Transition Metal Thiocyanate Complexes of Picolylcyanoacetamides

A variety of transition metal complexes involving picolylcyanoacetamides (pica = NCCH2CONH-R; R = 2-picolyl- (2pica), 3-picolyl- (3pica), 4-picolyl- (4pica)) and thiocyanate have been synthesised and their solid-state structures have been determined. The complexes were all obtained from reactions between the corresponding metals salts and pica ligands with sodium thiocyanate under ambient conditions. Both 3pica and 4pica coordinate to the metal solely through the nitrogen atom of the picolyl group and form discrete tetrahedral [M(NCS)2(pica)2] (3pica; M = Mn, Zn; 4pica; M = Co) and octahedral [M(NCS)2(3pica)4] (M = Co, Fe, Ni) complexes. In addition, one-dimensional N,S-thiocyanate-bridged coordination polymers poly-[M(µ-NCS)2(pica)2] (3pica; M = Cd; 4pica; M = Co, Cd) were obtained. The ligand 2pica gave the discrete octahedral complexes [Co(NCS)2(2pica)2] and [Cd(NO3)2(2pica)2] in which 2pica chelates in a bidentate fashion through its picolyl and carbonyl groups. Magnetic susceptibility measurements on the cobalt(ii) complexes were performed and showed short-range antiferromagnetic coupling for the [Co(NCS)2(4pica)2]n 1D polymer.