Thermodynamics of the formation of cis-bis(dialkylsulfide)-dimethylplatinum(II) complexes from bis(mu-dialkylsulfide)-bisdimethylplatinum(II) and free dialkylsulfide

摘要

Dialkylsulfides react with bis-mu-dialkylsulfidebisdimethylplatinum(II) to form monomeric cis-bis(dialkylsulfide)dimethylplatinum(II). The thermodynamic parameters of these reactions are reported for methyl, ethyl and propyl sulfides. Reactions are spontaneous for the formation of the monomeric compound. Equilibrium constants at 303 K are 2600+/-300 M-1 (R=Me), 50+/-10 M-1 (R=Et), and, 130+/-10 M-1 (R=Pr). Enthalpies are negative for each reaction, indicating that the bridging three center sulfur-platinum bonds of the dimeric compounds are weaker than the two center bonds in the respective monomers. The dimeric compounds owe their existence to the unfavorable entropy of the addition of two moles of dialkylsulfide when the dimers break into two monomeric compounds. For R=Me, Delta H- is -60+/-10 kJ mol(-1) and Delta S- is -120+/-30 J mol(-1) K-1 for the reaction. Likewise, for R=Et, Delta H- is -40+/-10 kJ mol(-1) and Delta S- is -90+/-30 J mol(-1) K-1, and, for R=Pr, Delta H- is -40+/-10 kJ mol(-1) and Delta S- is -100+/-40 J mol(-1) K-1. (C) 1998 Elsevier Science S.A. [References: 6]