Triple-bonded complexes

The use of functionalized isocyanides containing both the isocyanide function and the nucleophile in the same molecule leads to complexes with heterocyclic carbene ligands via a 1,2-addition across the C=N triple bond. Complexes with functionalized isocyanide ligands can be generated in template reactions or a nucleophile functionalized isocyanide can be reacted directly with a suitable metal complex. 

For the analogous cyclopentadiene(3 ee Cyclopentadienyl) derivative, prepared by a different route, the complex is unstable in solution and is believed to dissociate back to H2 and the Mo-Mo triple-bonded complex. In view of the fact that many catalytic cycles utilize hydrogen, these types of complexes are important models. Interactions of dihydrogen leading to cleavage of the metal-metal bond are discussed in Section 7.1.4. 

Reduchve elimination of hydrocarbons or their derivatives is another viable route to metal-metal bonded systems. A good example is dinuclear reductive elimination, as studied by Bergman and coworkers (equation 53). In this case, both the single and triple-bonded complexes are formed. Exposure to CO instantly converts the triple-bonded complex to the single-bonded one. 

In an attempt to synthesize M=Pb triple bond complexes. Power etal. obtained metallaplumbylenes of the type L M-Pb-Ar (M = Cr, Mo, W and Ar = 2,6 Trip2C6H3) of group 6 metals by salt elimination, as shown in equation (17). ... 

This derivative is then conjugated to propargylamine by peptide coupling in the presence of NHS and EDAC and the triple bond complexed by Co2(CO)g to yield the atrazine tracer 30 (Scheme 8.14) [44]. 

In order to prepare polycarbosilanes containing organometallic fragments which could be precursors of transition-metal-containing ceramics , 120 was reacted with dicobalt octacarbonyl to give 121 with approximatively half of the triple bonds complexed with Co2(CO)6 moieties (equation 68). )j -Complexation of the silole ring was performed... 

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