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The pentacoordinated [Cr(CO)5]2- dianion in [2,2,2-crypt-K]2[Cr(CO)5] ethylenediamine monosolvate

Acta Cryst. (2011). C67, m202–m204 (

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The first penta-coordinated chromium–carbonyl compound [2,2,2-crypt-K]2[Cr(CO)5]∙NH2CH2CH2NH2 was obtained from the reaction of K3Cd2Sb2 and Cr(CO)6 in ethylenediamine in the presence of 2,2,2-cryptand. The central Cr atom is coordinated by five carbonyl ligands in a distorted trigonal bipyramidal geometry. In contrast to the case of the reported hexacoordinated [Cr2(CO)10]2- dianion, the pentacoordinated [Cr(CO)5]2- dianion has a longer apical Cr–C bond length than the equatorial ones as a consequence of less electron back donation to the axial carbonyl ligands.

J. Zhai and L. Xu