Synthesis, structure, and temperature-dependent dynamics of neutral palladium allyl complexes of annulated diaminocarbenes and their catalytic application for C-C and C-N bond formation reactions

Imidazolinium salts 7,9-bis(2,4,6-trimethylphenyl)-6b,9a- dihydroacenaphtho[1,2-d]imidazolinium tetrafluoroborate and 7,9-bis(2,6- diisopropylphenyl)-6b,9a-dihydroacenaphtho[1,2-d]imidazolinium tetrafluoroborate, designated as [(BIAN-SIMes)(H)]BF₄ (3a) and [(BIAN-SIPr)(H)]BF₄ (3b), respectively, have been prepared and structurally characterized. The molecular structure of 3a shows the presence of a bifurcated hydrogen bond between the tetrafluoroborate anions and the central imidazolinium proton (-NCHN-). The palladium(II) complexes (η³- C₃H₅)Pd(BIAN-SIMes)Cl (5a) and (η³-C ₃H₅)Pd(BIAN-SIPr)Cl (5b) have been synthesized. The temperature-dependent NMR behavior of σ-bonded palladium(II) complex 5b was studied. The crystal structure of 5b shows a localized single and double bond between the allyl ligand. The catalytic activities of the palladium(II) complexes 5a and 5b have been evaluated for Suzuki-type C-C coupling and for room-temperature C-N bond formation using aryl halides.