Sulfonyl-Containing Eight-Membered Rings Varying in Ring Conformation in Oxyphosphoranes. Hexacoordination vs Pentacoordination1

Abstract

The new cyclic phosphine O2S[(t-Bu)MeC6H2O]2PPh (1) was used to prepare the new cyclic tetraoxyphosphoranes O2S[(t-Bu)MeC6H2O]2PPh(O2C6Cl4) (2) and O2S[(t-Bu)MeC6H2O]2PPh(O2C6H4) (3) by oxidative addition reactions. In similar reactions, the new cyclic pentaoxyphosphoranes O2S[(t-Bu)MeC6H2O]2P(OCH2CCl3)3 (4), O2S[Me2C6H2O]2P(OPh)3 (5), and O2S[(t-Bu)MeC6H2O]2P(OC6F5)3 (6) were formed from acyclic phosphites and the appropriate diol. Yields ranged from 51% to 66%. X-ray studies revealed hexacoordinated representations for 2 and 6 while 3−5 are pentacoordinate in trigonal bipyramidal geometries. For 3 and 4, the eight-membered rings are positioned diequatorially in anti chair conformations, whereas for 5, this ring occupies axial−equatorial sites in a syn twist-boat form. Tetraoxyphosphorane 3 is unique in locating the least electronegative ligand, the phenyl group, in an axial position. Oxygen donor action from the sulfone SO2 group led to a displacement from a square pyramid to an octahedron to the extent...