Internal Alkyne Isomerization to Vinylidene versus Stable π-Alkyne: Theoretical and Experimental Study on the Divergence of Analogous Cp*Ru and TpRu Systems
作者:Vinay K. Singh、Emilio Bustelo、Isaac de los Ríos、Ignacio Macías-Arce、M. Carmen Puerta、Pedro Valerga、Manuel Ángel Ortuño、Gregori Ujaque、Agustí Lledós
DOI:10.1021/om200273v
日期:2011.8.8
The activation of internal alkynes by Cp*Ru and TpRu complexes gives respectively pi-allyne and disubstituted vinylidene as stable species, even though both systems bear identical pyridylphosphine ligands (kappa P-2,N- (Pr2PXPy)-Pr-i, X = NH, CH2, S). The activation of the alkynones PhC CCOR (R = Me, Ph) by [TpRuCl((Pr2PXPy)-Pr-i)] complexes allowed us to isolate and characterize metastable eta(1)-O=C(R)C CPh adducts. These complexes isomerize spontaneously to vinylidene both in solution and in the solid state. Kinetic studies have been carried out in solution by P-31H-1} NMR and in the solid state by IR spectroscopy, providing the Eyring and Avrami-Erofeev parameters, respectively. The activation of internal alkynes without ketone groups provided vinylidene species as well, but without isolable intermediates. In contrast with the TpRu system, the activation of alkynones by [Cp*RuCl((Pr2PXPy)-Pr-1)] always results in stable pi-alkyne species. Representatives of both Cp*Ru-pi-alkyne; and TpRu-vinylidene compounds have been characterized by X-ray diffraction. DFT calculations have been carried out with the actual experimental complexes, including solvent effects, in order to analyze the mechanism of the pi-alkyne to vinylidene isomerization Of internal alkynes and to explain the divergent results obtained for Tp and Cp*.