Synthesis and Characterization of Stable Hypervalent Carbon Compounds (10-C-5) Bearing a 2,6-Bis(p-substituted phenyloxymethyl)benzene Ligand

Abstract

X-ray analysis of bis(p-fluorophenyl)methyl cation bearing a 2,6-bis(p-tolyloxymethyl)benzene ligand showed a symmetrical structure (10-C-5) where the two C-O distances are identical, although the distance (2.690(4) A) is longer than those (2.43(1) and 2.45(1) A) of 1,8-dimethoxy-9-dimethoxymethylanthracene monocation, which was recently reported by us. However, X-ray analysis of the more stable aromatic xanthylium cation with the same benzene ligand showed the tetracoordinate carbon structure where only one of the two oxygen ligands is coordinated with the central carbon atom. These results clearly indicate that the carbocations (10-C-5) bearing the sterically flexible benzene ligand were quite sensitive to the electronic effect on the central carbon atom. The electron distribution analysis by accurate X-ray measurements and the density functional calculation on the initially mentioned bis(p-fluorophenyl)methyl cation clearly show that the central carbon atom and the two oxygen atoms are bonded even if the bond is weak and ionic based on the small value of the electron density (rho(r)) and the small positive Laplacian value (nabla(2)rho(r)) at the bond critical points.

Stable Pentacoordinate Carbocations: Structure and Bonding

“…Moreover, because the MP2 geometry of 5-Tl has nearly identical C À Tl bond lengths, we decided to include the latter compound in the EDA study by using the shorter MP2 value of the C-Tl interatomic distance (2.431 ) for both bonds. As readily seen from Table 2, the interaction energy between the methyl radical and two EH 2 fragments 3 (1/2 e, q = + + 0.5)…”

“…Under special circumstances it is, however, possible to stabilize it, and compounds 1 and 2, which have been newly isolated by Yamamoto and co-workers are representative examples. [2,3] Very recently, YµÇez and co-workers reported the presence of the D 3h -symmetric molecule ion 3 as a gas-phase ion-molecule reaction product of tetramethylsilane by using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (Scheme 1). [4] This compound can be viewed Abstract: We report that only elements more electropositive than carbon (Group 13, 14, and Be) form stable symmetrical H n E À CH 3 À EH n + structures (E = Group 1, 2, 13, or 14 element) with a planar CH 3 group symmetrically bonded to two EH n moieties, in analogy with prototypical S N 2 transition structures.…”

“…Keywords: bond theory · carbo-A C H T U N G T R E N N U N G cations · energy decomposition · hypervalent compounds · quantum chemistry as a CH 3 + cation interacting with two SiA C H T U N G T R E N N U N G (CH 3 ) 3 radicals. The model implies that the empty p orbital of the sp 2 -hybridized carbon atom interacts with the appropriate singly occupied orbitals of the two SiA C H T U N G T R E N N U N G (CH 3 ) 3 moieties so that the central carbon atom is covalently bonded to the silicon atoms through a three-center, two-electron bond.…”

Synthesis and Structure of a Hexacoordinate Carbon Compound

“…5 A second example with a flexible pincertype ligand followed in 2005. 6 We now report an example of hexacoordinate carbon with arguable hypervalence. Hexacoordinate carbon compounds such as (Ph 3 PAu) 6 C 2+ have been characterized, 7 but orbital analysis does not support hypervalence.…”

“…6 We now report an example of hexacoordinate carbon with arguable hypervalence. Hexacoordinate carbon compounds such as (Ph 3 PAu) 6 C 2+ have been characterized, 7 but orbital analysis does not support hypervalence. Indeed, most high-coordinate carbon compounds are obviously electron-deficient, having three-center two-electron (3c-2e) bonds.…”