Thorium-mediated ring-opening of tetrahydrofuran and the development of a new thorium starting material: Preparation and chemistry of ThI _4(DME)_2

摘要

The thorium(iv) tetraiodide complex ThI_4(DME)_2 (3) (DME = 1,2-dimethoxyethane) has been prepared in high yield by reacting the corresponding chloride complex ThCl_4(DME)_2 with an excess of trimethylsilyl iodide (Me_3SiI) in toluene. This new route avoids the use of thorium metal as a reagent. ThI_4(DME)_2 (3) exhibits excellent thermal stability compared to ThI_4(THF) _4 (1), which undergoes rapid ring-opening of THF at ambient temperature to yield the iodobutoxide complex ThI_3[O(CH _2)_4I](THF)_3 (2). Subsequent ligand-exchange between 2 and DME affords ThI_3[O(CH_2)_4I](DME) _2 (11), which can be converted to 3 with Me_3SiI. Salt metathesis between 2 and K(L~(Me)) (L~(Me) = (2,6- ~iPr_2C_6H_3)NC(Me)CHC(Me)N(2,6- ~iPr_2C_6H_3)) cleanly gives (L ~(Me))ThI_2[O(CH_2)_4I](THF) (10), which is a rare example of a thorium β-diketiminate complex. Complexes 2, 10, and 11 represent the first reported examples of THF ring-opening mediated by thorium. The synthetic utility of ThI_4(DME)_2 (3) is demonstrated by preparation of thorium(iv) alkoxide, amide, and organometallic compounds.