Synthesis and reactivity of a terminal uranium() sulfide supported by siloxide ligands

• Published in: Chemical science (Cambridge) 2016-01, Vol.7 (9), p.5846-5856
• Main Authors: Andrez, Julie, Pécaut, Jacques, Scopelliti, Rosario, Kefalidis, Christos E, Maron, Laurent, Rosenzweig, Michael W, Meyer, Karsten, Mazzanti, Marinella
• Format: Article
• Language: English
• Subjects: Bonding; Carbon dioxide; Chemical Sciences; Chemistry; Coordination chemistry; Formations; Mathematical analysis; Sulfides; Synthesis; Terminals; Uranium
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c6sc00675b

The reactions of the tetrasiloxide U( iii ) complexes [U(OSi(O t Bu) 3 ) 4 K] and [U(OSi(O t Bu) 3 ) 4 ][K18c6] with 0.5 equiv. of triphenylphosphine sulfide led to reductive S-transfer reactions, affording the U( iv ) sulfide complexes [SU(OSi(O t Bu) 3 ) 4 K 2 ] 2 , 1 , and [{SU(OSi(O t Bu) 3 ) 4 K 2 } 2 (μ-18c6)], 2 , with concomitant formation of the U( iv ) complex [U(OSi(O t Bu) 3 ) 4 ]. Addition of 1 equiv. of 2.2.2-cryptand to complex 1 resulted in the isolation of a terminal sulfide complex, [SU(OSi(O t Bu) 3 ) 4 K][Kcryptand], 3 . The crucial role of the K + Lewis acid in these reductive sulfur transfer reactions was confirmed, since the formation of complex 3 from the reaction of the U( iii ) complex [U(OSi(O t Bu) 3 ) 4 ][Kcryptand] and 0.5 equiv. of PPh 3 S was not possible. Reactivity studies of the U( iv ) sulfide complexes showed that the sulfide is easily transferred to CO 2 and CS 2 to afford S-functionalized products. Moreover, we have found that the sulfide provides a convenient precursor for the synthesis of the corresponding U( iv ) hydrosulfide, {[(SH)U(OSi(O t Bu) 3 ) 4 ][K18c6]}, 5 , after protonation with PyHCl. Finally, DFT calculations were performed to investigate the nature of the U-S bond in complexes 1 , 3 and 5 . Based on various analyses, triple-bond character was suggested for the U-S bond in complexes 1 and 3 , while double-bond character was determined for the U-SH bond in complex 5 . The S-transfer reaction from Ph 3 PS to the tetrasiloxide U( iii ) complex [U(OSi(O t Bu) 3 ) 4 K] affords a stable U( iv ) triply bonded terminal sulfide that can be protonated to yield a U( iv ) doubly bonded terminal hydrosulfide.