Ligand generation

This regioselectivity is opposite to the one observed by the non-catalysed additions of BH3 THF or 9-BBN to the same alkene, or those catalysed by Rh and Ir catalysts. Chiral NHC ligands (generated from 84) on Cu under the same conditions proceed with high enantioselectivity (enantiomeric ratio 99 1) [71] (Scheme 2.12). 

Compound 1 (Fig. 18.18) reversibly forms an analogous ferric-superoxo/Cu adduct at 60 °C, as demonstrated by resonance Raman spectroscopy. However, warming the sample to 40 °C results in a rapid four-electron reduction of the bound O2 ligand, generating a ferryl/Cu /phenoxyl radical derivative (Fig. 18.18) [Collman et al., 2007a]. 

Entries 1-3 were run in toluene and entries 4—6 were run in THF with three different Mo catalyst sources. The activation time was longer when Mo(CO)6 was used, but the results were dependent on the solvent not the catalyst source. Thus, it was confirmed that Mo(CO)s with the chiral ligand generated the same active catalyst as Trost reported. 

The complex was synthesized using the so-called in situ benzoate ligand generation from benzaldehyde [62], The centrosymmetrical complex, formulated Con2(PhCOO)4(Me3TTF-CH=CH-py)2, is shown in Fig. 12. 

Methods for the enantioselective synthesis of 3-substituted indolines by means of the asymmetric intramolecular carbolithiation of 2-bromo-A,-allylanilines in the presence of (-)-sparteine were reported simultaneously by Bailey <00JA6787> and Groth <00JA6789>. Thus, addition of 89 to 2.2 equiv of /BuLi in the presence of the chiral ligand generates the lithium intermediate 90 which upon quenching with methanol affords the chiral indoline 91 in a process that is highly solvent dependent. 

De novo design of enzyme inhibitors by Monte Carlo ligand generation, J. Med. Chem. 38 466 (1995). 

Reaction of the heterocubane cluster 14 (R = Ph) with (Cp Rhl2)2, a reagent that functions both as a Lewis acid (the metal center) and a Lewis base (the iodide ligands), generates the dirhodium complex 18. Complex 14 also adds to l,l-bis(diphenylphosphinoferrocene) to form the cyclic species 19.8... 

Proton transfer to negatively charged hydrogen atoms has attracted the attention of many chemists over the last two decades. This process plays an important role in many chemical and biochemical phenomena that occnr in the gas phase, in solution, and in the solid state [1-3], For example, direct proton attack on hydride ligands generates transition metal dihydrogen complexes which are then involved in various catalytic transformations [4] ... 

This mechanism implies that OH" acts as a base rather than a nucleophile, and removes a proton from a coordinated am(m)ine ligand, generating the rate-determining amido conjugate base. Also implicit is a... 

The coordination chemistry of macrocyclic ligands has been extensively studied and aspects of isomerism have been considered in numerous systems.241 Methods whereby two diastereomers of complexes of tetra- N-methylcyclam may be isolated have been discussed previously.184 This, however, is a relatively simple system and it is usually necessary to consider isomerism due to the presence of asymmetric atoms in the chelate arms, as well as that due to asymmetric donor atoms that may be rendered stable to inversion by coordination. An example of a system exhibiting this level of complexity is afforded by the nickel(II) complexes of the macrocyclic ligands generated by reduction of the readily prepared macrocycle (46). These ligands contain two asymmetric carbon atoms and four asymmetric nitrogen atoms but, because AT-inversion is rapid, it is conventional to consider that only three separable stereoisomers exist. There is an enantiomeric pair, (47a) and (47b), which constitutes the racemic isomer (R, R ), and an achiral (R, S ) diastereomer (47c), the meso isomer. 

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