Metal Complexes with Tetrapyrrole Ligands, LV [ 1 ] Improved Syntheses of Oxorhenium(V) Porphyrins and Novel Trichlororhenium(V) Porphyrins

Abstract

The reaction of ReCl5 with a porphyrin H2(P) [2, 3] in refluxing trichlorobenzene represents a very efficient synthesis of oxorhenium(V) porphyrins ReO(P)X where X is a uninegative anion. Thus, rhenium is inserted to octaethylporphyrin and a variety of tetraarylporphyrins. The primary products are the paramagnetic trichlororhenium(V) porphyrins, ReCl3(P), which are remarkably resistant to hydrolysis. If moisture is not rigorously excluded from the metal insertion system, chlorooxorhenium(V) porphyrins ReO(P)Cl are formed which during alumina chromatography are converted to the methoxides ReO(P)OMe. All complexes ReO(P)X and ReCl3(P) are subject to alkaline hydrolysis yielding the μ-oxo complexes [ReO(P)]2O which are convenient starting materials for a variety of mononuclear species ReO(P)X [X = OMe, OEt, OiPr, OtBu, F, Cl, Br, OCIO3, OAc, OBz, OCN, NCS] on acidolysis with a number of monobasic inorganic and organic acids HX or reaction with alkali salts MX in presence of acetic acid. In the case of tetramesitylporphyrin, hydrolysis yields a mononuclear hydroxooxorhenium(V) porphyrin. The species ReCl3(P) and ReO(P)X are characterized by UV/VIS, IR, 1H NMR and mass spectra.