Cationic low-spin bis[1,2-bis(dialkylphosphino)ethane]iron(II) complexes

Abstract

The complexes trans-[FeCl₂(depe)₂] and trans-[FeCl₂(dmpe)₂](depe = Et₂PCH₂CH₂PEt₂, dmpe = Me₂PCH₂CH₂PMe₂) dissolve in acetonitrile and methanol to give 1 : 1 electrolytes. In methanol solution trans-[FeCl₂(depe)₂] reacts rapidly with a variety of π-acceptor ligands to yield cations of the type trans-[FeCl(L)(depe)₂]⁺[L = CO, NO⁺, RCN, ½N₂, and P(OMe)₃] which have been isolated as their tetraphenylborate or chloride salts. In acetone solution the neutral complexes react much more slowly and with a reduced range of ligands L. Where reaction does take place (L = CO or RNC) a mixture of cis and trans isomers is obtained and these have been isolated. The complex trans-[FeI₂(depe)₂] is insoluble in methanol, but a suspension of the complex in this solvent reacts slowly with CO to give a mixture of cis- and trans-[Fe(CO)I(depe)₂]⁺. Other complexes of the type trans-[FeX₂(depe)₂](X = NCO or NCS) do not react with CO in methanol. I.r. and Mössbauer spectra have been recorded for some of the complexes and enable the stereochemistry of the complexes to be assigned.