Calix[4]pyrrole Hydridosilicate: The Elusive Planar Tetracoordinate Silicon Imparts Striking Stability to Its Anionic Silicon Hydride

Anionic hydridosilicates are highly
reactive and strong hydride
donors. In contrast, calix[4]­pyrrole hydridosilicate is an entirely
water-stable, anionic silicon hydride, which does not show hydridic
reactivity. However, it still acts as an electron donor and enables
the detection of a single electron transfer process in the reduction
chemistry with hydridosilicates. Most important, these unusual properties
are imparted by the unique planar structure of its elusive parent
neutral silane-substantiating the effect of planar tetracoordinate
silicon for the first time.