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Title: Syntheses and characterization of ruthenium η²-dihydrogen and η²-silane complexes
Authors: Ng, Siu-man
Keywords: Ruthenium.
Ligand binding (Biochemistry)
Hong Kong Polytechnic University -- Dissertations
Issue Date: 1998
Publisher: The Hong Kong Polytechnic University
Abstract: Protonation of [RCnRuH(L)(L')]⁺ (RCn = 1,4,7-triazacyclononane and 1,4,7-trimethyl-1,4,7-triazacyclononane, (L)(L') = (PPh₃)₂, dppe, and (CO)(PPh₃)) and TpRuH(dppe) (Tp = hydrotris(pyrazolyl)borato) produced the corresponding dicationic dihydrogen complexes [RCnRu(H₂)(L)(L')]²⁺ and new monocationic dihydrogen complex [TpRu(H₂)(dppe)]⁺, respectively. pKa measurments indicate that the dicationic η²-H₂ complexes are more acidic than their monocationic Tp and Cp counterparts. [MeCnRu(H₂)(CO)(PPh₃)]²⁺ was found to be more acidic than [HCnRu(H₂)(CO)(PPh₃)]²⁺, probably due to stronger H-H interaction in the latter complex. It is also noted that triazacyclononane and hydrotris(pyrazolyl)borato dihydrogen complexes with pseudo aqueous pKa values well above that of H₃O⁺ can be deprotonated by H₂O to form the corresponding monohydride complexes in organic/aqueous mixed solvents. It is believed that deprotonation of the dihydrogen ligands in these complexes is assisted by strong solvation of H⁺ by H₂O. No silane complex was observed in the reaction of [TpRu(H₂)(PPh₃)₂]⁺ with silane, although the η²-H₂ ligand had undoubtedly been displaced. The silane complex had probably been formed, but it was readily attacked by nucleophilic species such as the counterion BF₄⁻ or water in the solvent. It was found that ruthenium solvent hydride complex [TpRuH(CH₃CN)(PPh₃)] reacted with silanes HSiR₃ ( R₃ = HPh₂, HEt₂, Ph₃, Et₃, H₂Ph and (OEt)₃) to yield the silane complexes [TpRuH(HSiR₃)(PPh₃)] which, instead of equilbrating between the η²-silane and η²-H₂ tautomeric forms, interchanged the H atoms rapidly, and rendering them equivalent. The silane complex [TpRuH(HSiR₃)(PPh₃)] is analogous to the dihydrogen hydride complex TpRuH(H₂)(PPh₃) which we have recently reported.
Description: xix, 161 leaves : ill. ; 30 cm.
PolyU Library Call No.: [THS] LG51 .H577M ABCT 1998 Ng
Rights: All rights reserved.
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