Departamento de Química Inorgánica, Instituto de Síntesis QuímicayCatálisis Homogénea-ISQCH, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009, Zaragoza, Spain.
Chemistry. 2018 Nov 27;24(66):17545-17556. doi: 10.1002/chem.201803878. Epub 2018 Nov 5.
The reactions of the rhodium(I) and iridium(I) complexes [M(PhBP )(C H )(NCMe)] (PhBP =PhB(CH PPh ) ) with alkynes have resulted in the synthesis of a new family of pseudo-tetrahedral complexes, [M(PhBP )(RC≡CR')] (M=Rh, Ir), which contain the alkyne as a four-electron donor. The reactions of these unusual compounds with two-electron donors (L=PMe , CNtBu) produced a change in the "donicity" of the alkyne from a 4e to a 2e donor to give five-coordinate complexes. These were the final products with the iridium complexes, whereas further reactions took place with the rhodium complexes. In particular, C(sp)-H bond activation of the alkyne occurred leading to hydrido alkynyl complexes. This process is essential for the further reactivity of the alkynes, and if the alkyne itself was used as reagent, E-enyne complexes were obtained. As a consequence of this chemistry, we show that the complex [Rh(PhBP )(C H )(NCMe)] is a very efficient pre-catalyst for the regioselective di- and trimerization of terminal alkynes to E-enynes and benzene derivatives, respectively. Interestingly, acetonitrile significantly enhanced the catalytic activity by facilitating the C(sp)-H bond activation step. A hydrometalation mechanism to account for these experimental observations is proposed.
铑（I）和铱（I）配合物[M(PhBP)(CH)(NCMe)]（PhBP=PhB(CH PPh ) ）与炔烃的反应导致了一类新型的拟四面体配合物[M(PhBP)(RC≡CR')]（M=Rh，Ir）的合成，其中炔烃作为四电子供体。这些不寻常化合物与双电子供体（L=PMe ，CNtBu）的反应导致炔烃的“给电性”从 4e 变为 2e 供体，生成五配位配合物。这些是与铱配合物的最终产物，而与铑配合物则发生了进一步的反应。特别是，炔烃的 C(sp)-H 键活化导致了氢代炔基配合物的形成。这一过程对于炔烃的进一步反应至关重要，如果炔烃本身被用作试剂，则得到 E-烯炔配合物。由于这种化学性质，我们证明了配合物[Rh(PhBP)(CH)(NCMe)]是末端炔烃区域选择性二聚和三聚为 E-烯炔和苯衍生物的非常有效的预催化剂。有趣的是，乙腈通过促进 C(sp)-H 键活化步骤显著提高了催化活性。提出了一个氢金属化机制来解释这些实验观察结果。
