Crystal Structure of a Monoazide Bridged Dimer of Ni(vV-tetramethylcyclam)2+Sir:Recently we reported the preparations of 1 and some of its metal complexes.1 A surprising and disappointing property of these complexes was their lability, which was apparently a result of the set of nitrogen donor configurations that was dictated by the kinetic precesses (1) E.
The mechanisms of decomposition of two nickel(III) complexes which contain macrocyclic secondary amine ligands have been studied. When 2 is treated with basic solvents such as pyridine, triethylamine, or water a Ni(II) ligand radical species is formed according to:Chemical and spectroscopic evidence is presented in support of this species. A similar species is observed in the decomposition of 4 by pyridine but is not observed in water although product analyses suggest that a radical species is again formed. Depending upon the solvent 1-25% of the radicals formed decompose with rupture of the macrocyclic ring; the remainder are converted to Ni(II) tetramine complex by hydrogen abstraction from ligand fragments or from a second radical species. The latter process leads to monoimine complex formation. Under certain conditions monoimine may also be formed by oxidation of the Ni(II) ligand radical by Ni(III) complex. Such radical species have been proposed earlier as intermediates in macrocyclic amine complex reactions, but no direct evidence for their formation has previously been obtained.
Silver(II) complexes of four macrocyclic tetraaza ligands have been prepared by disproportionation of Ag(I) in the presence of the ligand. Some of these complexes may be oxidized to silver(III) species electrochemically or with NO* salts. Spectral and electrochemical properties of the new compounds are reported.
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