Theoretical Study on the Transition-Metal Oxoboryl Complex: M–BO Bonding Nature, Mechanism of the Formation Reaction, and Prediction of a New Oxoboryl Complex ZengGuixiang SakakiShigeyoshi 2012 The Pt–BO bonding nature and the formation reaction of the experimentally reported platinum­(II) oxoboryl complex, simplified to PtBr­(BO)­(PMe<sub>3</sub>)<sub>2</sub>, were theoretically investigated with the density functional theory method. The BO<sup>–</sup> ligand was quantitatively demonstrated to have extremely strong σ-donation but very weak d<sub>π</sub>-electron-accepting abilities. Therefore, it exhibits a strong trans influence. The formation reaction occurs through a four-center transition state, in which the B<sup>δ+</sup>–Br<sup>δ−</sup> polarization and the Br → Si and O p<sub>π</sub> → B p<sub>π</sub> charge-transfer interactions play key roles. The Gibbs activation energy (Δ<i>G</i>°<sup>⧧</sup>) and Gibbs reaction energy (Δ<i>G</i>°) of the formation reaction are 32.2 and −6.1 kcal/mol, respectively. The electron-donating bulky phosphine ligand is found to be favorable for lowering both Δ<i>G</i>°<sup>⧧</sup> and Δ<i>G</i>°. In addition, the metal effect is examined with the nickel and palladium analogues and MBrCl­[BBr­(OSiMe<sub>3</sub>)]­(CO)­(PR<sub>3</sub>)<sub>2</sub> (M = Ir and Rh). By a comparison of the Δ<i>G</i>°<sup>⧧</sup> and Δ<i>G</i>° values, the M–BO (M = Ni, Pd, Ir, and Rh) bonding nature, and the interaction energy between [MBrCl­(CO)­(PR<sub>3</sub>)<sub>2</sub>]<sup>+</sup> and BO<sup>–</sup> with those of the platinum system, MBrCl­(BO)­(CO)­(PR<sub>3</sub>)<sub>2</sub> (M = Ir and Rh) is predicted to be a good candidate for a stable oxoboryl complex.