Difluorovinylidene, F₂CC:

Abstract

An alkyne–vinylidene isomerization is also possible with the difluoro compounds 1 and 2! Irradiation of 2 (λ = 193 nm) in an Ar matrix yields 1 exclusively. The IR spectrum agrees with results of novel abinitio calculations, which also suggest that 1—in sharp contrast to the vinylidenes RHCC—is protected against isomerization into 2 by a kinetic barrier. Irradiation with light with λ > 230nm converts 1 back into 2. Already at 35–42 K 1 adds CO and N2 to yields F2CCCO and F2CCNN, respectively.

Anharmonic force fields from analytic CCSD(T) second derivatives: HOF and F2O

“…48 The numerical precision of the anharmonic force constants obtained from this procedure depends on three factors, 4 i.e., the precision of the optimized equilibrium geometry, the step size in the finite difference scheme, and the precision of the analytic second derivatives. Concerning the first two points, general considerations, 4 and previous experience 4, [16][17][18][19] require the maximum absolute gradient component g max to be less than 10 Ϫ6 a.u. and suggest step sizes ⌬q between 0.01 and 0.05.…”

A Structurally Characterized Fluoroalkyne

“…[22c] As ac onsequence of this high barrier to isomerization to its parent alkyne,d ifluorovinylidene can be observed in low temperature matrices. [23] Curiously,t his stability has not resulted in an extensive chemistry of difluorovinylidene as al igand, indeed the only examples are in dimeric complexes prepared through defluorination reactions. [24] Using OSEF methodology, [6,7] thefluoroalkynyl ligand in 3 may be readily converted into ad ifluorovinylidene.…”

A Structurally Characterized Fluoroalkyne

“…136 kJ mol −1 ) than the hydrogen‐containing analogues, which is believed to be due to the antiaromatic transition state for fluorine migration and the commensurate requirement to cleave a C−F bond . As a consequence of this high barrier to isomerization to its parent alkyne, difluorovinylidene can be observed in low temperature matrices . Curiously, this stability has not resulted in an extensive chemistry of difluorovinylidene as a ligand, indeed the only examples are in dimeric complexes prepared through defluorination reactions…”