New approach to sulfonated diphosphine complexes: synthesis and amphoteric behaviour of zwitterionic [Mn+(CO4{(PPh2)2C(H)SO3-}].

Oxidation of the thioketone residue in the complex [Mn(CO)4{(PPh2)2C=S}]+ (2) with hydrogen peroxide affords the sulfonate derivative [Mn(CO)4{(PPh2)2C(H)SO3}] (3), which shows amphoteric behaviour in reversible acid-base processes, and is easily chlorinated to give [Mn(CO)4{(PPh2)2C(Cl)SO3}] (8).