Hydrazido ligand

A similar reaction with the formation of elemental hydrogen was observed when dimethylaminoalane (Me2NAlH2)3 was treated with 1,1-dimethylhydr-azine [Eq. (10)] [26]. All dimethylamino substituents were replaced by terminal hydrazido groups (24 66% yield). Dianionic hydrazido ligands analogous to compound 23 were formed. They occupy bridging positions... 

Four-membered heterocycles (B). They have the negatively charged nitrogen atoms of the hydrazido ligands in a bridging position between two metal atoms. Both N—N bonds are exocyclic and adopt a trans position in the solid state. In solution, an equilibrium between cisitrans isomers was detected by temperature dependent NMR spectroscopy in many cases. 

Six-membered heterocycles (D). Both N—N bonds are included in the central ring of the molecules, which usually adopt a chair conformation. Each aluminum atom is coordinated by a negatively charged amido nitrogen atom and by an amino NR2 group of different hydrazido ligands. 

Alkynes insert in the Zr-N bond of a chelating J7 -hydrazido ligand to give a 2,3 diazametallacyclopentene. The strain of the three-membered hydrazido metallacycle clearly enhances its reactivity towards insertion (Scheme 6.67) [209]. 

Returning now to the importance of the hydrazido ligand as an intermediate in dinitrogen reduction, it is noted that hydrazido complexes can be isolated from many reactions that ultimately give ammonia if allowed to continue, e.g.. Equations... 

Here, terminal bonding of the hydrazido ligand takes place. This is attributed to the low donor ability of the nitrogen atom bearing the electron withdrawing 2,4-dinitrophenyl moiety. 

The complexes [CpMo(NNRPh)2(PPh3)], where R = Me or Ph, have vNN of the organo-hydrazido ligands at 1589 cm"h Similar values were seen in Tp Mo(NNPPh)2Cl, where Tp = hydridotris(3,5-dimethylpyrazolyl)borate, R = Me or Ph. In Cp WCl3(NNPh2) vNN of the hydrazido ligand is at 1585... 

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