Remarkably Stable Iron Porphyrins Bearing Nonheteroatom-Stabilized Carbene or (Alkoxycarbonyl)carbenes: Isolation, X-ray Crystal Structures, and Carbon Atom Transfer Reactions with Hydrocarbons

Abstract

Reactions of [Fe(TPFPP)] (TPFPP = meso-tetrakis(pentafluorophenyl)porphyrinato dianion) with diazo compounds N₂C(Ph)R (R = Ph, CO₂Et, CO₂CH₂CHCH₂) afforded [Fe(TPFPP)(C(Ph)R)] (R = Ph (1), CO₂Et (2), CO₂CH₂CHCH₂ (3)) in 65−70% yields. Treatment of 1 with N-methylimidazole (MeIm) gave the adduct [Fe(TPFPP)(CPh₂)(MeIm)] (4) in 65% yield. These new iron porphyrin carbene complexes were characterized by NMR and UV−vis spectroscopy, mass spectrometry, and elemental analyses. X-ray crystal structure determinations of 1·0.5C₆H₆·0.5CH₂Cl₂ and 4 reveal FeCPh₂ bond lengths of 1.767(3) (1) and 1.827(5) Å (4), together with large ruffling distortions of the TPFPP macrocycle. Complexes 2 and 4 are reactive toward styrene, affording the corresponding cyclopropanes in 82 and 53% yields, respectively. Complex 1 is an active catalyst for both intermolecular cyclopropanation of styrenes with ethyl diazoacetate and intramolecular cyclopropanation of allylic diazoacetates. Reactions of 2 and 4 with cyclohexene or cumene produced allylic or benzylic C−H insertion products in up to 83% yield.