A set of new coordination compounds of cadmium(II)/mercury(II) halides/pseudohalides containing polyamines: Syntheses involving in situ metal–ligand reactions, crystal structures and molecular properties

Coordination compounds of the types [Hg(atta)][HgCl4] (1), [Cd5(apda)2Cl10]n (2), [Cd3(apda)2(N3)4]n(ClO4)2n (3) and [Cd2(bpda)(NCS)4]n (4) [atta = 4-(2-aminoethyl)-triethylenetetramine; apda = N-(2-aminoethyl)piperazine-1,4-diethylamine; bpda = N,N′-bis(2-aminoethyl)piperazine-1,4-diethylamine] are isolated using tetraethylenepentamine (tepa; for 1–3)/pentaethylenehexamine (peha; for 4) in presence of cadmium(II)/mercury(II) halides/pseudohalides. Structural studies reveal that polyamines tepa and peha undergo interesting in situ rearrangement to afford atta/apda and bpda ligands, respectively. Asymmetric unit in 1 comprises of discrete [Hg(atta)]2+ cation and [HgCl4]2− anion. Compound 2 consists of neutral pentanuclear core [Cd5Cl10] formed by three different types of chloride bridges propagating through binucleating bitridentate character of apda to afford a 1D ladder structure. 2D coordination polymer 3 with (4162)(4262) topology is formed through double μ1,1- and single μ1,3-azide bridges and binucleating behavior of apda. Alternating double μ1,3-thiocyanate and binucleating bis(tridentate) bridges in 4 result in a 1D zig-zag chain. Different kinds of non-covalent interactions promote dimensionalities in 1–4. Thermal behaviors of 1–4 are examined.

Syntheses involving in situ metal–ligand reactions, molecular and crystalline architectures, and molecular properties of one (1) homobimetallic mercury(II) and three (2–4) polynuclear cadmium(II) compounds are described. The interesting variation in bridging matrices, nuclearities of the central metal ions and influence of non-covalent interactions in the promotion of dimensionalities of the compounds are highlighted.Figure optionsDownload as PowerPoint slideHighlights
► One homobimetallic mercury(II) and three polynuclear cadmium(II) compounds are isolated.
► Three interesting in situ metal–ligand reactions are observed.
► X-ray study shows interesting variation in bridging matrices, nuclearities and architectures.
► Thermogravimetric analyses show different thermal stabilities and decomposition patterns.