Steric bite angle effect

In 2001, hybrid QM/MM strategies such as those in Section 3, provided a step forward in the modeling of real-world catalysts. However, the scope of these methods is also limited, because they only enable us to properly treat steric effects. Despite this drawback, some important aspects can be studied using these methods. Regioselectivity in diphosphine systems is explained by non-bonding interactions and bite angle effects. However, the role of ea complexes has not yet been determined. 

They constitute the first rhodium phosphine modified catalysts for such a selective linear hydroformylation of internal alkenes. The extraordinary high activity of 32 even places it among the most active diphosphines known. Since large steric differences in the catalyst complexes of these two ligands are not anticipated, the higher activity of 32 compared to 31 might be ascribed to very subtle bite angle effects or electronic characteristics of the phosphorus heterocycles. 

Bite angle effects in diphosphine metal catalysts Steric or electronic ... 

Freixa, Z. and van Leeuwen, P.W.N.M. (2003) Bite angle effects in diphosphine metal catalysts Steric or electronic Dalton Trans., 1890. 

Hydroformylation is also a model reaction system in homogeneous catalysis as it contains so many aspects such as ligand effects (electronic, steric, bite angle), in situ studies, complicated kinetics, and effects of conditions and impurities. All this, combined with its practical value, makes it an ideal topic in education. 

The results summarized in Figure 2 imply that the observed correlation between 8(103Rh) and catalytic activities for complexes 3 may be indirect rather than intrinsic. The activity is attributed to steric effects related to the bite angle which in turn affects the chemical shifts only indirectly via concomitant changes in the Rh-P bond lengths. 

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