Synthesis, structure and ethylene polymerisation behaviour of vanadium(iv and v) complexes bearing chelating aryloxides

Article abstract of DOI:10.1039/b901810g

The reaction of [V(Np-tolyl)Cl₃] with the sulfur-bridged diphenol ligand 2,2′-thiobis(4,6-di-tert-butylphenol), {2,2′-S[4,6-(t-Bu)₂C₆H₂OH]₂} (LSH₂) afforded the complexes [V(LS)₂

Full text of DOI:10.1039/b901810g

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www.rsc.org/dalton | Dalton Transactions
Synthesis, structure and ethylene polymerisation behaviour of
vanadium(IV and V) complexes bearing chelating aryloxides †
Damien Homden,a Carl Redshaw,*a Lee Warford,a David L. Hughes,a Joseph A. Wright,a
Sophie H. Daleb and Mark R. J. Elsegoodb
Received 28th January 2009, Accepted 15th May 2009
First published as an Advance Article on the web 7th July 2009
DOI: 10.1039/b901810g
The reaction of [V(Np-tolyl)Cl3] with the sulfur-bridged diphenol ligand 2,2¢-thiobis(4,6-di-
tert-butylphenol), {2,2¢-S[4,6-(t-Bu)2C6H2OH]2} (LSH2) afforded the complexes [V(LS)2] (1) and
[VOCl3(MeCN)2][H3Np-tolyl] (2). Complex 2 could also be prepared directly from [V(Np-tolyl)Cl3] and
‘wet’ acetonitrile. Reaction of [V(Np-tolyl)(Ot-Bu)3] with LSH2 afforded [VO(m2-OH)(LS)]2·6(MeCN)
(3), whilst reaction of [VO(On-Pr)3] with 2,2¢-sulfinylbis(4,6-di-tert-butylphenol),
{2,2¢-SO2[4,6-(t-Bu)2C6H2OH]2} (LSO2H2), afforded [V(LSO2)2]·MeCN (4). The reaction of
[VO(Oi-Pr)3] with the ethylidene-bridged diphenol 2,2¢-ethylidenebis(4,6-di-tert-butylphenol),
{2,2¢-CH3CH[4,6-(t-Bu)2C6H2OH]2} (LH2) afforded the hydroxyl bridged complexes
[(VOL)2(m2-OH)(m2-Oi-Pr)] (5) (major product) and [VO(m2-OH)(L)]2·4(MeCN) (6) (minor product). In
general, we find that controlled hydrolysis of [V(NAr)(On-Pr)3] (Ar = p-ClC6H4, p-OCNC6H4 or
p-tolyl) in the presence of LH2 reproducibly led to the vanadyl complex [VO(m-On-Pr)L]2·2(MeCN) (7),
in which the n-propoxide bridges both unexpectedly lie above the V2O2 plane. Reaction of the linear
triphenol 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-tert-butylphenol, [ArCH2Ar1CH2Ar] (Ar =
4,6-di-tert-butylphenol; Ar1 = 4-tert-butylphenol) (L1H3), and [VO(On-Pr)3] afforded the complex
[VOL1]2·3(MeCN) (8), whilst reaction of [V(Np-tolyl)(Oi-Pr)3] with the related methylene-bridged
linear triphenol 2,6-bis(3,5-di-tert-butyl-2-hydroxybenzyl)-4-methylphenol, [ArCH2Ar2CH2Ar] (L2H3)
(Ar2 = 4-methylphenol), gave {[V(m2-O)(Np-tolyl)][VO(Oi-Pr)]L2}2·1.5(MeCN) (9). The crystal
structures of 1 to 9 are reported. Complexes 1–4 and 7–9 were screened as pro-catalysts for the
polymerisation of ethylene in the presence of the co-catalyst dimethylaluminium chloride (DMAC) and
the re-activator ethyltrichloroacetate (ETA). All are highly active ethylene polymerisation catalysts with
activities covering the range 2000 to 90 000 g mmol-1 h-1 bar-1, and these results are discussed in terms
of the ligands present at vanadium in the pro-catalyst. Complex 3 has also been screened for
ethylene/propylene copolymerisation.
this field of study,6 and Nomura has reported a number of
Introduction
imido/aryloxide systems,7 whilst we have previously communi-
cated a number of vanadyl complexes bearing chelating bi- or
tri-dentate phenolate ligands, the structures of which are shown in
Scheme 1.2a
The last couple of years have seen an upsurge of interest
in vanadium-based systems for a-olefin polymerisation.1 Very
high activities and thermal stability have been observed for a
number of systems, particularly where the vanadium pro-catalyst
is combined with an organoaluminium chloride co-catalyst such
as dimethylaluminium chloride (DMAC).2 The presence of the
reactivator ethyltrichloroacetate (ETA) has also proved to be
beneficial in most of these vanadium systems.3 Despite the fact that
the active species remains somewhat of a mystery, it is clear that
the use of certain ligands at vanadium leads to enhanced catalytic
performance. Amongst those affording the highest activities
to-date are phenoxyimine systems reported by Fujita et al.,4
and bis(benzimidazole)amines utilized by the group of Gibson.5
Aryloxides are also proving to be useful ancillary ligands in
aEnergy Materials Laboratory, School of Chemistry, University of East
Anglia, Norwich, UK NR4 7TJ. E-mail: carl.redshaw@uea.ac.uk
Scheme 1
bChemistry Department, Loughborough University, Loughborough,
Leicestershire, UK LE11 3TU
Given the high activities observed for such vanadyl systems,
we have extended our studies to include the use of other bi- and
† CCDC reference numbers 718343–718350. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b901810g
8900 | Dalton Trans., 2009, 8900–8910
This journal is
The Royal Society of Chemistry 2009
©

Scheme 2 Vanadium complexes 1–9 (R = t-butyl).
◦
˚
tri-phenols, including ligands with bridging sulfur and sulfonylene
groups (Scheme 2). Takaoki and Miyatake have previously utilised
a thiobis(phenoxy) vanadyl pro-catalyst to polymerise propylene
(activities ≤ 2000 g mmol-1 h-1 bar-1),8 whilst Janas and Sobota
have used 2,2¢-thiobis{4-(1,1,3,3-tetramethylbutyl)phenol} in con-
junction with [VCl3(THF)3] and [VO(OEt)3] to prepare dimeric
vanadium(III) and (V) complexes, respectively, which when sup-
ported on MgCl2 and activated with aluminium alkyls were
efficient ethylene polymerization catalysts (activities ≤ 11 708 g
mmol-1 h-1 bar-1).9 Two recent reports have also appeared in the
literature concerning the coordination of sulfur-bridged diphenols
to high-valent vanadium, and those synthetic/structural results
will be compared with ours reported here.10 In the patent literature,
there is mention of [V(NAr)(diphenolate)Cl]-type pro-catalysts,
where the diphenolate can be methylene or sulfur bridged, and the
imido group possesses a number of electron-withdrawing groups.11
We also note that mono- and bi-nuclear vanadium(V) alkoxides
are biologically attractive,12 and that [VOL(OR)]-type complexes
have been shown to undergo hydrolysis to afford bi-nuclear [VOL]2
(L = ONO tridentate ligand) species.13
Table 1 Selected bond lengths (A) and angles ( ) for 2
˚
Bond lengths/A
V(1)–O(1)
V(1)–Cl(1)
V(1)–Cl(2)
V(1)–Cl(3)
V(1)–N(1)
V(1)–N(2)
1.5893(13)
2.3647(6)
2.3586(5)
2.4257(6)
2.1369(16)
2.3990(16)
Bond angles/◦
O(1)–V(1)–Cl(1)
O(1)–V(1)–Cl(2)
O(1)–V(1)–Cl(3)
O(1)–V(1)–N(1)
O(1)–V(1)–N(2)
N(1)–V(1)–Cl(2)
Cl(1)–V(1)–Cl(3)
V(1)–N(1)–C(1)
V(1)–N(2)–C(3)
88.07(5)
99.08(5)
97.92(6)
92.75(7)
174.52(7)
168.17(5)
162.53(2)
166.71(15)
174.79(17)
protonated and lost from the metal centre. The structure of 2 is
shown in Fig. 1, with bond lengths and angles given in Table 1. The
vanadium centre is distorted octahedral with a mer arrangement of
chloride ligands. The oxo group exerts a strong trans influence on
Results and discussion
Use of sulfur-bridged diphenols
˚
the acetonitrile [V(1)–N(2) 2.3990(16) cf. V(1)–N(1) 2.1369(16) A].
The reaction of [V(Np-tolyl)Cl3] with the sulfur-bridged diphe-
nol pro-ligand 2,2¢-thiobis(4,6-di-tert-butylphenol), {2,2¢-S[4,6-
(t-Bu)2C6H2OH]2} (LSH2) afforded a mixture of the complexes
[V(LS)2] (1) and [VOCl3(MeCN)2][H3Np-tolyl] (2) in isolated
yields of 47 and 17%, respectively. Complex 2 could also be
prepared directly from [V(Np-tolyl)Cl3] and ‘wet’ acetonitrile in
> 90% yield. Both brown 1 and green/brown 2 can be readily
recrystallised from acetonitrile affording crystals suitable for X-ray
diffraction. Complex 1 is the same as that reported by Chaudhuri
et al., where it was obtained from the reaction of the ligand LSH2
with [VCl3(THF)3] in the presence of Et3N.9b In the formation
of anilinium salt 2, the imido group of [V(Np-tolyl)Cl3] has been
There are four unique N–H ◊ ◊ ◊ Cl hydrogen bonds (Fig. 2, Table 2)
involving all three hydrogen atoms of the anilinium salt; this results
in chains that run along the b axis with only weak interactions
between the chains.
The reaction of [V(Np-tolyl)(Ot-Bu)3] with LSH2 afforded the
purple complex [VO(m2-OH)(LS)]2 (3) in good yield (ca. 70%).
Crystals of 3·6MeCN suitable for X-ray diffraction were grown
from a ‘hot’ (heated to reflux for several minutes with a heat-
gun) solution of acetonitrile on cooling to ambient temperature.
The structure, shown in Fig. 3, is similar to the complex [VO(m2-
OH)(LS)]2·2(MeCN) reported by Cornman et al. for the product
of the reaction between [VO(Oi-Pr)3] and LSH2 in acetonitrile.9a
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8900–8910 | 8901
©

◦
◦
˚
˚
Table 2 Hydrogen bonds for 2 (A and
)
Table 3 Selected bond lengths (A) and angles ( ) for 3·6(MeCN) and the
Cornman structure.9a Symmetry operations ¢: for complex 3·6(MeCN) =
1 - x, 1 - y, 1 - x, and for Cornman’s complex = 2 - x, 1 - y, -z
D–H ◊ ◊ ◊ A
d(D–H) d(H ◊ ◊ ◊ A) d(D ◊ ◊ ◊ A)
∠(DHA)
Cornman structure
[VO(m2-OH)(LS)]2·4(MeCN)
N(3)–H(3A) ◊ ◊ ◊ Cl(1¢)
N(3)–H(3A) ◊ ◊ ◊ Cl(2¢)
N(3)–H(3B) ◊ ◊ ◊ Cl(3¢¢)
N(3)–H(3C) ◊ ◊ ◊ Cl(3)
0.91
0.91
0.91
0.91
2.51
2.51
2.39
2.47
3.2847(17) 144
3·6(MeCN)
3.1826(17) 131
3.2998(16) 174
3.3352(17) 160
˚
Bond lengths/A
1
2
Symmetry operations for equivalent atoms: ¢ x, y + 1, z, ¢¢ 1 -x, y +
1 -z.
,
V(1)–O(1)
V(1)–O(2)
V(1)–O(3)
V(1)–O(3¢)
V(1)–O(4)
V(1)–S(1)
1.8409(15)
1.8472(16)
1.9624(15)
1.9736(16)
1.5904(17)
2.7620(7)
V(1)–O(3)
V(1)–O(4)
V(1)–O(2)
V(1)–O(2¢)
V(1)–O(1)
V(1)–S(1)
1.838(2)
1.861(2)
1.973(2)
1.973(2)
1.593(2)
2.7953(7)
Bond angles/◦
O(4)–V(1)–O(1)
O(4)–V(1)–O(2)
O(4)–V(1)–O(3)
O(4)–V(1)–O(3¢)
O(4)–V(1)–S(1)
O(1)–V(1)–O(3)
O(2)–V(1)–O(3¢)
V(1)–O(3)–V(1¢)
99.30(8)
O(1)–V(1)–O(3)
O(1)–V(1)–O(4)
O(1)–V(1)–O(2)
O(1)–V(1)–O(2¢)
O(1)–V(1)–S(1)
O(3)–V(1)–O(2)
O(4)–V(1)–O(2¢)
V(1)–O(2)–V(1¢)
97.89(8)
99.79(8)
97.81(8)
103.57(8)
102.82(8)
172.90(6)
154.24(7)
156.72(7)
106.79(7)
101.85(8)
103.76(8)
172.33(7)
157.27(7)
154.12(7)
106.50(8)
Fig. 1 CAMERON representation of the structure of 2 showing spheres
of arbitrary size; hydrogen atoms (except H3a, H3b and H3c) have been
omitted for clarity.
Fig. 3 CAMERON representation of the structure of 3·6MeCN showing
spheres of arbitrary size; alkyl groups, hydrogen atoms (except H3) and
four non-coordinated molecules of acetonitrile have been omitted for
clarity.
Fig. 2 Chains of 2 formed by hydrogen bonds. View is down the
crystallographic a-axis.
of acetonitrile at ambient temperature. The structure, shown in
Fig. 4, reveals a distorted octahedral vanadium centre bound by
two facially coordinated LSO2 ligands. Two molecules of 4·MeCN
are present in the asymmetric unit, and have similar geometric
parameters (Table 4).
Bond lengths and angles for 3·6(MeCN) and the Cornman
complex are compared in Table 3. Both complexes lie on centres
of symmetry and contain facially bound LS ligands in which the
sulfur is trans to an oxo ligand. However in 3·6(MeCN) the hydrox-
ide bridges are slightly asymmetric, with one of the three unique
acetonitrile solvent molecules hydrogen-bonded to each bridge.
The reaction of [VO(On-Pr)3] with 2,2¢-sulfonylenebis(4,6-di-
tert-butylphenol), {2,2¢-SO2[4,6-(t-Bu)2C6H2OH]2} (LSO2H2), af-
forded brown [V(LSO2)2] (4) in ca. 33% yield. Crystals of 4·MeCN
suitable for X-ray diffraction were grown from a saturated solution
Use of ethylidene-bridged diphenols
The reaction of [VO(Oi-Pr)3] with the ethylidene-bridged diphe-
nol 2,2¢-ethylidenebis(4,6-di-tert-butylphenol), {2,2¢-CH3CH[4,6-
(t-Bu)2C6H2OH]2} (LH2) afforded the hydroxyl bridged
8902 | Dalton Trans., 2009, 8900–8910
This journal is
The Royal Society of Chemistry 2009
©

◦
◦
˚
˚
Table 4 Selected bond lengths (A) and angles ( ) for 4·MeCN
Table 5 Selected bond lengths (A) and angles ( ) for 5 and 6·4(MeCN).
1
2
Symmetry operations ¢: for complex 5 =
- x, y, 1 - z, and for
6·4(MeCN) = 2 - x, 1 - y, -z
˚
Bond lengths/A
5
6·4(MeCN)
V(1)–O(1)
V(1)–O(2)
V(1)–O(3)
V(1)–O(5)
V(1)–O(6)
V(1)–O(7)
2.0931(18)
1.816(2)
1.8765(19)
1.8755(18)
1.8520(19)
2.100(2)
V(2)–O(11)
V(2)–O(10)
V(2)–O(9)
V(2)–O(13)
V(2)–O(14)
V(2)–O(15)
2.0846(19)
1.8235(19)
1.8644(19)
1.8687(18)
1.8365(19)
2.0868(19)
˚
Bond lengths/A
V(1)–O(1)
V(1)–O(2)
V(1)–O(3)
V(1)–O(4)
V(1)–O(5)
1.858(6)
V(1)–O(1)
V(1)–O(2)
V(1)–O(4)
V(1)–O(3)
V(1)–O(1¢)
1.9752(11)
1.5840(11)
1.8054(10)
1.8131(10)
1.9559(11)
1.5861(13)
1.8048(10)
1.8109(10)
1.9621(9)
Bond angles/◦
O(1)–V(1)–O(2)
O(1)–V(1)–O(3)
O(1)–V(1)–O(5)
O(1)–V(1)–O(6)
O(1)–V(1)–O(7)
O(2)–V(1)–O(6)
O(3)–V(1)–O(7)
84.23(8)
89.10(8)
174.94(8)
85.31(8)
87.77(8)
164.64(9)
176.20(8)
O(10)–V(2)–O(11)
O(9)–V(2)–O(11)
O(11)–V(2)–O(13)
O(11)–V(2)–O(14)
O(11)–V(2)–O(15)
O(10)–V(2)–O(14)
O(9)–V(2)–O(15)
85.72(8)
90.54(8)
174.22(8)
83.93(8)
86.51(7)
166.83(9)
176.84(8)
Bond angles/◦
O(1)–V(1)–O(2)
O(2)–V(1)–O(3)
O(2)–V(1)–O(4)
O(2)–V(1)–O(5)
O(1)–V(1)–O(4)
O(3)–V(1)–O(5)
V(1)–O(1)–V(1¢)
V(1)–O(5)–V(1¢)
O(3)–V(1)–O(4)
95.02(17)
105.77(6)
103.03(7)
112.15(5)
155.47(11)
141.49(4)
108.07(10)
110.11(8)
93.53(5)
O(2)–V(1)–O(1)
O(2)–V(1)–O(4)
O(2)–V(1)–O(3)
O(2)–V(1)–O(1¢)
O(1)–V(1)–O(3)
O(4)–V(1)–O(1¢)
V(1)–O(1)–V(1¢)
V(1)–O(1¢)–V(1¢)
O(3)–V(1)–O(4)
105.07(5)
104.92(5)
104.13(5)
104.35(5)
148.73(5)
148.59(5)
107.28(5)
107.28(5)
94.26(5)
Fig. 4 CAMERON representation of the structure of one of the two
independent molecules of 4·MeCN in the asymmetric unit, showing
spheres of arbitrary size; the solvent molecule, alkyl groups and hydrogen
atoms have been omitted for clarity.
complexes [(VOL)2(m2-OH)(m2-Oi-Pr)] (5) (major product) and
[VO(m2-OH)(L)]2 (6) (minor product). Both complexes can be
readily recrystallised from saturated solutions of acetonitrile
affording crystals suitable for X-ray crystallography. Complex
5 (Fig. 5, Table 5) lies on a 2-fold symmetry axis which
runs through O(5) and H(5) with O(1) and the attached
i-Pr group disordered close to the axis. The geometry at each
vanadium centre can be described as distorted square-based
pyramidal, and the centres are linked via asymmetric OH/Oi-
Pr bridging. The difference in the bridging ligands is best
illustrated by the angles subtended at each oxygen, V(1)–O(5)–
V(1¢) 110.11(8) cf. V(1)–O(1)–V(1¢) 108.07(10)◦. The chelating
ligand forms an 8-membered metallocycle adopting a boat
conformation, with a bite angle of 93.53(5)◦, somewhat smaller
than that found for the monomeric vanadyl complex {VOCl[2,2¢-
CH2(4-Me-6-t-BuC6H2O)2]} [106.9(2)◦],14 but comparable to that
found for the dimeric structure [VO(On-Pr)L]2 [94.49(10)◦].2a
Fig. 5 CAMERON representation of the structure of 5 showing spheres
of arbitrary size; tert-butyl groups and hydrogen atoms (except H5) have
been omitted for clarity.
The IR spectrum of 5 contains a strong band at 999 cm-1
=
assigned to the v(V O) group, and broader bands at 3175
and 3482 cm-1 assigned to v(OH). In complex 6·4(MeCN)
(Fig. 6, Table 5), the dimer sits about an inversion centre and,
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8900–8910 | 8903
©

are, as expected, similar, with only slight differences observed for
the angles about each vanadium centre. 1H NMR solution spectra
showed two isomers to be present in an approx. 4 to 1 ratio (major
to minor); in toluene-d8, C6D6 or CD3CN there was little change
in the appearance of the spectra over the temperature range 20
to 80 ◦C. 51V NMR spectra showed only trace signs of minor
hydrolysed (OH-bridged) product present in each case.
Use of methylene-bridged triphenols
Reaction of the linear triphenol 2,6-bis(3,5-di-tert-butyl-2-
hydroxybenzyl)-4-tert-butylphenol, [ArCH2Ar1CH2Ar] (Ar = 4,6-
di-t-butylphenol; Ar1 = 4-t-butylphenol) (L1H3), and [VO(On-
Pr)3] afforded the complex [VOL1]2 (8) in ca. 45% yield. The
complex can be readily recrystallised from acetonitrile, and the
structure of 8·3(MeCN) (Fig. 8, Table 7) is similar to that we
previously reported for the complex derived from the related triph-
enol ligand [ArCH2Ar2CH2Ar] (L2H3) (Ar2 = 4-methylphenol).2a
In particular, the ligand binds in an unsymmetrical fashion,
2
viz. h -coordination to one approximately tetrahedral vanadium
atom (with angles in the range 107.89(9) to 112.53(8)◦), with the
resulting eight-membered ring having a boat conformation with a
bite angle of 108.15(8)◦ (cf. 106.7(2)◦ for [VO(On-Pr)L]2). A two-
fold symmetry axis runs through the middle of the central cavity.
Interestingly, when we switched to the use of the isopropoxide
starting material [V(Np-tolyl)(Oi-Pr)3], reaction with the triph-
enol L2H3 led to the isolation of the complex {[V(m2-O)(Np-
tolyl)][VO(Oi-Pr)]L2}2 (9·1.5MeCN), containing four vanadium
centres (Fig. 9, Table 8). Here, V(3) and V(4) are approximately
tetrahedral, whilst V(1) and V(2) are best described as trigonal
bipyramidal with the axial positions in each occupied by a near-
linear imido group and the bridging central phenolate oxygen
of an L2 ligand. The two different vanadium environments are
clearly distinguishable in the 51V NMR spectrum [d: -452 (w1/2
4000), -515 (w1/2 1200)]. The molecule shows approximate two-
fold symmetry.
Fig. 6 CAMERON representation of the structure of 6·(4MeCN)
showing spheres of arbitrary size; hydrogen atoms (except H1 and H1¢),
tert-butyl groups and two molecules of unbound acetonitrile per dimer
have been omitted for clarity.
as in 3, there are acetonitrile ligands bound through O–H ◊ ◊ ◊ N
hydrogen bonds to the slightly asymmetric hydroxide bridges. The
other acetonitrile ligands associated with 6 simply fill the voids
in the lattice. Each vanadyl centre is square-based pyramidal,
with the vanadyl group at the apex. The chelating ligand forms
an eight-membered metallocycle adopting a boat conformation
◦
˚
[bite angle = 94.26(5) ]. The V ◊ ◊ ◊ V distance is 3.166 A. The
IR spectrum contains a strong band at 1014 cm-1 assigned to
the v(V O) group, and broader bands at 3165 and 3253 cm
Ethylene polymerisation
-1
=
assigned to v(OH). The ease of formation of 5 and 6 seems
to be related to the use and sensitivity of the vanadyl tris-
isopropoxide starting material. Under similar conditions, using
the analogous n-propoxide starting material, we have not observed
any hydroxide bridged species. Interestingly, Cornman et al. also
employed [VO(Oi-Pr)3] in the reaction with LSH2 which afforded
either [VO(LS)(m-OEt)]2 (from ethanol) or as mentioned earlier in
our discussions of compound 3, the hydroxide-bridged complex
[VO(LS)(m-OH)]2 (from acetonitrile), the formation of the latter
(and a related structure derived from a selenium-bridged diphenol)
was also reported by Chaudhuri et al.9b
Interestingly, the product obtained from the ‘controlled’ hy-
drolysis (one equivalent of H2O added) of [V(NAr)(On-Pr)3]/LH2
(Ar = p-ClC6H4, p-OCNC6H4 or p-tolyl), namely [VO(m-On-Pr)L]2
(7b), always contained (as characterised by single-crystal X-ray
diffraction for all three reactions using the differing Ar groups) n-
Pr groups on the same side of the V2O2 plane (Fig. 7b), which is in
contrast to that previously reported for the structure resulting
from the reaction of [VO(On-Pr)3] and LH2 (Fig. 7a).2a The
geometrical parameters (Table 6) associated with both structures
Complexes 1–4 and 7–9 (all samples were dried in vacuo for
12 h prior to use) were screened as pro-catalysts for ethylene
polymerisation in the presence of a variety of organoaluminium
co-catalysts (DMAC, MAO and Me3Al), and in the presence of
the re-activator ethyltrichloroacetate (ETA). Under the conditions
employed, only the combination of procatalyst/DMAC/ETA
gave significant catalytic activities (see Tables 9–11, Fig. 10).
Pro-catalysts 1 and 4, both of which contain no vanadyl
group, showed similar behaviour with activities in the region
of 21 000 g mmol-1 h-1 bar-1 affording high molecular weight
polymers (217 000 and 244 000, respectively). The absence of a
chelating ligand (run 2) led to a dramatic loss of catalytic activity,
with observed values down to ca. 2000 g mmol-1 h-1 bar-1. However,
when a combination of vanadyl group and chelating diphenolate
ligand (either methylene or sulfur-bridged) was present, observed
activities were extremely high (≥ 62 000 g mmol-1 h-1 bar-1).
Similarly, use of the methylene bridged triphenolate ligands in
combination with vanadyl (8) or vanadyl/vanadium imido groups
(9) afforded very high activities, with that observed from the
use of 9 being about 90 000 g mmol-1 h-1 bar-1. The polymers
8904 | Dalton Trans., 2009, 8900–8910
This journal is
The Royal Society of Chemistry 2009
©

◦
˚
Table 6 Selected bond lengths (A) and angles ( ) for ‘up-down’-[VO(On-Pr)L]2 (7a·MeCN) and 7b·2(MeCN)
‘up-down’-[VO(On-Pr)L]2 (7a·MeCN)
7b·2(MeCN)
˚
Bond lengths/A
V(1)–O(1)
V(1)–O(2)
V(1)–O(3)
V(1)–O(4)
V(1)–O(1¢)
1.973(3)
1.583(3)
1.802(2)
1.815(2)
1.973(3)
V(1)–O(1)
V(1)–O(8)
V(1)–O(6)
V(1)–O(7)
V(1)–O(2)
1.976(4)
1.568(4)
1.797(4)
1.802(4)
1.967(4)
V(2)–O(2)
V(2)–O(5)
V(2)–O(4)
V(2)–O(3)
V(2)–O(1)
1.974(4)
1.567(4)
1.814(4)
1.810(3)
1.977(4)
Bond angles/◦
O(3)–V(1)–O(4)
V(1)–O(3)–C(1)
V(1)–O(4)–C(17)
O(1)–V(1)–O(1A)
94.49(10)
141.3(2)
136.6(2)
O(6)–V(1)–O(7)
V(1)–O(6)–C(37)
V(1)–O(7)–C(45)
O(1)–V(1)–O(2)
93.47(17)
140.8(3)
137.7(3)
O(4)–V(2)–O(3)
V(2)–O(4)–C(12)
V(2)–O(3)–C(4)
O(2)–V(2)–O(1)
94.91(16)
139.5(3)
137.9(3)
72.35(12)
71.35(15)
71.21(15)
Fig. 7 CAMERON representation of the structures of (a) 7a·MeCN [2a] and (b) 7b·2(MeCN) showing spheres of arbitrary size; tert-butyl groups,
acetonitrile molecules and hydrogen atoms have been omitted for clarity.
afforded by both catalyst systems derived from the use of 8 and 9
displayed very similar properties with respect to molecular weight
and polydispersities (Table 9 and Fig. 10, runs 4 and 5), suggesting
that similar active species were generated upon the addition of
DMAC.
Complex 3 was screened under more robust conditions at both
25 ◦C and 80 ◦C—see Table 11. At the elevated temperature (80 ◦C,
run 2), there is a 10-fold increase in activity. This pro-catalyst was
also screened for ethylene/propylene copolymerization at 25 C,
and was found to have an activity of ca. 20 000 g mmol-1 h-1 bar-1
with 13.2% propylene incorporation.
In conclusion, we have structurally characterised a number
of high-valent vanadium complexes bearing chelating aryloxide
ligands with CH2, CH(Me), S or SO2 bridges. Screening for
ethylene polymerization in the presence of DMAC/ETA indicates
that the chelate ligand is clearly beneficial to the catalytic activity of
the system. Activity is further increased by the additional presence
of vanadyl or vanadium imido groups.
◦
More comprehensive screening was carried out upon 1
(Table 10). Over the temperature range 0–80 ◦C, the activity
of 1 was found to peak at ca. 60 ◦C (run 4); above this
temperature the activity was found to decrease slightly, with
a concomitant drop in the molecular weight of the resulting
polymer (Table 10, runs 1–5). A steady increase in activity, similar
to that of the niobium pro-catalysts bearing similar ligands,15
was found upon increasing the concentration of DMAC (runs
6–10); such an increase was found to lower the PDI of the
¯
resulting polymer, whilst the weight of the polymer (Mw) remained
Experimental
relatively constant. The use of other co-catalysts, such as TMA
and MAO, led to a significant drop in polymerisation activity. A
similar drop in activity was also observed upon removal of ETA;
such a trend has been observed previously for vanadium-based
catalysis.1–3
General
All manipulations were carried out under an atmosphere of
dinitrogen using standard Schlenk and cannula techniques or in a
conventional nitrogen-filled glove-box. Solvents were refluxed over
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8900–8910 | 8905
©

◦
2
2a
˚
Table 7 Selected bond lengths (A) and angles ( ) for 8·3(MeCN) and the analogue [VOL ]2
8
[VOL2]2
˚
Bond lengths/A
V(1)–O(1)
1.5954(18)
1.7823(16)
1.7707(16)
1.7760(17)
V(1)–O(7)
V(1)–O(1)
V(1)–O(5)
V(1)–O(6)
1.592(6)
1.779(5)
1.748(5)
1.722(5)
V(2)–O(8)
V(2)–O(2)
V(2)–O(3)
V(2)–O(4)
1.587(6)
1.752(5)
1.754(5)
1.760(5)
V(1)–O(1A)
V(1)–O(1B)
V(1)–O(1C)
Bond angles/◦
O(1)–V(1)–O(1A)
O(1)–V(1)–O(1B)
O(1)–V(1)–O(1C)
O(1A)–V(1)–O(1B)
O(1B)–V(1)–O(1C)
O(1A)–V(1)–O(1C)
109.85(9)
107.89(9)
110.00(9)
112.53(8)
108.15(8)
108.39(8)
O(7)–V(1)–O(1)
O(7)–V(1)–O(5)
O(7)–V(1)–O(6)
O(1)–V(1)–O(5)
O(5)–V(1)–O(6)
O(1)–V(1)–O(6)
110.1(3)
107.7(3)
110.3(3)
112.4(2)
107.7(2)
108.6(2)
O(8)–V(2)–O(2)
O(8)–V(2)–O(3)
O(8)–V(2)–O(4)
O(2)–V(2)–O(3)
O(3)–V(2)–O(4)
O(2)–V(2)–O(4)
107.6(3)
109.1(3)
110.4(3)
106.7(2)
109.7(2)
113.1(2)
◦
˚
Table 8 Selected bond lengths (A) and angles ( ) for 9·1.5(MeCN)
˚
Bond lengths/A
V(1)–N(1)
V(1)–O(6)
V(1)–O(5)
V(1)–O(11)
V(1)–O(2)
V(3)–O(7)
V(3)–O(1)
V(3)–O(11)
V(3)–O(8)
1.6625(15)
1.7853(12)
1.8944(12)
1.8456(13)
2.1547(12)
1.5869(15)
1.7850(13)
1.7394(13)
1.7446(14)
V(2)–N(2)
V(2)–O(3)
V(2)–O(2)
V(2)–O(12)
V(2)–O(5)
V(4)–O(9)
V(4)–O(4)
V(4)–O(12)
V(4)–O(10)
1.6631(15)
1.7924(12)
1.9015(12)
1.8450(13)
2.1604(12)
1.5855(15)
1.7803(13)
1.7490(13)
1.7419(15)
Bond angles/◦
N(1)–V(1)–O(6)
N(1)–V(1)–O(5)
N(1)–V(1)–O(11)
N(1)–V(1)–O(2)
O(5)–V(1)–O(6)
O(5)–V(1)–O(11)
V(1)–N(1)–C(75)
O(7)–V(3)–O(1)
O(7)–V(3)–O(11)
O(7)–V(3)–O(8)
O(1)–V(3)–O(8)
O(1)–V(3)–O(11)
V(3)–O(11)–V(1)
V(1)–O(5)–V(2)
101.08(6)
95.27(6)
N(2)–V(2)–O(3)
N(2)–V(2)–O(2)
N(2)–V(2)–O(12)
N(2)–V(2)–O(5)
O(2)–V(2)–O(3)
O(2)–V(2)–O(12)
V(2)–N(2)–C(82)
O(9)–V(4)–O(4)
O(9)–V(4)–O(12)
O(9)–V(4)–O(10)
O(4)–V(4)–O(10)
O(4)–V(4)–O(12)
V(4)–O(12)–V(2)
V(1)–O(2)–V(2)
101.35(7)
94.82(7)
99.99(7)
100.30(7)
158.47(6)
103.29(5)
136.67(6)
174.01(14)
110.64(7)
108.61(7)
106.90(8)
109.25(7)
110.92(6)
141.62(8)
110.40(5)
158.26(6)
104.74(6)
134.81(6)
170.99(14)
110.21(7)
109.26(7)
108.08(8)
108.17(7)
110.42(6)
141.72(8)
110.36(5)
Fig. 8 CAMERON representation of the structure of 8·3(MeCN) show-
ing spheres of arbitrary size; alkyl groups, three molecules of acetonitrile
and hydrogen atoms have been omitted for clarity.
an appropriate drying agent, and distilled and degassed prior to
use. Elemental analyses were performed by the microanalytical
services of the School of Chemical Sciences & Pharmacy at
UEA or at London Metropolitan University. EPR spectroscopy
was performed on an X-band ER200-D spectrometer (Bruker
Spectrospin) interfaced to an ESP1600 computer and fitted with
a liquid helium flow cryostat (ESR-900; Oxford Instruments).
NMR spectra were recorded on a Varian VXR 400 S spectrometer
at 400 MHz or a Gemini at 300 MHz (1H), 105.1 MHz (51V)
at 298 K; chemical shifts are referenced to the residual protio
impurity of the deuterated solvent. IR spectra (nujol mulls, KBr
windows) were recorded on Perkin-Elmer 577 and 457 grating
spectrophotometers. The complexes [V(Np-tolyl)(OR)3] (R =
n-Pr, i-Pr, t-Bu) and [VO(OR)3] (R = Et, n-Pr) were prepared
as described in the literature.16,17 [VO(Oi-Pr)3] was a gift from
the former Inorg Tech. Ltd. The ligand LSH2 was prepared
as previously reported,18 while LSO2H2 was prepared via the
hydrogen peroxide oxidation of LSH2.8
Table 9 Ethylene polymerisation runs for 1, 2, 4, 8 and 9
Activity/g mmol-1 Mw/g
Mn/ g
¯
Run Catalyst h-1 bar-1
mol-1
mol-1
PDI mp/◦C
1
2
1
2
4
8
9
20 480
2 120
21 640
89 840
36 660
217 000
256 000
81 700 2.7
60 100 4.3
132.9
134.3
134.4
135.0
133.7
3
244 000 111 000 2.2
4a
5b
173 000
178 000
43 800 4.0
40 900 4.3
a 10 min run time. b 15 min run time. All runs completed with 0.05 mmol
of [V], 40 000 equivalents DMAC and 0.1 mL ETA in 50 mL toluene at
50 ◦C for 30 min.
All other chemicals were obtained commercially and used as
received unless stated otherwise.
8906 | Dalton Trans., 2009, 8900–8910
This journal is
The Royal Society of Chemistry 2009
©

Fig. 10 Lifetime graph of ethylene polymerisation for 1, 2, 4, 8 and 9.
Conditions: 50 ml toluene at 50 ◦C, 0.1 mL ETA, 40 000 equivalents of
DMAC, 0.05 mmol of [V].
Table 11 Ethylene and ethylene/propylene screening for 3 under more
robust conditions
Run
T/◦C
Activity/g mmol-1 h-1 bar-1
C3 content (mol%)
1
2
3
25
80
25
7 500
72 600
19 800
n/a
n/a
13.2
Conditions: toluene 250 mL, 250 equiv. of DMAC, 0.5 mmol ETA, 15 min.
Upon cooling, the solvents were removed in vacuo and the residue
was extracted into acetonitrile. Standing at ambient temperature
for 3–4 d afforded 1 as green/brown prisms, yield: 0.83 g, 47%
together with {[VOCl3(NCMe)2]·[p-tolylNH3]} (2) (0.12 g, 17%).
◦
For 1: mp > 250 C. C56H80O4S2V (932.26) calcd (found) C 72.2
(72.1) H 8.7 (8.6). m/z (MALDI): 932 (M+). IR (cm-1): 2735 s,
2619 m, 2601 s, 2358 s, 2286 s, 2260 m, 1562 m, 1507 m, 1260 m,
1089 m, 1053 m, 1024 m, 975 m, 865 m, 801 w, 798 w, 740 s, 659 m.
Magnetic moment m = 1.62mB. EPR (toluene, 298 K): giso = 1.98,
Aiso = 69 G, (toluene, 10 K) g^ = 1.99, A^ = 67 G, gꢀ = 1.96, Aꢀ =
185 G.
Fig. 9 (a) CAMERON representation of the structure of 9·1.5(MeCN)
showing spheres of arbitrary size. (b) View of the core of 9·1.5(MeCN).
Solvent molecules, tert-butyl groups and hydrogen atoms have been
omitted for clarity.
Alternative synthesis of {[VOCl3(NCMe)2]·[p-tolylNH3]} (2).
[V(Np–tolyl)Cl3] (1.00 g, 3.81 mmol) was refluxed in degassed ace-
tonitrile (50 mL). Cooling of the solution to ambient temperature
and removal of solvent in vacuo afforded 2 as a brown solid. Yield:
1.30 g, 94%. mp 95 ◦C. C11H16ON3Cl3V (363.57) calcd (found): C
36.3 (35.8) H 4.4 (5.1) N 11.6 (11.1)%. 1H NMR (C6D6, 400 MHz)
Table 10 Ethylene screening for 1
¯
Activity/g
Mw/g
Run [Al] : [V] T/◦C mmol-1 h-1 bar-1
mol-1
Mn/g mol-1 PDI
3
3
d: 7.24 (2 H, d JHH 4.8 Hz, tolyl-H), 6.38 (2 H, d, JHH 4.8 Hz,
tolyl-H), 3.83 (3 H, bs, NH3), 1.82 (3 H, s, tolyl-Me), 0.59 (6 H, bs,
MeCN).51V (C6D6, 105.1 MHz) d: -384.24 (w1/2 448). m/z (EI+):
255 ([VOCl3(MeCN)2]+), (EI-): 108 (H3Np-tolyl-). IR (cm-1): 2726
m, 2360 m, 2321 m, 2293 m, 1602 bm, 1557 w, 1260 s, 1094 bm,
1017 bm, 865 w, 802 w, 725 w.
1
2
3
4
5
6
7
8
9
20 000
20 000
20 000
20 000
20 000
10 000
20 000
30 000
40 000
50 000
0
25
45
60
80
25
25
25
25
25
2 760
4 920
11 320
33 040
28 280
5 880
6 310
7 480
7 760
8 240
464 000 126 000
360 000 160 000
332 000 115 000
188 000 71 400
54 200 25 500
367 000 97 800
3.7
2.2
2.9
2.6
2.1
3.8
—
—
—
2.3
—
—
—
—
—
—
Synthesis of [VO(l2-OH)(LS)]2·6(MeCN) (3). [V(Np-
tolyl)(Ot-Bu)3] (0.85 g, 2.26 mmol) with LSH2 (1.00 g, 2.26 mmol)
were refluxed in toluene (30 mL) for 12 h. Following removal of
volatiles in vacuo, the residue was extracted into ‘hot’ acetonitrile
(30 mL), affording as a purple crystalline solid 3·6(MeCN) on
prolonged standing at ambient temperature. Yield 0.99 g, 68%.
C58H85NO8S2V2 (sample dried in vacuo for 12 h, -5MeCN, 1090.5)
calcd (found): C 63.9 (64.0) H 7.9 (8.7) N 1.3 (1.3)%. IR: 3413 bs,
1716 w, 1636 w, 1583 w, 1515 w, 1362 s, 1284 s, 1260 s, 1202 w,
10
386 000 169 000
All runs completed with 5 mmol of [V], DMAC and 0.1 mL ETA in 50 mL
of toluene for 15 min.
Synthesis of [V(LS)2] (1). [V(Np-tolyl)Cl3] (1.00 g, 3.81 mmol)
and LSH2 (1.69 g, 3.82 mmol) were refluxed in toluene for 12 h.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8900–8910 | 8907
©

1137 m, 1100 s, 1021 m, 996 m, 916 w, 880 m, 839 s, 806 s, 750 m,
722 w, 636 m. 1H NMR (C6D6, 400 MHz) d: 7.53 (s, 2 H, Ar-H),
7.01 (s, 2 H, Ar-H), 3.69 (bs, 2 H, OH), 1.30 (bs, 18 H, C(CH3)3),
1.24 (bs, 18 H, C(CH3)3).
C66H102O8V2·2(C2H3N) (sample dried in vacuo for 12 h, -MeCN,
1
1166.5) calcd (found): C 70.0 (69.4) H 9.1 (9.1) N 1.2 (1.2). H
4
NMR (C6D6, 400 MHz) major d: 7.70 (d, JHH 2.4 Hz, 4 H,
arylH), 7.43 (d, 4JHH 2.4 Hz, 4H, arylH), 5.30 (q, 3JHH 7.2 Hz, 2 H,
bridge-CH), 5.06 (m, 4 H, CH2 of n-propyl), 1.72 (m, 4 H, CH2 of
Synthesis of [V(LSO2)2]·MeCN (4). [VO(On-Pr)3] (0.24 mL,
1.06 mmol) and LSO2H2 (1.00 g, 2.11 mmol) were refluxed in
toluene for 12 h. Upon cooling the solvents were removed in
vacuo and the residue was extracted into acetonitrile. Standing at
ambient temperature for 3–4 d afforded 4·MeCN as brown prisms.
Yield: 350 mg, 33%. mp > 250 ◦C. C56H80O8S2V (sample dried in
vacuo for 12 h, -MeCN, 996.33) calcd (found) C 67.5 (67.7) H 8.1
(8.3). m/z (MALDI): 996 (M+). IR (cm-1): 3359 bs, 3122 bs, 2730 s,
2609 s, 2349 s, 2288 s, 2260 s, 1563 s, 1510 s, 1260 m, 1090 bm,
1019 m, 985 m, 866 m, 801 m, 722 s, 660 s. Magnetic moment m =
1.71mB. EPR (toluene, 298 K): giso = 1.97, Aiso = 70 G, (toluene,
10 K) g^ = 1.99, A^ = 65 G, gꢀ = 1.96, Aꢀ = 186 G.
3
n-propyl), 1.58 (s, 36 H, C(CH3)3), 1.53 (d, JHH 7.2 Hz, 6 H,
3
bridge-CH3), 1.32 (s, 36 H, C(CH3)3), 0.57 (t, 6 H, JHH 6.7 Hz,
4
6 H, CH3). Minor d: 7.52 (d, JHH 2.4 Hz, 4 H, arylH), 7.36 (d,
4JHH 2.4 Hz, 4 H, arylH), 5.33 (q, 3JHH 7.2 Hz, 2 H, bridge-CH),
5.02 (m, 4 H, CH2 of n-propyl), 1.64 (m, 4 H, CH2 of n-propyl),
3
1.54 (d, JHH 7.2 Hz, 6 H, bridge-CH3), 1.45 (s, 36 H, C(CH3)3),
1.23 (s, 36 H, C(CH3)3), 0.48 (t, 6 H, 3JHH 6.7 Hz, 6 H, CH3). 51
V
(C6D6, 105.1 MHz) d: -448.00 (w1/2 270), minor peaks at -289.46
(w1/2 440), -498.83 (w1/2 160).
Synthesis of [VOL1]2·3(MeCN) (8). [V(Np-tolyl)(On-Pr)3]
(0.62 g, 1.87 mmol) and L1H3 (1.00 g, 1.70 mmol) were refluxed
in toluene (40 mL) for 12 h. Upon cooling the volatiles were
removed in vacuo and the residue extracted into acetonitrile
affording 8·3(MeCN) as dark blocks. Yield: 0.96 g, 79%. M.p.
118 ◦C. C80H110O8V2 (sample dried in vacuo for 12 h, -3MeCN,
1301.63) calcd (found): C 73.8 (73.7) H 8.5 (8.5). 1H NMR (CDCl3,
300 MHz) d: 7.32–6.29 (12 H, overlaying signals, Ar–H), 4.38 (2
H, d, 2JHH 14.5 Hz, CH2), 4.13 (2 H, d, 2JHH 14.5 Hz, CH2), 3.86
Synthesis of [(VOL)2(l2-OH)(l2-Oi-Pr)] (5) and [VO(l2-
OH)(L)]2·4(MeCN) (6). To LH2 (2.00 g, 4.58 mmol) in toluene
(40 mL) was added [VO(Oi-Pr)3] (1.08 mL, 4.58 mmol). The dark
brown solution was refluxed for 12 h, volatiles were removed
in vacuo, and the residue was extracted into ‘hot’ acetonitrile
(30 mL). Prolonged standing (1–2 d) at ambient temperature
afforded dark brown crystals of 5 (1.74 g, 35%) and dark red
crystals of 6·4(MeCN) (yield (< 5%). Complex 5 can also be
recrystallised from dichloromethane at 0 ◦C. C63H96O8V2 (1083.28)
calcd (found) C 69.8 (70.4) H 8.9 (9.0). IR (cm-1): 3646 m, 3170
bm, 2724 m, 2673 m, 1649 w, 1589 m, 1415 w, 1261 m, 1234 m,
1199 m, 1149 m, 1106 bm, 1005 bm, 922 w, 904 w, 880 m, 797 m,
759 m, 634 m. 1H NMR (CDCl3, 400 MHz) d: 7.38–7.16 (3¥ m, 8
H, arylH), 5.45 (bm, 1 H, J not observed*, CH(CH3)2), 4.91 (q,
2 H, 3JHH 7.0 Hz, CHC(CH3)), 1.57 (d, 6 H, 7.0 Hz, CHC(CH3)),
1.37 (s, 36 H, C(CH3)3), 1.26 (s, 36 H, C(CH3)3), 1.23 (d, 3 H, J
not observed*, CH(CH3)2). m-OH not observed. * = cooling to
-20 ◦C had no effect. 51V (CDCl3, 105.1 MHz) d:–410.80 (w1/2
500).
For 6: m/z (FAB): 1066.6 (MH+ - 3MeCN - OH), 1049.6
(MH+ - 3MeCN - 2OH), 1034.7 (MH+ - 3MeCN - 2O). 1H NMR
(CDCl3, 400 MHz) d: 7.38–7.16 (3 ¥ m, 8 H, arylH), 4.92 (q, 2 H,
3JHH 7.0 Hz, CHC(CH3)), 1.57 (d, 6 H, 7.0 Hz, CHC(CH3)), 1.37
(s, 36 H, C(CH3)3), 1.26 (s, 36 H, C(CH3)3). m-OH not observed.
51V (CDCl3, 105.1 MHz) d: -410.91 (w1/2 438). IR (cm-1): 3489
w, 2620 w, 1595 w, 1507 w, 1411 w, 1363 m, 1261 s, 1216 w, 1201
w, 1154 w, 1095 bs, 1017 bs, 930 w, 905 w, 880 w, 800 bs, 725
w. C65H97.5N2.5O8V2 (sample dried in vacuo for 12 h, -1.5MeCN,
1144.0) calcd (found): C 68.2 (65.1) H 8.6 (8.5) N 3.1 (3.1).19
2
2
(2 H, d, JHH 14.4 Hz, CH2), 3.56 (2 H, d, JHH 14.4 Hz, CH2),
1.48–1.17 (90 H, overlaying signals, t-Bu). 51V (C6D6, 105.1 MHz)
d: -498 (w1/2 340). m/z (MALDI): 651 (M+/2). IR (cm-1): 1596 m,
1409 m, 1362 m, 1260 m, 1224 m, 1199 m, 1158 m, 1095 bs, 1014
bs, 924 m, 904 m, 881 m, 858 m, 799 s, 730 m, 687 w, 660 w.
Synthesis of {[V(l2-O)(Np-tolyl)][VO(Oi-Pr)]L2}2·1.5(MeCN)
(9). [V(Np-tolyl)(Oi-Pr)3] (1.35 g, 4.04 mmol) and L2H3 (1.00 g,
1.84 mmol) were refluxed intoluene (40mL) for 12h. Upon cooling
the volatiles were removed in vacuo and the residue extracted into
acetonitrile affording 9·1.5(MeCN) as red prisms. Yield: 0.57 g,
32%. M.p. 219 ◦C (decomposition). C94H126O12N2V4 (sample dried
in vacuo for 12 h, -1.5MeCN, 1679.80) calcd (found): C 67.2 (67.1),
H 7.6 (7.7) N 1.7 (1.7). 1H NMR (CDCl3, 300 MHz) d: 7.50–6.60
(12 H, overlaying signals, Ar–H) 6.46 (4 H, d, 3JHH 8.3 Hz, tolyl-
H), 6.06 (4 H, d, 3JHH 8.3 Hz, tolyl-H), 5.74 (2 H, d, 2JHH 16.8 Hz,
3
2
CH2), 5.22 (2 H, sept, JHH 8.0 Hz, Oi-Pr), 4.09 (2 H, d, JHH
16.8 Hz, CH2), 3.48 (2 H, d, 2JHH 16.8 Hz, CH2), 3.39 (2 H, d, 2JHH
16.8 Hz, CH2), 2.11 (3 H, s, Me), 2.07 (3 H, s, Me), 1.92 (3 H, s,
Me), 1.85 (3 H, s, Me), 1.48 (12 H, bs, Oi-Pr), 1.41 (18 H, s, t-Bu),
1.35 (9 H, s, t-Bu), 1.31 (9 H, s, t-Bu), 1.24 (9 H, s, t-Bu), 1.23 (9
H, s, t-Bu), 1.21 (9 H, s, t-Bu), 1.17 (9 H, s, t-Bu). 51V (C6D6, 105.1
MHz) d: -452 (w1/2 310), -515 (w1/2 487). m/z (FAB): 1623 (M+ -
Oi-Pr), 1540 (M+ - VO3i-Pr), 1524 (M+ - VO4i-Pr), 1508 (M+ -
VO5i-Pr). IR (cm-1): 1461 s, 1401 s, 1377 s, 1259 m, 1225 m, 1202
m, 1160 m, 1108 m, 1005 m, 920 m, 877 m, 868 m, 849 m, 796 m,
776 m, 625 m, 595 m.
Synthesis of [VO(On-Pr)L]2·2(MeCN) (7b). [V(NAr)(On-Pr)3]
(Ar = p-tolyl) (1.53 g, 4.59 mmol), LH2 (2.00 g, 4.58 mmol) and
H2O (0.08 mL, 4.44 mmol) were refluxed in toluene (40 mL) for
12 h. Upon cooling, volatiles were removed in vacuo, and the
residue was taken up in ‘hot’ MeCN (30 mL) and filtered whilst still
warm. Uponcooling to ambienttemperature, red/brown prisms of
7·2(MeCN) formed. Further crops of 7·2(MeCN) can be obtained
by concentration and cooling of the mother liquor. Yield: 2.19 g,
79%. m/z (MALDI): 1005 (M+ - 2MeCN - 2PrOH). IR (cm-1):
1745 w, 1592 m, 1262 m, 1233 m, 1199 m, 1172 m, 1147 m, 1112
m, 1031 m, 1002 s, 981 s, 921 m, 895 w, 881 m, 853 s, 797 m,
779 m, 758 m, 727 w, 693 w, 653 w, 635 m, 613 w, 574 s, 542 m.
Crystallography
For each sample, a crystal was mounted in oil on a glass fibre
and fixed in the cold nitrogen stream on an automated CCD
diffactometer equipped with Mo Ka radiation and a graphite
monochromator, except for 4·MeCN and 9·1.5MeCN which were
measured at Daresbury Laboratory SRS Stations 16.2 SMX
and 9.8, respectively. Intensity data were measured by thin-slice
8908 | Dalton Trans., 2009, 8900–8910
This journal is
The Royal Society of Chemistry 2009
©

This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 8900–8910 | 8909
©

w- or w- and q-scans. Data were processed using the CrysAlis-
RED,20 DENZO/SCALEPACK21 or SAINT22 programs. The
structures were determined by the direct methods routines in
the SHELXS23 or SIR-9224 programs and refined by full-matrix
least- squares methods, on F2, in SHELXL.24 The non-hydrogen
atoms were refined with anisotropic thermal parameters, except
in some disordered groups/solvent molecules of crystallisation.
For 2 the absolute structure was reliably determined; Flack
parameter x = -0.029(17). For 3·6MeCN, the acetonitrile in-
cluding N(3) was disordered over two closely spaced positions;
major occupancy 61.1(10)%. Also in 3·6MeCN, the tert-butyl
group at C(25) had the methyl groups modelled as disordered
over two sets of positions; major occupancy 58.1(6)%. For
5, the group O(1), C(31), C(32), C(33) was disordered 50/50
across the two-fold axis. In 6·4(MeCN) the tert-butyl group at
C(23) had the methyl groups modelled as disordered over two
sets of positions; major occupancy 70.7(13)%. In 8·3MeCN,
two tert-butyl groups were severely disordered, and the minor
component of each could only be successfully modelled using
isotropic thermal parameters. The tert-butyl group at C(41A)
had the methyl groups modelled as disordered over two sets of
positions, major occupancy 80%; the tert-butyl group at C(41B)
had the methyl groups modelled as disordered over two sets of
positions; major occupancy 53.7(7)%. In 9·1.5MeCN, one of the
acetonitrile molecules per unit cell was badly disordered, and was
modelled using the PLATON SQUEEZE procedure.25 SQUEEZE
recovered 27 electrons per unit cell in one void cf. 22 electrons for
one MeCN molecule, therefore 0.5 MeCN per molecule of the
complex. The methyl groups on the tert-butyl group at C(48) were
disordered over two sets of positions modelled with restraints
on geometry and anisotropic displacement parameters; major
occupancy: 81.6(5)%. Scattering factors for neutral atoms were
taken from reference 26. Crystal data and refinement results are
collated in Table 12.
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Acknowledgements
The EPSRC is thanked for financial support and the award of
beam time at the Daresbury Laboratory and Station Scientists
Dr J. E. Warren and Dr S. J. Teat are thanked for their support.
We thank Dr Shigekazu Matsui and Mr Sadahiko Matsuura of
Mitsui Chemical Inc., Chiba, Japan for the screening of complex
3. The Mass Spectrometry Service Centre, University of Wales,
Swansea is thanked for data.
19 Despite repeated elemental analyses for 6, there was no fit between the
experimental and the calculated values.
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8910 | Dalton Trans., 2009, 8900–8910
This journal is
The Royal Society of Chemistry 2009
©