New Benzylpotassium Reagents and Their Utility for the Synthesis of Homoleptic Uranium(IV) Benzyl Derivatives

A new family of benzylpotassium reagents, KBn′(1-Bn′) (Bn′ = p-iPrBn, p-tBuBn, p-NMe2Bn, p-SMeBn, m-OMeBn, o-OMeBn, 2-picolyl), was synthesized using a modified literature procedure and characterized by multinuclear NMR spectroscopy. Combining four equivalents of 1-Bn′ with UCl4 at low temperature in THF afforded the homoleptic uranium(IV) derivatives 2-Bn′ (2-p-iPr, 2-p-tBu, 2-p-NMe2, 2-p-SMe, 2-o-Picolyl, 2-m-OMe, 2-o-OMe). In addition to 1H NMR spectroscopic characterization, structural studies of five of these organouranium compounds (2-p-iPr, 2-p-tBu, 2-o-Picolyl, 2-m-OMe, 2-o-OMe) were performed, showing that in many cases the benzyl groups are coordinated in an η4-fashion, lending stability to these otherwise low-coordinate molecules. In the cases of U(o-OMeBn)4 (2-o-OMe) and U(2-picolyl)4 (2-o-Picolyl), heteroatom coordination to the uranium center is observed.