Synthesis, Structure, and Preparative Transamination of Tetrazinc Carbamato Complexes Having the Basic Zinc Carboxylate Structure

The series of tetranuclear zinc(II) carbamato complexes (Zn4O)(O2CR)6, (1, R = diethylamino; 2, R = piperidino; 3, R = pyrrolidino) was prepared. Complexes 2 and 3 were crystallographically characterized and shown to have the same tetrahedral Zn4O6+ core. Complex 2 crystallizes in the cubic space group I43d, a = 24.0131(5) A, V = 13846.6(5) A3, R(1976 observed reflections) = 0.0194, and GOF = 1.013. Complex 3 crystallizes in the triclinic space group P1, a = 10.3178(6) A, b = 10.6962(6) A, c = 19.5130(11) A, α = 81.9070(10)°, β = 75.4880(10)°, γ = 81.6540(10)°, V = 2050.4(2) A3, R(6141 observed reflections) = 0.0334, and GOF = 0.979. NMR spectroscopy was used to show that the (Zn4O)L6 structure was maintained in nonpolar solvents. The complexes reacted with free amine in nonpolar solvents, which resulted in facile conversion of one member of the series to another. For example, reacting 1 with a stoichiometric amount of pyrrolidine in tetrahydrofuran followed by workup resulted in the quantitative format...