SYNTHESIS AND CHEMISTRY OF PENTAMETHYL CYCLOPENTADIENYL COMPLEXES OF THORIUM AND URANIUM: A NEW CHAPTER IN ORGANOACTINIDE CHEMISTRY

This thesis describes the synthesis, chemistry, and properties of bis(pentamethylcyclopentadienyl) organoactinide complexes of the general type, {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)ML(,2) (M=Th, U; L=a variety of ligands). These complexes represent a new class of highly reactive and coordinatively unsaturated actinide organometallics which had been previously obtained only with difficulty using unsubstituted cyclopentadienyl ligands.;The second chapter deals primarily with the organometallic chemistry of the lower valent uranium(III) species, {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)U((mu)-Cl)(,3), produced by hydrogenolysis of the complexes {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)U(R)Cl (R=CH(,3), CH(,2)Si(CH(,3))(,3)). An extensive chemistry is derived from this complex and has allowed the preparation of other uranium(III) organometallic complexes.;The third chapter describes the reactions of carbon monoxide with a variety of bis(pentamethylcyclopentadienyl) thorium and uranium alkyls and hydrides ({(eta)('5)-C(,5)(CH(,3))(,5)}(,2)MR(,2), {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)M(R)X, and {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)M(H)X; M=Th, U; R=hydrocarbyl) to produce migratory insertion products. In general these reactions are mediated by highly reactive dihapto-bound acyl complexes, {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)M((eta)('2)-COR)X (M=Th, U), which exhibit an oxycarbene-like reactivity. A number of such complexes have been isolated and characterized.;Finally, the fourth chapter describes the insertion of carbon monoxide into thorium and uranium metal-nitrogen bonds in the complexes {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)M(NR(,2))(,2) and {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)M(NR(,2))X (M=Th, U; X=Cl; R=CH(,3), C(,2)H(,5)) to yield dihapto-carbamoyl complexes. A detailed study of the chemistry, structures, and structural dynamics of these complexes has been undertaken.;The first chapter deals with the synthesis and properties of the complexes {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)MX(,2) (M=Th, U; X=Cl). These complexes can be alkylated with a variety of hydrocarbyllithium reagents yielding the chloralkyl and dialkyl derivatives, {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)M(R)Cl and {(eta)('5)-C(,5)(CH(,3))(,5)}(,2)MR(,2). Hydrogenolysis of the dialkyls leads to the production of stable hydride complexes, {{(eta)('5)-C(,5)(CH(,3))(,5)}(,2)M((mu)-H)H}(,2) (M=Th, U). The crystal structure of the thorium hydride complex has been determined by a neutron diffraction study, and a dimeric structure containing both bridging and terminal hydride ligands is revealed. The hydride complexes catalyze olefin hydrogenation and aromatic hydrocarbon C-H bond activation. A number of other actinide alkyl and hydride complexes have been prepared, and their physical and chemical properties have been investigated in detail. The chemistry of the bis(pentamethylcyclopentadienyl) thorium and uranium complexes is found to be closely related to the chemistry of analogous transition metal complexes of Ti, Zr, and Hf.;All of the new complexes were characterized by infrared and nuclear magnetic resonance spectroscopy, elemental analysis, and, in several cases, by cryoscopic molecular weight measurements. A number of single crystal X-ray structure analyses are also described.;In general, the observed chemistry of thorium and uranium is similar to that known for the lanthanides and parallels that known for the elements Ti, Zr, and Hf.