Three-, four-, and five-coordinate cyclic phosphites, phosphonates, and phosphonium salts containing sulfuryl groups

Reaction of the sulfuryl diphenol O2S[(t-Bu)MeC6H2OH](2) (10) with phosphor us trihalides in the presence of amines yielded the phosphites O2S[(t-Bu)Me C6H2O](2)PR where R = Cl for 1 and R = Br for 2. Treatment of 1 with 2,6-di methylphenol in a halide displacement reaction gave 3 (R = OXyl). In a simi lar diol reaction with O2S[Me2C6H2OH](2) (11), the hydrogenphosphonate O2S[ Me2C6H2O](2)P(O)H (5) formed. A related hydrogenphosphonate O2S[(t-Bu)MeC6H 2O](2)P(O)H (4) was obtained by hydrolysis of either 1 or 2. The phosphoniu m bromide salt O2S[(t-Bu)MeC6H2O](2)PPhBr+Bi- (7) formed from the brominati on of the phenylphosphonite derivative O2S[(t-Bu)MeC6H2O](2)PPh (9), the hy drolysis of which yielded the phosphonate O2S[(t-Bu)MeC6H2O](2)P(O)Ph (6). A related phosphonium bromide O2S [(t-Bu)MeC6H2O](2)PB2+Br- (8) was prepare d by the reaction of the diphenol 10 with PBr3 in the presence of N-bromodi isopropylamine. All of the cyclic phosphorus derivatives 1-8 were character ized by x-ray studies and NMR measurements. All of the compounds lack donor -acceptor interaction that is potentially available via the oxygen atom of the sulfuryl group present as part of the ring system except for 4. For 3, the structure is pentacoordinated with a displacement from a tetrahedral ge ometry toward a trigonal bipyramid, The ring conformation is a syn twist-bo at whereas the others lacking donor coordination reside in an anti chair-li ke ring arrangement. Solution P-31 NMR chemical shifts are in appropriate r anges indicating retention of the coordination geometry that was found in t he solid state. Weak P-Br bond strength is suggested to account for formati on of the phosphonium bromides 7 and 8 which contrasts with the hexacoordin ate structure obtained previously for an analogous chlorophosphorane. Compa risons with similar formulations of cyclic phosphites and phosphates having ring sulfur atoms show that there is a preponderance of donor-acceptor int eractions involving sulfur compared to that experienced with the sulfuryl g roup.