Novel silacyclohexadienyl chromium and iron complexes bearing a bulky substituent on the central silicon atom
Novel hydrido(silacyclohexadienyl)chromium complexes bearing a bulky substituent, Tbt (2,4,6-tris[bis(trimethylsilyl)methyl]phenyl), were synthesized using formal insertion reactions of Cr(0) into C–H or Si–H bond. When the reactions of 1-silacyclohexa-2,4-dienes bearing a hydroxy or chloro group on the silicon atom with [Cr(CH3CN)3(CO)3] were performed, the corresponding hydrido(1-silacyclohexa-2,4-dienyl) complexes were obtained as the sole product. A similar reaction of a hydrosilane having a similar skeleton with [Cr(CH3CN)3(CO)3] gave an unprecedented type of silacyclohexadienyl complex, hydrido(1-silacyclohexa-1,3-dienyl)chromium bearing a three-center bonding interaction among the silicon, hydrogen, and chromium atoms. These are the first syntheses of silacyclohexadienyl complexes by the formal insertion reaction toward the corresponding silacyclohexadienes. Furthermore, the isolation of the silacyclohexadienyl anion was achieved; it was applied to synthesis of the corresponding sandwich-type iron complex. Structures of the newly obtained complexes were revealed based on their NMR and IR spectroscopic data and X-ray diffraction study.