1,2-Dioxolene complexes

Garcia-Canadas, J.Meacham, A. P.Peter, L. M.Ward, M. D. Electrochromic switching in the visible and near IR with a Ru-dioxolene complex adsorbed on to a nanocrystalline Sn02 electrode. Electrochem. Commun. 2003, 5, 416 120. 

It is commonly accepted that the C-O distance of the quinoidal ligand is an important parameter suggestive of the charge of the ligand in metal-dioxolene complexes, namely ... 

We finally point out that heteroleptic-dioxolene complexes with different redox non-innocent ligands can exhibit even further difficulty assignable redox changes.60... 

A series of novel ruthenium(IV) dioxolene complexes, formally [3 + 2] cycloadducts, have been obtained via the reaction of cix-[Ru (0)2(Me3tacn)(CF3C02)] with trimethylsilylacetylenes (Scheme 14). " These dark blue complexes display a characteristic UV-vis absorption band at 550-680 nm. They are also characterized by electrospray mass spectrometry. The X-ray structure of the complex formed with bis(trimethylsilyl)acetylene has been determined the two Ru—O bonds of the metallocycle are of the same length (1.978 A). 

A series of catecholate derivatives 189 and 190 were prepared from the parent dichloro complexes by reaction with o-catechol or tetrachloro-o-catechol and Me3N in hot methanol.83 The corresponding reaction with an unsymmetrical catechol, 3,5-di-ferf-butylcatechol produced a mixture of isomers 191a and 191b. The related dioxolene complexes 192 and the amidophenolate complexes 193 were also prepared by the same method. An X-ray crystal structure on the latter complex shows that the phenolate oxygen is trans to the aryl carbon atom. 

The redox noninnocence of Os and Ru dioxolene complexes and of their nitrogen donor analogues has... 

Synthesis and molecular structure of two bis(zinc-dioxolene) complexes have been also described.186 The [ Zn(TpCum,Me) 2(L-H2)] derivative in Fig. 3.39 has two protonated catecholate ligands, whereas [ Zn(TpCum,Me) 2(L-H)] has one protonated catecholate and one semiquinone ligand. 

Beni A, Dei A, Rizzitano M, Sorace L (2007) Unprecedented optically induced long-lived intramolecular electron transfer in cobalt-dioxolene complexes. Chem Common 2160... 

Scheme 3. Valence tautomeric bistability of cobalt bis(dioxolene) complex (Pierpont, 2001 Yoshida et al., 2009).

Such a complex is constituted not only by the redox-active V(IV) centre, but also by the redox-active catecholate ligand. In fact, as we will see in more detail in Chapter 6, Section 3, o-dioxolene ligands can undergo the redox processes illustrated in Scheme 4. 

Transition metal complexes with o-dioxolene ligands constitute one of the most intriguing classes of complexes as far as their electrochemical behaviour is concerned, in that, as already mentioned in Chapter 5, Section 1, such ligands are able to shuttle through the oxidation states o-benzoquinone)o-benzosemiquinone/catecholate illustrated in Scheme 250 (a process carried out in nature by the dicopper (I I)-based enzyme catechol oxidase through a single two-electron step see Chapter 9, Section 1.2). 

Indeed a limited number of monomeric [Mn(dioxolene)2] complexes have been structurally characterized (M = Ni dioxolene = 3, 6-di-terf-butyl-l,2-benzosemiquinone, n = 0 51a dioxolene = A AT -bis, 3-dihydroxybenzoyl)-l,7-diazaheptane, n = 2 51b dioxolene = 1,2-cate-cholate, n = 2 51c M = Pd, Pt dioxolene = 3,5-di-terf-butyl- 1,2-benzo-semiquinone, n = 052), likely due to the fact that Ni(II) in the presence of... 

As in the case of o-dioxolenes, the diimine derivatives also form tris-complexes. Figure 38 for instance shows the molecular structure of the benzoquinone diimino dication [Osn(bqdi)3]2 +. 50c... 

Other mixed-valence metal complexes have been published that display electrochromic behavior, among them bipyridyl ruthenium complexes linked through dioxolene containing bridging ligands, such as 3,3, 4,4 -tetrahydroxybi-phenyl, 3,3",4,4"-tetrahydroxy-p-terphenyl, and 9-phenyl-2,3,7-trihydoxy-6-flu-orone [115,116] (Chart 3). Many of the redox processes that lead to frequently... 

Organometallic substitution of iron-complexed dioxolenes has been reported. The reaction proceeds with net inversion of configuration, the result of a two-step addition-elimination pathway. Dialkyl-cuprates, higher order cyanocuprates and Grignard reagents have all been employed, and sequential dis-... 

Structural (X-ray) properties of homoleptic, mononuclear transition metal complexes of 1,2-dioxolenes 06CCR(250)2000. 

Transition metal complexes with dioxolene ligands may also give rise to interesting magnetooptical properties. Dei et al reported that in [Cr(TMC)SQ], where TMC= 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, the forbidden transition which is responsible for the... 

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