Synthesis, Characterization, and Acidity Properties of [MCl(H2)(L)(PMP)]BF4(M = Ru, L = PPh3, CO; M = Os, L = PPh3; PMP = 2,6-(Ph2PCH2)2C5H3N)

Abstract

Treatment of RuCl2(PPh3)3 with PMP (PMP = 2,6-(Ph2PCH2)2C5H3N) in acetone produced RuCl2(PPh3)(PMP), which has been characterized by X-ray diffraction. Treatment of RuCl2(PPh3)(PMP) with NaBH4 in methanol gave RuHCl(PPh3)(PMP), acidification of which with HBF4·Et2O produced the molecular dihydrogen complex [RuCl(H2)(PPh3)(PMP)]BF4. Treatment of RuHCl(CO)(PPh3)3 with PMP in benzene produced RuHCl(CO)(PMP), which reacted with HBF4·Et2O to give the molecular dihydrogen complex [RuCl(H2)(CO)(PMP)]BF4. The osmium molecular dihydrogen complex [OsCl(H2)(PPh3)(PMP)]BF4 was prepared by protonation of OsHCl(PPh3)(PMP) with HBF4·Et2O. Relative acidities of the dihydrogen complexes were investigated by NMR spectroscopy of equilibrium reactions conducted in CD2Cl2. [RuCl(H2)(CO)(PMP)]BF4 is more acidic than [RuCl(H2)(PPh3)(PMP)]BF4, which is in turn more acidic than its osmium analog [OsCl(H2)(PPh3)(PMP)]BF4.