A New Family of Low‐Spin CoIII Bis(amidate) Complexes with Two cis or trans Cyanides

Four low-spin dicyanodicarboxamidocobalt(III) complexes have been prepared from N,N′-bis(8-quinolyl)malonamide derivatives, the malonyl fragment of which was either unsubstituted (Et4N)[Co(BQM)(CN)2] (3a), monosubstituted by a benzyl group (Et4N)[Co(mono-BenzBQM)(CN)2] (3b), or disubstituted by two benzyl or two phenylethyl groups, (Et4N)[Co(di-BenzBQM)(CN)2] (3c) and (Et4N)[Co(di-PhEtBQM)(CN)2] (3d), respectively. The X-ray crystal structures of 3a and 3c reveal that the tetradentate ligand adopts a helical or a planar configuration around the cobalt centre of 3a and 3c, respectively. Complexes 3a−3d were characterised in solution by 1H NMR spectroscopy by 1D and 2D COSY H-H techniques. The solid-state structures of 3a and 3c are retained in solution, and complexes 3b and 3d adopt structures similar to 3a and 3c, respectively, showing that the level of the malonic substitution determines the configuration of the tetradentate ligand around the cobalt centre and forces the cyanide ligands to adopt either cis or trans orientations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)