硼酸化
化学
催化作用
选择性
多相催化
产量(工程)
氢化物
碳氢化合物
甲烷氧化偶联
光化学
组合化学
无机化学
有机化学
金属
烷基
材料科学
芳基
冶金
作者
Orion Staples,Magali Ferrandon,Guillaume Laurent,Uddhav Kanbur,A. Jeremy Kropf,Michael R. Gau,Patrick J. Carroll,Katherine E. McCullough,Dieter Sorsche,Frédéric A. Perras,Massimiliano Delferro,David M. Kaphan,Daniel J. Mindiola
摘要
Catalytic C-H borylation is an attractive method for the conversion of the most abundant hydrocarbon, methane (CH4), to a mild nucleophilic building block. However, existing CH4 borylation catalysts often suffer from low turnover numbers and conversions, which is hypothesized to result from inactive metal hydride agglomerates. Herein we report that the heterogenization of a bisphosphine molecular precatalyst, [(dmpe)Ir(cod)CH3], onto amorphous silica dramatically enhances its performance, yielding a catalyst that is 12-times more efficient than the current standard for CH4 borylation. The catalyst affords over 2000 turnovers at 150 °C in 16 h with a selectivity of 91.5% for mono- vs diborylation. Higher catalyst loadings improve yield and selectivity for the monoborylated product (H3CBpin) with 82.8% yield and >99% selectivity being achieved with 1255 turnovers. X-ray absorption and dynamic nuclear polarization-enhanced solid-state NMR spectroscopic studies identify the supported precatalyst as an IrI species, and indicate that upon completion of catalysis, multinuclear Ir polyhydrides are not formed. This is consistent with the hypothesis that immobilization of the organometallic Ir species on a surface prevents bimolecular decomposition pathways. Immobilization of the homogeneous IrI fragment onto amorphous silica represents a unique and simple strategy to improve the TON and longevity of a CH4 borylation catalyst.
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