Structural study of zirconium and hafnium oxoalkoxides

The results of the X-ray diffraction study of two oxoalkoxides, Zr3O(OBu-t) (10) (I) and Hf6O2(OEt)(20)(EtOH)(2) (II), are reported. Crystallization of I occurs after the prolonged storage of the electrolyte obtained by the an odic dissolution of metal Zr in t-BuOH dissolved in acetonitrile, Crystals of II were grown from the toluene solutions of the product formerly known a s 'hafnium ethoxide'. The central core of the Zr-3(mu(3)-O)(mu(3)-OBu-t)(mu -OBu-t)(3)(OBu-t)(6) molecule features the [Zr-3] triangle, which may be re garded as three [ZrO6] fused via common faces. Molecule Hf-6(mu(3)-O)(2)(mu -OEt)(8)(OEt)(12)(EtOH)(2) is a kind of 'doubled' hafnium analog of I; its central core representing the 12-membered cycle with the alternating Hf ato ms and the O atoms of the bridging Oft groups. Each of the two mu(3)-OXO at oms is bonded to three neighbouring hafnium atoms on either side of the rin g, thus forming two [Hf3O] triangles linked to each other via two four-memb ered [Hf2O2] cycles, involving two pairs of bridging Oft groups. The struct ures of the products of partial decomposition of alkoxides involving the tr iangular [M-3(mu(3)-O)] fragments confirm our earlier assumption about the structure of the oxocomplexes actually existing in the species formerly kno wn as unsolvated 'M(OR),(4)'. (C) 1999 Elsevier Science Ltd. All rights res erved.