Hydrazido 2— > complexes reactions

A general approach to rhenium hydrazido complexes is the reaction of oxo or chloro compounds with organohydrazines as has been demonstrated in an early report with the synthesis of [Re NNC(Ph)0 Cl2(PPh3)2] (310), " the molecular structure of which was solved in 1988. A detailed study on [Re(NNR)Cl2(PPh3)2] complexes with R = COPh or phthalazine shows that the course of subsequent reactions is governed both by the nature of the donor group R responsible for chelate closure and by the type of donor ligand introduced. No simple substitution chemistry has been observed for R = phthalazine. The benzoyl compound... 

The reaction of cis- [PtCl2(PMexPh3 x)] (x = 1—3) with either dibenzoyl- or diacetyl-hydrazine in EtOH has yielded new hydrazido-complexes 150 1H n.m.r. and also unpublished X-ray data reveal the hydrazide to be in the enolized form (41). 

I7A (R = Me), and ZN-Mo-N = 38°, with a linear Mo-N-0 bond. Reaction of this species with HCl caused regeneration of the nitrosyl chloro precursor without cleavage of the hydrazido N-N bond. Other hydrazido complexes are described in Section 5.4. 

The bis(titanium)hydrazido complex formed by HCl reaction with (h -Cp)2TiN2MgCl in MeOH reacts further with HCl to produce ... 

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

We have made several other V" complexes by displacing the hydrazine ligand in [V(N2H4)(NS3)] with Cl , N3 CN , MeCN or CNBu , and have prepared a series of imido-complexes [V(NAr)(NS3)] (Ar = various substituted phenyl groups), and of hydrazido-complexes [V(NNR R )(NS3)] (R R = methyl or phenyl) from reactions of [V(0)(NS3)] with aryl isocyanates or 1,1-disubstituted hydrazines, respectively. Structural studies on several of these compounds always reveal trigonal bipyramidal coordination about the V atom. The V-N distance in the V(NS3) system, as a result of the shape of the NS3, is sensitive to... 

Successful reactions of complexes 15 and 33, some occurring in very high yield, with various organic halides (Equations 14-19) will be presented in approximately chronological order. Acyl and aroyl chlorides react to form hydrazido and diazenido complexes, respectively. The latter complexes were treated with one mole of hydrogen chloride to form the hydrazido complexes.The hydrazido complexes can be deprotonated reversibly to give the corresponding diazenido complexes (Equation 14) ... 

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... 

Recently, the first mechanistic study of the conversion of a coordinated dinitrogen to a hydrazido complex was reported/ Treatment of cis-[M(N2)2(PMe2Ph)4] with excess HCl, HBr, or H2SO4 in methanol yields [M(NNH2)(OMe)2(PMe2Ph)3] in a reaction that would ultimately give ammonia. The stoichiometry of the reaction is shown in Equation (27) ... 

How are the hydrazido complexes of molybdenum converted to ammonia First, the stoichiometry of this latter reaction must be reexamined (Equation 29), since it implies N-N bond cleavage to... 

A proposed reaction pathway by which ammonia is formed is shown in Scheme 6. After the dissociation of phosphine, attack by another hydrazido complex (e.g., A) to form a bridged species, C, is proposed. Hydrazido complexes such as A are known to be good nucleophiles. For example, they react in acid catalyzed reactions with aldehydes and ketones to form diazoalkane complexes (e.g.. Equations 4 and... 

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

As bis(hydrazido) complexes may be precursors in the generation of hydrazinediido compounds [25], the reaction sequence leading to the indoles was thought to be potentially part of a catalytic cycle for the direct generation of substituted indoles from alkynes and hydrazines. Based on the combined experimental and computational evidence presented in this work, we propose the mechanistic cycle depicted in Scheme 13.11 for the catalytic formation... 

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