The metalation of esters of tetraalkyl methylenediphosphonates with sodium, potassium, sodium hydride and n-butyllithium to form the corresponding salts, M + [ H(PO 3 R 2 ) 2 ], is described. These compounds were characterized by 31 P and 1 H NMR; their synthetic usefulness was demonstrated by the preparation of a variety of alkylates, R′CH(PO 3 R 2 ) 2 , and by the preparation of mono and dihalo derivatives, XCH(PO 3 R 2 ) 2 and X 2 C(PO 3 R 2 ) 2 , by ...