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

Abstract

Reaction of [U(TrenTIPS)(PH2)] (1, TrenTIPS=N(CH2CH2NSiPri3)3) with C6H5CH2K and [U(TrenTIPS)(THF)][BPh4] (2) afforded a rare diuranium parent phosphinidiide complex [{U(TrenTIPS)}2(μ-PH)] (3). Treatment of 3 with C6H5CH2K and two equivalents of benzo-15-crown-5 ether (B15C5) gave the diuranium μ-phosphido complex [{U(TrenTIPS)}2(μ-P)][K(B15C5)2] (4). Alternatively, reaction of [U(TrenTIPS)(PH)][Na(12C4)2] (5, 12C4=12-crown-4 ether) with [U{N(CH2CH2NSiMe2But)2CH2CH2NSi(Me)(CH2)(But)}] (6) produced the diuranium μ-phosphido complex [{U(TrenTIPS)}(μ-P){U(TrenDMBS)}][Na(12C4)2] [7, TrenDMBS=N(CH2CH2NSiMe2But)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.