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. 2024 Sep 11;15(1):7943.
doi: 10.1038/s41467-024-52185-w.

Main-group compounds selectively activate natural gas alkanes under room temperature and atmospheric pressure

Runbo Pei #  1   2 , Wenju Chang #  3 , Liancheng He #  1   2 , Tao Wang  1 , Yue Zhao  1 , Yong Liang  4   5 , Xinping Wang  6   7
Affiliations

Main-group compounds selectively activate natural gas alkanes under room temperature and atmospheric pressure

Runbo Pei et al. Nat Commun. .

Abstract

Most C-H bond activations of natural gas alkanes rely on transition metal complexes. Activations by using main-group systems have been reported but required heating or photo-irradiation under high atmospheric pressure with rather low regioselectivity. Here we report that Lewis acid-carbene adducts facilely undergo oxidative additions to C-H bonds of ethane, propane and n-butane with high selectivity under room temperature and atmospheric pressure. The Lewis acids can be moved by the addition of a base and the carbene-derived products can be easily converted into aldehydes. This work offers a route for main-group element compounds to selectively functionalise C-H bonds of natural gas alkanes and other small molecules.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Activation strategies of natural gas C(sp3)–H bonds and small molecules by transition metal or main-group compounds.
a Transition metal complexes activating C(sp3)–H bonds of natural gas alkanes. b Representative examples of activating C–H bonds of natural gas alkanes by main-group compounds. c Representative examples of small molecular activation by main-group compounds. d Reactions of Lewis acid-carbene adducts with C–H bonds of natural gas alkanes. Mes = mesityl; Dipp = 2, 6-diisopropylphenyl; Dur = 2, 3, 5, 6-tetramethylphenyl; ORF = OC(CF3)3.
Fig. 2
Fig. 2. Reactions of Lewis acid-DAC1 adducts with alkanes.
a Reaction of BCF–DAC1 and hexane in benzene. b Reaction of Lewis acid-DAC1 adducts with natural gas alkanes and selected alkane substrates. c The HOMO and LUMO energy of DAC1, BCF–DAC1 and Al(ORF)3–DAC1, computed with B3LYP/6-31 G(d). The yield was determined from crude 1H-NMR spectra and isolated yield in the parenthesis. The structures were all confirmed by single-crystal XRD. ‡ 1H NMR yield (see Supplementary Fig. 48). ORF = OC(CF3)3.
Fig. 3
Fig. 3. Crystal structures.
a The main product from the reaction of BCF-DAC1 with n-hexane; b The product from the reaction of BCF–DAC1 with propane; c Al(ORF)3–DAC1; d The product from the reaction of Al(ORF)3–DAC1 with ethane followed by quenching by addition of CH3CN. ORF = OC(CF3)3. Thermal ellipsoid and stick drawings are set at 30% probability and hydrogen atoms are omitted for clarity. Colour codes: carbon (grey); boron (brown); nitrogen (navy blue); oxygen (red); aluminium (light blue); fluorine (green sticks).
Fig. 4
Fig. 4. DFT-Computed free energies for C–H functionalization of gaseous alkanes with Lewis acid-carbene adducts.
a Reaction of BCF–DAC1 and propane. b The NPA charge of carbon and oxygen atoms in free carbene, adducts and products. c Reaction of Al(ORF)3–DAC1 and ethane. All calculations were carried out at SMD(benzene)-M06-2X/6-311 + G(d,p)//B3LYP-D3/6-31 G(d) level of theory. Most hydrogen atoms are omitted for clarity. All distances are in Å. Colour codes: hydrogen (white); boron (pink); carbon (grey); nitrogen (blue); oxygen (red); fluorine (green); aluminium (tawny).
Fig. 5
Fig. 5. Direct carbonylation of natural gas alkanes without using transition metals and syngas.
a Transformation from n-butane to 2-methylbutyraldehyde. b Transformation from propane to isobutyraldehyde. c Transformation from ethane to propionic aldehyde. d Reaction mechanism of transformation from DAC1-propane to isobutyraldehyde. Yields were determined by 1H-NMR spectra using 1, 3, 5-trimethoxybenzene as internal standard. ORF = OC(CF3)3.
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