Organomercury complexes of iron, cobalt, and tungsten

Abstract

The iron complexes cis-[Fe(CO)₄(HgR)₂][R = CH₂SiMe₃, CH(SiMe₃)₂, or C(SiMe₃)₃] have been prepared. Their spectroscopic properties are reported, and their tendency to symmetrise, e.g. n[Fe(CO)₄(HgR)₂]→nHgR₂+[{HgFe(CO)₄}_n], has been examined. The complex [Fe(CO)₄{Hg[C(SiMe₃)₃]}₂] resists thermal symmetrisation; it reacts with HgBr₂ and with [Fe(CO)₄(HgBr)₂] forming HgBr[C(SiMe₃)₃] and [{HgFe(CO)₄}_n] probably via the intermediate [Fe(CO)₄(HgBr){Hg[C(SiMe₃)₃]}]. At 60 °C the carbonyl groups in cis-[Fe(CO)₄{Hg[C(SiMe₃)₃]}₂] are fluxional, whereas at –55 °C axial and equatorial CO groups can be distinguished. The fluxional behaviour does not involve dissociation, and there is no evidence for the trans isomer. At 35 °C this complex shows an anomalous ¹³CO spectrum. The impure complexes [Co(CO)₄(HgCH₂SiMe₃)] and [W(CO)₃(η-C₅H₅)(HgCH₂SiMe₃)] are also reported.