Synthesis and Redox Properties of (3-Phenothiazinomesityl)- and (4-Phenothiazinoduryl)dimesitylphosphines and the Corresponding Arsines
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- 作者：Shigeru Sasaki ; Fumiki Murakami ; and Masaaki Yoshifuji
- 刊名：Organometallics
- 出版年：2006
- 出版时间：January 2, 2006
- 年：2006
- 卷：25
- 期：1
- 页码：140 - 147
- 全文大小：156K
- 年卷期：v.25,no.1(January 2, 2006)
- ISSN：1520-6041
文摘
To construct the novel redox systems possessing the trimesitylphosphine- or trimesitylarsine-typesubstructure as a reversible redox site, dimesityl(3-phenothiazinomesityl)phosphine, dimesityl(4-phenothiazinoduryl)phosphine, and the corresponding arsines were synthesized (mesityl = 2,4,6-trimethylphenyl, duryl = 2,3,5,6-tetramethylphenyl). The key synthetic intermediates, (3-bromomesityl)dimesitylphosphine, (4-bromoduryl)dimesitylphosphine, and the analogous arsines were prepared bysuccessive addition of the corresponding Grignard reagents to phosphorus or arsenic trichloride. The(bromoaryl)phosphines and -arsines were converted to the corresponding (iodoaryl)phosphines and -arsinesand coupled with phenothiazine in the presence of copper to afford the phenothiazinophosphino- andphenothiazinoarsinobenzenes. The cyclic voltammograms of the phenothiazinopnictogenobenzenes thusobtained exhibit two-step redox waves corresponding to oxidation on the pnictogen as well as phenothiazineredox centers. The phenothiazino group contributes to stability of the redox systems, and thephenothiazinophosphinobenzenes display two-step nearly reversible redox waves at -78 
C. On the otherhand, the cyclic voltammograms of the phenothiazinoarsinobenzenes consist of the first reversible wavefollowed by the second irreversible wave, suggesting decomposition at the unstable arsenic redox center.The pnictogen redox centers of the phenothiazinopnictogenobenzenes are unstable as compared withthose of the corresponding trimesityl derivatives. Chemical oxidation of the phenothiazinophosphinobenzenes and phenothiazinoarsinobenzenes by tris(4-bromophenyl)aminium perchlorate, which can oxidizetrimesitylphosphine and trimesitylarsine to the corresponding cation radicals, was studied by EPR.However, only the nitrogen-centered cation radical was observed probably because of the instability ofthe phosphorus as well as arsenic radical centers.
C. On the otherhand, the cyclic voltammograms of the phenothiazinoarsinobenzenes consist of the first reversible wavefollowed by the second irreversible wave, suggesting decomposition at the unstable arsenic redox center.The pnictogen redox centers of the phenothiazinopnictogenobenzenes are unstable as compared withthose of the corresponding trimesityl derivatives. Chemical oxidation of the phenothiazinophosphinobenzenes and phenothiazinoarsinobenzenes by tris(4-bromophenyl)aminium perchlorate, which can oxidizetrimesitylphosphine and trimesitylarsine to the corresponding cation radicals, was studied by EPR.However, only the nitrogen-centered cation radical was observed probably because of the instability ofthe phosphorus as well as arsenic radical centers.