Gold-to-Boron Aryl Transfer from a T-Shaped Phosphine–Borane Gold(I) Complex

T-shaped gold(I) complexes with significant Au→B interactions were prepared from the phosphine–borane i-Pr2P(o-C6H4)BFXyl2 [Fxyl = 3,5-(F3C)2C6H3]. The (P,B)AuArF complex 4 [ArF = 4-(F3C)C6H4] was obtained by an indirect route involving ligand exchange from (ArO)3PAuArF3a [Ar = 2,4-(t-Bu)2C6H3]. A different outcome was observed with the analogous precursor (MeO)3PAuArF3b. Here, the phosphite remains bonded to gold, and the borane moiety abstracts the ArF group from gold to give the zwitterionic dicoordinate gold(I) complex 5. DFT calculations support a 2-step associative pathway for this gold-to-boron aryl transfer. It involves a square-planar gold(I) complex with enhanced Au→B interaction as key intermediate and proceeds via a 3-center transition state.