The ligating versatility of pseudohalides like thiocyanate and cyanate in copper(II) complexes of 2-benzoylpyridine semicarbazone: Monomer, dimer and polymer

Abstract

Three new copper(II) complexes [Cu(bpsc)(NCS)]n (1), [Cu(Hbpsc)(NCS)2] (2) and [Cu(bpsc)μ2(NCO)]2 (3) of a semicarbazone Hbpsc (where Hbpsc=2-benzoylpyridine semicarbazone) with pseudohalides like thiocyanate and cyanate have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measurements, FT-IR, UV–Vis and EPR spectral studies. The interesting amido-iminol tautomerism enables the proligand to exist in amido form as well as deprotonated iminolate form thereby functioning as tridentate NNO donor, coordinating through pyridyl nitrogen atom, azomethine nitrogen atom and amido/iminolate oxygen atom in the complexes. Versatile coordinating behavior of pseudohalides gives rise to complexes with different nuclearities. Single crystal XRD studies showed that [Cu(bpsc)(NCS)]n (1) is a one dimensional polymer connected by single end-to-end (μ1,3) thiocyanate bridges whereas [Cu(Hbpsc)(NCS)2] (2) is monomeric in nature in which copper(II) center is bonded to two terminal thiocyanate groups. [Cu(bpsc)μ2(NCO)]2 (3) is an end-on cyanato bridged binuclear species and found to exhibit packing polymorphism. In all complexes, g values in frozen DMF indicate the presence of the unpaired electron residing in the dx2-y2 orbital.