title: Chloro- and Fluoro-Substituted Phosphites, Phosphates, and Phosphoranes Exhibiting Sulfur and Oxygen Coordination(1).
abstract: New cyclic phosphoranes, O(2)S[Me(t-Bu)C(6)H(2)O](2)PCl(3) (1), O(2)S[Me(t-Bu)C(6)H(2)O](2)P(OC(6)H(4)-m-CF(3))(3) (2), and O(2)S[(t-Bu)(2)C(6)H(2)O](2)PCl(3) (3), containing sulfone donor groups and halogen substituents were synthesized by oxidative addition reactions of a diol with a tricoordinated phosphorus precursor. Cyclic phosphates, O(2)S[(t-Bu)(2)C(6)H(2)O](2)P(O)Cl (4) and O(2)S[Me(t-Bu)C(6)H(2)O](2)P(O)(OC(6)H(4)-m-CF(3)) (5), resulted from hydrolysis reactions of 3 and 2, respectively. Phosphate O(2)S[Me(t-Bu)C(6)H(2)O](2)P(O)(OC(6)F(5)) (6) was prepared from a known phosphorane precursor and independently from the reaction of an N-oxide molecule with a parent phosphite, O(2)S[Me(t-Bu)C(6)H(2)O](2)P(OC(6)F(5)). Two additional compounds containing a sulfur atom in place of the sulfone group, a cyclic phosphite, S[Me(2)C(6)H(2)O](2)P(OC(6)F(5)) (7), and a cyclic phosphate, S[Me(2)C(6)H(2)O](2)P(O)Cl (8), were synthesized. X-ray analysis and NMR data were obtained on all of these compounds to establish the role of electronegative ligands in promoting donor interaction. Compounds 1-3 were hexacoordinate as a consequence of oxygen atom coordination while 7 and 8 were trigonal bipyramidal due to sulfur atom coordination. The chlorine atom and the pentafluorophenoxy group promote similar degrees of coordination in these compounds. The results support the conclusion that the sulfur atom and oxygen atom of the sulfone group show similar coordination abilities in donor action with phosphoranes containing strongly electronegative ligands while in the presence of less electronegative ligands sulfur is the stronger coordinating agent. With phosphates and phosphites the sulfur atom exerts the stronger donor action independent of the electronegativity of the attached ligands.
authors.affiliation: Department of Chemistry, Box 34510, University of Massachusetts, Amherst, Massachusetts 01003-4510.
authors.forename: A.
authors.initials: A
authors.lastname: Chandrasekaran
authors.forename: Paul
authors.initials: P
authors.lastname: Sood
authors.forename: Roberta O.
authors.initials: RO
authors.lastname: Day
authors.forename: Robert R.
authors.initials: RR
authors.lastname: Holmes