Synthesis and structure of amino-functionalized cyclopentadienyl vanadium complexes and evaluation of their butadiene polymerization behavior

Article abstract of DOI:10.1021/om020170f

The synthesis and structure of amino-functionalized cyclopentadienyl vanadium complexes were studied. The catalytic behavior of some of the complexes toward butadiene was evaluated. Amino-functionalized cyclopentadienyl vanadium phosphine chloride complexes behaved much differently from their nonfunctionalized cyclopentadienyl derivatives. A cyclopentadienyl ligand with an amino-functionalized side chain acted as a bidentate ligand.

Full text of DOI:10.1021/om020170f

Organometallics 2002, 21, 3443-3453
3443
Syn th esis a n d Str u ctu r e of Am in o-F u n ction a lized
Cyclop en ta d ien yl Va n a d iu m Com p lexes a n d Eva lu a tion
of Th eir Bu ta d ien e P olym er iza tion Beh a vior
Sam Bradley, Kenneth D. Camm, Stephen J . Furtado, Andrew L. Gott,
Patrick C. McGowan,* Thomas J . Podesta, and Mark Thornton-Pett
Department of Chemistry, University of Leeds, Leeds LS2 9J T, U.K.
Received February 27, 2002
We have synthesized a number of bis-1,1,-amino-functionalized vanadocenes and vana-
docene monochlorides; the bis-1,1,-amino-functionalized vanadocenes represent the first
examples of structurally characterized compounds of this type, and the bis-1,1,-amino-
functionalized vanadocene monochlorides represent the first examples synthesized and
characterized. We report the catalytic behavior of some of the complexes toward butadiene
and observe that amino-functionalized cyclopentadienyl vanadium phosphine chloride
complexes behave much differently from their nonfunctionalized cyclopentadienyl derivatives.
In tr od u ction
Although under identical conditions, the titanium ana-
logue has significantly higher productivity (532 kg PE
(mol Ti)-1 h-1 bar-1 cf. 209 kg PE (mol V)-1 h-1 bar-1 ).
The polymer produced is also of much lower molecular
weight for the vanadium system. V{η-C5H4(CH2)2NPri}-
Cl2 does not polymerize propene, whereas the titanium
analogue is an active catalyst.9 Monocyclopentadienyl
complexes of vanadium have also been used to catalyze
the hydrogenation and isomerization of alkenes.10,11
Group VI monocyclopentadienyl chromium compounds
with linked amino side chains have been investigated
as a novel class of alkene polymerization catalysts.12,13
These are very promising catalysts for the oligomeriza-
tion and polymerization of ethene and copolymerization
of ethene with 1-hexene.
Other types of catalysis using group V compounds
include V(η-C5H5)2Cl, which has been reported as a
catalyst for the polymerization of 1,3-dienes.14 Unlike
other known vanadium systems, which afford trans
polymer, e.g., V(acac)3, vanadocene monochloride gave
material of a predominantly cis configuration.14 Another
type of catalyst is the monocyclopentadienyl complex
V(η-C5H4Me)(PEt3)2Cl2, which has also been explored
as a catalyst for the polymerization of butadiene.14 It
has considerably higher activity than vanadocene
monochloride and also affords cis polybutadiene.
With this application in mind, it was decided that the
synthesis and exploration of the potential catalytic
behavior of a number of V(II), V(III), and V(IV) mono-
and bis-cyclopentadienyl amino-functionalized cyclo-
A cyclopentadienyl ligand with an amino-functional-
ized side chain may act as a bidentate ligand.1 This
could potentially stabilize electron-deficient metal cen-
ters by intramolecular coordination, thus providing a
means of isolating and characterizing previously highly
reactive intermediates and products.1 The incorporation
of an amino-functionalized group can often have a
dramatic effect on the catalytic activity of organome-
tallic complexes. For example, intramolecular coordina-
tion to a vacant coordination site is of particular interest
for catalytic applications, e.g., polymerization of alkenes.
This is illustrated by the following example. Despite the
parent compound Ti(η-C5H5)Cl3 being virtually inactive
when used with MAO as a cocatalyst, the linked
cyclopentadienyl-amino compound Ti(η-C5H4CH2CH2-
NMe2)Cl3 was found to exhibit good activity toward
ethene and propene polymerization.2 The study was
3
later extended to include Ti(η-C5Me4CH2CH2NMe2)Cl3
and the indenyl complex Ti(η-C9H7CH2CH2NMe2)Cl3.4
There are also a number of group IV linked cyclopen-
tadienyl-amido complexes that exhibit catalytic be-
havior.5-8
Pendant arm group V complexes are less common.
The vanadium complex V{η-C5H4(CH2)2NPri}Cl2 has
been used to catalyze the polymerization of R-olefins.9
* Corresponding author. E-mail: p.c.mcgowan@chem.leeds.ac.uk.
(1) J utzi, P.; Redeker, T. Eur. J . Inorg. Chem. 1998, 663-674.
(2) Flores, J . C.; Chien, J . C. W.; Rausch, M. D. Organometallics
1994, 13, 4140-4142.
(3) Flores, J . C.; Chien, J . C. W.; Rausch, M. D. Macromolecules
1996, 29, 8030-8035.
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2944-2946.
(4) Blais, M. S.; Chien, J . C. W.; Rausch, M. D. Organometallics
1998, 17, 3775-3783.
(10) 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, 2354-2362.
(5) Gomes, P. T.; Green, M. L. H.; Martins, A. M.; Mountford, P. J .
Organomet. Chem. 1997, 541, 121-125.
(11) Nieman, J .; Teuben, J . H.; Huffman, J . C.; Caulton, K. G. J .
Organomet. Chem. 1983, 255, 193-204.
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Verhovnik, G. P. J . Organometallics 2000, 19, 388-402.
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G. P. J . Organometallics 1997, 16, 1511-1513.
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10.1021/om020170f CCC: $22.00 © 2002 American Chemical Society
Publication on Web 07/12/2002

3444 Organometallics, Vol. 21, No. 16, 2002
Bradley et al.
Sch em e 1a
a
(i) THF.
Ta ble 1. Selected In ter a tom ic Dista n ces (Å) a n d
An gles betw een In ter a tom ic Vector s (d eg) of 4
w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th esesa
pentadienyl complexes was of interest. To achieve this,
it was necessary to find viable synthetic routes to the
syntheses of these types of compounds, and this paper
represents a summary of our methodology and results.
Preliminary studies investigating the catalytic activity
of these novel compounds toward butadiene and for the
polymerization of olefins will be presented. We have
previously communicated the preparation of the bis-1,1,-
amino-functionalized vanadocenes.15 We have also had
success with these types of ligand systems in the
isolation of rhodium,16,17 sodium,16 yttrium,18 tita-
nium,19,20 and iron systems.15,21,22
V(1)-C(1)
V(1)-C(2)
V(1)-C(3)
V(1)-C(4)
V(1)-C(5)
V(1)-C(6)
V(1)-C(7)
V(1)-C(8)
V(1)-C(9)
V(1)-C(10)
2.3044(13)
2.2734(13)
2.3177(14)
2.333(2)
2.2845(13)
2.2963(12)
2.2726(13)
2.324(2)
C(1)-C(2)
1.434(2)
1.473(2)
1.407(2)
1.457(2)
1.450(2)
1.449(2)
1.456(2)
1.406(2)
1.470(2)
1.429(2)
1.44
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(1)
C(6)-C(7)
C(7)-C(8)
C(8)-C(9)
2.324(2)
2.2852(13)
C(9)-C(10)
C(10)-C(6)
average C-C
V(1)-Cp(cent)(1)
V(1)-Cp(cent)(2)
1.95
1.95
Resu lts a n d Discu ssion
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(1)
C(5)-C(1)-C(2)
C(6)-C(7)-C(8)
C(7)-C(8)-C(9)
109.92(13) Cp(cent)(1)-V(1)-Cp(cent)(2) 179
107.80(13) C(11)-C(1)-Cp(cent)(1)
106.95(13) C(61)-C(6)-Cp(cent)(2)
110.69(13) average C-C-C
104.63(12)
177
175
108
The characterization of vanadocenes is not facile due
to the intrinsic properties of the complexes; vanadocenes
are extremely air- and moisture-sensitive paramagnetic
compounds. The problem is made even more difficult
due to the inherent instability associated with amino-
functionalized cyclopentadienyl metal complexes com-
pared with the nonsubstituted analogues. This has been
observed by ourselves19,20 and others with amino-
functionalized Cp2TiCl2 systems.23 The problem of ob-
taining good characterizing data becomes even more
exasperating since some of the vanadocenes are oils or
low-melting solids, thus preventing single-crystal X-ray
structure analysis. The reaction between 8 equiv of the
amino-substituted cyclopentadienide sodium salts and
[(V2Cl3)(thf)6]2[Zn2Cl6]24,25 was found to yield the amino-
functionalized vanadocenes V{η-C5H4(CH2)2NMe2}2 (1),
V{η-C5H4(CH2)3NMe2}2 (2), V{η-C5H4(CH2)3NH2}2 (3),
V{C5H4CH(CH2)4NMe}2 (4), V{η-C5H4(CH2)2N(CH2)5}2
(5), and V{η-C5H4CH2(C5H4N)}2 (6) as shown in Scheme
1. Compounds 1-3 and 6 are extremely air- and water-
110.53(14)
106.75(13)
C(8)-C(9)-C(10) 108.13(13)
C(9)-C(10)-C(6) 109.59(13)
C(10)-C(6)-C(7) 104.99(12)
a
Cp(cent)(1) and Cp(cent)(2) denote centroids of the rings C(1)-
C(5) and C(6)-C(10), respectively.
sensitive bright purple oils and crystalline solids, and
the oils proved particularly difficult to handle.
Evidence for the difficulties in synthesis and charac-
terization for vanadocenes is exemplified by the syn-
thesis of V{η-C5H4R}2 (R ) Me, Pri), which are oils for
which there is no characterization data.26 The oil V{η-
C5H4(CH2)2NMe2}2 was obtained by the in situ reduction
of VCl3‚3thf with LiAlH4.27 We found this method
difficult to repeat. Steric modifications of the pendant
arm induce crystallinity to the sample. This paper
represents the first examples of structurally character-
ized amino-substituted bis-cyclopentadienyl vanadium
systems. Recrystallization of 4 from diethyl ether af-
forded crystals suitable for X-ray structure analysis
(Table 1 shows selected bond lengths and selected bond
angles). The molecular structure of V{η-C5H4CH(CH2)4-
NMe}2 (Figure 1) revealed it to be a metallocene, with
a co-planar arrangement of cyclopentadienyl ligands.
The structure of 4 is isomorphous with that of the
ferrocene analogue Fe{η-C5H4CH(CH2)4NMe}2.15
The molecular structure of 4 shows a C5 semi-eclipsed
ring configuration with an average C-M-M-C dihe-
dral angle of 19°. The amino-functionalized pendant
arms are well separated by ∼165°, probably to minimize
(15) Bradley, S.; McGowan, P. C.; Oughton, K. A.; Thornton-Pett,
M.; Walsh, M. E. Chem. Commun. 1999, 77-79.
(16) McGowan, P. C.; Hart, C. E.; Donnadieu, B.; Poilblanc, R. J .
Organomet. Chem. 1997, 528, 191-194.
(17) Philippopoulous, A. I.; Hadjiliadis, N.; McGowan, P. C.; Hart,
C. E.; Donnadieu, B.; Poilblanc, R. Inorg. Chem. 1997, 18422-1849.
(18) Corradi, M. M.; McGowan, M. A. D.; McGowan, P. C.; Thornton-
Pett, M., in press.
(19) McGowan, M. A. D.; McGowan, P. C. Inorg. Chem. Commun.
2000, 337-341.
(20) McGowan, M. A. D.; McGowan, P. C. International Patent WO
01/42260, 2001.
(21) Bradley, S.; Camm, K. D.; Furtado, S. J .; McGowan, P. C.;
Mumtaz, R.; Thornton-Pett, M., in press.
(22) Bradley, S.; Camm, K.; Liu, X.; McGowan, P. C.; Mumtaz, R.;
Oughton, K. A.; Podesta, T. J .; Thornton-Pett, M.; Walsh, M. E. Inorg.
Chem. 2002, 41, 715-726.
(23) J utzi, P.; Redeker, T.; Neumann, B.; Stammler, H. G. Organo-
metallics 1996, 15, 4153-4161.
(24) Bouma, R. J .; Teuben, J . H.; Beukema, W. R.; Bansemer, R.
L.; Huffman, J . C.; Caulton, K. G. Inorg. Chem. 1984, 23, 2715-2718.
(25) Floriani, C.; Mange, V. Inorganic Syntheses; J ohn Wiley and
Sons: 1990; Vol. 28.
(26) Belot, J . A.; McCullough, R. D.; Rheingold, A. L.; Yap, G. P. A.
Organometallics 1996, 15, 5062-5065.
(27) Enders, M.; Ko¨hler, K.; Frosch, W.; Pritzkow, H.; Lang, H. J .
Organomet. Chem. 1997, 538, 163-170.

Amino-Functionalized Vanadium Complexes
Organometallics, Vol. 21, No. 16, 2002 3445
F igu r e 2. Molecular structure of compound 5, with 50%
probability thermal ellipsoids.
F igu r e 1. Molecular structure of compound 4, with 50%
probability thermal ellipsoids.
Ta ble 2. Selected In ter a tom ic Dista n ces (Å) a n d
An gles betw een In ter a tom ic Vector s (d eg) of 5
w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th esesa
a crystallographic center of symmetry. The V-Cpcent
bond lengths are slightly elongated with respect to the
unsubstituted vanadocene (1.925 vs 1.915 Å), but to a
lesser extent than 4, which helps explain the fact that
there is no evidence of apparent ring slippage.
V(1)-C(1)
V(1)-C(2)
V(1)-C(3)
V(1)-C(4)
V(1)-C(5)
2.281(3)
2.265(3)
2.255(3)
2.273(3)
2.271(3)
C(1)-C(2)
1.415(4)
1.424(4)
1.399(5)
1.409(4)
1.413(4)
1.93
C(2)-C(3)
C(3)-C(4)
The first reported bis-cyclopentadienyl vanadium(III)
chloride was synthesized by the addition of 3 equiv of
NaC5H5 to VCl4.30 The product was prepared in 23%
yield and was characterized by elemental analysis. The
addition of organic halides, e.g., benzyl chloride, to
vanadocene also yields bis-cyclopentadienyl vanadium-
(III) chloride.31 The yield of vanadocene monochloride
was increased to >70% by conproportionation of V(η-
C(4)-C(5)
C(5)-C(1)
V(1)-Cp(cent)(1)
average C-C
1.41
C(1)-C(2)-C(3) 108.3(3) Cp(cent)-V(1)-Cp(cent) 180
C(2)-C(3)-C(4) 107.9(3) C(6)-C(1)-Cp(cent)
C(3)-C(4)-C(5) 107.8(3)
178.5
C(4)-C(5)-C(1) 109.2(3)
31
C(5)-C(1)-C(2) 106.7(3)
C5H5)2 and V(η-C5H5)2Cl2 and then to >90% by reac-
a
tion of VCl3 with TlC5H5. More recently PbCl2 has been
used to generate V(η-C5H5)2Cl and V(η-C5Me5)2Cl when
reacted with V(η-C5H5)2 or V(η-C5Me5)2, respectively.
Other oxidizing agents used to prepare V(η-C5Me5)2Cl
include HCl32 and benzyl chloride.33 Ring-alkylated
vanadocene monochlorides have also been prepared by
addition of PCl3 to the appropriate vanadocene; this
method has been used to prepare Me-, Pri-, and But-
substituted cyclopentadienyl complexes.26 PCl3 may also
be used to synthesize vanadocene dichloride34 and ring-
alkylated V derivatives as shown.26 Oxidation of V{η-
C5H4CH(CH2)4NMe}2 (4) and V{η-C5H4(CH2)2N(CH2)5}2
(5) with PCl3 afforded the corresponding vanadocene
monochlorides (Scheme 2). Complexes 4 and 5 were
used, since they are crystalline solids that can be
handled more easily than 1-3 and 6. V{η-C5H4CH-
(CH2)4NMe}2Cl (7) and V{η-C5H4(CH2)2N(CH2)5}2Cl (8)-
were synthesized by the addition of 1 equiv of PCl3 to 4
and 5 at room temperature, with stirring in a minimal
volume of petroleum ether (bp 40-60 °C). On addition
of PCl3 to the violet vanadocene solution, a green
precipitate was observed immediately with concomitant
formation of a bright blue solution. Recrystallization
from petroleum ether (bp 40-60 °C) afforded compounds
7 and 8 as blue crystalline platelets in 60% yield. The
products were characterized by X-ray crystal structure
Cp(cent)(1) and Cp(cent)(2) denote centroids of the rings C(1)-
C(5) and C(12)-C(16), respectively.
steric crowding, and as expected, the presence of steri-
cally demanding piperidinyl side chains results in
lengthening of the V-Cpcent bond distance (1.95 Å
compared to 1.91 Å for vanadocene28 and 1.96 Å for
decaphenyl vanadocene29).
A noteworthy feature of the structure is the relatively
short bond length of C(3)-C(4) coupled with a relative
lengthening of V(2)-C(3), with respect to the other V-C
bonds of the C(1)-C(5) ring. This could indicate a
contribution from olefinic bonding within the cyclopen-
tadienyl ring C(3)-C(4) and η3 allylic bonding to the
vanadium center from C(1), C(2), and C(5). The effect
is mirrored in the other C5 ring with olefinic bonding
between C(8)-C(9) and η3 allylic bonding to the vana-
dium center from C(6), C(7), and C(10). Recrystallization
of V{η-C5H4(CH2)2N(CH2)5}2 from diethyl ether afforded
crystals of a quality suitable for X-ray structure analy-
sis. The molecular structure of 5 is shown in Figure 2
and reveals a coplanar ligand arrangement similar to
that seen for 4. 5 possesses a crystallographic center of
symmetry and thus a staggered conformation of C5 rings
(Table 2 shows selected bond lengths and selected bond
angles). V{η-C5H4(CH2)2N(CH2)5}2, like compound 4, is
isomorphous with the corresponding ferrocene Fe{η-
C5H4(CH2)2N(CH2)5}2.22 The molecular structure of 5
shows a Cpcent-V- Cpcent angle of 180° and maximum
separation of the pendant arms (180°), consistent with
1
analysis, elemental analysis, and H NMR spectroscopy.
(30) Fischer, E. O.; Vigourex, S.; Kuzel, P. Chem. Ber. 1960, 93, 701.
(31) de Liefde Meijer, H. J .; J anssen, M. J .; van der Kerk, G. J . M.
Rec. Trav. Chim. 1961, 80, 831.
(32) Curtis, C. J .; Smart, J . C.; Robbins, J . L. Organometallics 1985,
4, 1283-1286.
(28) Antipin, M. Y.; Lobkovskii, E. B.; Semenenko, K. N.; Solove-
ichik, G. L.; Struchkov, Y. T. Zh. Struckt. Khim. 1979, 20, 942.
(29) Castellani, M. P.; Geib, S. J .; Rheingold, A. L.; Trogler, W. C.
Organometallics 1987, 6, 1703-1712.
(33) Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. Inorg.
Chem. 1984, 23, 1739-1747.
(34) Leigh, G. J .; Sanders, J . R. Polyhedron 1989, 8, 1782-1783.

3446 Organometallics, Vol. 21, No. 16, 2002
Bradley et al.
Sch em e 2a
a
(i) 1 equiv PCl3, (ii) excess PCl3.
Ta ble 3. Selected In ter a tom ic Dista n ces (Å) a n d
An gles betw een In ter a tom ic Vector s (d eg) of 9
w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th esesa
These are the first examples of bis-cyclopentadienyl
vanadium(III) chlorides with an amino-functionalized
side chain.
1
The H NMR spectra (300.1 MHz) of 7 (C6D6) and 8
V-C(1)
2.350(3)
2.289(3)
2.265(3)
2.276(3)
2.315(3)
2.336(3)
2.301(3)
2.276(3)
2.289(3)
2.302(3)
1.963
C(1)-C(2)
1.425(4)
1.398(5)
1.415(5)
1.413(5)
1.408(4)
1.410(4)
1.420(5)
1.400(5)
1.405(5)
1.427(4)
V-C(2)
C(2)-C(3)
(CD3CN) were recorded at room temperature. As would
be expected for the paramagnetic complexes 7 and 8,
the cyclopentadienyl ring protons are shifted downfield
to give two very broad signals at δ ∼150 and ∼130. A
second peak at δ ∼40 was assigned to the protons closest
to the C5 rings. Both the downfield shift and broadening
of the resonances lessen on moving away from the
vanadium center. The remaining resonances were as-
signed on this basis as well as with reference to their
integral values and the 1H NMR spectrum of the parent
sodium salts NaC5H4CH(CH2)4NMe and NaC5H4(CH2)2N-
(CH2)5. The molecular structures of 7 and 8 revealed a
distorted trigonal planar geometry about the V atom
and are shown in Figures 3a and 3b, respectively.
Selected bond lengths and angles are shown in Tables
3 and 4. Contrastingly 7 exhibits an eclipsed conforma-
tion of the cyclopentadienyl rings, whereas 8 shows a
staggered cyclopentadienyl ring configuration and pos-
sesses a crystallographic center of symmetry. The
pendant arms are also dissimilarly placed with respect
to one another. It can be seen that in 7, where the
cyclopentadienyl rings are almost eclipsed, the pendant
arms are well separated, whereas in 8 the pendant arms
are positioned almost above one another, directly above
and below the chlorine atom, which is arguably a less
effective conformer in minimizing steric crowding. One
possible explanation for this is the presence of close H‚
‚‚Cl contacts affording intramolecular C-H‚‚‚Cl hydro-
gen bonding in both complexes. Compound 7 features
H‚‚‚Cl distances of 2.66 and 2.83 Å, whereas the closest
H‚‚‚Cl distances in 8 are 2.61 Å (Figure 4a and 4b).
V-C(3)
C(3)-C(4)
V-C(4)
C(4)-C(5)
V-C(5)
C(1)-C(5)
V-C(12)
V-C(13)
V-C(14)
V-C(15)
V-C(16)
V-Cp(cent)(1)
V-Cp(cent)(2)
V-Cl(1)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15)-C(16)
C(12)-C(16)
1.961
2.3840(10)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(1)
C(5)-C(1)-C(2)
109.0(3) Cp(cent)(1)-V(1)-Cl(1)
107.6(3) Cp(cent)(2)-V(1)-Cl(1)
108.9
108.2
107.9(3) Cp(cent)(1)-V(1)-Cp(cent)(2) 142.9
108.6(3)
106.8(3)
C(12)-C(13)-C(15) 108.2(3)
C(13)-C(14)-C(15) 108.5(3)
C(14)-C(15)-C(16) 107.7(3)
C(15)-C(16)-C(12) 108.9(3)
C(16)-C(12)-C(13) 106.7(3)
a
Cp(cent)(1) and Cp(cent)(2) denote centroids of the rings C(1)-
C(5) and C(12)-C(16), respectively.
These interatomic distances are significantly shorter
than the combined van der Waals radii of hydrogen and
chlorine (1.20 and 1.75 Å, respectively).35
In 7, the two pendant arms are positioned as far apart
as possible without breaking the H‚‚‚Cl contacts (2.66
and 2.83 Å). Close H‚‚‚Cl contacts in 8 are facilitated
by the conformation of the pendant arms, directly above
and below the chlorine atom. 7 cannot, however, achieve
(35) Bondi, A. J . Phys. Chem. 1964, 68, 441-451.

Amino-Functionalized Vanadium Complexes
Organometallics, Vol. 21, No. 16, 2002 3447
Ta ble 4. Selected In ter a tom ic Dista n ces (Å) a n d
An gles betw een In ter a tom ic Vector s (d eg) of 10
w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th esesa
V-C(1)
2.390(3)
2.322(3)
2.262(3)
2.260(3)
2.328(3)
1.414(5)
1.406(5)
1.411(5)
1.419(5)
1.404(5)
V-Cp(cent)(1)
V-Cl(1)
1.978
2.390(3)
V-C(2)
V-C(3)
V-C(4)
V-C(5)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(1)-C(5)
C(1)-C(2)-C(3) 108.5(3) Cp(cent)(1)-V(1)-Cl(1)
109.6
C(2)-C(2)-C(4) 108.0(3) Cp(cent)(1)-V(1)-Cp(cent)(1)′ 140.9
C(3)-C(4)-C(5) 107.5(3)
C(1)-C(5)-C(4) 108.4(3)
C(5)-C(1)-C(2) 107.5(3)
a
Cp(cent)(1) denotes the centroid of the ring C(1)-C(5).
this “above and below” configuration, since in the
absence of the ethyl bridge between the cyclopentadienyl
and piperidinyl rings the two carbons of the arm would
be forced into the chlorine atom.
The existence of both inter- and intramolecular
hydrogen bonding of C-H donor units where chlorine
acts as the acceptor atom has been reported previ-
ously.36,37 It is difficult to compare this bonding situation
with vanadocene monochlorides due to the few examples
of such compounds. But, comparisons can be made with
vanadocene dichlorides containing monoalkylated cy-
clopentadienyl ligands that have the substituents di-
rectly above and below the chlorine atoms when the
alkyl group is Pri (cf. 8), whereas in the more rigid and
sterically demanding But-substituted complex the con-
formation of the cyclopentadienyl rings enables the alkyl
groups to move farther apart.26 The H‚‚‚Cl contacts for
these complexes are 2.84 and 2.70 Å, respectively.26
Bis-cyclopentadienyl vanadium(IV) chlorides with
amino-functionalized side chains have not been previ-
ously reported. To prepare the amino-substituted va-
nadocene dichlorides 9 and 10 (Scheme 2), the corre-
sponding vanadocenes 4 and 5 were dissolved in THF
and 2 equiv of PCl3 was added via syringe at room
temperature. This afforded a green precipitate, with a
blue solution, presumed to be the corresponding vana-
docene(III) monochloride. The blue color dissipated very
quickly, forming a green solid in high yield (80-90%).
The vanadocene dichloride derivatives V{η-C5H4CH-
(CH2)4NMe}2Cl2 (9) and V{η-C5H4(CH2)2N(CH2)5}2Cl2
(10) were characterized by EPR spectroscopy. For each
complex the spectra collected at room temperature in
CHCl3 showed the expected eight-line nuclear hyperfine
coupling, characteristic of the d1 vanadium nucleus
where I ) 7/2. Furthermore, the signals for 9 and 10
were centered at g ) 2.06. Each showed an average a
value of 73.3 G. This is typical for bis-cyclopentadienyl
vanadium(II) chlorides and is consistent with values of
g ) 2.00 and a )75 G measured for V(η-C5H4R)2Cl2 (R
) Me, Pri, But).26 There were solubility problems for
these compounds to the extent that it was difficult to
obtain consistent microanalyses or single crystals.
F igu r e 3. (a) Molecular structure of compound 7, with
50% probability thermal ellipsoids. (b) Molecular structure
of compound 8, with 50% probability thermal ellipsoids.
We were interested in comparing the structures and
reactivity of “piano-stool” amino-functionalized mono-
cyclopentadienyl complexes with the amino-functional-
ized vanadocene chlorides. A convenient starting ma-
terial is V(PR3)2Cl3 (R ) Me, Et),11 which is readily
prepared by addition of phosphine to VCl3‚3thf. V(PR3)2-
Cl3 can be used in situ to give V(η-C5H5)Cl2(PR3)2 by
addition of MCp (M ) Na, Tl, SnBun3, 0.5 Mg).11 This
strategy has been used to synthesize ring-alkylated half-
sandwich vanadium complexes38 and amido-function-
alized monocyclopentadienyl vanadium derivatives.9
Using the salt metathesis route described above, a series
(36) Chan, M. C. W.; Cole, J . M.; Gibson, V. C.; Howard, J . A. K.
Acta Crystallogr. C 1997, 53, 202-204.
(37) Spaniel, T.; Go¨rls, H.; Scholz, J . Angew. Chem., Int. Ed. 1998,
37, 1862-1865.
(38) Bo¨ttcher, C.; Schmidt, H.; Rehder, D. J . Organomet. Chem.
1999, 580, 72-76.

3448 Organometallics, Vol. 21, No. 16, 2002
Bradley et al.
in Table 6). The most noteworthy feature exhibited by
the molecular structure of 14 is a close H‚‚‚Cl contact
of 2.66 Å. This could help account for the piperidinyl
ring orientating itself toward one phosphine ligand and
not centrally between them, which would potentially be
favored for steric reasons. 13 and 14 represent the first
X-ray crystal structures of monocyclopentadienyl vana-
dium complexes with an amino-functionalized side chain
that does not coordinate intramolecularly to the metal
center.
1H NMR spectra (CDCl3, 300.1 MHz, 300 K) were
collected for compounds 12 and 13. It was expected that
the cyclopentadienyl protons would be observed at δ
∼150, i.e., similar to those of the bis-cyclopentadienyl
vanadium(III) complexes. No cyclopentadienyl reso-
nances were observed in the range δ 400 downfield to
200 upfield. This is probably due to unfavorable electron
spin relaxation rates, as was reportedly found for V(η-
C5H5)(PMe3)2Cl2 and V(η-C5H4Me)(PMe3)2Cl2.11 The
phosphine resonances are readily observed in the region
δ -15 to -25 and are similar to those found for V(η-
C5H5)(PMe3)2Cl2 and V(η-C5H4Me)(PMe3)2Cl2.11
P olym er iza tion Stu d ies. Industrial production of
polybutadiene is based upon homogeneous catalysis
using metal complex catalysts of Ti, Co, Ni, or Nd.
However the use of both heterogeneous and homoge-
neous vanadium compounds to catalyze the stereose-
lective polymerization of butadiene is also known.39
Heterogeneous systems based on vanadium(III) and
-(IV) chlorides and homogeneous systems such as V(a-
cac)3 give polymers with a 1,4-trans microstructure.40,41
More recently V(η-C5H5)2Cl and V(η-C5H4Me)(PEt3)2Cl2
were found to effectively catalyze the polymerization of
butadiene to give 1,4-cis-polybutadiene.14
The analogous amino-functionalized vanadium(III)
cyclopentadienyl complexes were investigated for po-
tential catalytic activity toward the polymerization of
butadiene. It was hoped to establish the activity and
stereoselectivity of the catalysts. Furthermore any effect
of the pendant amino functionality upon the perfor-
mance of the catalyst could be observed. It should be
emphasized that the catalytic trials to be presented were
carried out under nonoptimized conditions.
Therefore, trial polymerizations of butadiene were
carried out using V{η-C5H4CH(CH2)4NMe}2Cl, 7, V{η-
C5H4(CH2)2N(CH2)5}2Cl, 8, V{η-C5H4(CH2)2NMe2}-
{PMe3}2Cl2, 11, V{η-C5H4(CH2)3NMe2}{PMe3}2Cl2, 12,
V{η-C5H4CH(CH2)4NMe}{PMe3}2Cl2, 13, and V{η-C5H4-
(CH2)2N(CH2)5}{PMe3}2Cl2, 14, in single polymerization
runs. These trials were all conducted in analogous
fashion under nitrogen using normal Schlenk line
techniques. In each run MAO was used as a cocatalyst
in a ratio of 100:1 with respect to the catalyst. Butadiene
was used as a 1.8 M solution in toluene. In the instance
where 7 or 8 was used as catalyst, MAO was added to
the butadiene solution. The catalyst was added as a
bright blue toluene solution, and an immediate color
change to orange-brown was observed. After stirring for
F igu r e 4. (a) Representation of the C-H‚‚‚Cl hydrogen
bonding in 7. (b) Representation of the C-H‚‚‚Cl hydrogen
bonding in 8.
of novel pendant arm half-sandwich complexes have
been synthesized. For example, V{η-C5H4CH(CH2)4-
NMe}Cl2(PMe3)2 (13) is prepared by reaction of NaC5H4-
CH(CH2)4NMe with V(PMe3)2Cl3 (Scheme 3). This re-
action worked better when the V(PMe3)2Cl3 was used
in situ. After stirring overnight the solvent was removed
under reduced pressure and the product washed with
petroleum ether, affording 13 as a purple crystalline
solid. Analogous reactions were performed with the
corresponding sodium salts afforded V{η-C5H4(CH2)2-
NMe2}(PMe3)2Cl2 (11) and V{η-C5H4(CH2)3NMe2}(PMe3)2-
Cl2 (12) as oils and V{η-C5H4(CH2)2N(CH2)5}(PMe3)2Cl2
(14) as a solid. Compounds 11 and 12 were character-
ized by 1H NMR spectroscopy, and 13 and 14 were
1
characterized by H NMR spectroscopy, X-ray crystal
structure analysis, and microanalysis. The molecular
structure of 13 (Figure 5) revealed a square-pyramidal
piano-stool geometry about the V center. Selected bond
lengths and angles are shown in Table 5. The molecular
structure and geometry of 13 are comparable to V(η-
C5H5)(PMe3)2Cl2,11 but the presence of the piperidinyl
side chain eliminates the mirror plane bisecting the
chlorine atoms through the vanadium and one carbon
of the cyclopentadienyl ring. The molecular structure
of 14 was found to be monomeric with a square-
pyramidal piano-stool geometry about V and is shown
in Figure 6 (selected bond lengths and angles are shown
(39) Porri, L.; Giarruso, A. In Comprehensive Polymer Science;
Eastmond, C. C., Ledwith, A., Russo, S., Sigwalt, B., Eds.; Pergamon:
Oxford, 1989; Vol. 4, pp 53-108.
(40) Ricci, G.; Italia, S.; Comitani, C.; Porri, L. Polym. Commun.
1991, 32, 513.
(41) Ricci, G.; Italia, S.; Porri, I. Macromol. Chem. Phys. 1994, 195,
1389.

Amino-Functionalized Vanadium Complexes
Organometallics, Vol. 21, No. 16, 2002 3449
Sch em e 3a
a
(i) toluene.
Ta ble 5. Selected In ter a tom ic Dista n ces (Å) a n d
An gles betw een In ter a tom ic Vector s (d eg) of 13
w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th esesa
Ta ble 6. Selected In ter a tom ic Dista n ces (Å) a n d
An gles betw een In ter a tom ic Vector s (d eg) of 14
w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th esesa
V(1)-C(1)
V(1)-C(2)
V(1)-C(3)
V(1)-C(4)
V(1)-C(5)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(1)
2.334(2)
2.274(2)
2.281(2)
2.322(2)
2.381(2)
1.428(3)
1.403(3)
1.412(3)
1.420(3)
1.414(3)
V(1)-P(1)
2.5263(6)
2.5141(6)
2.4103(6)
2.3990(6)
1.98
2.32
1.415
1.82
V(1)-C(1)
V(1)-C(2)
V(1)-C(3)
V(1)-C(4)
V(1)-C(5)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(1)
2.362(3)
2.297(4)
2.274(4)
2.281(4)
2.323(3)
1.399(5)
1.391(6)
1.395(6)
1.418(5)
1.400(5)
V(1)-P(2)
2.5102(10)
2.5096(10)
2.3992(9)
2.4037(10)
1.98
2.31
1.4
1.8
V(1)-P(2)
V(1)-P(3)
V(1)-Cl(1)
V(1)-Cl(2)
V(1)-Cp(cent)(1)
average V-C
average C-C
average P-C
V(1)-Cl(1)
V(1)-Cl(2)
V(1)-Cp(cent)(1)
average V-C
average C-C
average P-C
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(1)
C(5)-C(1)-C(2)
average C-C-C
108.0(2)
107.68(19) Cl(1)-V(1)-Cl(2)
109.3(2)
106.63(19) Cl(2)-V(1)-Cp(cent)(1) 117.2
108.43(19) P(1)-V(1)-Cp(cent)(1) 112.5
108
P(1)-V(1)-P(2)
133.39(2)
124.63(2)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(1)
C(5)-C(1)-C(2)
average C-C-C
110.0(4) P(2)-V(1)-P(3)
107.6(3) Cl(1)-V(1)-Cl(2)
135.57(4)
121.84(5)
Cl(1)-V(1)-Cp(cent)(1) 118.1
107.3(4) Cl(1)-V(1)-Cp(cent)(1) 119.6
108.9(4) Cl(2)-V(1)-Cp(cent)(1) 118.6
106.2(4) P(2)-V(1)-Cp(cent)(1) 112.2
P(2)-V(1)-Cp(cent)(1) 114.1
108
P(3)-V(1)-Cp(cent)(1) 112.2
C(6)-C(5)-Cp(cent)(1) 176.1
C(11)-C(1)-Cp(cent)(1) 179.6
a
a
Cp(cent)(1) denotes the centroid of the ring C(1)-C(5).
Cp(cent)(1) denotes the centroid of the rings C(1)-C(5).
F igu r e 6. Molecular structure of compound 14, with 50%
probability thermal ellipsoids.
F igu r e 5. Molecular structure of compound 13, with 50%
probability thermal ellipsoids.
cal shifts in the H and 13C NMR spectra of the three
1
stereoregular polymers have been determined.40,42,43 The
stereochemistry of the resultant polymers was investi-
20 min at room temperature the solution had become
orange-green with a small amount of white precipitate.
After 1 h the reaction was quenched with methanol. HCl
was added to dissolve inorganic aluminum salts, and
any solid polymer was collected by filtration. The
polymerization mixture was extracted with toluene, and
the solvent was removed under reduced pressure, af-
fording the polymer. Where the vanadium(III) monocy-
clopentadienyl complexes 11, 12, 13, and 14 were used
as catalysts, the polymerization was carried out in a
fashion similar to that described above. In each case the
catalyst was added as a purple solution in toluene and
an immediate color change to red was observed when
each solution was injected into the butadiene/MAO
mixture. The polymer was collected as before.
1
gated by H and 13C{1H} NMR spectroscopy. The bis-
cyclopentadienyl vanadium(III) chloride derivatives 7
and 8 gave percentages of conversion of butadiene of
10% and 2%, respectively, which compare favorably with
similar complexes found in the literature; V(η-C5H5)2-
Cl is reported to polymerize butadiene with 8% conver-
sion.14 The reported cis-1,4-:trans-1:4-:1,2- stereoselec-
tivity of the vanadocene chloride (87.2:1.1:11.7)14 is
comparable to that found for compounds 7 and 8 (91:
0:9 and 89:0:11, respectively). Percentages of the dif-
ferent polybutadiene microstructures are shown in
Table 7.
(42) Seeman, J . I. Chem. Rev. 1983, 83, 83.
(43) Taube, R.; Windisch, H.; Maiwald, S. Macromol. Symp. 1995,
89, 393.
The three types of polymer produced are cis-1,4-,
trans-1:4-, and 1,2-polybutadiene. The expected chemi-

3450 Organometallics, Vol. 21, No. 16, 2002
Bradley et al.
Ta ble 7. Ra tios of P olybu ta d ien e Obta in ed via
Va n a d iu m (III) Com p lex Ca ta lysts
Ta ble 8. Selected In ter a tom ic Dista n ces (Å) a n d
An gles betw een In ter a tom ic Vector s (d eg) of 15
w ith Estim a ted Sta n d a r d Devia tion s in
P a r en th esesa
catalyst
cis-1,4-
trans-1,4-
1,2-
V(ηC5H5)2Cl2
87
91
89
82
27
37
41
21
1
0
0
12
9
11
16
4
18
0
17
C(1)-Cr(1)
C(2)-Cr(1)
C(3)-Cr(1)
C(4)-Cr(1)
C(5)-Cr(1)
C(1)-C(2)
C(2)-C(3)
C(3)-C(4)
2.2024(16)
2.2095(17)
2.2494(18)
2.2531(18)
2.2124(17)
1.419(3)
C(4)-C(5)
1.422(3)
1.423(2)
2.1493(14)
2.3084(5)
2.2988(4)
1.486(2)
1.98
7
C(1)-C(5)
8
N(9)-Cr(1)
Cl(1)-Cr(1)
Cl(2)-Cr(1)
C(9)-N(9)
V(ηC5H4Me)(PEt3)2Cl2
2
11
12
13
14
59
45
59
62
1.415(3)
1.397(3)
Cr(1)-Cp(cent)(1)
C(3)-C(2)-C(1)
C(4)-C(3)-C(2)
C(3)-C(4)-C(5)
C(4)-C(5)-C(1)
C(2)-C(1)-C(5)
C(5)-C(1)-C(6)
C(2)-C(1)-C(6)
C(1)-C(6)-C(11)
C(1)-C(6)-C(7)
C(11)-C(6)-C(7)
C(6)-C(7)-C(8)
108.22(17) C(6)-C(11)-C(10) 111.75(15)
108.44(17) N(9)-C(8)-C(7) 113.64(14)
108.14(17) N(9)-C(10)-C(11) 113.80(15)
107.97(17) C(8)-N(9)-C(10) 109.35(14)
107.22(16) C(9)-N(9)-C(10) 107.47(14)
The monofunctionalized monocyclopentadienyl com-
plexes 11-14 show relatively low conversions as well
(conversion 3-11%). Interestingly however, 11-14 gave
results quite unlike those reported for a similar complex
without the pendant arm; V(η-C5H4Me)(PEt3)2Cl2 gives
a high cis:trans ratio (82.4:2.1),14 whereas compounds
11-14, favor a trans-1,4-stereochemistry.
It has been suggested that the stereospecificity of
these types of catalysts is based on the cis vs trans mode
of monomer coordination and the rate of isomerization
of the anti vs syn butenyl, relative to the rate of
insertion. In the V(acac)3 system the fast rate of isomer-
ization of the butenyl group is the determining factor;
hence a trans polymer conformation is favored. The high
cis stereoselectivity of V(η-C5H5)2Cl and V(η-C5H4Me)-
(PEt3)2Cl2 is reportedly due to the isomerization rate of
the butenyl group being slower than monomer coordina-
tion, for which a cis configuration is favored.14 For each
of the catalysts used it would be expected that the action
of the MAO would be to generate a cationic active
species. It has been proposed in the half-sandwich
complex a cationic methyl intermediate is likely, which
would result in a 14-electron compound.14
126.17(17) C(9)-N(9)-C(8)
107.69(13)
126.21(17) Cl(2)-Cr(1)-Cl(1) 98.968(17)
111.74(15) N(9)-Cr(1)-Cl(2)
111.46(15) N(9)-Cr(1)-Cl(1)
95.73(4)
95.64(4)
108.01(17) C(8)-N(9)-Cr(1) 112.37(11)
112.00(15) C(9)-N(9)-Cr(1) 109.86(10)
C(10)-N(9)-Cr(1) 109.95(11)
Cl(1)-Cr(1)-Cp(cent)(1) 123.25
Cl(2)-Cr(1)-Cp(cent)(1) 121.43
N(9)-Cr(1)-Cp(cent)(1) 115.80
a
Cp(cent)(1) denotes the centroid of the ring C(1)-C(5).
Subsequently, the most probable explanation for the
observed stereoselectivity in the catalysts presented
here is the differing electronic configuration of the active
species and the influence of the pendant arm thereupon.
It is suggested that the pendant arm might promote
trans η2 coordination of butadiene in the half-sandwich
complexes in one or both of two ways; the pendant arm
could sterically hinder cis η4 coordination of butadiene,
promoting trans η2 coordination. Alternatively the trans
selectivity of the monocyclopentadienyl complexes could
be due to η2 coordination of the butadiene monomer
being promoted by intramolecular coordination of the
pendant arm amino group.
The vanadocene monochloride catalysts 7 and 8
produced no trans-1,4-polymer, regardless of the steric
bulk of the pendant arm and the potential for intramo-
lecular amino coordination. It is suggested that the very
electron-deficient 12-electron active species favors η4
butadiene coordination, resulting in a cis coordination
and. accordingly, a cis polymer. As described, the amino-
functionalized cyclopentadienyl ligand has an effect on
the catalytic behavior of a vanadium system. One of the
aspects that interested us regarding these ligand sys-
tems was to examine the effects of flexibility of the
pendent arm and the electron-donating ability of the
nitrogen atom on another catalytic system. A suitable
system to compare the ability to form an intramolecular
dative covalent bond was the half-sandwich mono-
functionalized cyclopentadienyl chromium systems of
J olly.12,13 These (in conjunction with MAO) have been
shown to be remarkably active ethene polymerization
F igu r e 7. Molecular structure of compound 15, with 50%
probability thermal ellipsoids.
catalysts. Therefore η-C5H4{CH(CH2)4NCH3}CrCl2 (15)
and η-C5H4{CH2C5H4N}CrCl2 (16) were synthesized.
Polymerization experiments were carried out as de-
scribed in the Experimental Section. The (nonoptimized)
polymerization data are shown in the Experimental
Section. The two compounds have very similar activity,
and a crystal structure of 15 (Figure 7, and selected
bond lengths and angles are shown in Table 8) may help
to explain why this is the case, since the pendant amino
arm is bound to the chromium center. Therefore we
found that the differences in the flexibility of the arm
have no effect on the catalytic rate.
Con clu sion
Having synthesized a number of new vanadium(II),
vanadium(III), and vanadium(IV) compounds, we iso-
lated and crystallized the first examples of amino-
functionalized vanadocenes and vanadocene monochlo-
rides. A series of amino-functionalized cyclopentadienyl
vanadium phosphine chloride complexes were also
synthesized, and their catalytic behavior toward the

Amino-Functionalized Vanadium Complexes
Organometallics, Vol. 21, No. 16, 2002 3451
as a bright purple crystalline solid (1.3 g, 0.003 mol, 54% based
on vanadium). Anal. Found: C 67.9; H 8.3; N 7.1. VC22H32N2
requires: C 70.4; H 8.6; N 7.5. H NMR (CDCl3, 300.1 MHz,
300 K): δ 337 (br s, 8H, ∆ω1/2 ) 11 000 Hz), 55 (br s, 2H, ∆ω1/2
) 1300 Hz), 11 (br m, 4H, ∆ω1/2 ) 110 Hz), 8.5 (br m, 4H,
∆ω1/2 ) 100 Hz), 3 (br m, 8H, ∆ω1/2 ) 580 Hz), 3 (br s, 6H,
∆ω1/2 ) 50 Hz).
V{η-C5H4(CH2)2N(CH2)5}2, 5. To a Schlenk tube charged
with NaC5H4(CH2)2N(CH2)5 (5.1 g, 0.023 mol) and THF (150
mL) and cooled to -78 °C was added [(V2Cl3)(thf)6]2[Zn2Cl6]
(5.2 g, 0.003 mol) with stirring. The reaction mixture was
worked up in the same way as 4 to give a bright purple
crystalline solid (3.4 g, 0.008 mol, 66% based on vanadium).
Anal. Found: C 69.5; H 9.1; N 6.75. VC24H36N2 requires: C
71.4; H 9.0; N 6.9. 1H NMR (CDCl3, 300.1 MHz, 300 K): δ 337
(br s, 8H, ∆ω1/2 ) 10 500 Hz), 77 (br s, 4H, ∆ω1/2 ) 1800 Hz),
3 (br s, 4H, ∆ω1/2 ) 120 Hz), 1.7 (br m, 8H, ∆ω1/2 ) 70 Hz), 1.5
(br m, 12H, ∆ω1/2 ) 80 Hz).
polymerization of butadiene was examined. It was found
that the amino-functionalized cyclopentadienyl vana-
dium phosphine chloride complexes behaved much
differently from their nonfunctionalized cyclopentadi-
enyl counterparts.
1
Exp er im en ta l Deta ils
Unless otherwise stated all manipulations were conducted
using standard Schlenk-line techniques, under an inert atmo-
sphere of dinitrogen or argon, using a modified dual vacuum/
dinitrogen (or argon) line or in a Braun Labmaster 100
glovebox under an atmosphere of dinitrogen. Diethyl ether,
petroleum ether (bp 40-60 °C), THF, and toluene were
predried with Na metal and distilled over Na or Na/benzophe-
none under dinitrogen. CHCl3 and CH3CN were predried and
distilled over CaH under N2. All solvents were subsequently
stored in ampules under N2. PCl3 was degassed using freeze-
pump-thaw cycles and dried over 4 Å molecular sieves prior
to use.
Cr yst a llogr a p h ic Da t a Collect ion a n d St r u ct u r e
Solu tion . X-r a y Cr ysta llogr a p h y. Data for compounds 4,
5, 9, 10, and 13-15 were collected on a Nonius KappaCCD
area-detector diffractometer using graphite-monochromated
Mo KR radiation (λ ) 0.71073 Å) using 1.0° φ-rotation frames.
Pertinent crystallographic details are given in Table 9.
The structures of all compounds were solved by direct
methods using SHELXS 86. Refinement, by full-matrix least
squares on F2 using SHELXL 97, was similar for all seven
compounds. Hydrogen atoms were constrained to idealized
positions using a riding model (with free rotation for methyl
groups).
V{η-C5H4CH2C5H4N}2, 6. To a Schlenk tube charged with
NaC5H4CH2C5H4N (2.65 g, 0.015 mol) and THF (150 mL) and
cooled to -78 °C was added [(V2Cl3)(thf)6]2[Zn2Cl6] (3.0 g, 0.002
mol) with stirring. The cold bath was removed, and the solution
became purple on warming to room temperature. The reaction
mixture was stirred overnight, the solvent was removed under
reduced pressure, and the product was extracted into THF (100
mL). The solvent was removed under reduced pressure,
1
affording 6 as a bright purple oil (1.5 g, 0.004 mol, 56%). H
NMR (C7D8, 300.1 MHz, 300 K): δ 331 (br s, 8H, ∆ω1/2
)
10 500 Hz), 78 (br s, 4H, ∆ω1/2 ) 1420 Hz), 8 (br m, 2H, ∆ω1/2
) 140 Hz), 7 (br m, 4H, ∆ω1/2 ) 50 Hz), 6.5 (br m, 2H, ∆ω1/2
)
50 Hz).
V{η-C5H4CH(CH2)4NMe}2Cl, 7. To a Schlenk tube charged
with a solution of 4 (0.4 g, 0.001 mol) in petroleum ether (bp
40-60 °C) (20 mL) was added PCl3 (0.1 mL, 0.001 mol) via
syringe with stirring. The solution changed color from purple
to blue with concomitant formation of a green precipitate. The
solvent was immediately removed in vacuo, and the product
was extracted into petroleum ether (bp 40-60 °C). Recrystal-
lization from petroleum ether (bp 40-60 °C) yielded 7 as bright
blue crystalline platelets (0.24 g, 0.0006 mol, 54%). Anal.
Found: C 64.2; H 7.75; N 7.1; Cl 8.25. Required for VC22H32N2-
V{η-C5H4(CH2)2NMe2}2, 1. To a Schlenk tube charged with
NaC5H4(CH2)2NMe2 (0.75 g, 0.005 mol) and THF (150 mL) and
cooled to -78 °C was added [(V2Cl3)(thf)6]2[Zn2Cl6] (0.8 g,
0.0005 mol) with stirring. The cold bath was removed, and the
solution became purple on warming to room temperature. The
reaction mixture was stirred overnight, the solvent was
removed under reduced pressure, and the product was ex-
tracted into diethyl ether (100 mL). Solvent was removed in
vacuo to give 1 as a distillable bright purple oil (∼200 °C, 10-2
1
Cl: C 64.3; H 7.8; N 6.8; Cl 8.6. H NMR (C6D6 CD3CN, 300.1
1
mmHg) (0.6 g, 0.002 mol, 94%, based on vanadium). H NMR
MHz, 300 K): δ 148.86 (br s, 4H, ∆ω1/2 ) 2700 Hz), 128.93 (br
s, 4H, ∆ω1/2 ) 2700 Hz), 40.72 (br s, 2H, ∆ω1/2 ) 900 Hz), 5.77
(br s, 4H), 3.56 (br s, 4H), 2.62 (br s, 3H), 1.89 (br s, 4H), 1.43
(br s, 4H).
V{η-C5H4(CH2)2N(CH2)5}2Cl, 8. To a Schlenk tube charged
with a solution of 5 (1.6 g, 0.004 mol) in petroleum ether (bp
40-60 °C) (20 mL) was added PCl3 (0.4 mL, 0.004 mol) via
syringe with stirring. The reaction mixture was worked up in
the same way as 7 to give 8 as bright blue crystalline platelets
(0.93 g, 0.002 mol, 53%). Anal. Found: C 62.2; H 8.4; N 3.9.
Required for VC24H36N2Cl: C 65.7; H 8.3; N 6.4. 1H NMR (CD3-
CN, 300.1 MHz, 300 K): δ 147.17 (br s, 4H, ∆ω1/2 ) 2500 Hz),
(C6D6, 300.1 MHz, 300 K): δ 345 (br s, 8H, ∆ω1/2 ) 9700 Hz),
79 (br s, 4H, ∆ω1/2 ) 1200 Hz), 2 (br m, 16H, ∆ω1/2 ) 65 Hz).
V{η-C5H4(CH2)3NMe2}2, 2. To a Schlenk tube charged with
NaC5H4(CH2)3NMe2 (4.0 g, 0.023 mol) and THF (150 mL) and
cooled to -78 °C was added [(V2Cl3)(thf)6]2[Zn2Cl6] (4.7 g, 0.003
mol) with stirring. The reaction mixture was worked up in the
same way as 1 to give 2 as a distillable bright purple oil (∼200
°C, 10-2 mmHg) (3.2 g, 0.009 mol, 79% based on vanadium).
1H NMR (C6D6, 300.1 MHz, 300 K): δ 349 (br s, 8H, ∆ω1/2
)
11 000 Hz), 80 (br s, 4H, ∆ω1/2 ) 1600 Hz), 9 (br s, 4H, ∆ω1/2
) 170 Hz), 2 (br m, 16H, ∆ω1/2 ) 90 Hz).
V{η-C5H4(CH2)3NH2}2, 3. To a Schlenk tube charged with
NaC5H4(CH2)3NH2 (2.0 g, 0.013 mol) and THF (150 mL) and
cooled to -78 °C was added [(V2Cl3)(thf)6]2[Zn2Cl6] (2.8 g, 0.002
mol) with stirring. The reaction mixture was worked up in the
same way as 1 to give 3 as a distillable purple oil (∼200 °C,
10-2 mmHg) (1.2 g, 0.004 mol, 59% based on vanadium). 1H
NMR (C7D8, 300.1 MHz, 300 K): δ 8 (br s, 4H, ∆ω1/2 ) 170
Hz), 4 (br m, 4H, ∆ω1/2 ) 250 Hz), 3.3 (br m, 8H, ∆ω1/2 ) 130
Hz).
V{η-C5H4CH(CH2)4NMe}2, 4. To a Schlenk tube charged
with NaC5H4CH(CH2)4NMe (2.4 g, 0.015 mol) and THF (150
mL) and cooled to -78 °C was added [(V2Cl3)(thf)6]2[Zn2Cl6]
(2.6 g, 0.002 mol) with stirring. The cold bath was removed,
and the solution became purple on warming to room temper-
ature. The reaction mixture was stirred overnight, the solvent
was removed under reduced pressure, and the product was
extracted into THF (100 mL). 4 was recrystallized from THF
127.41 (br s, 4H, ∆ω1/2 ) 2500 Hz), 38.33 (br s, 4H, ∆ω1/2 )
600 Hz), 5.87 (br s, 4H), 4.13 (br s, 8H), 1.49 (br s, 12H).
V{η-C5H4CH(CH2)4NMe}2Cl2, 9. To a Schlenk tube charged
with a solution of 4 (0.5 g, 0.0013 mol) in THF (80 mL) was
added PCl3 (1.0 mL, 0.010 mol). The solution rapidly became
colorless from purple through blue, with concomitant formation
of a fluffy green precipitate. The solvent was filtered from the
solid via cannula. Residual THF was removed in vacuo to
afford 9 as a bright green powdery solid. The product was
washed with THF (2 × 30 mL) (0.51 g, 0.0011 mol, 88%). EPR
(CHCl3, 298 K) 8-line hyperfine coupling, g ) 2.06, a ) 73.3
G.
V{η-C5H4(CH2)2N(CH2)5}2Cl2, 10. To a Schlenk tube charged
with a solution of 5 (1.6 g, 0.004 mol) in THF (80 mL) was
added PCl3 (1.0 mL, 0.010 mol). The reaction mixture was
worked up in the same way as 9 to give as a bright green
powder. The product was washed with THF (2 × 30 mL) (1.6

3452 Organometallics, Vol. 21, No. 16, 2002
Bradley et al.

Amino-Functionalized Vanadium Complexes
Organometallics, Vol. 21, No. 16, 2002 3453
g, 0.0034 mol, 84%). EPR (CHCl3, 298K) 8-line hyperfine
coupling, g ) 2.06, a ) 73.3 G.
CrC11H10NCl2: C 46.3; H 5.7; N 4.9. FAB mass spectrum: m/z
285 - C5H4{CH(CH2)2NCH3}CrCl2.
V{η-C5H4(CH2)2NMe2}{P Me3}2Cl2, 11. To a Schlenk tube
charged with V(PMe3)2Cl3 (1.1 g, 0.004 mol) and toluene (80
mL) and cooled to 0 °C was added NaC5H4(CH2)2NMe2 (0.6 g,
0.004 mol) as a suspension in toluene (40 mL) via cannula with
stirring. The color changed immediately to purple, and the
reaction mixture was stirred overnight before removal of the
solvent in vacuo. The bright purple oily solid was washed with
petroleum ether (bp 40-60°) (50 mL) and extracted once with
THF (150 mL). Volatiles were removed in vacuo to give 11 as
Cr {η-C5H4CH2C5H4N}Cl2, 16. To a Schlenk tube charged
with CrCl3 (0.88 g, 0.0056 mol) and THF (100 mL) was added
a suspension of NaC5H4{CH2C5H4N} (1 g, 0.0054 mol) in
THF (100 mL). The mixture was allowed to reflux overnight
to give a deep blue-green solution and precipitate of NaCl. The
solvent was removed in vacuo and the product extracted in
DCM to give a deep blue solution. Removal of the solvent in
vacuo afforded a deep blue powder (0.7 g, 0.0025 mol, 46.4%).
Anal. Found: C 52.3; H 4.2; N 5.2. Calcd for CrC11H10NCl2: C
47.3; H 3.6; N 5.0. FAB mass spectrum: m/z 279 - C5H4-
{CH2C5H4N}2CrCl2.
P olym er iza tion of Bu ta d ien e. Butadiene polymerization
trials were carried out using compounds 7, 8, 12, and 13 as
catalysts. Butadiene was used as a 1.8 M solution in toluene.
For polymerization runs of 7 and 8 50 µmol of catalyst was
used. For polymerization runs of 12 and 13 100 µmol of
catalyst was used. One hundred equivalents of MAO was used
as a cocatalyst for each run as a 10% solution in toluene.
Polymerization trials for all catalysts were carried out under
identical conditions. A typical run is given as an example.
To a Schlenk tube containing a toluene solution of butadiene
(35 mL, 0.063 mol) was added MAO (7 mL, 0.01 mol) via
syringe. V{C5H4CH(CH2)4NMe}(PMe3)2Cl2 (0.044 g, 100 µmol)
was added as a toluene solution (10 mL). The mixture was
stirred vigorously, and after 60 min MeOH was added drop-
wise, then in excess. HCl (80 mL) was added and any polymer
was collected by filtration and dried.
P olym er iza tion of Eth en e. To a solution of MAO (1.7 mL,
100:1 MAO/Cr ratio) in toluene (20 mL) under an ethylene flow
of 1 atm was added 15 (0.007 g, 25 µmol) in toluene (10 mL).
The temperature was maintained at 20 °C and the reaction
allowed to run (20 min). The polymerization was terminated
by addition of MeOH (5 mL) and the reaction mixture added
to MeOH (150 mL). Concentrated HCl was added and the
polymer precipitated out of solution. The resulting polymers
were washed (cHCl/MeOH (3 × 5 mL)) and dried to give white
polyethylene (1.57 g). The same procedure was carried out for
16 to give white polyethylene (1.69 g).
1
a crystalline purple solid (0.73 g, 0.0023 mol, 64%). H NMR
(CDCl3, 300.1 MHz, 300 K): δ -23 (br m, ∆ω1/2 ) 1200 Hz).
V{η-C5H4(CH2)3NMe2}{P Me3}2Cl2, 12. To a Schlenk tube
charged with V(PMe3)2Cl3 (1.1 g, 0.004 mol) and toluene (80
mL) and cooled to 0 °C was added NaC5H4(CH2)3NMe2 (0.6 g,
0.004 mol) as a suspension in toluene (40 mL) via cannula with
stirring. The color changed immediately to purple, and the
reaction mixture was stirred overnight before removal of the
solvent in vacuo. The bright purple oily solid was washed with
petroleum ether (bp 40-60°) (50 mL) and extracted once with
THF (150 mL). Volatiles were removed in vacuo to give 12 as
1
a crystalline purple solid (0.80 g, 0.0024 mol, 68%). H NMR
(CDCl3, 300.1 MHz, 300 K): δ -23 (br m, ∆ω1/2 ) 1200 Hz).
V{η-C5H4CH(CH2)4NMe}{P Me3}2Cl2, 13. To a Schlenk
tube charged with V(PMe3)2Cl3 (1.1 g, 0.004 mol) and toluene
(80 mL) and cooled to 0 °C was added NaC5H4CH(CH2)4NMe
(0.7 g, 0.004 mol) as a suspension in toluene (40 mL) via
cannula with stirring. The color changed immediately to
purple, and the reaction mixture was stirred overnight before
removal of the solvent in vacuo. The bright purple oily solid
was washed with petroleum ether (bp 40-60°) (50 mL) and
extracted into THF (150 mL). Volatiles were removed in vacuo
to give 13 as a crystalline purple solid (0.76 g, 0.0022 mol,
65%). Anal. Found: C 46.9; H 7.9; N 3.1; P 14.1. VC14H43N2P2-
Cl2 requires: C 46.8; H 7.9; N 3.2; P 14.1. 1H NMR (CDCl3,
300.1 MHz, 300 K): δ -23 (br s, ∆ω1/2 ) 1100 Hz).
V{η-C5H4(CH2)2N(CH2)5}{P Me3}2Cl2, 14. To a Schlenk
tube charged with V(PMe3)2Cl3 (1.1 g, 0.004 mol) and toluene
(80 mL) and cooled to 0 °C was added NaC5H4(CH2)2N(CH2)5
(0.7 g, 0.004 mol) as a suspension in toluene (40 mL) via
cannula with stirring. The color changed immediately to
purple, and the reaction mixture was stirred overnight before
removal of the solvent in vacuo. The bright purple oily solid
was washed with petroleum ether (bp 40-60°) (50 mL) and
extracted once with THF (150 mL). Volatiles were removed in
vacuo to give 14 as a crystalline purple solid (0.83 g, 0.0023
mol, 65%). Anal. Found: C 47.8; H 7.8; N 3.1; Cl 15.7.
VC14H43N2P2Cl2 requires: C 48.0; H 8.1; N 3.1; Cl 15.8. 1H
NMR (CDCl3, 300.1 MHz, 300 K): δ -23 (br s, ∆ω1/2 ) 1100
Hz).
P olym er iza tion Activity a n d Ch a r a cter iza tion
catalyst
precursor
amt. of cat.
(µmol)
amt. PE
(g)
activity
(kg PE/mol Cr/h)
15
16
25
25
1.69
1.57
202.8
189.2
The physical properties of the polymers were tested by RAPRA
Technology.
η-C5H4{CH2C5H4N}2Cr Cl2: MW ) 403 000; PD ) 5.9.
η-C5H4{CH(CH2)2NCH3}Cr Cl2: MW ) 642 000; PD ) 9.4.
Cr {η-C5H4CH(CH2)4NCH3}Cl2, 15. To a Schlenk tube
charged with CrCl3 (0.85 g, 0.0054 mol) and THF (100 mL)
was added a suspension of NaC5H4CH(CH2)4NMe (1 g, 0.0054
mol) in THF (100 mL). The mixture was allowed to reflux
overnight to give a deep blue-green solution and precipitate
of NaCl. The solvent was removed in vacuo and the product
extracted in DCM to give a deep blue solution. Removal of the
solvent in vacuo afforded a deep blue powder (0.74 g, 0.0024mol,
43.7%). Anal. Found: C 46.3; H 5.7; N 3.2%. Calcd for
Ack n ow led gm en t. We would like to thank Rapra
Technology Limited, Shropshire, U.K., for characteriza-
tion data for the polyethylene and the EPSRC for
funding.
Su p p or tin g In for m a tion Ava ila ble: This material is
available free of charge via the Internet at http://pubs.acs.org.
OM020170F