The crystal and molecular structure of the pentaco-ordinate complex tricarbonyl(triphenylphosphine)-σ-tetrafluoroethylcobalt(I)

Abstract

Crystals of trans-HCF₂·CF₂·Co(CO)₃PPh₃ are monoclinic, a= 9·675, b= 19·99, c= 11·975 Å, β= 91° 22′, space-group P2₁/c, final R 0·108 for 889 reflections. This pentaco-ordinate cobalt complex has trigonal bipyramidal geometry with the phosphine and fluorethyl groups occupying the axial positions. The Co–C distance to the –C₂F₄H group (1·95 Å) is slightly shorter than the expected single-bond length. Evidence for weak multiple bonding between the cobalt atom and fluoroethyl group is discussed. The conformation of the –C₂F₄H group is such that the hydrogen atom is directed towards one of the equatorial carbonyl groups (distance 2·6 Å). The possibility of a hydrogen–carbonyl group interaction is discussed. The Co–P bond length is 2·27 Å. Bond lengths and angles of the triphenylphosphine group differ slightly from those of free triphenylphosphine in the expected way.