Cyano benzene functionalised Ni and Cu bisdithiolene complexes

Abstract

New nickel and copper bisdithiolene complexes were prepared as tetraphenylphosphonium (Ph₄P⁺) salts, (Ph₄P)_n[M(3cbdt)₂], [n = 1, 2; M = Ni, Cu; 3cbdt = 3-cyanobenzene-1,2-dithiolate]: (Ph₄P)₂[Ni(3cbdt)₂] (1); Ph₄P[Ni(3cbdt)₂] (2); (Ph₄P)₂[Cu(3cbdt)₂] (3); Ph₄P[Cu(3cbdt)₂] (4), and characterised by single crystal X-ray diffraction, cyclic voltammetry, EPR and static magnetic susceptibility for the paramagnetic species. These Cu and Ni complexes obtained as stable monoanionic and dianionic anions are the first members of this family of cyano benzene functionalized bisdithiolene transition metal complexes, opening the way to the preparation of analogous compounds with other transition metals and their future use as building blocks for the preparation of molecular materials. Their properties are discussed in comparison with the corresponding complexes based on the 4-cyanobenzene-1,2-dithiolate (4cbdt) ligand previously described by us. The salts (Ph₄P)_n[M(3cbdt)₂], [n = 1, 2; M = Ni, Cu] present the metal complexes always in a square-planar coordination geometry with a ligand trans configuration, but revealing a rich polymorphism. The Ni and Cu compounds are isostructural and occur as two polymorphs (α, β) with the exception of the salt of the monoanionic Ni complex, that was found only as the α-polymorph. The salt of the dianionic Ni complex was found to crystallise also with one acetonitrile molecule, when recrystallised from this solvent. The salts of monoanionic [Ni(3cbdt)₂] and dianionic [Cu(3cbdt)₂] complexes have been characterised by EPR and static magnetic susceptibility as paramagnetic S = 1/2 species.