# Presentation: 116369

## Probing the Reactivity of the Actinides Using Catalysis

- Goals:
- 	Determine Fundamental Chemistry of Transuranic (TRU) Elements
- 		• Simple, well-defined systems
- 		• Compare reactivity to well studied analogs
- Benjamin P. Warner
- Actinides, Catalysis, and Separations Science Group

## Outline:

- 	Why should we care about reactions of transuranic elements?
- 	What is involved in performing transuranic chemistry?
- 	Studies of metal-ligand coordination reactions
- 	Reactivity studies
- 	Combinatorial approach

## Plutonium and other actinides contact organic materials.

-    Processing: *Phosphates, Amides, Ketones, Ammonium Salts*
-    Waste Forms: *Carbohydrates, Halocarbons, Hydrocarbons, Siloxanes*
-    Health Effects: *Phosphates, Amides *(DM Taylor, *J. Alloys and Comp*. **271-273**, *1998*, 6-10.)

- ion exchange

- chelation

- combustibles

## Questions:

-      Plutonium radiolysis of water can generate 1 mol % H2O2 per day
-      Radiation damage is significant
- Chemical activity has been shown to be significant:
-      Claycamp and Luo, *Radiation Research*, **137**, *1994*, 114-117.
-        • Pu(III) is 4.8x more active than Fe(III) in catalyzing ascorbate oxidation by H2O2
-        • Pu(III) is comparable to Fe(III) in inducing DNA oxidative stress
-          (measured by 8-oxoguanine formation and thymine glycol formation)
*What is the reactivity of Pu ?*
*How can it be understood in relation to other elements ?*
*What are the chemical effects v. the radiological effects ?*

## Simple f-element compounds are known to be catalysts

_**R**_**	**** ****	****           **_** Yield (%)**_
- Ph		62		10
- 4-NO2C6H4	90		0
*c*-C6H11		68		13
- COOEt		36		41

- X.G. Fang, J.G. Watkin, B.P. Warner, *Tetrahedron Lett*. **41**, *2000*, 447-449.

## Simple f-element compounds are known to be catalysts

- X.G. Fang, J.G. Watkin, B.P. Warner, *Synthetic Communication*. **30**, *2000*, 2669-2676.

- LnCl3	PrCl3     GdCl3    DyCl3    ErCl3    LuCl3
- Yield (%)	   1           2           42	      54         62

- 86%
- 49%

- 79%
- 71%

## Simple f-element compounds are known to be catalysts

- Oxidation:
- Ph-Cl (10,000 ppm) 				Ph-Cl (31 ppm) + CO2
- GJ Hutchings, CS Heneghan, ID Hudson, SH Taylor, *Nature*, **384**, *1996*, 341-342.
- Hydrolysis:
- Catalyst = UO2(NO3)2, kcat/uncat=6700, pKa UO2(NO3)2 = 4.2-6.1
- RA Moss, K Bracken, J Zhang, *Chem. Comm.*, *1997*, 563-564.

- U3O8 / 350 °C

- catalyst

## Handling Plutonium: A Non-Trivial Exercise

-  Inert Atmosphere (He) Negative Pressure Glovebox
-  Liquid Nitrogen and Solvent Traps for Distillation Inside Box
-  Sample Removal Port for NMR Tubes
-  Spectroscopy Well for IR, UV-Vis
-  U_x0008_V-Vis Fiber Optic
-  Electrochemical Feeds
-  Chilling Block

## Ann Schake, Lonny Morgan, and an RCT remove organo-plutonium NMR samples.

## Preparation of Starting Materials

- An[N(SiMe3)2]  +  3.1  ArOH		    An(OAr)3     (Ar=2,6-tBu2Ph)

- hexane

- Other Starting Materials: Cs2PuCl6, ThCl4, UCl4

- LR Avens, SG Bott, DL Clark, AP Sattelberger, JG Watkin, BD Zwick *Inorg. Chem.*, **1994**, *33*, 2248.
- BD Zwick, AP Sattelberger, LR Avens, *Transuranium Organometallic Elements: The Next Generation*;
- 	American Chemical Society: Washington D. C., 1992, pp. 239-246.

## Self-Exchange Reactions: Associative Process

- Binding Affinities: Mirrors Process Data

- H≠	5.8 kCal/mol	3.8 kCal/mol	14.7 kCal/mol
- S≠	-22.5 eu		-26.4 eu		-2.3 eu
- G≠	11.9 kCal/mol	11.8 kCal/mol	15.5 kCal/mol
- Ka	      9		      214		     190

## IR Frequencies for bound and free ligands

- Red shift in the C=O or P=O frequency

- -free	1642 cm-1 	1192 cm-1 	1627 cm-1
- -bound	1580 cm-1 	1149 cm-1 	1564 cm-1
- -free	 62 cm-1 	 	 43 cm-1 	 	 63 cm-1

## Elucidating the “Anomalous Aryl Strengthening Effect”

- Determining Steric and Electronic Effects on Ligation

## Initial Examination of TRU Catalysis

- What analogies can be drawn between actinides, transition metals, lanthanides
- Cp*2U (IV) acts like group IV and/or lanthanides - Eisen, Marks, Doye, Bergman
- Uranium (VI) allows unique reactivity - Burns

- cat = Cp*2UMe2, Cp*2ThMe2,
- Cp2TiMe2, Cp’2SmR, Cp2Zr(NHAr)2

## An-Catalyzed Meerwein-Ponndorf-Verley Reduction

-  Pu(III) catalzes MPV and Tischenko Reactions - similar to Lanthanides

## Pu(III)-Catalyzed Meerwein-Ponndorf-Verley Reduction

## An-Catalyzed Meerwein-Ponndorf-Verley Reduction

-  Th(IV), U(IV) do not catalyze MPV - similar to Zr
-  U(III) does not catalyze MPV - U(III) is oxidized by *iso*-propanol and ketones
- 					(although UI2(iPrOH)4+ I-)
-  Np(III) does not catalyze MPV - Np(III) is oxidized by ketones, but not by *iso*-propanol
- 	U(III)/U(IV)	-.631 V
- 	Np(III)/Np(IV)	+.155 V	 	Np(III)/Np(V)	+.447
- 	Pu(III)/Pu(IV)	+.982 V

## Actinides Catalyze Ketone Hydrosilation...

- 		+ <4 iPrOH,

**Actinides Catalyze Ketone Hydrosilation...**

**...but the Catalyst is Difficult to Generate...**

**...****and Uranium is Still Oxidized.**

- Catalyst = 	Pu(N(SiMe3)2)3 + 3 iPrOH,
- 	An(N(SiMe3)2)2(N(SiMe2CH2)
- 		+ >4 iPrOH,

- U(N(SiMe3)2)3 + 3 iPrOH + ketone appears identical to U(N(SiMe3)2)2(N(SiMe2CH2) + 4 iPrOH + ketone

- An(N(SiMe3)2)2(N(SiMe2CH2) =

## Conclusions:

- 	Pu mediates catalytic reactions
- 	Pu(III) similar to Ln(III), An(IV) similar to Group IV
- 	Carbonyl ligands bind to Pu(III) through simple Lewis acid-base
- 	coordination, but ketones and alcohols oxidize U(III) to U(IV),
- 	and ketones oxidize Np(III)
- 	Associative ligand self-exchange process despite
- 	large ancillary ligands
- 	Binding affinities of three ligands mirror those of comparable
- 	ligands in acidic-aqueous Pu(III) process chemistry
- 	Autoradiography used to examine combinatorial Pu reaction

## Acknowledgements:

- Lanthanide Catalysis: Xinggao Fang
- TRU Catalysis: Ann Schake, Lonny Morgan
- Th/U Catalysis: Tony D’Alessio, Rick Broene
- Combinatorial: Grace Mann, Cyndi Wells, Becky Chamberlin, Mavis Lin
- LANL Laboratory Directed Research and Development Program
- DN_x0008_FSB 94-1 Core Technology Program
- Seaborg Institute for Transactinium Science