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

Abstract

A new family of benzylpotassium reagents, KBn′(<b>1-Bn</b>′) (Bn′ = <i>p</i>-^<i>i</i>PrBn, <i>p</i>-^<i>t</i>BuBn, <i>p</i>-NMe₂Bn, <i>p</i>-SMeBn, <i>m-</i>OMeBn, <i>o-</i>OMeBn, 2-picolyl), was synthesized using a modified literature procedure and characterized by multinuclear NMR spectroscopy. Combining four equivalents of <b>1-Bn</b>′ with UCl₄ at low temperature in THF afforded the homoleptic uranium­(IV) derivatives <b>2-Bn</b>′ (<b>2-</b><i><b>p</b></i><b>-</b>^{<b><i>i</i></b>}<b>Pr</b>,<b> 2-</b><i><b>p</b></i><b>-</b>^{<b><i>t</i></b>}<b>Bu</b>,<b> 2-</b><i><b>p</b></i><b>-NMe</b>_<b>2</b>, <b>2-</b><i><b>p</b></i><b>-SMe</b>,<b> 2-</b><i><b>o</b></i><b>-Picolyl</b>, <b>2-</b><i><b>m</b></i><b>-OMe</b>, <b>2-</b><i><b>o</b></i><b>-OMe</b>). In addition to ¹H NMR spectroscopic characterization, structural studies of five of these organouranium compounds (<b>2-</b><i><b>p</b></i><b>-</b>^{<b><i>i</i></b>}<b>Pr</b>,<b> 2-</b><i><b>p</b></i><b>-</b>^{<b><i>t</i></b>}<b>Bu</b>,<b> 2-</b><i><b>o</b></i><b>-Picolyl</b>, <b>2-</b><i><b>m</b></i><b>-OMe</b>, <b>2-</b><i><b>o</b></i><b>-OMe</b>) 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(<i>o-</i>OMeBn)₄ (<b>2-</b><i><b>o</b></i><b>-OMe</b>) and U­(2-picolyl)₄ (<b>2-</b><i><b>o</b></i><b>-Picolyl</b>), heteroatom coordination to the uranium center is observed