A new transformation of methylene-bis (phosphonic dichloride) into tetrathiobisphosphonate derivatives is reported. The reaction of methylene-bis (phosphonic dichloride) with 1, 2- ethanedithiol in bromoform in the presence of AlCl3 formed methylene-bis (1, 3, 2- dithiaphospholane-2-sulfide), which gave rise to O, O′-diester- methylenediphosphonotetrathioate analogues 1a–k upon reaction with phenols and alkyl ...