2- quinoxaline metal complexes

A number of quinoxalines carrying substituents in the benzene ring base have been quaternized, including 5-ethoxy,6-methyl, 6-chloro, and some 2-phenyl derivatives, but in none of these cases has the position of quatemization been ascertained. 5-Hydroxy-quinoxaline gives a methiodide which can still form metal complexes, indicating that salt formation occurred on N-1. ... 

Note Only a few simple examples of the metal complexes formed by quinoxaline oxides and dioxides are given here. 

Note Many of the (substituted hydrazino)quinoxalines covered in this section have been converted into metal complexes, randomly exemplified here. 2-(Pyridin-2-ylhydrazonomethyl)quinoxaline (246) Fe(ll), Ni(ll), and Cu(ll)... 

Quinoxaline-2,3-dithione, as reported earlier,1 is useful for its coordinating properties with transition metals. The metal complexes of the dithione with Cu, Ni, Zn, Pd, and Pt have been prepared,171 and the spectral properties of the Ni and Pd complexes examined.171,172 UV data indicate that quinoxaline-2,3-dithione (153) is present as such, rather than as 2,3-dimercaptoquinoxaline the highly colored nature of its complexes is attributed to charge transfer.171... 

Flavoquinone-metal complexes of Ag, Cu, Ni , Co , and Fe have been detected in aprotic solvents using n.m.r. and optical absorption spectroscopy. The stoicheiometry and formation constants were determined by metal ion titration in acetone. l,4-Di-N-butoxy-6//-indole[2,3-h]quinoxaline in CHCI3 extracts Ag from HNO3 solution, with formation of complex (61) indicated from i.r. spectra. On the other hand, the 2,3-dibutoxy-isomer shows no ability to extract. 

Quinoline-5-sulfonic acid, 8-hydroxy-7-iodo-metal complexes absorptiometry, 549 Quinolinium salts in gravimetry, 535 Quinoxaline-2,3-dithiol metal complexes liquid-liquid extraction, 547... 

Progress in quinoxaline synthesis (Parts 1 and 2) 12PHC(24)55. Pyrazinecarboxylic acid and analogs Highly efficient co-catalysts in the metal-complex-catalyzed oxidation of organic compounds 13CCR 732. 

It has been reportedthat a C-C bond in an aromatic ring is cleaved with a stoichiometric amount of a transition metal complex. When quinoxaline was treated with the tungsten complex 90, dihydrogen was released and the tungsten was inserted into the C-C bond to furnish the di(isocyanide) tungsten complex 92 (Scheme 7.37) [52]. The authors proposed the mechanism to be through sequential C-H... 

One of the methods of preparing metal quinoxalinoporphinazines involves the thermolysis of quinoxaline 65a with dry manganese and chromium chlorides at 220 °C, which leads to 129 (R = R = R = R = H, X = Mn, CrCl) in 80-84% yields (1997RUP2074188,1996RUP2052464). Similarly, heating quinoxaline 65j with the acetates of zinc, cobalt, or copper at 220° C without any solvent, but in the presence of ammonium molybdate as a catalyst resulted in corresponding metal complexes of the macrocycles 129 (R = R = R = H, R = f-Bu, X = Zn, Co, Cu) in 57-74% yields (2008ZOB1214). 

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