102494-78-0Relevant articles and documents
Kinetics and mechanism of molecular A-frame formation. Reactions of cyclo-octasulfur and sulfur dioxide with Pt2Cl2(μ-Ph2PCH2PPh 2)2 and related binuclear platinum complexes
Muralidharan,Espenson, James H.,Ross, Scott A.
, p. 2557 - 2562 (2008/10/08)
The first reaction referred to in the title follows a second-order rate law in dichloromethane, with k298 = 1.19 M-1 s-1 (ΔH? = 15.1 ± 0.3 kcal/mol, ΔS? = -7.6 ± 0.8 cal mol-1 K-1). With a substantial deficiency of elemental sulfur, nearly all eight atoms can (eventually) be incorporated into the bridgehead position. Data were also obtained for complexes having other ligands in place of Cl-, including Br-, I-, pyridine, NH3, and CO. Complexes with uncharged ligands react very slowly. All of the reactions are substantially accelerated by even trace amounts of a salt such as R4N+X-. The diiodide forms two products concurrently, the A-frame and a Pt(II) chelate, PtI2(η2-dppm); the latter does not result from reaction or decomposition of the former. The SO2 reaction involves preassociation of the reactants, as characterized spectroscopically and kinetically. The adduct appears to be a loose charge-transfer complex, since the phosphorus atoms of dppm remain equivalent in the 31P NMR even at -80°C and the strength of the interaction is low (ΔH° and ΔG°298 are -7 and -1.2 kcal, respectively). Kinetic data for both reactions are consistent with a substantial involvement of Pt-Pt bond breaking in the activation process.
