Organometallic oxides:: Preparation and properties of the clusters [(η-C5Me5)V(μ3-O)]4 and [(η-C5Me5)V]4(μ-O)6 by reductive aggregation of (η-C5Me5)VCl2(O)

Reduction of Cp*VCl2(O) (Cp* = eta-C5Me5) by the powerful reductants sodium, potassium, magnesium, or calcium or the amalgams of these metals gave a mixture of the black cubane-like cluster [Cp*V(mu(3)-O)](4) and the black-green adamantane-like cluster [Cp*V](4)(mu-O)(6). A concurrent coproduct of the formation of [Cp*V](4)(mu-O)(6) was dark purple [Cp*V(mu-Cl)(2)](3). The formation of [Cp*V]4(mu-O)(6) was favored in toluene, whereas [Cp*V(mu(3)-O)](4) was favored in tetrahydrofuran. The identity of the reductant did not influence the ratio of [Cp*V]4(mu-O)(6) to [Cp*V(mu(3)-O)](4) produced. A scheme for the reduction is proposed; the key intermediate is [Cp*VClO](2). The cluster [Cp*V(mu(3)-O)](4) was paramagnetic (mu(eff) = 2.35 mu(B) at 300 K), and [Cp*V]4(mu-O)(6) was diamagnetic. The syntheses of [Cp*VCl(O)](2)(mu-O) by treatment of Cp*VCl2(O) with Ag2CO3 and [Cp*VCl(mu-O)](4) (which is paramagnetic, mu(eff) = 4.51 mu(B) at 300 K) by reduction of Cp*VCl2(O) with mercury are reported.