Platinum Assisted Tandem P-C Bond Cleavage and P-N Bond Formation in Amide Functionalized Bisphosphine -PhPCHC(O)N(H)CHPPh-: Synthesis, Mechanistic, and Catalytic Studies.

The reactions of amide functionalized bisphosphine -PhPCHC(O)N(H)CHPPh- () with platinum salts are described. Treatment of with [Pt(COD)Cl] yielded a chelate complex, [PtCl{-PhPCHC(O)N(H)CHPPh-}] (), which on subsequent treatment with LiHMDS formed a novel 1,2-azaphospholene-phosphine complex [Pt(CH)Cl{-CH{C(O)N(-PPh(CH))P(Ph)}}] () involving a tandem P-C bond cleavage and P-N bond formation. The same complex on passing dry HCl gas afforded the dichloro complex [PtCl{-CH{C(O)N(-PPh(CH))P(Ph)}}] (). Complex upon refluxing in toluene or treatment of with [Pt(COD)Cl] in the presence of a base at room temperature resulted in the pincer complex [PtCl{-PhPCHC(O)N(CHPPh-)}] (). Reaction of with [Pt(COD)ClMe] at room temperature also afforded the pincer complex [PtMe{-PhPCHC(O)N(CHPPh-)}] (). Mechanistic studies on 1,2-azaphospholene formation showed the reductive elimination of LiCl to form a phosphonium salt that readily adds one of the P-C bonds oxidatively to the generated Pt species to form a chelate complex . The analogous palladium complex [PdCl{-CH{C(O)N(-PPh(CH))P(Ph)}}] () showed excellent catalytic activity toward -alkylation of amines with alcohols with a very low catalyst loading (0.05 mol %), and the methodology is very efficient toward the gram-scale synthesis of many -alkylated amines.