Divalent Ytterbium Complex-Catalyzed Homo- and Cross-Coupling of Primary Arylsilanes

Redistribution of primary silanes through C-Si and Si-H bond cleavage and reformation provides a straightforward synthesis of secondary silanes, but the poor selectivity and low efficiency severely hinders the application of this synthetic protocol. Here, we show that a newly synthesized divalent ytterbium alkyl complex exhibits unprecedentedly high catalytic activity toward the selective redistribution of primary arylsilanes to secondary arylsilanes. More significantly, this complex also effectively catalyzes the cross-coupling between electron-withdrawing substituted primary arylsilanes and electron-donating substituted primary arylsilanes to secondary arylsilanes containing two different aryls. DFT calculation indicates that the reaction always involve the exothermic formation of a hypervalent silicon upon facile addition of PhSiH₃ to the Yb-E (E = C, H) bond. This hypervalent compound can easily either generate directly the Yb-Ph complex, or indirectly through the formation of Yb-H, that is the key complex for the formation of Ph₂SiH₂.