Synthesis, Characterization, and Reaction Chemistry of PtCl2[P(m-C6H4SO3Na)3]2, an Alkyne Hydration Catalyst

The preparation and reactions of cis -PtCl 2 (TPPTS) 2 (TPPTS = P( m -C 6 H 4 SO 3 Na) 3 ) in aqueous solution are described. In the absence of excess Cl -, cis -PtCl 2 (TPPTS) 2 exists as a mixture with 20% of cis -Pt(Cl)(H 2 O)(TPPTS) 2 +; the aqua complex was prepared independently by reaction with Ag + . As a result of the aquation cis -PtCl 2 (TPPTS) 2 is slightly acidic. Increasing the pH for a solution of cis -PtCl 2 (TPPTS) 2 leads to Pt 2 (TPPTS) 4 (μ-OH) 2 2+; a subsequent decrease in pH leads to cis -Pt(OH 2 ) 2 (TPPTS) 2 2+ and, ultimately, cis -PtCl 2 (TPPTS) 2 . All of these complexes were characterized by 31 P and 195 Pt NMR. cis -PtCl 2 (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. Hydration of 4-pentyn-1-ol occurs by a 5-exo-dig mechanism, while hydration of 3-pentyn-1-ol occurs through a 5-endo-dig mechanism.