2,2 -bipyridine salts

Mo111 halide complexes formed with chelating diazadienes or diamines (N—N) include [MoCl3(CNMe)(N—N)] species with aromatic chelates such as 1,10-phenanthroline or 2,2 -bipyridine, salts containing the cation ds-[MoCl2(N—N)2]+ have been isolated.20 Compounds of stoichiometry [MoX3L4] are known for X = Cl, Br L = RCN and X = Br L2 = 2,6-lutidine,ls but it is not clear whether these involve seven-coordinate Mo111. 

The pale blue tris(2,2 -bipyridine)iron(3+) ion [18661-69-3] [Fe(bipy)2], can be obtained by oxidation of [Fe(bipy)2]. It cannot be prepared directiy from iron(III) salts. Addition of 2,2 -bipyridine to aqueous iron(III) chloride solutions precipitates the doubly hydroxy-bridged species [(bipy)2Fe(. t-OH)2Fe(bipy)2]Cl4 [74930-87-3]. [Fe(bipy)2] has an absorption maximum at 610 nm, an absorptivity of 330 (Mem), and a formation constant of 10. In mildly acidic to alkaline aqueous solutions the ion is reduced to the iron(II) complex. [Fe(bipy)2] is frequentiy used in studies of electron-transfer mechanisms. The triperchlorate salt [15388-50-8] is isolated most commonly. 

In analogy to the situation for bipyridine, the blue tris(l,10-phenanthroline)iron(3+) ion [1347949-7], [Fe(phen)2], must be obtained by oxidation of the corresponding iron(II) ion. [Fe(phen)2] has an absorption maximum at 590 nm, an absorptivity of 600 (Mem), and a formation constant of 10 . In solutions of pH > 4, this species is reduced to the iron(II) complex. The reduction is instantaneous in alkaline solution. At pH < 2, protons compete with iron(III) for the phenanthroline nitrogens and coordination is incomplete. [Fe(phen)2] is used most often in solution as an oxidant, but the trichloride [40273-22-1] and the triperchlorate monohydrate [20774-81-6] salts have been prepared. 

Quaternary Salts. Herbicides paraquat (20) and diquat (59) are the quaternary salts of 4,4 -bipyridine (19) and 2,2 -bipyridine with methyl chloride and 1,2-dibromoethane, respectively. Higher alkylpyridinium salts are used in the textile industry as dye ancillaries and spin bath additives. The higher alkylpyridinium salt, hexadecylpytidinium chloride [123-03-5] (67) (cetylpyridinium chloride) is a topical antiseptic. Amprolium (62), a quaternary salt of a-picohne (2), is a coccidiostat. Bisaryl salts of butylpyridinium bromide (or its lower 1-alkyl homologues) with aluminum chloride have been used as battery electrolytes (84), in aluminum electroplating baths (85), as Friedel-Crafts catalysts (86), and for the formylation of toluene by carbon monoxide (87) (see QuaternaryAA ONiUM compounds). 

We report here studies on a polymer fi1m which is formed by the thermal polymerization of a monomeric complex tris(5,5 -bis[(3-acrylvl-l-propoxy)carbonyll-2,2 -bipyridine)ruthenium(11) as its tosylate salt,I (4). Polymer films formed from I (poly-I) are insoluble in all solvents tested and possess extremely good chemical and electrochemical stability. Depending on the formal oxidation state of the ruthenium sites in poly-I the material can either act as a redox conductor or as an electronic (ohmic) conductor having a specific conductivity which is semiconductorlike in magnitude. 

Complexes having a tridentate A,A,C chelate derived from 2,9-diphenyl-phen,1944 4-(4-methoxy-phenyl)-6-phenyl-2,2 -bipyridine,1945 6-benzyl-2,2 -bipyridine,1946 or 6-But-2,2 -bipyridine1946 have been prepared from heating solutions of the ligand and [AuCl4] with the assistance of a silver salt. Equation (18) shows one example. 

Reaction of 3-(2-pyridyl)pyrazole and 6-(3-pyrazolyl)-2,2 -bipyridine with zinc salts results in mononuclear pseudo-octahedral complexes [ZnL3](PF6)2 and [ZnL2](PF6)2 respectively. The ligands coordinate as neutral mononucleating chelates in a similar fashion to the bidentate 2,2 -bipyridine or tridentate 2,2 6, 2"-terpyridine respectively.153... 

The aminophosphenium salt 204 undergoes a reaction with bipyridine 196 to yield iminophosphide complex 205 (Equation 21) <2000CC2087, 2005JA3921>. 

Caution should be observed in handling this compound, as with all perchlorate salts. The tris(bipyridine)chromium(I1) perchlorate explodes violently on slow heating to 250° and can be set off by static electricity. It does not appear to be shock-sensitive on dropping an 8.8-g. steel ball from 4 ft., although the compound was tested only once. The explosive properties of related complexes have been described.16... 

FIG. 38. a-D-GalNAc 2,2 -bipyridine oligomers self-assembled around a copper(II) salt.277... 

Replacement of both pyridine rings of bipyridine by imidazole has a much greater effect than replacement by thiazole and the [Fe N6]2+ derivative of 2,2 -biimidazole 34 (Dq(Ni2+)=1080 cm-1) is purely high spin [41]. The spin-crossover behaviour of tris(2,2/-bi-imidazoline)iron(II) salts seems somewhat unexpected in light of this and the relatively low a-donor power as indicated by the small Dq(Ni2+) value (1030 cm-1) for 36. 

The identification of different carbonate binding modes in copper(II) and in zinc(II)/2,2 -bipyridine or tris(2-aminoethyl)amine/(bi)carbonate systems, specifically the characterization by X-ray diffraction techniques of both r)1 and r 2 isomers of [Cu(phen)2(HC03)]+ in their respective perchlorate salts, supports theories of the mechanism of action of carbonic anhydrase which invoke intramolecular proton transfer and thus participation by r)1 and by r 2 bicarbonate (55,318). 

The viologens are mentioned a couple of times in this chapter, and are formally salts of 4,4 -bipyridine. The only book dedicated to them is The Viologens Physicochemical Properties, Synthesis and Applications of the Salts of 4,4 -Bipyridine by P. M. S. Monk, Wiley, Chichester, 1998, and is up-to-date and comprehensive. Although badly out of date, a shorter work is Electrochemistry of the viologens , C. L. Bird and A. T. Kuhn, Chem. Soc. Rev., 1981, 10, 49. 

The reaction of alcohols with CO can also be catalysed by palladium iodides, and various ligands or solvents. Acetic acid is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a palladium compound, an ionic iodide compound, a sulfone solvent at conditions similar to those of the rhodium system (180 °C, 60 bar), and, in some cases, traces of a nickel-bipyridine compound were added. Sulfones or phosphine oxides play a stabilising role in preventing metal precipitation [26], Palladium(II) salts catalyse the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective [27],... 

---