title: Dimethylphosphinate bridged binuclear Rh(i) catalysts for the alkoxycarbonylation of aromatic C-H bonds.
abstract: A variety of binuclear rhodium(i) complexes featuring two bridging dimethylphosphinate ligands ((CH3)2PO2-) have been prepared and tested in the alkoxycarbonylation of aromatic C-H bonds. The complex [Rh(μ-κO,O'-(CH3)2PO2)(cod)]2has been prepared by a reaction of [Rh(μ-MeO)(cod)]2with 2 equivalents of dimethylphosphinic acid. Binuclear complexes [Rh(μ-κO,O'-(CH3)2PO2)(CO)L]2(L = PPh3, P(OMe)Ph2and P(OPh)3) were obtained by carbonylation of the related mononuclear complexes [Rh(κO-(CH3)2PO2)(cod)(L)], which were prepared in situ by the reaction of [Rh(μ-κO,O'-(CH3)2PO2)(cod)]2with 2 equivalents of L. Conversely, if L = IPr, the reaction of [Rh(μ-κO,O'-(CH3)2PO2)(CO)L]2with carbon monoxide affords the mononuclear complex [Rh(κO-(CH3)2PO2)(CO)2IPr]. The subsequent reaction with trimethylamine N-oxide gives the corresponding binuclear complex [Rh(μ-κO,O'-(CH3)2PO2)(CO)(IPr)]2by abstraction of one of the carbonyl ligands. Complexes [Rh(μ-κO,O'-(CH3)2PO2)(cod)]2and [Rh(κO-(CH3)2PO2)(cod)(L)] (L = IPr, PPh3, P(OMe)Ph2, P(OPh)3) are active precatalysts in the alkoxycarbonylation of C-H bonds, with the ligand system playing a key role in the catalytic activity. The complexes that feature more labile Rh-L bonds give rise to better catalysts, probably due to the more straightforward substitution of L by a second carbonyl ligand, since a more electrophilic carbonyl carbon atom is more susceptible toward aryl migration. In fact, complexes [Rh(μ-κO,O'-(CH3)2PO2)(CO)2]2and [Rh(μ-Cl)(CO)2]2, generated in situ from [Rh(μ-κO,O'-(CH3)2PO2)(cod)]2and [Rh(μ-Cl)(cod)2]2, respectively, are the most active catalysts tested in this work.
authors.affiliation: Departamento de Química Inorgánica - Instituto de Síntesis Química y Catálisis Homogénea-ISQCH, Universidad de Zaragoza - CSIC, C/Pedro Cerbuna 12, 50009 Zaragoza, Spain. miglesia@unizar.es oro@unizar.es.
authors.forename: Amaia
authors.initials: A
authors.lastname: Iturmendi
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Sanz Miguel
authors.forename: Saheed A
authors.initials: SA
authors.lastname: Popoola
authors.forename: Abdulaziz A
authors.initials: AA
authors.lastname: Al-Saadi
authors.forename: Manuel
authors.initials: M
authors.lastname: Iglesias
authors.forename: Luis A
authors.initials: LA
authors.lastname: Oro