Insight into the Mechanism of R-R Reductive Elimination from the Six-Coordinate d6 Complexes L2Pt(R)4 (R = vinyl, Me)

We have used density functional theory to investigate the reductive elimination from platinum(IV) structures of the form L2PtR4 where L = PMe3, PH3, PF3, CO, NH3 and R = vinyl, Me. We conclude that reductive elimination occurs via the L-predissociation pathway for R = Me, irrespective of ligand L. But when R = vinyl, direct elimination is the preferred pathway if the L ligand is PMe3; otherwise both pathways are competitive for R = vinyl. We also note that if L is more pi-electron accepting and less a-electron donating, the reductive elimination from the six-coordinate complexes L2PtR4 will be more rapid. Reductive elimination from the five-coordinate complexes LPtR4 proceeds more easily if the ligand trans to the two R groups being coupled is more a-electron donating and the ligands cis to the two R groups are more pi-electron accepting.