Theoretical design of hexacoordinate hypervalent carbon compounds by analyzing substituent effects

A hexacoordinate hypervalent carbon compound with an ideal octahedral structure was proposed theoretically in a previous study (Chem. Phys. Lett. 2008, 460, 37). However, there is no report telling of success in synthesizing the compound and/or its derivatives. In order to perform a theoretical design for stronger hypervalent bonds, the present study systematically investigated the substituent effects at the para position of phenyl groups of axial C-C and equatorial C-O bonds by adopting 14 functional groups involving both electron-donating and -withdrawing groups. The results showed that the substituent effect at the former position is more influential than that at the latter. In the former case, a good correlation between the C-C and C-O distances is found and the hypervalent C-O bonds are strengthened as the substituent becomes more electron-withdrawing. In the latter case, both electron-donating and -withdrawing groups slightly weaken the hypervalent C-O bonds.