Heteroaromatics metallated azoles

One such problem is the possibility of the existence and aromatic character of analogues of five-membered heteroaromatics with one heteroatom and those of azoles in which one or several ring C atoms are substituted by a metal atom, e.g. structures (289)-(305) (M = Ge, Sn, Pb X = O, S, NR). The other specific problems involve antiaromaticity of 871-electron carbenoids (306) and homoaromaticity of 67t-electron systems with a tetravalent metal (307). 

Complexes of the heteroaromatic compounds may be prepared by building up the heterocyclic ligand. The most effective method for the N (10, E = N) and C (11) derivatives is 1,3-dipolar cycloaddition from the metal azides. The N and C derivatives of triazole (67) and (68), tetrazole (69-72) and other azoles, e.g., 73, were prepared.The transformations leading to the complexes are summarized later. 

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