Arsine stabilized triangulo-[Hg3]4+ clusters

Subvalent mercury clusters [Hg3(LL)3]4+ with LL=dpam (dpam=Ph2AsCH2AsPh2) or Ph2AsCH2PPh2 and dpam–dppm (dppm=Ph2PCH2PPh2) or dpam–Ph2AsCH2PPh2 mixed ligand complexes were obtained by reaction of [Hg2]2+ with the ligands or by reduction of a mixture of [Hg(Me2SO)6](O3SCF3)2 and the ligands with elemental mercury. Whereas the equilibrium 2Hg2++Hg⇌[Hg3]4+ is far to the right in the presence of the ligands dpam or dppm, only ca. 20% conversion is observed for Ph2AsCH2PPh2. The clusters are characterized by FAB MS and multinuclear NMR spectroscopy. The 199Hg–199Hg coupling constants of [Hg3(μ-dpam)2(μ-dppm)](O3SCF3)4 have values of 17 800 and 23 600 Hz. The fragmentation of [Hg3(μ-dpam)3](O3SCH3)4 gives [Hg2(μ-dpam)2](O3SCH3)4 which is characterized by single-crystal X-ray diffraction.