1,10-Phenanthroline chromium complexes

Recently, Lacour, Sauvage and coworkers were able to show that the association of chiral [CuL2] complexes (L=2-R-phen,6-R-bpy and2-iminopyridine) with TRISPHAT 8 leads to an NMR enantiodifferentiation, which allows the determination of the kinetics of racemization of the complexes (bpy=2,2 -bipyri-dine phen=l,10-phenanthroline) [119]. This type of application has recently been reported in conjunction with chiral sandwich-shaped trinuclear silver(l) complexes [122]. Several reports, independent from Lacour s group,have confirmed the efficiency of these chiral shift agents [123-127]. Finally, TRISPHAT can be used to determine the enantiomeric purity of (r] -arene)chromium complexes. These results broaden the field of application of 8 to chiral neutral, and not just cationic, species [114,128,129]. 

Garcia C, Ferraudi G, Lappin AG, Isaacs M (2012) Synthesis, spectral, electrochemical and flash photolysis studies of Fe(II), Ni(II) tetrapyridylporphyrins coordinated at the periphery with chromium(ni) phenanthroline complexes. Inorg Chim Acta 386 73-82... 

A chromium atom forms a neutral complex with carbon monoxide molecules and 1,10-phenanthroline molecules. The structure of the complex is ... 

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

Since complexes of 2,2 -bipyridyl and 1,10-phenanthroline with chromium in oxidation states I and 0 can be obtained by reduction (Scheme 64) of the chromium(n) complexes, these oxidation states will be considered together. Oxidation, as shown in Schemes 65 and 68 of Section 35.4.2.5, gives chromium(III) complexes, which are often best prepared in this way. Earlier work has been extensively reviewed, and few complexes of 2,2 6, 2"-terpyridyl are known.32 A chromium(I) phthalocyanine derivative is mentioned in Section 35.4.9.3. 

Chromium(II) complexes of bipyridyls, terpyridyl and the phenanthrolines have been discussed in Section 35.2.2.1. Complexes of the ligands 2-aminomethylpyridine (pic, 2-picolyl-amine) and 8-aminoquinoline (amq), which have one heterocyclic and one amino nitrogen donor atom, have been prepared by methods similar to those in Scheme 10. The bis(amine) complexes are typical high-spin, distorted octahedral complexes, and the mono(amine) complexes, from their antiferromagnetic behaviour and reflectance spectra, are six-coordinate, halide-bridged polymers (Table 15).103 No tris(amine) complexes could be prepared so the attempt to find spin isomeric systems in octahedral chromium(II) systems was unsuccessful ([Cr(en)3]X2 are high-spin and [Cr(bipy)3]X3 and [CrX2(bipy)2] low-spin). 

Mixed dinuclear complexes of tartrates and 2,2 -bipyridyl or 1,10-phenanthroline and chromium(III) have been prepared 934,935 the typical structure is illustrated below (213). Stereochemical correlations have been carried out by oxidatively cleaving the tartrate bridge (214,215).936 The crystal structure of sodium hydrogen bis(//-meso-tartrato)bis(2,2 -bipyridyl)dichromate(III) heptahydrate has been reported.937... 

Complexation of chromium(III) by nitrilotriacetic add (H2nta) has been investigated. Values of equilibrium constants (/ = 0, 25 °C) are log K = 10.66 and log K2 — 8.73.1234 A large number of mixed complexes with nta/chromium(III) have been prepared, including mixed aminoad-dates,1235 acetylacetonates, catecholates, oxalates and complexes with 1,10-phenanthroline and 2,2 -bipyridyl.1236 1238... 

CrLCls DMF have normal magnetic moments (103) and are jirobably monomeric. The purple diol complex [(phen)2Cr(OH)2Cr(phen)2] as the iodide has been the subject of a magnetochemical investigation (221). The same cationic specie as the nitrate may be hydrolyzed to the orange cis-diaquobis(phenanthroline) chromium(III) ion (393). The tris-chelate... 

Metals in Molecular Biology—Synthesis, Photophysical and Chiral Properties of Tris(1,10-Phenanthroline)Chromium(lll) Metal Complex DNA Interactions and Reactivity... 

The traditional preparation of chromium(III) complexes involves reacting the brilliant blue ion with phenanthroline ligand. In this experiment we will prepare [Cr(phen)3]3+, Figure 8.1, using a revised method in which the precipitation of AgCI(s) drives the complex formation and eliminates the need for inert atmosphere conditions. 

The rate behaviour for the reduction of salicylato and several substituted salicylato derivatives of [(NH3)5Co] was consistent with the intervention of chelated precursor complexes formed from the two cobalt(iii) centres with loss of H, after which internal electron-transfer competes with non-productive dissociation of the precursor. The kinetics of reduction by chromium(ii) of a series of 2-hydroxy-benzenato derivatives of [(NH3)5Co] were compared with those of the 2-amino-benzoate derivatives. A study of the kinetics of dissociation of oxalatobis(phenan-throline)cobalt(iii) into cis-d iaquobis(phenanthroline)cobalt(iii) in aqueous HCl-KCl media found the rate was first order with respect to The photo-redox... 

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