Theoretical investigation of the nature of π(BB)⋯M interactions in coinage metal π-diborene complexes

Abstract

Transition metal π-diborene species exhibit fascinating photophysical properties, and their unique properties reflect their particular electronic structure. In this work, the nature of π(BB)⋯M interactions in coinage metal π-diborene complexes, B₂IDip₂⋯nMCl (n = 1, 2, 3; M = Cu, Au, Ag), was characterized within the framework of energy decomposition analysis, natural bond orbital analysis, atoms in molecule theory, and the electron localization function method. The calculated results show that the M atom of MCl interacts with two boron atoms of B₂IDip₂ to form an η²-coordinated structure. The π(BB)⋯M interactions belong to the Dewar–Chatt–Duncanson model, the charge transfers from IDip to π(BB) bonds first and then from π(BB) bonds to the MCl. In π(BB)⋯M interactions, electrostatic interactions are dominant, and orbital interactions are important. The strengths of π(BB)⋯M interactions increase in the sequence of M = Ag, Cu, and Au for the same n. The formation of π(BB)⋯M interactions weakens the BB and B-C bonds in B₂IDip₂. In particular, the BB bonds become increasingly weaker with an increasing number of MCl, followed by M = Ag, Cu, and Au.