Synthesis, Solid‐State Structures, and EPR Spectroscopic Studies on Polycrystalline and Single‐Crystal Samples of α‐Diimine Cobalt(II) Complexes

Cobalt compounds of the general formula [CoX 2 (α‐diimine)], where X = Cl or I and the α‐diimines are 1,4‐diaryl‐2,3‐dimethyl‐1,4‐diaza‐1,3‐butadiene (Ar‐DAB) and bis(aryl)acenaphthenequinonediimine (Ar‐BIAN) were synthesized by the direct reaction of the anhydrous cobalt salts CoCl 2 or CoI 2 and the corresponding α‐diimine ligand in dried CH 2 Cl 2 . The synthesized compounds are [Co(Ph‐DAB)Cl 2 ] ( 1a ), [Co( o , o ′, p ‐Me 3 C 6 H 2 ‐DAB)Cl 2 ] ( 1b ), and [Co( o , o ′‐iPr 2 C 6 H 3 ‐DAB)Cl 2 ] ( 1c ) with the ligands Ar‐DAB, and also [Co( o , o ′, p ‐Me 3 C 6 H 2 ‐BIAN)I 2 ] ( 2′b ) with the ligand Ar‐BIAN. The crystal structures of all the compounds were solved by single‐crystal X‐ray diffraction. In all cases the cobalt atom is in a distorted tetrahedron, which is built up of two halide atoms and two nitrogen atoms of the α‐diimine ligand. X‐band EPR measurements of polycrystalline samples performed on compounds 1b , 1c , and 2′b indicate a high‐spin Co II ion ( S = 3/2) in an axially distorted environment. Single‐crystal EPR experiments on compounds 1b and 1c allowed us to evaluate the orientation of the g tensor in the molecular frame. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)