A Base‐Free Thorium–Terminal‐Imido Metallocene: Synthesis, Structure, and Reactivity

Abstract

Abstract The synthesis, structure, and reactivity of a base‐free thorium terminal‐imido metallocene have been comprehensively studied. Treatment of thorium metallocenes [{η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 } 2 ThMe 2 ] and [{η 5 ‐1,3‐(Me 3 C) 2 C 5 H 3 } 2 ThMe 2 ] with RNH 2 gives diamides [{η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 } 2 Th(NHR) 2 ] (R=Me ( 7 ), p ‐tolyl ( 8 )) and [{η 5 ‐1,3‐(Me 3 C) 2 C 5 H 3 } 2 Th(NH‐ p ‐tolyl) 2 ] ( 9 ), respectively. Diamides 7 and 9 do not eliminate methylamine or p ‐toluidine, but sublime without decomposition at 150 °C under vacuum (0.01 mmHg), whereas diamide 8 is converted at 140 °C/0.01 mmHg into the primary amine p ‐tolyl‐NH 2 and [{η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 } 2 ThN( p ‐tolyl)] ( 10 ), which may be isolated in pure form. Imido metallocene 10 does not react with electrophiles such as alkylsilyl halides; however, it reacts with electron‐rich or unsaturated reagents. For example, reaction of 10 with sulfur affords the metallacycle [{η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 } 2 Th{N( p ‐tolyl)S‐S}]. Imido 10 is an important intermediate in the catalytic hydroamination of internal alkynes, and an efficient catalyst for the trimerization of PhCN. Density functional theory (DFT) studies provide a detailed understanding of the experimentally observed reactivity patterns.