Synthesis, structure and isomerization of arylphosphoranes with anti-apicophilic bonding modes using a novel bidentate ligand with two C(2)F(5) groups.
A series of anti-apicophilic pentacoordinate phosphoranes (with one chelating substituent in an O-equatorial, C-apical bonding mode at pentacoordinated phosphorus atom) bearing a para-substituted aryl group (-C(6)H(4)(p-X); X = H, CF(3), F, OMe) or a mesityl (2,4,6-trimethylphenyl) group were isolated using a novel bulky bidentate ligand with two C(2)F(5) groups. These phosphoranes were stable to isomerization at room temperature, and quantitatively converted into the corresponding more stable isomers (O-apical) at elevated temperatures in solution. On the basis of a kinetic study, the free energy of activation (DeltaG(double dagger)) of the stereomutation of the O-equatorial mesitylphosphorane to its O-apical isomer was higher than that of the CF(3) derivative by 2.6 kcal mol(-1), giving rise to a further example of the steric effect of the C(2)F(5) group to freeze the isomerization of the pentacoordinate phosphorus compounds. Kinetic measurements of the isomerization of the O-equatorial ortho-unsubstituted derivatives (-C(6)H(4)(p-X)) to the corresponding O-apical isomers suggested that the O-equatorial isomers were stabilized by the pi --> sigma*(P-O) interaction in the ground state.
Jiang
Xin-Dong
XD
Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
Matsukawa
Shiro
S
Yamamoto
Yohsuke
Y
D007536:Isomerism; D007700:Kinetics; D008024:Ligands; D010753:Phosphoranes / Q000138:chemical synthesis* / Q000737:chemistry; D013816:Thermodynamics
D008024:Ligands; D010753:Phosphoranes