Tailoring Catalytic Selectivity By Enzyme-Inspired Confinement

Prof. Dr. Michael R. Buchmeiser, Universität Stuttgart

Reactions under steric confinement by well-defined organometallic catalysts selectively immobilized inside tailored mesoporous materials with pore diameters < 6 nm mimic enzymes and benefit from the proximity of the catalyst to a pore wall with defined geometry and polarity. This allows governing the transition states of catalytic reactions, thereby offering access to tailored stereo- and chemoselectivity. This concept was successfully applied to the size-specific macrocyclization of a, w-dienes by tethered and surface-bound neutral Ru- and cationic Mo- and W-imido alkylidene N-heterocyclic carbene (NHC) complexes, in Z-selective ring-opening cross-metathesis reactions, in Z-selective hydrosilylation and hydroboration reactions of alkynes by Rh(I) NHC complexes, in the alkene-selective oligomerization of ethylene with Cr(II) and Cr(III) complexes as well as in the stereospecific ring-expansion metathesis polymerization (REMP) with cationic molybdenum alkylidyne NHC complexes to yield cyclic low-molecular weight, low-Đ polymers. Complementary, the concept of liquid confinement in biphasic supported ionic liquid-liquid phase (SILLP) catalysis, in which confinement is created by a thin (1 nm) liquid layer as well as under solid catalyst ionic liquid layer (SCILL) conditions and their role in Z-selective alkyne hydrosilylation reactions together with the role of the mesoporous support will be outlined