1.2.4- Triazole, metal complexes

There are a number of other reported 1,4-disubstituted-l,2,3-triazole metal complexes in which monodentate binding is presumed [114—119]. None of these compounds have been structurally characterized, and as such, it is unknown whether the coordination is through the N2 or N3 nitrogen of the 1,2,3-triazole unit. However, on the basis of the previously discussed structurally characterized... 

Cycloaddition reactions catalysed by transition metal complexes are an important tool in the construction of a wide range of carbo- and hetero-cyclic systems, such as benzene, pyridines, triazoles, etc. [7]. In general, these reactions are extremely atom-efficient and involve the formation of several C-C bonds in a single step. Among the innumerable possible catalytic systems for the cycloaddition reaction the NHC-metal complexes have received special attention [7c]. 

Adducts of triazoles with transition metal salts are usually prepared by direct reactions between the two components involved and frequently precipitate or crystallize spontaneously from the reaction mixture (55,172,194, 202). Complexes containing triazolate anions can usually be obtained from the corresponding transition metal halide, carboxylate, nitrate, or perchlorate complex and an alkali metal (146, 147, 172) or thallium(I) triazolate salt (33). Other routes to triazolate complexes include the direct reactions of metal halides with triazoles in the presence of a base (201) and the treatment of triazole/metal halide... 

Infrared data have been tabulated for benzotriazole and a wide range of its transition metal complexes or adducts (172). Far infrared spectra have been recorded for copper(II) benzotriazole adducts and bands at 270-320 cm-1 have been assigned to Cu-N vibrations (172). Infrared absorptions at approximately 825, 800, and 775 cm-1 in the spectra of cobalt(III)/4,5-disubstituted triazolate complexes have been attributed to triazolate ring vibrations (109). Infrared data have been reported and assignments made for palladium and platinum thiatriazoline-5-thionate complexes (37) and for the parent thione (127). Vibrational spectroscopy has been employed in an attempt to determine coordination sites for a range of 8-azapurine complexes (108). 

One of the most important biomolecules for which fluorescent sensing [94-96] is of great importance is nitric oxide [97-101]. Nitric oxide can react with several organic dyes, switching on their fluorescence as a result of a triazole ring closure reaction [94], There are also useful and selective NO optical sensors based on transition metal complexes (Figures 16.22 and 16.23) [94-96],... 

Although the parent compound 1,2,3-triazole has not been studied, the crystal structure of benzotriazole (18) has been determined (74AX(B)1490). Benzotriazole crystallizes in the space group P2i. In association with its remarkable anticorrosion activity (Section 4.11.6.4.2) benzotriazole and its conjugate base form stable transition metal complexes whose crystal structures have, in part, been studied. Some examples are presented in Figures 5-7, with special regard to the molecular dimensions of the benzotriazole moiety. 

Deactivation against electrophilic attack accounts for the difficulty or failure of nitration, sulfonation and iV-oxidation of 1,2,4-triazoles proper. However, triazolate anions react readily with electrophilic reagents alkylation and acylation have received much attention but halogenation and addition reactions less. Systematic study of the formation and reactions of salts and metallic complexes is of recent origin. 

The crystallography of 8-azaadenine complexed with zinc and mer-cury and of 8-azahypoxanthine with cadmium and mercury showed that the first two metals complexed with N-3 whereas the cadmium was bound to N-7. Cupric ions opened the nucleus of 8-azaadenine to give a triazole. ... 

In 1988 Lalor reported the synthesis and spectroscopic characterization of some new poly(benzo-triazolyl)borate salts (Scheme 8).180 The regiospecifity of the synthesis of I I B( Btz)4 differs from that of pyrazole/BH4 reaction in that B—N bond formation takes place in a manner that maximizes steric crowding at boron (i.e., at the triazole N(l) atoms). In 1989 Shiu describes some new metal carbonyls of HB(Btz)3.181 The synthesis and spectroscopic characterization of some first-row transition metal complexes was reported by Cecchi,182 whereas Hill described some new Rh183 and Ru184 carbonyl and isonitrile complexes. The formation of isonitrile derivatives was proposed to proceed through an associative mechanism involving an intermediate complex... 

The synthesis of low-dimensional solids has become more important than ever before, both to chemists and physicists. In the catenation of metal ions, the catenating blocks are usually polynucleating ligands. The 1,2,4-triazole ligand acts in most of its metal complexes as a 1,2-bicoordinating ligand. In this type of coordination, linear polynuclear complexes are formed. 

Tin Derivatives. 5-Stannylated or 5-zincated 1-benzyloxy-l,2,3-triazole, 114 and 115, respectively, is available from the 5-lithiated species by quenching with the respective metal halide (Scheme 49). Either metal complex is a good substrate for ketone formation 116 in the 5-position with acid chloride reagents. ... 

Scheme 2 Popular metal complexation motifs used for supramolecular polymer-network formation. py pyridine, bpy bipyridine, tpy terpyridine, BTP 2,6-bis(l,2,3-triazol-4-yl)pyridine, BIP 2,6-bis(l-methylbenzimidazolyl)pyridine, DOPA dihydroxy-phenylalanine, PAA poly (acrylic acid)...

Yamaguchi I, Nagano T. Synthesis, chemical, and thermoelectric properties of n-type jr-conjugated polymer composed of 1,2,4-triazole and pyridine rings and its metal complexes. J Appl Polym Sci 2013. 

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