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 pi system [NiII-((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).