Transition-metal(II) thiocyanate coordination compounds containing 4-allyl-1,2,4-triazole. Structure and magnetic properties.

Abstract

The synthesis and characterisation of a series of dinuclear and polynuclear coordination compounds with 4-allyl-1,2,4-triazole are described. Dinuclear compounds were obtained for Mn(II) and Fe(II) with composition [M 2(Altrz) 5(NCS) 4], and for Co(II) and Ni(II) with composition [M 2(Altrz) 4(H 2O)(NCS) 4](H 2O) 2. The crystal structure of [Co 2(Altrz) 4(H 2O)(NCS) 4](H 2O) 2 was solved at room temperature. It crystallizes in the monoclinic space group P2 1/ n. The lattice constants are a = 18.033(3) Å, b = 13.611(2) Å, c = 15.619(3) Å, β = 92.04(2)° Z = 4. One cobalt ion has an octahedrally arranged donor set of ligands consisting of three vicinal nitrogens of 1,2-bridging triazoles (CoN = 2.14–2.15 Å), one terminal triazole nitrogen (CoN = 2.12 Å) and two N-bonded NCS anions (CON = 2.08 Å). The other Co(II) ion has the same geometry, but the terminal triazole ligand is replaced by H 2O (CoO = 2.15 Å). The crystal structure is stabilised by hydrogen bonding through H 2O molecules, S-atoms of the NCS anions and the lone-pair electron of the monodentate triazole. The magnetic exchange in the Mn, Co and Ni compounds is antiferromagnetic with J-values of −0.4 cm −1, −10.9 cm −1 and −8.7 cm −1 respectively. The Co compound was interpreted in terms of an Ising model. For [Zn 2(Altrz) 5(NCS) 2]∞[Zn(NCS) 4], [Cu 2(Altrz) 3(NCS) 4]∞ and [Cd 2(Altrz) 3(NCS) 4]∞ chain structures are proposed. In the Cu compound thiocyanates appear to be present, bridging via the nitrogen atom, as deduced from the IR spectrum.