Stereoelectronic effects on the chelating properties of [2-(methylsulfinyl)ethyl]diphenylarsine and its phosphorus analogue.

Abstract

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 Ph2ECH2CH2S(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) Å,b = 17.449(3) Å,c= 21.981(4) Å,α = 82.67(2)° β = 87.06(2)°,γ= 82.87(2)°, 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 AsS coordination in solution. A similar bonding mode was observed for the analogous phosphine complex. The ES chelation appears to be governed by the electronic properties of platinum. In contrast to the previously documented palladium(II) analogues, the EO chelation is not observed in the present series of platinum(II) compounds although there will be less severe ligand-ligand interactions if the ES(O) ligands form six-membered chelate rings in these square-planar systems. © 1994.