Abstract
Two complexes containing both vanadium and lithium, [V6Li10O8(ONep)14{O2Si(Me)2(ONep)}2] (1) and [V(ONep)3(µ-ONep)2Li(thf)2] (2), Nep = neopentyl, Me = methyl and thf = tetrahydrofuran, have been isolated in high yield and characterised by a number of techniques including X-band electron paramagnetic resonance (EPR) and 29Si{¹H} nuclear magnetic resonance (NMR) spectroscopies, magnetic susceptibility measurements and single crystal X-ray diffractometry. Despite the similar preparation conditions, the two products present remarkably distinctive structural features: complex 2is a binuclear adduct of "V(ONep)4" and "Li(ONep)(thf)2", while 1is a mixed-valence, 16-metal aggregate. The large molecular oxoalkoxide 1also contains silanolate units, {OSi(Me2)(ONep)} -, produced by nucleophilic attack of neopentoxide groups on Si-O bonds of silicone grease accidentally dissolved in the reaction media. Both products have promising applications in organic and inorganic synthesis, including the preparation of uncommon V-Li and/or Si containing oxides.
Highlights
The literature on vanadium alkoxide chemistry describes a number of high valence, vanadium(V) compounds prepared from commercially available VOCl3, V2O5,(NH )VO or VO(OR) (R = alkyl)
The five-coordinate V(1) and V(2), in their turn, are supposed to be in the +IV oxidation state. These assignments are based on the inversion symmetry of the molecular assembly and the most common coordination numbers of vanadium(III) and (IV) in O-donor environments.[39]
A number of works have reported the occurrence of redox and/or fragmentation processes in highly reactive systems involving metal alkoxides, Grignard reagents and metal amides.[43,44,45]
Summary
[V(1) and V(2); 1.917(4) Å] is close to the observed for the analogous dimensions in the [V (μ‐ONep) (ONep) ] starting material [mean bond length = 2.012(6) Å],15 as well as for its isopropoxide-containing analogue, [V2(μ‐OPri)2(OPri)6], 2.012(10) Å.11 For the vanadium(III) centre, the average The simulation parameters are in very good agreement with those of the powder spectrum (Table 4), strongly suggesting that the binuclear aggregation revealed for 2 in the solid state (Figure 4) is kept in thf solution.
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