[2,2,2-Crypt-Na]₂[Cr₂(CO)₁₀]: a Chromium(-1) Carbonyl Structure with a Very Weakly Coordinating Cation

The title compound, bis[(1,10-diaza-4,7,13,16,21,24-hexaoxabicyclo[8.8.8]hexacosane)sodium(+)] decacarbonyldichromate(Cr-Cr)(2-), [Na(C₁₈H₃₆N₂O₆)]₂[Cr₂(CO)₁₀], has been prepared by the reduction of [Cr(CO)₆] with Na₂Tl in dimethylformamide followed by the addition of the macrobicyclic ligand, 2,2,2-crypt in ethylenediamine (en) solvent. The geometric parameters observed for the anion in the title salf differ significantly from those reported previously for the DME solvated (DME = 1,2-dimethoxyethane) K⁺ and [PPN]⁺ {[PPN]⁺ = bis[bis(triphenylphospine)iminium]} salts, reflecting the more weakly coordinating nature of the [2,2,2-crypt-Na]⁺ cation.