4,4 -Dimethyl-2,2 -bipyridine complexes

The vinyl derivative 4-methyl-4 -vinyl-bpy is valuable for chemical electrode modification because its ruthenium and osmium complexes can be polymerized to generate electroactive films with variable properties.86 This unsymmetric ligand was prepared in 35% overall yield from 4,4 -dimethyl bipyridine by first lithiating one methyl group and quenching the anion with (chloromethyl)methyl ether, then reacting with potassium t-butoxide to effect elimination.87,88... 

Photophysical, electrochemical, and electrochromic properties of copper-/h.v(4,4 -dimethyl-6,6 -diphenyl-2,2 -bipyridine) complexes 02CCR(230)253. 

With 6,6 -dimethyl-2,2 -bipyridine (21-XLIX), many metal ions that form tris-2,2 -bipyridine complexes form only bis or mono complexes, or, in some cases, no isolable complexes at all, because of the steric hindrance between the methyl groups and other ligands attached to the ion. 

D-A reactions, comprising st-DNA and the Cn " complex of 4,4 -dimethyl bipyridine. Nitromethane and dimethyl malonate, both of which enolize readily, were employed as the nncleophiles. With 100 equivalents of dimethyl malonate, a clean and quantitative conversion into the Michael addnct was observed after 3 days, with an ee of 91%. The addition of nitromethane was slower nsing 1000 equivalents 97% conversion and an ee of 85% were obtained in the same time. The snbstrate scope proved to be broad a series of derivatives of the snbstrate were tested in the Michael reaction and generally gave high conversions (typically > 75%) and ees (86-99% with dimethylmalonate as the nncleophile, and 82-94% with nitromethane as the nncleophile). Only in the case of the Michael addition to the enone with R = Me instead of aryl, did the ee drop to 60%. Again, it was shown that the reaction conld be performed on a preparative scale (1 mmol), and that the catalyst solution conld be recycled withont loss of activity or enanti-oselectivity over at least two rnns. 

Re(bpy)(CO)3Cl-modified electrodes has not yet been explained. However, from the cyclic voltammograms of fac-Re(bpy)(CO)3Cl (Fig. 14) and from the intermediate complexes formed by electrolysis in acetonitrile in the presence and absence of C02, two different electrocatalytic pathways (Fig. 15) were suggested144 initial one-electron reduction of the catalyst at ca. -1.5 V versus SCE followed by the reduction of C02 to give CO and C03, and initial two-electron reduction of the catalyst at ca. -1.8 V to give CO with no C03. The electrochemistry of [Re(CO)3(dmbpy)Cl] (dmbpy = 4,4 -dimethyl-2,2 -bipyridine) was investigated145 to obtain mechanistic information on C02 reduction, and the catalytic reac-... 

In 1986, Breikss and Abruna reported electrochemical and mechanistic studies on a close analogue of the rhenium complex, (Dmbpy)Re[CO]3Cl, where Dmbpy = 4,4 dimethyl 2,2 bipyridine. The cyclic voltammogram of the complex at platinum in CH3CN/tetrabutylammonium perchlorate is shown in Figure 3.56 for simplicity we will consider only the electrochemistry taking place above c. —2.3V vs. SCE. 

The molecule [ReI(MQ+)(CO)3(dmb)]2+ has been a model system for studying intramolecular electron transfer over the last two decades. Here, MQ+ is the monodentate ligand Af-methyl-4,4/-bipyridinium, dmb is the bidentate ligand 4,4r-dimethyl-2,2r-bipyridine, and the three CO ligands are facially coordinated. Irradiation of this complex at room temperature in solution with near-UV light leads to a sequence of intramolecular electron-transfer events as shown in Fig. 7. 

The epoxidation of alkenes is one of the most impoi4ant oxidation methods. Electrochemical epoxidation of electron-poor olefins such as enoates (154 155) and enones has been accomplished by using silver(III)oxo bis(2,2 -bipyridine) and similar complexes (Scheme 61) [241], )-Dimethyl glutaconate is electrolyzed in an MeCN-LiCl04/Ag0Ac)(bpy)-(Pt) system to give the trans-epoxide in 90% yield. 

The complexes traTO-[ReO(OH)(N N)2] (N N = bipy or 4,4 -dimethyl-bipy) and trans-[Re02(N N)2]" (N N = 1,10-phenanthroline) are synthesized by reacting Rc207 with PPhs in the presence of the relevant ligands. Decomposition of the complexes occurs in aqueous media by slow oxidation of the coordinated bipyridine ligands to form the corresponding A-oxides." ... 

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