Laboratory for Molecular Design: Inorganic Material
Science of Coordination Compounds and Clusters

http://www.materials.sci.osaka-cu.ac.jp/SEKKEI/index_e.htm

Current Research and Principal Research Interests
Selected Publications

1. Current Research and Principal Research Interests
My research interest is in the area of synthetic chemistry of functional organometallic andcoordination compounds. Research projects currently in progress involve the synthetic study oforganometallic oxide clusters and photosensitive crystalline-state complexes and developmentof artificial sulfur cycle on M-M bonds.
Organometallic oxide clusters which have cubic, incomplete cubic and valley site frameworks
are useful as homogeneous and heterogeneous catalysts in the oxidation and metathesis of
unsaturated hydrocarbons. We have synthesized several organometallic oxide clusters with thelatter frameworks, for example the triple cubic [(Cp*Rh)4Mo4O16] (Cp* = η5-C5Me5), theincomplete double cubic [(Cp*Rh)2Mo3O9(OMe)4], the double bookshelf[(Cp*Rh)2Mo6O20(OMe)2]2- type oxide clusters and so on. These clusters are formed by thecondensation of oxometalate anions on the Lewis acidic Cp*Rh moiety, which is able to provide
three coordination sites for the condensation.

Artificial sulfur cycle on M-M bonds. Oxidation is an important part of most sulfur cycles andsulfur chemistry in general. In the oceanic thermal vents, it was reported that H2S is released
and then oxidized to SO42-, which then settles back to the vent to be reduced back to H2S. Also,
some bacteria perform a stepwise conversion of organic disulfides into RSO3H. Herein, we willreport a strictly inorganic oxidation of an μ-S2 rhodium complex [{Cp*Rh(μ-CH2)}2(μ-S2)]
which is derived from several steps starting at the reaction of trans-[{Cp*Rh(μ-CH2)}2Cl2] with
H2S. From the oxidation reaction, the mono-[μ-SS(O)], bis-[μ-SS(O)2 and μ-S(O)S(O)] andtetra-[μ-S(O)2S(O)2] oxygenated species have been isolated and characterized. Preliminary 1 H
NMR data suggests that the oxidation process, like the oxidation of organic disulfides, mayhappen in a stepwise fashion. Tetra-[μ-S(O)2S(O)2] oxygenated species is oxidized further with
O2 to give SO3 and SO4 complexes under irradiation of light. Mechanistic details of theoxidation reaction as well as attempts to reduce the oxide complexes are under progress.

2. Selected Publications
1. "Structure and Reactivity of a Novel Parallel Thiosulfito (SSO2-S,S') Rhodium Dinuclear
Complex", K. Shiomi, B. K. Breedlove, H. Kitayama, T. Nishioka, I. Kinoshita, N. Koga and K.
Isobe, Chem. Commun., 2002, 1756-1757.
2. "Direct Observation by Electrospray Ionization Mass Spectrometry of [Cp*RhMo3O8(OMe)5]-, a Key Intermediate in the Formation of the Double-Bookshelf-Type Oxide Cluster[(Cp*Rh)2Mo6O20(OMe)2]2-", S.Takara, S.Ogo, Y. Watanabe, K. Nishikawa, I. Kinoshita and
K. Isobe, Angew. Chem. Int. Ed., 38, 3051-3053 (1999).
3. "Tetranuclear Mo2Rh2 Complexes Obtained from Reactions between Triple Cubane- type
Oxide Cluster [(Cp*Rh)4Mo4O16] (Cp* = η5-C5(CH3)5) and Methanethiol: [{Cp*Rh(μSCH3)3MoO2}2(μ-O)] and [{Cp*Rh(μ-SCH3)33MoO}2(μ-X)(μ-Y)] (X, Y = O and X = O, Y =S). Synthesis, X-ray Structures, and Dynamic Behavior in Nonaqueous Media", R. Xi, B. Wang,
M. Abe, Y. Ozawa, I. Kinoshita and K. Isobe, Bull. Chem. Soc. Jpn., 72, 1985-1996 (1999).

4. "Reactions of Terminal and Bridging Thiol Di-μ-methylene Dirhodium Compleses with
Alkynes to Afford the Corresponding Ethenethiolate Complexes. Remarkable C- C bondFormation between Two μ-CH2 and Alkynes on the Bridging Ethenethiolate Complexes", Y.
Kaneko, N. Suzuki, A. Nishiyama, T. Suzuki and K. Isobe, Organometallics, 17, 4875-4883(1998).
5. "Structures, Bonding and Reactivity of M-S-M' (M and M' = Rh, W, and Cu) Groups inHigher-Nuclearity Heterometallic Sulfide Clusters", S. Ogo, T. Suzuki, Y. Ozawa and K. Isobe,
Inorg. Chem., 35, 6093-6101 (1996).
6. "[{Rh2Cp*2(μ-CH2)2}2(μ-S4)]2+: A Novel Tetranuclear Cationic Complex with a Rectangular
S4 Unit", K. Isobe, Y. Ozawa, A. Vázquez de Miguel, T.-W. Zhu, K.-M. Zhao, T. Nishioka, T.
Ogura and T. Kitagawa, Angew. Chem. Int. Ed. Engl., 33, 1882- 1883 (1994).
7. "Cubane-Type Clusters as Potential Models for Inorganic Solid Surfaces", K. Isobe and A.
Yagasaki, Acc. Chem. Res., 26, 524-529 (1993).
8. "Site-selective Oxygen-exchange and Substitution of Organometallic Groups in an
Amphiphilic Quadruple-Cubane-Type Cluster. Synthesis and Molecular Structure of[(MCp*)4V6O19](M = Rh, Ir)", Y. Hayashi, Y. Ozawa and K. Isobe, Inorg. Chem., 30,
1025-1033 (1991).
9. "Novel Triple Cubane-Type Organometallic Oxide Clusters: [MCp*MoO4]4•nH2O (M = Rh
and Ir; Cp* = C5Me5: n = 2 for Rh and O for Ir)", Y. Hayashi, K. Toriumi and K. Isobe, J. Am.
Chem. Soc., 110, 3666-3668 (1988).
10. "trans-Bromo(2-, 3-, and 4-pyridyl)bis(trietylphosphine)palladium(II) Complexes", K. Isobe,
E. Kai, Y. Nakamura, K. Nishimoto, T. Miwa, S. Kawaguchi, K. Kinoshita and K. Nakatsu, J.
Am. Chem. Soc., 102, 2475-2476 (1980).