Chloride coordination

The structural characterization of this assembly has revealed that chloride coordination (via hydrogen bonding to the protonated pyridyl groups of the strands) induce the strands to adopt a double-helical structure in the solid state. 

Fulton JL, Hoffmann MM, Darab JG (2000a) An X-ray absorption fine structure study of copper(I) chloride coordination structure in water up to 325°C. Chem Phys Lett 330 300-308 Fulton JL, Hoffmann MM, Darab JG, Palmer BJ, Stem EA (2000b) Copper(I) and Copper(II) Coordination stmcture under hydrothermal conditions at 325°C An X-ray Absorption Fine Stmcture and Molecular Dynamics Study. JPhys Chem A104 11651-11663... 

It seems safe to say that coordination will generally decrease the reactivity of donor atoms in the first row of the periodic table through steric effects. With some reactions the extent of this steric hindrance may be small. Ammonia can be transformed into chloramines when coordinated (34), and aromatic acid chlorides coordinated to A1C13 or TiCl4 may be esterified even when the functional group is a hindered one, as in mesitylene carbonyl chloride (47). These last reactions may proceed through a very reactive carbonium ion, whose existence is rendered possible by the polarization of the ligand which it suffers as a result of coordination. 

In this respect, the aromatic component of such Friedel-Crafts condensation may be considered to function as a nucleophilo, in which w-electrona attack the aluminum chloride-coordinated ethylene oxide ring. 

Chloride Coordination. This predominates over hydroxide coordination—i.e., [MCI] > [MOH] only if Equation 9 is valid. 

Aluminum chloride coordinates with 1-chloropropane to give a Lewis acid/Lewis base complex, which can be attacked by benzene to yield propylbenzene or can undergo an intramolecular hydride shift to produce isopropyl cation. Isopropylbenzene arises by reaction of isopropyl cation with... 

Chloride ion is a weaker nucleophile than bromide ion because it is smaller and less polarizable. An additional Lewis acid, such as zinc chloride (ZnCl2), is sometimes necessary to promote the reaction of HC1 with primary and secondary alcohols. Zinc chloride coordinates with the oxygen of the alcohol in the same way a proton does— except that zinc chloride coordinates more strongly. 

Salts usually have a dual effect on cationic polymerization (cf., Section VII.E.3). Tetrabutylammonium chloride coordinates strongly with Lewis acids, e.g., with BCI3 or SnCl4 to form tetrabutylammonium tetrachlo-roborate and pentachlorostannate, respectively. In the latter case, an excess of salt may lead to the formation of hexachlorostannate dianions. Thus, salts scavenge Lewis acid and reduce the polymerization rate in a way similar to nucleophiles. Recent analysis of model reactions by 119Sn NMR spectroscopy demonstrate a transformation of SnCl4 in the presence of the added salt ... 

Addition of chloride anion to the ligand-free (i.e., four coordinate) iron(III) corrole leads to a complex with chloride coordinated apically to the iron center. To... 

Extensive kinetics studies on water substitution by thiocyanate in [Mo4Q4(H20)i2]5+ (Q = S, Se), [Mo4S4(H20)i2]4+ and [Mo4S4(H20)12]6+ have been reviewed recently.6 Chloride coordinates to [Mo4S4(H20)i2]5+, equilibration constant 1.98 M-1, which is 103 times less than for thiocyanate.271... 

Zheng et al. [20] showed that KI decreases the temperature and diminishes the activation energy for the decompositions of five cobalt(III) ammine chloride coordination compounds containing the cations [Co(NH3)sX], where X=N3, NOj, Cr, C03 or NH3. The electron transfer step to Co " is regarded as exerting an important control on the decomposition. 

Or a solid-state oxidation process involving chloride coordination of surface cobalt centers ... 

CoC1(NH3)5]C12, pentaamminechlorocobalt(III) chloride. Coordinated ligands are shown in... 

The catalyst system for the modem methyl acetate carbonylation process involves rhodium chloride trihydrate [13569-65-8]y methyl iodide [74-88-4], chromium metal powder, and an alumina support or a nickel carbonyl complex with triphenylphosphine, methyl iodide, and chromium hexacarbonyl (34). The use of nitrogen-heterocyclic complexes and rhodium chloride is disclosed in one European patent (35). In another, the alumina catalyst support is treated with an organosilicon compound having either a terminal organophosphine or similar ligands and rhodium or a similar noble metal (36). Such a catalyst enabled methyl acetate carbonylation at 200°C under about 20 MPa (2900 psi) carbon monoxide, with a space-time yield of 140 g anhydride per g rhodium per hour. Conversion was 42.8% with 97.5% selectivity. A homogeneous catalyst system for methyl acetate carbonylation has also been disclosed (37). A description of another synthesis is given where anhydride conversion is about 30%, with 95% selectivity. The reaction occurs at 445 K under 11 MPa partial pressure of carbon monoxide (37). A process based on a montmorillonite support with nickel chloride coordinated with imidazole has been developed (38). Other related processes for carbonylation to yield anhydride are also available (39,40). 

Fig. 5 Pyridine ligands carrying a self-complementary hydrogen-bond moiety (carboxylic acid, in this example) provide a noncovalent directional tool for connecting infinite copper(I) chloride coordination polymers into an extended two-dimensional network.

Fig. 1 (a) Chloride coordination environment in tetramethylammonium chloride-(pyrrole)2 (Copyright Royal Society of Chemistry... 

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