Professor Karen Goldberg, University of Washington.

Department of Chemistry

Visiting Speaker

Professor Karen Goldberg, University of Washington.

Seattle, WA, USA

E-mail: goldberg@chem.washington.edu

"Reactions of Late Transition Metal Complexes with Molecular Oxygen".

Abstract:

From environmental and economic standpoints, molecular oxygen represents

an ideal oxidant for large-scale chemical transformations. It is readily available,

inexpensive (particularly if used without separation from air) and environmentally

benign. However, widespread use of molecular oxygen as an oxidant in homogeneous

catalysis has been limited, with more expensive and/or hazardous oxidants often

employed. Further understanding of how transition metal complexes react with

molecular oxygen will assist in efforts to develop new selective homogeneous

catalytic reactions that effectively utilize this abundant and environmentally friendly

oxidant.

One valuable potential use of oxygen as an oxidant would be in selective

alkane functionalization. A variety of late transition metal complexes have been

shown to activate alkane C-H bonds to generate metal alkyl and alkyl hydride

complexes. To accomplish alkane functionalization, such late metal species need to

undergo further reaction. If oxygen is to be used as an oxidant, the reactivity of these

species with oxygen needs to be understood. With this goal in mind, a variety of late

transition metal alkyls, hydrides and alkyl hydride complexes were exposed to

molecular oxygen. Reactions including the insertion of oxygen into metal-hydride

bonds to form metal-hydroperoxides, the insertion of oxygen into metal-alkyl bonds

to form metal-alkylperoxides and oxygen-induced reductive elimination have been

observed. Kinetic and mechanistic studies of these oxygen reactions have been carried

out and will be discussed. Both radical chain and non-radical chain mechanisms were

documented. The radical chain mechanisms identified in these late metal systems will

be compared to those typically found for organic autoxidations and to those that have

been proposed for autoxidations of main group and early transition metal alkyl

complexes.

Friday, November 6, 2009 at 3:00 p.m.  ST 143

Department Contact: Tracy Lohr (Grad)