Ions as Competitive Ligands

In the ferric chloride systems the tetrahedral species [FeCl2(TMP)2]+, FeCl3(TMP) and [FeCU]" are present and it appears that FeCls dissolved in trimethyl phosphate undergoes autocomplex formation" 127 is known to occur in triethyl phosphatei s. With azide ions as competitive ligands octahedral units are produced" . 

The main mechanism of ligand adsorption is ligand exchange the surface hydroxyl is exchanged by another ligand. This surface complex formation is also competitive OH ions and other ligands compete for the Lewis acid of the central ion of the hydrous oxide (e.g., the Al(iii) or the Fe(III) in aluminum or ferric (hydr)oxides). The extent of surface complex formation (adsorption) is, as with metal ions, strongly... 

On the other hand, Table 9 contains several data which cannot be interpreted by the relative donicities of donor solvent and competitive ligand the donor strength of the iodide ion is comparable to that of acetonitrile and the formation of tetraiodocobaltate in solvents of high donicity, such as DMA, DMSO and HMPA may not be anticipated. The formation of this species is however, complete with excess iodide ions and is due to the small values of the free enthalpies of the gas phase reactions ... 

Bidentate phosphorus ligands coordinated to metal ions may be more suitable for hydrogenation processes than for carbonylation processes the competition of CO as a ligand would then be excluded. 

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