Synthesis, crystal structure and dynamic behaviour in solution of monocyclooctatetraene uranium alkoxides

Treatment of [U(cot)(BH4)2](cot =η-C8H8) with ROH (R = Et, Pri or But) led to successive formation of the alkoxide derivatives [U(cot)(BH4)(OR)]4 and [U(cot)(OR)2]5. Their structure and dynamic behaviour in solution have been studied by NMR spectroscopy; complexes 4 are monomeric in tetrahydrofuran whereas 5 are dimeric in this solvent and monomeric in pyridine. Rapid stereoselective exchange occurs between the terminal propoxide ligands of [{U(cot)(OPri)(µ-OPri)}2] and free PriOH. The crystal structures of [{U(cot)(BH4)(µ-OEt)}2] and [{U(cot)(OPri)(µ-OPri)}2] have been determined.