Bonding between chromium atoms

11 Electron density in the metal-ligand plane of dichromium tetraacetate, (a) Molecular diagram, (b) deformation density through Cr—Cr and the acetyl group averaged over equivalent regions. Contours are at 0.10 eA-3. Negative contours are broken lines. Source Benard et al. (1980). 

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Introduction and survey/Multiple bonds in dirhenium and ditechnetium compounds/ Multiple bonds in dimolybdenum and ditungsten compounds/Multiple bonding between chromium atoms/X3M=MX3 compounds of molybdenum and timgsten/ Diruthenium and diosmium compounds/Dirhodium compounds/Dimetal com-... 

In the 1960s quadruple bonds between metallic atoms were discovered in species such as Re2Clg . There would be no obvious way to explain quadruple bonds with cubic atoms or tetrahedra. In 2005, evidence was presented for a quintuple bond between the two chromium atoms in a crowded dichromium complex (RCrCrR). ... 

A number of reviews contain relevant material such as those on dimolybdenum and ditungsten complexes, substitution reactions of chromium complexes, the reactivity of complexes containing multiple bonds between metal atoms, model reactions of coupling ieactions2 5, and in a review principally on ruthenium chemistry.216... 

The complex might be best described by saying that each oxygen atom could form a double bond with the chromium atom with the. use of either one of its two 7t orbitals and the accompanying pair of electrons, extra stability being achieved through the resonance between the two kinds of double bonds. 

In this chapter we illustrated how the CASSCF/CASPT2 method can be used to explore the nature of such chemical bonds. Classic cases are the Re-Re multiple bond in Re2Cl, and the Cr-Cr bond ranging from the quadruply bonded Cr(II)-Cr(II) moiety to the formal hextuple bond between two neutral chromium atoms. The bonding between the 3d5 electrons is weak and should be considered as an intermediate between two pairs of antiferromagnetically... 

The bond distances between the chromium atoms and the terminal oxygen atoms become 1.629 A (27), which is longer than in chro-mium(VI) oxide but shorter than in the chromate ion (the bonds from the chromium to the central oxygen are 1.748 A). 

The Ji-complexes formed between chromium(O), vanadium(O) or other transition metals, and mono- or poly-fluorobenzene show extreme sensitivity to heat and are explosive [1,2], Hexafluorobenzenenickel(O) exploded at 70°C [3], and presence of two or more fluorine substituents leads to unstable, very explosive chromium(O) complexes [1]. Apparently, the aryl fluorine atoms are quite labile, and on decomposition M—F bonds are formed very exothermically. Laboratory workers should be wary of such behaviour in any haloarenemetal Ji-complex of this type [1]. However, in later work, no indications of explosivity, or indeed of any complex formation, were seen [4]. Individually indexed compounds are ... 

In the structure, the copper (or chromium) atom has a greatly distorted octahedral coordination, with two bond distances much longer than the other four (difference = 0.38 A for Cu, 0.36 A for Cr) and small, but significant differences between the pairs of short distances. The major distortion is correlated with the d9, or high-spin d4, electronic configuration of Cu(II) and Cr(II), respectively, giving an uneven occupation of the eg orbitals—the Jahn-Teller effect. The differ-... 

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