Iridium-Promoted B-B Bond Activation: Preparation and X-ray Diffraction Analysis of a mer-Tris(boryl) Complex.

The tris(boryl) complex Ir(Bcat){κ-P,O,P-[xant(PPr)]} [Bcat = catecholboryl; xant(PPr) = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene] has been prepared and characterized by X-ray diffraction analysis. The boryl ligands are disposed in a mer arrangement. The Ir-B bonds situated mutually trans are ∼0.1 Å longer than that disposed cis to the other two. An energy decomposition analysis method coupled to natural orbitals for chemical valence has revealed that the level of π-back-donation from the metal to the p atomic orbital of the boron atom decreases ∼43% in the longer bonds with respect to the shorter one, while the level of σ-bonding interaction diminishes by only ∼8%.