Heteronuclear complexes derived from the molecular ion [Hg(SCN)4]2−: Variance in bridging matrices, nuclearities and architectures with the change in complementary units

Five neutral heteronuclear compounds of the type [M(tren)(μ-NCS)zHg(SCN)4−z]n [M = Cu/Zn/Cd, z = 1, n = 1, 1/2/3; M = Ni, z = 2, n = 2, 4; M = Pb, z = 3, n = ∞, 5; tren = tris(2-aminoethyl)amine] have been synthesized and characterized. X-ray structural analyses reveal that the tetrahedral [Hg(SCN)4]2− unit forms a single Hg–SCN–M end-to-end bridge with Cu(II), Zn(II) and Cd(II) of the complementary unit [M(tren)(S)z]2+, affording dinuclear 1–3, respectively, with a trigonal bipyramidal geometry around the heterometal ions. In tetranuclear 4, four single Hg–SCN–Ni bridges bind two different octahedrally coordinated Ni(II) centers forming a cyclic loop. A heteropolynuclear chain with heptacoordinated Pb(II) in 5 results through alternate single and double NCS bridges. Multiple N–H⋯N, N–H⋯S, C–H⋯N, C–H⋯S hydrogen bonds in 1–5 and S⋯S interactions in 1–4 promote increased dimensionalities. EPR and variable-temperature (2–300 K) magnetic data of 1 and 4 have been interpreted in terms of their structures.

Graphical abstractThe syntheses, molecular and crystalline architectures, and properties of five neutral heteronuclear compounds of the type [M(tren)(μ-NCS)zHg(SCN)4−z]n [M = Cu/Zn/Cd, z = 1, n = 1, 1/2/3; M = Ni, z = 2, n = 2, 4; M = Pb, z = 3, n = ∞, 5; tren = tris(2-aminoethyl)amine] are described. The interesting change in bridging matrices, nuclearities and architectures with the change in complementary units is highlighted.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Five neutral heteronuclear compounds are isolated using [Hg(SCN)4]2− and [M(tren)(solvent)z]2+. ► The X-ray structures show interesting changes in nuclearities and bridging matrices as well. ► A variation in the crystalline architectures is also observed through a change in the complementary units. ► Compound 4 shows weak antiferromagnetic interactions mediated through –NCS–Hg–SCN– bridges.