Thermodynamics of metal-ligand bond formation. XX. Reaction of tertiary phosphines with mercury(II) halides

Abstract

Tertiary phosphines form highly stable 1 : 1 and 2 : 1 adducts with mercury(11) halides in benzene solution. In the series of phosphines (alkyl),PPh_3-n enthalpies of formation are determined by inductive effects and give a linear relationship with Taft constants, ∑σ*. The cyclic phosphine 1,2,5-triphenylphosphole is a much weaker base towards the mercury(11) halides. While ethane-1,2- diylbis(dipheny1phosphine) behaves only as a chelate, methylenebis(dipheny1phosphine) can behave both as a chelate and as a bridging ligand and propane-1,3-diylbis(dipheny1phosphine) only as a bridging ligand. The unsaturated diphosphines (2)- and (E)-ethene-l,2-diylbis(dipheny1phosphine) both form 1 : 1 adducts with mercury(11) halides in benzene solution in which the phosphines are unidentate. Enthalpy data are reported for the formation of all these adducts.