PHOTOREACTIONS OF SILYLIRON(II) COMPLEXES CP-ASTERISK-FE(CO)2SIME3 (CP-ASTERISK=ETA-5-C5H5,ETA-5-C5ME5) IN THE PRESENCE OF TRIHYDROSILANES

The photochemistry of silyliron(II) complexes Cp*Fe(CO)2SiMe3 (CP* = eta-5-C5H5, eta-5-C5Me5) in the presence of trihydrosilanes is described. Three types of products were observed, depending on the bulkiness of the Cp* ligands and the substituents on the trihydrosilanes: (eta-5-C5H5)Fe(CO)2SiMe3 reacts with tert-alkylsilanes RSiH3 (R = (t)Bu, C(Me2)2H) upon irradiation to give silylene-bridged diiron complexes (eta-5-C5H5)2Fe2(CO)3(mu-SiHR) in good yields. In contrast, (eta-5-C5Me5)Fe(CO)2SiMe3 reacts with the tert-alkylsilanes photochemically to give silyl monoiron complexes (eta-5-C5Me5)Fe(CO)2SiH2R exclusively. Using p-TolSiH3 instead of tert-alkylsilane, the main photolysis product was the hydridobis(silyl)iron complex Cp*Fe(CO)SiMe3(H)SiH2-p-Tol. The X-ray crystal structure analysis of (eta-5-C5H5)2Fe2(CO)3(mu-SiH(t)Bu) revealed that this complex adopts a geometry in which the two Cp rings and a Si-H bond are located on the same side with respect to the SiFe2C four-membered ring. Si-29 NMR spectra of the silylene-bridged diiron complexes showed signals at remarkably low field (delta-235.5-289.1 ppm). A mechanism for the formation of these silylene-bridged diiron complexes is proposed.