176 Journal of Inorganic Biochemistry 96 (2003)

Iron- Nitrosyl Sulfinate Complexes: Relevance to the Fe-Containing Nitrile Hydratases

Chien-Minrr Lee, Department of Chemistry, National Tsing Hua University, Taiwan Chien-Hong Chen, Department of Chemistry, National rSing Hua University, Taiwan Chung-Hung Hsieh, Department of Chemistry, National Tsing Hua University, Taiwan Amitava Dutta, Department of Chemistry, National Tsing Hua University, Taiwan Gene-Hsiang Lee, Instrumentation Centel; National Taiwan University, Taiwan

Iron-NO complex containing monosulfinate [(NO)Fe(S,SO,-C,H,)(S,S-ChHd)Js (3) has been isolated from sulfur oxygenation of complex [(NO)Fe(S,S-C,H,),]- (2) which is obtained from addition of NO molecule to [(C,H,O)Fe(S,S-C,H,),]- (1), in organic solvents. In contrast, complex 1 does not initiate any 0, activation to yield iron-sulfinate/-sulfenate complex. This result reveals that binding of NO to the iron center is required in promoting oxygenation of iron-bound dithiolates by dioxygen to yield iron-sulfinate-nitrosyl species. Analysis of the bond angles for complexes 2 and 3 reveals that iron is best described as existing in a distorted trigonal bipyramidal coordination environment surrounded by one NO, three thiolates, and one sulfinate in complex 3, whereas the distorted square pyramidal geometry is adopted in complex 2. Complex 3 further reacts with molecular oxygen in the presence of [NO,]- to produce dinuclear bis(sulfinate) [PPN],[(NO)Fe(SO,,SO,- C,H,)(S,S-C,H,)], (4). Complex 3 showed reaction with PPh,in THF/CH,Cl, to yield complex 2 and Ph,PO. Extrusion of [0] atoms from complex 3 was also observed on photolysis of CI-&Cl, solutions of complex 3 under N, at ambient temperature. Obviously, complex 3 is thermally quite stable but is photochemically active toward [0] release.

Novel Mononuclear Fe(II1) Mono(terpyridine) Complexes Having Labile Solvent Ligands: A Comparison of Homegeneous vs. Heterogeneous Catalytic Activity

Jin-Kvu Lee, School of Chemistry, Seoul National Universi& Korea Cheal Kim, Department of Fine Chemistry, Seoul National University, Korea Dong-Woo Yoo, School of Chemistry, Seoul National University, Korea Sang-Kun Yoo, Department ofFine Chemistry, Seoul National University, Korea

We have been exploring to find the new active mononuclear nonheme iron complexes having at least one open coordination site that is vacant or occupied by a solvent molecule to allow the room for exogenous ligands to bind during the catalytic reaction. Although a handful of examples have been recently isolated as mononuclear nonheme Fe(IIl)-OH complexes by introducing sterically bulky substituents, electrochemically well studied Fe poly(pyridy1) complexes have been hardly investigated for catalytic applications probably due to the lack of synthetic methods for preparing coordinatively unsaturated one. A new polymer-bound Fe(III)-terpyridine complex (PCD-Fe(tpy)) (l), which may have three additional water and/or methanol ligands, was obtained from the reaction of polymer supporter PCD, potassium carbonate and 2,6-bis(2’-pyridyl)-4’-(p-hydroxyphenyl)pyridine. This polymer-supported catalyst 1 has shown an excellent catalytic activity on the ring-opening reaction of various epoxides by water and alcohol under mild and neutral conditions to give stereospecific (trans-1,2-diol or trans-1,2-diol mono-ether) and relatively regioselective products where the nucleophile is incorporated preferentially to the more substituted carbon center in epoxide ring. The catalytic method appears to be an efficient, mild, and simple method for the alcoholysis of epoxides and to be useful to prepare more substituted-ether alcohol, which might be exploited immediately for the practical synthesis of a wide range of interesting 1,2-diol mono-ethers. Moreover, the catalyst 1 could be easily recovered by a simple filtration and be used repeatedly without any significant change from original catalytic activity even when used consecutively over 20 times. Furthermore, the catalytic system has the advantages such as availability and environment-friendly nontoxicity of the reagent, ease of workup and catalyst recycling, and the excellent conversion of epoxide into 1 ,Zdiol mono-ether could make it as a promising candidate for a useful addition to the present methodologies in organic synthesis. We will also discuss a comparison ofhomogeneous vs. heterogeneous catalytic activity for [(terp)FeIII(S),] and catalyst 1.