[2,2,2-Crypt-K]₂[Cr₂(CO)₁₀]: the First Dinuclear Metal Decacarbonyl Dianion Structure with an Eclipsed Geometry

Bis[)1,10-diaza-4,7,13,16,21,24-hexaoxabicyclo[8.8.8]hexacosane)potassium(+)] eclipsed-decacarbonyldichromate Cr-Cr(2-), [K(C₁₈H₃₆N₂O₆)]₂[Cr₂(CO)₁₀], was obtained from the reaction between the trigonal bipyramidal Pb₂Ch₃^2- anions (Ch = Se, Te) and Cr(CO)₆ in ethylenediamine (en) solvent and in the presence of the macrobicyclic ligand, 2,2,2-crypt. The anion geometry is eclipsed (approximate D_4h point symmetry) and contrasts with the staggered geometry (approximate D_4d point symmetry) observed for the anion in the [2,2,2-crypt-Na]⁺, DME-solvated K⁺ (DME is 1,2-dimethoxyethane), and PPN⁺ {PPN⁺ is bis[bis(triphenylphosphine)iminium]} salts.

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