Dinitrogen, rhenium complex

Sutton has reported a pentamethylcyclopentadienyl rhenium dinitrogen complex that activates benzene (Eq. 29) [114]. The intermediate involved is similar to that described above in studies by Bergman [92]. In the absence of a reactive solvent, cyclometallation was observed. 

Titanium(IV) chloride forms a number of different adducts with trans-[ReCl(N2)(PMe2Ph)4] (see Table 1) that are believed to involve dinitrogen bridging between rhenium and titanium. Hydrolysis or treatment of these adducts with ethanol results in the virtual quantitative recovery of the original rhenium-dinitrogen complex. 

Acids, acyl, and aroyl halides all react with [ReCl(N2)(PMe2Ph)4]. However, protonation occurs at the metal to give the hydride [ReClH(N2)-(PMe2Ph)4], whereas slow acylation and aroylation occur at the end nitrogen atom. Interestingly, this latter reaction is the reverse of the preparation of the rhenium dinitrogen complexes. Alkyl halides do not react with rhenium complexes of dinitrogen. 

Nitrosylrhenium complexes with the ehelating ligand dppe have been obtained by the reaetion of [ReOBr3(dppe)] with or by treatment of the rhenium(I) dinitrogen complex... 

Organohydrazine derivatives play an important role in the coordination chemistry of rhenium since they represent important intermediates in the preparation of nitrido, imido, or dinitrogen complexes as has been described in the previous sections. They are defined as complexes which possess metal-nitrogen-nitrogen bonds, which would (strictly applied) also include dinitrogen complexes, and indeed this class has attracted considerable attention in the exploration of biological nitrogen fixation. 

A RHENIUM(I) DINITROGEN COMPLEX CONTAINING A TERTIARY PHOSPHINE... 

Dinitrogen complexes of rhenium are relatively stable to air and moisture under ambient conditions so that they serve as convenient starting materials for a number of Re(I), Re(II), and Refill) complexes. The basis of their reactivity is the lability of the N2 ligand in either the Re(I) or Re(II) oxidation states. 

A rhenium(l) dinitrogen complex containing a tertiary phosphine 263... 

An alternative route to the mononuclear dinitrogen complex is by the reaction of [(ij5-CsH5)Mn(CO)2(N2Ari r and its rhenium homologs with nucleophiles such as Cl, Br, I, Cn, and SCN. This has poten-... 

Scheme 1 Routes to some dinitrogen complexes of rhenium(I)...

Table 3 Some Properties of Representative Dinitrogen Complexes of Rhenium(I)...

Scheme 2 Some reactions of dinitrogen complexes of rhenium(l)...

Rhenium dinitrogen phosphine and phosphite complexes give products through intramolecular C-H activation upon ultraviolet (UV) irradiation in hydrocarbon solvents. For example, the agostic complex 88 identified by IR spectroscopy decays to stereoisomeric cyclometallated products [Eq. (6.68)]. Analogous transformations were observed for phenoxy and phenyl derivatives. 

Disappointingly, the rhenium complex also was not capable of producing ammonia. Most generally, protonation of dinitrogen complexes led to evolution of the dinitrogen as the gas, often with the production of metal hydrides, a not unexpected result in view of the electron-richness of the metal sites to which dinitrogen was bound. That we were eventually successful was due to a combination of factors, all important in research, as seasoned practitioners will know. These were persistence, preparedness and serendipity. 

The range of metals was also extended to include rhenium in the preparation of [ReCl2(N2COR)(PMe2Ph)3] from [ReCl(N2)(PMe2Ph)J,3 but other dinitrogen complexes proved resistant. 

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