Synthesis and characterization of 8-quinolinolato vanadium(IV) complexes

Article abstract of DOI:10.1016/j.ica.2009.02.025

Reaction of vanadium(III) chloride with 8-quinolinol (Hqn) gave a mononuclear vanadium(IV) complex, [VOCl₂(H₂O)₂] 1) · 2H₂qn · 2Cl · CH₃CN, and three dinuclear vanadium(IV) complexes: [V₂O<

Full text of DOI:10.1016/j.ica.2009.02.025

Inorganica Chimica Acta 362 (2009) 3201–3207
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Inorganica Chimica Acta
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Synthesis and characterization of 8-quinolinolato vanadium(IV) complexes
Kentaro Takano a, Yukinari Sunatsuki b, Masaaki Kojima b, Isamu Kinoshita c, Takashi Shibahara a,
*
a Department of Chemistry, Okayama University of Science, Ridai-cho, Okayama 700-0005, Japan
b Department of Chemistry, Okayama University, Tsushimanaka, Okayama 700-8530, Japan
c Department of Chemistry, Osaka City University, Sugimoto, Sumiyoshi, Osaka 558-8585, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of vanadium(III) chloride with 8-quinolinol (Hqn) gave a mononuclear vanadium(IV) complex,
[VOCl2(H2O)2] 1) ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, and three dinuclear vanadium(IV) complexes: [V2O2Cl2
(qn)2(H2O)2] (2) ꢀ Hqn, [V2O2Cl2(qn)2(C3H7OH)2] (3), and [V2O2Cl2(qn)2(C4H9OH)2] (4). Reaction of vana-
dium(III) chloride with 5-chloro-8-quinolinol (HClqn) gave four dinuclear vanadium(IV) complexes:
[V2O2Cl2(Clqn)2(H2O)2] (5) ꢀ 2HClqn, [V2O2Cl2(Clqn)2(C3H7OH)2] (6), [V2O2Cl2(Clqn)2(C6H5CH2OH)2] (7),
and [V2O2Cl2(Clqn)2(C4H9OH)2] (8) ꢀ 2C4H9OH. Reaction of vanadium(III) chloride with 5-fluoro-8-quino-
linol (HFqn) gave two dinuclear vanadium(IV) complexes: [V2O2Cl2(Fqn)2(H2O)2] (9) ꢀ HFqn ꢀ 2H2O and
V2O2Cl2(Fqn)2(C3H7OH)2] (10). X-ray structures of 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7, 8 ꢀ 2 t-BuOH, and
10 have been determined. As to the mononuclear species 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, coordination of Hqn
to vanadium does not occur, but protonation to Hqn occurs to give H2qn+, which links 1’s through hydro-
gen bonding, while each of the dinuclear species has a terminal and a bridging qn (or Clqn, Fqn) ligand,
giving rise to a (V–O)2 ring. Magnetic measurements of 3, 4, 6, 7, and 10 in solid form show very weak
antiferromagnetic behavior, and the effective magnetic moments are close to spin only value (2.44) of
d1–d1 system, while ESR of 3 in THF shows dissociation to monomeric species. Change from mononuclear,
1, to dinuclear, 2, species was followed by the change of electronic spectrum.
Received 19 December 2008
Accepted 18 February 2009
Available online 28 February 2009
Keywords:
Vanadium complexes
8-Quinolinol
X-ray structures
Magnetic measurements
ESR
Electronic spectra
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
(H2O)2]. As for V(IV) complexes containing other ligands than 8-
quinolinol, several magnetic [11–14] and ESR [15] properties have
8-Quinolinol (Hqn = C9H7NO) and its derivatives have been
widely used as analytical reagents [1]; however, research on vana-
dium complexes with 8-quinolinol ligands or its derivatives is
almost all on V(V). Guastini and coworkers reported the inter-con-
version scheme of 8-quinolinolato vanadium(V) complexes
(Scheme 1) [2], where [VO(OH)(qn)2] is the starting material,
whose blue color in chloroform turns red due to the formation of
[VO(OR)(qn)2] [3–5] with coordinated ORꢁ by the addition of
ethanol (ROH). Dimerization of [VO(OR)(qn)2] gives oxo-bridged
dinuclear vanadium(V) species [6]. On the other hand, reports on
8-quinolinolato-V(III) or -V(IV) complexes are very limited (Chart
1), and [VIII(qn)3] (Chart 1b) [7] and [V2IVO2(qn)4] [8] are the only
complexes so far reported, with the structure of the latter being
determined by elemental analysis and IR spectroscopy. As to V(IV)
complexes with derivatives of 8-quinolinolate ligands, [VIVO
(Meqn)2] (Chart 1d) [9] and [VIVO(L)2] [10] (Chart 1e) were reported.
We report here the syntheses, X-ray structures, and character-
ization of dinuclear vanadium(IV) complexes with 8-quinolinol
ligands obtained by the reaction of vanadium(III) chloride with
8-quinolinol via a mononuclear vanadium(IV) complex [VOCl2
been reported together with their X-ray structures. In addition, a
simpler complex [VOCl2(H2O)2] containing diethylether [16] or
crown ether [17,18] has been reported.
2. Experimental
2.1. Materials and reagents
All the commercially available chemicals were used as received:
VCl3, Aldrich; 8-hydroxyquinoline (Hqn), nacalai Tesque; acetoni-
trile, nacalai Tesque; benzyl alcohol, nacalai Tesque; iso-propanol,
nacalai Tesque; t-butanol, nacalai Tesque; 5-fluoro-8-hydroxy-
quinoline (HFqn), Tokyo Kasei; 5-chloro-8-hydroxyquinoline
(HClqn), Merck.
2.2. Syntheses
[VOCl2(H2O)2] ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN (1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN).
Method 1. Dissolving VCl3 (20.1 mg, 1.28 ꢂ 10ꢁ4 mol) in a mix-
ture of acetonitrile (10 mL) and water (0.05 mL) by heating for
15 min at ca. 60 °C gave a pale dark-green solution, which was
cooled to room temperature. Addition of Hqn (37.2 mg,
2.56 ꢂ 10ꢁ4 mol, Hqn/V = 2) to the solution resulted in a series of
* Corresponding author.
E-mail address: shiba@chem.ous.ac.jp (T. Shibahara).
0020-1693/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2009.02.025

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K. Takano et al. / Inorganica Chimica Acta 362 (2009) 3201–3207
were taken out of the mother liquid under a dinitrogen atmo-
R-OH [3]
sphere: yield, 35.2 mg (48%).
Method 2. A similar procedure to that described in method 1
gave a pale-green solution: the only difference was the use of conc.
HCl (0.05 mL) instead of water (0.05 mL). Standing the resultant
solution for one day gave very pale-blue, plate-like crystals of
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN: yield 37.6 mg (51%).
OH-
H+
O
O
O
qn2V
qn2V
OH
O
O
O
OH- H2O
[V2O2Cl2(qn)2(H2O)2] ꢀ Hqn (2 ꢀ Hqn). A similar procedure to that
described in method 1 for the synthesis of 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN
were followed: only the amount of water was increased from
0.05 mL to 0.15 mL. From the resultant pale-green solution, pale-
green, thin-layered crystals of 2 ꢀ Hqn were deposited in an hour:
yield, 19.0 mg (36%). Anal. Calc. for C27H23Cl2N3O7V2: C, 48.09; H,
3.44; N, 6.23. Found: C, 48.24; H, 3.64; N, 6.22%.
[6]
V
V
OH-
OR
qn2 qn2
R-OH
O
qn2V
O
(CH3CO)2O
-R2O
[4]
qn2V
[5]
O
O
[V2O2Cl2(C9H6NO)2(C3H7OH)2] (3). Similar procedures to those
for the synthesis of 2 ꢀ Hqn were followed: except for the fact
that under dinitrogen atmosphere, iso-propanol (10 mL) was
added immediately after the addition of Hqn (Hqn/V = 2). Pale-
green, thin-layered crystals of 3 were obtained by slow air oxi-
dation through keeping the solution in a loosely sealed vessel
for several days: yeild, 18.3 mg (47%). Anal. Calc. for
C24H28Cl2N2O6V2: C, 47.00; H, 4.60; N, 4.57. Found: C, 46.98;
H, 4.34; N, 4.52%.
Scheme 1. 8-Quinolinolate vanadium(V) complexes.
0
O
N
O
N
V
O
O
N
V
O
O
N
O
N
O
V
N
O
N
OH
N
[V2O2Cl2(qn)2(C4H9OH)2] (4). Similar procedures to those for
the synthesis of 3 were followed: t-butanol was used instead of
iso-propanol:
yield:
14.98 mg
(37%).
Anal.
Calc.
for
a) Hqn
IIIqn3
b) V
[V O (qn) ]
c)
2
2
4
C26H32Cl2N2O6V2: C, 48.69; H, 5.03; N, 4.37. Found: C, 48.61; H,
4.74; N, 4.33%.
[V2O2Cl2(C9H5ClNO)2(H2O)2] ꢀ (C9H6ClNO)2 (5 ꢀ 2HClqn). Similar
procedures to those for the synthesis of 2 ꢀ Hqn were followed:
HClqn was used instead of Hqn: yield: 34.39 mg (56%). Anal. Calc.
for C36H26Cl6N4O8V2: C, 45.17; H, 2.74; N, 5.85. Found: C, 44.97;
H, 2.89; N, 5.86%.
O
N
O
O
N
N
O
O
V
S
N
O
V
S
[V2O2Cl2(C9H5ClNO)2(C3H7OH)2] (6). Similar procedures to
those for the synthesis of 3 were followed: HClqn was used in-
stead of Hqn: yield: 20.38 mg (47%). Anal. Calc. for
C24H26Cl4N2O6V2: C, 42.26; H, 3.84; N, 4.11. Found: C, 42.17; H,
3.74; N, 4.11%.
d) [VIVO(Meqn)2]
e) [VIVO(L)2]
Chart 1.
[V2O2Cl2(C9H5ClNO)2(C6H5CH2OH)2] (7). Similar procedures to
those for the synthesis of 3 were followed: HClqn and benzyl alco-
hol were used instead of Hqn and iso-propanol, respectively: yield:
26.85 mg (54%). Anal. Calc. for C32H26Cl4N2O6V2: C, 49.39; H, 3.37;
N, 3.60%. Found: C, 49.52; H, 3.36; N, 3.56(3.60).
color changes: red ? orange ? green ? pale-green in ca. one min-
ute. Standing the resultant solution for half an hour gave very pale-
blue, plate-like crystals of 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN. As the crystals
are very hygroscopic and become liquefied in a few seconds, they
Table 1
Crystallographic data.
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN
3
4
6
7
8 ꢀ 2 t-BuOH
10
Formula
F.W.
C20H23Cl4N3O5V
578.17
C24H26Cl2N2O6V2
611.27
C26H32Cl2N2O6V2
641.34
C24H24Cl4N2O6V2
680.16
C32H26Cl4N2O6V2
778.26
C34H50Cl4N2O8V2
858.47
C24H20Cl2F2N2O6V2
643.22
Crystal System
Space Group
a (Å)
b (Å)
c (Å)
monoclinic
P21/m (#11)
7.599(3)
20.875(8)
7.719(3)
91.235(4)
1224.2(8)
2
monoclinic
P21/n (#14)
9.978(15)
16.23(2)
16.51(2)
105.06(3)
2582(6)
4
monoclinic
C2/c (#15)
16.609(8)
10.412(5)
16.418(8)
91.090(5)
2839(2)
4
monoclinic
P21/c (#14)
9.004(5)
15.873(9)
20.049(11)
98.478(9)
2834(3)
4
monoclinic
C2/c (#15)
28.688(10)
7.572(2)
18.157(5)
127.964(4)
3109.8(16)
4
trigonal
R3 (#148)
monoclinic
P21/n (#14)
8.407(6)
16.019(11)
19.933(14)
98.691(12)
2653(3)
4
ꢀ
31.730(17)
31.730(17)
10.442(4)
90.000
9105(8)
9
b (°)
V (Å3)
Z
Dcalc (g/cm3)
1.568
8.777
1.572
9.725
1.501
8.884
1.594
10.771
1.662
9.935
1.409
7.736
1.610
9.613
l
(Mo K
a
) (cmꢁ1
)
Reflections collected
Unique reflections
13998
3566
24750
5821
15863
4129
27710
6333
17243
4496
35245
5865
29478
7708
[R(int)
]
0.098
0.066
0.046
0.099
0.069
0.039
0.031
Goodness-of-fit (GOF)
1.005
1.064
0.996
0.994
0.990
1.069
1.060
R1 (I > 2.00
R; wR2
r
(I))
0.0428
0.0495;0.1016
0.1048
0.1429; 0.2463
0.0311
0.0341; 0.0885
0.0952
0.1442; 0.2538
0.0346
0.0450; 0.0881
0.0436
0.0512; 0.0954
0.0409
0.0477; 0.1098
P
P
R1
=
||Fo| ꢁ |Fc||/ |Fo|.
P
P
2
2 1=2
wR2 ¼ ½ ðwðF2o ꢁ Fc2Þ Þ= wðF2oÞ ꢃ
.

K. Takano et al. / Inorganica Chimica Acta 362 (2009) 3201–3207
3203
O
V
+
N
OH H
-
AN
1
2
2
Cl
H2O
Cl
Cl OH2
0
0
L
L
O
O
L = H2O, 5
Cl
Cl
Cl
N
V O
L = H2O, 2
N
N
V O
L = i-PrOH, 6
L = C6H5CH2OH, 7
L = t-BuOH, 8
L = i-PrOH, 3
L = t-BuOH, 4
O
V N
O
V N
Cl
Cl
Cl
O
O
L
L
0
L
O
Cl
F
V O
L = H2O, 9
L = i-PrOH, 10
O
V N
F
Cl
O
L
Chart 2. 8-Quinolinolato vanadium(IV) complexes.
[V2O2Cl2(C9H5ClNO)2(C4H9OH)2] ꢀ 2C4H9OH (8 ꢀ 2 t-BuOH) Sim-
ilar procedures to those for the synthesis of 3 were followed: HClqn
and benzyl alcohol were used instead of Hqn and t-butanol, respec-
tively: yield: 23.51 mg (47%). Anal. Calc. for C34H50Cl4N2O8V2: C,
47.57; H, 5.87; N, 3.26. Found: C, 47.41; H, 5.80; N, 3.39%.
[V2O2Cl2(C9H5FNO)2(H2O)2] ꢀ C9H6FNO ꢀ 2H2O(9 ꢀ HFqn ꢀ 2H2O).
Similar procedures to those for the synthesis of 3 were followed:
HFqn was used instead of Hqn: yield: 33.60 mg (69%). Anal. Calc.
for C27H24Cl2F3N3O9V2: C, 42.43; H, 3.17; N, 5.50. Found: C, 42.31;
H, 2.46; N, 5.35%.
3. Results and discussion
Designations of compounds
[VOCl2(H2O)2] ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN
[V2O2Cl2(qn)2(H2O)2] ꢀ Hqn
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN
2 ꢀ Hqn
[V2O2Cl2(qn)2(C3H7OH)2]
3
4
[V2O2Cl2(qn)2(C4H9OH)2]
[V2O2Cl2(Clqn)2(H2O)2] ꢀ 2HClqn
5 ꢀ 2HClqn
[V2O2Cl2(Clqn)2(C3H7OH)2]
6
[V2O2Cl2(C9H5FNO)2(C3H7OH)2] (10). Similar procedures to
those for the synthesis of 3 were followed: HFqn was used instead
of Hqn: yield: 15.88 mg (38%). Anal. Calc. for C24H26Cl2F2N2O6V2: C,
44.40; H, 4.04; N, 4.31. Found: C, 44.48; H, 3.77; N, 4.13%.
[V2O2Cl2(Clqn)2(C7H7OH)2]
7
[V2O2Cl2(Clqn)2(C4H9OH)2] ꢀ 2C4H9OH
[V2O2Cl2(Fqn)2(H2O)2] ꢀ H5Fqn ꢀ 2H2O
[V2O2Cl2(Fqn)2(C3H7OH)2]
8 ꢀ 2 t-BuOH
9 ꢀ HFqn ꢀ 2H2O
10
2.3. X-ray crystallography and solution of structures
Structural determinations of 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7,
8 ꢀ 2 t-BuOH, and 10. Data were collected on a Rigaku/MSC Mercury
CCD diffractometer. Suitable crystals were attached to the tip of a
glass capillary using silicone grease and transferred to the goniostat,
where they were cooled for data collection, using graphite mono-
3.1. Syntheses and electronic spectra
Reaction of vanadium(III) chloride with 8-quinolinol (Hqn), 5-
chloro-8-quinolinol (HClqn), or 5-fluoro-8-quinolinol (HFqn) gave
one mononuclear vanadium(IV) complex and eight dinuclear vana-
dium(IV) complexes listed below, and X-ray structures of
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7, 8 ꢀ 2 t-BuOH, and 10 have suc-
cessfully been determined (Chart 2). No X-ray structures of mono-
meric and dimeric V(IV) complexes with qn ligands have been
reported so far.
chromatedMoKaradiation. Thestructuresweresolvedusingacom-
bination of Patterson method (DIRDIF99 PATTY) [19], and all the
remaining non-hydrogen atoms were located from difference Fou-
rier maps [20]. The hydrogen atoms of 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 4, 7,
8, and 10 were located from difference Fourier maps, and their posi-
tions were fixed. Those of 3 and 6 were located at calculated posi-
tions. All of the isotropic thermal parameters of hydrogen atoms
were constrained to 1.2Ueq to which they were attached. The pro-
gram package Crystal Structure [21] was used, SHELXL being used for
the refinement. Crystallographic data are summarized in Table 1.
0.6
0.4
0.2
0
2.4. Measurements
Electronic spectra were measured using a Hitachi U-2000 dou-
ble-beam spectrophotometer. X-ray diffraction data were collected
with a Rigaku CCD diffractometer and analyzed using the teXsan
System. Elemental analyses were determined with a Perkin–Elmer
240 NCH analyzer. Variable-temperature magnetic susceptibility
measurements of 3, 4, 6, 7, and 10 were carried out on powdered
samples on an MPMS XL5 SQUID magnetometer in the range of
1.9–300 K in a 1 T applied field. The diamagnetic corrections were
carried out using Pascal’s constant [22]. ESR spectrum was
obtained for a solution of 3 in THF with a JEOL JES-FE2XG
spectrometer.
400
600
800
1000
Wavelength/nm
Fig. 1. Electronic spectral change in the course of the reaction from
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN to 2 ꢀ Hqn in acetonitrile (every 5 min).

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K. Takano et al. / Inorganica Chimica Acta 362 (2009) 3201–3207
The reaction of VCl3 with Hqn in acetonitrile–water or acetoni-
3.2. X-ray structures
trile–concentrated HCl gives mononuclear V(IV) species 1, which
turns to dinuclear V(IV) species 2, when coordination of qnꢁ oc-
curs. Smaller amounts of water and higher acidity retard the reac-
tion rate from 1 to 2. Probably deprotonation of H2qn+ is one of the
important processes. 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN is very hygroscopic
and becomes liquefied within a few seconds when the crystals
are taken out of the mother liquid in the air, and therefore the com-
position is according to that determined by X-ray crystallography.
Electronic spectral change of 1 to 2 was observed by dissolving
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN in acetonitrile under dinitrogen atmo-
sphere (Fig. 1). Further oxidation of 2 proceeds to give V(V) species
in the air (Fig. 2), but the rate is low and any air-free technique is
required to obtain crystals of 2.
Addition of propanol or butanol in the synthesis of 2 ꢀ Hqn
results in the formation of alcohol-coordinated species
[V2O2Cl2(qn)2(ROH)2] (R = C3H7, 3; C4H9, 4), respectively, which
are air-oxidized to give V(V) species much more easily than the
water-coordinated complex 2, and a mild air-free condition is re-
quired for the isolation of 3 and 4; leaving the solution containing
the crystals of iso-propanol-coordinated species 3 for a few days
longer causes resolution of the deposited crystals and change of
color of the solution from pale-green to dark red. This indicates
the formation of V(V) complex [3–5]. The use of HClqn (5, 6, 7,
and 8) or HFqn (9 and 10) instead of Hqn gave respective
complexes.
ORTEP drawings of 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7, 8, and 10
are shown in Fig. 3. Atomic distances are listed in Tables 3 and
4, respectively. Fig. 3a. 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN shows that
a
crystallographic mirror plane passes through V1, O1, O2, O3,
C21, C22, N21, and H221. A feature of this compound is that
coordination of Hqn to vanadium does not occur; however, pro-
tonation to Hqn occurs to give H2qn+, which is linked to [VOCl2-
(H2O)] through hydrogen bonding: H10ꢀ ꢀ ꢀCl2, 2.32 Å; Cl2ꢀ ꢀ ꢀH2,
2.15 Å.
X-ray structures of five compounds containing the mononuclear
vanadium complex, [VOCl2(H2O)] (1), have been reported so far:
1 ꢀ 2Et2O [16], 1 ꢀ 15-crown-5 [17], 1 ꢀ benzo-15-crown-5 [17],
1 ꢀ 18-crown-6 [18], and 1 ꢀ 2C10H10N3 ꢀ Cl2 (C10H10N3 = bis{2-
(2-pyridylamino)pyridinium}) [23], where diethyl ethers (in the
former four complexes) connect 1’s through hydrogen bonding,
which cause interaction between the complexes. The dimensions
of 1 in 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN are not so different from those of
the reported complexes (see Table 4).
Complexes 3, 4, 6, 7, 8, and 10 are dimeric species having four
membered anti-coplanar (V–O)2 rings. Possible structures of
[VO(l
-OR)2VO]2+ are shown in (Chart 3). Crystallographic (4, 7,
and 8) or pseudo crystallographic (3, 6, and 10) centers of symme-
try reside on the centers of the rings. The V–O distances trans to
the terminal oxo ligands are substantially longer than those cis
to the terminal oxo ligands (Table 3) due to V@O trans effect.
The V–V distances will be discussed in the magnetic properties sec-
tion below.
Electronic spectral data of 1–10 are shown in Table 2. Electronic
spectral change of 1 to 2 was observed by means of dissolving
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN in acetonitrile under dinitrogen atmo-
sphere (Fig. 1); coordination of 8-quinolinol (Hqn) to 1 gives 2,
which accompanies the peak shift from 720 to 670 nm. Further
electronic spectral change indicates slow air oxidation of 2 ꢀ Hqn
to give V(V) species in acetonitrile (Fig. 2).
3.3. Magnetic properties
The magnetic data of 3, 4, 6, 7, and 10 were treated by applying
the Bleaney–Bowers equation [24] (Eq. (1)), calculated for two
S = 1/2 centers under a 2JS1 ꢂ S2 spin Hamiltonian, using a non-
linear least-squares fitting routine (N
a
, 0.0001).
1.0
0.8
0.6
0.4
0.2
0
ꢀ
ꢁ
2Ng2b2
kT
1
vM
¼
þ N
a;
where x ¼ expðꢁJ=kTÞ
ð1Þ
3 þ x2
The results are summarized in Table 5. The compounds in solid
state are experiencing a very weak antiferromagnetic interaction
between the metal centers, and the effective magnetic moments
are close to spin only value (2.44) of the d1–d1 system. Fig. 4 shows
temperature dependence of magnetic susceptibility of 3. ESR spec-
trum of 3 at 270 K in THF and its simulation (Fig. 5) indicate that
the dimeric species 3 dissociates to give monomeric species; the
g value (2.03) obtained in the solution differs distinctly from that
obtained in solid state (Table 5).
Much discussion has focused on the magnetic properties of
dinuclear oxo-vanadium complexes, and it is suggested that me-
tal–metal interactions of complexes with syn-orthogonal, syn-
coplanar, and twist structures are strong, while those of complexes
with anti-coplanar ones are weak [11,12,13]. The complexes 3, 4, 6,
7, and 10 are of anti-coplanar structure, and the above discussion is
well applied.
400
600
800
1000
Wavelength/nm
Fig. 2. Electronic spectral change in the course of the air oxidation of 2 ꢀ Hqn in
acetonitrile (every 30 min).
Table 2
Electronic spectral data of 1–10 in acetonitrile.
Compound
kmax,
(e )
/Mꢁ1 cmꢁ1
nm
4. Conclusion
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN
355 (6220), 720 (40.4)
372 (5560), 670 (108)
375 (4570), 672 (103)
393 (5960), 675 (113)
375 (4590), 673 (99.3)
390 (5660), 671 (97.5)
401 (6210), 679 (120)
374 (4550), 670 (105)
380 (5490), 672 (98.0)
2
Reaction of vanadium(III) chloride with 8-quinolinol (Hqn) gave
a mononuclear vanadium(IV) complex, 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, and
three dinuclear vanadium(IV) complexes: 2 ꢀ Hqn, 3, and 4. Reac-
tion of vanadium(III) chloride with 5-chloro-8-quinolinol (HClqn)
gave four dinuclear vanadium(IV) complexes: 5 ꢀ 2HClqn, 6,
7, and 8 ꢀ 2 t-BuOH. Reaction of vanadium(III) chloride with 5-flu-
oro-8-quinolinol (HFqn) gave two dinuclear vanadium(IV)
3
4
6
7
8 ꢀ 2C4H9OH
9
10

K. Takano et al. / Inorganica Chimica Acta 362 (2009) 3201–3207
3205
complexes: 9 ꢀ HFqn ꢀ 2H2O and 10. X-ray structures of 1 ꢀ
2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7, 8 ꢀ 2 t-BuOH, and 10 have been
determined. All the dinuclear complexes reported here have
(V–O)2 rings.
Magnetic measurements of 3, 4, 6, 7, and 10 in solid state show
very weak antiferromagnetic behavior, and the effective magnetic
moments are close to spin only value (2.44) of the d1–d1 system,
while ESR of 3 in THF shows dissociation to monomeric species.
Fig. 3. ORTEP drawings of 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7, 8 ꢀ 2C4H9OH, and 10 with thermal ellipsoids at 50% probability (see text). Uncoordinated t-butyl alcohol molecules
in 8 are omitted for clarity.

3206
K. Takano et al. / Inorganica Chimica Acta 362 (2009) 3201–3207
Table 3
Selected bond lengths (Å) for 1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7, 8 ꢀ 2C4H9OH, and 10.
1
3
4
6
7
8 ꢀ 2 t-BuOH
10
V–N
2.09[1]
2.13[2]
1.99[1]
3.349(2)
2.370[6]
1.592[5]
130.0[2]
107.25[4]
2.103(1)
2.102[7]
2.164[5]
1.9855[3]
3.338(2)
2.368[4]
1.585[6]
123.9[9]
107.0[2]
2.112(1)
2.182(2)
1.999(1)
3.3537(5)
2.3677(5)
1.604(2)
126.5(2)
106.57(4)
2.107(2)
2.178(1)
1.999(1)
3.3778(3)
2.3761(5)
1.596(1)
131.4(1)
107.85(6)
2.103[2]
2.158[4]
1.9913[5]
3.3392(3)
2.371[1]
1.5935[7]
129.1[4]
107.1[2]
V–Oa
2.1809(8)
1.9956(8)
3.3860(2)
2.3721(3)
1.5953(8)
139.53(7)
108.25(3)
V–Ob
V–V
V–Cl
2.3085(9)
1.576(2)
V@O
\V–Oc–C
\V–Od–V
a
Oxygen of qn trans to terminal oxygen.
Oxygen of qn cis to terminal oxygen.
Oxygen of alcohol.
b
c
d
Oxygen of qn.
Table 4
Selected bond lengths (Å) and angles (°) of [VOCl2(H2O)2] (1).
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CNa
1 ꢀ Et2Ob
1 ꢀ 15C5c
1 ꢀ B15C5d
1 ꢀ 18C6e
1 ꢀ 2C10H10N3 ꢀ Cl2
f
V@O
1.576(2)
2.3085(9)
2.011[1]
106.18(2)
105.5[4]
147.64(2)
85.7[1]
1.574(1)
2.318[5]
1.997(1)
105.78[3]
106.32(3)
148.4(1)
85.6[1]
1.570(2)
2.3050[7]
2.005[2]
108.7[4]
103.4[1]
142.73(4)
85.8[2]
1.567(3)
2.299[5]
2.022[5]
107.6[1]
103.1[2]
144.80(5)
86.1[3]
1.568(3)
2.31[2]
2.00[2]
105.0[2]
103.7[2]
150.1(3)
86.5[7]
1.5719(19)
2.310[5]
1.977[1]
104.6[7]
106.5[3]
150.85(3)
85.90[7]
147.0(1)
7.838
V–Cl
V–Og
Ob–V–Cl
Ob–V–Ob
Cl–V–Cl
Cl–V–Og
Og–V–Og
Vꢀ ꢀ ꢀVh
149.07(9)
7.719
147.36(7)
7.282
153.2(1)
8.206
153.8(1)
7.910
152.3(1)
a
This work.
b
c
d
e
f
Ref. [16].
Ref. [17]: 15C5 = 15-crown-5.
Ref. [17]: B15C5 = benzo-15-crown-5.
Ref. [18]: 18C6 = 18-crown-6.
Ref. [23]: C10H10N3 = bis{2-(2-pyridylamino)pyridinium}.
Coordinated water molecule.
g
h
The shortest Vꢀ ꢀ ꢀV distance.
3
2
1
Ο
Ο
Ο
0.10
0.08
0.06
0.04
0.02
0
Ο R
Ο R
Ο R
Ο R
V
V
V
V
Ο
syn -orthogonal
anti -orthogonal
Ο R
Ο R
Ο
Ο R
V
V
V
V
Ο
Ο
Ο R
Ο
anti -coplanar
syn -coplanar
Ο
Ο
Ο
0
20
40
60
80
100
V
V
Temperature / K
Ο
Fig. 4. Temperature dependence of magnetic susceptibility of 3.
and leff vs. T plot (h), 1 T, 1.9–100 K.
vA vs. T plot (s)
twist
Chart 3. Possible structures of [VO(
l
-OR)2VO]2+
.
A
B
Table 5
Effective magnetic moments, g-, and J-values of 8-quinolinolato dinuclear vana-
dium(IV) complexes.
Complex
leff (300 K)
g
J (cmꢁ1
)
3
10
6
4
7
2.43
2.53
2.49
2.50
2.45
1.89 (2.03a)
2.01
1.94
2.06
2.00
ꢁ2.0
ꢁ0.9
ꢁ0.6
ꢁ0.3
ꢁ0.1
2800
3000
3200
3400
3600
3800
mT
Fig. 5. ESR spectrum of 3: (A) measured at 270 K in THF; (B) the simulated
a
Determined by ESR spectrum.
spectrum.

K. Takano et al. / Inorganica Chimica Acta 362 (2009) 3201–3207
3207
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We thank Miss Michiko Oki for help with the synthesis of some
of the complexes. This work was partly supported by a Special
Grant for Cooperative Research administered by the Japan Private
School Promotion Foundation.
[11] S.L. Castro, M.E. Cass, F.J. Hollander, S.L. Bartley, Inorg. Chem. 34 (1995) 466.
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Appendix A. Supplementary material
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[19] P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, S. Garcia-Granda, R.O.
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Report of the Crystallography Laboratory, University of Nijmegen, The
Netherlands, 1992.
CCDC 711089, 711090, 711091, 711092, 711093, 711094 and
711095 contain the supplementary crystallographic data for
1 ꢀ 2H2qn ꢀ 2Cl ꢀ CH3CN, 3, 4, 6, 7, 8 ꢀ 2C4H9OH and 10. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2009.02.025.
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