One trimetallic compound (μ-η2-Ni-1)[W(CO)5]2 (NiW2) was prepared by reaction of the Ni(II) dithiolate metalloligand, [Ni-bme-dach] where bme-dach = bis-(mercaptoethyl)diazacycloheptane, with W(CO)6 in CH2Cl2 under a certain treatment. Two solvent-free polymorphs of NiW2 (I and II) and two solvates NiW2(CH2Cl2) (III) and NiW2(C6H6) (IV) were obtained by crystallization in various solvent conditions. Conformations I and II exhibit concomitant polymorphisms in CH2Cl2 solvent system. However, conformations of III and IV were obtained in mixed solvent system of CH2Cl2 with CHCl3 and benzene, respectively. For morph II*, it was obtained by heating treatment of conformation II at 160 °C for 20 min. Two low-valent metallic W0(CO)5 groups in I to IV were bridged by Ni-1 in the transoid modes, giving W-W distances of 5.576(17) A to 6.024(3) A.
