Facile access to enantiomerically pure bis(sulfoxide) chelates of late transition metals

Herein contains a report detailing the synthesis and characterization of six, chiral, late-transition metal complexes all chelated using R-S, R-S-bis(p-tolylsulfinyl)ethane, R-S, R-S-BTSE. All complexes revealed S-ligation to the metal with an expected contraction of the sulfinyl-oxygen bond length when compared to free sulfoxide. The presented data serve to illustrate three attractive, yet unexplored, aspects of the bis(sulfoxide) bidentate ligand: (i) bidentate sulfoxide ligands, when chelated to a metal, give rise to complexes that are pseudo-C-2 symmetric in terms of both sterics and electronics, (ii) the sulfoxides, unlike typical N-, P-, and O-based ligands, present the coordination sphere with a significant amount of steric and electronic mismatch, and (iii) the data support the fact that sulfoxides are moderate sigma-donors and good-to-excellent pi-acceptors - an aspect that should afford such metal chelates with a wide degree of reactivity. Finally, X-ray crystallographic experiments, coupled with an extensive CCDC search, provide an opportunity to establish the following ligand-ranking scheme for bidentate ligands spanned by an ethylene bridge, R2N- < RS(O)- < RS- < R2P-, based on the trans influence of chloride salts of Pt(H). (C) 2003 Elsevier Science B.V. All rights reserved.