Heavier Group 14 Congeners of Metalla-isobenzenes: Access to Metalla-isosilabenzene and Metalla-isogermabenzene by One-Pot Reactions

Metalla-isosilabenzenes and metalla-isogermabenzenes have been successfully synthesized by the formal [5+1]-cycloaddition of diethynylsilane or diethynylgermane with simple metal complexes. This is the first example of a heavier Group 14 metalla-isobenzene isomer bearing a cumulative double bond motif within a metallacycle. These novel complexes were fully characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. The stabilization of the cyclic metal-vinylidene complexes has been analyzed using density functional theory (DFT) calculations. When the metalla-isosilabenzenes bearing Si-H bond were treated with the trityl salt as a hydride scavenger, the formation of silylium cation was observed spectroscopically. Both of metalla-isosilabenzenes and metalla-isogermabenzenes can readily undergo migratory insertion reactions to furnish siloles or germoles.