title: Hydrogenolysis of palladium(II) hydroxide, phenoxide, and alkoxide complexes.
abstract: A series of pincer ((tBu)PCP)Pd(II)-OR complexes ((tBu)PCP = 2,6-bis(CH(2)P(t)Bu(2))C(6)H(3), R = H, CH(3), C(6)H(5), CH(2)C(CH(3))(3), CH(2)CH(2)F, CH(2)CHF(2), CH(2)CF(3)) were synthesized to explore the generality of hydrogenolysis reactions of palladium-oxygen bonds. Hydrogenolysis of the Pd hydroxide complex to generate the Pd hydride complex and water was shown to be inhibited by formation of a water-bridged, hydrogen-bonded Pd(II) hydroxide dimer. The Pd alkoxide and aryloxide complexes exhibited more diverse reactivity. Depending on the characteristics of the -OR ligand (steric bulk, electron-donating ability, and/or the presence of β-hydrogen atoms), hydrogenolysis was complicated by hydrolysis by adventitious water, a lack of reactivity with hydrogen, or a competing dissociative β-hydride abstraction reaction pathway. Full selectivity for hydrogenolysis was observed with the partially fluorinated Pd(II) 2-fluoroethoxide complex. The wide range of Pd-OR substrates examined helps to clarify the variety of reaction pathways available to late-transition-metal alkoxides as well as the conditions necessary to tune the reactivity to hydrogenolysis, hydrolysis, or dissociative β-hydride abstraction.
authors.affiliation: Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, United States.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Fulmer
authors.forename: Alexandra N
authors.initials: AN
authors.lastname: Herndon
authors.forename: Werner
authors.initials: W
authors.lastname: Kaminsky
authors.forename: Richard A
authors.initials: RA
authors.lastname: Kemp
authors.forename: Karen I
authors.initials: KI
authors.lastname: Goldberg
mesh_terms: D018360:Crystallography, X-Ray; D006865:Hydrogenation; D006878:Hydroxides / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*
chemical_list: D006878:Hydroxides; D009942:Organometallic Compounds; D010087:Oxides; D010165:Palladium