Formation reactions of phosphorus ylide–tetracyanoquinodimethane complexes

The Study of HOMO Energy for Showing the Basicity and the v (C=O) Stretching Bands Obtained by the Semi-Empirical and ab initio Methods in Phosphorus Ylides

“…We already found that there is a linear relationship between the rate constant, log k and pKa [13]. When the linear relationship is represented by the form log k = m(pKa) + c, the values of m and c are 0.43 and -1.77 at 50 C, 0.43 and -1.87 at 40 C, and 0.43 and -1.99 at 30 C, respectively.…”

“…This result indicates that the contribution of resonance structure IIb is large in ylides. In addition, the ν(C=O) stretching bands of ylides in the charge-transfer complexes shifted to high frequency (30-60 cm -1 ) [13]. This shift shows the interaction with TCNQ and the ylide bond.…”

“…This result indicates that the electron density of the donor molecule plays an important role in the formation of charge-transfer complexes. The substituent effect was also examined by the Hammett method [13]. In this case, the range of reaction constants (ρ) is from -1.06 to -1.17.…”

“…As the basicity on the ylide carbon (anionic carbon) of phosphorus ylides is controlled by substituents on ylide carbon, the correlation between pKa of the phosphorus ylide as the donor and the formation of the phosphorus ylide-TCNQ chargetransfer complex was studied. The linear relationship between the reaction rate in the formation of charge-transfer complexes and pKa of the ylides was reported [13].…”

“…[II] The structural requirement for a phosphorus ylide is that it contains an anionic carbon attached to a phosphorus atom which carries a high degree of positive charge. Thus, ylides have electronically unique characteristics because of the specific structures and are known to be electron donors [1][2][3][4][5][6][7][8][9][10][11][12][13].…”