Electron-Poor Rhenium Allenylidenes and Their Reactivity toward Phosphines: A Combined Experimental and Theoretical Study

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• 作者：Cecilia Coletti ; Luca Gonsalvi ; Antonella Guerriero ; Lorenza Marvelli ; Maurizio Peruzzini ; Gianna Reginato ; Nazzareno Re
• 刊名：Organometallics
• 出版年：2012
• 出版时间：January 9, 2012
• 年：2012
• 卷：31
• 期：1
• 页码：57-69
• 全文大小：543K
• 年卷期：v.31,no.1(January 9, 2012)
• ISSN：1520-6041

文摘

The reaction of 1-(phenyl)-1-(p-nitrophenyl)-2-propyn-1-ol with the Re(I) precursor [(triphos)(CO)₂Re(OTf)] in dichloromethane at 0 掳C afforded the cationic allenylidene complex [(triphos)(CO)₂Re{C鈺怌鈺怌(C₆H₅)(p-C₆H₄NO₂)}]⁺ (3) as a dark burgundy red triflate salt after solvent evaporation. The reaction of 3 with 1.2 equiv of the phosphine PMePh₂ at 鈭?0 掳C led first to the 纬-phosphonioalkynyl complex [(triphos)(CO)₂Re{C鈮CPh(p-C₆H₄NO₂)(PMePh₂)}]⁺ (5) (observed as a pair of distinct rotamers, 5a,b) and then, on slow increase of the temperature to 0 掳C, to the 伪-phosphonioallenyl complex [(triphos)(CO)₂Re{C(PMePh₂)鈺怌鈺怌Ph(p-C₆H₄NO₂)}]⁺ (6). On the other hand, the reaction of 3 with the more nucleophilic PMe₃ at 鈭?0 掳C led to its complete transformation into a compound, suggested to be the 伪-phosphonioallenyl derivative [(triphos)(CO)₂Re{C(PMe₃)鈺怌鈺怌(C₆H₅)(p-C₆H₄NO₂)}]⁺ (7). To study the effect due to the strongly electron withdrawing p-nitrophenyl substituent on the allenylidene geometry, electronic structure, and reactivity with phosphines, we performed theoretical calculations on 3 and other hypothetical p-nitro-substituted allenylidenes as well as on the products and plausible intermediates of its reaction with PMe₃ and PMePh₂. Finally, theoretical methods were applied to shed light on the nature of the two rotamers observed for the 纬-phosphonioalkynyl complex 5.