Semiquinones metal complexes

The stability constant for the lumiflavin semiquinone Zn chelate in aqueous solution was found to be 2xlfr M , with the Cd chelate having about equal stability Aprotic solvents such as DMF serve to increase the stability constants relative to H2O about 10-fold. In all systems tested, the stoichiometry of the flavin semiquinone-metal complex is 1 1. 

Semiquinone, 3,5-di-/-butyl-chromium complexes, 398 Semiquinones metal complexes, 398 Sepulchrates classification, 920 metal ion complexes, 940 synthesis, 927 Serine... 

Transition metal complexes of o-benzoquinone, o-semiquinone and catecholate ligands. C. G. Pier-pontand R. M. Buchanan, Coord. Chem. Rev., 1981, 38, 45-87 (72). 

Broad-band irradiation from a xenon arc lamp by Felix and Sealy produced semiquinone radicals from catecholamines. They were detected by ESR spectra of their metal complexes. Semiquinones gave rise to o-quinones and... 

Metal Complexes Containing Catechol and Semiquinone ligands. 41 331... 

Due to some special structural and magnetic peculiarities, in particular, free-radical properties, the quinone ligands and their metal complexes are apart from the other kinds of coordination compounds [125a, 138a], as will be shown below. Here we present an overview of the main methods for the synthesis of complexes containing benzoquinone, semiquinone, and catecholate ligands, and peculiarities of the products. 

Transition metal complexes containing catecholate and semiquinone ligands have been reviewed by Pierpont and Buchanan.336 The syntheses of catecholate adducts of platinum group metals by oxidative addition of benzoquinone (BQ) have been reported (reaction 92).337 The coordinated catechol can then be oxidized to the semiquinone with silver ion (reaction 93). In reactions (92) and (93), L M = lr(Cl)(CO)(PPh3)2] and the benzoquinones (BQ) are shown in (146). The oxidative addition of phenanthrenequinone to [Ir(Cl)(CO)(PPh3)2] has also been cited.338... 

Pierpont, Conlandt G. and Lange, Christopher W., The Chemistry of Transition Metal Complexes Containing Catechol and Semiquinone Ligands. 

The electron-transfer reactions which form 212 when the corresponding heterocycle is oxidized by various metal complexes in perchloric acid have been studied by a stopped-flow technique and the results interpreted in terms of Marcus theory. The reaction forming the corresponding o-semiquinone was also studied. 

Metal Complexes Containing Catechol and Semiquinone Ligands. 

C.G. Pieipont and R.M. Buchanan, Transition metal complexes of < -benzoquinone, f -semiquinone, and... 

Nitric oxide fixation by non-transition metal complexes was reported by Ilyakina et al. [98]. Lead(II) and zinc(II) catecholato complexes readily react with nitric oxide to give the corresponding nitrosyl-containing mono-o-semiquinonates the process of binding and transfer of NO was monitored by EPR spectroscopy [98]. 

The mechanistic schemes proposed for metal complex catalyzed oxidations of 3,5-DTBC often involve the corresponding semiquinone as an intermediate [28,29,84,103,121,122]. 

The tris-bidentate ligand l,3,5-t is(5-ter butyl-3,4-djhydroxyphenyl)benzene was synthesized by Suzuki coupling in an excellent yield, v ch affords high-spin metal complexes containing a ferromagnetically coupled tris(semiquinone) ligand (Equation 5) [6]. 

---