HEXACOORDINATION VIA SULFUR DONOR ACTION IN BICYCLIC PENTAOXYPHOSPHORANES

New bicyclic oxyphosphoranes, S[(t-Bu)MeC6H2O](2)P(OC6H5)(O2C6H3F) (1) and S[(t-Bu)MeC6H2O](2)P(OC6H5)(O2C6H4) (3), were synthesized by disp lacement reactions of a monocyclic pentaoxyphosphorane by a diol, and S[(t-Bu)(2)C6H2O](2)P(OCH2CF3)(O2C6Cl4) (2) and S[(t-Bu)(2)C6H2O](2)P( C6H5)(O2C6Cl4) (4), by oxidative addition reactions of a phosphite or: phosphine with tetrachlorobenzoquinone. X-ray studies revealed hexacoo rdinated structures formed by the presence of a sulfur donor atom inco rporated in a flexible eight-membered ring. The structures were displa ced along a coordinate from a square pyramid toward an octahedron. P-3 1 and H-1 NMR data are also reported. Comparisons are made between bic yclic tetraoxyphosphoranes and monocyclic and bicyclic pentaoxyphospho ranes which show the importance of ligand electronegativity in increas ing the degree of hexacoordination. Of the various series now studied, the extent of sulfur donor atom coordination increases in the followi ng order: phosphates < phosphites < oxyphosphoranes. It is concluded t hat, in general, sulfur donor atom coordination will take place with p hosphorus in any of the common coordination geometries in the presence of sufficiently electronegative ligands.