Influence of 18-Crown-6 Ether Coordination on the Catalytic Activity of Potassium and Calcium Diarylphosphinites in Hydrophosphorylation Reactions.

The addition of 18-crown-6 ether (1,4,7,10,13,16-hexaoxacyclooctadecane) to tetranuclear [(thf)K(OPAryl)] and [(thf)Ca(OPAryl)] yields the corresponding mononuclear complexes [(18C6)K(OPAryl)] [Aryl = Ph (1a), Mes (1b)] and [(18C6)Ca(OPAryl)] [Aryl = Ph (2a), Mes (2b)]. The metathesis reaction of [(thf)K(OPAryl)] with CaI yields the calciate [KCa(thf){OPMes}]. The addition of dimesitylphosphane oxide and crystallization from a hexane solution gives [KCa{OPMes}{MesP(O)H}] (3). The complexes [(thf)K(OPMes)], [(thf)Ca(OPMes)], 1b, 2b, and the calciate 3 are tested as catalysts in the hydrophosphorylation of isopropylisocyanate with dimesitylphosphane oxide, quantitatively yielding N-isopropyl(dimesitylphosphoryl)formamide. The potassium complexes are more efficient catalysts than the calcium congeners, and coordination of 18-crown-6 decelerates the catalytic conversion.