Facile reactions of gold(i) complexes with tri(tert-butyl)azadiboriridine

Abstract

Direct structural evidence for group 11 metal-mediated B–B bond activation was obtained from reactions of tri(tert-butyl)azadiboriridine (1) with AuCl(L) complexes. The AuCl(SMe₂) reaction afforded [η²-B,B-B(tBu)N(tBu)B(tBu)]AuCl (2) by ligand displacement. More donating phosphines as co-ligands led to B–B bond cleavage accompanied by either halide or L migration to form boron–gold complexes 3 (L = PPh₃) and 4 (L = PMe₃). A similar product 5, which is isostructural to 4, was obtained by the addition of dimethylaminopyridine (DMAP) to 2–4. Complexes 2–5 constitute rare examples of metal complexes bearing two Lewis acidic centres. The effect of the boryl ligand was demonstrated in the formation of a gold(I) complex 6 bearing a 5-membered heterocycle from 3 and tert-butylisonitrile. Plausible reaction mechanisms that led to these complexes and their bonding situation were explored computationally at the DFT level.