Synthesis, crystal structures and conducting properties of heteroleptic nickel(II) 1,1-dithiolate-bpy/dppe ligand complexes

Abstract

New heteroleptic complexes, [Ni(LL′)] (L=2-(methylene-1,1′-dithiolato)-5,5′-dimethylcyclohexane-1,3-dione (L1), L′=2,2′-bipyridyl (bpy) 1; L=2-(methylene-1,1′-dithiolato)-1,3-indandione (L2), L′=1,2-bis(diphenylphosphino)ethane (dppe) 2) have been synthesized and characterized by elemental analysis, IR, NMR and UV–Vis spectroscopy, and their structures have been determined crystallographically. In the two structures, the Ni atom lies at the centre of a distorted square plane. In 1, the ligand L1 is uniquely bonded to the Ni atom in an adjacent molecule in a μ2, κ2 S,S-chelating–bridging manner, forming a weak dimer with a Ni…S distance of 2.96Å, which is shorter than the sum of the van der Waal’s radii of the Ni and S atoms. In 2 the steric restrictions of the bulky dppe ligand hindered any dimerization, but result in the formation of a rare intramolecular C–H…Ni anagostic interaction between the ortho hydrogen atom of the phenyl ring and the nickel centre, which has been assessed by theoretical calculations. The supramolecular structures of 1 and 2 are sustained by π(chelate)…π(bpy), C–H…O, C–H…π(chelate) and C–H…π(Ar) interactions. The two compounds are weakly conducting (σrt=10−7–10−5Scm−1), but show semiconducting behavior in the 303–363K temperature range.