A Deeper Look into Thiophene Coordination Prior to Oxidative Addition of the C−S Bond to Platinum(0): A Computational Study Using DFT and MO Methods

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• 作者：T&#xfc ; lay A. Ateş ; in ; William D. Jones
• 刊名：Organometallics
• 出版年：2008
• 出版时间：January 14, 2008
• 年：2008
• 卷：27
• 期：1
• 页码：53 - 60
• 全文大小：1686K
• 年卷期：v.27,no.1(January 14, 2008)
• ISSN：1520-6041

文摘

The reaction of thiophene with a zerovalent platinum bisalkylphosphine fragment yields a highly stable thiaplatinacycle derived from cleavage of the C−S bond. Calculations on the [Pt(dmpe)] model system using Density Functional Theory are consistent with experimental results obtained with [Pt(dippe)] in that the reaction is exothermic overall and furthermore predict that the initial b7;²-coordination of thiophene through the Cbs.acs.org/images/entities/dbd_2.gif">C double bond is energetically more favorable than coordination through the sulfur atom (ΔG = 9.3 kcal/mol). There are three well-defined transition states along the pathway to the oxidative addition product from both of these coordination modes. Two of these lead to a higher energy b7;²-C,S-coordinated intermediate, while the third one leads to cleavage of the C−S bond from the b7;²-C,S complex. As the reaction was carried out in a polar solvent (THF), the effect of solvation was taken into account by using the polarizable continuum model. The thermodynamic preference for the initial coordination of thiophene through the Cbs.acs.org/images/entities/dbd_2.gif">C bond is found to be greater in THF (ΔG = 11.4 kcal/mol). More importantly, the total free energy of the transition state from the Cbs.acs.org/images/entities/dbd_2.gif">C coordinated complex is now lower than that of the S-coordinated complex in solution. Therefore, the initial b7;²-coordination of thiophene through the Cbs.acs.org/images/entities/dbd_2.gif">C double bond results in the kinetically preferred pathway. Molecular orbital analyses were carried out to rationalize the results.