Crystal structure of µ-[1,2-bis(dimethylarsino)tetrafluorocyclobutene-AsAs]-di-µ-carbonyl-bis-(dicarbonylcobalt)(Co–Co)

Abstract

Crystals of the title compound, Me₂As[graphic omitted]F₂·Co₂(CO)₆ are orthorhombic, a= 16·749(4), b= 13·719(4), c= 18·316(3)Å, Z= 8, space group Pbca. The structure was determined by direct and Fourier methods, and refined by block-diagonal least squares calculations to R 0·058 for 1688 observed reflexions. The structure shows a marked resemblence to that of Co₂(CO)₈. Each cobalt atom lies 0·4 Å out of the plane formed by the two carbon atoms of the bridging carbonyl groups, the arsenic atom, and the carbon atom of the appropriate terminal carbonyl group. The two planes of this type in the molecule meet at an angle of 88°; thus the cobalt atoms are octahedrally co-ordinated, the ‘bent metal–metal bond’ occupying the sixth co-ordination position. The Co–Co bond length is 2·483(4)Å.