Effect of Organic Ligands

For example, replacement of one CO by stronger a-acceptor ligands P(OPh)3 or PPhg in the complex HCo(CO)4 reinforces the Co-H bond and causes a marked decrease in the value [3]. In this respect, HCo(CO)3PPh3 tpK = ( .96) is comparable with the second dissociation of phosphoric acid tpK = ( .92). HCo(CO)3P(OPh)3 (piC3 = 4.95) is similarly acidic to acetic acid pK =4 .95). In spite of the problems in the exact determination of the p/C values in several solvents [4], HCo(CO) is by far the most acidic compound among these complexes, comparable with some mineral acids such as HI, HBr, or H2SO4 [5]. As a beneficial side effect, phosphorus-modified Co complexes are thermally more stable than HCo(CO)4. 

A similar effect was attributed to the SnClg ligand in platinum-catalyzed hydroformylation. Because of its inherent trans effect, SnCl3 activates the Pt-H bond and thus facilitates its insertion into the olefin [6]. The same, but less pronounced effect was found by quantum chemical calculations for the migratory insertion of CO into the Pt-alkyl bond [7]. 

Because of the properties of organic ligands, the whole catalytic cycle can be accelerated or, in the worst case scenario, totally blocked. Consecutive or side reactions may be favored. Modification of cobalt catalysts with phosphines not 

A volcano curve lucidly describes the dependence of the reaction rate on the phosphor/rhodium ratio [16]. 

The shift of equilibria depends on the concentration of the ligand, its coordination properties, and the CO partial pressure. For each catalytic system, an optimum has to be identified, in order to avoid catalysis by the unmodified catalyst HRh(CO) (I). On the other hand, with an excess of the organic ligand, 

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The effect of organic ligands on the exchange reaction between Fe III) and... 

The effect of organic ligands on dissolution of feldspar at ambient temperature has been observed by several groups to follow the same order as that observed by Furrer and Stumm (1986) for alumina citrate, oxalate > salicylate, tartrate > aspartate, acetate (Drever and Stillings, 1997). High-temperature studies of aluminosilicate dissolution in the presence of organic acids have also been completed, but are not reviewed here (see, however the review by Oelkers and Schott, 1998). 

Chin P. K. F. and Mills G. L. (1991) Kinetics and mechanism of kaolinite dissolution—effects of organic ligands. Chem. Geol. 90, 307-317. 

Golubev, S.V. and Pokrovsky, O.S., Experimental study of the effect of organic ligands on diopside dissolution kinetics, Chem. Geol., 235, 377, 2006. 

Effects of organic ligands on the adsorption of trace elements onto metal oxides and organo-mineral complexes... 

The objective of the present study is to examine the desorption kinetics of Cd following its adsorption on iron oxides. To simulate the effects of organic ligands in soil rhizosphere environment and chloride-bearing fertilizer, Cd desorption caused by citrate, acetate and chloride was investigated. 

Puzder A, Williamson AJ, Zaitseva N, Galli G, Manna L, Alivisatos AP (2004) The effect of organic ligand binding on the growth of CdSe nanoparticles probed by Ab initio calculations. Nano Lett 4 2361... 

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