Synthesis and reactivity of hydrogen-rich uranium–rhenium compounds; an unsuspected detrimental effect of alkali-metal halide on chemical metathesis

Abstract

Reaction of [U(η-C₅Me₅)₂Cl(thf)] and [K(thf)₂][ReH₆(PPh₃)₂] did not afford the metathesis product with elimination of KCl but gave the anionic addition compound [K(thf)₂][Cl(η-C₅Me₅)₂ UH₆Re(PPh₃)₂](thf = tetrahydrofuran); the borohydride analogue was similarly prepared. The bimetallic complexes [(η-C₅H₄R)₃UH₆Re(PPh₃)₂](R = Bu^t or SiMe₃) could not be isolated from [U(η-C₅H₄R)₃Cl] and [K(thf)₂][ReH₆(PPh₃)₂] because of their reverse cleavage by KCl which led to an equilibrium mixture; these hexahydrides were cleanly synthesized by reaction of [U(η-C₅H₄R)₃][BPh₄] and [K(thf)₂][ReH₆(PPh₃)₂].