Chemistry of iron complexes. Part 1. Synthesis, characterization, and structures of iron(III) complexes with bis(tertiary phosphine oxides)

Abstract

Bidentate bis(tertiary phosphine oxides)(L – L) such as PP′-methylene-(mdpo), PP′ethylene-(edpo), PP′-tetramethylene-(tmdpo), and PP′-hexamethylene-bis(diphenylphosphine oxides)(hmdpo) on reaction with iron(III) chloride or nitrate in suitable organic solvents yield complexes of the types: [Fe(L – L)₂Cl₂][FeCl₄]·xH₂O (x= 0 for all except hmdpo), [Fe(L – L)(ONO)₂)₃](L – L = tmdpo or hmdpo), [Fe(L–L)₂(ONO₂)₂][NO₃]·H₂O (L – L = edpo), and [Fe₂(L – L)₃(ONO₂)₄][NO₃]₂·2H₂O (L – L = mdpo). These complexes have been characterized by elemental analyses, i.r., far-i.r., u.v.–visible, e.s.r., and Mössbauer spectral data, molar conductance, thermogravimetric analysis, magnetic moments, and X-ray diffraction data. The cation [Fe(L – L)₂Cl₂]⁺ has been assigned a trans-octahedral structure. The nitrate complex of mdpo has a dimeric trigonal bipyramidal cation while the complex of edpo has a cis-octahedral structure. The nitrate complexes of tmdpo and hmdpo also have trigonal bipyramidal structure.