Darstellung und katalytische Eigenschaften von Rhodium(I)-Komplexsalzen des Typs [Rh(COD)o-Py(CH2)2P(Ph)(CH2)3ZR)]PF6 (Z = O,NH)

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 M_w (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 M_w as hitherto known catalyst systems.