Solvent co-ordination

Wishaw-Stokes equation. Evidence that the average number of molecules of the solvent co-ordinated by the solute decreases from four in dilute solution, to two in the range 0.5 to 5M, and one at higher concentrations was advanced. In solutions of AgNOg-CHgCN-HgO, Ag appears to be preferentially solvated by CHgCN, even when the concentration of acetonitrile in the solvent has been reduced to 4.7 mol%. ... 

The Pd oxidation number is reduced from +2 to -i-l by accepting a single electron. The Pd(I) is the active form which picks-up CO2. Further protonation and electron transfer form the dihydroxocarbene which eliminates water to afford the dicationic labile-carbonyl complex, which eliminates CO under solvent co-ordination. In an attempt to improve the catalytic properties (TOF and TON) the polydentate P-ligand has been modified in many different ways by changing the central P-donor atom as shown in Fig. 8.4 without any apparent gain in efficiency. 

When there is a large difference between ys(A) and ys(B) in the equation above, there must be signihcant deparmres from dre assumption of random mixing of the solvent atoms around tire solute. In this case tire quasi-chemical approach may be used as a next level of approximation. This assumes that the co-ordination shell of the solute atoms is hlled following a weighting factor for each of tire solute species, such that... 

An unusual enhancement of catalytic activity in a two-phase system has been reported by Fremy et al. (1998) for the hydroformylation of acrylic esters using Rh complex of TPTS as catalyst. Even though acrylic esters have reasonable solubility in water, rate enhancements in two-phase systems by a factor of 2 to 14 have been reported. It seems that water is not an inert solvent but also acts as a reactant or a co-ordinating solvent which can modify elementary steps of the catalytic cycle (Cornilis, 1997). 

Pd(H20)4] at 40°C [73]. A kinetic study indicated that internal attack on the Pd-co-ordinated nitrile ligand by the aqua (not hydroxide) ligand and external attack on the nitrile ligand by solvent water occur at a similar rate. 

It has been proven that the concentration of the reagent and the solvent used can become involved in the final yield of side reactions, as shown in Table 11.2. The use of water as a solvent and high concentrations of TMAH ensure better yields of the transmethylation reaction. This has been explained on the basis of the co-ordination chemistry, the solvent analyte mixture determines the reactivity of TMAH with respect to the reactants [12]. 

The commercially interesting metal complex pigments usually contain the co-ordinative tetravalent Cu+ + or Ni+ + ions, less commonly Co++ ions. The fourth coordination site is typically occupied by a solvent molecule with a free electron pair. It may also be engaged by the second nitrogen atom of a different pigment molecule, a phenomenon which is observed in azo complexes and similar materials. In the latter case, sandwich structures are obtained [5]. The copper and nickel complexes are mostly planar molecules. 

The seven-co-ordinate complexes [R MV(CO)e], [RnMVlCOlgPPhj] (R M = PhjSn, EtHg, or PhjPAu), and [Ph3SnV(CO)4(diphos)] have been prepared by the reaction of [VICO) ]" salts with R MC1. The substituted complexes are very prone to heterolytic cleavage in weak donor solvents, and reactions of some of these tin compounds are included in Scheme 2, which describes convenient syntheses of [HV(CO)4(diphos)], [IV(CO)4(diphos)], and [VlCOj ldiphos)]. " ... 

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