Experimental and Computational Studies on a Base‐Free Terminal Uranium Phosphinidene Metallocene

Abstract

Abstract The first stable base‐free terminal uranium phosphinidene metallocene is presented; and its structure and reactivity have been studied in detail and compared to that of the corresponding thorium derivative. Salt metathesis reaction of the methyl iodide uranium metallocene Cp’’’ 2 U(I)Me ( 2 , Cp’’’= η 5 ‐1,2,4‐(Me 3 C) 3 C 5 H 2 ) with Mes*PHK (Mes*=2,4,6‐(Me 3 C) 3 C 6 H 2 ) in THF yields the base‐free terminal uranium phosphinidene metallocene, Cp’’’ 2 U=PMes* ( 3 ). In addition, density functional theory (DFT) studies suggest substantial 5f orbital contributions to the bonding within the uranium phosphinidene [U]=PAr moiety, which results in a more covalent bonding between the [Cp’’’ 2 U] 2+ and [Mes*P] 2− fragments than that for the related thorium derivative. This difference in bonding besides steric reasons causes different reactivity patterns for both molecules. Therefore, the uranium derivative 3 may act as a Cp’’’ 2 U(II) synthon releasing the phosphinidene moiety (Mes*P:) when treated with alkynes or a variety of hetero‐unsaturated molecules such as imines, thiazoles, ketazines, bipy, organic azides, diazene derivatives, ketones, and carbodiimides.