Darstellung und katalytische Eigenschaften von Rhodium(I)-Komplexsalzen des Typs [Rh(COD)o-Py(CH2)2P(Ph)(CH2)3ZR)]PF6 (Z = O,NH) |
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Authors: | H.-J. Haupt U. Ortmann |
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Abstract: | Preparation and Catalytic Properties of Rhodium(I) Complex Salts of the Type [Rh(COD)(o-Py(CH2)2 P(Ph)(CH2)3ZR)]PF6 (Z = O, NH) . In dichloromethane solutions were reacted [Rh(COD)Cl]2 (COD = cis,cis-1.5-cyclooctadiene) with each of the four new ligands of the type o-Py(CH2)2P(Ph)(CH2)3ZR in the presence of the halogen scavenger TIPF6 at 0°C to complex salts [Rh(COD) (o-Py(CH2)2P(Ph)(CH2)3ZR]PF6 (ZR = OC2H5, I ; OPh, II ; NHPh, III ; NHcyclo? C6H11, IV ). The Rh1 complex cation in the obtained compounds I – IV coordinates besides the bedentate COD group the ligand donor atoms P und pyridinic N and the remaining donor atom Z is uncoodinated in an assumed square planar ligand geometry at the Rh central atom. In 1.4 dioxane solutions the complex catalysts I – IV polymerize at 25°C the substrate phenylacetylene (PA) to polyphenylacetylene (PPA): values of TON [h?1] between 352 ( I ) and 876 ( IV ), and average molecular weights Mw (GPC measurements) between 238 000 ( I ) and 199 900 ( IV ). These given values exhibit a dependency on the ZR group in complexes I – IV . The microstructure of isolated PPA is cis-transoidal. It is formed stereospezific and, based on MNDO calculations, is thermodynamically favoured. For the purpose of comparison, from both the newly synthesized compounds of the type [Rh(COD)DBN- (or DBU)Cl] (DBN = 1.5-Diazabi-cyclo[4.3.0.]non-5-en, DBU = 1.8-Diazabicycl0[5.4.0]- undec-7-en) was obtained a larger value of TON with 1292 (or 1327) [h?], but a lower value of M, with 166200 (or 131200). These catalysts including I –IV polymerize PA to PPA at a lower reaction temperature with improved selectivity and larger values of Mw as hitherto known catalyst systems. |
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Keywords: | Rhodium( I) Complex Salts Preparation Catalysis |
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