2- pyridine complexes structure

Nickel, tris(l, 10-phenanthroline) racemization, 1,24. 466 solid state, 1, 467 structure, 1,64 Nickel complexes, 5,1-300 acetylacetone alcoholysis, 2, 380 pyridine complexes, 2, 386 solvolysis, 2,379 structure, 2,388 amidines... 

The Ullman reaction has long been known as a method for the synthesis of aromatic ethers by the reaction of a phenol with an aromatic halide in the presence of a copper compound as a catalyst. It is a variation on the nucleophilic substitution reaction since a phenolic salt reacts with the halide. Nonactivated aromatic halides can be used in the synthesis of poly(arylene edier)s, dius providing a way of obtaining structures not available by the conventional nucleophilic route. The ease of halogen displacement was found to be the reverse of that observed for activated nucleophilic substitution reaction, that is, I > Br > Cl F. The polymerizations are conducted in benzophenone with a cuprous chloride-pyridine complex as a catalyst. Bromine compounds are the favored reactants.53,124 127 Poly(arylene ether)s have been prepared by Ullman coupling of bisphenols and... 

Ghosh et al. [70] reviewed a few years ago the utihty of C2-symmetric chiral bis(oxazoline)-metal complexes for catalytic asymmetric synthesis, and they reserved an important place for Diels-Alder and related transformations. Bis(oxazoline) copper(II)triflate derivatives have been indeed described by Evans et al. as effective catalysts for the asymmetric Diels-Alder reaction [71]. The bis(oxazoline) Ugand 54 allowed the Diels-Alder transformation of two-point binding N-acylimide dienophiles with good yields, good diastereos-electivities (in favor of the endo diastereoisomer) and excellent ee values (up to 99%) [72]. These substrates represent the standard test for new catalysts development. To widen the use of Lewis acidic chiral Cu(ll) complexes, Evans et al. prepared and tested bis(oxazoHnyl)pyridine (PyBOx, structure 55, Scheme 26) as ligand [73]. 

Condensation of triallylborane with octa-l,7-diyne (130-140 °C, 3 h) followed by treatment with methanol afforded a mixture of stereoisomeric l,4-bis(3-methoxy-3-borabicyclo[3.3.1]non-6-en-7-yl)butanes 66a and 66b (Scheme 26). Hydroboration of the latter with H3B-THF in THF and heating under reflux for 2 h gave rise to a mixture of racemic bis-l-boraadamantanes 67a and meso-ioim 67b in 94% overall yield. Pure racemate 67a was isolated by crystallization from the reaction mixture (THF) and converted to the pyridine complex 64 whose structure was established by X-ray diffraction analysis. 

Previous studies of the photochemistry of alkylchlorodiazirines have shown that the yield of trappable carbene is sensitive to the alkylcarbene structure. A laser flash photolysis study of phenanthridenes (91), precursors of alkylchlorocarbenes, in the presence of pyridine, has ruled out the intermediacy of a carbene-pyridine complex which partitions between pyridine-ylide formation and [1,2]-H shift. ... 

Mesoionic 4-amino-l,2,3,5-thiatriazoles constitute the only class of mesoionic 1,2,3,5-thiatriazoles known. They are prepared by the reaction of l-amino-l-methyl-3-phenylguanidine with approximately 2 equivalents of thionyl chloride with pyridine as solvent (88ACS(B)63>. They are obtained as the yellow 1 1 pyridine complexes (17). The dark-violet mesoionic 1,2,3,5-thiatriazole (18) was liberated on treatment with aqueous potassium carbonate (Scheme 3). The structure is established on the basis of elemental analysis and spectroscopic data. In particular, the IR spectrum is devoid of NH absorptions. Compound (18) exhibits a long-wavelength absorption at 463 nm in methanol. When mixed with an equivalent amount of pyridinium chloride, complex (17) is formed and the absorption shifts to 350 mn. The mesoionic thiatriazoles are sensitive towards mineral acids and aqueous base and although reaction takes place with 1,3-dipolarophiles such as dimethyl acetylene-dicarboxylate, a mixture of products were obtained which were not identified. 

Chromium atoms provide a unique route to 7r-pyridine complexes. No simple product has been isolated from the reaction of pyridine and chromium atoms, but 2,6-dimethylpyridine and chromium atoms give a low yield of (i 8-2,6-dimethylpyridine)2chromium characterized by a crystal structure showing essentially planar pyridine rings (103). A mixture of pyridine with either PF3 or mesitylene gives a 7r-C5H5N complex ... 

The importance of the carboxylate donors is underlined by a study of the lanthanide coordination chemistry of the similar terdentate ligand 2,6 -bis( 1 -pyrazol-3 -yl)pyridine, L24 (63). The complex structure of [Tb(L24)3][PF6]3, shown in Fig. 11, appears to be fairly robust in methanolic solution, with Horrocks analysis (q = 0.6) suggesting the 9-coordinate structure is retained the small quenching effect of outer sphere coordination explains the q-value. However, in aqueous solution, the lability of the ligands dramatically changes the luminescence. Whilst the emission decays are not exactly single exponential, approximate lifetimes in H20 and DoO suggest a solvation value of 4-5. 

In sulfamation, also termed IV-sulfonation, compounds of the general structure I NSC H are formed as well as their corresponding salts, acid halides, and esters. The reagents are sulfamic acid (amido—sulfuric acid), SO3—pyridine complex, S03—tertiary amine complexes, aliphatic amine—S03 adducts, and chlorine isocyanate—S03 complexes (3). 

Recently, de Koning et a/.157 have found that hydride transfer takes place exclusively to the 4-position of pyridine, using zinc hydride and magnesium hydride. The reaction is fairly slow and eventually is completed to yield the pyridine complex of bis(l,4-dihydro-l-pyridyI)zinc and its magnesium analog, Zn(NR2)2-2py and Mg(NR2)2-2py, where NR2 is the 1,4-dihydropyridyl residue. H- and 13C-NMR spectral data give consistent answers in agreement with the proposed structures 112 and 113. 

The first synthesis of the borepin ring was performed in 1960 by van Tamelen and coworkers starting from 2,2 -dilithiobibenzyl according to Scheme 39 (60TL(8)14). The ethanolamine derivative (203) was isolated and characterized. Reduction with LAH gave a product, isolated as an unstable pyridine complex. The Lewis acid part of the complex was considered to have structure (204), but the conclusions were tentative, partly due to its re-oxidation to (20S). The corresponding synthetic strategy to non-fused borepins met with difficulties 4,5-dihydroborepin (206) could be prepared, but it was not possible to introduce the third double bond. 

Com corroles form five- and six-coordinate complexes in the presence of ligands but the second association constant is much lower than the first. A five-coordinate triphenylphosphine complex was isolated and shown to have a distorted square pyramidal structure with the Co atom displaced out of the N4 plane by 0.28 A.245 In pyridine, it is converted to a diamagnetic bis-pyridine complex.239 Isocyanides displace pyridine ligands to form five-coordinate complexes, from which amine complexes may be obtained (Scheme 78). 

FIGURE 6. ORTEP drawing of the experimental structure of the trimethylsilyl-pyridine complex (7). Si—N bond length in A. Reproduced by permission of Wiley-VCH from Reference 69... 

---