Synthesis, spectroscopic and structural characterisation of vanadium(IV) and oxovanadium(IV) complexes with arsenic donor ligands

Article abstract of DOI:10.1016/j.poly.2010.02.003

The reaction of o-C₆H₄(AsMe₂)₂ with VCl₄ in anhydrous CCl₄ produces orange eight-coordinate [VCl₄{o-C₆H₄(AsMe₂)₂}₂], whilst

Full text of DOI:10.1016/j.poly.2010.02.003

Polyhedron 29 (2010) 1630–1638
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, spectroscopic and structural characterisation of vanadium(IV)
and oxovanadium(IV) complexes with arsenic donor ligands
a
a
Benjamin M. Gray a, Andrew L. Hector a, William Levason a, , Gillian Reid , Michael Webster ,
*
Wenjian Zhang a, Marek Jura b
a School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
b ISIS STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of o-C6H4(AsMe2)2 with VCl4 in anhydrous CCl4 produces orange eight-coordinate [VCl4{o-
C6H4(AsMe2)2}2], whilst in CH2Cl2 the product is the brown, six-coordinate [VCl4{o-C6H4(AsMe2)2}]. In
dilute CH2Cl2 solution slow decomposition occurs to form the VIII complex [V2Cl6{o-C6H4(AsMe2)2}2].
Six-coordination is also found in [VCl4{MeC(CH2AsMe2)3}] and [VCl4{Et3As)2]. Hydrolysis of these com-
plexes occurs readily to form vanadyl (VO2+) species, pure samples of which are obtained by reaction
of [VOCl2(thf)2(H2O)] with the arsines to form green [VOCl2{o-C6H4(AsMe2)2}], [VOCl2{MeC(CH2As-
Me2)3}(H2O)] and [VOCl2(Et3As)2]. Green [VOCl2(o-C6H4(PMe2)2}] is formed from [VOCl2(thf)2(H2O)]
and the ligand. The [VOCl2{o-C6H4(PMe2)2}] decomposes in thf solution open to air to form the diphos-
phine dioxide complex [VO{o-C6H4(P(O)Me2)2}2(H2O)]Cl2, but in contrast, the products formed from sim-
ilar treatment of [VCl4{o-C6H4(AsMe2)2}x] or [VOCl2{o-C6H4(AsMe2)2}] contain the novel arsenic(V) cation
Received 21 December 2009
Accepted 2 February 2010
Available online 10 February 2010
Keywords:
Vanadium tetrachloride
Vanadium oxide dichloride
Arsine
Phosphine
[o-C6H4(AsMe2Cl)(l
-O)(AsMe2)]+. X-ray crystal structures are reported for [V2Cl6{o-C6H4(AsMe2)2}2],
[VO(H2O){o-C6H4(P(O)Me2)2}2]Cl2, [o-C6H4(AsMe2Cl)(
diffraction data for [VCl4{o-C6H4(AsMe2)2}2].
l
-O)(AsMe2)]Clꢀ[VO(H2O)3Cl2] and powder neutron
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
V
III such as [VCl4(PR3)2]ꢁ or as phosphine oxide adducts, and possi-
bly small amounts of [VOCl2(PR3)2]. There are no authenticated
phosphine complexes of vanadium(IV) chloride. A small number
of di- and tri-arsine adducts of VCl4 were reported over 30 years
ago [13–15], often included as minor parts in works focused on
the TiIV systems. We have recently reported detailed characterisa-
tion of dithioether and diselenoether complexes [VCl4(dichalcoge-
noether)] and [{VOCl2(dithioether)}4] [6,16]. Many diphosphine
and diarsine ligands (L–L) form six-coordinate complexes,
The coordination chemistry of vanadium is the most compli-
cated of any 3d element, covering seven formal oxidation states
(VV to Vꢁ1) [1,2]. Compounds in the higher oxidation states, VV
and VIV are dominated by V@O species, labile in solution and rela-
tively easily reduced. Not surprisingly, complexes of the higher
oxidation states with neutral soft donor ligands are few, and where
obtained are highly reactive, moisture sensitive and very easily re-
duced. Thus we have recently shown that both series of oxovana-
dium(V) halides, VO2X and VOX3 (X = F or Cl) are immediately
reduced by phosphine or arsine ligands although very unstable thi-
oether adducts of VOX3 can be isolated [3–6]. Vanadium tetrachlo-
ride is an unstable liquid which slowly loses chlorine at ambient
temperatures forming VCl3, solid VBr4 exists only below ꢁ23 °C,
and VI4 is unknown [1], hence the coordination chemistry of VIV
halides is limited to adducts of VCl4. Although early work [7] re-
ported VCl4 was reduced by PPh3, subsequent studies of a range
of PR3 (and AsR3) adducts relying heavily upon EPR data reported
trans-[VCl4(ER3)2] complexes and Nb and Ta analogues [8–10]. De-
tailed re-examination of the vanadium systems [11,12] found no
evidence for [VCl4(PR3)2], and identified the products as containing
[TiX4(L–L)] with TiX4 (X = Cl or Br), and with very strong
r-donors
with small steric requirements such as o-C6H4(EMe2)2 (E = P or As)
or Me2P(CH2)2PMe2, eight-coordination is achievable in the
dodecahedral [TiX4(L–L)2] [18–22]. Eight coordination is also
known for Zr, Hf and Nb complexes of the diarsine [23–25]. How-
ever, in contrast to vanadium, Group 4 metals show little tendency
to form M@O species, and oxo-derivatives of these metals normally
contain M–O–M bridges [1]. Here we report an investigation of
corresponding arsenic ligand complexes and some reactions with
o-C6H4(PMe2)2.
2. Experimental
Infrared spectra were recorded as Nujol mulls between CsI
plates using a Perkin–Elmer 983G or Spectrum 100 spectrometers
* Corresponding author. Tel.: +44 023 80593792; fax: +44 023 80593781.
E-mail address: wxl@soton.ac.uk (W. Levason).
over the range 4000–200 cmꢁ1 1H NMR spectra were recorded
.
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.02.003

B.M. Gray et al. / Polyhedron 29 (2010) 1630–1638
1631
from CDCl3 solutions using a Bruker AV300 spectrometer. UV/visi-
5.9%. IR (Nujol mull)/cmꢁ1: 358 (br)
m
(VCl). UV–Vis. Emax (diffuse
ble spectra were recorded from CH2Cl2 solutions or as solid sam-
ples diluted with BaSO4 using the diffuse reflectance attachment
of a Perkin–Elmer Lambda 19 spectrometer. Magnetic measure-
ments were made on powdered samples at 25 °C using a John-
son–Matthey Magnetic Susceptibility Balance. Microanalyses on
new complexes were undertaken by Medac Ltd. Preparations were
undertaken using standard Schlenk and glove box techniques un-
der a N2 atmosphere, and rigorous exclusion of moisture is neces-
sary to obtain pure complexes. Solvents were dried by distillation
from CaH2 (CH2Cl2 or CCl4) or Na/benzophenone ketyl (hexane,
thf and diethyl ether). A fresh bottle of VCl4 (Aldrich) was used
as received. The ligands o-C6H4(PMe2)2, o-C6H4(AsMe2)2, MeC-
(CH2AsMe2)3 and Ph2As(CH2)2AsPh2 were made by literature
methods [26–28], as was [VOCl2(thf)2(H2O)] [29,30]. Et3As was
obtained from Strem.
reflectance)/cmꢁ1: 12 800, 17 900, 27 100.
l = 1.90 lB.
2.5. [V2Cl6{o-C6H4(AsMe2)2}2]
VCl4 (0.19 g, 1.0 mmol) was dissolved in anhydrous CH2Cl2
(40 mL) and the solution was carefully layered with a solution of
o-C6H4(AsMe2)2 (0.25 g, 0.9 mmol) in anhydrous CH2Cl2 (50 mL).
The mixture was stoppered and left at room temperature for two
weeks. Initially a brown solution developed, and then this depos-
ited a precipitate and some crystals. After two weeks the solid
was filtered off and dried to yield a pink-brown powder. Yield
0.12 g, 30%. Anal. Calc. for C20H32As4Cl6V2 (886.8): C, 27.1; H, 3.6.
Found: C, 27.9; H, 3.6%. IR (Nujol mull)/cmꢁ1: 340 (br), 270(sh)
m
(VCl). UV–Vis. Emax (diffuse reflectance)/cmꢁ1
500(sh), 27 800. = 2.80 lB
: 12 010, 19
l
.
2.1. [VCl4{o-C6H4(AsMe2)2}2]
2.6. [VCl3{MeC(CH2AsMe2)3}]
o-C6H4(AsMe2)2 (0.64 g, 2.5 mmol) was dissolved in anhydrous
CCl4 (10 mL) and VCl4 (0.19 g, 1.0 mmol) was added dropwise via
a syringe to the vigorously stirred solution, resulting in immediate
formation of an orange precipitate. The mixture was stirred for 1 h
then filtered and the orange solid rinsed with CCl4 (5 mL) and dried
in vacuo. Yield: 0.71 g, 92%. Anal. Calc. for C20H32As4Cl4V (764.9): C,
31.4; H, 4.2. Found: C, 31.0; H, 4.2%. IR (Nujol mull)/cmꢁ1: 325, 317
A solution of VCl4 (0.19 g, 1.0 mmol) in anhydrous CH2Cl2
(40 mL) was layered with a solution of MeC(CH2AsMe2)3 (0.38 g,
1.0 mmol) in anhydrous CH2Cl2 (60 mL) and stoppered. After one
week at room temperature a pink-brown precipitate was formed,
which was filtered off and dried in vacuo. Yield: 0.23 g, 42%. Anal:
Calc. for C11H27As3Cl3V (541.4): C, 24.1; H, 5.0. Found: C, 24.2; H,
m
(VCl). UV–Vis Emax (CH2Cl2)/cmꢁ1: 14 200, 19 800(sh), 23 800, 26
4.3%. IR (Nujol mull)/cmꢁ1: 345, 330
m(VCl). UV–Vis. Emax (diffuse
reflectance)/cmꢁ1: 13 900(w), 18 200, 28 600.
l
= 2.71 lB.
000; (MeCN) 14 400, 20 400, 24 050. Emax(diffuse reflectance)/
cmꢁ1: 13 260, 20 600(sh), 24 400.
l = 1.82 lB.
2.7. [VOCl2{MeC(CH2AsMe2)3}(H2O)]
2.2. [VCl4{o-C6H4(AsMe2)2}]
Powdered [VOCl2(thf)2(H2O)] (0.30 g, 1.0 mmol) was suspended
in CH2Cl2 (15 mL) and the triarsine (0.38 g, 1.0 mmol) added. Upon
stirring, a deep green solution rapidly formed, and after 1 h the sol-
vent was removed in vacuo and the dull green solid was rinsed
with CH2Cl2 (2 mL) and dried in vacuo. Yield: 0.48 g, 88%. Anal. Calc.
for C11H29As3Cl2O2V (540.0): C, 24.5; H, 5.4. Found: C, 24.7; H, 5.3%.
o-C6H4(AsMe2)2 (0.51 g, 1.8 mmol) was dissolved in anhydrous
CH2Cl2 (10 mL) and VCl4 (0.38 g, 2.0 mmol) was added via a syringe
to the vigorously stirred solution. A dark red solution formed. The
mixture was stirred for 1 h, concentrated and the brown solid was
filtered off and dried in vacuo. Yield 0.27 g, 56%. Anal. Calc. for
C10H16As2Cl4V (478.8): C, 25.1; H, 3.4. Found: C, 25.2; H, 3.6%. IR
IR (Nujol mull)/cmꢁ1: 3400, 1620 (H2O), 982(s)
(VCl). UV–Vis. Emax (diffuse reflectance)/cmꢁ1: 12 000(sh), 14 300,
22 940, 27 470. = 1.80 lB
m(VO), 357(sh), 334
(Nujol mull)/cmꢁ1: 356, 346
m :
(VCl). UV–Vis Emax (CH2Cl2)/cmꢁ1
15 100, 19 300(sh), 22 700. Emax (diffuse reflectance)/cmꢁ1: 13
m
l
.
600, 20 800, 24 500, 26 800.
l = 1.75 lB.
2.3. [VCl4{MeC(CH2AsMe2)3}]
2.8. [VOCl2{o-C6H4(AsMe2)2}]
(NB. This reaction is extremely moisture sensitive and the reaction
mixture turns green with trace moisture). MeC(CH2AsMe2)3 (0.76 g,
2.0 mmol) was dissolved in anhydrous CCl4, (10 mL) and VCl4
(0.38 g, 2.0 mmol) syringed in, producing an immediate brown
precipitate. The mixture was stirred for 1 h, and then the precipi-
tate filtered off, rinsed with CCl4 (5 mL) and dried in vacuo. Yield
0.56 g, 49%. Anal. Calc. for C11H27As3Cl4V (576.8): C, 22.9; H, 4.7.
Found: C, 22.3; H, 3.8%. IR (Nujol mull)/cmꢁ1: 368, 349, 332, 323
[VOCl2(thf)2(H2O)] (0.30 g, 1.0 mmol) was suspended in CH2Cl2
(15 mL) and o-C6H4(AsMe2)2 (0.57 g, 2.0 mmol) added. The blue so-
lid rapidly dissolved on stirring to form a deep green solution, and
after 1 h the solvent was concentrated to ꢂ5 mL in vacuo and then
refrigerated overnight. The dull green precipitate was filtered off,
rinsed with n-hexane (5 mL) and dried in vacuo. Yield: 0.29 g,
69%. Anal. Calc. for C10H16As2Cl2OV (429.9): C, 28.3; H, 3.8. Found:
C, 28.1; H, 3.0%. IR (Nujol mull)/cmꢁ1: 973(s)
UV–Vis Emax (CH2Cl2)/cmꢁ1 mol/dm3 molꢁ1 cmꢁ1): 15 150 (100),
m(VO), 340(br) m(VCl).
m
(VCl). UV–Vis Emax (diffuse reflectance)/cmꢁ1: 13 300, 19 200,
24 270, 26 040(sh). = 1.75 B. The same product was obtained
(e
l
l
17 850(sh), 22 980(sh ꢂ150), 27 000(sh ꢂ350), 29 500 (1500). Emax
using CH2Cl2 as solvent.
(diffuse reflectance)/cmꢁ1: 13 900, 14 900(sh), 24 300, 28 000.
l
= 1.69 lB.
2.4. [VCl4(Et3As)2]
Et3As (0.32 g, 2.0 mmol) was dissolved in anhydrous CH2Cl2
(10 mL) and the solution cooled to ꢁ30 °C; VCl4 (0.19 g, 1.0 mmol)
in CH2Cl2 (5 mL) was added dropwise via a syringe to the vigor-
ously stirred solution, which was allowed to warm to room tem-
perature with stirring. After 5 min. the dark red-brown
precipitate was filtered off, and dried in vacuo. Yield 0.25 g, 48%.
The dark red-brown powder slowly becomes paler on storage. Anal.
Calc. for C12H30As2Cl4V (517.0): C, 27.9; H, 5.8. Found: C, 28.0; H,
2.9. [VOCl2{o-C6H4(PMe2)2}]
This compound was prepared similarly to the diarsine analogue
as a bright green powder. Yield: 55%. Anal. Calc. for C10H16Cl2OP2V
(336.0): C, 35.7; H, 4.8. Found: C, 36.2; H, 5.2%. IR (Nujol mull)/
cmꢁ1: 970(s)
m
(VO), 348(s)
16 550 (80), 24 580 (130), 30 120 (4700); Emax (diffuse reflec-
tance)/cmꢁ1: 12 500(sh), 15 600, 25 000, 28 500(sh).
= 1.70 lB
m :
(VCl). UV–Vis Emax (CH2Cl2)/cmꢁ1
l
.

1632
B.M. Gray et al. / Polyhedron 29 (2010) 1630–1638
2.10. [VOCl2(Et3As)2]
2.12. Reaction of [VCl4{o-C6H4(AsMe2)2}2] in thf with moist air
[VOCl2(thf)2(H2O)] (0.30 g, 1.0 mmol) was suspended in CH2Cl2
(15 mL) and Et3As (0.35 g, 2.1 mmol) added. The blue solid slowly
dissolved on stirring to form a dull green solution. The solution was
concentrated to ꢂ4 mL and refrigerated overnight. The dull green
precipitate was filtered off, rinsed with n-hexane (5 mL) and dried
in vacuo. Yield: 0.22 g, 47%. Anal. Calc. for C12H30As2Cl2OVꢀ½CH2Cl2
[VCl4{o-C6H4(AsMe2)2}2] (0.1 g) was suspended in thf (20 mL)
and the solution was stirred in air. The solid dissolved to give a
dark solution which changed to green and then blue over a few
hours. After 12 h, concentration of the solution to a small volume
gave a blue powder, which was filtered off, rinsed with diethyl
ether (5 mL) and dried. Yield 0.03 g. IR (Nujol mull)/cmꢁ1: 990
(504.5): C, 29.7; H, 6.2. Found: C, 29.8; H, 5.9%. IR (Nujol)/cmꢁ1
:
t
(VO). UV–Vis Emax (Me2CO)/cmꢁ1: 12 500(sh), 14 900, 26 800.
979(s)
m
(VO), 340(br), 310(sh)
m
(VCl). UV–Vis. Emax (diffuse reflec-
Similar products were obtained starting with [VCl4{o-C6H4-
(AsMe2)2}] or [VOCl2{o-C6H4(AsMe2)2}]. Concentration of the syn-
thesis solutions to a small volume (5 mL) and refrigeration gave
blue crystals on several occasions, most diffracted too poorly for
an X-ray structure analysis, but in two cases the structures were
determined (see Section 3.5).
tance)/cmꢁ1: 12 000, 15 000 (sh), 26 300.
2.11. Reaction of VCl4 with o-C6H4(PMe2)2
A solution of o-C6H4(PMe2)2 (0.20 g, 1.0 mmol) in anhydrous
CH2Cl2 (10 mL) was frozen solid in liq. N2 and a solution of VCl4
(0.47 g, 3.0 mmol) in CH2Cl2 (10 mL) added via a syringe, and the
mixture allowed to warm. On melting a very dark red solution
formed immediately, and after 30 min this was concentrated in va-
cuo to 10 mL and the red-brown solid filtered off and dried in va-
cuo. Yield: 0.20 g. Anal. Calc. for C10H16Cl8P2V (527.8): C, 22.6; H,
3.0. Found: C, 23.3; H, 4.1%. IR (Nujol mull)/cmꢁ1: 360–300 (vbr)
2.13. X-ray crystallography and powder neutron diffraction
Crystallographic parameters are given in Table 1. Crystals were
isolated from the reaction mixtures usually following a period of
refrigeration as described above. Data collections were carried
out using a Bruker–Nonius Kappa CCD diffractometer fitted with
m
(VCl). UV–Vis (diffuse reflectance)/cmꢁ1: 15 300(sh), 21 400, 29
monochromated (graphite or confocal mirrors) Mo Ka radiation
000. The initial reaction solution exhibits a broad 31P{1H} NMR res-
onance at d = 91.
(k = 0.71073 Å). Crystals were held at 120 K in a nitrogen gas
stream. Structure solutions were straightforward [31–33] and
comments about some of the refinement details follow. H atoms
bonded to carbon were introduced in calculated positions using
the default C–H distance. Hydrogen atoms bonded to oxygen were
convincingly located in the later difference maps having both a
reasonable geometry and being high-up in the difference electron
density map peak listing. In addition, these H atoms formed hydro-
gen bonds of the type O–HꢀꢀꢀO or O–HꢀꢀꢀCl. These O-bonded H
atoms were refined with a fixed Uiso and inclusion of DFIX com-
mands on the O–H distance.
The above product (0.1 g) was dissolved in thf (20 mL) and the
solution was stirred while open to air, when the initial dark solu-
tion paled, changing colour through brown, yellow, green and fi-
nally pale blue. After 24 h. the solution was concentrated to
ꢂ10 mL and refrigerated for one week when it produced a small
number of pale blue crystals, which were used for the X-ray study.
Concentration of the mother liquor produced a blue powder. Anal.
Calc. for C20H36Cl2O7P4V: C, 37.9; H, 5.6. Found: C, 38.4; H, 6.3%. IR
(Nujol mull)/cmꢁ1
1145(s), 1098(vs)
mol/dm3 molꢁ1 cmꢁ1): 11 630(15), 20 830(12), 26 040(2100).
:
3400(vbr)
m
(OH), 1640 d(HOH), 1181(m),
m
(PO), 995(s)
m
(VO). UV–Vis Emax (CH2Cl2)/cmꢁ1
Powder X-ray diffraction data were collected using a Siemens
D5000 diffractometer with Cu Ka1 radiation. Samples were
(e
Table 1
Crystallographic data.a
Compound
[V2Cl6{o-
C6H4(AsMe2)2}2]ꢀnCH2Cl2
[VO(H2O){o-C6H4(P(O)-
Me2)2}2]Cl2ꢀ3H2O
[VOCl2(MeCN)2(H2O)] [o-C6H4(AsMe2Cl)(l-O)-
(AsMe2)][VO(H2O)3Cl2] ClꢀH2O
Formula
C20.8H33.6As4Cl7.6V2
954.66
orthorhombic
Pbca (#61)
14.383(3)
15.503(3)
15.688(4)
90
C20H40Cl2O9P4V
670.24
C4H8Cl2N2O2V
237.96
C10H24As2Cl4O6V
582.87
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c (#14)
11.374(2)
14.269(3)
19.474(3)
90
106.997(10)
90
3022.7(10)
4
triclinic
monoclinic
P21/c (#14)
7.8680(10)
8.6091(10)
31.333(4)
90
95.171(10)
90
2113.7(5)
4
ꢀ
P1 (#2)
5.4137(10)
7.4724(15)
11.963(3)
89.313(15)
80.920(10)
76.887(10)
465.28(16)
2
a
(°)
b (°)
90
90
c
(°)
U (Å3)
3498.2(13)
4
4.882
Z
l
(Mo K
a
) (mmꢁ1
)
0.760
1.595
4.102
F(0 0 0)
1862
1396
238
1156
Total number of reflections
Unique reflections
Rint
20 212
3981
0.085
26 765
6872
0.069
8107
2111
0.033
21 572
4757
0.041
Number of parameters,
restraints
171, 2
358, 8
108, 2
236, 9
Goodness-of-fit (GOF) on F2 1.175
1.148
1.078
1.080
Resid. electron density (e
ꢁ0.77 to +1.05
ꢁ0.59 to +0.55
ꢁ0.45 to +0.42
ꢁ0.54 to +0.54
Åꢁ3
)
b
R1 [Io > 2
r(Io)]
0.064
0.119
0.104
0.125
0.062
0.108
0.109
0.130
0.029
0.032
0.073
0.076
0.035
0.043
0.070
0.075
R1 (all data)
b
wR2 [Io > 2
r(Io)]
wR2 (all data)
a
Common items: temperature = 120 K; wavelength (Mo K
a) = 0.71073 Å; h (max) = 27.5°.
b
2
4 1/2
R1
=
R
|| Fo| ꢁ |Fc||/
R
|Fo|. wR2 = [
R
w(Fo ꢁ Fc2)2/
R
wFo
]
.

B.M. Gray et al. / Polyhedron 29 (2010) 1630–1638
1633
mounted under N2 in an air-tight holder. Structure refinements
were carried out using the GSAS package [34,35].
The powder neutron diffraction (PND) pattern of [VCl4{o-
C6H4(AsMe2)2}2] was collected over 2 h on a powdered sample
(300 mg) mounted in a 6 mm vanadium can, using the GEM dif-
fractometer at ISIS. The highest resolution data banks (banks 5
and 6) contained very broad peaks that were unsuitable for struc-
ture refinement. However a series of peaks in banks 3 and 4 did
seem suitable, albeit with a high, curving background. The data
were refined using the atom positions of [TiCl4{o-C6H4(PMe2)2}2]
as a starting point. It was not found to be possible to refine carbon
and hydrogen positions independently and hence the methyl
groups and phenyl rings were maintained in their known geome-
tries using a series of soft constraints. These were then allowed
to refine along with the As and Cl positions, and thermal parame-
ters for all atoms except V. V scatters very weakly (bcoh = ꢁ0.38 fm)
but this is not problematic as it is located on a special position
(0, 0, 0). The refined pattern from bank 3 is shown in Fig. 1.
(Rwp = 25.9%, Rp = 19.8%), and full details are available as Supple-
mentary material.
Fig. 1. Fit to the PND pattern of [VCl4{o-C6H4(AsMe2)2}2]. Allowed reflections are
shown by tick marks, the data points by crosses and the modelled intensity by the
upper continuous line. The lower continuous line shows the difference between the
measured and modelled patterns.
Scheme 1. Synthesis of VCl4 and VOCl2 complexes with tertiary arsines.

1634
B.M. Gray et al. / Polyhedron 29 (2010) 1630–1638
3. Results and discussion
3.1. VCl4 complexes
See Scheme 1. The reaction of VCl4 with o-C6H4(AsMe2)2 in
anhydrous CCl4, irrespective of the reactant ratios used, gave or-
ange [VCl4{o-C6H4(AsMe2)2}2] as reported [13,17], contrasting with
the corresponding TiIV system where 1:1 or 1:2 complexes can be
isolated depending upon the conditions [17–21]. The driving force
appears to be the insolubility of the 2:1 complex in CCl4. However,
by reaction of VCl4 and o-C6H4(AsMe2)2 in a 1:0.9 molar ratio using
CH2Cl2 as solvent, we have obtained the hitherto unknown brown
[VCl4{o-C6H4(AsMe2)2}]. Both complexes are poorly soluble in
CH2Cl2 and hydrolytically unstable in solution or in the solid state,
Fig. 2. The structure of [VCl4{o-C6H4(AsMe2)2}2] derived from analysis of the PND
data showing the atom labelling scheme. Hydrogen positions are omitted for clarity.
Selected bond lengths (Å) and angles (°): V1–Cl1 2.52(2); V1–As1 2.61(5); As1–C1
1.96(4); As1–C2 1.99(4); minimum As1–V1–As1 78.7(24); Cl1–V1–Cl1 96.12(25);
Cl1–V1–As1 69.7(12).
turning green. The magnetic moments of 1.7–1.8 lB (Section 2) are
typical of d1 VIV [36]. Solution UV–Vis spectra were difficult to ob-
tain due to very poor solubility and moisture sensitivity, but the
diffuse reflectance spectra show broad features at ꢂ14 000 and
ꢂ20 000 cmꢁ1, which are only slightly different in energy maxima
between the two complexes, an effect also observed for the corre-
sponding TiIV species [21]. The assignment of these features fol-
lows from the spectra of the d0 titanium analogues which show
X = Cl or Br) and to draw some conclusions from the bond lengths.
The V–Cl distance of 2.52(2) Å compares well with those reported
in [TiCl4{o-C6H4(AsMe2)2}2] (2.46(2) Å) and [TiCl4{o-C6H4-
(PMe2)2}2] (2.501(3) Å), whilst the V–As distance of 2.61(5) Å
may be compared with those in [TiX4{o-C6H4(AsMe2)2}2] (X = Cl
2.71(2) Å; X = Br 2.733(1) Å) [17,21,22]. The diarsine ligand
architecture is also satisfactorily generated by the PND data fit.
Comparisons with the bond lengths and angles in [V2Cl6{o-
C6H4(AsMe2)2}2] (Section 3.2 below) are also possible, and suggest
that the three major differences viz – change in metal oxidation
state and coordination number, and also the absence of directly
trans ligands in the dodecahedral complex (and hence no equiva-
lent to the trans influences clearly seen in the VIII complex) largely
cancel out.
The reaction of VCl4 with Et3As in CH2Cl2 or CCl4 is noticeably
exothermic at ambient temperatures and work-up of the reactions
affords materials which range in colour from dark red-brown to
pale pink, indicating variable amounts of reduction. However, if
the reactions are conducted at low temperature (ꢁ30 °C in CH2Cl2),
followed by brief warming to room temperature, and rapid isola-
tion of the solid, the product is the dark red-brown [VCl4(Et3As)2].
r
(As) ? Ti(d) and
p
(Cl) ? Ti(d) at ꢂ21 000 and ꢂ28 000 cmꢁ1
respectively, reflecting the difference in donor atom orbital ener-
gies [21]. In the more easily reduced VIV systems, the bands have
shifted to lower energy, but the ꢂ6–7 000 cmꢁ1 difference between
them remains. Thus the assignment of the lower energy band as
r
(As) ? V(3d) and the higher energy feature as
p(Cl) ? V(3d) is
secure. The (Cl) ? V(3d) bands are also of similar energy to the
p
corresponding features in the thio- and seleno-ether adducts
[6,16]. The two complexes are readily distinguished by the fre-
quencies of the V–Cl stretching modes in the far-IR spectra. The
six-coordinate [VCl4{o-C6H4(AsMe2)2}] shows very broad
m(VCl)
ꢂ360–340 cmꢁ1 (theory C2v, 2a1 + b1 + b2), whilst in the eight-
coordinate [VCl4{o-C6H4(AsMe2)2}2] the corresponding bands are
at 325, 315 cmꢁ1 (theory D2d, b2 + e), again replicating the trends
in the titanium systems [21]. Many attempts to obtain crystals of
either complex were unsuccessful, the complexes are slightly solu-
ble in chlorocarbons and upon standing, these solutions deposit VIII
complexes due to reduction (see Section 3.2), whilst donor solvents
including MeCN, thf or MeNO2 bring about more rapid reduction
and/or displacement of the diarsine.
The single strong symmetrical band in the far-IR (m(VCl)) at
358 cmꢁ1 suggests it is the trans isomer (theory eu). The reaction
of the softer and weaker donor arylarsines, Ph3As or
Ph2As(CH2)2AsPh2 with VCl4 in CH2Cl2 solution at 0 °C, gave prod-
ucts containing substantial amounts of VIII.
In view of the instability of [VCl4{o-C6H4(AsMe2)2}2], the struc-
ture analysis using powder diffraction was attempted. An X-ray
powder diffraction pattern showed a series of broad peaks that
resembled patterns generated from the single crystal X-ray struc-
ture of [TiCl4{o-C6H4(PMe2)2}2] [21,24]. A Le Bail fit to this pattern
in space group I-42m showed a reasonable fit with lattice param-
eters of a = 9.27 and c = 16.29 Å and Rietveld refinement using
the atom positions from [TiCl4{o-C6H4(PMe2)2}2] gave a respect-
able fit, though the errors on the heavy atom (Cl, As) positions were
large and the carbon positions could not be refined. The high inco-
herent scattering cross-section of hydrogen has meant that neu-
tron diffraction is little used in the determination of structures
containing organic substituents. Recent work has shown that by
using high flux diffractometers this is becoming less of a problem,
as the intensity of peaks above the incoherent background can be
significant [37]. On this basis a PND experiment was attempted.
The structure obtained from the PND data is shown in Fig. 2 and
full structural details are available as Supplementary material.
The errors in the atom positions are, of course, larger than those
that would be expected from a single crystal X-ray study. As ex-
pected with such a high incoherent scattering background, the
thermal parameters are also unrealistic. However, the data are
clearly good enough to demonstrate that [VCl4{o-C6H4(AsMe2)2}2]
is isostructural with [MX4{o-C6H4(EMe2)2}2] (M = Ti, Zr, Hf etc,
The triarsine MeC(CH2AsMe2)3 reacts with VCl4 in either CH2Cl2
or CCl4 to form brown [VCl4{j
2-MeC(CH2AsMe2)3}]; the reaction is
extremely sensitive to moisture, generating a green vanadyl com-
plex unless rigorous exclusion of moisture is achieved. The original
study [14] proposed that this complex and the [TiX4{MeC-
(CH2AsMe2)3}] analogues were seven-coordinate, but for the
titanium systems, variable temperature NMR studies showed the
arsenic ligand to be bound as a bidentate, although undergoing ra-
pid exchange of the free and bound –AsMe2 groups in solution at
ambient temperatures, and this was confirmed by the crystal
structure of [TiBr4{
the vanadium complex as [VCl4{
j
2-MeC(CH2AsMe2)3}] [21]. The formulation of
2-MeC(CH2AsMe2)3}] follows by
j
analogy, and is supported by the far-IR spectrum which shows
V–Cl stretches in the region typical of six-coordinate complexes.
3.2. VCl3 complexes
During many attempts to prepare crystals of the VCl4 com-
plexes, a dilute solution of VCl4 in anhydrous CH2Cl2 was layered
with a CH2Cl2 solution of the o-C6H4(AsMe2)2. On standing at room

B.M. Gray et al. / Polyhedron 29 (2010) 1630–1638
1635
C9
plex has not been isolated [3]. We find that although vanadyl com-
plexes are formed during hydrolysis, this does not constitute a
clean synthesis (see Section 3.4 below). We have recently shown
that [{VOCl2(dithioether)}4] can be prepared from reaction of
VCl4 with the siloxane (Me3Si)2O in CH2Cl2/MeCN solution, fol-
lowed by addition of the dithioether [6], but our attempts to apply
this route to the arsenic ligands failed. The product obtained was a
diarsine-free, pale-green powder, identified as [VOCl2(MeCN)x].
The failure is apparently due to the ability of the nitrile solvent
to displace the diarsine from the hard VIV centre, and was con-
firmed when attempts to grow crystals from an MeCN solution of
[VOCl2{o-C6H4(AsMe2)2}] (made as described below) yielded green
crystals of [VOCl2(MeCN)2(H2O)] (confirmed by a crystal structure
determination); the water is presumably adventitious. The struc-
ture (Fig. 4) shows an octahedral vanadium centre coordinated to
two cis chlorines, two cis nitriles with a V@O unit trans to H2O.
The relationship of this green complex to the reported [40] blue
[VOCl2(MeCN)2(H2O)] is unclear; the IR spectra are different
Cl2
V1
Cl3a
C7
As1a
C6
As2
C10
C8
V1a
Cl1
C5
C3
C4
As2a
As1
C2
Cl3
Cl2a
C1
Fig. 3. Structure of [V2Cl6{o-C6H4(AsMe2)2}2]ꢀnCH2Cl2 with the atom numbering
scheme adopted. The dimer is centrosymmetric. Ellipsoids are drawn at the 50%
probability level and H atoms and the solvate molecule are omitted for clarity.
Symmetry operation: a = 1 ꢁ x, ꢁy, 1 ꢁ z.
temperature, a brown-pink powder slowly separated, along with
some red-brown crystals. The structure of the latter revealed them
to be [V2Cl6{o-C6H4(AsMe2)2}2] (Fig. 3, Table 2), a centrosymmetric
dimer with an edge-shared bi-octahedral geometry. The vanadium
is in a distorted six-coordinate environment with a chelating diar-
sine, two short terminal chlorines (2.285(2), 2.292(2) Å) and longer
bridging chlorines (2.398(2), 2.471(2) Å) with the longest bond
trans to chlorine. This is the first structure of a VIII arsine, the clos-
est analogue being [V2Cl6(PMe3)4] [11], also an edge-sharing dimer,
but with two PMe3 ligands cis on one vanadium and the second
PMe3 pair trans on the other. The complex is paramagnetic with
(m
(CN) = 2320, 2300 cmꢁ1
m m(CN) = 2311,
(VO) = 990 cmꢁ1 (blue),
2285 cmꢁ1 (VO) = 980 cmꢁ1 (green)); presumably they are geo-
m
metric isomers.
However, we found that addition of o-C6H4(AsMe2)2, MeC-
(CH2AsMe2)3 or Et3As to
a suspension of [VOCl2(thf)2(H2O)]
[29,30] in CH2Cl2 resulted in formation of deep green solutions,
which on concentration yielded dull green powders, [VOCl2-
{o-C6H4(AsMe2)2}], [VOCl2{MeC(CH2AsMe2)3}(H2O)] and [VOCl2-
(Et3As)2] respectively (see Scheme 1). A similar reaction using
o-C6H4(PMe2)2 gave bright green [VOCl2{o-C6H4(PMe2)2}]. Despite
the presence of one water molecule in the vanadium reagent,
anhydrous compounds are readily obtained (see also Ref. [40] for
similar observations). All the vanadyl complexes hydrolyse in air,
but much more slowly than the VCl4 adducts, and slowly decolou-
rise even in the solid state over a few weeks due to reduction. The
l
= 2.80 l
B, consistent with a d2 ion, and the UV–Vis spectrum
shows weak d–d absorption bands in the visible region (12 010,
19 500(sh)), with the first intense (charge transfer) band in the
near UV (27 000 cmꢁ1), a typical VIII spectrum [37] and clearly very
different from those of [VCl4{o-C6H4(AsMe2)2}x] (x = 1, 2) above. A
dilute CH2Cl2 solution of VCl4 layered with a CH2Cl2 solution of
MeC(CH2AsMe2)3, also deposited a pink-brown powder over two
[VOCl2{o-C6H4(EMe2)2}] show strong IR active
m
(VO) stretches at
(VCl)
B) as expected.
970 (E = P) and 973 (E = As) cmꢁ1, typical of VIV@O bonds,
m
at ꢂ340–350 cmꢁ1, and are paramagnetic (
l
ꢂ 1.8
l
weeks, which was identified as (fac) [VCl3{j
3-MeC(CH2AsMe2)3}]
(Section 2.6). This complex has previously been obtained directly
from [VCl3(thf)3] and MeC(CH2AsMe2)3 [14].
The diffuse reflectance UV–Vis spectra are very different to those of
[VCl4(ligand)] discussed above, exhibiting several weak bands in
3.3. Vanadyl (VOCl2) complexes
Hydrolysis of VIV complexes commonly produces vanadyl spe-
cies, although only in certain cases does this yield clean products,
e.g. [VOCl2(L–L)] (L–L = 2,20-bipyridyl, 1,10-phenanthroline) [39],
as further hydrolysis often occurs displacing the neutral ligands.
The original reports of VCl4–arsine complexes [12–15] mentioned
exposure to moisture producing green vanadyl complexes, but
only for two triarsines, MeC(CH2AsMe2)3 and MeAs(o-C6H4AsMe2)2
were the products described [14]. Reaction of VOCl3 with o-
C6H4(AsMe2)2 in CH2Cl2 also gives a green product, but a pure com-
O2
C1
Cl1
Cl2
C2
N1
N2
V1
Table 2
C4
Selected bond lengths (Å) and angles (°) for [V2Cl6{o-C6H4(AsMe2)2}2]ꢀnCH2Cl2.
C3
V1ꢁCl1
V1ꢁCl2
V1ꢁCl3
2.285(2)
2.292(2)
2.398(2)
V1ꢁCl3a
V1ꢁAs1
V1ꢁAs2
2.471(2)
2.557(1)
2.646(1)
O1
Cl1ꢁV1ꢁCl2
Cl1ꢁV1ꢁCl3
Cl2ꢁV1ꢁCl3
Cl1ꢁV1ꢁAs1
Cl2ꢁV1ꢁAs1
Cl3ꢁV1ꢁAs1
As1ꢁV1ꢁAs2
101.39(8)
94.19(8)
164.11(8)
88.00(6)
89.39(6)
94.31(6)
77.59(4)
Cl1ꢁV1ꢁCl3a
Cl3ꢁV1ꢁCl3a
V1ꢁCl3ꢁV1a
Cl1ꢁV1ꢁAs2
Cl2ꢁV1ꢁAs2
Cl3ꢁV1ꢁAs2
Cl3aꢁV1ꢁAs2
94.86(8)
84.66(7)
95.34(7)
165.38(7)
81.18(6)
84.53(6)
99.51(6)
Fig. 4. Structure of [VOCl2(MeCN)2(H2O)] with the atom numbering scheme
adopted. Ellipsoids are drawn at the 50% probability level with H atoms given a
common arbitrary size. Selected bond lengths (Å) and angles (°): V1ꢁO1 1.593(2);
V1ꢁO2 2.232(2); V1ꢁN1 2.116(2); V1ꢁN2 2.124(2); V1ꢁCl1 2.3615(7); V1ꢁCl2
2.3523(7); O1ꢁV1ꢁN1 95.04(7); O1ꢁV1ꢁN2 93.21(7); N1ꢁV1ꢁN2 83.84(6);
N1ꢁV1ꢁO2 80.06(6); N2ꢁV1ꢁO2 82.48(6); O1ꢁV1ꢁCl2 100.93(5); N2ꢁV1ꢁCl2
90.46(5); O2ꢁV1ꢁCl2 83.68(4); O1ꢁV1ꢁCl1 97.07(5); N1ꢁV1ꢁCl1 89.36(5); Cl1–
V1–Cl2 93.38(2).
Symmetry operation: a = 1 ꢁ x, ꢁy, 1 ꢁ z.

1636
B.M. Gray et al. / Polyhedron 29 (2010) 1630–1638
the visible region, assigned as d–d transitions of the vanadyl unit,
and intense features in the near UV due to charge transfer transi-
tions [38]. The effect of an M@O unit in shifting the L ? M charge
3.4. Reactions with o-C6H4(PMe2)2
The reaction in a 1:1 or 1:2 molar ratio of VCl4: o-C6H4(PMe2)2
in CCl4 or CH2Cl2 at ambient temperatures gave dark solutions,
which on standing deposited unidentified intractable mixtures of
black, red and yellow powders (cf. the VCl4–PMe3 reaction [11]).
The reaction of o-C6H4(PMe2)2 in CH2Cl2 with excess (threefold)
of VCl4 at low temperatures produced a very dark solution which
had a single, broad 31P{1H}NMR resonance at d = 91, which is in
the range [43] observed for chlorophosphonium(V) derivatives. A
dark red-brown, very moisture sensitive solid was deposited on
standing, which was tentatively identified as [o-C6H4(PMe2Cl)2]-
[VIVCl6] from the microanalysis, its IR and UV–Vis spectra. The
red-brown solid is insoluble in chlorocarbons, and is decomposed
by donor solvents.
transfer bands to higher energy, due to the effects of M–O p-bond-
ing on the d-orbital energies is well established in many systems
[38]. The solution spectra of the two complexes are significantly
different in CH2Cl2 solution, suggesting a change in coordination
number – probably five-coordinate, square pyramidal monomers
in solution, which associate into ‘‘octahedral” chains or rings with
V@OꢀꢀꢀV links in the solids. Unfortunately, although green crystals
of the [VOCl2{o-C6H4(AsMe2)2}] have been obtained on several
occasions, these have proved poorly diffracting and hence a crystal
structure has not been obtained. The [VOCl2{MeC(CH2AsMe2)3}-
(H2O)] is rather different in that all samples show the presence
of significant amounts of water in the IR spectra, in addition to a
m
(VO) stretch at 982 and
gand rocking modes in the region 925–800 cmꢁ1 are very similar
to those in [VCl4{
2-MeC(CH2AsMe2)3}], and we tentatively formu-
late the complex as six-coordinate [VOCl2{
2-MeC(CH2AsMe2)3}-
m
(VCl) at 357, 334 cmꢁ1. The Me–As li-
When this solid was dissolved in thf and the solution stirred in
air for 24 h, the colour changed from red-brown, through yellow to
green and finally blue. Work-up of this blue solution yielded pale
blue crystals which the X-ray structure analysis (Fig. 5, Table 3)
j
j
(H2O)], with the water probably coordinating trans to V@O.
A small number of VOCl2 adducts of phosphines have been re-
ported previously, including the structurally authenticated
[VOCl2(PPh3)2] - a trigonal bipyramid with axial phosphines [12],
[VOCl2{P(SiMe3)3}2] [41], and (fac) octahedral [VOCl2{[12]ane-
P3Et3}] [42].
a
O1
Cl2
V1
O4
H62
H61
O6
O3
Cl1
O5
O2
C11
P3
C1
O2
P1
V1
O1
C10
C12
O3
C5
P2
b
O4
Cl3
C4
C3
C2
C19
P4
C6
C8
C3
C7
C4
C20
C7
As1
C1
C6
C8
C5
Fig. 5. Structure of the cation in [VO(H2O){o-C6H4(P(O)Me2)2}2]Cl2ꢀ3H2O showing
the atom numbering scheme. Ellipsoids are drawn at the 50% probability level and
H atoms bonded to C are omitted for clarity.
C9
C2
O5
Table 3
Selected bond lengths (Å) and angles (°) for [VO(H2O){o-C6H4(P(O)Me2)2}2]Cl2ꢀ3H2O.
C10
V1–O1
V1–O2
V1–O3
P1–O1
P2–O2
2.119(3)
2.037(3)
2.009(3)
1.510(3)
1.518(3)
V1–O4
V1–O5
V1–O6
P3–O3
P4–O4
1.992(3)
1.601(3)
2.045(3)
1.518(3)
1.518(3)
Fig. 6. Structure of [o-C6H4(AsMe2Cl)(
(a) the neutral [VO(H2O)3Cl2] residue and (b) the cation [o-C6H4(AsMe2Cl)(
l-O)(AsMe2)][VO(H2O)3Cl2]ClꢀH2O showing
l-
O)(AsMe2)]+. Ellipsoids are drawn at the 50% probability level and H atoms bonded
to C are omitted for clarity. Selected bond lengths (Å) and angles (°): (a) V1–O1
1.588(2); V1–O2 2.199(3); V1–O3 2.082(2); V1–O4 2.045(2); V1–Cl1 2.4063(10);
V1–Cl2 2.3441(10); O1–V1–O3 94.21(11); O1–V1–O4 98.05(12); O1–V1–Cl1
97.07(9); O1–V1–Cl2 100.79(9). (b) As1–C1 1.920(3); As1–C2 1.920(4); As1–C3
1.962(3); As1–O5 1.955(2); As2–O5 1.714(2); As1–Cl3 2.3765(9); As2–C8 1.898(3);
As2–C9 1.903(3); As2–C10 1.898(3); As2–O5–As1 117.06(12); O5–As1–Cl3
175.93(7).
O2–V1–O1
O3–V1–O1
O4–V1–O1
O6–V1–O1
O4–V1–O2
O5–V1–O2
81.82(10)
82.40(11)
87.07(11)
81.04(11)
86.27(11)
98.92(13)
O6–V1–O2
O4–V1–O3
O5–V1–O3
O6–V1–O3
O5–V1–O4
O6–V1–O5
90.59(12)
87.33(11)
97.44(13)
92.49(12)
100.12(14)
91.78(14)

B.M. Gray et al. / Polyhedron 29 (2010) 1630–1638
1637
identified as a cationic vanadyl (VIV) complex of the diphosphine
4. Conclusions
dioxide [VO(H2O){o-C6H4(P(O)Me2)2}2]Cl2ꢀ3H2O, formed through
a sequence of hydrolysis and oxidation reactions. The vanadium
is six-coordinate, bonded to one V@O (1.601(3) Å), two chelating
diphosphine dioxides (V–O = 1.992(2)–2.119(3) Å) which are dis-
posed cis with chelate angles (87.3(1) and 81.8(1)°). The coordina-
tion sphere is completed by a water molecule (the H’s were readily
identified in the electron density map) with V–OH2 = 2.045(3) Å.
The V@O is slightly longer than that in the square pyramidal [VO-
Cl2(OPPh3)2] (1.584(5) Å) [44]. The IR spectrum shows a strong
V@O stretch at 995 cmꢁ1 and several PO stretches, while the UV–
Vis spectrum shows weak d–d transitions in the visible region
and the onset of charge transfer bands > ꢂ25 000 cmꢁ1, typical of
vanadyl complexes containing oxygen donor ligands [38].
The formation of tertiary arsine adducts of VCl4 has been con-
firmed, contrasting with the discredited reports of phosphine ana-
logues. Adducts of VCl3 have also been prepared as reduction
products of the same reactions, including the first structurally
authenticated VIII arsine [V2Cl6{o-C6H4(AsMe2)2}2]. Hydrolysis of
the VIV complexes proceeds via vanadyl–arsine complexes, which
can be obtained pure by reaction of [VOCl2(thf)2(H2O)] with the li-
gands. In contrast, the very strongly coordinating diphosphine, o-
C6H4(PMe2)2, instantly reduces VCl4 even at low temperatures.
The different behaviour of the phosphine and arsine ligands re-
flects the stronger reducing power of the former. However, the
vanadyl diphosphine complex [VOCl2{o-C6H4(PMe2)2}], is readily
obtained showing the stability conferred upon the VIV centre by
the V@O linkage. The VIV complexes undergo complex decomposi-
tion in thf solution exposed to air, the final products being identi-
fied in the case of the diphosphine as a vanadyl diphosphine
dioxide, [VO(H2O){o-C6H4(P(O)Me2)2}2]Cl2, whereas [VCl4{o-
C6H4(AsMe2)2}x] decompose with chlorination of the arsenic ligand
3.5. Hydrolysis of VIV arsine complexes
Comparison of the IR and UV–Vis spectra of [VOCl2{j
2-MeC-
(CH2AsMe2)3}(H2O)] (above), with those obtained from the green
solids made by reacting VCl4 and MeC(CH2AsMe2)3 in ‘‘laboratory
grade” CCl4 without taking any precautions to exclude moisture,
to the cation [o-C6H4(AsMe2Cl)(l
-O)(AsMe2)]+, and cis-[VOCl2-
(H2O)3] is also produced.
and also by exposing solid [VCl4{j
2-MeC(CH2AsMe2)3}] briefly to
air, exhibit similar features, showing that [VOCl2{MeC(CH2As-
Me2)3}(H2O)] is a significant component of the products. However,
the products are not obtained in a pure state by hydrolysis, and
prolonged exposure to air resulted in blue oils. The [VCl4{o-
C6H4(AsMe2)2}n] (n = 1 or 2) also become green in moist air and
eventually blue oils result. When either [VCl4{o-C6H4(AsMe2)2}n]
(n = 1 or 2) are stirred in thf solution exposed to air, the initial
brown solutions turn green and then blue, and removal of the sol-
vent, followed by washing the sticky blue residues with diethyl
ether affords blue powders which are, on the basis of their IR spec-
tra, assigned as VOCl2 with water or thf as co-ligands, and do not
contain any arsenic ligands. Blue crystals have been obtained on
several occasions from the reaction solutions, but mostly gave very
weak diffraction patterns. In one case the structure of a deep blue
crystal (Fig. 6) showed it to contain co-crystallised oxidised/halo-
Acknowledgements
We thank RCUK and EPSRC for support, STFC for access to the
GEM diffractometer at ISIS through the GEM Express service
(XB990042), and Dr R. I. Smith for collecting the PND data.
Appendix A. Supplementary material
CCDC 757918, 757919, 757920, 757921, and 757922 contain
the supplementary crystallographic data for compounds. These
data can be obtained free of charge via http://www.ccdc.cam.ac.
uk/conts/retrieving.html, or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary
data associated with this article can be found, in the online version,
at doi:10.1016/j.poly.2010.02.003.
genated diarsine cation [o-C6H4(AsMe2Cl)(l
-O)(AsMe2)]+ and cis-
[VOCl2(H2O)3]. The latter is a distorted octahedral molecule with
cis chlorines, a short V@O (1.588(2) Å) and three facially bound
water molecules with the longest V–OH2 trans to the vanadyl unit.
Although [VOCl2ꢀxH2O] (x usually unspecified) is a well known
starting material [1] and there are several structurally authenti-
cated adducts of [VOCl2(H2O)2], this seems to be the first structural
characterisation of the tris(aquo) species The bond lengths are all
slightly longer than in the five-coordinate [VOCl2(H2O)2]ꢀ2Et2O
(which also has trans Cl’s) [30] or [VOCl2(H2O)2ꢀL] (L = 15-crown-
5 or 18-crown-6) [45,46], and the nearest analogue is mer-cis-
[VOCl2(MeOH)3] [30]. The previously unknown organoarsenic(V)
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1
[o-C6H4(AsMe2Cl)(l-O)(AsMe2)]2[VOCl4]. C20H32As4Cl6O3V, RMM = 883.78,
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b = 8.6904(10), c = 22.132(4) Å, b = 98.254(10)°, U = 1570.3(4) Å3. k = 0.71073 Å,
18 278 reflections measured, 3 596 unique reflections, Rint = 0.033. R1
[Io > 2r(Io)] = 0.030, wR2 (all data) = 0.065.

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