Selective and stepwise bromodemethylation of the silyl ligand in iron(II) silyl complexes with boron tribromide

Treatment of Cp*(CO)₂FeSiMe₂R (Cp* = C₅Me₅, R = Me and Ph) with 1 equiv of BBr₃ at room temperature afforded Cp*(CO)₂FeSiBrMeR (R = Me and Ph) and MeBBr₂ in high yields via bromodemethylation of the silyl ligand. Cp*(CO)₂FeSiBrMeR (R = Me and Ph) was further converted to Cp*(CO)₂FeSiBr₂R (R = Me and Ph) quantitatively on addition of another equivalent of BBr₃ and heating. Treatment of Cp*(CO)₂FeSiMe₂SiMe₃ with 1 equiv of BBr₃ at room temperature led to selective bromodemethylation at the α-silicon atom to produce Cp*(CO)₂FeSiBrMeSiMe ₃, which was also converted to Cp*(CO)₂FeSiBr ₂SiMe₃ on heating with another equivalent of BBr ₃ at 40°C in quantitative yield. The solid-state structure of Cp*(CO)₂FeSiBr₂SiMe₃ was confirmed by X-ray crystal structure determination.