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

Reaction of [U(Tren(TIPS))(PH(2))] (1, Tren(TIPS)=N(CH(2)CH(2)NSiPr(i) (3))(3)) with C(6)H(5)CH(2)K and [U(Tren(TIPS))(THF)][BPh(4)] (2) afforded a rare diuranium parent phosphinidiide complex [{U(Tren(TIPS))}(2)(μ‐PH)] (3). Treatment of 3 with C(6)H(5)CH(2)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(CH(2)CH(2)NSiMe(2)Bu(t))(2)CH(2)CH(2)NSi(Me)(CH(2))(Bu(t))}] (6) produced the diuranium μ‐phosphido complex [{U(Tren(TIPS))}(μ‐P){U(Tren(DMBS))}][Na(12C4)(2)] [7, Tren(DMBS)=N(CH(2)CH(2)NSiMe(2)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.