Crystalline Diuranium Phosphinidiide and μ-Phosphido Complexes with Symmetric and Asymmetric UPU Cores.

Reaction of [U(Tren(TIPS) )(PH2 )] (1, Tren(TIPS) =N(CH2 CH2 NSiPr(i)3 )3 ) with C6 H5 CH2 K and [U(Tren(TIPS) )(THF)][BPh4 ] (2) afforded a rare diuranium parent phosphinidiide complex [{U(Tren(TIPS) )}2 (μ-PH)] (3). Treatment of 3 with C6 H5 CH2 K and two equivalents of benzo-15-crown-5 ether (B15C5) gave the diuranium μ-phosphido complex [{U(Tren(TIPS) )}2 (μ-P)][K(B15C5)2 ] (4). Alternatively, reaction of [U(Tren(TIPS) )(PH)][Na(12C4)2 ] (5, 12C4=12-crown-4 ether) with [U{N(CH2 CH2 NSiMe2 Bu(t) )2 CH2 CH2 NSi(Me)(CH2 )(Bu(t) )}] (6) produced the diuranium μ-phosphido complex [{U(Tren(TIPS) )}(μ-P){U(Tren(DMBS) )}][Na(12C4)2 ] [7, Tren(DMBS) =N(CH2 CH2 NSiMe2 Bu(t) )3 ]. Compounds 4 and 7 are unprecedented examples of uranium phosphido complexes outside of matrix isolation studies, and they rapidly decompose in solution underscoring the paucity of uranium phosphido complexes. Interestingly, 4 and 7 feature symmetric and asymmetric UPU cores, respectively, reflecting their differing steric profiles.