Oxygen‐Promoted CH Bond Activation at Palladium

Abstract

[Pd(P(Ar)(tBu)2)2] (1, Ar=naphthyl) reacts with molecular oxygen to form Pd(II) hydroxide dimers in which the naphthyl ring is cyclometalated and one equivalent of phosphine per palladium atom is released. This reaction involves the cleavage of both C-H and O-O bonds, two transformations central to catalytic aerobic oxidizations of hydrocarbons. Observations at low temperature suggest the initial formation of a superoxo complex, which then generates a peroxo complex prior to the C-H activation step. A transition state for energetically viable C-H activation across a Pd-peroxo bond was located computationally.

Cycloheptatrienyl Cyclopentadienyl Titanium Phosphane Ligands in Palladium‐Catalyzed Suzuki–Miyaura Cross‐Coupling Reactions

“…The molecular structures of [Pd( 4 t Bu ) 2 ] and [Pd( 5 t Bu ) 2 ] (Figures and ) reveal the formation of linear bis‐phosphane complexes with P–Pd–P angles of 174.610(13)° in [Pd( 4 t Bu ) 2 ] and 180° in [Pd( 5 t Bu ) 2 ], which exhibits crystallographic inversion symmetry. The Pd–P bond lengths of 2.2857(4) (Pd–P1) and 2.2890(4) Å (P2–Pd) in [Pd( 4 t Bu ) 2 ] and 2.2992(4) Å in [Pd( 5 t Bu ) 2 ] lie in the range reported for other [Pd(PR 3 ) 2 ] complexes . Both structures exhibit a few short intramolecular C‐H ··· Pd van der Waals contacts involving the tert ‐butyl groups and the Cht rings, with the shortest distances of 2.60/2.65 Å and 2.53 Å between Pd and one ortho ‐CH group of each seven‐membered ring.…”

Synthesis of peri-Substituted (Naphthalen-1-yl)phosphine Ligands by Rhodium(I)-Catalyzed Phosphine-Directed C–H Arylation

“…Consequently, only a couple of catalytic systems based on palladium and rhodium have been reported, employing FcP­( t Bu) 2 (Fc = ferrocenyl) and biaryl-based phosphines as starting materials. Meanwhile, a few well-defined cyclomethylated complexes containing (naphthalen-1-yl)­phosphine have been prepared by C–H bond activation . These reports provide a better understanding of the mechanism of such transformations and have led to the design of new functionalized molecules and catalysts. , Herein, we report the rhodium­(I)-catalyzed P-directed C–H arylation of (naphthalen-1-yl)­phosphines to give a series of 8-substituted derivatives.…”

Hydroxide complexes of the late transition metals: Organometallic chemistry and catalysis

“…[Pd(P t Bu2Nap)2] is oxidised by O2 to form a hydroxide-bridged palladium(II) dimer in which the peri-position of the napthyl fragment has been metalated (Scheme 23). 69 In contrast, [Pd(OH)(Me)(di(2-pyridyl)methane sulfonate)] undergoes reaction with oxygen to form [Pd(OH)2(di(2-pyridyl)methane sulfonate)] and a mixture of methanol, ethane, and methyl peroxide. 70 Scheme 23.…”

“…Oxidation of a palladium(0) complex with oxygen to form a C-H activated product. 69 The majority of known palladium hydroxide complexes feature palladium in the +2 oxidation state, but examples of palladium(IV) hydroxide complexes have also been reported. An example of such a species has been prepared from the reaction of a palladium(II) complex with oxygen (Scheme 24).…”