Zirconium mixed ligand isopropoxide/aminoalkoxide complexes: crystal structures of [Zr2(OPri)6(L)2] and [Zr2(OBut)3(bdmap)4(OH)] {where L = dmap, 1-dimethylaminopropan-2-olate and bdmap, 1,1-bis(dimethylamino)propan-2-olate}

Abstract

The reactions of the homoleptic zirconium alkoxides [Zr₂(OPrⁱ)₈(PrⁱOH)₂] and Zr(OBu^t)₄ in n-hexane suspensions or solutions with two equivalents of the aminoalcohols 2-dimethylaminoethanol (Hdmae), 1-dimethylaminopropan-2-ol (Hdmap), or 1,1-bis(dimethylamino)propan-2-ol (Hbdmap) have been studied. Products with the formula [Zr(OR)₂(dmae)₂] (R = Prⁱ 1 or Bu^t 2), [Zr₂(OPrⁱ)₆(L)₂] (L = dmap 3 or bdmap 4), and [Zr₂(OBu^t)₃(bdmap)₄(OH)] 5 have been isolated. Compounds 3 and 4 have been shown by single crystal X-ray crystallography to be asymmetric binuclear complexes in the solid state. The two metal centres are bridged via the two aminoalkoxide oxygen atoms and one isopropoxide ligand. The remaining co-ordination spheres of the binuclear molecules are completed by 3 terminal isopropoxide ligands on one metal centre, and 2 terminal isopropoxide ligands on the other. Compound 5 was found to be binuclear, but instead of a µ-isopropoxide bridge a µ-OH group was observed which intramolecularly hydrogen bonds to one of the free NMe₂ groups on a terminal bdmap ligand. The remaining sites in the co-ordination spheres are filled by 3 terminal tert-butoxide ligands on one metal centre and two terminal aminoalkoxide ligands on the other. These are the first binuclear 6/7 co-ordinate zirconium compounds. The structural studies are helpful in understanding the behaviour of these and related complexes as precursors in the MOCVD of ZrO₂ films.