| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 1992: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1991: ¥5,500,000 (Direct Cost: ¥5,500,000)
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| Research Abstract |
Photo- and electrochemical CO_2 reductions catalyzed by transition metal complexes have widely been investigated so far. The products in those homogeneous reactions, however, are limited to CO and/or HCOOH. The purpose of this project is to explore multi-electron reduction of CO_2 accompanied by carbon-carbon bond formation in electrochemical CO_2 reduction catalyzed by metal complexes. Isolation and the molecular structures by X-ray analysis for [Ru(bpy)_2(CO)_2]^<2+>, [Ru(bpy)_2(CO)(C(O)OH)]^+, and [Ru(bpy)_2(CO)(CO_2)] (bpy = 2,2'- bipyridyl) have revealed the mechanism for the formation of CO and HCOOH in the electro- and photochemical CO_2 reduction catalyzed by those complexes. Furthermore, the reaction of NaBH_4 with [Ru(bpy)_2(CO)_2]^<2+> at -20ﾟC to produce [Ru(bpy)_2(CO)(C(O)H)]^+, which is further reduced to [Ru(bpy)_2(CO)(CH_2OH)]^+ in the presence of excess of BH_<4-> at room temperature. From a point of view that both [Ru(bpy)_2(CO)(C(O)H)]^+ and [Ru(bpy)(trpy)(C(O)H)]^+ (trpy = terpyridyl) are quite labile at room temperature, electrochemical CO_2 reduction catalyzed by [Ru(bpy)(trpy)(CO)]^<2+> at -20ﾟC stabilizes the formyl intermediates, and CO_2 is catalytically reduced to not only HC(O)H and CH_3OH as the two- and four-electron reduction products but also HO(O)CC(O)H and HO(O)CCH_2OH as C2 products.Thus, [Ru(bpy)(trpy)(CO)]^<2+> has an ability to catalyze the multi-electron reduction accompanied by carbon-carbon bond formation in electrochemical CO_2 reduction.
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