Complexes of pyridazines

Complexes of pyridazine A(-oxides with cupric chloride were prepared, and depending on the particular N-oxide 2 1 or 1 1 complexes were formed (78TL1979). 

Spin-state control in cobalt(II) complexes of pyridazine- or triazole-containing ligands 03CCR(245)17. 

Pyridazine forms a stable adduct with iodine, with semiconductor properties. " Similar complexes were prepared from iodine mono-ehloride, bromine, and nickel(II) ethyl xanthate. Complexes of pyrida-zines with iron carbonyls and with iron carbonyls and triphenylphosphine have been prepared and investigated. " Complexes of pyridazines with boron trihalides, silver salts, mercury(I) salts, iridium salts, " ruthenium salts, and chromium carbonyls are re-... 

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

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). 

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... 

Thia-crown ethers incorporating propan-2-one units and dimeric silver(I) compounds as (176) and other polymeric species have been prepared.1132,1133 Other substituents can be diisopropyl idene groups which form complexes of the type [AgL(PPh3)]OTf (177),1134 pyridazine,1133 phthalazine1136 ligands or even organometallic compounds as ferrocene in (178).1137... 

With this in mind, the coordination chemistry of 52 with different diazine structural isomers was investigated. There were no detectable changes in the H NMR spectrum of 52 in a THF-Jg solution when either pyrazine or pyrimidine were added in 1 1 or 1 2 molar ratios, which suggested that only weak interactions might occur between 52 and these bases. In contrast, incremental addition of pyridazine or phthalazine to a THF-Jg solution of 52 at 25 °C resulted in an upheld shift of the aromatic NMR resonances of the diindacycle 52 thus reflecting the formation of complexes between 52 and the 1,2-diazines. Analysis of the tritration data clearly indicated the formation of 1 1 Lewis acid-diazine complexes 52-pyridazine-(THF)2 and 52-phthalazine-(THF)2 whose stability constants are equal to 80 ( 10) and 1000 ( 150) M respectively (Scheme 29). These data, as a whole, indicate that 52 is a selective receptor for 1,2-diazines. 

Pyridine and quinoline /V-oxides react with phosphorus oxychloride or sulfuryl chloride to form mixtures of the corresponding a- and y-chloropyridines. The reaction sequence involves first formation of a nucleophilic complex (e.g. 270), then attack of chloride ions on this, followed by rearomatization (see also Section 3.2.3.12.5) involving the loss of the /V-oxide oxygen. Treatment of pyridazine 1-oxides with phosphorus oxychloride also results in an a-chlorination with respect to the /V-oxide groups with simultaneous deoxygenation. If the a-position is blocked substitution occurs at the y-position. Thionyl chloride chlorinates the nucleus of certain pyridine carboxylic acids, e.g. picolinic acid — (271), probably by a similar mechanism. 

It was established that the Pd(II) complexes of bmpa were more reactive than those of dien, and the aqua-complexes were much more reactive than the chloro-complexes. The most reactive nucleophile of the five-membered rings is triazole, while pyridazine is the most reactive six-membered ring nucleophile. This could be understood in terms of nitrogen donor atoms in the 1,2-positions rather than in other configurations. As noted earlier, 260 for a given complex, the reactivity is related to the basicity of the... 

Methylmercury complexes of allopurinol (56) and l-methylpyrazolo[3,4-from aqueous solutions and characterized <87ICA181>. Copper complexes of allopurinol have also been prepared by reaction with copper salts and their structures were elucidated by x-ray crystal structural analysis <87ZN(B)195>. 

In this section we consider the osmium complexes of the three potentially bifunctional ligands pyrazine (pyz), pyrimidine (pym) and pyridazine (pyd) (Table 8). All form terminal complexes with... 

Spectroscopic and crystallographic techniques were used to good effect in the study of pyridazines. Spectrophotometry and H NMR spectroscopy were used to investigate the ligand substitution reactions of pyridazine in Pt(II) coordination complexes <07M1>. The electron densities and tautomeric equilibria of 6-(2-pyrrolyl)pyridazin-3-one 11 and 6-(2-pyrrolyl)pyridazin-3-thione 12 <07ARK114>. Optical, dielectric and x-ray diffraction studies of pyridazine perchlorate showed distinct structural differences between phases <07MI086219>. 

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