Quadruple Bonds between Transition Metal Atoms

Quadruple Bonds between Transition Metal Atoms 

Molecules with more than one transition metal atom have been known since 1850, but even Alfred Werner (see chapter 1) did not consider the possibility that they contained direct metal-metal bonding. It is noteworthy that the mercurous ion has been known to be Hg2 since the 

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Quadruple Bonds between Transition Metal Atoms... 

The rapid advances in synthetic and structural chemistry of the metal-metal bond have inspired detailed theoretical investigation. Unlike main group elements such as carbon, transition metals can form a quadruple bond between two metal atoms. The quadruple bond consists of a single a bond (overlap of two dz2 orbitals), two degenerate n bonds (overlap... 

Although less numerous than complexes containing heavier transition metals, some cases are known in which there is a quadruple bond between first-row metals. One very interesting complex of this type is [Cr2(C03)4(H20)2] in which the carbonate ions form bridges between the two metal atoms as shown in Figure 21.25. 

During the succeeding decades, many thousands of cluster compounds of transition metals have been synthesized, including hundreds containing quadruple bonds. Therefore, we need to consider briefly how metal atoms can bond to each other and, in particular, how quadruple bonds between metals are possible. 

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