Solvated complexes

Figure 7.22 (a) Structure of the dimeric unit in the solvated complex [Ga(/) -C6H6)2][GaCl4].3QH6 indicating the... 

Solvation, complexation, and reactivity of poly(A-vinyllactams) 98MI29. 

Measurements of polymerization rate and parallel measurements on the resultant polymer microstructure in the butadiene/DIPIP system cannot be reconciled with the supposition that only one of the above diamine solvated complexes (eg. Pi S) is active in polymerization 162). This is probably true of other diene polymerizations and other diamines. The observations suggest a more complex system than described above for styrene polymerization in presence of TMEDA, This result is clearly connected with the increased association number of uncomplexed diene living ends which permits a greater variety of complexes to be formed. 

At this stage of development of the subject it is appropriate to consider a number of empirical rules which may serve to indicate the important variables. It would seem likely that (i) there will be competitition between each species in the system for the sites available at the electrode surface, and that (ii) for each species in the system there will be an equilibrium between the solution and the adsorbed state. Thus it would be expected that the solution constituents would affect these equilibria in two ways (a) if one of the constituents of the medium is itself adsorbed, the reactant will tend to be displaced (b) if the reactant is strongly solvated, complexed or ion paired by constituents of the medium, the species in solution will be favoured. 

The unsolvated complexes Li[P(NR)(NR )] In may adopt monomeric, dimeric or tetrameric structures as indicated by the examples (4) [7], (5) [6] and (6) [7]. Variable temperature NMR studies reveal that the tetramer (6) dissociates into the corresponding dimer in solution [7]. The dimeric cubic structure is stabilized in the THF-solvated complex THF-Li [P(N Bu)2] 2 (7) [8]. 

Several hydrido(phenoxo) complexes of nickel, trans-[NiH(OPh)L2] (6) (a L= P Prs b L = PCys c L = PBnj), have been prepared by the metathesis reaction of NaOPh with trans-[NiHClL2] (Eq. 6.6). The complex 6c was obtained as the phenol-solvated complex whose structure was determined by X-ray analysis [9]. An analogous platinum complex trans-[PtH(OPh)(PEt3)2] (7) was prepared by the reaction of trans-[PtH(N03)(PEt3)2] with NaOPh (Eq. 6.7). The complex 7 is air-stable but thermally sensitive and decomposes at room temperature. The structure was elucidated by X-ray analysis [10]. 

In solvent extraction with TBP, the fluoride complexes form solvated complexes with TBP. The stabilities of such complexes depend on the acidity/concentration of hydrofluoric... 

At high acidities, niobium is present as fluoroniobic acid, and this forms a solvation complex given by the reaction ... 

On warming, or on treatment with ether, the solvated complex give a black pyrophoric material of unknown constitution. 

Davies, J. A. et al., J. Chem. Soc., Dalton Trans., 1980, 2246-2249 Extremely sensitive to thermal and mechanical shock, occasionally detonating spontaneously without external stimulus, it should only be prepared and used in solution. The solid is an extreme hazard, and the acetone-solvated complex is also explosive. 

The development of more benign alternatives to cyanide for gold-leaching (see Section 9.17.3.1) such as thiourea, thiocyanate, or thiosulfate, which form stable complexes in water has prompted research to identify suitable solvent extractants from these media. Cyanex 301, 302, 272, Ionquest 801, LIX 26, MEHPA, DEHPA, Alamine 300 (Table 5) have been evaluated as extractants for gold or silver from acidic thiourea solutions.347 Whilst the efficacy of Cyanex 301 and 302 was unaffected by the presence of thiourea in the aqueous feed, the loading of the other extractants is severely depressed. Formation of solvated complexes of gold and of an inner-sphere complex of silver has been proposed.347... 

Figure 38 The structure of the dimeric solvated complex [( 5-Cp)Mg(/i2-SBut)(THF)]2 72.

From the method of preparation of [BeCl(12-crown-4)]+ (179), it is known that the Cl ligand can be substituted by a solvent molecule. We applied our most common test solvents water and NH3 to a Be2+ cation, where most coordination sites are occupied by a chelating ligand, in this case the crown ether 12-crown-4. In contrast to the tetrahedral [Be(solvent)4]2+ solvated complexes, the precursor complexes [Be(solvent)(12-crown-4)]2+ are quadratic pyramidal, where four oxygen donor atoms of the crown ether form the quadratic basis, while Cl- or a coordinating solvent molecule occupies the apical position. Addition of one water or ammonia molecule to [Be(12-crown-4)]2+ is exothermic (see Table IX). 

Butyne-l,4-diol has been hydrogenated to the 2-butene-diol (97), mesityl oxide to methylisobutylketone (98), and epoxides to alcohols (98a). The rhodium complex and a related solvated complex, RhCl(solvent)(dppb), where dppb = l,4-bis(diphenylphosphino)butane, have been used to hydrogenate the ketone group in pyruvates to give lactates (99) [Eq. (15)], and in situ catalysts formed from rhodium(I) precursors with phosphines can also catalyze the hydrogenation of the imine bond in Schiff bases (100) (see also Section III,A,3). 

Netropsin in Solution AGC (kcal/mol) Netropsin in Solvated Complex AGd (kcal/mol) ... 

By using EXSY measurements, it was shown that at 323 K there is only intramolecular exchange, whereas at 348 K intermolecular exchange also occurs via complete dissociation of the complex, producing a free substrate and a solvate complex (Fig. 11.9). 

Fig. 31.2 Typically (DIPAMP, CHIRAPHOS), the intramolecular exchange of Re and Si complexes is several times faster than the dissociation to reform the solvate complex.

The status quo provided by the early mechanistic studies described above was incomplete in several respects. Although the affinity of the solvate complex for dihydrogen was known to be low, the addition product remained uncharacterized. Likewise, the putative H2 addition intermediate between the enamide complex and the transient, but observable, alkylhydride had not been characterized. 

Solvation of the lithio cation of the silylated reagents by HMPA leads to solvent-separated ion pairs (Eq. 9.5). Titration experiments indicate coordination by four HMPA molecules. These solvated complexes, including the TBS derivative, exist entirely as the propargyl structures, emphasizing the importance of the silyl group to charge stabilization. 

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