New zirconocene pseudohalogeno complexes. Crystal structure of mu-oxo-bis[bis(cyclopentadienyl)isocyanatozirconium(IV)], [{Zr(eta(5)-C5H5)(2)(NCO)}(2)O]

The isothiocyanato complexes [Zr(eta(5)-C5H4Me)(2)(NCS)(2)] and [Zr(eta(5)-(C5H4Bu)-Bu-t)(2)(NCS)(2)] have been prepared from the corresponding zirconocene dichlorides and KSCN in acetone. Analogous reactions with KOCN or KSeCN, led to the formation of the stable dinuclear ore-bridged complexes [(Zr(eta(5)-C5H5)(2)(NCO))(2)O] and [(Zr(eta(5)-C5H4Me)(2)(NCSe))(2)O], respectively. The molecular structure of [(Zr(eta(5)-C5H5)(2)(NCO)](2)O] has been determined by X-ray diffraction methods and consists of two (eta(5)-C5H5)(2)Zr(NCO) units linked by an oxo bridge. The Zr-O-Zr bridge [angle 165.7(2)degrees] is non linear. The relatively short Zr-O bond lengths of 1.949(3) and 1.942(3) Angstrom support the presence of partial double-bond character. The compound contains N-coordinated cyanato ligands which are almost linear.