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Six-coordinate nitro complexes of iron(III) porphyrins with trans S-donor ligands. Oxo-transfer reactivity in the
Tigran S Kurtikyan1, Astghik A Hovhannisyan, Alexei V Iretskii
1Molecule Structure Research Centre NAS, 0014, Yerevan, Armenia. kurto@netsys.am
Abstract:
Spectroscopic studies demonstrate that the 5-coordinate O-nitrito complexes Fe(Por)(eta(1)-ONO) (Por--meso-tetraphenyl- or meso-tetra-p-tolyl-porphyrinato dianions) react with the thioethers (R(2)S) dimethylsulfide and tetrahydrothiophene to give the 6-coordinate N-nitrito complexes Fe(Por)(R(2)S)(NO(2)). These reactions were conducted in low-temperature porous layered solids formed in a cryostat; however, with excess R(2)S in the atmosphere, the same species are moderately stable at room temperature. Six-coordinate O-nitrito isomers were not observed with the R(2)S proximal ligands, even though DFT calculations for the Fe(P)(DMS)(eta(1)-ONO) and Fe(P)(DMS)(NO(2)) models (P = porphinato dianion, DMS = dimethyl sulfide) show the latter to be only modestly lower energy (approximately 8 kJ/mol) than the former. Leaving this system at room temperature in the presence of excess R(2)S leads eventually to the appearance in the FTIR spectra of the nu(NO) band characteristic of the ferrous nitrosyl Fe(Por)(NO). Concomitantly, the mass spectrum of the gas phase demonstrated the molecular peaks of the sulfoxides R(2)SO, indicating oxygen atom transfer reactivity for the ferric porphryinato complexes of nitrite.
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