Hetero-alkoxide group (IV) and (V) neo-pentoxide compounds.: Syntheses, characterizations, and X-ray structures of [Zr(μ-OCHMe2)(OCH2CMe3)3(HOCH2CMe3)]2 and [Ta(μ-OCH2Me)(OCH2CMe3)4]2

The alcoholysis exchange between excess HONp and [Zr(OPri)(4)(HOPri)](2) or "Ta(OEt)(5)" led to isolation of the mixed-alkoxide compounds [Zr(mu-OPri)(ONp)(3)(HONp)](2) (1) and [Ta(mu-OEt)(ONp)(4)](2) (2), respectively. Compounds 1 and 2 were found to adopt an edge-shared bioctahedral geometry, [M(mu-OR')(OR)(5)](2), with the smaller ligands acting as the bridge between the two metal centers. For 1, the octahedral geometry around the metal center is completed by the coordination of a HONp solvent molecule. The solid state structure of 1 was retained in saturated solutions but at lower concentrations, dynamic behavior associated with a mononuclear-dinuclear equilibrium was observed. For 2, at low concentrations an equilibrium between mononuclear and dinuclear complexes was noted; however, at higher concentrations a dinuclear-higher-nuclearity equilibrium was noted.