The mechanism of the Ru-assisted C-C bond cleavage of terminal alkynes by water

被引:168
作者
Bianchini, C
Casares, JA
Peruzzini, M
Romerosa, A
Zanobini, F
机构
[1] Ist. per Stud. Stereochimica E.C.C., CNR, 50132, Firenze
关键词
D O I
10.1021/ja9601393
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The hydration of phenylacetylene in the presence of the complex mer, trans-(PNP)RuCl2(PPh(3)) in THF at 60 degrees C leads to the cleavage of the C-C triple bond with formation of the carbonyl complex fac, cis-(PNP)RuCl2(CO) and toluene [PNP=CH3CH2CH2N(CH(2)CH(2)PPh(2))(2)]. A study under different experimental conditions, the use of model and isotope labeling experiments, and the detection of several intermediates, taken altogether, show that the C-C bond cleavage reaction comprises a number of steps, among which the most relevant to the mechanism are 1-alkyne to vinylidene tautomerism, conversion of a vinylidene ligand to hydroxycarbene by intramolecular attack of water, deprotonation of hydroxycarbene to sigma-acyl, deinsertion of CO from the acyl ligand, and hydrocarbon elimination by protonation of the metal-alkyl moiety. The following intermediate species have been isolated and characterized: the vinylidene fac,cis-(PNP)RuCl2{C=C(H)Ph}, the (aquo)(sigma-alkynyl) complex fac-(PNP)RuCl(C=CPh)(OH2), and the (benzyl)carbonyl mer-(PNP)RuCl(eta(1)-CH(2)Ph)(CO). Other intermediates such as the sigma-acyl mer-(PNP)RuCl(eta(1)-COCH(2)Ph)(CO) have been intercepted by addition of appropriate reagents, while the independent synthesis of the aminocarbene complex fac, cis-(PNP)RuCl2{C(NC5H10)(CH(2)Ph)} and its reaction with water have provided evidence for the intermediacy of a hydroxycarbene species in the C-C bond cleavage reaction.
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页码:4585 / 4594
页数:10
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