Cationic supports

A complementary approach has been reported very recently [43]. hi this case negative charges were introduced into the salen ligand Iq (Fig. 14) with the aim of exchanging it on cationic supports, such as a layered double (Zn, Al) hydroxide. The expansion in the basal spacing indicated intercalation, at least partially, of the Ig-Mn complex between the layers of [Zn2,i5Alo,86(OH)6,o2]- The complex was used in the epoxidation of (i )-limonene with molecular oxygen and pivalaldehyde. The use of N-... 

Conducted in 10% CH2Cl2-90% acetonitrile for compounds [54] and [56] and in acetonitrile [55] upon addition of 2 equiv of the respective cation supporting electrolyte, 0.10 mol dm-3 TBABF4. The potential of the reduction current peak r, reversible q, quasi-reversible s, single reduction peak without corresponding reoxidation peak ec, electron transfer followed by a chemical reaction ec, ad, electron transfer followed by a chemical reaction with insoluble product which adsorbs on to the electrode surface. Prewaves are in parentheses. 

However, ab initio calculations [QCISD-(T)/6-31G //UMP2/6-31G ] on ethylene and its radical cation support an anti -7i-complex, in which the two components are joined by one long bond (190 pm), rather than the sandwich -type 71 complex. The complex is connected to two transition states leading to a (rhombic) cyclobutane radical cation (see above) or, by 1,3-H-shift, to 1-butene radical... 

Table 1. Rate of H2 gas generated catalytically per gram of catalyst (Ru + support resin) are compared for various anionic and cationic support resins in 20% NaBEL, 10% NaOH, 70% H20 solution at 25°C. All catalysts had 5 wt% Ru loading.

Red ReOs, which can be obtained by CO reduction of the heptaoxide at 175 280 °C, is a good electrical conductor with a metal-like temperatme dependence the d electron is clearly delocalized. It has octahedral Re and easily forms nonstoichiometric bronzes in which an alkali metal donates an electron to the metal-0x0 lattice and enters the stmetme as a cation. Supported ReOs is important in alkene metathesis catalysis. No Tc analog is known. Blue Re20s, brown Re02, and black Rc203 are also known. For Tc, the only lower oxide is TCO2. 

The reduction of Ti(OEP)(THF)2 in THF with Li under C2FI4 led to the formation of the dimeric Ti11 porphyrin complex with C2-bridged Ti atoms and two Li cations supported by the porphyrin ligands.273... 

Ferrous cations supported on Si02> Al20, and Ti02... 

The TPR spectra for Cu catalysts supported on silica and alumina displayed two maxima at 220 260°C and 200 310°C (Table 2). The toted hydrogen uptake in both cases corresponded to full reduction of Cu ( H2/Cu2+ 1). The Cu cations supported on alumina were reduced mainly during the lower temperature... 

The vapor phase synthesis of methacrylic acid from propionic acid and formaldehyde was studied [42]. In particular, the choice of alkali metal cation and loading were evaluated for their effect on the activity and selectivity of silica supported catalysts. Experiments were carried out in 0.5 in. (o.d.) quartz reactors equipped with 0.125 in. thermowells. Alkali metal cations supported on silica are effective base catalysts for the production of methacrylic acid. Silica surfaces exchanged with alkali metal cations are capable of chemisorbing propionic acid yielding surface-bound silyl propionate esters and metal propionate salts. The alkali metal cation influences the temperature at which desorption of the ester occurs (Cs < Na < Li < support). For silica catalysts of equimolar cation loading, activity and selectivity to methacrylic acid show the opposite trend, Cs > K. > Na > Li. Methacrylic acid selectivity reaches a maximum at intermediate cation loadings where interaction of adjacent silyl esters is minimized [42]. 

Milling anhydr MgCl2 with aromatic materials (e.g., naphthalene, durene) or polymers (e.g., polyethylene) forms stable free radicals that are radical cations supported on MgCl2... 

Calcium and magnesium may be bound in carbonates or in other compounds. They participate in exchange reactions and they serve as cations supporting the coagulation of colloids. 

Polycations on Derivatized Glass or Silica Since most aqueous packings contain functional groups that can dissociate to form anions, one may expect cationic polymers to be retained or adsorbed. There have been two approaches to this problem (1) preparation of cationic supports which repel the polycation, or (2) utilization of near-neutral supports. The pros and cons of both techniques will be discussed. 

A completely different approach to cluster ligands is the one exemplified by the use of [Co3(CO)9(/i3-C-COOH)]. This cluster may be considered as a trime-tallasubstituted acetic add and, as such, has been used to synthesize trimetalla-substituted acetate complexes with Mo-Mo multiple bonded dinudear moieties and with [M4(/i4-0)j polynuclear oxo-cations supporting their description as so-called basic acetates. [398, 400] One of these remarkable salts is, for instance, constituted by a tetrahedral [Co4(/i4-0)] oxo-cation edge-bridged by six [Co3(CO)9(jM3-C-COO)] tricobaltasubstituted acetate anions. [398]... 

Bulk data of solvation of tetravalent cations supports octa-coordination in the first hydration sphere whereas the actinyl(VI) cations seem to favor hexa-coordination in the plane perpendicular to the axial actinyl group. The trends in the thermodynamic parameters of hydration across the actinide series are essentially similar to those observed for the lanthanide ions and the small differences can be attributed to relativistic effects in the actinides which causes changes in the relative energies of the s, p, d, and f orbitals. 

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