Organometallic chemistry additional approaches

Comparison of the development of the organometallic chemistry of the two elements reveals furthermore that the chemistry of technetium is often a copy of that of rhenium. Type reactions, starting materials and compounds have been first synthesized, almost without exception, with rhenium. Some of the rare exceptions where the chemistry of rhenium followed that of technetium will be discussed. In addition the scarcity of 2 was the basis for a very different approach to low-valency organotechnetium chemistry, and resulted finally in the fact that almost all compounds originally derived from 2 can be synthesized from 3 in better yield. 

Organometallic chemistry may provide another approach to cyclization of JV-allylanilines. The procedures developed to date require additional functionalization, specifically a halogen on the aromatic ring. Treatment of JV-allyl-Af-methyl-o-bromoaniline first with methylmag-... 

This contribution will focus on new developments in the key step for the synthesis of PAHs the C-C bond formation as one of the most fundamental and challenging processes in organic and organometallic chemistry. In addition, these new synthetic approaches often give access to substituted aromatic structures. The authors attempt to cover the literature until the end of 1996. Important contributions in the synthesis of PAHs during the work on this review in the beginning of 1997 will also be considered whenever possible. The functionalization of aromatic compounds [10] and the chemistry of fullerenes [18] are beyond the limits of this contribution. As mentioned above, this review will concentrate on modern routes to preferably large condensed PAHs. Classical approaches towards aromatic hydrocarbons like the Pschorr, Elbs, Hayworth,... 

Steric stabilization of otherwise reactive species is a standard strategy in organometallic chemistry. Steric bulk can permit formation of low electron count, low coordination number complexes, as in the isolable 14e bis-Tv-allyl complex 2.16. In this case, the bulky SiMej groups enforce a syn,anti conformation that minimizes the steric clash between SiMes groups but blocks approach of additional ligands. The 12e paramagnetic. 

---