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ISSN 1998-9539

Iron Complexes of Octaphenyltetraazaporphine

Pavel A. Stuzhin


Department of Organic Chemistry, Ivanovo State University of Chemical Technology, RF-153000, Ivanovo, Russia




This review is dedicated to my teacher Professor B. D. Berezin on occasion of his 80th birthday and considers the results obtained during investigation of iron octaphenyltetraazaporphyrin complexes (FeOPTAP), which was initiated by his suggestion. Although synthesis and some catalytic properties of FeOPTAP have being mentioned already in the pioneering works of Linstead and Cook [J. Chem. Soc. 1937, 929-933; 1938, 1761-1780, 1845-1847] this species was not characterised and its coordination chemistry remained unknown. We have shown that template condensation of diphenylfumarodinitrile with Fe(CO)5 in boiling 1-bromonaphthalene affords the crude bromoiron(III) complex [(Br)FeOPTAP] which can be easily converted in a number of various coordination forms with different oxidation and spin state of iron. This complex and other five-coordinated acido complexes [(X)FeOPTAP] (X – anion of a strong inorganic or carboxylic acid) contain iron(III) in the intermediate spin state S = 3/2. Treatment of [(X)FeOPTAP] with N-bases L or anionic nucleophiles A‑ (e.g. OH-, OR, CN-, SCN-, OCN-, N3) in non-coordinating solvents with low dielectric constant (benzene or CHCl3) leads first to mixed six-coordinated complexes ([(L)(X)FeOPTAP] or [(A)(X)FeOPTAP]‑) and then to cationic or anionic low-spin (S = 1/2) iron(III) species ([(L)2FeOPTAP]+ or [(A)2FeOPTAP]‑). In solvents with higher dielectric constant and/or donor properties (acetone, dimethylsulfoxide, etc) iron(III) is reduced to iron(II) with formation of diamagnetic six-coordinate iron(II) complexes [(L)2FeOPTAP] or [(A)2FeOPTAP]2-. Heating of [(L)2FeOPTAP] in vacuum affords four-coordinated intermediate spin (S = 1) iron(II) complex [(L)2FeOPTAP] which is easily oxidised in air to the binuclear μ-oxodiiron(III) complex μ-O[FeOPTAP]2. This species is also easily obtained from [(X)FeOPTAP] during chromatography on neutral or basic Al2O3. Treatment of μ-O[FeOPTAP]2 with acid HX leads to [(X)FeOPTAP] and with N-base L to μ-O[(L)FeOPTAP]2 which is then reduced to [(L)2FeOPTAP]. μ-Nidrido diiron(III½) complex μ‑N[FeOPTAP]2 which is formed from the azide derivative [(N3)FeOPTAP] upon refluxing in benzene can form an adduct with N-bases and bind O2. Reactive nitridocomplex [N≡FeOPTAP] containing most likely iron(V) was shown to be the key intermediate in the formation of μ-nitrido complexes and heteroleptic and heterometallic μ-nitrido species μ‑N(FeOPTAP)(FeTPP) and [μ‑N(FeOPTAP) (MnOPTAP)] were also described. Treatment of [(X)FeOPTAP] with CI4 under reductive conditions or with CHCl3 in alkali media leads to the μ-carbido complex μ‑C[FeOPTAP]2. Results of spectral study (UV-vis, IR, 1H NMR, ESR and Mössbauer), investigation of redox and ligand binding/exchange reactions are also reviewed.

MHC2009_t02n02_114-129.pdf1.65 MB