Mercury(I) chemistry. Part II. Reactions of the mercurous ion with some ligands having the heavier Group VA or VIA elements as donor atoms

Abstract

The reactions of Hg2(AsF6)2 with P(CF3)3, PF3, PCl3, P(CF3)Ph2, PClPh2, PPh3, P(OMe)3, AsPh3, SbPh3, SPPh3, SP(p-C6H4F)3, and SePPh3 in liquid sulfur dioxide have been studied. The last five ligands form insoluble 1:1 complexes, Hg2(AsF6)2•L, if L:Hg22+ ≤ 1, but disproportionation of the mercurous ion occurs if L:Hg22+ > 1; the 1:1 mercurous complexes have been characterized by analysis and vibrational spectroscopy. There is no evidence for complexation of P(CF3)3. PPh3 and P(OMe)3 cause disproportionation of the mercurous ion under all conditions; Hg(PPh3)22+ and Hg(P(OMe)3)22+ have been characterized by 13C and 1H nmr respectively. When P(CF3)Ph2:Hg22+ ≤ 1 soluble Hg2(P(CF3)Ph2)2+ is formed; the 19F and 13C nmr spectra of this complex are reported, as are those of Hg(P(CF3)Ph2)22+. In the system PF3–Hg2(AsF6)2–SO2 no disproportionation occurs; 19F nmr provides evidence that Hg2PF32+ and, probably, Hg2(PF3)22+ are formed. 1J(P–F) in mercurous and silver(I) complexes of PF3 is of unusually large magnitude. The 13C nmr spectra of Hg(PPh3)22+, Hg2(P(CF3)PPh2)2+, and Hg(P(CF3)Ph2)22+, are consistent with the occurrence of little metal-to-phosphorus back-bonding in these phosphine complexes. The relationship between the net electron donating ability of a phosphine and the nature of its interaction with the mercurous ion is discussed.