Synthesis, Structures, and Norbornene Polymerization Behavior of Aryloxide-N-Heterocyclic Carbene Ligated Palladacycles

• Published in: Organometallics Vol. 30; no. 1; pp. 153 - 159
• Main Authors: Kong, Yong, Wen, Lifang, Song, Haibin, Xu, Shansheng, Yang, Min, Liu, Binyuan, Wang, Baiquan
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 10.01.2011; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; CROSS-COUPLING REACTIONS; NEUTRAL NICKEL; LIGANDS; PALLADIUM COMPLEXES; C-C; OLEFIN POLYMERIZATION; ARYL; AB-INITIO POLYMERIZATION; CATALYTIC EMULSION POLYMERIZATION; SUZUKI-MIYAURA
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om100994s

Treatment of the o-hydroxyaryl imidazolinium pro-ligands (2-OH-3,5- t Bu2C6H2)(R)(C3H3N2)+Br− [R = Me (3a), i Pr (3b), t Bu (3c), Ph (3d), Mes (3e)] with the palladacycle [Pd(dmba)(μ-Cl)]2 (dmba = Me2NCH2C6H5) (2) afforded the corresponding aryloxide-NHC (NHC = N-heterocyclic carbene)-ligated palladacycles (2-O-3,5- t Bu2C6H2)(R)(NHC)Pd(dmba) [R = Me (4), i Pr (5), Ph (6), Mes (7), t Bu (8)]. Notably, without isolating 2, complexes 4−8 could also be obtained by one-pot, three-component, sequential reaction of N,N-dimethylbenzylamine, PdCl2, and the pro-ligands in refluxing acetonitrile in the presence of K2CO3. When the N-functional group on the NHCs is tert-butyl, the NHC in 8 adopts an abnormal binding (C4-bonding). All these complexes were fully characterized by 1H and 13C NMR, high-resolution mass spectrometry (HRMS), and elemental analysis. Single-crystal X-ray diffraction analysis results further confirmed the molecular structures of 4−8 and the abnormal binding of NHC in 8. With methylaluminoxane (MAO) as cocatalyst these palladacycles showed excellent catalytic activities up to 107 g of PNB (mol of Pd) −1 h−1 in the addition polymerization of norbornene.