Science · 2005 · 562 citations · 22 references
Natural SciencesChemistryMaterials ScienceComputational ChemistryCrystal StructureInorganic ChemistryChemical BondingCoordination ChemistryCrystal ChemistryMetal-ligand BondingMolecular BondingTransition Metal ComplexesBondingBonding In Coordination CompoundsCovalency In Metal-ligand BondsLocalized Molecular OrbitalsRoom Temperature StabilityRoom-temperature SynthesisSymmetry In Molecular OrbitalsX-ray Diffraction Analysis
Although in principle transition metals can form bonds with six shared electron pairs, only quadruply bonded compounds can be isolated as stable species at room temperature. Here we show that the reduction of {Cr(mu-Cl)Ar'}2 [where Ar' indicates C6H3-2,6(C6H3-2,6-Pri2)2 and Pr indicates isopropyl] with a slight excess of potassium graphite has produced a stable compound with fivefold chromium-chromium (Cr-Cr) bonding. The very air- and moisture-sensitive dark red crystals of Ar'CrCrAr' were isolated with greater than 40% yield. X-ray diffraction revealed a Cr-Cr bond length of 1.8351(4) angstroms (where the number in parentheses indicates the standard deviation) and a planar transbent core geometry. These data, the structure's temperature-independent paramagnetism, and computational studies support the sharing of five electron pairs in five bonding molecular orbitals between two 3d5 chromium(I) ions.
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Mononuclear and Polynuclear Chemistry of Rhenium (III): Its Pronounced Homophilicity
F. Albert Cotton, N.F. Curtis, C. Harris et al. · Science · 1964 · 415 citations