Controlling the Properties of a 2,2′-bipy–Platinum Dichloride Complex via Oxidation of a Peripheral Stibine Moiety

Our interest in the chemistry of antimony derivatives has led us to investigate the synthesis and properties of 4-(diphenylstibino)-2,2′-bipyridine (L^SbPh2). This new ligand, which could be obtained by reaction of 4-lithio-2,2′-bipyridine with Ph₂SbCl, was treated with Pt­(CH₃CN)₂Cl₂ to afford the platinum complex L^SbPh2PtCl₂ (1). Interestingly, the latter reacts with PhICl₂ to afford L^SbCl2Ph2PtCl₂ (2), a complex in which the peripheral stibine moiety has been converted into a dichlorostiborane. Complexes 1 and 2 have both been fully characterized. Computational, UV–vis, and cyclic voltammetry studies show that oxidation of the antimony atom leads to a lowering of the bipy-centered LUMO, indicating that 2 is more electron deficient than 1. A congruent picture emerges from reactivity studies, which show that 2 is a more active catalyst for the hydroarylation of ethyl propiolate by mesitylene.