Crystal structure of (18-crown-6)potassium(I) [(1,2,3,4,5-η)-cycloheptadienyl][(1,2,3-η)-cycloheptatrienyl]cobalt(I)

Abstract

The reaction of bis(anthracene)cobaltate(−I) with excess cycloheptatriene, C7H8, resulted in a new 18-electron cobaltate containing two different seven-membered ring ligands, based on single-crystal X-ray diffraction. The asymmetric unit of this structure contains two independent cation–anion pairs of the title complex, [K(18-crown-6)][Co(η3-C7H7)(η5-C7H9)], where 18-crown-6 stands for 1,4,7,10,13,16-hexaoxacyclooctadecane (C12H24O6), in general positions and well separated. Each (18-crown-6)potassium cation is in contact with the η3-coordinating ligand of one cobaltate complex. Each η3-coordinating ligand behaves as an allylic anion whoseexo-diene moiety is bent away from the allylic plane, and thus is not involved directly in the bonding. The metal-coordinating portions of the anionic η5ligands are planar and one of these ligands is modeled as disordered over two positions, with occupancy ratio 0.699 (5):0.301 (5), such that one orientation is rotated by one carbon atom with respect to the other. The diffraction intensities were integrated according to non-merohedral twin law [-1 0 0/0 -1 0/0.064 0 1], a 180° rotation about reciprocal lattice axis [001], and the masses of the twin domains refined to equal amounts. As both ligands are formally coordinated as anions, the cobalt atom is best considered to be CoI. This compound is of interest as the first to possess cycloheptatrienyl and cycloheptadienyl ligands in an anionic metal complex.