Formation of Metal Carbyne Complexes

Compared to the CO insertion into the M — tr-carbyl bond, the reaction of this type for isocyanide ligands proceeds more readily, giving iminoacyl groups which are thermodynamically more stable than the acyl ligands. Thus, in contrast to the acyl groups, they do not undergo the reverse reaction, i.e., deinsertion. 

multiple insertion reactions may occur leading to the formation of polyimine ligands [equation (12.47)]. Alkyl iodides and Ni(CNBu )4 afford pentaimine complexes (12.48). The metal-nitrogen bond of the polyimine complexes may be broken by the 

Niobium and tantalum halides also react with isocyanides to give migration products [equation (12.51)]. Azide complexes react with CNR to afford coordination compounds with tetrazolyl [equation (12.52)]. Codimerization and cooligomerization of 

Some compounds of transition metals may react with isocyanides to give RN = C = C=NR dimers. Niobium and tantalum compounds of the type M2Cl6(SMe2)3 which possess metal-metal double bonds of the configuration (M = M bond distances ca 265 pm) react with various isocyanides to furnish the follow- 

A complex containing another ligand which arises as a result of the formation of a bond between carbon atoms of two isocyanide molecules may be prepared by the reaction of [Mn(CNMe)(CO)4] with methyl iodide [structure (12.58)].  

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