| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1999: ¥2,200,000 (Direct Cost: ¥2,200,000)
|
|---|
| Research Abstract |
The metalladichalcogenolene rings in [CpCo(S_2C_2X, Y)]-type complexes are very unique conjugated metal chelate rings which exhibit both aromaticity and unsaturation. Aromaticity is the origin of substitution reactions in electrophilic or radical mechanism, while the unsaturated character of the ring causes addition reactions. The purpose of this study is to elucidate the unique features of quasi-aromatic conjugated metal chelate rings. In this work, we observed the following interesting results.
(1) Reactions due to aromaticity : The reaction of [CpCo(S_2C_2Ph, H)](1) with AIBN brings about the substitution of hydrogens with 1-cyano-1-methylethyl group either in the cobaltadithiolene ring or in the Cp ring. Normally the cobaltadithiolene ring is more reactive for the radical substitution. However, the addition of group 14 element hydride compounds promotes the reaction in the Cp ring (3) and inhibits the reaction in the cobaltadithiolene ring (2). The regio-selectivity (ratio/3 : 2) fo
… More
r the substitution in Cp ring changed in order of Bu_3SnH (100 : 0)>Bu_3GeH (75 : 25)>Bu_3SiH (36 : 64)>Bu_4Sn (32 : 68)>no additive (19 : 81).
In the reaction of the cobaltadithiolene complex [CpCo(S_2C_2Ph, H)] with bis (benzo[d]-1,3-thiazol-2-yl) disulfide under refluxing in benzene, substitutions by sulfur-centered radicals occured selectively in the cobaltadithiolene ring and in that under refluxing in acetonitrile, the product by nitrogen-centered radicals or ions was also observed.
(2) Reactions due to unsaturation : Azides react with [CpCo(S_2C_2Z_2)](Z=COOMe) to form imido-bridged complexes (2-component adducts) between Co and S.The reaction of 2 equivalents of PPh_3 with the p-tolylsulfonylimido-bridged complex showed an interesting reaction which is not observed for the alkylidene-bridged complex. The coordination of PPh_3 with Co at room temperature causes the Co-N bond cleavaged to give an ylide complex (3-component adduct). Upon heating at 80℃ in benzene, the sulfonylimido group migrates from S to the Cp ring. Further, the double migration of the NTs and PPh_3 groups to tha Cp ring from the cobaltadithiolene ring occured in the reaction of excess PPh_3 with the imido-bridged complex.
The coexistence of aromaticity and unsaturation is the origin of unique reactivities or electrochemical behavior of this quasi-aromatic ring. Less
|
