TY - JOUR
T1 - Formation of a New, Strongly Basic Nitrogen Anion by Metal Oxide Modification
AU - Tamura, Masazumi
AU - Kishi, Ryota
AU - Nakayama, Akira
AU - Nakagawa, Yoshinao
AU - Hasegawa, Jun Ya
AU - Tomishige, Keiichi
N1 - Funding Information:
This work was supported by JST PRESTO Grant Numbers JPMJPR15S5 and JPMJPR16S8, Japan. Part of the calculations were performed on supercomputers at RCCS (Okazaki, Japan), RIIT (Kyushu University), and ACCMS (Kyoto University).
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/8/30
Y1 - 2017/8/30
N2 - Development of new hybrid materials having unique and unprecedented catalytic properties is a challenge for chemists, and heterogeneous-homogeneous hybrid catalysts have attracted much attention because of the preferable and exceptional properties that are highly expected to result from combination of the components. Base catalysts are widely used in organic synthesis as key materials, and a new class of base catalysts has made a large impact from academic and industrial viewpoints. Here, a principle for creating a new strong base by hybridization of homogeneous and heterogeneous components is presented. It is based on the modification of organic compounds with metal oxides by using the acid-base property of metal oxides. Based on kinetic and DFT studies, combination of CeO2 and 2-cyanopyridine drastically enhanced the basicity of 2-cyanopyridine by a factor of about 109 (∼9 by pKa (in CH3CN)), and the pKa was estimated to be ∼21, which locates it in the superbase category. 2-Cyanopyridine and CeO2 formed a unique adsorption complex via two interaction modes: (i) coordinative interaction between the Ce atom of CeO2 and the N atom of the pyridine ring in 2-cyanopyridine, and (ii) covalent interaction between the surface O atom of CeO2 and the C atom of the CN group in 2-cyanopyridine by addition of the lattice oxygen of CeO2 to the CN group of 2-cyanopyridine. These interactions established a new, strongly basic site of N- over the CeO2 surface.
AB - Development of new hybrid materials having unique and unprecedented catalytic properties is a challenge for chemists, and heterogeneous-homogeneous hybrid catalysts have attracted much attention because of the preferable and exceptional properties that are highly expected to result from combination of the components. Base catalysts are widely used in organic synthesis as key materials, and a new class of base catalysts has made a large impact from academic and industrial viewpoints. Here, a principle for creating a new strong base by hybridization of homogeneous and heterogeneous components is presented. It is based on the modification of organic compounds with metal oxides by using the acid-base property of metal oxides. Based on kinetic and DFT studies, combination of CeO2 and 2-cyanopyridine drastically enhanced the basicity of 2-cyanopyridine by a factor of about 109 (∼9 by pKa (in CH3CN)), and the pKa was estimated to be ∼21, which locates it in the superbase category. 2-Cyanopyridine and CeO2 formed a unique adsorption complex via two interaction modes: (i) coordinative interaction between the Ce atom of CeO2 and the N atom of the pyridine ring in 2-cyanopyridine, and (ii) covalent interaction between the surface O atom of CeO2 and the C atom of the CN group in 2-cyanopyridine by addition of the lattice oxygen of CeO2 to the CN group of 2-cyanopyridine. These interactions established a new, strongly basic site of N- over the CeO2 surface.
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U2 - 10.1021/jacs.7b05227
DO - 10.1021/jacs.7b05227
M3 - Article
C2 - 28753288
AN - SCOPUS:85028636674
SN - 0002-7863
VL - 139
SP - 11857
EP - 11867
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 34
ER -