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 N 2C(Ph)R (R = Ph, CO 2Et, CO 2CH 2CH=CH 2) afforded [Fe(TPFPP)(C(Ph)R)] (R = Ph (1), CO 2Et (2), CO 2CH 2CH=CH 2 (3)) in 65-70% yields. Treatment of 1 with N-methylimidazole (Melm) gave the adduct [Fe(TPFPP)(CPh 2)(Melm)] (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 1·0.5C 6H 6·0.5CH 2Cl 2 and 4 reveal Fe=CPh 2 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.