Synthesis and Isomerisation Reactions of Tetranuclear and Octanuclear (Carbamato)zinc Complexes

A new series of (diisopropylcarbamato)(oxido)zinc complexes were obtained by innovative synthetic approaches. The (carbamato)zinc clusters [Zn4(μ4-O)(O2CNiPr2)6] (1) and [Zn8(μ4-O)2(O2CNiPr2)12] (2) were synthesised by an identical reaction procedure involving protolysis of ZnEt2 with iPr2NH/CO2 and followed by stoichiometric hydrolysis. Recrystallisation of the reaction product from nitrile solvents yielded the tetrazinc complex 1. Conversely, recrystallisation from alkane solvents yielded crystals of the octazinc complex 2. The two structural isomers were readily interconverted simply by recrystallisation from the appropriate solvent. Both complexes were structurally characterised by X-ray crystallography. The tetrazinc complex 1 has the quintessential basic zinc acetate type structure. Its dimer, the octazinc complex 2 is a new derivative of the [M8(μ4-O)2(O2CNiPr2)12] class, examples of which are known for all other first-row transition metals. The solution chemistry was investigated using variable-temperature NMR spectroscopy and ESI-MS. The new synthetic approach offers a route to other similar complexes. Thus, using Et2NH in place of iPr2NH yielded the known complex [Zn4(μ4-O)(O2CNEt2)6] (3).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)