Polynitrile anions as ligands: synthesis, structure and magnetic properties of a new three-dimensional coordination polymer with the 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide (tcpd2−) bridging ligand

Reaction between CuCl2 and K2tcpd (tcpd2− = {C[CN)2]3}2− = 2-dicyanomethylenc-1,1,3,3-tetracyanopropanediide anion) in presence of the neutral ligand tn (1,3-diaminopropane) in aqueous solution yields the new compound [Cu(tn)(tcpd)] (1) which was characterized by X-ray crystallography. The crystal structure of 1 consists of one [Cu(tn)]2+ unit and one tcpd2− anion, both located on general positions. Each Cu atom presents an essentially octahedral coordination with four nitrogen atoms arising from four polynitrile ligands and two nitrogen atoms from the chelating tn ligand. Despite its six nitrile groups potentially bridging, the tcpd ligand acts with a μ4-bridging mode via four nitrogen atoms of two different C(CN)2 wings leading to a 3D structure. The magnetic behavior for compound 1 shows a very weak antiferromagnetic coupling of the Cu(II) ions through the NCCCN bridge that can be very well reproduced with a regular S = 1/2 antiferromagnetic chain model with g = 2.108 and J = −0.042.