Transition-metal(II) thiocyanate coordination compounds with 4-t-butyl-1,2,4-triazole. Structure and magnetic properties

Abstract

The synthesis, spectroscopy and structure of a series of t-Butrz coordination compounds with varying geometries is described. [Zn(t-Butrz) 2-(NCS) 2] is a mononuclear compounds, in which the Zn(II) ion is coordinated tetrahedrally. [Mn 2(t-Butrz) 4(H 2O)(NCS) 4] and its Fe(II) analogue are both asymmetrical dinuclear compounds. In the manganese compounds a small antiferromagnetic exchange ( J - 0.5 cm −1 is present. the crystal structure of [Co 3(t-Butrz) 8(NCS) 4]-(NCS) 2(H 2O) 9 was determined at room temperature. It crystallizes in the space group P2 1/ n, with lattice constants a = 15.616(3) », b = 14.168(4) », c = 19.517(7) », and β = 90.48(2)°. The unit cell contains two trinuclear units. In the linear trimer the Co centers are linked by three 1,2-bicoordinating t-Butrz groups (CoCo: 3.88 »). The central Co(II) ion is therefore coordinated by 6 t-Butrz ligands. For the terminal Co ions the octahedral coordination is completed by two N-donating thiocyanate anions (CoN: 2.10 ») and a monodentate coordinating t-Butrz (CoN: 2.13 »). The non-coordinating nitrogen atom of this triazole ligands is involved in hydrogen bonding (ON: 2.98 »). The magnetic properties of this compound can be described in terms of a S = 1 2 formalism. Application of the Ising model yields J = −13.2 cm −1 and g = 7.8. The magnetic interaction in the corresponding isostructural Ni compound is antiferromagnetic also ( J = 10.0 cm −1, g = 2.02). [Co 3(t-Butrz) 4(NCS) 6](H 2O) 2 is a trinuclear compound in which the central Co(II) ion is coordinated octahedrally, while the terminal Co ions reside in tetrahedral coordination sites. Attempts to replace the terminal Co ions by Zn(II) ions appeared to be successful. The magnetic exchanged in [Cu(t-Butrz) 2(NCS) 2](H 2O) 0.5 is antiferromagnetic and unusually strong. Based on spectral data a layer structure is proposed for this compound. Cd(t-Butrz) 1.5(NCS) 2 is a linear-chain type compound, containing alternating units of bridging ligands and unusual bridging NCS anions.