Ethylene Oxidation by a Platinum(II) Hydroxo Complex. Insights into the Wacker Process

Abstract

The ethylene reaction of hydroxo complex [Pt(COD)(μ-OH)] 2 (OTf) 2 (4) yields acetaldehyde and an equilibrium mixture of Pt 11) are detected as intermediates during the reaction. The reaction displays three phases:(1) an induction period, (2) an accelerating reaction yielding intermediate 11, water, and 6 plus 7, and (3) a linear decrease in the concentration of 11 with simultaneous formation of acetaldehyde and more 6 plus 7. The reaction is proton catalyzed, and phases 1 and 2 are attributed to autocatalytic behavior resulting from the acidic complex of 6 with water, [Pt(COD)(C 2 H 5 )(OH 2 )]OTf. Phase 3 is initiated by the complete consumption of basic 4 and the resulting release of protons to catalyze the reaction of 11 with water and ethylene to give acetaldehyde and 6 plus 7.

Facile Hydrolysis and Alcoholysis of Palladium Acetate

“…Finally, with complex 1 in hand, we turned our attention to trying to resolve an issue that remains somewhat contentious, namely whether or not palladium hydroxide complexes play any role in the Wacker oxidation of alkenes. There is still some debate as to whether the oxygen is incorporated into the product by anti addition of an external oxygen nucleophile (H 2 O or OH − ) to the coordinated alkene or by 1,2‐migratory insertion of the coordinated alkene into the PdO bond of a hydroxide complex (Scheme ) 16…”

Facile Hydrolysis and Alcoholysis of Palladium Acetate

“…[15] Finally,with complex 1 in hand, we turned our attention to trying to resolve an issue that remains somewhat contentious, namely whether or not palladium hydroxide complexes play any role in the Wacker oxidation of alkenes.T here is still some debate as to whether the oxygen is incorporated into the product by anti addition of an external oxygen nucleophile (H 2 OorOH À )tothe coordinated alkene or by 1,2-migratory insertion of the coordinated alkene into the PdÀOb ond of ah ydroxide complex (Scheme 3). [16] Palladium acetate can be used to good effect in the Wacker oxidation of alkenes to ketones,using benzoquinone as an oxidant in the presence of as trong acid. [17,18] We have previously shown that p-toluene sulfonic acid reacts with palladium acetate to give unusual palladacycles in which the toluene ring has undergone orthometallation.…”

Hydroxo Radicals, C–H Activation, and Pt–C Bond Formation from 77 K Photolysis of a Platinum(IV) Hydroxo Complex

“…The phosphorus centers are coupled to each other (doublet, 2 J PP = 513 Hz) and to 195 Pt with 1 J PtP = 1853 Hz (PEt 3 ) and 1410 Hz (P b ). 1 H− 1 H COSY and 1 H− 13 C HMQC NMR spectroscopy and comparisons to data for platinum(II) phosphaplatinacycle complexes 27−30 allowed identification and assignment of all 1 H NMR shifts for 2. The ringsystem methylene protons appear as diastereotopic pairs.…”