LAUSR

Di-tert-butylsilylene (SitBu2) has been detected directly in solution and its reactivity characterized by laser flash photolysis methods. Laser photolysis of 7,7-di-tert-butyl-7-silabicyclo[4.1.0]heptane (5) affords a transient product that exhibits λmax ≈ 520 nm and decays on the microsecond time scale, concurrent with the growth of a second, much longer-lived species exhibiting λmax = 290, 430 nm. The two species are assigned to di-tert-butylsilylene (SitBu2) and its disilene dimer, tetra-tert-butyldisilene (tBu2Si═SitBu2, 8), respectively. Transient absorption spectra recorded by laser photolysis of hexa-tert-butylcyclotrisilane (7) are consistent with the prompt formation of both SitBu2 and 8, the former appearing as a weak shoulder absorption on the red edge of the intense absorption band due to the disilene. Absolute rate constants were determined for the reactions of SitBu2 with a variety of representative silylene substrates in hexanes at 25 °C, including methanol, triethylsilane, acetic acid, ace...