Polymeric 1,7-dithenylidene-1,4,7-triazaheptane copper(II) chloride with extended linear structure

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The crystal and molecular structures of [Cu 3(dienSS) 2Cl 6] where dienSS is a Schiffbase 1,7-dithenylidene-1,4,7-triazaheptane are reported. The compounds is polymeric with extended linear structure; it has a trimeric repeating unit in which two edge-sharing pseudooctahedral groups [Cu(dienSS)Cl 3] − are linked by single Cl bridges to a highly distorted tetrahedral [CuCl 4] 2− group. The space group is Pbcn, Z=4 with a=13.979(2), b=20.567(2), c=12.9481(9) A ̊ . DienSS, a potentially pentadentate ligand coordinates to Cu II as tridentate with dangling thiophene residues; it is located normal to the CuCu axis with CuN=2.026(7), 2.021(7) and 0.024(7) A ̊ . The three CuCl bonds completing Cu(dienSS) to a pseudooctahedron differ in length and position: CuCl=2.253(2) A ̊ is in the same plane as the three CuN; CuCl=3.029(2) A ̊ is perpendicular to that plane and takes part in the double bridge Cu(Cl) 2Cu; CuCl=3.133 A ̊ takes part in a single bridge with the [CuCl 4] 2− group. The [CuCl 4] 2− group is closer to a planar structure than to a tetrahedron: trans-ClCuCl angles are 154.0(2) and 157.2(2)°. The CuCl bonds are 2.286(2) Å (bridging to two different six-coordinate Cu units) and 2.226(3) Å (free). Both the elongated pseudo-octahedra and the planar structure are due to vibronic coupling. Molecular mechanics (MM), Austin Model 1 (AM1) and extended Hückel (EH) calculations suggest that electron delocalization to the thiophene groups occurs upon coordination.