NEW PERTHIOPHOSPHONIC ACID ANHYDRIDES AND THE DIRECT INDICATION OF THE DIMER-MONOMER EQUILIBRIUM - NMR AND X-RAY STUDIES

New perthiophosphonic acid anhydrides (R-PS2)n with R = 2,4,6-tri-iso-propylphenyl and 2,4-di-tert-butyl-6-methylphenyl have been prepared. For the latter case, the isolation of the monomer (n = 1), the 2,4-di-tert-butyl-6-methylphenyl-dithioxophosphorane, and both dimers (n = 2), cis- and trans-2,4-bis(2,4-di-tert-butyl-6-methylphenyl)-2,4-dithioxo-1, 3,2,4-dithiadiphosphetane, of one perthiophosphonic acid anhydride has been performed for the first time. The crystal structure of 2,4-di-tert-butyl-6-methylphenyl-dithioxophosphorane and of cis-2,4-bis(2,4,6-tri-iso-propylphenyl)-2,4-dithioxo-1,3,2,4-dithiadiphosphetane has been determined. The new cis and trans dithiadiphosphetanes and dithioxophosphoranes as well as the known compounds (2,4,6-trimethylphenyl-PS2)2 and 2,4,6-tri-tert-butylphenyl-PS2 are characterized by solution and high resolution solid-state P-31 and C-13 NMR spectroscopy. The existence of a dimer-monomer equilibrium is directly proved by 2D exchange P-31 NMR spectroscopy. It is shown that the reaction of the monomer with methanol is faster than the reaction of the dimer with methanol.