Rational Design of Catalysts: New Concepts from the Activation Strain Model

The aim of this work is to understand [1] the factors that determine the activity and selectivity of transition-metal catalysts in oxidative-addition steps that occur in bond activation and cross-coupling reactions. We studied the effect of varying the metal M along the d¹⁰ metals of groups 9, 10 and 11, in combination with varying the number as well as the type of ligands, using relativistic density functional theory (DFT) [2] and the activation strain model (ASM) [1].

Figure 1. Schematic illustration of concepts presented in this lecture.

 Three concepts for tuning a catalyst’s activity emerge: (i) d-regime catalysts; (ii) s-regime catalysts; and (iii) bite-angle flexibility (see Figure 1, left). These concepts explain why the effect of one and the same ligand on a catalyst’s activity can be completely different, even opposite, for catalysts from different electronic regimes. Furthermore, I will point out why not the bite angle itself, but its flexibility is decisive for the catalyst’s activity. Finally, I show how the latter is influenced not only by steric repulsion but also by what we designate “steric attraction” (see Figure 1, right).

 References:

[1]    (a) I. Fernandez, F. M. Bickelhaupt, Chem. Soc. Rev. 2014, 43, 4953-4967; (b) F. M. Bickelhaupt, J. Comput. Chem. 1999, 20, 114-128.

[2]    (a) G. te Velde, F. M. Bickelhaupt, E. J. Baerends, C. Fonseca Guerra, S. J. A. van Gisbergen, J. G. Snijders, T. Ziegler, J. Comput. Chem. 2001, 22 931-967; (b) F. M. Bickelhaupt, E. J. Baerends, In: Reviews in Computational Chemistry; K. B. Lipkowitz and D. B. Boyd, Eds.; Wiley-VCH: New York, 2000, Vol. 15, pp. 1-86; (c) C. Fonseca Guerra, J.-W. Handgraaf, E. J. Baerends, F. M. Bickelhaupt, J. Comput. Chem. 2004, 25, 189-210.