title: The pentacoordinated [Cr(CO)5](2-) dianion in [2,2,2-crypt-K]2[Cr(CO)5] ethylenediamine monosolvate.
abstract: Bis[(4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane)potassium(+)] pentacarbonylchromate(2-) ethylenediamine monosolvate, [K(C(18)H(36)N(2)O(6))](2)[Cr(CO)(5)]·C(2)H(8)N(2), was obtained from the reaction between K(3)Cd(2)Sb(2) and Cr(CO)(6) in ethylenediamine in the presence of the macrocyclic 2,2,2-crypt ligand. The structure provides the first crystallographic characterization of the pentacoordinated [Cr(CO)(5)](2-) dianion. The central Cr(III) atom is coordinated by five carbonyl ligands in a distorted trigonal-bipyramidal geometry. The distribution of the Cr-C bond lengths indicates a greater degree of back bonding from Cr(III) to the equatorial carbonyl ligands compared with the axial carbonyl ligands.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on Structure, Chinese Academy of Sciences, Fuzhou 350002, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhai
authors.forename: Li
authors.initials: L
authors.lastname: Xu