Research

Paramagnetic transition metal complexes are believed to be the active species in many catalytic and stoichiometric reactions. In general, their very high reactivity prevents their isolation or even their observation except under the most severe conditions (e.g. in frozen inert gas matrices). Thus, information on them is limited.

One area of research for our group involves the synthesis of model complexes for these systems by replacing small ligands with larger ones to prevent the product radicals from reacting in ways that prevent their isolation.  For example, we frequently employ the C5Ph5 ligand in the place of the smaller C5H5 ligand in complexes.  In the past, we have prepared (C5Ph5)Cr(CO)3 and have examined its reactivity.  A number of derivatives of this compound (e.g. (C5Ph5)Cr(CO)2(PMe3)) have been prepared and characterized.  Some (e.g. [(C5Ph5)CrCl2]2) show interesting chemistry in their own rite and are currently being examined.

Another, newer area is taking advantage of a property of paramagnetic compounds.  Rotating an electrical field (e.g. an unpaired electron) gives rise to a magnetic field.  (The reverse process, rotating a magnetic field, is how electric power generators work.)  Thus, paramagnetic compounds can exhibit magnetism because of their unpaired electrons.  In collaboration with Prof. Gordon Yee of Virginia Tech, we have begun to prepare series of ionic charge-transfer salts (e.g. [(C5Me4Et)2Fe][TCNE]).  More detail about this work can be found at his website.

The products of these reactions are characterized by a range of techniques including IR, NMR, and ESR spectroscopies, X-ray crystallography, electrochemistry, and magnetic susceptibility.  In some cases, these reactions may proceed by interesting pathways and, where applicable, electrochemical and spectroscopic studies will be performed to elucidate these mechanisms.

Movable, 3-D images of some of the molecules we have made appear below.  Full page images can be seen by clicking on the links below the images.  To move the images, simply hold the left mouse button down and drag the cursor across the screen.  The image will turn as the cursor moves.  To change the appearance of the image, hold the right mouse button down and a menu will appear.
 
 

Images may be manipulated using the mouse.  X-ray crystal structures were obtained by Prof. Arnold Rheingold and his group at the University of California at San Diego.

(C5Ph5)Cr(CO)3 (C5Ph5)Cr(CO)2(PMe3) [(C5Ph5)CrCl2]2
(C5Ph5)Fe(CO)2– (C5Ph4H)2Rh  [(C5Me4Et)2Fe][TCNE]

Full screen images may be obtained by clicking on the link below the picture.