Structural Studies of Complexes Containing the Peroxodisulfate Anion. II. The Crystal and Molecular Structure of Cd(S2O8) (bpy)2.H2O and Hg2(S2O8)(terpy)2(acet)2 (bpy: 2,2′-bipyridine, terpy: 2,2′,2′′-terpyridine, acet: acetate)

Abstract

The crystal structures of two transition-metal complexes with different dinitrogenated bases, and the unusual peroxodisulfate anion are presented, Cd(S₂O₈)(bpy)₂·H₂O (1) and Hg₂(S₂O₈)(terpy)₂(acet)₂ (2) (where bpy represents 2,2′-bipyridine, terpy represents 2,2′,2′′-terpyridine, and acet represents acetate).

In both structures, though in different ways, the peroxodisulfate group acts as a bridge, giving rise to polymeric linear chains. To our knowledge these are the first structures reported wherein the anion displays such behaviour. The cadmium compound crystallizes with one water molecule of hydration, which intervenes in medium-strength H-bonds, stabilizing the structure. The mercury complex is built up of similar, though independent, chains displaying double Hg–O–Hg bridges spanning Hg···Hg distances of 4.214(1) and 3.911(1) Å. The inter-chain link is achieved through weak C–H···O contacts.

Compound (1) is triclinic P1^–; a 7.213(3), b 9.841(6), c16.371(5) Å; α 82.94(4), β 82.31(3), γ 86.32(4)˚; V 1141.6(9) ų; Z 2; conventional R (on F) being 0.0315 for 4019 N_o observed reflections (I> 2σ(I)). Compound (2) is also triclinic P1^–; a 10.653(2), b 12.195(3), c 14.641(3) Å; α 88.295(19), β 83.553(18), γ 73.921(19)˚; V 1816.0(7) ų; Z 2; R0.0498; N_o 6179.