Picolyl–NHC Hydrotris(pyrazolyl)borate Ruthenium(II) Complexes: Synthesis, Characterization, and Reactivity with Small Molecules

Ruthenium­(II)
hydrotris­(pyrazolyl)­borate chloro complexes bearing picolyl-functionalized
N-heterocyclic carbenes [TpRu­(κ2-C,N-picolyl-RI)­Cl] (picolyl-MeI = 3-methyl-1-(2-picolyl)­imidazol-2-ylidene)
(1a), picolyl-iPrI = 3-isopropyl-1-(2-picolyl)­imidazol-2-ylidene
(1b), picolyl-Me45DClI =
3-methyl-1-(2-picolyl)-4,5-dichloroimidazol-2-ylidene (1c), picolyl-PhI = 3-phenyl-1-(2-picolyl)­imidazol-2-ylidene
(1d), picolyl-MeBI = 3-methyl-1-(2-picolyl)­benzoimidazol-2-ylidene
(1e)) have been synthesized and characterized. Furthermore,
cationic carbonyl derivatives 2a–e have been prepared, characterized, and used to study the donor properties
of the picolylcarbene ligands (picolyl-RI) via infrared spectroscopy.
Also, the reactivity of the 16-electron species [TpRu­(κ2-C,N-picolyl-RI)]+, in situ generated using NaBArF4 (ArF = 3,5-bis­(trifluoromethyl)­phenyl) as
a halide scavenger, toward N2, CH3CN, H2, CH2CH2, S8, and O2 was studied indicating a strong influence of the NHC wingtip and
backbone substituents in the product distribution. The crystal structures
of [TpRu­(κ2-C,N-picolyl-iPrI)­Cl] (1b),
[TpRu­(κ2-C,N-picolyl-MeI)­CO]­[BArF4] (2a), [TpRu­(κ2-C,N-picolyl-PhI)­CO]­[BArF4] (2d), [{TpRu­(κ2-C,N-picolyl-MeI}2(μ-N2)]­[BArF4]2 (3′a), [{TpRu­(κ2-C,N-picolyl-PhI)}2(μ-N2)]­[BArF4]2 (3′d), [TpRu­(κ2-C,N-picolyl-iPrI)­(η2-CH2CH2)]­[BArF4] (5b), and [{TpRu­(κ2-C,N-picolyl-MeI)}2(μ-S2)]­[BArF4]2 (6) are reported.

本研究合成并表征了一系列带有吡啶甲基功能化氮杂环卡宾(N-heterocyclic carbenes, NHC)的氢化三(吡唑基)硼酸根(hydrotris(pyrazolyl)borate, 缩写Tp)合钌(II)氯配合物[TpRu(κ²-C,N-picolyl-RI)Cl]，其中picolyl-MeI对应3-甲基-1-(2-吡啶甲基)咪唑-2-亚基（对应配合物1a），picolyl-iPrI对应3-异丙基-1-(2-吡啶甲基)咪唑-2-亚基（1b），picolyl-Me45DClI对应3-甲基-1-(2-吡啶甲基)-4,5-二氯咪唑-2-亚基（1c），picolyl-PhI对应3-苯基-1-(2-吡啶甲基)咪唑-2-亚基（1d），picolyl-MeBI对应3-甲基-1-(2-吡啶甲基)苯并咪唑-2-亚基（1e）。此外，本研究还制备并表征了阳离子羰基衍生物2a–e，并通过红外光谱研究了此类吡啶甲基卡宾配体(picolyl-RI)的给电子性能。另外，以NaBArF4（ArF = 3,5-双(三氟甲基)苯基）作为卤离子清除剂原位生成的16电子物种[TpRu(κ²-C,N-picolyl-RI)]+，针对氮气(N2)、乙腈(CH3CN)、氢气(H2)、乙烯(CH2CH2)、单质硫(S8)与氧气(O2)的反应活性被系统探究，结果表明氮杂环卡宾的翼式取代基与骨架取代基对产物分布具有显著调控作用。本文还报道了如下配合物的晶体结构：[TpRu(κ²-C,N-picolyl-iPrI)Cl]（1b）、[TpRu(κ²-C,N-picolyl-MeI)CO][BArF4]（2a）、[TpRu(κ²-C,N-picolyl-PhI)CO][BArF4]（2d）、[{TpRu(κ²-C,N-picolyl-MeI)}2(μ-N2)][BArF4]2（3′a）、[{TpRu(κ²-C,N-picolyl-PhI)}2(μ-N2)][BArF4]2（3′d）、[TpRu(κ²-C,N-picolyl-iPrI)(η²-CH2CH2)][BArF4]（5b）以及[{TpRu(κ²-C,N-picolyl-MeI)}2(μ-S2)][BArF4]2（6）。