Physical Organic Chemistry of Transition Metal Complexes. 31.

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• 作者：Claude F. Bernasconi and Mahammad Ali
• 刊名：Organometallics
• 出版年：2004
• 出版时间：December 20, 2004
• 年：2004
• 卷：23
• 期：26
• 页码：6134 - 6139
• 全文大小：146K
• 年卷期：v.23,no.26(December 20, 2004)
• ISSN：1520-6041

文摘

Rate constants for the attachment of CH(CN)₂^- to Fischer carbene complexes of the type(CO)₅M=C(XR)C₆H₄Z with M = Cr, W and XR = OMe, OEt, SMe in 50% MeCN-50% water(v/v) at 25 C are reported. The malononitrile anion shows a much higher reactivity towardthese carbene complexes than OH^-, primary aliphatic amines (e.g. n-butylamine), orsecondary alicyclic amines (e.g. piperidine) but is slightly less reactive than thiolate ions(e.g. HOCH₂CH₂S^-). The alkoxycarbene complexes react more quickly than the thiomethylderivatives, consistent with previous findings for alkoxide ion, OH^-, amine, and thiolateion nucleophiles. Hammett values are 0.69 for the reaction with (CO)₅Cr=C(SMe)C₆H₄Zand 2.88 for the reaction with (CO)₅Cr=C(OMe)C₆H₄Z. The much larger value for themethoxycarbene complexes fits a pattern observed previously with other nucleophiles andcan be explained by the -donor effect of the methoxy group, which is much stronger thanthat of the thiomethyl group.