Reactivity of Elemental Tin and Zinc toward Organophosphonic Acid Dialkyl Esters: A New One-Pot Recipe for the Synthesis of Coordination Assemblies Derived from O-Alkylorganophosphonate Ligands.

Abstract

A new recipe for the synthesis of diorganotin bis(O-alkylorganophosphonate)s, R12Sn{O(P)(O)(OR1)R}2 [R = R1 = methyl (1); R1 = ethyl and R = methyl (2), allyl (3), 2-thienyl (4), benzyl (5)], has been developed from the direct reaction of elemental tin (powder) with organophosphonic acid dialkyl esters, RP(O)(OR1)2, in the presence of a catalytic amount of potassium iodide under ambient conditions (130 °C, 18-20 h). The key steps in the proposed catalytic cycle involve the monodealkylation of phosphonate diester and in situ generation of a R1SnI or R12SnI2 intermediate via the oxidative addition of alkyl iodide on tin. Evidence in support of the formation of organotin species comes from the isolation of Me2Sn{O(P)(O)(OiPr)Me}2 (6) from the direct reaction of tin metal with MeP(O)(OiPr)2 in the presence of methyl iodide. The method has also been extended to isolate Zn{OP(O)(OMe)Me}2 (7) using metallic zinc as the precursor. All of the compounds have been characterized by IR and NMR studies as well as X-ray crystallography for 2, 4, 6, and 7.