Synthesis, characterization, and reaction chemistry of PtCl2[P(m-C6H4SO3Na)(3)](2), an alkyne hydration catalyst

The preparation and reactions of cis-PtCl2(TPPTS)(2) (TPPTS = P(m-C6H4SO3Na )(3)) in aqueous solution are described. In the absence of excess Cl-, cis- PtCl2(TPPTS)2 exists as a mixture with 20% of cis-Pt(Cl)(H2O)(TPPTS)(2)(+); the aqua complex was prepared independently by reaction with Ag+. As a res ult of the aquation cis-PtCl2(TPPTS)(2) is slightly acidic. Increasing the pH for a solution of cis-PtCl2(TPPTS)(2) leads to Pt-2(TPPTS)(4)(mu -OH)(2) (2+); a subsequent decrease in pH leads to cis-Pt(OH2)(2)(TPPTS)(2) (2+) a nd, ultimately, cis-PtCl2-(TPPTS)(2). All of these complexes were character ized by P-31 and Pt-195 NMR. cis-PtCl2(TPPTS)(2) functions as an effective hydration catalyst for the water-soluble alkynes 4-pentyn-1-ol and 3-pentyn -1-ol. Both hydrations are stereospecific to 5-hydroxy-2-pentanone. Hydrati on of 4-pentyn-1-ol occurs by a 5-exo-dig mechanism, while hydration of 3-p entyn-1-ol occurs through a 5-endo-dig mechanism.