Jain Anant Kumar, Gau Michael R, Carroll Patrick J, Goldberg Karen I
Department of Chemistry, University of Pennsylvania Philadelphia Pennsylvania 19104 USA
Chem Sci. 2022 Jun 20;13(26):7837-7845. doi: 10.1039/d2sc00279e. eCollection 2022 Jul 6.
Syntheses of Vaska-type complexes [IrPX(CO)] (P = phosphine, X = halide) with all four common halides (fluoride, chloride, bromide, and iodide) was attempted using a protic and hemilabile imidazolyl di--butyl phosphine ligand. In the solid-state, all four complexes were found to be ionic with the halides in the outer-sphere, and the fourth coordination site of the square plane occupied by the imidazole arm of the ligand. In solution, however, the chloride complex was found to be in equilibrium with an octahedral Ir-H species at room temperature. For the bromide and iodide analogs, the corresponding Ir-H species were also observed but only after heating the solutions. The neutral Ir Vaska's analogs for X = Cl, Br, and I were obtained upon addition of excess halide salt, albeit heating was required for X = Br and I. The Ir-H species are proposed to originate from tautomerization of minor amounts of the electron rich neutral Vaska analog (halide inner-sphere and phosphines monodentate) that are in equilibrium with the ionic species. Heating is required for the larger anions of bromide and iodide to overcome a kinetic barrier associated with their movement to an inner-sphere position prior to tautormerization. For the fluoride analog, the Ir-H was not observed, attributable to strong hydrogen bonding interactions of the imidazolyl proton with the fluoride anion.
尝试使用质子化且具有半不稳定性质的咪唑基二丁基膦配体合成含有所有四种常见卤化物（氟化物、氯化物、溴化物和碘化物）的瓦卡型配合物[IrPX(CO)]（P = 膦，X = 卤化物）。在固态下，发现所有四种配合物都是离子型的，卤化物处于外层球，平面正方形的第四个配位位点被配体的咪唑臂占据。然而，在溶液中，发现氯化物配合物在室温下与八面体Ir-H物种处于平衡状态。对于溴化物和碘化物类似物，相应的Ir-H物种也被观察到，但仅在加热溶液之后。通过加入过量的卤化物盐得到了X = Cl、Br和I的中性Ir瓦卡类似物，不过对于X = Br和I需要加热。提出Ir-H物种源自与离子物种处于平衡状态的少量富电子中性瓦卡类似物（卤化物在内层球且膦为单齿）的互变异构。对于较大的溴离子和碘离子阴离子，需要加热以克服与它们在互变异构之前移动到内层球位置相关的动力学障碍。对于氟化物类似物，未观察到Ir-H，这归因于咪唑基质子与氟离子之间强烈的氢键相互作用。
