Preparation and C−X Reductive Elimination Reactivity of Monoaryl Pd^IV−X Complexes in Water (X = OH, OH₂, Cl, Br)

Abstract

Monohydrocarbyl palladium(IV) complexes bearing OH, OH(2), Br, and Cl ligands at the metal and supported by facially chelating 1-hydroxy-1,1-bis(2-pyridyl)methoxide were readily prepared in water at 0 °C. These complexes reductively eliminate Ar-X (X = OH, Br, Cl) in water at room temperature in high yield, and the corresponding first-order rate constants k(OH), k(Cl), and k(Br) are on the same order of magnitude.

Selective and efficient oxidation of ethylene to ethylene glycol acetates with H2O2 catalyzed by Pd(OAc)2–di(2-pyridyl)ketone–di(2-pyridyl)methanesulfonate system

“…The most active catalyst developed in this work consists of a mixture of palladium acetate and derived dpk and Me-dpms complexes. Using analogy with previously studied oxidation of dpk-supported organopalladium(II) complexes [23] as well as dpms-supported organoplatinum(II) complexes [25e29], we propose that high selectivity and activity of our systems in the formation of glycol acetates is due to facile dpk or dpms enabled functionalization of Pd II alkyl intermediates via Pd IV species. Future studies will be directed toward improving conversions and reactivity by developing novel tridentate ligand motifs for mild and selective difunctionalization of olefins utilizing environmentally benign oxidants such as H 2 O 2 and molecular oxygen.…”

“…The latter can be oxidized by H 2 O 2 to form a Pd IV intermediate 12 (step iv) at a much faster rate than 10 itself. The ability of dpk [23] and dpms [23] ligands to accelerate the rate of oxidation of supported palladium(II) monohydrocarbyl complexes has been documented previously. The source of the ligand L needed for the formation of 11 might be a 2:1 [(dpk) 2 Pd] 2þ complex or [(dpk-H 2 O)(Me-dpms)Pd] þ , 9.…”

“…The dpk ligand, a derived semiketal or gem-diol can act as bidentate ligands with respect to a d 8 metal center. In the form of a singly deprotonated semiketal or gem-diol, the dpk can act as a tridentate fac-chelating ligand [23,30e32], stabilize a d 6 metal center, such as in Pd IV [23] and Pt IV [32] complexes, and enable facile oxidation of Pd II monohydrocarbyls to Pd IV monohydrocarbyls with H 2 O 2 in aqueous solutions [23].…”

“…Recently we showed that metallacyclic monohydrocarbyl Pd II complexes supported by di(2-pyridyl)ketone ligand (dpk) can be oxidized with H 2 O 2 in water under mild conditions to cleanly and selectively produce derived monohydrocarbyl Pd IV species stabilized by a hydrated gem-diol form of the dpk ligand (Scheme 2) [23]. The resulting Pd IV species are capable of subsequent clean CeO bond elimination [23].…”

“…The resulting Pd IV species are capable of subsequent clean CeO bond elimination [23]. Following up on the earlier work, we sought to expand such ligand-enhanced reactivity of Pd II complexes supported by the dpk ligand to catalytic olefin difunctionalization using H 2 O 2 as an oxidant.…”