Triel Bonds between BH(3)/C(5)H(4)BX and M(MDA)(2) (X = H, CN, F, CH(3), NH(2); M = Ni, Pd, Pt, MDA = Enolated Malondialdehyde) and Group 10 Transition Metal Electron Donors.

A systematic theoretical study was conducted on the triel bonds (TrB) within the BH(3)∙∙∙M(MDA)(2) and C(5)H(4)BX∙∙∙M(MDA)(2) (M = Ni, Pd, Pt, X = H, CN, F, CH(3), NH(2), MDA = enolated malondialdehyde) complexes, with BH(3) and C(5)H(4)BX acting as the electron acceptors and the square-coordinated M(MDA)(2) acting as the electron donor. The interaction energies of these systems range between -4.71 and -33.18 kcal/mol. The larger the transition metal center M, the greater the enhancement of the TrB, with σ-hole TrBs found to be stronger than π-hole TrBs. In the σ-hole TrB complex, an electron-withdrawing substituent on the C opposite to the B atom enhances the TrB, while an electron-donating substituent has little effect on the strength of TrB in the Pd and Pt complexes but enhances the TrB in the Ni-containing complexes. The van der Waals interaction plays an important role in stabilizing these binary systems, and its contribution diminishes with increasing M size. The orbital effect within these systems is largely due to charge transfer from the d(z)(2) orbital of M into the empty p(z) orbital of B.