title: Characterization of the mixed axial ligand complex (4-cyanopyridine)(imidazole)(tetramesitylporphinato)iron(iii) perchlorate. Stabilization by synergic bonding.
abstract: The reaction of [Fe(TMP)(OClO3)], where TMP is the dianion of tetramesitylporphyrin, with a combination of a strongπ-acceptor ligand and aπ-donating imidazole can lead to the preparation of mixed-ligand complexes [Fe(Porph)(4-CNPy)(L)]+where L is imidazole itself or 1-acetylimidazole and 4-cyanopyridine is the strongπacceptor ligand. The stability of the new mixed-ligand pair is the presumed result of synergic bonding between the two axial ligands. The molecular structure and other characterization of the new mixed axial ligand complex, [Fe(TMP)(4-CNPy)(HIm)]ClO4is described. The axial ligands have a relative perpendicular arrangement with Fe-N(imidazole) = 1.945 Å and Fe-N(pyridine) = 2.021 Å The average equatorial Fe-Npdistance is 1.963 Å, which is consistent with the S4-ruffled TMP core. Despite the relative perpendicular arrangement of axial ligands, the EPR spectrum of the complex is a rhombic signal and not a large gmaxsignal. The EPR g-values are g1= 3.05, g2= 2.07, and g3= 1.22. A quadrupole doublet was seen in the Mössbauer spectrum with an isomer shift of 0.197 mm/s and quadrupole splitting of 1.935 mm/s. Two crystalline forms of [Fe(TMP)(4-CNPy)(HIm)]ClO4have been characterized; the two forms differ only in the solvent content of the lattice. Crystal data for formA:a= 15.432 (12) Å,b= 20.696 (2) Å,c= 19.970 (5) Å, andβ= 99.256 (14)°, monoclinic, space groupP21/n, V = 6295 (2) Å3, Z = 4, formula FeCl3O4N8C69H69, 8397 observed data, R1= 0.086, wR2= 0.210, refinement onF2. Crystal data for formB:a= 15.267 (3) Å,b= 20.377 (6) Å,c= 19.670 (4) Å, andβ= 98.14 (1)°, monoclinic, space groupP21/n, V = 6058 (4) Å3, Z = 4, formula C65.25H60.5Cl1.5FeN8O4, 5464 observed data, R1= 0.096, wR2= 0.112, refinement onF.
authors: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana USA 46556.
authors: Judith A
authors: JA
authors: Serth-Guzzo
authors: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana USA 46556.
authors: Ilona
authors: I
authors: Turowska-Tyrk
authors: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana USA 46556.
authors: Martin K
authors: MK
authors: Safo
authors: Department of Chemistry and Biochemistry, University of Arizona, Tuscon, Arizona USA 85721-0041.
authors: F Ann
authors: FA
authors: Walker
authors: Department of Physics, University of Illinois, Urbana, Illinois USA 61801.
authors: Peter G
authors: PG
authors: Debrunner
authors: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana USA 46556.
authors: W Robert
authors: WR
authors: Scheidt