Nitrogen- and oxygen-bridged bidentate phosphaalkene ligands

An overview is given on synthesis and structures of new bidentate phosphaalkene ligands [(RMe2Si)2CP]2E (E = O, NR, N−) and (RMe2Si)2CPN(R′)PR′′2. Exceptional properties of these ligands, extending beyond predictable properties of phosphaalkenes are: (i) the NSi bond cleavage of [(iPrMe2Si)2CP]2NSiMe3 with AuI and RhI chloro complexes under mild conditions leading to binuclear complexes of the 6π-delocalised imidobisphosphaalkene anion [(iPrMe2Si)2CP]2N−, and (ii) the chlorotropic formation of molecular 1:2 PdII and PtIImetallochloroylid complexes with novel ylid-type ligands [(RMe2Si)2CP(Cl)N(R)PR2]−, and the transformation of a P-platina-P-chloroylid complex into a C-platina phosphaalkene by intramolecular chlorosilane elimination. Properties of the heavier congeners [(RMe2Si)2CP]2E (E = S, Se, Te, PR, P−, As−) and (RMe2Si)2CPEPR′′2 (E = S, Se, Te) are also described.