Mercury(II) acetate complexes of the type (R3P)nHg(OAc)2, where n = 1 and 2, and R3P = (p-tolyl)3P, (p-F-C6H4)3P, Ph2MeP, Ph2EtP, and PhEt2P have been prepared in good yields. Only the 1:1 adduct is formed with (o-tolyl)3P. Conductance measurements in nitromethane show that these complexes are non-electrolytes. The 1:1 adducts are monomeric in dichloroethane but the 1:2 adducts are extensively dissociated. Tentative assignments for ν(COO), ν(Hg—O), ν(Hg—P) are made from the infrared and Raman spectral data. The correlation of the coordination chemical shifts, Δδ(31P), with the coupling constants 1J(199Hg–31P) of the complexes is discussed with respect to the bulkiness and the basicity of the phosphine ligands.