Halo complexes formation

The insolubility of the Cu(I) halide salts, as well as the possibility of /x-halo-bridge formation between two copper atoms (as discussed later) or between the copper complex and the electrode surface, suggests that the presence of hahdes may alter the electrochemical properties observed for copper-containing solutions. 

ThermodynaMc Smdy of Complex Formation by Hydrogen Bonding in Halo-genoalkane-Oxygenated Solvent Mixtures—Halothane With Propyl Ether, Isopropyl Ether, 1,4-Dioxane, and 2,5-Dioxahexane (Dohnal et al., 1996)... 

Oxygen-containing solvents such as water, alcohols or ethers are such poor donors that few complexes with palladium(II) have been isolated. The most important class of complexes of this type consists of those containing water, which are formed as intermediates in the substitution reactions of palladium(II) when carried out in aqueous solution. In these reactions their formation is in competition with the second order reaction of the complex with the incoming ligand. The aqua complexes can also be formed by reaction of halo complexes with silver salts (e.g. N03, C104, BF4) in water. These complexes are acidic, being in equilibrium with hydroxo complexes in neutral or basic media. 

The pentahalides of Group VA are all strong Lewis acids that interact with electron pair donors to form complexes. This is typified by the formation of halo complexes,... 

The trivalent transplutonium halides have been extensively studied. Several reviews deal specifically with actinide halides. " In aqueous solution the mono- and bis-complexes have been characterized, with the formation of the latter decreasing down the halide series. For example, AmF and AmF2" have been studied, but only a very weak monochloride complex AmCP has been reported. These species are reported to have coordination numbers as high as 11, although recent EXAFS studies show that the hydration number decreases with increasing halide concentration (and ionic strength) at concentrations below which the halo complexes form. These data suggest the coordination numbers of the mixed aquo halo complexes are probably seven to ten. 

Give an overview of the formation of halo complexes of type [MX ] by the first row d-block metal ions, noting in particular whether discrete ions are present in the solid state. 

Many routes to 0x0 and imido compounds have been developed. Transition metal-oxo complexes are coimnonplace and, in many cases, are the most stable form of an element in air. Some imido compoimds, including the first imido complex, have been prepared from metal-oxo complexes (Equation 13.50). The reactions of some of the later metal-oxo compounds with a primary amine generate an imido species by extrusion of water. In other cases, metal-imido complexes are prepared from 0x0 complexes by the reaction of phosphmimines (Equation 13.51) or from 0x0 or halo complexes by the reactions of silylamines (Equations 13.52 and 13.53). The driving force for these reactions is the formation of phosphine oxide, silyl ethers, or silyl halides. 

It remained for G.N. Lewis (2), M.L. Huggins (3), and their contemporaries to interpret the primary and secondary valences of Werner in terms of the newly emerging electron patterns which were being used to explain "valence." Primary valences were normal covalent bonds (one electron from each bonded atom) and secondary valences were coordinate covalent bonds (two electrons for bond formation supplied by the ligand). The terms Lewis base and Lewis acid entered the literature. The Werner and Lewis-Huggins descriptions of stmcture and bonding were excellent for the metal-ammines, halo complexes of metals, and related species. Classical Werner coordination compounds fit the Wemer-Lewis description, and there were many of such compounds. 

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