Metal bonded complexes, bridged

As will be seen in later sections, the complexes in which the heteronuclear metal-metal bonds are bridged by agostic B—H—- metal interactions are intermediates in a variety of reactions involving the carbaborane cages and the /i-alkylidyne ligands. 

Novel Types of Metal-Metal Bonded Complexes Containing Allyl and Cyclopentadienyl Bridging Ligands, 19, 155... 

Table II. Photochemistry of Bridged Dinuclear Metal-Metal Bonded Complexes.

An increasing area of interest and utilization of metal-metal bonded complexes is the area of electrical conduction at the molecular level. A prototypical complex is shown in Figure 1, which incorporates a diphosphine-bridged Pt -Pt dimer sphced to two linear acetylenic linkages terminated by ferrocenyl see Ferrocene) groups as endcaps. 

Figure 6 Preparation of bridging acetylene dendrimeric metal-metal bonded complexes. (Reprinted with permission from Ref 8. 2003 American Chemical Society)...

It should also be considered that, due to the high mobility of the ligand, linear hydrido-bridged species might readily transform to transition states involving hydrido-bridged metal-metal bonded complexes. 

Bridging ligands are normally innocent or spectators and do not play an active role in chemical reactions. This is not always the case, however, particularly for coordinated sulfur. For example, reaction of the sulfur-bridged metal-metal bonded complexes with hydrogen, followed by reaction with acetylene, occurs at the sulfur, as investigated by Rakowski Dubois (equation 25). ... 

In addition to monocyclopentadienyl dimers, various molybdenocene derivatives can form dimers, as shown in equation (33). This is one example of a vast range of organic ligands that bridge metal-metal bonded complexes. Another example is one of the several products obtained by reaction of diphenylacetylene and molybdenum carbonyl (equation 34). 

A few stable metal-metal bonded complexes (70) have been described. They are synthesized by reaction of a zirconium dichloride complex with an organometallate of iron or ruthenium (see following section). CO2 and CS2 insertion into the polar metal metal bond affords hetero dinuclear complexes of the second family (71) (Scheme 18). The /U.-OXO complexes are representative complexes of the (71) group. They are readily prepared by the smooth hydrolysis of most metallocenes. Arrangement (71) is also present in the methyl-bridged homo dinuclear species (77) formed by reaction of methylzirconocene cation with Cp2ZrMc2. 

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