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)3PAuArF 3a [Ar = 2,4-(t-Bu)2C6H3]. A different outcome was observed
with the analogous precursor (MeO)3PAuArF 3b. 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.