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

The Pd(II) complexes [Pd(Cp)(L)(n)](m)[BF4](m) were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF3 center dot OEt2 (n = 2, m= 1: L = PPh3 (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-)center dot center dot center dot(Ph-group) and (Cp-)center dot center dot center dot(CH2-group) interactions, which are of C-H center dot center dot center dot pi 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)]BF4 was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 x 10(3) gPA.(mol(Pd).h)(-1) were observed)

Automated summary

The Pd(II) complexes [Pd(Cp)(L)(n)](m)[BF4](m) were synthesized by reacting cationic acetylacetonate complexes with cyclopentadiene in the presence of BF3 center dot OEt2. X-ray diffraction analysis confirmed the structures of complexes 1-3 and revealed non-covalent C-H center dot center dot center dot pi interactions. DFT calculations and QTAIM analysis supported the existence of these interactions. The cationic Pd catalyst precursors with monophosphines showed high catalytic activity for the telomerization of 1,3-butadiene with methanol, and complex [Pd(Cp)(TOMPP)(2)]BF4 exhibited efficient catalytic activity for the polymerization of phenylacetylene.