Half-Sandwich Silane σ-Complexes of Ruthenium Supported by NHC Carbene

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• 作者：Van Hung Mai ; Ilia Korobkov ; Georgii I. Nikonov
• 刊名：Organometallics
• 出版年：2016
• 出版时间：April 11, 2016
• 年：2016
• 卷：35
• 期：7
• 页码：936-942
• 全文大小：387K
• 年卷期：0
• ISSN：1520-6041

文摘

Reactions of carbene complex [Cp(IPr)Ru(pyr)₂][BF₄] (6, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with excess acetonitrile and LiCl in THF afford complexes [Cp(IPr)Ru(NCCH₃)₂][PF₆] (7) and Cp(IPr)RuCl (8), respectively. Complex 8 was characterized by NMR and X-ray diffraction analysis. Addition of hydrosilanes to 8 results in silane σ-complexes Cp(IPr)Ru(η²-HSiR₃)Cl (4), which were characterized by NMR and X-ray studies of Cp(IPr)Ru(η²-HSiMeCl₂)Cl (4b) and Cp(IPr)Ru(η²-H₃SiPh)Cl (4d). The hydrogen–silicon coupling constants of complexes 4 show an unusual trend in that the J(H–Si) values increase from the less-chlorinated complex Cp(IPr)Ru(η²-HSiMe₂Cl)Cl (4c) to the trichloro derivative Cp(IPr)Ru(η²-HSiCl₃)Cl (4a). Reaction of Cp(IPr)RuCl (8) with two equivalents of HSiCl₃ gave the ruthenate complex [IPrH]⁺[CpRuCl(H) (SiCl₃)₂]⁻, characterized by NMR and X-ray study. Addition of hydrosilanes to the cationic complex [Cp(IPr)Ru(NCCH₃)₂][BAr^F₄] (9) furnished very unstable cationic silane σ-complexes [Cp(IPr)Ru(η²-HSiR₃)(NCCH₃)]⁺ (5), characterized by low-temperature NMR. Reaction of complex 9 with two equivalents of HSiCl₃ gives the neutral bis(silyl) complex CpRu(NCCH₃)(H)(SiCl₃)₂ and [IPrH][BAr^F₄]. Catalytic studies showed that 9 is a poorer catalyst for hydrosilylation of benzaldehyde, benzonitrile, and pyridine than its phosphine analogue [Cp(ⁱPr₃P)Ru(NCCH₃)₂][BAr^F₄]. The reason for this reduced activity was assigned to the easy dissociation of carbene from the former catalyst.