Thermodynamics of metal-ligand bond formation. XXIV. Reaction of mercury(II) halides with tertiary arsines and phosphine and arsine sulphides

Abstract

Thermodynamic data have been obtained by calorimetric titration for the formation of 1 : 1 adducts of mercury(11) halides with tertiary arsines in benzene solution. In contrast to phosphines, only one molecule of arsine adds to HgX₂ in dilute solution. Enthalpies of adduct formation, in the range - ΔHº = 50-80 kJ mol^-1, are not much changed by replacement of phenyl by methyl, but adduct stabilities increase in the order Ph₃As < Ph₂AsMe < PhAsMe₂ < AsMe₃ HgI₂AsMe₃ is dimeric in solution. The diarsines Ph₂As(CH₂),AsPh₂ are unidentate, but Ph₂P- (CH₂),AsPh₂ is bidentate. Data are also reported for addition to HgX₂ of Ph₃PS,Ph₂PSCH₂PSPh₂ and corresponding arsine sulphides; the disulphides are bidentate. Factors affecting chelation in these compounds are discussed.