Unpredictable reaction of phenyltrichlorosilane with tert-butyllithium

The reaction of PhSiCl3 with one equivalent of Li[tBu] at r. t. yielded tBuPhSiCl2 whereas tBu2PhSiCl was only a minor product of the reaction of two molar equivalents Li[tBu] with PhSiCl3 at 60 °C. By contrast, at r. t. tBuPhSiCl2 was solely formed by this reaction. Treatment of PhSiCl3 with three or more equivalents of Li[tBu] at 98 °C yielded a mixture of tBu2PhSiH and tBu2(tBuC6H4CMe2CH2)SiH (3). Both silanes could easily be separated from each other: tBu2PhSiH was distilled from the reaction mixture and the silane 3 could be crystallized from the dissolved distillation residue. X-ray quality crystals of 3 were grown from a benzene solution at ambient temperature (monoclinic, P21/c).