Homogeneous Metal Catalysts on a Support

Gerard van Koten and Bert Klein Gebbink

Debye Institute for Nanomaterials Science, Organic Chemistry and Catalysis, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands

g.vankoten@uu.nl

In this lecture various types of supported catalysts developed in our laboratories will be discussed. Initially we explored the use of carbosilane dendrimers as chemically inert supports with pincer-metal catalysts attached to their periphery.¹ We made also use of supports which had very rigid core-shell structures.² The synthesis of these soluble supports with up to twelve catalytic sites at their periphery required only a few steps. They have sizes amounting to 3.5nm. Experiments showed that these catalysts can be used in a continuous manner applying a membrane reactor (with Prof. D. Vogt, Eindhoven University) without detectable metal or ligand leaching.²

Most recent studies concentrate on the application of pincer-metal catalysts immobilized onto nanosize supports via non-covalent interactions.³ In this way a number of catalytic species become linked to the support in an one-step procedure. This support can provide new properties to the catalyst, e.g. making it water-soluble or putting the catalytic sites in a chiral surrounding.⁵

Finally, the partial, directed inhibition of a lipase with one ruthenium catalyst (see X-ray)⁴ will be discussed that produces a hybrid racemization/enantioselective acylation catalytic material for the kinetic resolution of racemic alcohols.

Proof-of-principle of some of these approaches will be discussed and will be put in the perspective of closing the gap between homogeneous and heterogeneous catalysis and the possibility to compartimentalize homogeneous catalysts in a multicomponent catalyst system.

1. Acc. Chem. Res., 2002, 35, 798-810, Nature, 1994, 372, 659

2. J. Org. Chem., 2003, 68, 675-685 ; Adv. Synth. Catal., 2003, 345, 364-369

3. J.Amer.Chem.Soc, 2006, 128, 12700-12713 ; Eur.J.Org. Chem., 2007, 2931-2939.