10.1021/om049660t

The (N,N-dimethylaminoethyl)cyclopentadienyl vanadium(III) complex [η⁵,η¹-C₅H₄(CH ₂)₂-NMe₂]VCl₂(PMe₃) (1), in which the pendant amine is coordinated to the metal center, was prepared by the reaction of VCl₃(PMe₃)₂ with Li[C ₅H₄(CH₂)₂NMe₂] in THF. Reaction of 1 with 2 equiv of MeLi yields [η⁵-C₅H ₄(CH₂)₂NMe₂]VMe₂(PMe ₃)₂ (2), in which the amine is released in favor of the binding of a second phosphine. Compound 2 reacts with [PhNMe₂H]- [BPh₄] to form the ionic complex {[η⁵, η²-C₅H₄(CH₂)₂N(Me) CH₂]V(PMe₃)₂}[BPh₄] (3), in which a methyl group of the pendant NMe₂ functionality is metalated, and 2 equiv of methane. Reaction of 1 with allylmagnesium chloride yields [η⁵-C₅H₄(CH₂) ₂NMe₂]V(η³-C₃H ₅)Cl(PMe₃) (4), in which the amine is released in favor of the η³-bonding of the allyl ligand. Methylation of 4 to yield thermally labile [η⁵-C₅H₄(CH ₂)₂NMe₂]V(η³-C₃H ₅)Me(PMe₃) (5), followed by reaction with [PhNMe ₂H][BPh₄], gives protonation exclusively at the methyl group to yield the ionic allyl complex {[η⁵,η¹- C₅H₄(CH₂)₂NMe₂] V(η³-C₃H₅)(PMe₃)}[BPh ₄] (6) without concomitant NMe₂ maetalation.

Full text of DOI:10.1021/om049660t

3914
Organometallics 2004, 23, 3914-3920
Neu tr a l a n d Ca tion ic Va n a d iu m (III) Alk yl a n d Allyl
Com p lexes w ith a Cyclop en ta d ien yl-a m in e An cilla r y
Liga n d
Guohua Liu, Dirk J . Beetstra, Auke Meetsma, and Bart Hessen*
Center for Catalytic Olefin Polymerization, Stratingh Institute for Chemistry and Chemical
Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
Received May 13, 2004
The (N,N-dimethylaminoethyl)cyclopentadienyl vanadium(III) complex [η5,η1-C5H4(CH2)2-
NMe2]VCl2(PMe3) (1), in which the pendant amine is coordinated to the metal center, was
prepared by the reaction of VCl3(PMe3)2 with Li[C5H4(CH2)2NMe2] in THF. Reaction of 1
with 2 equiv of MeLi yields [η5-C5H4(CH2)2NMe2]VMe2(PMe3)2 (2), in which the amine is
released in favor of the binding of a second phosphine. Compound 2 reacts with [PhNMe2H]-
[BPh4] to form the ionic complex {[η5,η2-C5H4(CH2)2N(Me)CH2]V(PMe3)2}[BPh4] (3), in which
a methyl group of the pendant NMe2 functionality is metalated, and 2 equiv of methane.
Reaction of 1 with allylmagnesium chloride yields [η5-C5H4(CH2)2NMe2]V(η3-C3H5)Cl(PMe3)
(4), in which the amine is released in favor of the η3-bonding of the allyl ligand. Methylation
of 4 to yield thermally labile [η5-C5H4(CH2)2NMe2]V(η3-C3H5)Me(PMe3) (5), followed by
reaction with [PhNMe2H][BPh4], gives protonation exclusively at the methyl group to yield
the ionic allyl complex {[η5,η1-C5H4(CH2)2NMe2]V(η3-C3H5)(PMe3)}[BPh4] (6) without con-
comitant NMe2 metalation.
In tr od u ction
terization is often based on (low temperature) solution
NMR spectroscopy. As the most common oxidation
states of vanadium in relevant organometallic com-
plexes (2+, 3+, 4+) tend to yield paramagnetic species,
this characterization method is distinctly less useful.
In particular the complexes of V(III) (d2, S ) 1), the
oxidation state implicated in many active vanadium-
based polymerization catalyst systems,4 are poorly
accessible either by NMR or EPR spectroscopy. In this
paper we describe the synthesis and characterization
of cationic organometallic species of V(III) bearing an
(N,N-dimethylaminoethyl)cyclopentadienyl ancillary
ligand. This type of ligand has previously been found
to be very useful in the chemistry of transition-metal
organometallics.5 The hard Lewis basic nature of the
pendant amine functionality should have its greatest
affinity for the relatively soft Lewis acidic V(III) center
in its cationic derivatives, making it potentially very
suitable for the stabilization of cationic V(III) alkyl
species.
Catalysts based on the group 5 metal vanadium have
found application in the catalytic polymerization of
alkenes, in particular in the preparation of ethene/
propene and ethene/propene/diene copolymers.1,2 As is
the case for the extensive family of molecular catalysts
based on the group 4 metals, this activity is likely to
derive from the reactivity of electrophilic, probably
cationic, metal alkyl species. It is therefore remarkable
that thus far very little attention has been given to the
synthesis and characterization of cationic vanadium
alkyl complexes.3 One of the possible reasons for this is
that cationic early transition-metal alkyl species tend
to be very reactive and/or thermally labile in the absence
of (olefinic) substrates and that therefore their charac-
* Corresponding author. E-mail: hessen@chem.rug.nl.
(1) For recent relevant reviews, see: (a) Gambarotta, S. Coord.
Chem. Rev. 2003, 237, 229. (b) Hagen, H.; Boersma, J .; Van Koten, G.
Chem. Soc. Rev. 2002, 31, 357. (c) Britovsek, G. J . P.; Gibson, V. C.;
Wass, D. F. Angew. Chem., Int. Ed. 1999, 38, 428.
(2) For recent work involving alkene polymerization by vanadium
catalysts, see: (a) Nakayama, Y.; Bando, H.; Sonobe, Y.; Fujita, T. J .
Mol. Catal. A 2004, 213, 141. (b) Colamarco, E.; Milione, S.; Cuomo,
C.; Grassi, A. Macromol. Rapid Commun. 2004, 25, 450. (c) Wang, W.;
Yamada, J .; Fujiki, M.; Nomura, K.; Catal. Commun. 2003, 4, 159. (d)
Sato, Y.; Nakayama, Y.; Yasuda, H. J . Appl. Polym. Sci. 2003, 89, 1659.
(e) Nomura, K.; Sagara, A.; Imanishi, Y. Macromolecules 2002, 35,
1583. (f) Milione, S.; Cavallo, G.; Tedesco, C.; Grassi, A. J . Chem. Soc.,
Dalton Trans. 2002, 1839. (g) Ruther, T.; Cavell, K. J .; Braussaud, N.
C.; Skelton, B. W.; White, A. H. J . Chem. Soc., Dalton Trans. 2002,
4684. (h) Bradley, S.; Camm, K. D.; Furtado, S. J .; Gott, A. L.;
McGowan, P. C.; Podesta, T. J .; Thornton-Pett, M. Organometallics
2002, 21, 3443. (i) Reardon, D.; Guan, J .; Gambarotta, S.; Yap, G. P.
A.; Wilson, D. R. Organometallics 2002, 21, 4309. (j) Kotov, V. V.;
Avtomonov, E. V.; Sundermeyer, J .; Aitiola, E.; Repo, T.; Lemenovskii,
D. A. J . Organomet. Chem. 2001, 640, 21.
Resu lts a n d Discu ssion
Syn th esis of [η5,η1-C5H4(CH2)2NMe2]VCl2(P Me3)
(1). Reaction of VCl3(PMe3)2, generated in situ from
VCl3(THF)3 and 2 equiv of PMe3 in THF,6 with 1 equiv
of Li[C5H4(CH2)2NMe2],7 followed by extraction with
(4) See for example: Ma, Y.; Reardon, D.; Gambarotta, S.; Yap, G.;
Zahalka, H.; LeMay, C. Organometallics 1999, 18, 2773, and references
therein.
(5) See: (a) Mu¨ller, C.; Vos, D.; J utzi, P. J . Organomet. Chem. 2000,
600, 127. (b) J utzi, P.; Redeker, T. Eur. J . Inorg. Chem. 1998, 663. (c)
J utzi, P.; Siemeling, U J . Organomet. Chem. 1995, 500, 175, and
references therein.
(3) To our knowledge the V(IV) methyl complex [Cp2VMe(NCMe)]-
[BPh4] represents the only structurally characterized example: Chouk-
roun, R.; Lorber, C.; Donnadieu, B. Organometallics 2002, 21, 1124.
(6) Nieman, J .; Teuben, J . H.; Huffman, J . C.; Caulton, K. G. J .
Organomet. Chem. 1983, 255, 193.
10.1021/om049660t CCC: $27.50 © 2004 American Chemical Society
Publication on Web 07/03/2004

Vanadium(III) Alkyl and Allyl Complexes
Organometallics, Vol. 23, No. 16, 2004 3915
F igu r e 1. Molecular structure of 1. Thermal ellipsoids are
drawn at the 50% probability level. Hydrogen atoms have
been omitted for clarity.
Sch em e 1
F igu r e 2. Molecular structure of 2. Thermal ellipsoids are
drawn at the 50% probability level. Hydrogen atoms have
been omitted for clarity.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 2
V-P(1)
V-P(2)
V-C(16)
V-C(17)
V-Cg
2.4829(4)
2.4941(4)
2.206(1)
2.222(1)
1.9864(6)
V-C(1)
V-C(2)
V-C(3)
V-C(4)
V-C(5)
2.313(1)
2.304(1)
2.322(1)
2.334(1)
2.346(1)
P(1)-V-P(2)
124.58(1)
131.05(5)
78.87(4)
79.39(3)
78.39(4)
P(2)-V-C(17)
Cg-V-P(1)
Cg-V-P(2)
Cg-V-C(16)
Cg-V-C(17)
78.92(3)
116.64(2)
118.76(2)
113.49(4)
115.46(4)
C(16)-V-C(17)
P(1)-V-C(16)
P(1)-V-C(17)
P(2)-V-C(16)
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 1
V-Cl bonds, and the sterically demanding iPr group is
pointing downward, minimizing steric hindrance. In 1,
the increased steric hindrance associated with eclipsing
the N-C(8) bond with the V-Cl(1) bond results in a
smaller Cl(1)-V-Cl(2) angle of 117.05(3)° and a longer
V-N bond of 2.342(2) Å (versus 125.53(3)° and
2.290(2) Å in the complex with the secondary amine).
The coordination of the NMe2 functionality in 1 at the
expense of the loss of one PMe3 ligand contrasts with
the noncoordination of the tertiary amine functionalities
in the complexes [η5-C5H4(CH2)3NMe2]VCl2(PMe3)2 and
[η5-C5H4(CH2)2N(CH2)5]VCl2(PMe3)2, as observed by
McGowan and co-workers.2h In the former complex this
is likely to be caused by an unfavorable chelate ring size,
in the latter possibly by a reduced ability to avoid steric
interaction with the chloride ligands.
V-Cl(1)
V-Cl(2)
V-P
2.3719(7)
2.3947(7)
2.5145(8)
2.342(2)
1.968(1)
V-C(1)
V-C(2)
V-C(3)
V-C(4)
V-C(5)
2.328(2)
2.306(2)
2.298(2)
2.288(2)
2.299(2)
V-N
V-Cg
Cl(1)-V-Cl(2)
P-V-N
Cl(1)-V-N
Cl(2)-V-N
Cl(1)-V-P
117.05(3)
149.40(5)
85.39(5)
84.55(5)
80.88(3)
Cl(2)-V-P
Cg-V-N
77.70(2)
102.81(6)
107.64(4)
122.68(4)
120.17(4)
Cg-V-P
Cg-V-Cl(1)
Cg-V-Cl(2)
diethyl ether and recrystallization from warm THF,
gave [η5,η1-C5H4(CH2)2NMe2]VCl2(PMe3) (1, Scheme 1)
as a purple crystalline solid in 83% isolated yield. The
compound is paramagnetic (d2, S ) 1), as seen from the
1
broad resonances in its H NMR spectrum. Neverthe-
Syn t h esis of [η5-C5H 4(CH 2)2NMe2]VMe2(P Me3)2
(2). The cyclopentadienyl-amine vanadium(III) dichlo-
ride complex 1 is a convenient starting material for the
synthesis of further derivatives. The reaction of 1 with
2 equiv of MeLi in diethyl ether, followed by extraction
with and crystallization from pentane, afforded a red
paramagnetic, highly air-sensitive crystalline compound
in moderate yield. A single-crystal X-ray structure
determination of the product (Figure 2, pertinent in-
teratomic distances and angles in Table 2) revealed that
this is the bis(trimethylphosphine) adduct of the vana-
dium(III) dimethyl derivative, [η5-C5H4(CH2)2NMe2]-
VMe2(PMe3)2 (2), in which the pendant amine function-
ality is not coordinated to the metal center. As the
less, resonances that can be attributed to the PMe, NMe,
and CH2 protons are readily distinguished. A single-
crystal X-ray structure determination (Figure 1, perti-
nent interatomic distances and angles in Table 1) shows
that 1 has a four-legged piano-stool structure, with the
coordinated amine and the PMe3 ligand in trans geom-
etry. In these respects its structure is comparable to that
of CpVCl2(PMe3)26 and [η5,η1-C5H4(CH2)2N(H)iPr]VCl2-
(PMe3).8 In the latter complex, the N-H bond of the
coordinated secondary amine is eclipsed with one of the
(7) J utzi, P.; Kleimeier, J . J . Organomet. Chem. 1995, 486, 287.
(8) Witte, P. T.; Meetsma, A.; Hessen, J . H. Organometallics 1999,
18, 2944. The detailed structural data can be found in the Supporting
Information of the paper.

3916 Organometallics, Vol. 23, No. 16, 2004
Liu et al.
Sch em e 2
starting material 1 contains only one PMe3 ligand per
vanadium, the low isolated yield (41%) of 2 and the
presence of a significant amount of dark residue left
after extraction are probably associated with redistribu-
tion of the phosphine ligands during synthesis, produc-
ing 2 in a maximum theoretical yield of 50%. This
should be accompanied by the formation of “[C5H4(CH2)2-
NMe2]VMe2”, the nature of which is as yet unclear
(Scheme 2). Repeating the reaction between 1 and 2
equiv of MeLi with an added equivalent of PMe3
afforded 2 in a significantly higher isolated yield of 83%.
The structure of 2 reveals a normal four-legged piano-
stool geometry, with V-P distances of 2.48-2.49 Å that
are somewhat shorter than those in related dichloride
complexes (2.50-2.52 Å)2h,6,9 and with V-C(Me) dis-
tances of 2.20-2.22 Å. It is likely that the parent
compound CpVMe2(PMe3)2,10 of which previous at-
tempts at a crystal structure determination were unsuc-
F igu r e 3. Molecular structure of the cation of 3. Thermal
ellipsoids are drawn at the 50% probability level. Hydrogen
atoms and the anion have been omitted for clarity.
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Ca tion of 3
V(1)-P(11)
V(1)-P(12)
V(1)-N(1)
V(1)-C(18)
N(1)-C(17)
N(1)-C(18)
2.515(1)
2.472(1)
2.072(3)
2.121(4)
1.488(5)
1.387(5)
N(1)-C(19)
V(1)-C(11)
V(1)-C(12)
V(1)-C(13)
V(1)-C(14)
V(1)-C(15)
1.487(5)
2.275(3)
2.305(4)
2.313(3)
2.280(3)
2.248(3)
P(11)-V(1)-P(12)
P(11)-V(1)-N(1)
P(11)-V(1)-C(18)
P(12)-V(1)-N(1)
P(12)-V(1)-C(18)
95.29(4)
N(1)-V(1)-C(18)
V(1)-N(1)-C(17)
V(1)-N(1)-C(18)
V(1)-N(1)-C(19)
V(1)-C(18)-N(1)
38.6(1)
98.21(9)
120.5(1)
115.32(9)
81.1(1)
115.2(2)
72.6(2)
120.3(3)
68.8(2)
1
cessful, has a similar structure. The H NMR spectrum
of 2 is rather poorly resolved and does not provide much
useful information. Its IR spectrum is informative in
the sense that, in addition to the usual absorptions
associated, for example, with coordinated PMe3 (946,
1279, 1297 cm-1), it shows C-H vibration bands at
2764 and 2799 cm-1 that are absent in 1 and that are
likely to be associated with the NMe νCH of the nonco-
ordinated (CH2)2NMe2 group.11 As such, these vibrations
are useful probes for the behavior of the pendant amine
functionality in paramagnetic complexes. The reason the
metal center in 2 prefers coordination of a second
monodentate phosphine to the pendant amine is per-
haps more likely to be electronic rather than steric in
nature. Vanadium(III) is not a particularly hard Lewis
acid, and the replacement of the two electronegative
chlorides in 1 by two methyls in 2 is likely to increase
the covalent character of the bonding in the complex.
This could lead to a preference for coordination of the
soft Lewis base PMe3 rather than the hard amine,
despite its potentially chelating nature.
the gas evolved in this reaction showed a release of 1.9
equiv of methane per vanadium. This indicates that, in
addition to simple protonation, a sequential reaction
occurs as well. When the reaction was performed on a
preparative scale, a dark red crystalline product was
obtained by cooling a solution in THF. A single-crystal
X-ray structure determination (Figure 3, pertinent
interatomic distances and angles in Table 3) showed
that the product is {[η5,η2-C5H4(CH2)2N(Me)CH2]V-
(PMe3)2}[BPh4] (3), in which one of the NMe2 methyl
groups has been deprotonated (Scheme 2). The resulting
NCH2 moiety is η2-bound to the metal center, with short
V-C(18) and V-N distances of 2.121(4) and 2.072(3) Å
respectively. For comparison, the V-Me distances in 2
are 2.20-2.22 Å and the V-N distance in 1 is 2.342(2)
Å. The remarkably short N-CH2 bond of 1.387(5) Å
(relative to the other two N-C bonds of 1.48 Å) and the
relatively small degree of pyramidalization of the N
atom (the sum of the C-N-C angles is 348.2°, compared
to 331.1° in the free amine of complex 2) suggest that
the V(I) η2-iminium resonance state may be important
in determining the overall structure of the cation of 3
(Scheme 2). In fact, the geometry of the cation strongly
resembles that of the neutral V(I) ethene complex CpV-
(η2-C2H4)(PMe3)2.12 The relatively soft Lewis acidic
character of the metal center is shown by the preference
Rea ction of 2 w ith [P h NMe2H][BP h 4]. In an
attempt to generate a cationic V(III) monomethyl de-
rivative from the dimethyl complex 2, this compound
was reacted with the Brønsted acid [PhNMe2H][BPh4]
in THF solvent. An experiment performed using a
Toepler pump to determine the amount and nature of
(9) Bottcher, C.; Schmidt, H.; Rehder, D. J . Organomet. Chem. 1999,
580, 72.
(10) (a) Hessen, B.; Teuben, J . H.; Lemmen, T. H.; Huffman, J . C.;
Caulton, K. G. Organometallics 1985, 4, 946. (b) Hessen, B.; Lemmen,
T. H.; Luttikhedde, H. J . G.; Teuben, J . H.; Petersen, J . L.; Huffman,
J . C.; J agner, S.; Caulton, K. G. Organometallics 1987, 6, 2354.
(11) (a) Lappert, M. F.; Sanger, A. R. J . Chem. Soc. A 1971, 874. (b)
Visser, C.; Van den Hende, J . R.; Meetsma, A.; Hessen, B.; Teuben, J .
H. Organometallics 2001, 20, 1620.
(12) (a) Hessen, B.; Meetsma, A.; Van Bolhuis, F.; Teuben, J . H.;
Helgesson, G.; J agner, S. Organometallics 1990, 9, 1925. (b) Hessen,
B.; Meetsma, A.; Teuben, J . H. J . Am. Chem. Soc. 1988, 110, 4860.

Vanadium(III) Alkyl and Allyl Complexes
Organometallics, Vol. 23, No. 16, 2004 3917
to bind the two phosphine ligands originally present in
2, rather than the hard Lewis base THF that is used as
a solvent.
The metalation of pendant ligand NMe2 fragments via
σ-bond metathesis with a metal hydride or alkyl func-
tionality is not unprecedented.13 It is nevertheless
remarkable that this reaction is so efficient here,
especially in a coordinating solvent like THF that
potentially could block the coordination site required for
σ-bond metathesis to proceed. When the reaction is
performed in THF-d8 in an NMR tube, no evidence was
found for an intermediate with a lifetime at ambient
temperature that would allow its observation by 1H
NMR. This suggests that, after initial protonation of one
of the methyl groups of 2, the subsequent ligand
metalation is a fast reaction. Cyclopentadienyl-amine
Ti(III) and Cr(III) systems have been shown to be highly
active catalysts for alkene polymerization,14 but their
cationic monoalkyl species have not been extensively
investigated. Interestingly, in the tetramethylcyclopen-
tadienyl-amine chromium system, solids of composition
{[Cp-amine]CrMe}[A] (A ) MeB(C6F5)3, B[C6H3(CF3)2]4)
were isolated, but were found to be catalytically
inactive.14c The observations made here suggest that
these ancillary ligands are not necessarily innocent after
generation of the active catalyst species.
F igu r e 4. Molecular structure of the cation of 6 (majority
orientation in the lattice). Thermal ellipsoids are drawn
at the 50% probability level. Hydrogen atoms and the anion
have been omitted for clarity.
Sch em e 3
Cyclop en ta d ien yl-a m in e Va n a d iu m Allyl Com -
p lexes. Reaction of the dichloride 1 with 1 equiv of
allylmagnesium chloride in diethyl ether, followed by
extraction with pentane, afforded a red oil that sepa-
rated from the solution upon cooling the concentrated
pentane extract to -80 °C. Although this compound is
again paramagnetic, showing a set of poorly resolved
broad resonances in its 1H NMR spectrum, useful
information as to its nature can be obtained from the
IR spectrum. An absorption at 1517 cm-1 indicates the
presence of an η3-allyl ligand.15 In addition to the
absorptions associated with PMe3 (955, 1262, 1280
cm-1), C-H absorptions are observed at 2766 and 2778
cm-1, indicative of a noncoordinated NMe2 group, as was
seen for 2. This suggests that the product may be
formulated as [η5-C5H4(CH2)2NMe2]V(η3-C3H5)Cl(PMe3)
(4, Scheme 3), in which a trihapto coordination of the
allyl group is preferred over the intramolecular coordi-
nation of the pendant amine. On the basis of this
formulation, compound 4 was obtained in 47% isolated
yield. Subsequently, the allyl chloride complex 4 was
reacted with MeLi in order to produce the allyl methyl
complex 5 (Scheme 3). The product of this reaction is
thermally labile, even at 0 °C. This low thermal stability
is comparable to that of the allyl methyl complex
CpV(η3-C3H5)Me(PMe3) reported previously.10b Never-
theless, the compound could be precipitated as a brown-
red oil in 48% crude yield by cooling a concentrated
solution in pentane. This product was used in a subse-
quent reaction with the Brønsted acid [PhNMe2H]-
[BPh4] in THF solvent. Crystallization from THF af-
forded the ionic complex {[η5,η1-C5H4(CH2)2NMe2]V(η3-
C3H5)(PMe3)}[BPh4] (6, Scheme 3) as red crystals in 41%
isolated yield. A single-crystal structure determination
was complicated by a disorder problem: the complex
appears to be present in the lattice in two different
orientations, the minor fraction having a site occupancy
factor of about 0.22 (as seen from a refinement including
two separate metal atom positions). This is too low to
allow for a separate refinement of the ligand environ-
ment of the minor fraction. Nevertheless, the observed
non-hydrogen positions of the major fraction (Figure 4)
are consistent with the formulation of 6 as given above.
Additional support is obtained by elemental analysis
(consistent with the proposed composition) and IR
spectroscopy. The latter shows that the C-H absorption
bands characteristic of a noncoordinating pendant
amine (as in 2 and 4) are now absent, indicating
coordination of the amine, and also that an η3-allyl
absorption is present at 1523 cm-1. Thus it appears that
in the reaction of 5 with the Brønsted acid the proto-
nation occurs preferentially at the methyl group. This
was corroborated by an experiment on a vacuum line
with Toepler pump that showed exclusively the forma-
(13) For an example of methyl metalation of a pendant dimethyl-
aminoethyl functionality on a cyclopentadienyl group, see: Mu, Y.;
Piers, W. E.; MacQuarrie, D. C.; Zaworotko, M. J .; Young, V. G., J r.
Organometallics 1996, 15, 2720.
(14) (a) Arts, H. J .; Eggels, G. H. M.; Gruter, G. J . M.; Van Beek, J .
A. M.; Van Doremaele, G. H. World Pat. WO 96/13529. (b) J olly, P.
W.; J onas, K.; Verhovnik, G. P. J .; Dohring, A.; Gohre, J .; Weber, J . C.
World Pat. WO 98/04570. (c) Dohring, A.; Gohre, J .; J olly, P. W.;
Kryger, B.; Rust, J .; Verhovnik, G. P. J . Organometallics 2000, 19,
388.
(15) (a) J onas, K.; Wiskamp, V. Z. Naturforsch. 1983, 38B, 1113.
(b) Nieman, J .; Pattiasina, J . W.; Teuben, J . H. J . Organomet. Chem.
1984, 262, 157. (c) Brussee, E. A. C.; Meetsma, A.; Hessen, B.; Teuben,
J . H. Organometallics 1998, 17, 4090.

3918 Organometallics, Vol. 23, No. 16, 2004
Liu et al.
spectrometer from Nujol mulls between KBr disks, unless
mentioned otherwise. Elemental analyses were performed by
Kolbe Analytical Laboratories, Mu¨lheim a.d. Ruhr, Germany.
Syn th esis of [η5,η1-C5H4(CH2)2NMe2]VCl2(P Me3) (1).
PMe3 (2 mL, 20.5 mmol) was added at ambient temperature
to a suspension of VCl3(THF)3 (4.20 g, 11.2 mmol) in 25 mL of
THF. The resulting brown solution was stirred for 1 h and
then cooled to -80 °C, after which Li[C5H4(CH2)2NMe2] (1.683
g, 11.76 mmol) was added. The mixture was allowed to warm
to ambient temperature, during which the color changed via
red to deep purple. After stirring for 72 h the volatiles were
removed in vacuo and remaining THF was removed by stirring
the mixture twice with 15 mL of diethyl ether, which was
subsequently pumped off. The residue was repeatedly ex-
tracted with 50 mL of diethyl ether. The solvent was then
removed in vacuo and the residue was dissolved in 10 mL of
hot THF. Gradually cooling to -60 °C yielded 2.08 g of a purple
crystalline solid. Subsequent recrystallization of the material
left in the mother liquor from THF/pentane resulted in another
portion of 1.03 g of material. The combined yield of the title
compound was 3.11 g (9.31 mmol, 83%). IR (Nujol/KBr): 3103
(vw), 1422 (mw), 1330 (w), 1294 (w), 1276 (mw), 1260 (m), 1239
(w), 1208 (w), 1166 (vw), 1114 (w), 1096 (w), 1076 (w), 1060
(mw), 1044 (mw), 1022 (s), 1004 (m), 944 (s), 918 (m), 877 (vw),
825 (m), 807 (s), 779 (mw), 726 (m), 696 (w), 665 (w), 627 (w)
tion of methane. After generation of the cationic species,
the intramolecular coordination of the pendant amine
is preferred over coordination of a THF molecule from
the solvent.
Con clu sion s
From the chemistry of the (N,N-dimethylaminoethyl)-
cyclopentadienyl vanadium(III) complexes described
here it can be seen that the affinity of the V(III) center
for the pendant hard Lewis basic amine is only modest,
despite its favorable orientation for chelation. In the
neutral derivatives it can compete with PMe3 only when
electronegative chlorides are attached to the metal, and
it is displaced by η3 coordination of an allyl ligand. In
the cationic derivatives the affinity for the amine is
enhanced, and there it is preferred as ligand over the
hard Lewis base THF that is used as the solvent.
Metalation of the methyl substitents of the pendant
amine upon generation of the monomethyl cation turned
out to be remarkably easy, even in a potentially coor-
dinating solvent like THF. This could present complica-
tions when the NMe2 group is used in ancillary ligand
systems for catalytic olefin polymerization. Neverthe-
less, the cationic allyl complex 6 appears to be stable
toward ligand metalation at ambient temperature,
suggesting that the stability of such cationic species is
dependent on a more complex set of variables.
Making use of the (N,N-dimethylaminoethyl)cyclo-
pentadienyl ligand, it thus proved possible to generate
and characterize cationic V(III) hydrocarbyl species
successfully. The isolated ionic complexes 3 and 6
described here are themselves not active in catalytic
olefin polymerization.16 Both are 16 valence electron
species with an S ) 1 configuration, rendering them
unreactive toward Lewis basic substrates such as ethene
without prior phosphine ligand dissociation. Neverthe-
less, it does show that cationic V(III) hydrocarbyl species
can be readily and selectively generated from well-
defined bis-hydrocarbyl precursors. Synthetic and cata-
lytic studies on related phosphine-free systems are in
progress.
1
cm-1. H NMR (300 MHz, C6D6, 20 °C): δ 17 (∆ν1/2 ) 710 Hz,
CH2), 1 (∆ν1/2 ) 1070 Hz, NMe2), -15 (∆ν1/2 ) 1080 Hz, CH2),
-21 (∆ν1/2 ) 1280 Hz, PMe3). Anal. Calcd for C12H23Cl2NPV:
C, 43.12; H, 6.94; N, 4.19. Found: C, 43.27; H, 6.90; N, 4.54.
Syn th esis of [η5-C5H4(CH2)2NMe2]VMe2(P Me3)2 (2). (a )
With ou t Ad d ed P Me3. Methyllithium (7.66 mmol, as a 1.6
M solution in diethyl ether) was added to a solution of 1 (1.28
g, 3.83 mmol) in 30 mL of diethyl ether, cooled to -80 °C. After
addition, the mixture was allowed to warm to -10 °C, after
which it was stirred at this temperature for 2 h. The volatiles
were removed in vacuo, and residual ether was removed by
stirring the mixture twice with a portion of cold (0 °C) pentane,
which was subsequently pumped off. The solid was extracted
repeatedly with cold pentane, leaving a dark residue. Concen-
tration and cooling of the extract to -30 °C yielded 0.70 g of
the title compound as red crystals (1.90 mmol, 41%).
(b) With Ad d ed P Me3. The procedure was followed as
described above (using 0.49 g, 1.47 mmol of 1 in 15 mL of
diethyl ether, and 2.92 mmol of MeLi), with the difference that,
before adding the MeLi solution, first 0.14 mL (1.47 mmol) of
PMe3 was added to the solution of 1. Via the same workup
procedure, 0.45 g (1.22 mmol, 83%) of red crystalline 2 was
obtained. IR (Nujol/KBr): 3088 (w), 2799 (mw), 2764 (w), 1422
(mw), 1297 (mw), 1279 (s), 1214 (w), 1168 (w), 1129 (w), 1097
(w), 1042 (m), 1018 (vw), 946 (vs), 859 (vw), 840 (m), 785 (s),
718 (s), 665 (w) cm-1.1H NMR (300 MHz, C6D6, 20 °C): δ 5
(∆ν1/2 ) 380 Hz, with shoulder, NMe2+CH2), -4.5 (∆ν1/2 ) 1090
Hz, PMe3). Anal. Calcd for C17H38NP2V: C, 55.28; H, 10.37;
N, 3.79. Found: C, 55.18; H, 10.43; N, 3.70.
Exp er im en ta l Section
Gen er a l Rem a r k s. All preparations were performed under
an inert nitrogen atmosphere, using standard Schlenk or
glovebox techniques. Pentane (Aldrich, anhydrous, 99.8%) was
passed over columns of Al2O3 (Fluka), BASF R3-11-supported
Cu oxygen scavenger, and molecular sieves (Aldrich, 4 Å).
Diethyl ether and THF (Aldrich, anhydrous, 99.8%) were dried
over Al2O3 (Fluka). All solvents were degassed prior to use and
stored under nitrogen. Deuterated solvents (C6D6, C4D8O;
Aldrich) were vacuum transferred from Na/K alloy prior to use.
VCl3(THF)3 was prepared from VCl3 (Merck) by continuous
extraction with THF. PMe3,17 Li[C5H4(CH2)2NMe2],7 and
[PhNMe2H][BPh4]18 were prepared via published procedures.
1H NMR spectra were recorded on a Varian VXR-300 spec-
trometer in NMR tubes sealed with a Teflon (Young) stopcock.
IR spectra were recorded on a Mattson-4020 Galaxy FT-IR
Syn th esis of {[η5,η2-C5H4(CH2)2N(Me)CH2]V(P Me3)2}-
[BP h 4] (3). A mixture of 2 (0.32 g, 0.87 mmol) and [PhNMe2H]-
[BPh4] (0.36 g, 0.85 mmol) was dissolved in 20 mL of THF at
0 °C. After stirring overnight, the solution was concentrated
and cooled to -30 °C to yield the title compound (0.36 g, 0.54
mmol, 65%) as dark red crystals. IR (Nujol/KBr): 3048 (w),
3022 (vw), 1579 (mw), 1420 (m), 1326 (vw), 1307 (w), 1287 (m),
1266 (mw), 1247 (vw), 1225 (mw), 1181 (w), 1152 (m), 1120
(m), 1107 (m), 1065 (mw), 1029 (mw) 1016 (w), 945 (s), 862
(vw), 842 (w), 814 (m), 741 (sh), 731 (s), 705 (s), 667 (vw) cm-1
.
1H NMR (300 MHz, THF-d8, 20 °C): δ 13 (∆ν1/2 ) 700 Hz,
PMe3), 7.3 and 6.8 (BPh4), -7.5 (∆ν1/2 ) 660 Hz). Anal. Calcd
for C39H51BNP2V: C, 71.24; H, 7.82; N, 2.13. Found: C, 71.09;
H, 7.71; N, 2.06.
(16) Stirring 3 or 6 in toluene in the presence of isobutyl alumoxane
impurity scavenger (Al:V ) 10:1) at ambient temperature under 5 bar
ethene pressure for 30 min did not yield any polyethene.
(17) Prepared according to Inorg. Synth. 1989, 26, 7, but using
MeMgI instead of MeMgBr.
(18) [PhNMe2H][BPh4] was prepared using N,N-dimethylaniline
following the procedure reported for [Et3NH][BPh4]: Eshuis, J . J . W.;
Tan, Y. Y.; Meetsma, A.; Teuben, J . H. Organometallics 1992, 11, 362.
Toep ler P u m p Exp er im en t of th e Rea ction of 2 w ith
[P h NMe2H][BP h 4]. On a vacuum line, 3 mL of THF was
condensed onto a mixture of 2 (81 mg, 0.22 mmol) and

Vanadium(III) Alkyl and Allyl Complexes
Organometallics, Vol. 23, No. 16, 2004 3919
Ta ble 4. Cr ysta l Da ta for Com p ou n d s 1, 2, 3, a n d 6
1
2
3
6
empirical formula
fw
C
12H23Cl2NPV
C17H38NP2V
369.38
C39H51BNP2V
657.54
C39H48BNPV
623.54
334.12
temperature (K)
cryst size (mm)
space group
a (Å)
b (Å)
c (Å)
180(2)
100(1)
100(1)
100(1)
0.15 × 0.25 × 0.25
0.53 × 0.41 × 0.17
0.14 × 0.12 × 0.09
0.48 × 0.38 × 0.09
P21/n
P21/c
Pna21
Pna21
10.119(1)
11.660(1)
13.184(1)
98.75(1)
1537.4(2)
4
1.444
10.8
696
14.1732(8)
9.6636(5)
16.6389(9)
111.624(1)
2118.5(2)
4
1.158
6.15
800
23.287(1)
15.1524(7)
10.2341(4)
23.038(2)
15.084(1)
9.8631(8)
â (deg)
V (Å3)
3611.1(3)
4
1.209
3.91
1400
3427.5(5)
4
1.208
3.63
1328
Z
dc (g cm-3
)
µ (cm-1
F(000)
)
θ range (deg)
2.34 to 27.47
-13 e h e 12
0 e k e 15
0 e l e 17
3833
3502
2814
0.0942
2.48 to 27.45
-18 e h e 18
-12 e k e 12
-21 e l e 21
17844
4793
4335
0.0692
2.21 to 24.56
-31 e h e 31
-19 e k e 19
-13 e l e 12
32392
8792
7193
0.1449
2.22 to 25.02
-24 e h e 27
-16 e k e 17
-11 e l e 11
19082
5951
4043
0.2127
index range
no. of reflns collected
no. of unique reflns
no. of reflns with Fo g 4σ(Fo)
wR(F2)
a, b
R(F)
0.0581, 0.2038
0.0355
0.0421, 0.4119
0.0254
0.0759, 1.66
0.0582
0.1, 0.0
0.0855
no. of data/params/restraints
Flack’s x
3502/246/0
4793/342/0
8792/574/1
0.02(3)
1.037
5951/463/1
0.08(6)
1.217
GOF on F2
1.073
0.87(8), -0.44(8)
1.027
0.40(5), -0.15(5)
largest diff peak/hole (e Å-3
)
1.06(8), -0.58(8)
0.7(1), -0.5(1)
1
[PhNMe2H][BPh4] (97 mg, 0.22 mmol) frozen in liquid nitrogen.
The mixture was thawed out and stirred at ambient temper-
ature overnight. Repeated freeze-thaw cycles on the Toepler
pump yielded 0.423 mmol of gas, determined by CG to be
methane (1.92 equiv per V).
951 (mw), 874 (w), 812 (m), 743 (sh), 732 (s), 707 (s) cm-1. H
NMR (300 MHz, THF-d8, 20 °C): δ 7.3 and 6.8 (BPh4), -2.0
(∆ν1/2 ) 430 Hz, PMe3). No other well-defined resonances could
be discerned. Anal. Calcd for C39H49BNPV: C, 75.00; H, 7.91;
N, 2.24. Found: C, 75.15; H, 7.86; N, 2.29.
Syn th esis of [η5-C5H4(CH2)2NMe2]V(η3-C3H5)Cl(P Me3)
(4). Allylmagnesium chloride (1.41 mmol as a 0.80 M solution
in diethyl ether) was added dropwise to a solution of 1 (0.47
g, 1.41 mmol) in 10 mL of THF cooled to 0 °C. After stirring
at this temperature for 3 h, the volatiles were removed in
vacuo and any residual solvent was removed by stirring the
residue twice with 10 mL of pentane (0 °C), which was
subsequently pumped off. The mixture was repeatedly ex-
tracted with 30 mL of pentane. Concentration and cooling of
the extract to -80 °C yielded the title compound as a red oil
(0.22 g, 0.65 mmol, 47%). IR (neat/KBr): 3080 (m), 2966 (s),
2928 (s), 2907 (s), 2814 (m), 2778 (m), 2766 (m), 1517 (mw),
1416 (s), 1426 (m), 1280 (m), 1262 (m), 1200 (mw), 1096 (w),
1042 (m), 1020 (m), 1003 (w), 955 (s), 921 (w), 861 (mw), 803
Toep ler P u m p Exp er im en t of th e Rea ction of 5 w ith
[P h NMe2H][BP h 4]. On a vacuum line, THF (5 mL) was
condensed onto a mixture of crude 5 (obtained as described
above, 130 mg, 0.41 mmol) and [PhNMe2H][BPh4] (163 mg,
0.37 mmol) frozen in liquid nitrogen. The mixture was thawed
out and stirred overnight at ambient temperature. Repeated
freeze-thaw cycles on the Toepler pump yielded 0.31 mmol
of gas, determined by CG to be methane (0.83 equiv per
anilinium). No formation of propene was observed.
Str u ctu r e Deter m in a tion s. Suitable crystals for single-
crystal X-ray diffraction were obtained by cooling solutions of
the compounds in THF (1, 3, and 6) or pentane (2). Crystals
were mounted on a glass fiber inside a drybox and transferred
under inert atmosphere to the cold nitrogen stream of a Bruker
SMART APEX CCD diffractometer (2, 3, and 6) or an Enraf-
Nonius CAD-4F diffractometer (1). Intensity data were col-
lected with Mo KR radiation (λ ) 0.71073 Å). Intensity data
were corrected for Lorentz and polarization effects. A semiem-
pirical absorption correction was applied, based on the intensi-
ties of symmetry-related reflections measured at different
angular settings (SADABS19). The structures were solved by
Patterson methods, and extension of the models was ac-
complished by direct methods applied to difference structure
factors using the program DIRDIF.20 Hydrogen atom coordi-
nates and isotropic thermal parameters were refined freely
unless mentioned otherwise. For 3, the hydrogen atoms on
C(17), C(18), and C(19) were included riding on their carrier
atoms. The crystals of 6 that could be obtained showed weak
scattering power. In the difference Fourier map a peak of 3.7
e Å-3 was observed at a distance of about 1 Å of the V atom.
This suggests that in the lattice the complex is also present
1
(s), 779 (sh), 730 (w) cm-1. H NMR (300 MHz, C6D6, 20 °C):
δ 27 (∆ν1/2 ) 900 Hz), 2.3 (∆ν1/2 ) 30 Hz, NMe2), -8.5 (∆ν1/2
)
410 Hz, PMe3), -21 (∆ν1/2 ) 480 Hz). Two other broad,
relatively small and partially obscured resonances are found
around δ 12 and -11 ppm.
Gen er ation of [η5-C5H4(CH2)2NMe2]V(η3-C3H5)Me(P Me3)
(5) a n d Syn th esis of {[η5,η1-C5H4(CH2)2NMe2]V(η3-C3H5)-
(P Me3)}[BP h 4] (6). MeLi (0.66 mmol as a 1.6 M solution in
diethyl ether) was added dropwise to a solution of 4 (0.22 g,
0.66 mmol) in 5 mL of THF, cooled at -70 °C. After addition,
the mixture was allowed to warm to -20 °C and was stirred
for 2 h at this temperature. The solvent was removed in vacuo,
and residual THF was removed by stirring the mixture twice
with 5 mL of cold (0 °C) pentane, which was subsequently
pumped off. The solid was repeatedly extracted with 30 mL of
pentane. Concentrating the extract to a small volume and
cooling to -30 °C precipitated 5 as a brown-red oil, of which
0.10 g (0.32 mmol) was recovered. This was dissolved in 10
mL of THF together with [PhNMe2H][BPh4] (131 mg, 0.30
mmol). After stirring overnight, the solution was concentrated
and cooled to -30 °C to yield 6 (76 mg, 0.12 mmol, 41% on 5)
as red crystals. IR (Nujol/KBr): 3048 (w), 1579 (w), 1523 (w),
1291 (w), 1261 (m), 1150 (w), 1096 (mw), 1028 (m), 1017 (m),
(19) Sheldrick, G. M. SADABS Version 2, Empirical Absorption
Correction Program; University of Go¨ttingen: Germany, 2000.
(20) Beurskens, P. T.; Beurskens, G.; De Gelder, R.; Garc´ıa-Granda,
S.; Gould, R. O.Israe¨l, R.; Smits, J . M. M. The DIRDIF-99 program
system; Crystallography Laboratory, University of Nijmegen: The
Netherlands, 1999.

3920 Organometallics, Vol. 23, No. 16, 2004
Liu et al.
in a different orientation. The metal center was refined as
occupying two positions, with the smallest fraction, V(1b),
refining to a sof of 0.22. It was impossible to locate the ligand
set belonging to this orientation, resulting in some atoms
showing unrealistic displacement parameters. Nevertheless,
the connectivity of the non-hydrogen atoms of the major
component could be unequivocally established. All refinements
and geometry calculations were performed with the program
packages SHELXL21 and PLATON.22 Crystallographic data
and details of the data collections and structure refinements
are listed in Table 4.
Ack n ow led gm en t. This work was supported by The
Netherlands Foundation for Chemical Sciences (C.W.)
with financial aid from The Netherlands Organization
for Scientific Research (N.W.O.).
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data for 1, 2, 3, and 6 including atomic coordinates, full bond
distances and bond angles, as well as anisotropic thermal
parameters. This material is available free of charge via the
Internet at http://pubs.acs.org.
(21) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen: Germany, 1997.
(22) Spek, A. L. PLATON, Program for the Automated Analysis of
Molecular Geometry, Version April 2000; University of Utrecht: The
Netherlands, 2000.
OM049660T