Isolation of [Ru(IPr)2(CO)H]+ (IPr = 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and Reactivity toward E–H (E = H, B) Bonds

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• 作者：Ian M. Riddlestone ; David McKay ; Matthias J. Gutmann ; Stuart A. Macgregor ; Mary F. Mahon ; Hazel A. Sparkes ; Michael K. Whittlesey
• 刊名：Organometallics
• 出版年：2016
• 出版时间：May 9, 2016
• 年：2016
• 卷：35
• 期：9
• 页码：1301-1312
• 全文大小：733K
• 年卷期：0
• ISSN：1520-6041

文摘

Halide abstraction from the ruthenium N-heterocyclic carbene complex Ru(IPr)₂(CO)HCl (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with NaBAr₄^F (BAr₄^F = B{C₆H₃(3,5-CF₃)₂}₄) gave the salt [Ru(IPr)₂(CO)H]BAr₄^F (2), which was shown through a combined X-ray/neutron structure refinement and quantum theory of atoms in molecules (QTAIM) study to contain a bifurcated Ru···η³-H₂C ξ-agostic interaction involving one ⁱPr substituent of the IPr ligand. This system complements the previously reported [Ru(IMes)₂(CO)H]⁺ cation (IMes =1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), where a non-agostic form is favored. Treatment of 2 with CO, H₂, and the amine–boranes H₃B·NR₂H (R = Me, H) gave [Ru(IPr)₂(CO)₃H]BAr₄^F (3), [Ru(IPr)₂(CO)(η²-H₂)H]BAr₄^F (4), and [Ru(IPr)₂(CO)(κ²-H₂BH·NR₂H)H]BAr₄^F (R = Me, 5; R = H, 6), respectively. Heating 5 in the presence of Me₃SiCH═CH₂ led to alkene hydroboration and formation of the C–H activated product [Ru(IPr)(IPr)′(CO)]BAr₄^F (7). X-ray characterization of 3 and 5–7 was complemented by DFT calculations, and the mechanism of H₂/H exchange in 4 was also elucidated. Treatment of 2 with HBcat resulted in Ru–H abstraction to form the boryl complex [Ru(IPr)₂(CO)(Bcat)] BAr₄^F (8), which proved to be competent in the catalytic hydroboration of 1-hexene. In 8, a combined X-ray/neutron structure refinement and QTAIM analysis suggested the presence of a single Ru···η²-HC ξ-agostic interaction.