Syntheses, properties and Mössbauer studies of mono- and di-nitrile phosphine complexes of iron(II). Crystal structures of trans-[Fe(NCR)2(Et2PCH2CH2PEt2)2][BF4]2 (R = Me or CH2C6H4OMe-4)†

Abstract

Complexes trans-[FeL(NCR)(depe)₂]Y_n (R = Me, Et, CH₂C₆H₄OMe-4, C₆H₄OMe-4, C₆H₄Me-4, Ph, C₆H₄F-4 or C₆H₄NO₂-4; depe = Et₂PCH₂CH₂PEt₂; Y = BF₄ or BPh₄; L = Br, n = 1 1; L = NCR, n = 2 2) have been prepared by treatment of trans-[FeBr₂(depe)₂] (in MeOH and in the presence of [NBu₄][BF₄] or Na[BPh₄]) with a stoichiometric or a twofold molar amount of the appropriate organonitrile. Electronic, NMR and Mössbauer spectral as well as FAB mass spectrometric data are reported. Mössbauer partial isomer shift (p.i.s.) and partial quadrupole splitting (p.q.s.) parameters have been estimated for the nitrile ligands and rationalised, with the overall i.s. and q.s., in terms of π- and σ-electronic effects. The FAB MS fragmentation patterns are also proposed, and the crystal structures of 2 (R = Me or CH₂C₆H₄OMe-4, Y = BF₄) have been determined.