Platinum stilbazoles: ring-walking coupled with aryl-halide bond activation.

The reaction between tetrakis(triethylphosphine)platinum(0) and 4-[trans-2-(4-bromophenyl)vinyl]pyridine (1) is examined. Initially, the metal center coordinates to the bridging double bond of 1. Complexes 2 and 3 were fully characterized, and their X-ray crystallography structures are presented. Upon heating, either in solution or in the solid state, complex 2 undergoes C-Br oxidative addition to give complex 3. Kinetic studies revealed that this conversion is unimolecular and does not involve dissociation of the metal center from the double bond. Density functional studies show that a plausible mechanism involves the metal center "walking" around the pi-system from the bridging C=C double bond to the C-Br bond.