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Evidence for Charge-Shift Bonding in [1.1.1]Propellanes C5H6 and E5Me6 (E = Si, Ge, Sn): A Theoretical Investigation

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journal contribution
posted on 09.12.2013, 00:00 by Congjie Zhang, Lichao Ning, Jinxia Li
Using density functional theory, the structures and stability of [1.1.1]­propellanes C5H6 and E5Me6 (E = Si, Ge, Sn), as well as their dianions have been studied. Calculated results showed that the energy of Sn5Me62– is lower than that of Sn5Me6. In contrast, C5H62– and E5Me62– (E = Si, Ge) are electronically unstable, which successfully explains the experimental results of the reactions of E5R6 (E = Ge, Sn) with [FeCp­(CO)2]2 and [RuCp­(CO)2]2. Furthermore, FeCp­(CO)2 and CH3 groups were introduced to capture the covalent resonance structures of C5H6 and E5Me6. Additionally, the ionic resonance structures of C5H6 and E5Me6 were captured by the strongly electron donating group (HCNMe)2C: and electron accepting group (AgCl) simultaneously. Hence, the “inverted” C–C and E–E bonds in [1.1.1]­propellanes C5H6 and E5Me6 are covalent–ionic mixes. Together with their electron density and Laplacian values, direct evidence for the charge-shift bonding of the inverted C–C (C5H6) and E–E bonds (E5Me6) was presented.