Molecular and Electronic Structures of Homoleptic Nickel and Cobalt Complexes with Non‐Innocent Bulky Diimine Ligands Derived from Fluorinated 1,4‐Diaza‐1,3‐butadiene (DAD) and Bis(arylimino)acenaphthene (BIAN)

The diimine complexes with bulky fluorinated N ‐substituents [Ni II ( F DAD) 2 ] 1 and [Co II ( F DAD) 2 ] 2 [ F DAD = N , N′ ‐bis(pentafluorophenyl)‐2,3‐dimethyl‐1,4‐diaza‐1,3‐butadiene]as well as diimine complexes with extended π system [Ni II ( F BIAN) 2 ] 3 and [Co I ( F BIAN) 3 ] 4 ( F BIAN = bis[ N ‐{3,5‐bis(trifluoromethyl)phenyl}imino]acenaphthene) were synthesized. Compound 4 represents the first complex with three bis(imino)acenaphthene ligands synthesized so far. The molecular structures of the complexes 1 – 4 were determined by X‐ray crystallography at 193 K. Complexes 1 , 2 and 3 comprise the divalent metal ions with pairs of radical monoanionic ligands, whereas 4 is best described as a cobalt(I) complex with two neutral ( F BIAN) 0 and one ( F BIAN) 1– ligand in the radical monoanionic form. The electronic structures of the paramagnetic cobalt complexes 2 and 4 were investigated by SQUID measurements and X‐band EPR spectroscopy. Both complexes possess a doublet ground state, with electron density located mostly in the metal d‐orbitals. The doublet–quartet energy gap for 4 was established to be 159 cm –1 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)