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
(LSbPh2). 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 LSbPh2PtCl2 (1). Interestingly,
the latter reacts with PhICl2 to afford LSbCl2Ph2PtCl2 (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.