Pyridyl complexes

Kwiatek and Seyler were the first to report that many organopenta-cyanides, when treated first with acid and then with alkali, liberate nitriles 110). This reaction occurs with unsubstituted primary and secondary alkyl, benzyl, vinyl, and phenyl complexes, while allyl, 2-oxo-, 2-hydroxy-, and 2-alkoxy complexes simply release the organo-ligand on treatment with acid, and 1-cyanoalkyl and a-pyridyl complexes are stable 105) (see also Table IV). The yield of nitrile is usually far from quantitative and is... 

The earliest NLO studies involving metal pyridyl complexes were reported by Frazier et al. in 1986 who investigated the SHG properties of various group 6 metal pyridyl carbonyls.63 Although most of the complexes tested show little or no activity, (6) and (7) have respective SHG efficiencies of 0.2 and 1.0 times ADP using a 1,064 nm laser.63 Shortly after, Calabrese and Tam reported SHG from the Re1 complex (8).64 Subsequent studies by Eaton and Tam et al.65,66 describe the preparation of inclusion compounds of various metal complexes with thiourea or tris-ort/ o-thymotide. Unfortunately, none of the complexes [W(CO)5L] (L = pyridine, py, or a 4-substituted py) produce SHG-active materials.65,66... 

Some general aspects of linked bis-tacn, bpta and bis-benzimidazole-pyri-dyl ligand and their Fe(II)Fe(II) compounds have been mentioned in Sect. 2.1 and Sect. 2.2 [21, 22, 28]. Only the helical [Fe2L3]4+ bis-benzimid-azole-pyridyl complex shows SCO and it was studied in solution. We are pursuing work on weakly linked compounds, with Toftlund, using a butane-linked dinitrile ligand, and this is mentioned in Sect. 6. 

When 114 is treated with a variety of alkene substrates, facile insertion into the aza-zirconacycle takes place (—> 115). The derived azazirconacyclopentanes are formed with various, but generally high, levels of diastereoselection, depending on the nature of alkene substituents. As illustrated in Scheme 6.36, the non-racemic (ebthi)Zr(r 2-pyridyl)+ complex has been shown to participate in an asymmetric and catalytic C—C bond-forming reaction. 

DR. SIDERS The edge atoms on the rings of the tris-bi-pyridyl complexes that we considered are a long way out from the central metal ions. For that reason we thought that an estimate such as Hopfield s, based on a carbon-carbon overlap, would be more appropriate than one based on a metal-metal overlap. 

Dobson, J.C. Taube, H. Coordination Chemistry and Redox Prop ies of Poly-pyridyl Complexes of Vanadium(II). Inorg. Chem. 1989,25, 1310-1315. 

The stability of the intermediate will depend in part on the relative values of ki and k2. The more negative CuGI)/Cu(I) redox potential observed for the pyridyl complex 2 would probably result in a larger ki in the reaction of this compound with O2, compared to the pyrazolyl analog. With the assumption that comparable k2 values would be observ in the two systems, the peroxo dicopper(II) intermediate will be more stable (i.e. longer lived) for the case of the pyridyl donors. 

Of particular interest are the proton-coupled multielectron transfers of high-valent oxorhenium (poly)pyridyl complexes [6, 15-18, 35]. This behavior is... 

Further variations on the theme have been achieved54 by anchoring species such as [RuivO-(terpy)(py)]2+ or complexes of osmium.55 Iron complexes have also been studied for example, evaporation of a solution containing [Fe(CN)5(H20)]3 and PVP on to an electrode will immobilize the pentacyanoferrate as a pyridyl complex, one in three available pyridyl groups being used to avoid precipitation prior to evaporation of solvent. 

The pyridyl complex Cp 2Y(2-pyridyl) reacts both with excess (1 bar) and 1 equivalent of CO to yield a n-r)2 t/2-dipyridylketone fragment by unexpected CO insertion (Eq. 43) [283]. The Y-O bond distances are in the range of bridging alkoxide ligands (Table 18). 

The stereospecificity of this cycloaddition process can be utilized in setting the stereochemistry of substituents on the 7-azanorbomane nucleus. For example, reactions of 22 with the methyl esters of Z- and -3-(3 -pyridyl) acrylates afford the corresponding exo and endo pyridyl complexes 86a and 89a, respectively (Figure 17). 

Figure 4.15 Schematic representation of the sequential steps taken for the formation of multilayers based on electrostatic self-assembly using cationic polymers and anionic a-ZrP sheets (see text for further details). Reprinted from Coord. Chem. Rev., 185-186, D.M. Kaschak, S.A. Johnson, C.C. Waraksa,J. Pogue and T.E. Mallouk, Artificial photosynthesis in lamellar assemblies of metal poly(pyridyl) complexes and metalloporphyrins, 403-416, Copyright (1999), with permission from Elsevier Science...

The rf-N,C bonding can also occur in deprotonated pyridines,104 i.e., pyridyl complexes made by reactions such as (9-6). 

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