Transition metal complexes with pyrazole-based ligands. XXII. Part XXI: Mészáros Szécsényi, Leovac, Kovacs, Pokol & Jaćimović (2005). Di-mu-thiocyanato-bis[(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa2N,N')(thiocyanato-kappaN)copper(II)] and a redetermination of bis(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa2N,N')bis(nitrato-kappaO)copper(II).

The title Cu(II) complex, [Cu2(NCS)4(C6H10N4)2], represents the first crystal structure of a polynuclear transition metal complex with the 3,5-dimethyl-1H-pyrazole-1-carboxamidine ligand (HL). It is compared with previously reported crystal structures of metal complexes with the same HL ligand. The molecule contains an eight-membered binuclear Cu2(NCS)2 ring, which is centrosymmetric and in a chair conformation. The Cu atom has a distorted square-pyramidal geometry with a very elongated Cu-S bond of 2.993 (2) A. The crystal structure redetermination of the bis(3,5-dimethyl-1H-pyrazole-1-carboxamidine-kappa(2)N,N')bis(nitrato-kappaO)copper(II)complex, [Cu(NO3)2(C6H10N4)2], and analysis of its hydrogen bonds confirm the significance of the NO3 groups in the formation of a three-dimensional hydrogen-bonding network. Both complexes are centrosymmetric, the inversion centre being located at the mid-point of the Cu...Cu line in (I) and the Cu atom being located at the inversion centre in (II).