Novel Route to Cationic Palladium(II)-Cyclopentadienyl Complexes Containing Phosphine Ligands and Their Catalytic Activities.

The Pd(II) complexes [Pd(Cp)(L) n ] m [BF 4 ] m were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF 3 ∙OEt 2 ( n = 2, m = 1: L = PPh 3 ( 1 ), P( p -Tol) 3 , tris ( ortho -methoxyphenyl)phosphine (TOMPP), tri -2-furylphosphine, tri -2-thienylphosphine; n = 1, m = 1: L = dppf, dppp ( 2 ), dppb ( 3 ), 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: 1,6-bis(diphenylphosphino)hexane). Complexes 1 - 3 were characterized using X-ray diffractometry. The inspection of the crystal structures of the complexes enabled the recognition of (Cp - )⋯(Ph-group) and (Cp - )⋯(CH 2 -group) interactions, which are of C-H…π nature. The presence of these interactions was confirmed theoretically via DFT calculations using QTAIM analysis. The intermolecular interactions in the X-ray structures are non-covalent in origin with an estimated energy of 0.3-1.6 kcal/mol. The cationic palladium catalyst precursors with monophosphines were found to be active catalysts for the telomerization of 1,3-butadiene with methanol ( TON up to 2.4∙10 4 mol 1,3-butadiene per mol Pd with chemoselectivity of 82%). Complex [Pd(Cp)(TOMPP) 2 ]BF 4 was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 × 10 3 g PA ·(mol Pd ·h) -1 were observed).