Cleavage of the Au-P Bond in Au-Substituted Phosphines

Three protocols that involve the cleavage of the Au-P bond in Au-substituted phosphines (AuPhos) have been demonstrated, namely i) direct demetallation with a strong anionic base; ii) protonation followed by demetallation with a neutral base; iii) oxidation-triggered metal migration. Specifically, direct demetallation of (CAAC)AuPPh2 (1 a) (CAAC=cyclic (alkyl)(amino)carbene) with KP(TMS)(2) or LiC(N-2)TMS yields (CAAC)AuPTMS2 (2) or (CAAC)AuC(N-2)TMS (3), respectively. Treatment of (NHC)AuPPh2 (1 b) (NHC=N-heterocyclic carbene) with HOTf followed by the corresponding neutral phosphine gives scarce examples of aurophosphonium salts [(NHC)AuPHAd(2)][OTf] (5) and [((NHC)Au)(2)PPh2][OTf] (6). Oxidation of 1 a or 1 b with Se affords LAuSeP(Se)Ph-2 (L=CAAC, 7 a; NHC, 7 b).