Page 109 - Academic Press Encyclopedia of Physical Science and Technology 3rd Organic Chemistry

P1: FPP Revised Pages Qu: 00, 00, 00, 00
Encyclopedia of Physical Science and Technology EN002C-85 May 17, 2001 20:35

Catalysis, Homogeneous

Piet W.N.M. van Leeuwen
University of Amsterdam

I. Definition and Scope of Homogeneous Catalysis
II. Elementary Steps for Homogeneous Catalysis
III. Description and Mechanisms of Homogeneous
Catalytic Processes

GLOSSARY Polymerization Coupling of many molecules (mono-
mers) forming a polymer (macromolecule).
Coordination compound Molecule or ion comprising a Reductive elimination (Reverse of oxidative addition.)
metal atom or ion surrounded by ions or molecules Loss of one or two ligands from a metal complex by
called ligands. reduction of the metal.
Coordination number Number of ligand atoms bonded
to the metal atom or ion in a coordination compound.
Electrophile Refers to the reactivity of an atom, ion, or THE PHENOMENON CATALYSIS has become well
molecule; an electron-deficient species ready to accept known owing to the use of catalysts in automobile ex-
an electron pair from another species thus forming a hausts, which ensure the complete conversion of the last
chemical bond. traces of fuel and decompose the toxic nitrogen oxides and
Enantiospecificity Preference for the formation of a sin- carbon monoxide to nitrogen and carbon dioxide. Cata-
gle enantiomer of a compound. lysts are substances that enhance chemical reactions that
Metal complex See Coordination compound. are not themselves consumed in the reactions. Exhaust cat-
Migratory insertion Insertion of an unsaturated mole- alysts are heterogeneous, as the catalyst is a solid material
cule such as ethene or CO (Y) into a metal–X bond, while the reactants are in the gaseous phase. In this article
whereby X migrates to one of the atoms of the unsatu- we are concerned with homogeneous catalysts, that is to
ratedmoleculecoordinatedtothemetalgivingM–Y–X. say that catalyst and reactant are molecularly dispersed in
Nucleophile Refers to the reactivity of an atom, ion, or the same phase, often the liquid phase. Homogeneous cat-
molecule; an electron-rich species ready to donate an alysts for the gas phase are also known and a well-known
electron pair to another species thus forming a chemical example is the chlorine atom catalyzing the decomposi-
bond. tion of ozone in our stratosphere. Here we will focus on
Oligomerization Coupling of several molecules of the metal catalysts in solution that have found widespread uti-
same kind forming a larger unit (oligomer). lization in chemical industry for the manufacture of bulk
Oxidative addition Oxidation of a metal compound ac- chemicals, fine chemicals, and pharmaceuticals and in or-
companied by an increase of the coordination number. ganic synthesis in the laboratory. The catalysts presented

457