Uranium(III) and Uranium(IV) meta-Terphenylthiolate Complexes.

We report the synthesis and characterization of crystalline m-terphenylthiolate uranium complexes supported by the bulky ligand system, SAr(iPr6) (SAr(iPr6) = {SC(6)H(3)-2,6-(Tripp)(2)}; Tripp = 2,4,6-iPr-C(6)H(2)). Treatment of U(IV)Cl(4) with 2 equiv of KSAr(iPr6) in Et(2)O afforded both [U(IV)(SAr(iPr6))(2)(Cl)(2)] (1) and the Et(2)O adduct, [U(IV)(SAr(iPr6))(2)(Cl)(2)(Et(2)O)(2)] (1·Et(2)O) in poor yield. The reaction between [U(IV)(BH(4))(4)] and 1 equiv of KSAr(iPr6) in toluene gave several crystals of the double salt, [U(IV)(μ-SAr(iPr6))(BH(4))(2)(μ-BH(4))(μ(3)-BH(4))K](2) (2), and exposing the crude reaction mixture to Et(2)O gave the disulfide dimer, (SAr(iPr6))(2). The reaction between [U(IV)(BH(4))(4)] and 1 equiv of HSAr(iPr6) in hot toluene gave [U(III)(H(3)B·SAr(iPr6) κS,H,H)(BH(4))(2)] (3) which proved resistant to further substitution using either HSAr(iPr6) or KSAr(iPr6). Two U(III) mono-terphenylthiolates, [U(III)(SAr(iPr6))(BH(4))(2)] (4a) and [{U(III)(SAr(iPr6))(BH(4))}(2){μ-B(2)H(6)}] (4b), were isolated as a mixture from the reaction between [U(III)(BH(3))(3)(toluene)] and 1 equiv of KSAr(iPr6), while using 2 equiv of KSAr(iPr6) gave the bis-terphenylthiolate complex [U(III)(SAr(iPr6))(2)(BH(4))] (5). Complex 4b is a rare example of a nido-metalloborane. Complexes 1-5 have been characterized variously by single-crystal and powder X-ray diffraction, multinuclear NMR spectroscopy, infrared spectroscopy, UV-Vis-NIR spectroscopy, SQUID magnetometry, and elemental analyses as appropriate. Quantum chemical calculations have been employed to interpret the nature of the U-S bonding interactions across these complexes.