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Oxidation of Diorganopalladium(II) Complexes by Water and Halogens: Reactions Involving Methyl Group Transfer and Structural Studies of Hydrogen-Bonded Adducts Formed by Aryl Alcohols with the Pallada(IV)cyclopentane Complex Pd(CH2CH2CH2CH2)(OH){(pz)(3)BH}([(pz)(3)BH](-)=tris(pyrazol-1-yl)borate)

journal contribution
posted on 2023-05-16, 10:14 authored by Allan CantyAllan Canty, Jin, H, Roberts, AJ, Skelton, BW, White, AH
The first observations of oxidation of palladium(II) by water are reported. The pallada-(II)cyclic complex ion [Pd(CH 2CH 2CH 2CH 2){(pz) 3BH}] - [(pz) 3BH = tris (pyrazol-1-yl)borate)] is oxidized by water in acetone or tetrahydrofuran to form Pd(CH 2CH 2CH 2CH 2)(OH){(pz) 3-BH} and hydrogen, and oxidation by hydrogen peroxide gives the same complex. Oxidation by halogens results in the formation of Pd(CH 2CH 2CH 2CH 2)(X){(pz) 3BH} (X = Cl, Br, I), and these complexes, together with the hydroxopalladium(IV) complex, represent the first examples of stable dihydrocarbylpalladium(IV) complexes. The octahedral complex Pd(CH 2CH 2CH 2CH 2)(OH){(pz) 3BH} forms adducts with phenol, 3-methylphenol, and pentafluorophenol with an overall composition of Pd(CH 2CH 2CH 2CH 2)(OH){(pz) 3BH}·2ArOH (5 and 6) and Pd(CH 2CH 2CH 2CH 2)(OH){(pz) 3BH}·C 6F 5OH (7). Complex hydrogen-bonding interactions occur in the adducts, consistent with the assignment of the phenol and 3-methylphenol adducts as hydroxopalladium(IV) complexes and the pentafluorophenol adduct as an aquapalladium(IV) complex. Complexes 5 and 6 are considered to contain the hydrogen-bonding motifs H-O(Pd)⋯HO(Ph)⋯HOPh and Ar(H)O⋯H-O(Pd)⋯HOAr, respectively, and 7 to contain an aquapalladium(IV) cation in which both hydrogen atoms of the aqua ligand act as hydrogen-bond donors to pentafluorophenoxide ions in a centro-symmetric dimer, [Pd(CH 2CH 2CH 2CH 2)(OH 2){(pz) 3BH}·C 6F 5O] 2. The complex ions [PdMeR{(pz) 3BH}] - (R = Me, Ph) react with water or halogens to form the PdMe 2R{(pz) 3- BH} and Pd IIR species, and in the case of water as the oxidant, hydrogen is also formed. These reactions occur via initial oxidation to form undetected palladium(IV) species, presumably PdMeR(X){(pz) 3BH} (X = OH, Cl, Br, I), which undergo rapid methyl group exchange reactions with [PdMeR{(pz) 3BH}] - to form Pd IIR species and PdMe 2R{(pz) 3BH}. The oxidation of palladium(II) by water and the structural analysis of hydroxo- and aquapalladium(IV) complexes represent the first examples of organopalladium(IV) chemistry in aqueous media.


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School of Natural Sciences


American Chemical Society

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United States of America

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