RADICALS CONTAINING BOTH A PHOSPHORANYLIDENE AND A KETONE GROUP - AN ELECTRON-PARAMAGNETIC-RESONANCE ELECTRON-NUCLEAR DOUBLE-RESONANCE STUDY OF THEIR STRUCTURE AND AB-INITIO INVESTIGATIONS ON THE CAPTODATIVE EFFECTS

被引:3
作者
GEOFFROY, M [1 ]
RAO, G [1 ]
TANCIC, Z [1 ]
BERNARDINELLI, G [1 ]
机构
[1] UNIV GENEVA,XRAY CRYSTALLOG LAB,CH-1211 GENEVA,SWITZERLAND
来源
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS | 1993年 / 89卷 / 14期
关键词
D O I
10.1039/ft9938902391
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Single crystals of 2-(triphenylphosphoranylidene)succinic anhydride have been X-irradiated and studied by electron paramagnetic resonance/electron nuclear double resonance (EPR/ENDOR) spectroscopy after determination of their crystal structure. The trapped radical results from the departure of a hydrogen atom bound to a carbon located a to both a C-P and a C-0 bond. The resulting hyperfine coupling tensors are compared with those obtained from ab initio calculations on H3P-CH-CH-CHO (1) and are interpreted in terms of spin delocalization on the succinic anhydride ring. The radical stabilization energies have been calculated for H3P=CH-CH-CHO and H2P-CH2-CH-CHO; they agree with the presence of a captodative effect. Owing to the charge separation caused by the contribution of the mesomeric phosphonium-enolate structure, this effect is more pronounced for the phosphoranylidene compound.
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页码:2391 / 2396
页数:6
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