title: An approach to bimetallic catalysts by ligand design.
abstract: New diphosphines based on benzofurobenzofuran and dibenzodioxocin backbones, forming exclusively bimetallic complexes were designed and synthesized. Depending on the ligand to metal ratio, face-to-face bimetallic complexes or syn-chloride bridged dimeric complexes were formed as main reaction products. The structures of the rhodium complexes of the new ligands 4, 7, 10, 13, 16 were established in solution by NMR, IR, and MS spectroscopy. The molecular structures of the syn-chloride bridged dimeric complexes [Rh(2)(CO)(2)(mu-Cl)(2)(4)] (22), [Rh(2)(CO)(2)(mu-Cl)(2)(10)] (24), and the face-to-face bimetallic complexes [Rh(CO)Cl(4)](2) (17), [Rh(CO)Cl(10)](2) (19), and [Rh(CO)Cl(13)](2) (20) were confirmed by X-ray crystallography. Ligands 4, 7, 10, 13, 16, and SPANphos were tested in rhodium catalyzed methanol carbonylation at 150 degrees C and 22 bar of CO gas, showing high activities under catalytic conditions.
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), Avgda. Països Catalans 16, Tarragona, Spain.
authors.forename: Josep M
authors.initials: JM
authors.lastname: López-Valbuena
authors.forename: Eduardo C
authors.initials: EC
authors.lastname: Escudero-Adan
authors.forename: Jordi
authors.initials: J
authors.lastname: Benet-Buchholz
authors.forename: Zoraida
authors.initials: Z
authors.lastname: Freixa
authors.forename: Piet W N M
authors.initials: PW
authors.lastname: van Leeuwen
mesh_terms: D001572:Benzofurans / Q000737:chemistry; D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008024:Ligands; D008968:Molecular Conformation; D010720:Phosphines / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry
chemical_list: D001572:Benzofurans; D056831:Coordination Complexes; D008024:Ligands; D010720:Phosphines; D012238:Rhodium