The crystal and molecular structure of bicyclo[2.2.1]-hept-2-en-5,6-dinitrosocobalt-η 5-cyclopentadienide. Evidence for a nitroxyl diradical bidentate ligand

Abstract

An accurate X-ray crystallographic structural study of a metal complex having a nitroxyl diradical as a bidentate ligand has been carried out. Bicyclo[2.2.1]-hept-2-en-5,6-dinitrosocobalt-η 5-cyclopentadienide crystallizes in space group P 1 with Z 2, a 8.245 ± 0.007, b 10.285 ± 0.016, c 7.888 ± 0.008 Å and α 59.276 ± 0.073, β 101.099 ± 0.053, γ 108.802 ± 0.067°. Intensities of 1831 independent reflections were used in the refinement of the structure to an R( F) of 4.6%. The bonding of the Co atom to the cyclopentadienyl ligand appears to be a normal pentahapto linkage. The lone double bond and the CC single bonds adjacent to the endo hydrogens of the norbornene fragment of the molecule are shorter than have previously been reported for this moiety. This study represents the first structural report of NO groups bridging to Co. The CoNO angles (129.4(3) and 128.9(3)°) and the NO stretching frequency (1357 cm −1) of the title compound resemble values found in nitroxyl free radical compounds more closely than values found in bridging NO group compounds.