Mechanistic Study on the Photochemical Conversion of Disilanyliron(II) Complexes to Monosilyliron(II) Complexes

Article abstract of DOI:10.1246/bcsj.61.2797

Photolysis of a C6D6 solution of CpFe(CO)2SiMe2SiMe3 (Cp=η⁵-C5H5) or (MeCp)Fe(CO)2SiMe2SiMe3 (MeCp=η⁵-C5H4Me) resulted in the formation of monosilyl derivative, CpFe(CO)2SiMe3 or (MeCp)Fe(CO)2SiMe3 in 64 or 59percent yield, respectively, together with small quantities of ferrocene and Cp2Fe2(CO)4 or their methylated derivatives.The yield of CpFe(CO)2SiMe3 increased to 88percent when the photolysis was carried out under a carbon monoxide atmosphere, while decreased to 22percent when argon was vigorously bubbled through the reaction mixture.These results are consistent with a mechanism involving dissociation and recombination of a carbonyl ligand which are common processes in photoreactions of transition-metal carbonyl derivatives.Dimethylsilylene moiety released during the photolysis was tried to be trapped with a hydrosilane, diene, and cyclotrisiloxane, but none of the expected products from the trapping reactions was detected, even in a trace amount.Photolysis of CpFe(CO)2SiMe2SiMeEt2 afforded, accompanying alkyl migration between silicon atoms, CpFe(CO)2SiMeEt2, CpFe(CO)2SiMe2Et, and CpFe(CO)2SiMe3 in 26, 33, and 4percent yields, respectively.Photolysis of a 1 : 1 mixture of CpFe(CO)2SiMe2SiMeEt2 and (MeCp)Fe(CO)2SiMe2SiMe3 provided only products expected from intramolecular alkyl migration mechanism.A possible mechanism involving silyl(silylene)iron intermediates is proposed to explain these results.