Macgregor Stuart A, Roe D Christopher, Marshall William J, Bloch Karen M, Bakhmutov Vladimir I, Grushin Vladimir V
School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK.
J Am Chem Soc. 2005 Nov 2;127(43):15304-21. doi: 10.1021/ja054506z.
The fluoride congener of Wilkinson's catalyst, [(Ph(3)P)(3)RhF] (1), has been synthesized and fully characterized. Unlike Wilkinson's catalyst, 1 easily activates the inert C-Cl bond of ArCl (Ar = Ph, p-tolyl) under mild conditions (3 h at 80 degrees C) to produce trans-[(Ph(3)P)(2)Rh(Ph(2)PF)(Cl)] (2) and ArPh as a result of C-Cl, Rh-F, and P-C bond cleavage and C-C, Rh-Cl, and P-F bond formation. In benzene (2-3 h at 80 degrees C), 1 decomposes to a 1:1 mixture of trans-[(Ph(3)P)(2)Rh(Ph(2)PF)(F)] (3) and the cyclometalated complex [(Ph(3)P)(2)Rh(Ph(2)PC(6)H(4))] (4). Both the chloroarene activation and the thermal decomposition reactions have been shown to occur via the facile and reversible F/Ph rearrangement reaction of 1 to cis-[(Ph(3)P)(2)Rh(Ph)(Ph(2)PF)] (5), which has been isolated and fully characterized. Kinetic studies of the F/Ph rearrangement, an intramolecular process not influenced by extra phosphine, have led to the determination of E(a) = 22.7 +/- 1.2 kcal mol(-)(1), DeltaH(++) = 22.0 +/- 1.2 kcal mol(-)(1), and DeltaS(++) = -10.0 +/- 3.7 eu. Theoretical studies of F/Ph exchange with the [(PH(3))(2)(PH(2)Ph)RhF] model system pointed to two possible mechanisms: (i) Ph transfer to Rh followed by F transfer to P (formally oxidative addition followed by reductive elimination, pathway 1) and (ii) F transfer to produce a metallophosphorane with subsequent Ph transfer to Rh (pathway 2). Although pathway 1 cannot be ruled out completely, the metallophosphorane mechanism finds more support from both our own and previously reported observations. Possible involvement of metallophosphorane intermediates in various P-F, P-O, and P-C bond-forming reactions at a metal center is discussed.
威尔金森催化剂的氟化物同系物[(Ph(3)P)(3)RhF] (1)已被合成并得到全面表征。与威尔金森催化剂不同，1在温和条件下（80℃反应3小时）能轻易活化ArCl（Ar = Ph，对甲苯基）的惰性C-Cl键，通过C-Cl、Rh-F和P-C键的断裂以及C-C、Rh-Cl和P-F键的形成，生成反式-[(Ph(3)P)(2)Rh(Ph(2)PF)(Cl)] (2)和ArPh。在苯中（80℃反应2 - 3小时），1分解为反式-[(Ph(3)P)(2)Rh(Ph(2)PF)(F)] (3)和环金属化配合物[(Ph(3)P)(2)Rh(Ph(2)PC(6)H(4))] (4)的1:1混合物。氯代芳烃活化反应和热分解反应均通过1向顺式-[(Ph(3)P)(2)Rh(Ph)(Ph(2)PF)] (5)的简便且可逆的F/Ph重排反应发生，5已被分离并得到全面表征。F/Ph重排的动力学研究是一个不受额外膦影响的分子内过程，由此确定了E(a) = 22.7 +/- 1.2 kcal mol⁻¹，ΔH⁺⁺ = 22.0 +/- 1.2 kcal mol⁻¹，以及ΔS⁺⁺ = -10.0 +/- 3.7 eu。对[(PH(3))(2)(PH(2)Ph)RhF]模型体系中F/Ph交换的理论研究指出了两种可能的机制：(i) Ph转移至Rh，随后F转移至P（形式上为氧化加成后再进行还原消除，途径1）和(ii) F转移生成金属膦烷，随后Ph转移至Rh（途径2）。虽然途径1不能完全排除，但金属膦烷机制从我们自己以及先前报道的观察结果中获得了更多支持。本文讨论了金属膦烷中间体在金属中心各种P-F、P-O和P-C键形成反应中的可能参与情况。
