Fe−B Bonding in (Dibromoboryl)ferrocene: A Structural and Theoretical Investigation

Abstract

The geometry and electronic structure of borylferrocenes, FcBR2, have been investigated by X-ray structure analysis (R = Br) and density functional theory (DFT) calculations (R = H). An interaction between filled d-type orbitals at iron and the empty p orbital of boron causes bending of the BR2 substituent toward the central iron atom. The dip angle α* is 17.7° (18.9°) for FcBBr2 (X-ray structure). Slightly larger values were calculated for the sterically unhindered model system FcBH2 (α* = 21.6° [LDA/NL]). According to the DFT calculations, the Fe−B interaction in FcBH2 is considerably weaker than the Fe−Cexo bond of the isoelectronic cation FcCH2+ (α* = 41.0° [LDA/NL]). In 1,1‘-diborylated ferrocene no energetically preferred rotamer was detected by our DFT calculations.