Formation of the Platinum-Olefin Bond Catalyzed by SnCl3-

The kinetics of the reactions between PtCl42- and various olefins have been studied in aqueous solutions 1.9 M in NaCl and 0.1 M in HCI, at 25, in the presence of SnCl3-. The product is a ir-olefinic complex of the Zeise's salt type. The rate law is a two-term expression of the type: kobsd,k' = k' Loll k"[SnCl3. The first term is interpreted as a bimolecular attack of the olefin on the PtCI.41- complex and the second depends also on [SnC13-11. As far as the first SnC13- -uncatalyzed term is concerned, the reactivity changes in the order: allyl NHS + > butyl NH3+ > allyl SO3- > allyl alcohol > pentenyl NHS. The second SnCl3 catalyzed term is interpreted as an easier attack of the olefin on a species of the type Pt(SnCl3)(2)Cl2-, probably the cis isomer, formed in the rate-determining step. The accelerating effect of the group SnCl3- is related to its high trans effect.