Bpy, 2,2 -Bipyridine

Ligands containing more than one donor atom which can bond to a metal centre are termed polydentate or multidentate. Such ligands are extremely important and have played crucial roles in the development of coordination chemistry. Well known examples include 1,2-diaminoethane (ethylenediamine, en) 2,4-pentanedionate (acetylacetonate, acac ) 2,2 -bipyridine bpy) and 1,2-diaminoethane-M IV, tetraacetate (edta ) (Fig. 8-1). 

Dendrimer 1 + is a classical example of a dendrimer containing a luminescent metal complex core. In this dendrimer the 2,2 -bipyridine (bpy) ligands of the [Ru(bpy)3] +-type core carry branches containing 1,2-dimethoxybenzene- and 2-naphthyl-type chromophoric units [15]. 

Bpym is a bis(a-diimine) ligand, and its similarity to the well-known 2,2 -bipyridine (bpy) and 1,10-phenanthroline (phen) ligands has attracted the... 

For convenience, many of the examples cited here will come from our own work. In our work we have taken advantage of the synthetic flexibility offered by the system shown below which is based on the ligand 2,2 -bipyridine (bpy). Synthetic studies... 

The direct borylation of arenes was catalyzed by iridium complexes [61-63]. Iridium complex generated from [lrCl(cod)]2 and 2,2 -bipyridine (bpy) showed the high catalytic activity of the reaction of bis (pinaco la to) diboron (B2Pin2) 138 with benzene 139 to afford phenylborane 140 (Equation 10.36) [61]. Various arenes and heteroarenes are allowed to react with B2Pin2 and pinacolborane (HBpin) in the presence of [lrCl(cod)]2/bipyridne or [lr(OMe)(cod)]2/bipyridine to produce corresponding aryl- and heteroarylboron compounds [62]. The reaction is considered to proceed via the formation of a tris(boryl)iridium(lll) species and its oxidative addition to an aromahc C—H bond. 

The di-/.t-oxo Mn(III,IV) complex in presence of 2,2 -bipyridine (bpy) chelating ligand was first reported in 1960 by Nyholm and Turco. " and structurally characterized in 1972 by Plaksin... 

Pyridine-based ligands which have been used for dendrimers are 2,2-bipyridine (bpy) 17,2,3-bis(2-pyridyl)pyrazine (2,3-dpp) 18 and its monomethylated salt 19, and 2,2 6, 2"-terpyridine 20. Their transition metal complexes possessing dendritic structures were first reported in the collaborative work of Denti, Campagne, and Balzani whose divergent synthetic strategy has led to systems containing 22 ruthenium centers. - The core unit is [Ru(2,3-dpp)3] 21 which contains three... 

Applications to Small Molecules. - 2.2.1 Intensity of Half-field Transition or Resolved Dipolar Splitting. In the pH range 8-10 the dominant species in solutions of Cu(II) and 2,2 -bipyridine (bpy) is [Cu(bpy)(OH)]22+.30 Well-resolved EPR spectra were obtained. The value of the zero-field splitting parameter D and the relative intensity of the half-field transition gave r = 3.4 A. 

Instead, complexes with chiral chelates of the 2,2 -bipyridine (bpy) ligand could lead to asymmetric induction in the synthesis of chiral p-lactams. 

One of the most common types of ligand in supra molecular photochemistry is the bidentate chelate 2,2 bipyridine (bpy, 11.1), which represents the first member of the homologous series of polypyridyls that includes 2,2 6, 2"-terpyridine (tpy, 11.3) and carries on up to the helicate-forming sexipyridine... 

NiCRA-bpyA NiCRA complex containing 2,2 -bipyridine (bpy) effects homocoupling of aryl halides (Ullmann coupling), often in high yield, which can be improved in some cases by addition of KI or Nal. When used in a catalytic amount, reduction to an alkane is the main side reduction. 

Thin films of simple Er111 complexes with aza aromatic ligands such as 2,2 -bipyridine (bpy), 1,10-phenanthroline (phen) or 2-dithienyl-2,2/-bipyridazine (dithi, fig. 115) doped into polymethylmethacrylate (PMMA), orpolyl[2-mcthoxy-5-(3, 7 -dimethyl-octylo.xy)]-/ -phenylene vinylene (MDMO-PPV) have been fabricated. The dithi complex is the most promising, with the strong luminescence of the MDMO-PPV matrix quenched by a factor 100 upon doping (Koppe et al., 2001). No other quantitative data are however reported. 

Aromatic C-H borylation is catalyzed by an Ir complex with a small and electron-donating ligand, for example PMe3, l,2-bis(dimethylphosphino)ethane (dmpe), 2,2 -bipyridine (bpy), and 4,4,-di-tert-butyl-2,2 -bipyridine (dtbpy) (Table 1)... 

Apart from the catalytic properties of the Mn-porphyrin and Mn-phthalo-cyanine complexes, there is a rich catalytic chemistry of Mn with other ligands. This chemistry is largely bioinspired, and it involves mononuclear as well as bi- or oligonuclear complexes. For instance, in Photosystem II, a nonheme coordinated multinuclear Mn redox center oxidizes water the active center of catalase is a dinuclear manganese complex (75, 76). Models for these biological redox centers include ligands such as 2,2 -bipyridine (BPY), triaza- and tetraazacycloalkanes, and Schiff bases. Many Mn complexes are capable of heterolytically activating peroxides, with oxidations such as Mn(II) -> Mn(IV) or Mn(III) -> Mn(V). This chemistry opens some perspectives for alkene epoxidation. 

Figure 12 Molecular structures of four bischelating ligands commonly used to form octahedral Ru- and Rh-complexes for attachment to DNA phenanthrenequinone diimine (phi), dipyridophenazine (dppz), 5-(amido-glutaric acid)-l,10-phenanthroline (phen ), and 2,2 -bipyridine (bpy).

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