HIGH-SPIN FOUR AND SIX-COORDINATE COBALT(II) COMPLEXES WITH 3,5-DIMETHYL PYRAZOLE

Abstract

Abstract The reaction of cobalt dichloride hexahydrate with two equivalents of 3,5-dimethyl pyrazole under reflux in THF gave a deep blue solution of Co(3,5-dimethylpyrazole) dichloride. Suitable crystals for X-ray structural determination were grown in THF. The structural assignment of (1) was made by elemental analysis and electronic spectroscopy and confirmed by single crystal X-ray diffraction studies. The crystal structure reveals that compound (1) crystallizes in the monoclinic space group C2/c with eight molecules in the unit cell of dimensions a = 15.012(2), b = 8.275(1), and c = 24.047(2)A, and β = 96.05 (1)°. The structure has been refined to an R(F) factor of 0.045 based on 1670 observed reflections. The geometry around the Co(II) center is best described as tetrahedral. The four ligating atoms consist of two chlorine atoms and two nitrogen atoms from the 3,5-dimethyl pyrazole. The solution electronic spectra of (1) in acetone and THF are consistent with the solid state crystal structure. Howev...