Diverse reactivity of a tricoordinate organoboron LPhB: (L = oxazol-2-ylidene) towards alkali metal, group 9 metal, and coinage metal precursors.

The reactivity of a tricoordinate organoboron LPhB: (L = oxazol-2-ylidene) towards metal precursors and its coordination chemistry were comprehensively studied. While the boron center in is reluctant to coordinate to the alkali metals in their trifluoromethanesulfonate salts (MOTf) (M = Li, Na, K), the unprecedented compound containing two LPhB: units linked by a cyclic Li(OTf)Li spacer was obtained from the reaction of with LiOTf. Treatment of with group 9 metal complexes [MCl(COD)] (M = Rh, Ir) afforded the first zwitterionic rhodium(i)-boronium complex and the iridium(iii)-borane complex , respectively. The reaction pathway may involve C-H activation followed by proton migration from the metals to the boron center, demonstrating the first example of the deprotonation of metal hydrides by a basic boron. In the reactions with coinage metals, could act as a two-electron reducing agent towards the metal chlorides MCl (M = Cu, Ag, Au). Meanwhile, the reaction of with gold chloride supported by a N-heterocyclic carbene (NHC) produced a heteroleptic cationic gold complex [(LPhB)Au(NHC)]Cl () featuring both carbene and LPhB: ligands on the gold atom. In contrast, an isolable gold chloride complex (LPhB)AuCl () was obtained by direct complexation between and triphenylphosphine-gold chloride ligand exchange. X-ray diffraction analysis and computational studies revealed the nature of the B:→Au bonding interaction in complexes and . Natural Population Analysis (NPA) and Natural Bond Orbital (NBO) analysis support the strong σ-donating property of the LPhB: ligand. Moreover, preliminary studies showed that complex can serve as an efficient precatalyst for the addition of X-H (X = N, O, C) to alkynes under ambient conditions, demonstrating the first application of a metal complex featuring a neutral boron-based ligand in catalysis.