ic035205y_si_001.cif (53.52 kB)

Synthesis and Oxygenation of a Nickel(II) and Zinc(II) Dithiolate:  An Experimental and Theoretical Comparison

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posted on 03.05.2004, 00:00 by Craig A. Grapperhaus, Christopher S. Mullins, Pawel M. Kozlowski, Mark S. Mashuta
The diamino-dithiolato N2S2 ligand N,N‘-bis-2-methyl-mercaptopropyl-N,N‘-dimethylethylenediamine, H2(bmmp-dmed), and its nickel (1) and zinc (2) complexes have been prepared and their reactivities with hydrogen peroxide investigated. Complex 1 yields a mixture of sulfenato (RSO-), 4, sulfinato (RSO2-), 3, and sulfonato (RSO3-), 5, products upon addition of H2O2. Products are separable by column chromatography. Stoichiometric addition of H2O2 to 2 yields an inseparable mixture. Excess peroxide addition results in oxygenation of the ligand to the disulfonate, 6, and decomplexation of zinc. Complexes 1, 2, and 3 and compound 6 have been investigated by X-ray crystallography, and their structures are reported. Density functional theory (DFT) calculations of 1 and 2 reveal significant sulfur p character in the HOMO of each complex. However, 1 also shows significant metal d character that is π-antibonding with respect to the sulfur p orbitals. Complex 2 shows little metal character in the HOMO. Implications of the HOMO with respect to S-centered reactivity and metal ligand distances in S-oxygenated products are provided.