Thiocarbonyl complexes of iron: IV. Concerning the reaction of (CO) 4FeCS with mercury chloride in various solvents

Abstract

Mercury chloride, suspended in n-pentane, reacts with the iron carbonyl complexes (CO) 4FeCS and Fe(CO) 5 at room temperature to yield adducts of the composition (CO) 4FeCS · 3HgCl 2 ( 1a) and (CO) 5Fe · 3HgCl 2 ( 1b), respectively. The IR spectra reveal that both carbonyl compounds contain an iron—mercury donor bond. In ethanol as the solvent, the thiocarbonyl complex incorporates a solvent molecule, to yield the bright yellow thioalkoxycarbonyl complex cis-(CO) 4Fe(HgCl)(C(S)OC 2H 5) ( 2), whereas Fe(CO) 5 undergoes an oxidative addition to form the well known cis-(CO) 4Fe(HgCl) 2 ( 4) under the same reaction conditions. The mass spectrum of 2 exhibits the molecular ion as well as that of a dimer with the composition Fe 2(CO) 5[C(S)OC 2H 5] 2 ( 6), which is probably formed during the process by the thermal decomposition of 12. Attempts to isolate 6 by pyrolysis of 2 gave a red-brown oil which could not be purified. From Mössbauer spectroscopic studies a carbenoid formula for 2 can be excluded. In aqueous solution the reaction of (CO) 4FeCS with mercury chloride results in the formation of the yellow insoluble HgFe(CO) 3CS ( 3). A polymer structure similar to that of HgFe(CO) 4 is proposed for 3.