Preparation and characterization of μ-nitrido diiron phthalocyanines with electron-withdrawing substituents: application for catalytic aromatic oxidation

Abstract

Mu-nitrido-bis [tetra-(hexyl-sulfonyl)phthalocyaninatoiron] (3a) and mu-nitrido-bis [tetra-(tert-butylsulfonyl) phthalocyaninatoiron] (3b) complexes have been prepared and fully characterized by electrospray ionization mass spectrometry, UV-Vis, FTIR, EPR, Mössbauer techniques as well as by X-ray photoelectron and Fe K-edge X-ray absorption spectroscopies. Small changes at the periphery of the phthalocyanine ligand introduce a difference in the iron oxidation state. While 3b with tert-butyl substituents is a neutral complex with a mixed-valence Fe(3.5)-N-Fe(3.5) structural unit, 3a having n-hexyl substituents is an oxidized cationic Fe(IV)-N-Fe(IV) complex. The structural parameters of N-bridged diiron phthalocyanine with a Fe(3.5)-N-Fe(3.5) unit were determined for the first time. Iron atoms in 3b are displaced out of plane by 0.24 A and the Fe-N bond distance of the linear Fe-N-Fe fragment is equal to 1.67 A. Both complexes selectively catalyze benzylic oxidation of alkyl aromatic compounds by tBuOOH. Toluene was oxidized to benzoic acid with 80% selectivity, and the total turnover number was as high as 197. p-Toluic acid was the principal product of p-xylene oxidation. In this case the turnover number achieved 587 substrate molecules per molecule of catalyst. The described catalytic system is complementary to the recently reported system based on mu-nitrido diiron tetrabutylphthalocyanine-H2O2 which effectively oxidizes the benzene ring.

Site-selective formation of an iron(iv)–oxo species at the more electron-rich iron atom of heteroleptic μ-nitrido diiron phthalocyanines

“…μ-Nitrido diiron phthalocyanines belong to the class of stable binuclear single atom bridged complexes that are known to bind metal ions in high oxidation states, 15 although the nature of the reactivity patterns was determined on whether electron-withdrawing or electron-donating substituents on the periphery of the phthalocyanine moieties were added. 16 , 17 These complexes were shown to give a large versatility of chemical and catalytic properties and can adopt Fe III Fe IV and Fe IV Fe IV oxidation states. 18 − 20 The μ-nitrido diiron macrocyclic complexes were found to be able to activate oxygen-atom donors, such as H 2 O 2 and m -chloroperbenzoic acid ( m -CPBA), to form a high-valent diiron–oxo species, i.e.…”

Unexpected formation of a μ-carbido diruthenium(iv) complex during the metalation of phthalocyanine with Ru3(CO)12 and its catalytic activity in carbene transfer reactions

“…The original interest in the µ-carbido complex 2 was fuelled by the observation of the particular catalytic properties of the related µnitrido and µ-oxo complexes. [19][20][21][22][23][24][25] This study represents the first example of the catalytic application of dimeric µ-carbido Ru(IV) phthalocyaninate exemplified by the carbene insertion reactions into olefinic bonds and N-H bonds of amines. Although the catalytic activity is still modest, the results obtained suggest that µ-carbido diruthenium phthalocyanine can be added to the family of catalytically active single-atom bridged bimetallic macrocyclic complexes and might find interesting applications in catalysis.…”

“…However, µ-oxo diiron phthalocyanines were shown to be effective catalysts for the oxidation of aromatic compounds to quinones. 19 In turn, µnitrido diiron phthalocyanine and porphyrin complexes were found to exhibit a rare catalytic activity 20 including oxidation of methane 21 and aromatic compounds, 22 oxidative dechlorination 23 and defluorination 24 as well as the formation of C-C bonds. 25 However, related µ-carbido diiron macrocyclic complexes have never been reported as catalysts for any reaction.…”

Transition metal‐catalyzed oxidative transformations of methylarenes

“…In 2009, Sorokin and co‐workers prepared μ‐nitrido‐bis[tetra(hexylsulfonyl)phthalocyaninatoiron] and μ‐nitrido‐bis[tetra( tert ‐butylsulfonyl)phthalocyaninatoiron] and applied then in catalytic aromatic oxidation (Scheme ) . In this research, in order to estimate the reactivity of the prepared complexes towards aliphatic C–H and aromatic oxidation, toluene was employed and oxidized by TBHP.…”