Synthesis and Electrochemistry of Iron-Pyrylium Complexes

Abstract

The syntheses and characterization of three cationic iron-pyrylium complexes (2 +, [2-OMe-3-Fp-5,6-Ph2(C5HO)]+; 3 +, [2-OMe-3-Fp-6-Ph(C5H2O)]+; 4 +, [2-OMe-3-Fp‘-6-Ph (C5H2O)]+) that result from the sequential addition of methyl propiolate and PhC⋮CR (R = Ph, H) to FpBF4 (Fp = η5-C5H5(CO)2Fe) or Fp‘PF6 (Fp‘ = η5-(C5H4Me)(CO)2Fe) are presented. The initially formed cationic Fp-methyl propiolate complex is shown to convert into a complicated mixture that includes the corresponding vinylidene and alkynyl complexes. The iron-pyrylium complexes have been characterized by 1H NMR and IR spectroscopy, elemental analysis, FAB-MS, electrochemical, and fiber-optic-IR and ESR spectroelectrochemical techniques. These metal-pyrylium complexes undergo electron transfer at the pyrylium ring rather than at the metal center. The subsequent chemistry of the neutral species 2 • , 3 • , and 4 • is strongly influenced by the nature of the substituents on the ring. The sterically protected complex 2 + undergoes chemically and electrochemically reversible reductions. The complexes 3 + and 4 + undergo dimerization reactions after reduction presumably through the 4-position of the pyrylium ring.

Retooling Manganese(III) Porphyrin-Based Peroxynitrite Decomposition Catalysts for Selectivity and Oral Activity: A Potential New Strategy for Treating Chronic Pain

“…The general procedures and apparatus for the electrochemistry experiments have been previously reported. 81 …”

“…UV–vis spectra were recorded using an Ocean Optics Red Tide UV–vis Spectrometer. The general procedures and apparatus for the electrochemistry experiments have been previously reported …”

“…The general procedures and apparatus for the electrochemistry experiments have been previously reported. 81 Mn(III)-TCHP Chloride (7). A mixture of TCHP (100 mg, 0.19 mmol) in CHCl 3 /MeOH (3:1, 60 mL) was treated with MnCl 2 (362 mg, 2.88 mmol) and 2,6-lutidine (1 mL).…”

Bis(metallaethynyl) Ketones: Synthesis and Structure of {(Ph3P)AuC≡C}2CO and Attempted Transmetalation: Formation and Structure of [1,3-{Ru(dppe)Cp}2{c-COC(OMe)CHCCH}]PF6

“…The 1 H and 13 C NMR spectra showed the expected peaks for the ancillary ligands, together with a singlet at δ H 5.05 assigned to the C(4) proton. The OMe group resonates at δ H 2.58 and δ C 54.78, the former being at a field considerably higher than that found in related compounds Fe{c-CCHCR 1 CPhCC(OMe)}(CO) 2 Cp R (R = H, R 1 = H, Ph; R = Me, R 1 = H), in which the OMe group lies between the Fe and pyrylium O atoms . The C(2) H signal falls within the aromatic region, as do the resonances for C(2,4), which lie between δ C 127 and 143.5.…”

“…Other ferrocenyl derivatives are known . Cationic manganese and iron complexes have been described, , while (η 5 -pyranyl)Mn(CO) 3 and 2-ferrocenylpyrylium cations have been obtained from cyclomanganated chalcones and alkynes . A platinum(II) complex containing a related carbenoid ligand, cis -PtCl 2 (PPh 3 ){c-CC(CO 2 Et)CPhC(CO 2 Et)CPhO}, was obtained from PtCl 2 (CO) 2 and PhCCCO 2 Et, followed by reaction with PPh 3 , and is the only complex of this type which has been structurally characterized …”