The reaction of 1,1′-biphenyl-2,2′-dial with iron(III) and the crystal structure of piperidinium bis[µ-(1,1′-biphenyl-2,2′-diolato-O,µ-O′)(1,1′-biphenyl-2,2′-diolato-O,O′)ferrate(III)]–ethanol(½)

Abstract

The interaction of 1,1′-biphenyl-2,2′-diol (H₂L) with iron(III) perchlorate in the presence of piperidine yields the title complex [C₅H₁₂N]₂[(FeL₂)₂]·2EtOH, the crystal and molecular structure of which has been determined by single-crystal X-ray diffraction techniques. Crystals of the complex are triclinic, space group P, with a= 14.058(2), b= 9.976(1), c= 12.517(1)Å, α= 73.41 (1), β= 65.29(1), γ= 61.48(1)°, and Z= 1. After full-matrix least-squares refinement the final R value is 0.052 for 3 473 observed reflections. The complex contains [(FeL₂)₂]^2– dimers with seven-membered chelate rings, as well as piperidinium ions and ethanol molecules of crystallization. Each Fe^III is bonded to five oxygen atoms from L^2– ligands to give a distorted trigonal-bipyramidal co-ordination. The iron atoms are bridged by phenolate oxygens. The ethanol molecules, piperidinium ions, and L^2– ligands are linked by hydrogen bonds. Spectroscopic and magnetic data are in keeping with the dimeric [(FeL₂)₂]^2– structure, with weak antiferromagnetic coupling via the bridging oxygen atoms. Spectroscopic evidence indicates that the dimers are dissociated by nitrogen-donor solvents.