Charge distribution in dioxygen complexes of cobalt(III). The crystal structure and absolute configuration of (+)546-Δ-cis-β-[{2,13-dimethyl-6,9-diphenyl-2,6,9,13-tetraarsatetradecane}(dioxygen)cobalt(III)] perchlorate

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Abstract
The crystal structure and absolute configuration of an optically active dioxygen complex of cobalt(III) have been determined from three dimensional X-ray diffraction data collected by counter techniques. (+)546-Δ-cis-β-[Co{R,R-(CH3)2As(CH2)3As(C6H5)(CH2)2As(C6H5)(CH2)3As(CH3)2}O2]ClO4 crystallizes in the orthorhombic space group P212121, in a unit cell of dimensions a = 12.595(7), b = 20.937(10), and c = 11.509(6) Å. There are four formula units per cell. The structure was refined on F by full matrix least-squares techniques, and converged with an agreement factor R = 0.0474 based on 2988 independent observations collected from two crystals. The absolute configuration of the cation was determined by the Bijvoet absorption edge technique to be Δ. The tetradentate ligand adopts the cis-β configuration around the cobalt atom. One six-membered ring has a chair conformation; the other is disordered, and occurs with equal probability in a chair and a distorted boat conformation. The five-membered chelate ring has a gauche conformation, of absolute configuration λ. The absolute configurations at the asymmetric arsenic atoms are both R. The O—O bond length is 1.424(10) Å. The assignment of formal oxidation states to the cobalt atom and the dioxygen ligand is discussed in light of the molecular geometry and the optical properties of the cation.

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