Pyridine as ligand

Shieh, S.-J., Hong, X., Peng, S.-M. and Che, C.-M. (1994) Synthesis and crystal structure of a luminescent onedimensional phenylacetylide-gold(I) polymer with 2,6-bis(diphenylphosphino) pyridine as ligand. Journal of the Chemical Society, Dalton Transactions, 3067-3068. 

Phenols such as 2.6-dimethyIphenol are converted rapidly and in high yield to high molecular weight polymers at room temperature with oxygen in the presence of amine complexes of copper salts as catalyst. Much of the work described in the literature has been performed with copper (I) chloride as catalyst and pyridine as ligand and solvent. Other amines, primary, secondary or tertiary can be used as ligands for the catalyst. Autoxidation of copper (I) chloride in pyridine results in the... 

In the presence of 3-8 mol equiv. of pyridine as ligand (compared with Co) the phenomenon of ligand-accelerated catalysis [8] is observed with higher activity and improved selectivity of the catalyst system [9]. The cobaltcarbonyl/ pyridine catalyst system is applied industrially for the synthesis of higher alkanoic acids, e.g., the hydrocarboxylation of isomers of undecene yields dodecanoic acid with approximately 80% selectivity [10],... 

In the second step, the concentration of pyridine as ligand must be low because it has an inhibitory effect on the hydroalkoxycarbonylation. In situ isomerization to the 4-pentenoic acid ester is a prerequisite for the subsequent carbonylation which provides dimethyl adipate. To ensure internal double-bond rearrangement, the temperature of the reaction is increased to 160-200 °C to give dimethyl adipate with 80 % selectivity. After hydrolysis of the ester, adipic acid is obtained with an overall selectivity of about 70% [1]. So far, this process has been performed on pilot-plant scale. 

Dioxygen activation at mononuclear nonheme iron active sites (enzymes, models, and intermediates with pyridines as ligands) 04CRV939. 

With pyridine as ligand, two types of complexes have been isolated I(C6H6N)X (X = acid radical) and I(C6H5N)2X. The former type has been formulated as a nonelectrolyte, [I (C5H5N)X], and the latter as an electrolyte, [I (CsH sN) s]X. ... 

Figure 4 Substituent effect of 4-Y-substituted pyridines as ligands on photophysical properties of bis-bipyridyl nitro complexes of ruthenium (II). Reprinted with permission from (2014JPCA(n8)6216). Copyright 2014 American Chemical Society.

We have investigated the ESR spectra of a series of copper(II) complexes with substituted pyridines as ligands to see whether the substitution of the pyridine ligand has an effect on the bonding parameters of the complex. Furthermore we have compared the complex with unsubstituted pyridine in two different host lattices. To avoid any steric effects, only complexes with pyridine derivatives that are substituted in 4-position were studied. 

A similar pattern of results was obtained for complexes containing a variety of substituted pyridines as ligands. However, a number of significant differences have been found which seem to support the above interpretation. For example, for L = isoquinoline the results are consistent with the view that isoquinoline forms weaker o -bonds to the metal than does pyridine but that it is better able to accept back-coordinated electrons in a 7r-bond. Similarly, marked differences in the data obtained for complexes with 3-alkylsubstituted and 4-alky Substituted pyridines suggest that the former amines are poorer ir -acceptors, a conclusion in accord with publShed information on the mesomeric effects of 3- and 4-substituents and the calculated electronic charge densities at different ring positions (2). 

The cationic complexes with 2,6-bis(A-pyrazolyl)pyridine as ligand, 237 and 238, have been prepared by a similar method. A dinuclear complex with bridging SEt2 ligands and four biphenyl ligands 239 exists as a mixture of stereochemical atropisomers. ... 

FlS 1 199 N J Hg meso tetraphenyl porphyrin with pyridine as ligand 340 Y14... 

Serrano et al. [23] have used other substituted pyridines as ligands for metallomeso-gen formation. Thus the cis-iridium complexes, 13, with short chains formed monotropic nematic phases, while those with longer chains led to SmA phases. The related rhodium complexes are also mesogenic. This is an example of a mesogenic complex formed with a nonmesogenic ligand. 

Recently, it was shown that the electroreduction of catalytic simple cobalt salts in the presence of functionalized organic halides leads to an organometallic compound [19] that can react with different substrates in DMF or acetonitrile containing pyridine as ligand (Scheme 15.6). 

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