Bipyridyl, 2,2-dipyridyl

Bipyridines (1UPAC), also known as bipyridyls, dipyridyls, and dipyridines, are aromatic nitrogen heterocycles that form complexes with most transition metals.1-5 This class of compounds contains six possible regioisomers—2,2 (1), 2,3 (2), 2,4 (3), 3,3 (4), 3,4 (5), and 4,4 (6)—most common of which is the bidentate chelate, (1), (bpy = 2,2 -bipyridine). Bipyridine ligands interact... 

Cul, 12mol% of 2,2 -dipyridyl, in lOvol of xylene diglyme (9 1) at 140°C with azeotropic removal of the water as it was formed. The azeotropic removal of water helped alleviate the problem of solids coating the reaction vessel walls, which led to stalling of the reaction. The reaction was complete in less than lOh, typically with 96% assay yield and 92% isolated yield for 49 after aqueous work-up and subsequent crystallization [14b-d]. It was noteworthy that this catalytic system composed of the copper(I) salt with bipyridyl ligand was recently reported to be applicable to a wide range of Ullmann-type ether formations [14d]. 

The classical route for producing 2,2 -dipyridyl consists in the dehydrodimerization of pyridine on Raney-Ni using a process developed by the Imperial Chemical Industries [63AHC(2)179 68CI(L)49, 80MI4]. 2,2 -Bipyridyl reacts with ethylene bromide to give l,l -ethylene-2,2 -bipyridylium bromide (diquat). The production of one ton of the diquat (which is widely used as a herbicide) requires 1.2 tons of pyridine [Eq.(17)]. 

N,N -Disubstituted Bipyridyls and Dipyridyl Ethenes 2.1 Variation of N-Substituents in 4,4 -Bipyridyl... 

The production of bipyridyls (1) and bipiperidyls (2) was observed on reduction of pyridine. Schering AG has a patent on a process for producing 4,4 -dipyridyls at the cathode of a divided or undivided cell using liquid ammonia as the solvent.26 The same bipyridyl was also formed during electrolysis of bromobenzene in pyridine solvent, using Mg electrodes.27 Bipiperidyls (2) were observed as products of pyridine reduction as early as... 

Pseudotetrahedral complexes of Cu1, [Cu(bpy)2]BF4 and similar derivatives with substituted dipyridyl ligands all gave intact cations in their ES mass spectra [37,38]. In an extension of this chemistry, bipyridyl groups were introduced into amino acid residues and, after reaction with Cu1, the intact cations of the copper(I) complexes of these species were observed [37]. The analogous [Cu(phen)2]+ ion and others derived from substituted phenanthrolines have also been observed [39]. For both the [Cu(bpy)2]+ and [Cu(phen)2] + species, collisional activation led to loss of one ligand. 

The reaction of [MoO(H20)(CN)4] with 1,10-phenanthroline (211) and 2,2 -dipyridyl (215) has also been studied by means of reaction kinetics. It is clear that there are still uncertainties and questions regarding the mechanism of the reaction of these bidentate ligands For example, why is the reaction of the molybdenum complex faster at high pH values at which there is less of the aqua and more of the hydroxo) complex in solution (211) Scheme 5 was proposed for reaction with 2,2 -bipyridyl (215). 

The procedure described here Is by far the most efficient synthesis of terpyridine. Previous preparations include the dehydrogenation of pyridine with ferric chloride, the Ullman reaction of 2-bromopyridine and 2,6-dibromopyridine, the action of copper on 2-bromopyridine and 6-bromo-2,2 -dipyridyl, the reaction of iodine or ferric chloride with 2,2 -bipyridyl and the reaction of 2,2 -bipyridyl with 2-1ithiopyr1d1ne (40% yield). Terpyridine is a very effective chelating agent. 

Nornicotine Formylanatabine (FAT) 4-(Methylnitrosamino)- 2,3 -Dipyridyl l-(3-pyridyl-)-l- ( bipyridyl ) butanone (NNK)... 

Polymerizations of styrene using 2,2 -dipyridyl as the ligand indicated that they proceed first order with respect to the concentration of initiator, and 0.4 and 0.6 orders with respect to the concentration of Cu(l) halide and ligand [218, 229]. The copper bipyridyl complexes mentioned above were pictured by Haddleton et al. [233, 234] as follows ... 

The so-called articulated PBO and PBT, in which 3,3 -biphenyl or 4,4 -(2,2 -bipyridyl) moieties have been incorporated into the otherwise rodlike backbone, are appreciably more stable than those containing diphenoxybenzene (Ph-O-Ph) segments (Fig. 54.2). While PBO and PBT articulated with diphenoxybenzene units experience significant weight losses at 316 °C, those articulated with biphenyl and bipyridyl units are largely unaffected at that temperature and display thermo-oxidative stability comparable to the parent PBO and PBT polymers. While the biphenyl unit appears to give better stability than the dipyridyl unit, the stability of the articulated PBO and PBT polymers decreases with increased content of the flexible unit in the backbone [14]. 

Irradiation of the complex (1) leads to a detectable nonradiative decay process which is interpreted as shown in Scheme 1 where S2 = C6H5SCH2CH2SC6H5 B = 2,2 -dipyridyl L = 4,4 -bipyridyl and related ligands. The slow step is electron transfer from the bridging to a nonbridging... 

The two ligands that have been most extensively studied are ortho-phenanth-roline and 2,2 -bipyridyl. Both of these ligands are bidentate and are only weakly basic. With ortho-phenanthroline the maximum number of bound ligands is four when the anion is the perchlorate ion (Krishnamurthy and Soundararajan, 1966). The tris-complex with one coordinated perchlorate ion (as indicated by the infrared spectrum) has also been obtained (Grandey and Moeller, 1970). There do not appear to have been any dipyridyl complexes with the lanthanide perchlorates prepared at the present time, although there does not seem to be any reason they would not form. 

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