Ligand bipyridine

An example of this type of dendrimer is the polynuclear species that can be prepared from 2,3-bis(2-pyridyl)pyrazine as bridging ligands, bipyridines as terminal bgands, and either Ru(II) or Os(II) as the metal centre. 

Later, several other copper catalysts bearing dinitogen ligands [bipyridine derivatives (76),232,233 diamines (77),234 bis(azaferrocene) (78),235 bisferrocenyldiamine (79),159 and bis(oxazoyl) binaphthyl (80)236] have been introduced (Scheme 62), but asymmetric induction by them does not exceed that by complex (75). 

Probably Pb(II) complexes formed with either the closoanions B10H9SMe2 and B1211MNEtf [960] or the arahno anion 6-B10H9CN [965], both containing amine ligands (bipyridine or dipyridylamine) coordinated with a metal, have a similar structure. 

Niobium and tantalum halides also fonn adducts with numerous N-donors. Their reactions with pyridine and related ligands (bipyridine, phenanthroline, 7-azaindole ) depend critically on the reaction conditions. Indeed, aromatic amines have a tendency to reduce the metal to oxidation state IV especially for niobium but the reduction can be prevented, even at rt, by an appropriate choice of the solvent (equations 2a-c). Imide adducts M(NR)Cl3L2 are obtained with primary or secondary amines. ... 

The reader is referred to other chapters for (i) aromatic nitrogen-donor nonbridging ligands bipyridines (Chapter 1.1), terpyridines (Chapter 1.3), phenanthrolines (Chapter 1.2), porphyrins... 

Several groups have developed metal-mediated alternative base pairs with [2 - - 2] coordination by using the bidentate ligands bipyridine, 8-hydroxyquinoline, hydroxypyridone, or salicylaldehyde. N, N -Bis(salicylidene)ethylenedi-amine (salen), a four-dentate ligand that coordinates through two nitrogen and two oxygen atoms, is also included in this section because of the similarity between its coordination complexes and those with bis(salicyladehyde) coordination. 

The three ligands bipyridine (bipy) (22-X), 1,10-phenthroline (phen) (22-XI), and terpyridine (terpy) (22-XII) form complexes with a variety of... 

Kinetic data on complexing of other +2 transition metal ions is sparse and scattered. However, sufficient information is available to allow a comparison to be made of the rates of formation of complexes of Mn Fe Co " " and Cu with the common ligands bipyridine, terpyridine and phenanthroline (Table 13). There follows an account of some of the more recent studies. 

The arm-first methodology for the synthesis of star polymers requires the synthesis of proper macromolecular ligands. Bipyridine-ftmctionalized polymers have been frequently used for this purpose. ATRP techniques have been used to prepare bipyridine-centered or end-functionalized PSs and PMMAs. However, other techniques have been used as well. The ROP of s-caprolactone and lactide was irutiated by hydroxymethyl bipyridine initiators in the presence of tin catalysts. Coupling reactions of PEO chains to functionalized bipyridines have also been carried out (Scheme 68). 

Photoexcited fluorescence from spread monolayers may be studied [158,159] if the substance has both a strong absorption band and a high emission yield as in the case for chlorophyll [159]. Gaines and co-workers [160] have reported on the emission from monolayers of Ru(bipyridine)3, one of the pyridine ligands having attached C g aliphatic chains. Ruorescence depolarization provides information about the restriction of rotational diffusion of molecules in a monolayer [161], Combining pressure-area... 

Interestingly, the rate constants for Diels-Alder reaction of the ternary complexes with 3.9 are remarkably similar. Only with 2,2 -bipyridine and 1,10-phenanthroline as ligands, a significant change in reactivity is observed. It might well be that the inability of these complexes to adopt a planar geometry hampers the interaction between the copper ion and the dienophile, resulting in a decrease of the rate of the catalysed Diels-Alder reaction. 

Crystal stmctures of complexes of copper(II) with aromatic amine ligands and -amino acids " " and dipeptides" have been published. The stmctures of mixed ligand-copper complexes of L-tryptophan in combination with 1,10-phenanthroline and 2,2 -bipyridine and L-tyrosine in combination with 2,2 -bipyridine are shown in Figure 3.2. Note the subtle difference between the orientation of the indole ring in the two 1,10-phenanthroline complexes. The distance between the two... 

In contrast, investigation of the effect of ligands on the endo-exo selectivity of the Diels-Alder reaction of 3.8c with 3.9 demonstrated that this selectivity is not significantly influenced by the presence of ligands. The effects of ethylenediamine, 2,2 -bipyridine, 1,10-phenanthroline, glycine, L-tryptophan and L-abrine have been studied. The endo-exo ratio observed for the copper(II)-catalysed reaction in the presence of these ligands never deviated more than 2% from the endo-exo ratio of 93-7 obtained for catalysis by copper aquo ion. 

Copper(I) tends towards a tetrahedral coordination geometry in complexes. With 2,2 -bipyr-idine as a chelate ligand a distorted tetrahedral coordination with almost orthogonal ligands results. 2,2 -Bipyridine oligomers with flexible 6,6 -links therefore form double helices with two 2,2 -bipyridine units per copper(I) ion (J. M. Lehn, 1987,1988). J. M. Lehn (1990 U. Koert, 1990) has also prepared such helicates with nucleosides, e.g., thymidine, covalently attached to suitable spacers to obtain water-soluble double helix complexes, so-called inverted DNA , with internal positive charges and external nucleic bases. Cooperative effects lead preferentially to two identical strands in these helicates when copper(I) ions are added to a mixture of two different homooligomers. 

The size-exclusion and ion-exchange properties of zeoHtes have been exploited to cause electroactive species to align at a zeoHte—water interface (233—235). The zeoHte thus acts as a template for the self-organization of electron transfer (ET) chains that may find function as biomimetic photosynthetic systems, current rectifiers, and photodiodes. An example is the three subunit ET chain comprising Fe(CN)g anion (which is charge-excluded from the anionic zeoHte pore stmcture), Os(bipyridine)3 (which is an interfacial cation due to size exclusion of the bipyridine ligand), and an intrazeoHte cation (trimethylamino)methylferrocene (F J ). A cationic polymer bound to the (CN) anion holds the self-assembled stmcture at an... 

Coordination Compounds. A large number of indium complexes with nitrogen ligands have been isolated, particularly where Ir is in the +3 oxidation state. Examples of ammine complexes include pr(NH3)3] " [24669-15-6], prCl(NH3)] " [29589-09-1], and / j -pr(03SCF3)2(en)2]" [90065-94-4], Compounds of A/-heterocychc ligands include trans- [xCX py)][ [24952-67-8], Pr(bipy)3] " [16788-86-6], and an unusual C-metalated bipyridine complex, Pr(bipy)2(C, N-bipy)] [87137-18-6]. Isolation of this latter complex produced some confusion regarding the chemical and physical properties of Pr(bipy)3]3+ (167). 

Chiral carbenoid complexes with 2,2 -bipyridine ligands for asymmetric synthesis 98YGK764. 

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