Synthesis and electrode reactions of difluorogermanium(IV) porphyrins. Molecular stereochemistry and crystal structure of difluoro-(2,3,7,8,12,13,17,18-octaethylporphyrinato)germanium(IV)

Abstract

The difluorogermanium(IV) porphyrins [GeF₂(P)][P = 2,3,7,8,12,13,17,18-octaethylporphyrinate(2–)(oep), 5,10,15,20-tetraphenylporphyrinate(2–)(tpp), or 5,10,15,20-tetra-p-tolylporphyrinate(2–)(tptp)] have been prepared by reacting hydrogen fluoride with the appropriate dichloro derivative [GeCl₂(P)]. The complexes were characterized by elemental analysis, ¹H n.m.r., i.r., and u.v.–visible spectroscopy. The electrochemical behaviour was investigated in non-aqueous media while spectroelectrochemistry and e.s.r. were used to characterize the oxidized and reduced complexes. Each complex could be reversibly oxidized or reduced by one electron. In each case these electron additions or abstractions were ring centred. The crystal structure [GeF₂(oep)] was determined by X-ray diffraction methods. The complex crystallizes in the space group I4₁/a, with a=b= 15.202(2), c= 13.910(3)Å, and R= 0.034 and R′= 0.035 for 1 465 unique reflections. The germanium atom lies on a crystallographic axis and is co-ordinated by the porphyrin ring and two fluorine atoms; the short germanium–fluorine distance [1.790(2)Å] is very close to that found in [FeF(tpp)][1.792(2)Å].