A Highly Reactive Ruthenium Phosphido Complex Exhibiting Ru−P π-Bonding

Multiple bonding in the terminal phosphido complex [Ru(PCy2)(η5-indenyl)(PPh3)] (2a) is clearly demonstrated by solution, solid-state, and computational studies. Reactions of this dark blue, half-sandwich complex with CO, MeI, HNEt3Cl, HCl, NH4PF6, H2, and Et3SiH demonstrate an unusual range of behavior resulting from combined coordinative unsaturation at Ru, high nucleophilicity/basicity of the phosphido P, and π-character of the Ru−P interaction. The terminal, π-bound phosphido structure is general for a range of PR2 species (R = Pri (2b), Ph (2c), Tolp (2d)). The very reactive diarylphosphido analogues 2c,d have been observed spectroscopically at low temperatures and can be trapped quantitatively as their CO adducts, [Ru(PAr2)(η5-indenyl)(CO)(PPh3)] (3c,d), in which the Ru−P bond order is reduced to 1. Complex 2a and its analogue [Ru(PPri2)(η5-indenyl)(PPh3)] (2b) are consistently isolated with ∼15% of their structural isomers, the ruthenium hydrido phosphaalkenes 9a,b, resulting from an apparent 1,2-H shift.

溶液相、固态及计算研究均清晰证实了末端膦化物配合物[Ru(二环己基膦基(dicyclohexylphosphino, PCy₂))(η⁵-茚基(η⁵-indenyl))(三苯基膦(triphenylphosphine, PPh₃))]（2a）中存在多重成键。该深蓝色半三明治配合物与一氧化碳（carbon monoxide, CO）、碘甲烷（methyl iodide, MeI）、三乙胺盐酸盐（triethylamine hydrochloride, HNEt₃Cl）、氯化氢（hydrogen chloride, HCl）、六氟磷酸铵（ammonium hexafluorophosphate, NH₄PF₆）、氢气（hydrogen, H₂）及三乙基硅烷（triethylsilane, Et₃SiH）的反应，展现出一系列反常的反应行为，这源于钌中心的配位不饱和性、膦化物磷原子的高亲核性/碱性，以及Ru-P相互作用的π轨道特性。这种末端π配位的膦化物结构，对于一系列PR₂型配体（R = 异丙基(isopropyl, Pri)、苯基(phenyl, Ph)、对甲苯基(p-tolyl, Tolp)）具有普适性。活性极高的二芳基膦化物类似物2c、2d可在低温下通过光谱手段观测到，并能以一氧化碳加合物[Ru(二芳基膦基(diarylphosphino, PAr₂))(η⁵-茚基(η⁵-indenyl))(CO)(PPh₃)]（3c、3d）的形式被定量捕获，该加合物中Ru-P键级被降至1。配合物2a及其类似物[Ru(二异丙基膦基(diisopropylphosphino, PPri₂))(η⁵-茚基(η⁵-indenyl))(PPh₃)]（2b）在分离时，总会伴随约15%的结构异构体——氢化膦烯合钌9a、9b——生成，该异构体源于明显的1,2-氢迁移(1,2-H shift)过程。