Iron, complexes with pyridazines

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). 

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-... 

The (benzo)pyridazines are able to form complexes with a variety of metal ions, and examples of complexes with iron (Section 6.01.3.2.1) and with silver and ruthenium (Section 6.01.12.6) are given. 

Biomimetic Cu(II) and Fe(II) complexes with bis- and tris-pyridyl amino and imino thioether ligands and vacant (or potentially so) coordination positions (Fig. y are active as catalyst precursors for the solvent- and halogen-free MW-assisted oxidation of 1-phenylethanol by TBHP, in the presence of pyridazine or other N-based additives. Maximum TOF of 5220 h (corresponding to 87% yield) was achieved just after 5 min of reaction time under the low power MW irradiation. The same authors reported" the catalytic activity of related copper, iron, and vanadium systems with mixed-N,S pyridine thioether hgands. The Cu and Fe complexes proved to be useful catalysts in various MW-assisted alcohol oxidations with TBHP, at 80 °C. Thus, 5-containing ligands can also be used to create effective catalyst precursors. 

The activity of the iron(II) complexes (6, 9-11) is lower, the overall yields not exceeding 21% (Table 18.2, runs 23, 26-28) [14]. However, the combination of 6-11 with a catalyst promoter, such as, pyrazine-2-carboxylic acid (Hpca), pyridine (py), or pyridazine (pydz), leads to a significant increase of the acetophenone yield, for example, for the systems 6/9/10-Hpca, 7/8-py, 7/8-pydz, yields of circa 92-75% were achieved in 30 min (Table 18.1) [14]. Moreover, for 9-Hpca, the yield of circa 74% was achieved in 5 min with corresponding turnover frequency (TOF) value of 4440 (Table 18.1, run 9) [14b]. For the systems in Table 18.1, the yields obtained in MW-assisted processes are also superior to those obtained under CH, that is, for the 6-Hpca system, an acetophenone yield of circa 26 % was achieved in 30 min, while utilization of MW irradiation allowed to obtain a yield of 76% (Table 18.1, run 2 vs 1). 

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