Design and Performance of Rigid Nanosize Multimetallic Cartwheel Pincer Compounds as Lewis-Acid Catalysts

Abstract

Novel strategies for the preparation of rigid cartwheel pincer metal complexes have been developed. The aromatic backbone of these materials ensures a high rigidity, which is expected to be important for a high retention when these multimetallic nanosize complexes are applied as homogeneous catalysts in a nanomembrane reactor. The ligand precursors C6[C6H3(CH2Y)2-3,5]6 (10, Y = NMe2; 11, Y = SPh; 12, Y = PPh2; 13, Y = pz = pyrazol-1-yl) have been prepared in high yields from the key intermediate C6[C6H3(CH2Br)2-3,5]6 (9). The hexakis(pincer) palladium(II) complexes C6[(PdX)-4-C6H2(CH2Y)2-3,5]6 (14, Y = SPh, L = Cl; 15, Y = PPh2, L = Cl; 16, Y = pyrazol-1-yl, L = OAc; 17, Y = pyrazol-1-yl, L = Cl) have been prepared via direct electrophilic palladation of the corresponding ligands. The (tris)pincer ligand C6H3[Br-4-C6H3(CH2NMe2)2-3,5]3-1,3,5 (20) was prepared via a triple-condensation reaction of 4-bromo-3,5-bis[(dimethylamino)methyl]acetophenone (19). Reaction of 20 with Pd(dba)2 yielded the tripalladium ...