Comparing Frustrated Lewis Pair Chemistry to Metal-Ligand Cooperativity

The discovery of main-group systems, such as frustrated Lewis pairs (FLPs), possessing a lone pair of electrons and a vacant orbital have shown to be able to activate small molecules [1]. This too holds for metal-ligand... [ view full abstract ]

The discovery of main-group systems, such as frustrated Lewis pairs (FLPs), possessing a lone pair of electrons and a vacant orbital have shown to be able to activate small molecules [1]. This too holds for metal-ligand cooperativity (MLC), where both the metal and ligand are involved in bond activation processes [2]. A typical MLC system consists of a pincer-type tridentate PNP ligand with a Lewis basic site located in the ligand and a Lewis acidic metal centre (see Figure 1).

Pivotal to FLP chemistry is the prevention of Lewis adduct formation, which is accomplished by using sterically encumbered Lewis acidic and basic sites. Sterically unencumbered FLPs are able to dimerize, which leads to mutual quenching (Figure 2, left). We recently discovered that when MLC systems also contain sterically unencumbered groups, they dimerize thereby reducing their activity in stoichiometric and catalytic processes (Figure 2, right).

In this presentation, we fully delineate the similarities and differences between various FLP and MLC systems using experimental and theoretical means. By doing so, guiding principles can be formulated for cooperative Lewis acid/base chemistry and catalysis.

[1] D. W. Stephan, G. Erker Angew. Chem. Int. Ed. 2015, 54, 6400-6441. [2] C. Gunanathan, Y. Ben-David, D. Milstein, Science 2007, 317, 790-792. 

Email: e.r.m.habraken@uva.nl; j.c.slootweg@uva.nl