|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1996 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1995 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1994 : ¥1,100,000 (Direct Cost : ¥1,100,000)
The nucleophilic attack of trival ent phosphorus compounds (Z_3P) on an electrophilic center has been believed to proceed in a single-step. However, it has become well known that Z_3P acts as an electron donor, which means that the reaction could take place with a multi-step mechanism including an initial electron transfer (SET) from Z_3P to the electrophile.
As a first attempt to inspect if such a mechanism is valid, the author examined chemical property of a putative intermediate, trivalent phosphorus cation radical. Thus, trivalent phosphorus compounds (Z_3P) were reacted with an electron acceptor such as acridinium salts in the photoexcited state, diazonium salts, or methylviologen in the presence of water or alcohol, and the products were analyzed. The results showed that the caution radicals generated during the reactions principally undergo ionic reactions with water or alcohol, but when a free-radical is present in the reaction system, radical coupling between the cation radical and the free-radical also takes place competitively.
Moreover, the author examined the photoreaction of ruthenium (II) complex with Z_3P,and found that Z_3P acts either as an electron donor or as a nucleophile in this photoreaction, resulting in the reduction of the ruthenium complex through SET and the ligand exchange, respectively. Kinetic analysis of the photoreaction gave the rate constants for the SET and the ligand exchange individually. The logarithm of the rate constant for SET showed an excellent correlation with oxidation potential of Z_3PP.On the other hand, the logarithm of the rate constants for the ligand exchange well correlated with a linear combination of an electronic parameter and a steric parameter of Z_3P.Thus, the rate constants for the SET and the ligand exchange exhibited correlations with independent parameters, which suggests that an electron donor ability and a nucleophilc one of Z_3P are independent.