Metal-to-Ligand Ratio As a Design Factor in the One-Pot Synthesis of Coordination Polymers with [MS₄Cu_n] (M = W or Mo, n = 3 or 5) Cluster Nodes and a Flexible Pyrazole-Based Bridging Ligand

Two complexes, [WS 4 Cu 5 I 3 (bbd) 2 ] n ( 1 ) and [(WS 4 Cu 3 I) 2 (bbd) 3 ] n · n (DMF) ( 2 ), with one-dimensional polymeric chain structures containing hexanuclear and tetranuclear clusters linked by flexible 1,4-bis(3,5-dimethylpyrazol-1-yl)butane (bbd) ligands have been synthesized in facile one-pot reactions at room temperature, together with the molybdenum analogue of 2 . The only significant difference in the syntheses of the two tungsten complexes is the 5:1 or 3:1 molar ratio of copper(I) to [WS 4 ] 2–, the other experimental factors being kept constant. The observed products reflect the stoichiometric Cu:W ratio used. All three complexes were characterized by IR and UV–vis spectroscopy, thermal and elemental analyses, and single-crystal X-ray diffraction. Complex 1 contains an unusual and surprisingly unsymmetrical WS 4 Cu 5 I 3 cluster in which five Cu atoms bridge all but one of the six S···S edges of the WS 4 tetrahedron and the three I atoms all have different coordination modes (terminal, μ 2 and μ 3 ); it consists of two face-sharing WS 3 Cu 3 I distorted cubes, in one of which a Cu···I edge is opened up instead of being bonded, this Cu atom (shared by the two cubes) having an additional terminal iodo ligand. Complex 2 is the first reported example of a polymer containing (S=)MS 3 M′ 3 X cubes linked by organic ligands; pairs of these cube clusters are connected by pairs of bbd ligands, and the (cluster) 2 (bbd) 2 units are assembled into chains by single bbd bridges. In these and previously reported complexes, the bbd bridging ligand displays considerable flexibility, enabling it to support a range of discrete oligomeric and polymeric structures. X-ray powder diffraction shows that 2 is consistently obtained as a mixture of two polymorphs, and the same has been found for the corresponding molybdenum complex [(MoS 4 Cu 3 I) 2 (bbd) 3 ] n · n (DMF) ( 3 ), for which the second polymorph has been structurally characterized by single-crystal diffraction using synchrotron radiation. The two polymorphs have essentially identical polymer chain structures, with different packing arrangements of the chains and different symmetry properties.