Complexes in solution

Champmartin D and Rubini P 1996 Determination of the 0-17 quadrupolar coupling constant and of the C-13 chemical shielding tensor anisotropy of the CO groups of pentane-2,4-dione and beta-diketonate complexes in solution. NMR relaxation study/norg. Chem. 35 179-83... 

A concise summary of chemistry of technologically important reactions catalysed by organometallic complexes in solution. Cornils B and Herrmann W A (eds) 1996 Applied Homogeneous Catalysis with Organometallio Compounds (Weinheim VCH) A two-volume, multiauthored account with emphasis on industrial applications. 

How ever, the Mn(II) ion forms a variety of complexes in solution, some of which may be more easily oxidised these complexes can be either tetrahedral, for example [MnClJ , or octahedral, for example [Mn(CN)f,] Addition of ammonia to an aqueous solution of a manganese(II) salt precipitates Mn(OH)2 reaction of ammonia with anhydrous manganese(II) salts can yield the ion [MnfNH y T... 

Equilibria in Solution The stability of a protein-ligand complex in solution is measured in terms of the equilibrium constant and the standard free energy of association based on it. For association of species P and L in solution to form a complex PL, i.e., for... 

The formation of such materials may be monitored by several techniques. One of the most useful methods is and C-nmr spectroscopy where stable complexes in solution may give rise to characteristic shifts of signals relative to the uncomplexed species (43). Solution nmr spectroscopy has also been used to detect the presence of soHd inclusion compound (after dissolution) and to determine composition (host guest ratio) of the material. Infrared spectroscopy (126) and combustion analysis are further methods to study inclusion formation. For general screening purposes of soHd inclusion stmctures, the x-ray powder diffraction method is suitable (123). However, if detailed stmctures are requited, the single crystal x-ray diffraction method (127) has to be used. 

The phenomenon of dye aggregation was discovered in the 1930s (52,53). Polymethine dyes were found to form molecular complexes in solution or on certain crystal surfaces. Molecules within aggregates are bound together by nonvalence bonds, ie, resonance interactions exist between them. 

Metha.no Ca.rbonyla.tion, An important industrial process cataly2ed by rhodium complexes in solution is methanol carbonylation to give acetic acid. 

The selective oxidation is catalyzed by silver, which is the only good catalyst. Other olefins are not converted selectively to the epoxides in the presence of silver. However, propylene epoxidation is appHed commercially the catalysts are either molybdenum complexes in solution or soHd Ti02—Si02 (see... 

In both cases n is the number of hydrogen ions displaced in the formation of the complex. In solutions where the ratio of free chelating agent to complex, ], is held constant, the slopes of the curves pM vs pH are equal. o n m. the region where H A is the principal form of the chelating... 

Studies on metal-pyrazole complexes in solution are few. The enthalpy and entropy of association of Co(II), Ni(II), Cu(II) and Zn(II) with pyrazole in aqueous solution have been determined by direct calorimetry (81MI40406). The nature of the nitrogen atom, pyridinic or pyrrolic, involved in the coordination with the metal cannot be determined from the available thermodynamic data. However, other experiments in solution (Section 4.04.1.3.3(i)) prove conclusively that only the N-2 atom has coordinating capabilities. 

In the complex system containing APA (AdPA), La(III), and dye (either Ars-I or XO), strong adsorption of dye and La occurs at pH 6-8. Analysis of UV-Vis of prepared solids shows formation of MLC. Their composition, UV-Vis adsorption maxima ()i, mn) and the shifts relatively to the monoligand La-dye complexes in solution (A)i, mn) are shown in the table below. Ars-III was unsuitable for MLC, as it strongly complexes with La at pH=2-5 and desorbs it from surface of AdPA- and APA-silica. 

The electron transfer rates in biological systems differ from those between small transition metal complexes in solution because the electron transfer is generally long-range, often greater than 10 A [1]. For long-range transfer (the nonadiabatic limit), the rate constant is... 

Many biochemical and biophysical studies of CAP-DNA complexes in solution have demonstrated that CAP induces a sharp bend in DNA upon binding. This was confirmed when the group of Thomas Steitz at Yale University determined the crystal structure of cyclic AMP-DNA complex to 3 A resolution. The CAP molecule comprises two identical polypeptide chains of 209 amino acid residues (Figure 8.24). Each chain is folded into two domains that have separate functions (Figure 8.24b). The larger N-terminal domain binds the allosteric effector molecule, cyclic AMP, and provides all the subunit interactions that form the dimer. The C-terminal domain contains the helix-tum-helix motif that binds DNA. 

A chiral titanium complex with 3-cinnamoyl-l,3-oxazolidin-2-one was isolated by Jagensen et al. from a mixture of TiCl 2(0-i-Pr)2 with (2R,31 )-2,3-0-isopropyli-dene-l,l,4,4-tetraphenyl-l,2,3,4-butanetetrol, which is an isopropylidene acetal analog of Narasaka s TADDOL [48]. The structure of this complex was determined by X-ray structure analysis. It has the isopropylidene diol and the cinnamoyloxazolidi-none in the equatorial plane, with the two chloride ligands in apical (trans) position as depicted in the structure A, It seems from this structure that a pseudo-axial phenyl group of the chiral ligand seems to block one face of the coordinated cinnamoyloxazolidinone. On the other hand, after an NMR study of the complex in solution, Di Mare et al, and Seebach et al, reported that the above trans di-chloro complex A is a major component in the solution but went on to propose another minor complex B, with the two chlorides cis to each other, as the most reactive intermediate in this chiral titanium-catalyzed reaction [41b, 49], It has not yet been clearly confirmed whether or not the trans and/or the cis complex are real reactive intermediates (Scheme 1.60). 

The process of separating the intermediate products from the purified solutions, in the form of solid complex fluoride salts or hydroxides, is also related to the behavior of tantalum and niobium complexes in solutions of different compositions. The precipitation of complex fluoride compounds must be performed under conditions that prevent hydrolysis, whereas the precipitation of hydroxides is intended to be performed along with hydrolysis in order to reduce contamination of the oxide material by fluorine. 

The dissociation of coordinatively sufficient organometallic complexes in solution. For instance, for the system based on cyclopentadienyl complexes of titanium the active centers of catalytic polymerization (C Hj) -TiR]+ are caused by the following process (178, 179) ... 

The past fifteen years have seen evidence of great interest in homogeneous catalysis, particularly by transition metal complexes in solution predictions were made that many heterogeneous processes would be replaced by more efficient homogeneous ones. There are two motives in these changes—first, intellectual curiosity and the belief that we can define the active center with... 

It is believed [1135,1136] that the decomposition of metal complexes of salicyaldoxime and related ligands is not initiated by scission of the coordination bond M—L, but by cleavage of another bond (L—L) in the chelate ring which has been weakened on M—L bond formation. Decomposition temperatures and values of E, measured by several non-isothermal methods were obtained for the compounds M(L—L)2 where M = Cu(II), Ni(II) or Co(II) and (L—L) = salicylaldoxime. There was parallel behaviour between the thermal stability of the solid and of the complex in solution, i.e. Co < Ni < Cu. A similar parallel did not occur when (L—L) = 2-indolecarboxylic acid, and reasons for the difference are discussed... 

Reactions and catalytic properties of rhodium complexes in solution. B. R. James, Coord. Chem. Rev., 1966, 1,505-524 (160). 

X-ray diffraction studies on the structures of metal complexes in solution. H. Ohtaki, Rev. Inorg. Chem., 1982,4,103-177 (223). 

Luminscence kinetics of metal complexes in solution, T, J, Kemp, Prog. React. Kinet., 1981, 10, 301-398 (256). 

Application of molecular orbital theory to electron transfer reactions of metal complexes in solution. J. K. Burdett, Comments Inorg. Chem., 1981,1, 85-103 (7). 

Thermodynamics of the formation of outer-sphere complexes in solution. V. E. Mironov and A. K. Pyartman, Russ. Chem. Rev. (Engl. Transl), 1983, 52, 837-849(144). 

STRATEGY First, we write the chemical equation for the equilibrium between the solid solute and the complex in solution as the sum of the equations for the solubility and complex formation equilibria. The equilibrium constant for the overall equilibrium is therefore the product of the equilibrium constants for the two processes. Then, we set up an equilibrium table and solve for the equilibrium concentrations of ions in solution. 

Structures with a cyclic character (70° a 110°) are less solvated than open cation structures (a < 70° a > 110°) due to a larger charge delocalization in the former. Thus, the alterations of the potential energy surface described above are plausible. There are two possible structures for activated complexes in solution. They... 

C, which leads to a break in the pressure-composition curve at BF3 Ir = 2 1. The formation of the 1 1 complex in solution is indicated by titrations. Insertion of InCl into the Fe—Fe bond in boiling dioxane yields [T7 -C CO)2Fe]2lnCl in 55% yield. The only group-VIIA compound that forms an addition compound with a group-lIIB halide, namely with BF3, is [(i7 -Cp)2ReH]The formation of (t -Cp),ReH BF3 is established when (T7 -Cp),ReH is titrated tensimetrically in toluene with BF3 at 0°C. 

Structure of Complexes in Solution Derived from X-Ray Diffraction Measurements Georg Johansson... 

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