Controlling the Reactivity of the Boronyl Group in Platinum Complexes toward Cyclodimerization: A Theoretical Survey.

A theoretical study of the cyclodimerization of (Cy3P)2Pt(BO)Br (1Br) and [(Cy3P)2Pt(BO)](+) (1) (Cy = cyclohexyl) suggests that the reactivity of the BO ligand is primarily controlled by M←BO σ donation. Therefore, increasing the electron density at the metal center through strong σ-donor and weak π-acceptor ancillary ligands and a low formal metal oxidation state are suggested to reduce the polarity of the boronyl ligand and thus lower its reactivity toward cyclodimerization. The stable 1Br has lower Pt←BO σ donation and thus a less electrophilic boron atom, leading to a less polarized BO ligand. However, 1 is unstable in dichloromethane, since the dicationic dimer and transition state are highly stabilized by strong electrostatic interactions.