Complex, precursor

The selectivity for (/ ,/ )( ,S)-10 has been rationalized by invoking a synperiplanar enolate species whose conformation is enforced by a donor(enolate oxygen)- acceptor) peril uo-rophenyl) interaction depicted in structure N47. Infrared and variable temperature NMR spectroscopic studies of the neutral precursor complex 8 support the existence of such a donor-acceptor interaction. 

A number of metal complexes with disulfurmonoxide as a ligand have been prepared either by oxidation of precursor complexes containing the 2 hgand or by trapping S2O formally produced in situ from a suitable precursor by heating [52]. Such molecules are cyclic di-, tri-, or tetrasulfane monoxides or dioxides such as the one shown in Scheme 1. 

In the complex with two methylimidazol units one of them is N-coordinated and the other a C-coordinating carbene ligand. It seems that in the synthesis of this complex a homoleptic rearrangement of the QFs precursor complex is accompanied by a rapid migration of the proton nitrogen to the initially coordinated carbon. 

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. 

Au Nanoparticles stabilizffd by alkyl groups derived from the precursor complex... 

Extending the formalism for ET in homogeneous phase, reactions at liquid-liquid interfaces can be described in terms of a series of elementary steps initiated by the approach of reactants to the interfacial region and the formation of the ET precursor complex [1,5,60],... 

The voltammograms at the microhole-supported ITIES were analyzed using the Tomes criterion [34], which predicts ii3/4 — iii/4l = 56.4/n mV (where n is the number of electrons transferred and E- i and 1/4 refer to the three-quarter and one-quarter potentials, respectively) for a reversible ET reaction. An attempt was made to use the deviations from the reversible behavior to estimate kinetic parameters using the method previously developed for UMEs [21,27]. However, the shape of measured voltammograms was imperfect, and the slope of the semilogarithmic plot observed was much lower than expected from the theory. It was concluded that voltammetry at micro-ITIES is not suitable for ET kinetic measurements because of insufficient accuracy and repeatability [16]. Those experiments may have been affected by reactions involving the supporting electrolytes, ion transfers, and interfacial precipitation. It is also possible that the data was at variance with the Butler-Volmer model because the overall reaction rate was only weakly potential-dependent [35] and/or limited by the precursor complex formation at the interface [33b]. 

Thioethers lack the capacity to neutralize positive charge and display weak donor properties. Consequently, they do not readily displace strong donor solvents (water) or strongly bonding anions (such as halides) from the coordination sphere. As a consequence, many thioether complex syntheses employ aprotic or alcoholic solvents and precursor complexes with weakly bound solvents (such as DMSO or acetone) or anions (such as C+3S03 ). Despite the synthetic challenges, a wide range of complexes has been reported, particularly with the cyclic poly-thioethers, where the macrocyclic effect overcomes many of the above difficulties. 

Five-coordinate Ni111 complexes (89) have been prepared by oxidation of the square planar Ni11 precursor complexes [Ni(L)X] with either X2 or CuX2, and the crystal structure of the iodo derivative has been determined. The geometry at Ni is best described as square pyramidal, with the Ni atom displaced approximately 0.34 A out of the basal plane towards the apical I atom. EPR confirms the Ni111 oxidation state, in which the unpaired electron of the low-spin d1 system is situated in the dz2 orbital.308,309 In aqueous solution full dissociation of both X anions occurs, while in acetone solution dissociation is not significant. The redox couple [Nin NCN (H20)]+/ [Ni111 NCN (H20)ra]2+ in water is +0.14V (vs. SCE). 

The first examples of five-coordinate platinum(II) complexes of the type [Pt(PR3)L]2+ (L = tris(2-(diphenylphosphino)ethyl)phosphine R = Et, OMe, OEt) (104) containing only P-donor atoms have been prepared by the reaction of [PtClL]+ with an appropriate monodentate tertiary phosphine or phosphite ligand.284 Triaryl phosphines and phosphites do not react with the precursor complex, even at elevated temperatures, most probably due to the considerable steric interactions that would occur upon the approach of the P-donor ligand to the platinum(II) center. 

From the atomic to the macroscopic level chirality is a characteristic feature of biological systems and plays an important role in the interplay of structure and function. Originating from small chiral precursors complex macromolecules such as proteins or DNA have developed during evolution. On a supramolecular level chirality is expressed in molecular organization, e.g. in the secondary and tertiary structure of proteins, in membranes, cells or tissues. On a macroscopic level, it appears in the chirality of our hands or in the asymmetric arrangement of our organs, or in the helicity of snail shells. Nature usually displays a preference for one sense of chirality over the other. This leads to specific interactions called chiral recognition. 

The most practicable and easy-to-use precursor complex for the desired 14 electron intermediate... 

In related work, complexes 32 and 33 have been synthesized (41). The precursor complex in each preparation is the rhenaacetylacetonimine complex 25, where R = CH2CH2OH. This complex is formed by direct Schiff-base condensation with 2-aminoethanol. Complex 32 is formed when this precursor compound is treated with MeP(0)F2, and complex 33 is formed similarly by treatment with N,N -carbonyldiimidazole. The... 

In equation 11, two CO molecules have been inserted into the NN bond, which was the shortest bond in the precursor complex The overall transformation accomplished by treating azobenzene with (C Me,. -Sm(THF)2 and then CO is shown in equation 12. 

The synthesis of group 4 alkoxide complexes grafted on the surface of silica illustrates this approach.44-47 Two routes were considered, which are schematically represented in Equations(2) and (3) they differ in the nature of the precursor complex, which is either the tetra-alkoxide M(OR)4 (Equation(2)), or the tetra-alkyl complex MR4, M = Ti, Zr, Hf (Equation(3)) ... 

The more hindered alkoxide Ti(OiPr)4 was used as the precursor complex with surface silanols of an amorphous silica support this reaction is reported to lead to the same environment of Ti as in TS-1, but only when the reaction is carried in cyclohexanol as the solvent. Epoxidation of octene, cyclohexenol, and norbornene with FI202 in phenylethanol leads to 95-98% epoxide selectivity.147... 

Intramolecular adducts have also been used as gallium and indium precursor complexes they are synthesized by the alkylation of the group 13 metal trihalide with an appropriate Grignard reagent,89 as shown Figure 20. 

In two independent studies, InP was grown from the precursor complex [(CH3)2In /i-P(But)2 ]2.255 256 262 First, Cowley et al. employed the use of a cold-wall reactor to deposit InP using H2 or He as the carrier gas, with substrate temperatures between 450 °C and 700 °C. Using an MBE reactor, Bradley and co-workers found that stoichiometric growth was only possible at 480 °C and only when a simultaneous secondary incident flux of dissociated phosphine was added. Lower growth temperatures resulted in indium-rich deposits. 

The presence of Ga—C rr-bonds in many dimeric precursor complexes was found to affect the quality of the resultant films and the film growth rate in many cases films obtained from dimers were found to contain significant levels of carbon. Monomer species have also been investigated. 

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