Structure of Bromotrinitrosyl Iron, [Fe(NO)₃Br], and DFT Calculations of the Structures of [Fe(NO)₃X] (X = Cl, Br, I)

Bromotrinitrosyl iron was prepared by passing a stream of nitrogen monoxide over a mixture of iron dibromide and iron powder at elevated temperatures. It readily loses NO to give [(ON) 2 Fe(μ‐Br)Fe(CO) 2 ]. The structure of freshly obtained [Fe(NO) 3 Br] was determined by X‐ray diffraction at 200 K and shows (distorted) tetrahedral coordination with N–Fe–N and N–Fe–Br angles of 107.9(2)° and 111.0(2)° and bent Fe–N–O groups (162.5(6)°). The DFT calculations in the series [Fe(NO) 3 X] (X = Cl, Br, I) reproduce well the experimental structural parameters and vibrational frequencies.