A {Cu < inf > 4 < /inf > I < inf > 4 < /inf > } Cluster Supported on a Metal-Dithiolato Complex Anion Causes its Conformational Change Leading to a Doubly-Bridged Curved Coordination Polymer and its Reactivity with a Diamine Resulting in the Emergence of a [M(diamine)(dithiolate)] System

Abstract

When dithiolene-based coordination complexes [Bu4N]2[MII(tdas)2] (tdas2–= 1,2,5-thiadiazole-3,4-dithiolate; M = Ni, Pd, Pt) are reacted separately with CuI, it results in the formation of chain-like coordination polymers [Bu4N]2n[MII(tdas)2Cu4I4]n[M = Ni (compound 1), Pd (compound 2), Pt (compound 3)] in which each metal(bis)dithiolato complex unit supports a {CuI4I4} cluster unit. Two of the crystal structures and powder X-ray diffraction studies confirm that compounds 1, 2 and 3 are isomorphous with each other showing the abundance of a doubly-bridged “curved” chain-like structure formed by the coordination of two “N” donor atoms of each [MII(tdas)2]2–complex unit to two Cu+ions of two adjacent {CuI4I4} cluster units and by the coordination of two Cu+ions of a {CuI4I4} cluster with its neighbouring two [MII(tdas)2]2–complex anions through their “N” donor atoms from opposite sides. Since the [MII(tdas)2]2–complex anion generally has a planar geometry, which becomes bent upon supporting a {CuI4I4} cluster in the present study, the Cu–S interaction in [MII(tdas)2Cu4I4]2–is responsible for the bending conformation of the metal–dithiolato complex unit. This bending structure of the complex anion [MII(tdas)2]2–in [MII(tdas)2Cu4I4]2–describes a situation where the central part of the complex anion is pulled away towards the {CuI4I4} cluster through Cu–S bonds. This causes a “curve-like” structure throughout the resulting doubly-bridged chain in compounds 1, 2 and 3. The second important aspect of the present work is an interesting reactivity of this doubly-bridged coordination polymer with a bidentate chelating ligand, tetramethylethylenediamine (TMEDA). Compound [Bu4N]2n[NiII(tdas)2Cu4I4]n(1), a representative member of the series of compounds 1–3, was treated with TMEDA, which resulted in a square planar complex [Ni(tdas)(TMEDA)] (4) belonging to a mononuclear [MII(N2S2)]-type system (where N2= bidentate N∩N donor ligand, mostly a bipyridine type, and S2= dithiolato ligand) representing an important class of compounds for photophysical properties. Compound 4 exhibits emission at room temperature in the visible region.