title: Formation, reactivity and redox properties of carbon- and sulfur-bridged diiron complexes derived from dibenzothienyl Schiff bases: effect of N,N- and N,P-chelating moieties.
abstract: Dibenzothienyl Schiff bases, DBT-NN and DBT-NP, were derived from condensation of 4-formyldibenzothiophene with N,N-dimethylethylenediamine and 2-(diphenylphosphino)ethylamine, respectively. A photochemical reaction of [Fe(CO)5] with DBT-NN produced diiron complexes, [Fe2(μ-DBT-NN)(CO)6] (1) and [{Fe(μ-BPT-NN-κ(3)S,C,N)(CO)2}Fe(CO)3] (2). Complex 1 has π coordination of a Schiff base C=N bond and an N,N-chelate, while 2 has an S,C,N-tridentate ligand having an uncoordinated dimethylamino group. The corresponding reaction with DBT-NP produced a diiron complex of an S,C,N,P-tetradentate ligand, [{Fe(μ-BPT-NP-κ(4)S,C,N,P)(CO)}Fe(CO)3] (3), which has an N,P-chelate, via the DBT-NP complex [Fe(DBT-NP-κP)(CO)4] (4). Reactions of 2 and 3 with one equivalent of PMe2Ph gave the monosubstituted complexes [{Fe(μ-BPT-NN-κ(3)S,C,N)(CO)2}Fe(CO)2(PMe2Ph)] (5) and [{Fe(μ-BPT-NP-κ(4)S,C,N,P)(CO)}Fe(CO)2(PMe2Ph)] (6), respectively. The corresponding reactions with an excess of PMe2Ph produced mononuclear complexes, trans-[Fe(BPT-NN-κ(3)S,C,N)(CO)(PMe2Ph)2] (7) and [Fe(BPT-NP-κ(4)S,C,N,P)(CO)(PMe2Ph)] (8), respectively. Complexes 1-3 and 5-8 were structurally characterized by X-ray crystallography. Complexes 2, 3, 5 and 6 have similar dinuclear structures with different carbonyl/phosphine substitution patterns. Cyclic voltammograms of 2, 3 and 5 showed two one-electron reduction processes, and more negative potentials were observed for 6. The shift of the redox potentials are rationalized by the electron-donating character of the phosphine ligands, which suggests that the reduction occurs at the asymmetrically bridged diiron core.
authors.affiliation: Division of Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. mhiro@sci.osaka-cu.ac.jp.
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Santo
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hirotsu
authors.forename: Isamu
authors.initials: I
authors.lastname: Kinoshita
mesh_terms: D002244:Carbon / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D005029:Ethylenediamines / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D010720:Phosphines / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry; D013876:Thiophenes / Q000737:chemistry
chemical_list: D002614:Chelating Agents; D056831:Coordination Complexes; D005029:Ethylenediamines; D010720:Phosphines; D012545:Schiff Bases; D013876:Thiophenes; C027450:dimethylethylenediamine; D013455:Sulfur; D002244:Carbon; D007501:Iron; C016366:dibenzothiophene