Thorium alkoxide chemistry: Preparation and structural studies of thorium tetrakis (di-iso-propylmethoxide) and its Lewis base adducts

The thorium metallacycle [(Me3Si)2N]2Th(CH2SiMe2NSiMe3) (1) reacts with four equivalents of 2, 4-dimethylpentan-3-ol (di-iso-propylmethanol) in hexane at room temperature to produce the first structurally characterized homoleptic actinide alkoxide complex, [Th2(OCH-i-Pr2)4]2 (2). 1H NMR spectra of 2 in non-coordinating solvents indicate a monomer-dimer equilibrium in solution at ambient temperatures between 2 and its monomer Th2(OCH-i-Pr2)4 (3). Addition of Lewis bases such as quinuclidine, DME (DME = 1,2 dimethoxyethane) or pyridine give the five- and six-coordinate mononuclear adducts Th(OCH-i-Pr2)4(quin) (4), Th(OCH-i-Pr2)4(DME) (5) and Th(OCH-i-Pr2)4py2 (6) respectively. Reaction of 6 with one equivalent of trimethylsilyliodide produces the mono-iodide derivative Th(OCH-i-Pr2)3py2 (7)