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Theoretical Study on the Transition-Metal Oxoboryl Complex: M–BO Bonding Nature, Mechanism of the Formation Reaction, and Prediction of a New Oxoboryl Complex
journal contribution
posted on 2012-04-16, 00:00 authored by Guixiang Zeng, Shigeyoshi SakakiThe Pt–BO bonding nature and the formation reaction
of the
experimentally reported platinum(II) oxoboryl complex, simplified
to PtBr(BO)(PMe3)2, were theoretically investigated
with the density functional theory method. The BO– ligand was quantitatively demonstrated to have extremely strong
σ-donation but very weak dπ-electron-accepting
abilities. Therefore, it exhibits a strong trans influence. The formation
reaction occurs through a four-center transition state, in which the
Bδ+–Brδ− polarization
and the Br → Si and O pπ → B pπ charge-transfer interactions play key roles. The Gibbs
activation energy (ΔG°⧧) and Gibbs reaction energy (ΔG°) 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 ΔG°⧧ and ΔG°. In addition, the metal effect
is examined with the nickel and palladium analogues and MBrCl[BBr(OSiMe3)](CO)(PR3)2 (M = Ir and Rh). By a comparison
of the ΔG°⧧ and ΔG° values, the M–BO (M = Ni, Pd, Ir, and Rh)
bonding nature, and the interaction energy between [MBrCl(CO)(PR3)2]+ and BO– with
those of the platinum system, MBrCl(BO)(CO)(PR3)2 (M = Ir and Rh) is predicted to be a good candidate for a stable
oxoboryl complex.
