Tungsten hydrazido 2-1 complexes

An in situ 15N-NMR study of the protonation reactions of molybdenum and tungsten dinitrogen complexes has shown that signals arise in the early stages of the reaction which can be assigned to relatively stable hydrazido(2-) species (4). With careful choice of acid and conditions, thermally stable hydrazido(2-) complexes can be isolated. They often yield ammonia and/or hydrazine upon further protonation (4,105), for example, reaction (43). 

Cl) . Also exploring reaction mechanisms, Rheingold and coworkers have examined the electrophilic reactions between zerovalent tungsten nitrenes and hydrazido complexes and phosphines . ... 

The electrocatalytic properties of several parent dinitrogen or hydrazido-containing molybdenum and tungsten complexes with dppe ligand have also been investigated. Each of these complexes yielded NH3, in chemical yields which ranged from 1% to 36% per mole of complex.318... 

Hydrazido(2-) and hydrazido(l-) complexes have also been shown to condense with aldehydes and ketones to give diazoalkane complexes containing the W=N—N=CRiR2 unit.387,388 Treatment of these complexes with LiAlFL, gives secondary amines and ammonia, whereas treatment with acid produces hydrazine, keto azines and N2-free tungsten compounds. Amines can also be produced from organohydrazido(2—) complexes.389,390... 

Despite the fact that hydrazido(2—) complexes are in general restricted to the metals molybdenum, tungsten, and rhenium, a great variety of coordination sites (various coligands) have been realized. Four general routes have been employed to yield this class of compounds (143, 275, 317). 

The hydrazido(l-) tungsten(VI) shown in Figure 5 was produced from the triflate complex [W(NAr) 2,6-NC5H3(CH2NTosyl)2 (OTf)Cl ] (Ar = 2,6-C6H3-i-Pr2) and 2 equiv. of hydrazine. 

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... 

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