The reduction of platinum(IV) and palladium(IV) ions by 2,6-pyridinedihydroxamic acid

Abstract

Reaction of K₂[Pt^IVCl₆] and K₂[Pd^IVCl₆] with 2,6-pyridinedihydroxamic acid (2,6-pyha) and its disodium salt, 2,6-pyhaNa₂, yielded not the desired Pt(IV) and Pd(IV) 2,6-pyridinedihydroxamato complexes, but rather the Pt(II) and Pd(II) 2,6-pyridinedicarboxylato complexes, trans-[Pt^II(2,6-pyca_H−1)₂]·2H₂O and trans-[Pd^II(2,6-pyca_H−1)₂]·2H₂O respectively (2,6-pyca = 2,6-pyridinedicarboxylic acid). Thus in the presence of Pt(IV) and Pd(IV), the dihydroxamic acid was adventitiously hydrolysed to the corresponding dicarboxylic acid and Pt(IV) and Pd(IV) reduced to Pt(II) and Pd(II)in situ. The X-ray crystal structures of 2,6-pyha, 2,6-pyhaNa₂·8H₂O, trans-[Pt^II(2,6-pyca_H−1)₂]·2H₂O and trans-[Pd^II(2,6-pyca_H−1)₂]·2H₂O are reported, together with a possible mechanism for the metal-assisted hydrolysis of the dihydroxamic acid and reduction of Pt(IV) and Pd(IV) to Pt(II) and Pd(II) respectively.