Dechlorination of diphenyl chlorophosphate with tin and sodium 3,6-di-tert-butyl-ortho-semiquinones

Dechlorination reactions of diphenyl chlorophosphate (PhO)2P(O)Cl with 3,6-di-tert-butyl-ortho-semiquinone complexes of triphenyl tin, SQSn(Ph)3 and sodium, SQNa have been investigated by electron spin resonance (ESR) both in solutions at 300 K and in solid phase at 77 K using mechanochemical activation. Paramagnetic 3,6-di-tert-butyl-ortho-semiquinone ligand (SQ) was used as spin probe to monitor changes in the Sn coordination sphere during the dechlorination reaction of (PhO)2P(O)Cl and consecutive formation of tin chloride derivatives SQSnCl(Ph)2, SQSnCl2Ph, and SQSnCl3. Their structure was revealed based on the analysis of hyperfine interaction constants due to 1H nuclei in the 4,5-positions of the aromatic ring of the SQ ligand, hyperfine interaction constants due to 35Cl and 37Cl nuclei of chlorine atoms in the Sn coordination sphere, and hyperfine interaction constants due to 117Sn and 119Sn nuclei of the central metal ion. Interaction of SQSnCl3 with (PhO)2P(O)Cl leads to the formation of a meta-stable radical–anion complex [SQSnCl4]radical dot− P+(O)(OPh)2, which transforms to SQSnCl3⋯P(O)R3, a stable adduct of SQSnCl3 with dechlorinated phosphate of a general formula P(O)R3. Analysis of solution dechlorination reaction products suggests the formation of diphenyl-phosphoryl radical (PhO)2Pradical dot(O), which was not observed in solutions. Dechlorination of (PhO)2P(O)Cl with sodium 3,6-di-tert-butyl-ortho-semiquinone SQNa can proceed in solid phase in liquid nitrogen at 77 K via mechanochemical activation using a ball mill. ESR analysis of the cryo-mechanochemical reaction showed the formation of the adduct of (PhO)2Pradical dot(O) radical with 3,6-di-tert-butyl-ortho-quinone.