SYNTHESIS AND X-RAY CRYSTAL-STRUCTURE OF THE FIRST MONONUCLEAR NICKEL(II) ALKANE THIOLATE COMPLEX WITH A MIXED (S,N,N,O) LIGAND-FIELD

The six-step synthesis of a chiral, pentadentate dihydrosalen Ligand, carrying a mercaptomethyl group as additional binding site, is describ ed. When this ligand was treated with nickel(II) salts, a planar tetra coordinated nickel chelate was obtained, and not the expected pentacoo rdinated species. This complex was fully characterized, including X-ra y crystallography. The crystal structure revealed that the nickel ion is coordinated by the thiolate anion, both the amine and the imine nit rogen atoms of the Ligand, and by one phenolate anion. The second phen olic oxygen atom of the Ligand does not participate in the coordinatio n of the nickel ion. This chelate is the first mononuclear nickel(II) thiolate complex having a mixed (S,N,N,O) Ligand field. Cyclic voltamm etry did not indicate a reduction up to -2.1 V (vs. Fc/Fc(+)). In the anodic range, no reversible but two irreversible oxidation processes w ere observed.