STEREOELECTRONIC EFFECTS ON THE CHELATING PROPERTIES OF [2-(METHYLSULFINYL)ETHYL]DIPHENYLARSINE AND ITS PHOSPHORUS ANALOG

A pair of internally diastereomeric platinum(II) complex cations containing the orthometalated (S)-(1-(dimethylamino)ethyl)naphthalene and the racemic form of the sulfinyl-substituted ligand Ph(2)ECH(2)CH(2)S(O)Me ((E-S(O), where E = As, P) has been prepared via two routes originating from (S)-(+)bis(m-chloro)bis[1-[1-(dimethylamino)ethyl] -2-naphthalenyl-C,N]diplatinum(II). The crystal structure of the arsenic analogue (crystal data: triclinic, P1, a = 7.950(2) Angstrom, b = 17.449(3) Angstrom, c = 21.981(4) Angstrom, alpha = 82.67(2)degrees beta = 87.06(2)degrees, gamma = 82.87(2)degrees, Z = 4 and R = 0.0409) shows the ligand being coordinated to platinum(II) in both diastereomers as a bidentate chelate exclusively via arsenic and sulfur donor atoms. Proton NMR studies also indicate the retention of this As-S coordination in solution, A similar bonding mode was observed for the analogous phosphine complex. The E-S chelation appears to be governed by the electronic properties of platinum. In contrast to the previously documented palladium(II) analogues, the E-O chelation is not observed in the present series of platinum(II) compounds although there will be less severe ligand-ligand interactions if the E-S(O) ligands fonn six-membered chelate rings in these square-planar systems.