Triazenide complexes

Although the ability of triazenes to complex transition metal ions, notably copper, silver, and mercury, was recognized at a very early stage, and was 

Diaryl-, alkylaryl-, and, to a lesser degree, dialkyltriazenes are readily available. Consequently most triazenide complexes are synthesized from the free triazene or one of its salts. The salient methods, together with illustrative examples, are given below. 

From metal halides and free triazenes in the presence of base (77). 

From metal halides and lithium (720), sodium (42), or magnesium (77) triazenides. 

By oxidative addition of triazenes to low oxidation state metal complexes 135). 

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Electric fleld gradient, 22 214-218 Electroabsorption spectroscopy, 41 279 class II mixed-valence complexes, 41 289, 291, 294-297 [j(jl-pyz)]=+, 41 294, 296 Electrocatalytic reduction, nickel(n) macro-cyclic complexes, 44 119-121 Electrochemical interconversions, heteronuclear gold cluster compounds, 39 338-339 Electrochemical oxidation, of iron triazenide complexes, 30 21 Electrochemical properties fullerene adducts, 44 19-21, 33-34 nickeljll) macrocyclic complexes, 44 112-113... 

Pair-of-dimer effects, chromium, 43 287-289 Palladium alkoxides, 26 316 7t-allylic complexes of, 4 114-118 [9JaneS, complexes, 35 27-30 112-16]aneS4 complexes, 35 53-54 [l5]aneS, complexes, 35 59 (l8)aneS4 complexes, 35 66-68 associative ligand substitutions, 34 248 bimetallic tetrazadiene complexes, 30 57 binary carbide not reported, 11 209 bridging triazenide complex, structure, 30 10 carbonyl clusters, 30 133 carboxylates... 

Most triazenide complexes of the transition metals are air-stable, crystalline solids, soluble in many common nonpolar organic solvents. Most are deeply colored, ranging from bright yellow to deep red or brown. Dialkyl triazenide complexes tend to be rather less stable and those of titanium and zirconium are reported to be sensitive to air and moisture (77). 

Selected Bond Lengths" and Angles" for Triazenide Complexes... 

Studies of electronic spectra are confined almost exclusively to derivatives of silver(I) (236, 237) and mercury(II) (79, 194, 234), both of which have been investigated extensively. Data have also been recorded for copper(II) triazenide complexes (79, 236) and nickel(II) (84). 

Few triazenide complexes reported to date are paramagnetic. Examples studied by ESR are restricted to the low-spin osmium(III) complexes OsX2(PhNNNPh)(PPh3)2 (3), the binuclear mixed-valence rhodium salts [ Rh(/z-ArNNNAr)(CO)(PPh3) 2][PFe] (43), and the low-spin d cobalt(II) species Co(ArNNNAr)(C5H5)L (178). 

Electrochemical redox reactions have been reported for triazenide complexes of iron 214), cobalt 214), and rhodium 43). 

To date no triazenide complexes appear to have been reported for the scandium, yttrium, and lanthanum group of metals. 

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