Theoretical investigation of boron-doped lithium clusters, BLin (n = 3–6), activating CO2: an example of the carboxylation of C–H bonds. Issue 87 (5th September 2016)

• Record Type: Journal Article
• Authors: Ma, Jing-Feng; Ma, Fang; Zhou, Zhong-Jun; Tao Liu, Ying
• Is Part Of: RSC advances. Volume 6:Issue 87(2016)
• Page Start: 84042
• Page End: 84049
• Publication Date: 2016-09-05
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c6ra15152c
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Boron-doped lithium clusters BLi n activating CO2 is reported. And the carboxylation of C–H bond of benzene can be achieved through C–C bond formation and H-atom-transfer from C to O via two H2 O molecules acting as an H-transfer tunnel. Abstract : This work reports the first example of boron-doped lithium clusters, BLi n, activating CO2 . The investigation shows that a kind of novel BLi n –CO2 ( n = 2–6) complex (I n ) with bidentate double oxygen M(η2 -O2 C) coordination is obtained through the bimetal 2Li of BLi n clusters binding to the two O atoms of CO2, and the structural integrities of BLi n clusters are not destroyed. We find that the partial negative charge transfer from BLi n to the π* orbital of CO2 leads to weakening of the CO bonds of CO2 and an active CO2 moiety, except for when n = 2. Further, we perform reactions betweenI n ( n = 3–6) and benzene to elucidate a novel alternative approach to direct carboxylation by inserting CO2 into C–H bonds. We find that the carboxylation of the C–H bond of benzene can be achieved through the transition states (TS) of C–C bond formation and H-atom-transfer from C to O via two H2 O molecules acting as a H-transfer tunnel. Comparing the transition states of H-direct transfer and one H2 O molecule assisting H transfer, two H2 O molecules assisting H-transfer as a tunnel is shown to lower the barrier, due to this long H-bond bridge effectively easing the rotation of the dihedral angle between the C6 H6 and CO2 moiety planes. Considering the whole free energy profile, BLi5 and BLi6 clusters are more feasible for the carboxylation of C–H bonds.