The reactivity of organometallic diamido-actinide complexes

This thesis explores the coordination chemistry of diamido-actinide complexes and establishes them as active catalysts for a number of transformations. The synthesis, characterization and reactivity studies of a series of diamido-ether actinide complexes are described. The focus of these studies include the use of two different ligand frameworks: a silyl ether backbone of the form [(RNHSiMe2)2O] ([RNON]H2; R = tBu, 2,6-iPr2Ph, 2,4,6-Me3Ph), and an alkyl ether backbone of the form [(RNHCH2CH2)2O] ([RNCOCN]H2; R = 2,6-iPr2Ph). A series of diamido-ether actinide halide complexes supported by these ligands can be prepared through the addition of either [RNON]Li2 or [RNCOCN]Li2 to UCl4 or ThCl4•2DME. These halide complexes can then be alkylated via the addition of appropriate alkylating reagents such as LiCH2SiMe3, LiCH(SiMe3)2 or KCH2Ph. A series of new diamido-actinide alkoxide complexes has also been prepared from the addition of alkoxide reagents such as LiOiPr or KOtBu. These diamido-actinide alkyl complexes are explored as catalysts for ethylene polymerization, lactide polymerization, and intramolecular hydroamination. In all cases, these alkyl complexes are found to be active catalysts, but in each instance, different complexes are established as the most active species. The mixed-donor amido-amino-siloxo ligands [(RN(Li)SiMe2N(R)SiMe2O] ([RNNO]Li2; R = 2,6-iPr2Ph, 2,4,6-Me3Ph), are also used to prepare a series of new actinide-based complexes. The addition of one equivalent of ligand per metal centre yields “ate” complexes that retain solvent and salt in the coordination sphere of the metal while the addition of two equivalents of ligand per metal centre yields bis(amido-siloxo)actinide-based products. These complexes, like their diamido counterparts, can be alkylated through the addition of appropriate alkylating reagents such as LiCH2SiMe3. Lastly, oxidation reactions with {[tBuNON]UCl2}2, [iPr2PhNCOCN]UCl3Li•THF and [Me3PhNNO]2U are described. The preparation of two non-uranyl U(VI) complexes from the oxidation of {[tBuNON]UCl2}2 are reported. Furthermore, the oxidation of [Me3PhNNO]2U yields a new, ligand-activated U(V) complex.