Synthesis and characterisation of novel heterobimetallic halide isopropoxides based on M2(OPri)9–(M = Sn, Zr or Ti) anions: crystal and molecular structures of [CdI{Sn2(OPri)9}] and [{SnI[Zr2(OPri)9]}2

Abstract

New heterobimetallic halide isopropoxides based on the interaction of M2(OPri)9–(M = SnIV, ZrIV or TiIV) units with CdII, SnII and PbII have been prepared. These complexes have been characterised by multinuclear solution and solid-state cross polarisation magic angle spinning (CP MAS) NMR spectroscopy, elemental analyses and cryoscopy. Single-crystal X-ray diffraction studies have been performed for [CdI{Sn2(OPri)9}]1 and [{SnI[Zr2(OPri)9]}2]2. Compound 1 consists of a face-sharing bioctahedral Sn2(OPri)9– unit which interacts with the central metal atom, cadmium, using two µ- and two terminal OPri groups. The cadmium atom is within a distorted trigonal bipyramid of oxygen and iodine atoms. The 113Cd chemical shifts in the solution and solid-state CP MAS NMR spectra of 1 are consistent with the retention of its heterometallic nature in solution. In contrast to the monomeric form of 1, compound 2 exists as an iodo-bridged dimer in the solid state. Cryoscopic measurements for 2 indicate a monomer–dimer equilibrium (η= 1.6) in solution which has been confirmed by variable-temperature 119Sn NMR studies. In the solid state the ligating mode of the Zr2(OPri)9– unit in 2 is different from isostructural Sn2(OPri)9– and it binds to tin via only three OPri groups, the fourth M–OPri interaction being hindered by the stereochemically active lone pair of electrons present at SnII. The central SnI2O6 core in 2 can be viewed as two SnI2O3 octahedra fused along a common axial–equatorial edge where one of the axial co-ordination sites in each is occupied by the non-bonding electron pair of SnII.