Fixation with Low-Valent Ti and Zr Metallocenes

The various titanium mixed systems have been used not only to reduce dinitrogen to ammonia, but also to hydrazine (55) and to organonitrogen compounds. Thus, mixtures of TiCL, sodium, and naphthalene were found to give traces of naphthylamines (55). Reaction of (17-C5H5)2Ti(CsH5)2 with phenyllithium in the presence of N2 gave small amounts of aniline (55). Reaction of (rj-CjHs TiCU with Mg, N2, and diethyl ketone afforded a mixture of 3-pentylamine and di(3-pentyl)amine in 25-50% yield based on fixed N2 (56). 

The first transition metal dinitrogen complex, [Ru(NH3)5N2]2+, was prepared by Allen and Senoff in 1965 (62). By 1970, some 20 dinitrogen 

Teuben and de Liefde Meijer (64) prepared the first well-characterized titanium dinitrogen complex. They found that toluene solutions of phenyl-dicyclopentadienyltitanium(III) (26) when cooled under N2 gave an intense blue coloration ascribed to the reversible formation of a dinitrogen adduct. 

Complex 28 consists of two (i7-C5H5)2Ti(p-CH3C6H4) units bridged by a dinitrogen ligand, in an essentially linear Ti—N=N—Ti arrangement. 

Further work is needed to actually isolate and characterize some of these proposed intermediates in the reduction of dinitrogen. 

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