Peñas-Defrutos Marconi N, Bartolomé Camino, García-Melchor Max, Espinet Pablo
IU CINQUIMA/Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, 47071 Valladolid, Spain.
School of Chemistry, CRANN and AMBER Research Centres, Trinity College Dublin, College Green, D02 PN40 Dublin 2, Ireland.
Inorg Chem. 2025 Jul 14;64(27):13729-13739. doi: 10.1021/acs.inorgchem.5c01081. Epub 2025 Jun 26.
In contrast with the previously reported decelerating effect of added L (L = AsPh) on the Rf/Pf exchange reaction between [Au(Pf)L] and -[Rh(Rf)(CO)L] (Pf = CF; Rf = CFCl-3,5), the Rf/Cl exchange between [AuClL] and -[Rh(Rf)(CO)L] is accelerated by addition of an excess of L. By combining experimental data and microkinetic modeling, with DFT calculations, the unexpected existence of two cooperative Rf/Cl exchange mechanisms is demonstrated. The opposite kinetic effects of L addition, from negative in the Rf/Pf exchange process, opposing L dissociation in an octahedral rhodium intermediate, to positive in the Rf/Cl exchange, opening an L-catalyzed alternative pathway via tricoordinate gold intermediates, explain the Janus effect of AsPh. The three transmetalation pathways involve a metal redox-insertion step with accessible activation barrier, producing intermediates with Rh-Au bonds. Whereas our previously reported Rf/Pf exchange implied Rh(I) oxidation by Au(I), the Rf/Cl exchange mechanism involves Au(I) oxidation by Rh(I). Further support is provided by NBO studies, which reveal remarkable electronic donations from the oxidized metal in each case forging the M-M' covalent interaction in the intermediates yielded by the redox-insertion step.
与之前报道的添加L（L = AsPh）对[Au(Pf)L]与-[Rh(Rf)(CO)L]之间Rf/Pf交换反应的减速作用相反（Pf = CF；Rf = CFCl-3,5），添加过量的L会加速[AuClL]与-[Rh(Rf)(CO)L]之间的Rf/Cl交换。通过结合实验数据和微动力学模型以及密度泛函理论（DFT）计算，证明了两种协同的Rf/Cl交换机制的意外存在。添加L的相反动力学效应，从Rf/Pf交换过程中的负效应（在八面体铑中间体中阻碍L解离）到Rf/Cl交换中的正效应（通过三配位金中间体开辟L催化的替代途径），解释了AsPh的两面神效应。这三种金属转移途径都涉及一个具有可及活化能垒的金属氧化还原插入步骤，生成具有Rh-Au键的中间体。虽然我们之前报道的Rf/Pf交换意味着Au(I)氧化Rh(I)，但Rf/Cl交换机制涉及Rh(I)氧化Au(I)。自然键轨道（NBO）研究提供了进一步的支持，该研究揭示了在每种情况下氧化态金属都有显著的电子给予，从而在氧化还原插入步骤产生的中间体中形成M-M'共价相互作用。
