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.