Darstellung und spektroskopische Charakterisierung der Acetylenkomplexe CpV(CO)2R1C2R2 und CpV(CO)(L)R1C2R2 (Cp=η5-C5H5; R1, R2 = H, Me, Ph, SiMe3; L = PMe3 tBuNC) / Preparation and Spectroscopic Characterization of the Acetylene Complexes CpV(CO)2R1C2R2 and CpV(CO)(L)R1C2R2 (Cp=η5-C5H5; R1, R2 = H, Me, Ph, SiMe3; L = PMe3 tBuNC)

Abstract

The photo-induced reaction of CpV(CO)4 (1) (Cp =η5-C5H5) with alkynes R1C2R2 (R1, R2 = H, Me, Ph, SiMe3) in pentane solution yields the substitution products CpV(CO)2R1C2R2 (2). One CO ligand of complexes 2 is readily displaced by PMe3 or tBuNC affording the derivatives CpV(CO)(L)R1C2R2 {3(PMe3), 4 (tBuNC)}. Compounds 2-4 are characterized by their IR, 1H, 13C, 51V NMR and mass spectra. The alkyne in compounds 2-4 shows typical features of a four electron ligand. The barrier for the rotation of the alkyne ligand around the vanadium alkyne bond axis in the complexes 3-4 is comparatively low (⊿ G≠ = 44.4-68.3 kJ/mol) depending mainly on the steric requirements of the acetylene ligand.