Preparation of salts of vanadyl(V) Schiff base complexes,
[VO(L)]؉, by reactions with acids in air
cm3). The initial filtrate was layered with diethyl ether to yield a
further crop of the dark green solid. Yield: 0.60 g, 60%. IR
(KBr disc, cmϪ1): 902s, ν(V᎐O).
᎐
Some new salts of this kind are listed in Table 4, and some
typical preparations are given below. The inclusion of
additional molecules of solvent or acid in some of the formu-
lations below has not been everywhere confirmed, but this
phenomenon has often been found in compounds of this
type. These materials presumably all contain five-co-ordinate
vanadium(), and compounds prepared similarly but contain-
ing co-ordinated solvent and thus six-co-ordinate vanadium()
will be described elsewhere.
(c) Cocrystallisation of vanadium(IV) and vanadium(V) species.
For details of further compounds prepared by this method see
Table 6.
[{VO{salen(5-Me)2}}2][ClO4]. The complex [VO{salen(5-
Me)2}][ClO4] (0.38 g, 0.83 mmol) was dissolved in acetonitrile
(60 cm3), [VO{salen(5-Me)2}] (0.30 g, 0.83 mmol) then added
and the suspension heated under reflux for 1.5 h. The solution
was reduced to dryness, dichloromethane (60 cm3) added, and
the dark green solution heated under reflux for 2 h. Green crys-
tals were isolated by layering the filtrate with diethyl ether and
storing at Ϫ20 ЊC for 7 d. Yield: 0.45 g, 66%. IR (KBr disc,
cmϪ1): 1623s, 1547s, 1276s, 1255s, 1093s (br), 935s and 829s.
[{VO(salibn)}2][ClO4]ؒ2CHCl3. The complex [VO(salibn)]
(1.0 g, 2.8 mmol) was dissolved in acetonitrile (50 cm3),
and perchloric acid (0.36 cm3, 5.5 mmol) added to give an
immediate change to dark blue. The solution was stirred at
room temperature for 5 d, filtered through Celite and reduced
to dryness. The crude [VO(salibn)][ClO4] was used without
further purification or characterisation; 0.93 g (2.01 mmol) was
dissolved in acetonitrile (50 cm3) and [VO(salibn)] (0.73 g, 2.02
mmol) added. The solution was reduced to dryness and chloro-
form (150 cm3) added to give a dark solution, from which a
green powder was isolated after storage at Ϫ20 ЊC for 3 w. This
was then filtered off and washed with diethyl ether (30 cm3).
Yield: 1.13 g, 55%. IR (KBr disc, cmϪ1): 1615s, 1543s, 1446s,
1298s, 1272s, 1098s, 916s, 820s, 805s and 755s.
[VO{salen(5-Br)2}][CF3SO3]. The complex [VO{salen-
(5-Br)2}] (2.65 g, 5.40 mmol) was suspended in acetonitrile
(60 cm3) and triflic acid (0.50 cm3, 5.7 mmol) added to give
an immediate change to dark green. The suspension was stirred
at room temperature for 6 d, and the green solid formed
filtered off and washed with diethyl ether (40 cm3). Yield: 1.69
g, 52%. IR (KBr disc, cmϪ1): 928s ν(V᎐O), 826s, 700s, 690s
᎐
and 639s. Found: C, 33.4; H, 2.0; N, 4.7. C33H24Br4F3N4O9SV
requires C, 35.0; H, 2.1; N, 5.0%.
[VO(salibn)][CF3SO3]. The complex [VO(salibn)] (1.94 g,
5.37 mmol) was dissolved in acetonitrile (60 cm3) to afford a
green-blue solution. Trifluoromethanesulfonic acid (0.47 cm3,
5.31 mmol) was added, and a change to deep blue occurred
immediately. The solution was stirred for 22 h and layered with
diethyl ether. A dark blue crystalline solid was isolated. Yield:
1.59 g, 56% IR (KBr disc, cmϪ1): 964s ν(V᎐O). Found: C, 42.1;
᎐
H, 3.7; N, 5.1. C19H20F3N2O7SV requires C, 44.5; H, 3.9; N,
5.5%. NMR: 1H (400 MHz, CD3CN) δ 1.66 (s, br, 6 H,
2 × CH3), 4.15 (s, br, 1 H, CH), 4.39 (s, br, 1 H, CH), 7.13 (m,
2 H, aryl), 7.34 (m, 2 H, aryl), 7.89 (s, br, 2 H, aryl), 8.02 (m,
2 H, aryl), 9.05 (s, 1 H, CH) and 9.11 (s, 1 H, CH); 19F
(376 MHz, CD3CN) δ Ϫ79.581s; 51V (131.5 MHz, CD3CN)
δ Ϫ586.3s (∆ν1/2 ≈ 200 Hz).
[{VO(salen)}{VO(salnptn)}][BF4].
The
complex
[VO(salen)] (0.46 g, 1.4 mmol) was dissolved in acetonitrile
(100 cm3), [VO(salnptn)][BF4] (0.64 g, 1.4 mmol) added and the
solution heated under reflux for 1.5 h. The solution was reduced
to dryness and the residue taken up in dichloromethane (180
cm3). This solution was then stored at Ϫ20 ЊC for 3 d. A black
crystalline solid was filtered off and washed with diethyl ether
(30 cm3). Yield: 0.90 g, 82%. IR (KBr disc, cmϪ1): 1611s, 1546s,
1446s, 1272s, 1060s (br), 910 and 874s.
Preparation of salts of adducts [VO(L)→VO(L)]؉
[{VO(salnptn)}{VO(salen)}][ClO4]ؒ0.5MeCN. The com-
plex [VO(salen)][ClO4] (1.41 g, 3.3 mmol) was dissolved in
acetonitrile (100 cm3) to afford a blue solution; [VO(salnptn)]
(1.22 g, 3.3 mmol) was added, and the solution heated to reflux
for 2.5 h. The solution was then cooled to room temperature
and kept at Ϫ20 ЊC for several weeks. A black crystalline solid
was isolated and washed with diethyl ether (30 cm3). Yield: 1.83
g, 68%. IR (KBr disc, cmϪ1): 1612s, 1545s, 1447s, 1304s, 1092s
(br), 862s and 764s.
Compounds prepared by iodine oxidation are listed in Table 5,
and those by oxidation in the presence of acids, or by co-
crystallisation, Table 6.
(a) Reactions with iodine. A specimen protocol is given. The
other products are listed in Table 5.
[{VO{salen(3-OMe)2}}2][I3]ؒ0.5MeCN.
The
complex
[VO{salen(3-OMe)2}] (1.07 g, 2.73 mmol) was dissolved in
acetonitrile (50 cm3) and iodine (0.35 g, 1.4 mmol) added. The
solution was heated under reflux for 7 h, and then cooled to
room temperature over a period of several hours. The green
solid was filtered off and washed with diethyl ether (30 cm3).
Yield: 0.95 g, 59%. IR (KBr disc, cmϪ1): 1618s, 1560m, 1262s,
1085s, 859s ν(V᎐O) and 802s.
Acknowledgements
We acknowledge the award of a project studentship from the
EPSRC to N. F. C.
(b) Reactions with acids in air. The following examples illus-
trate the general method.
References
[{VO{salen(5-Cl)2}}2][ClO4]. The complex [VO{salen-
(5-Cl)2}] (0.63 g, 1.60 mmol) was suspended in acetonitrile
(40 cm3) and perchloric acid (0.2 cm3, 3.20 mmol) was added.
The dark green solution was stirred at room temperature for
6 d. A dark green solid was filtered off and washed with diethyl
ether (30 cm3). Yield: 0.30 g, 43%. IR (KBr disc, cmϪ1): 1094s
(br) ν(Cl᎐O) and 898s ν(V–O). MS (FAB): m/z = 401, [M]ϩ,
24%, based on m/z = 55, 100%.
[{VO{salen(5-Cl)2}}2][BF4]ؒ0.5HBF4. The complex [VO-
{salen(5-Cl)2}] (0.86 g, 2.13 mmol) was suspended in aceto-
nitrile (30 cm3), and tetrafluoroboric acid–diethyl ether (0.31
cm3, 2.11 mmol) added. After 24 h at room temperature, a dark
green solid was filtered off and washed with diethyl ether (30
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