RESEARCH PROJECTS

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I have TWO independent research projects. The one listed on this page deals with applying ORGANOMETALLIC/METALLOCENE complexes towards degrading toxic organophosphate compounds. Click here if you're interested in how metallocenes are used to make polymer. I have another research project on RNA ENZYMES, go to this site if you're interested in the RNA WORLD.

Over the eight years I have had over 14 undergraduate Lewis & Clark students help me with these research projects; their contribution to this ongoing reseach effort is gratefully thanked. I wish to recognize them here at this link.

Why are we interested in studying phosphate hydrolysis in the first place as a research project?

Here are some published work done at Lewis & Clark where we used an organometallic compound to carry out phosphate hydrolysis in water. This is the first known case of an organometallic compound that does this type of chemistry. The compound is called bis(cyclopentadienyl)molybdenum(IV) dichloride-Cp₂MoCl₂ for short. This compound belongs to a class of compounds called metallocene dihalides which have found wide application in polymer syntheses. Part I shows some of our beginning work with this compound.

Phosphate Hydrolysis by Cp₂MoCl₂ done about two years ago is shown here in Part II

We have even made several derivatives of the metal complex to promote phosphate hydrolysis, but none of them are better than the parent compound called Cp₂MoCl₂ when you look at the rate constants for phosphate hydrolysis

We propose the following intramolecular mechanism for this phosphate hydrolysis and it has to do with the unique properties of the Cp₂MoCl₂ molecule...the small Cl-Mo-Cl bite angle.

However, our most recent work has been on promoting the phosphate hydrolysis of phosphate esters such as the ones found in the pesticides, parathion and paraoxon. Parathion and paraoxon are neurotoxins and they are related to the notorious sarin and VX neurotoxins albeit a lot less lethal. Here are some toxicity comparisons.

We use nuclear magnetic resonance to look at the degradation (hydrolysis) of parathion and paraoxon. You can see that they degrade to form different products when treated with Cp₂MoCl₂ in water. Parathion hydrolysis by Cp₂MoCl₂ forms ethanol as the leaving group, and paraoxon hydrolysis forms diethylphosphate; p-nitrophenol is the leaving in this case. Check out the proton NMR spectra for both of these hydroytic reactions.

The hydrolysis products for parathion were rather unexpected, for they involve breaking the C-O bond of the phoshate ester when Cp₂MoCl₂ is present. Most phosphate hydrolytic reactions proceed through P-O bond cleavage. We used carbon-13 NMR in conjunction with oxygen-18 enriched water to show this rather novel mechanism of phosphate hydrolysis.

So what are the possible mechanisms for parathion and paraoxon hydrolysis by Cp₂MoCl₂? Below is a schematic for the proposed mechanism based on the products formed. In addition, we see about a 3,000-fold rate acceleration for these pesticide hydrolysis in the presence of Cp₂MoCl₂.