Octahedral Mn(I) complexes bearing tridentate donor ligands [(L^∩L′^∩L′′)(CO)₂MnX] have recently emerged as major players in catalytic (de)hydrogenation processes. While most of these systems are still based on structurally rigid pincer scaffolds imposing a meridional coordination mode, for some more flexible tridentate ligands a facial arrangement of donor moieties becomes possible. Accordingly, the geometry of the corresponding Mn(I) hydrides [(L^∩L′^∩L′′)(CO)₂MnH] directly involved in the catalytic processes, namely the nature of the donor extremity located in the trans-position of the hydride (CO and L for mer- and fac-configurations, respectively) may influence their hydride transfer ability. Herein, low-temperature IR and NMR spectroscopy studies of two model Mn(I) complexes, mer-[(L1)(CO)₂MnH] and fac-[(L2)(CO)₂MnH], bearing similar triphosphine ligands (L1 = PhP(CH₂CH₂PPh₂)₂; L2 = MeC(CH₂PPh₂)₃) in the presence of B(C₆F₅)₃ as the H⁻ abstractor revealed for the first time a higher kinetic hydricity of the tripodal system. Even for the pincer complex, hydride transfer proceeds from the non-covalent adduct fac-[(L1)(CO)₂MnH]⋯B(C₆F₅)₃ with the facial geometry arising from the mer-to-fac isomerization of the initial mer-[(L1)(CO)₂MnH]. The higher reactivity of the fac-hydride derivatives was found to be consistent with the catalytic performance of the corresponding Mn(I) bromide complexes in the benchmark ester hydrosilylation.

中文翻译：

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Mn（I） 氢化物配合物中三磷氢配位几何结构 [（P∩P∩P）（CO）2MnH] 对其动力学水合度的影响


带有三齿供体配体 [（L^∩L′^∩L′′）（CO）₂MnX] 的八面体 Mn（） 配合物最近已成为催化（脱）氢化过程的主要参与者。虽然这些系统中的大多数仍然基于结构刚性的钳式支架，施加经向协调模式，但对于一些更灵活的三齿配体，供体部分的面部排列成为可能。因此，直接参与催化过程的相应 Mn（） 氢化物 [（L^∩L′^∩L′′）（CO）₂MnH] 的几何形状，即位于氢化物反位的供体末端的性质（分别为 CO 和 L 用于 mer 和 fac 构型）可能会影响它们的氢化物转移能力。本文对两种模型 Mn（） 配合物 mer-[（L1）（CO）₂MnH] 和 fac-[（L2）（CO）₂MnH]，具有相似的三磷氢配体（L1 = PhP（CH₂CH₂PPh₂）₂;L2 = MeC（CH₂PPh₂）₃） 在 B（C₆F₅）₃ 作为 H⁻ 抽象器的存在下，首次揭示了三脚体系统的更高动力学水力。 即使对于钳形配合物，氢化物转移也来自非共价加合物 fac-[（L1）（CO）₂MnH]⋯B（C₆F₅）₃，其面部几何形状是由初始 mer-[（L1）（CO）₂MnH] 的 mer-fac 异构化产生的。发现 fac-hydride 衍生物的较高反应性与基准酯氢化硅烷化中相应 Mn（） 溴化物络合物的催化性能一致。