Hydrazido complexes with metals

The most widely used methods for the syntheses of monohydrazido(2—) complexes have been from the parent hydrazide and metal oxo or halide complexes with formal elimination of water (equation 168), hydrogen halide (equation 169) or trimethylchlbrosilane (equation 170). The preparation of the hydrazido(2—) complexes, shown in equation (169) and (170), shows that the driving force for the formation of metal-nitrogen multiple bonds is such that the N hydrogens are lost. 

Extensive studies of the mechanism of formation of dialkylhydrazido(2—) complexes from [Mo(N2)2(dppe)2] (M = Mo, W) have revealed a free radial mechanism for addition of the first alkyl group with loss of one N2 molecule as the rate-determining step.484 Addition of the second alkyl group proceeds via an SN 2 mechanism (see Scheme 6) and the effect of the metal and coligands on reaction rates has been studied in detail.485 Acoyl and aroyl hydrazido(2 —) complexes can be obtained by reaction of the N2 complexes with acoyl or aroyl halides in the presence of acid (equation 177).486... 

Reactions of metal-NjR complexes with protonic acids yield hydrazido complexes ... 

Another synthesis of alkyldiazenido complexes is due to Chatt et al. (1977 b), and independently to the work of Hidai et al. (1976 b), namely a route by condensation of hydrazido(2 —) metal complexes with aldehydes or ketones. The original work of Hidai et al. (1976 a) concentrated on molybdenum complexes, that of Chatt et al. (1977 b) on tungsten, but both groups used the same type of ligands as their starting material complexes, namely [Mo(NNH2)(dppe)2] X (X = F, Cl, Br or I). The... 

These complexes are considered according to the mode of bonding of the hydrazido fragment. The known coordination types are shown in valence bond representations in Figure 15 together with the formal charge, geometry and numbers of valence electrons donated to the metal. 

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