Host–guest interactions of the cluster [ triangulo-Hg 3(μ-dppm) 3] 4+ (dppm=bis(diphenylphosphino)methane) with halides and pseudohalides

Abstract

The complexes [ triangulo-Hg 3(μ-dppm) 3X n ] (4− n)+ (X=Cl, Br and I, n=1, 2) are formed in a small extent upon addition of halides to the cationic subvalent cluster [ triangulo-Hg 3(μ-dppm) 3] 4+, whereas SeCN − and CN − cause quantitative fragmentation. The cluster [ triangulo-Hg 3(μ-dppm) 3(SCN) 2] 2+ is produced either by the reaction of [ triangulo-Hg 3(μ-dppm) 3] 4+ with thiocyanate or via reduction of a mixture of Hg(SCN) 2, [Hg(Me 2SO) 6](O 3SCF 3) 2 and 3 mequiv. of dppm with elemental mercury. The X-ray structure of [Hg 3(μ-dppm) 3(SCN) 2](O 3SCF 3) 2 shows a Hg 3 triangle (Hg–Hg distances 286.60(14), 279.32(12) and 281.2(2) pm) spanned by three dppm ligands. The thiocyanate ions are positioned nearly parallel to the Hg 3 plane in the two cavities formed by the Hg 3 group at the bottom and the phenyl groups of the dppm ligands as the walls (Hg1–S1 277.5(6) and Hg3–S2 278.4(6) pm). Phosphorus-31 solution NMR indicates a rapid rotation of the SCN − ligands about the Hg 3 triangle within the cavity.