Pyridazines metal complexes

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

There seems to have been no systematic study of tautomerism in the pyridopyridazines, but isolated observations in the pyrido[3,4-d]pyridazinedione (75BSF702, 69CPB2266) and pyrido[2,3-d]pyridazinedione (74JHC351) series have involved methylation studies. The pyrido[2,3-d]pyridazine-5,8-diones are believed to be enolized at the 8-position, from metal complexation results (67MI21500). 

Electrophilic attack of a metal complex on one of the nitrogen atoms of 1,2-diazines has been reported to occur in the mechanism of new metal mediated methods to prepare C-N bonds. Pyrrolo-fused pyridazines and phthalazines for instance were synthesized via attack of the 1,2-diazine on a palladacyclobutane intermediate 34 formed via oxidative addition of an alkylidenecyclopropane to Pd(PPh3)2 (Equation 7) <2004JOC3202>. 

Both pyridazine- and phthalazine-derived ligands show a very similar coordinating behavior to metal ions. It is has been observed that in most of their metal complexes the diazine (N-N) group bridges two metal in a //12 fashion (mode 1), but in some cases the diazine (N-N) behaves as a mono-dentate ligand (mode 2) (Figure 1). 

Molecular orbital studies on fluxional behavior of metal complexes containing monodentate diimines are of obvious relevance to one-end-off mechanisms for dissociation, as in the classic case of [Fe(bipy)3]. In this approach the behavior of the monodentate diimines is treated alongside that of such diaza-ligands as pyridazine (10), phthalazine (11), and naphthyridine (12)/ ... 

Several 3-substituted 6-methylmercuriothiopyridazines and complexes of perfluoro-pyridazine with metal carbonyl anions have been prepared <67MI21200). 

The Ni11 complex of bis(pyridazine)carboxamide can act as a bidentate ligands towards other metal ions, e.g., in (841). 7-2049 3,6-Bis(2-pyridyl)pyridazine (dppn, (842)) forms a tetranickel... 

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