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Chapter 1: Introduction

A personal look at the history of aqueous organometallic catalysis “Organometallic chemistry deals with moisture sensitive compounds therefore all manipulations should be carried out under strictly anhydrous conditions” – this was the rule of thumb ever since the preparation of the first organometallic compounds. Not as if there were no isolated examples of water-stable organometallics from the very beginning, in fact Zeise`s salt, was prepared as early as 1827. Nevertheless, it is true, that compounds having highly polarized M-C, M-H etc. bonds may be easily decomposed in water by protonation. In other cases, oxidative addition of or oxygen abstraction from. | Chapter 1 Introduction 1.1 A personal look at the history of aqueous organometallic catalysis Organometallic chemistry deals with moisture sensitive compounds therefore all manipulations should be carried out under strictly anhydrous conditions - this was the rule of thumb ever since the preparation of the first organometallic compounds. Not as if there were no isolated examples of water-stable organometallics from the very beginning in fact Zeise s salt PtCl3 C2H4 was prepared as early as 1827. Nevertheless it is true that compounds having highly polarized M-C M-H etc. bonds may be easily decomposed in water by protonation. In other cases oxidative addition of or oxygen abstraction from water leads to formation of metal hydroxides or oxides i.e. the redox stability of water may not be sufficient to dissolve without deterioration a compound having a highly reduced metal center. Still there are the procedures for preparation of important compounds such as e.g. HRh PPh3 4 which call for washing the products with water in order to remove inorganics - these compounds cannot be highly sensitive to water. Nowadays we look with other eyes at organometallic compounds the family of which has expanded enormously. Some members of this family are soluble in water due to their ionic nature the legions of anionic carbonylmetallates e.g. Ni CN CO 3 and cationic bisphosphine Rh-chelate complexes e.g. Rh BDPP COD just come to mind. Others obtain their solubility in water from the well soluble ligands they contain these can be ionic sulfonate carboxylate phosphonate ammonium phosphonium etc. derivatives or neutral such as the ligands with polyoxyethylene chains or with a modified urotropin structure. 1 2 Chapter 1 One of the most important metal complex catalyzed processes is the hydroformylation of light alkenes. In the early years the catalyst was based on cobalt and this brought about an intense research into the chemistry of cobalt carbonyls. A key intermediate CoH CO 4 is well