Tetrazoles transition metal complexes

Despite the weak basicity of isoxazoles, complexes of the parent methyl and phenyl derivatives with numerous metal ions such as copper, zinc, cobalt, etc. have been described (79AHC(25) 147). Many transition metal cations form complexes with Imidazoles the coordination number is four to six (70AHC(12)103). The chemistry of pyrazole complexes has been especially well studied and coordination compounds are known with thlazoles and 1,2,4-triazoles. Tetrazole anions also form good ligands for heavy metals (77AHC(21)323). 

Reactions between 5-cyanotetrazole and transition metals, when performed in boiling acetone, lead to hydrolysis of the cyano group and formation of 5-carbamyl tetrazolate complexes (68). Complexes containing 1- or 5-substituted tetrazolate anions can also be obtained by 1,3-dipolar cycloaddition of organic isonitriles (RNC) (15) or nitriles (RCN) (61), respectively, to coordinated azide ligands [Eqs. (3) and (4)]. 

Infrared spectra have been recorded for the parent tetrazole (ttaH), its sodium salt, and a range of transition metal derivatives (94). In subsequent work the infrared spectra of sodium tetrazolate and of the copper complex Cu(tta)2 H20 were assigned and a vibrational analysis was reported for the tetrazolate anion (77). Infrared data have been... 

Other polymeric heterocyclic amines such as imidazole, benzimidazole pyrazole, triazole or tetrazole are also excellent ligands for transition metal ions [1,2,23,24]. A detailed study on the complexation of Ag(I) and Cu(II) with poly(A-vinylimidazole) gave insights into the intrinsic complexation equilibria [88]. 

We are investigating the template formation of 2-D and 3-D metal-di-cyanamide anionic networks, for instance of type Mn(dca)3, by use of [M(N,N)3]n+ cations such as [M(2,2 -bipy)3]2+. A hexagonal sheet network was formed in [Fen(2,2 -bipy)3][Fen(dca)3]2 in which the cations fitted beautifully within the hexagonal windows. The cation remained LS between 4-300 K [66], Attempts to make the Con(2,2 -bipy)32+ analogue unfortunately led to dissociation of dca and bipy and formation of a zig-zag chain structure in the weakly-coupled HS complex [Con(dca)2(2,2 -bipy)2]n. The complex [Fen(propyl-tetrazole)6]2+, which has a very sharp SCO transition [42], unfortunately did not yield a network product. 

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