Structural comparison of alkylated derivatives of (bmmp-dmed)Ni and (bmmp-dmed)Zn

The sulfur-alkylation of the nickel (1) and zinc (2) complexes of the dithiolate N2S2 ligand N,N′-bis-2-methyl-mercaptopropyl-N,N′-dimethylethylenediamine, H2(bmmp-dmed), have been investigated. Reactions with iodomethane yield [(Me-bmmp-dmed)Ni]PF6 (3), [(Me2-bmmp-dmed)NiI2] (4), and [(Me2-bmmp-dmed)ZnI]2[ZnI4] (5). Addition of iodoacetamide yields [(AA2-bmmp-dmed)Ni]I2 (6) and [(AA2-bmmp-dmed)Zn]I2 (7). Each of the metal-thioether products (3–7) have been characterized spectroscopically and by X-ray crystallography. Structural data is compared with that of the previously reported thiolato precursors 1 and 2. Sulfur-alkylation of 1 results in small relative changes in the nickel–sulfur bond distance, whereas for 2, the zinc–sulfur bond distance increases significantly, but is not cleaved. The difference between nickel and zinc is attributed to the release of a π*-bonding interaction between the metal and sulfur upon alkylation that compensates for the decreased σ-donor ability of the thioether in the case of nickel, but not for zinc.