Oxidation of complexes by (O2CPh)(2) and (ER)(2) (E = S, Se), including structures of Pd(CH2CH2CH2CH2)(SePh)(2)(bpy) (bpy = 2,2 '-bipyridine) and MMe2(SePh)(2)(L-2) (M = Pd, Pt; L-2 = bpy, 1,10-phenanthroline) and C···O and C···E bond formation at palladium(IV)

Oxidation of PdMe 2(L 2) [L 2 = 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen)] by diphenyl diselenide provides the first examples of stable dimethylpalladium(IV) complexes PdMe 2(SePh) 2(L 2), and pallada(IV)cyclic Pd(CH 2- CH 2CH 2CH 2)(SePh) 2(bpy) may be similarly isolated. X-ray structural studies of the octahedral dimethylpalladium-(IV) complexes and their isomorphous platinum(IV) analogues have been completed [L 2 = bpy, orthorhombic Pnma; L 2 = phen, triclinic P1̄; an additional phase for PtMe 2(SePh) 2(phen), tetragonal, I4 1/a]. The complexes PdMe 2(SePh) 2(L 2) decompose at moderate temperatures in CDCl 3 following first-order behavior [L 2 = bpy, E a ̃ 46 kJ mol -1, ΔS‡(20°C) ∼ -170 J K -1 mol -1; L 2 = phen, E a ∼36 kJ mol -1, ΔS‡(20°C) ∼ -204 J K -1 mol -1] to give ethane and Se(Ph)Me, together with small quantities of SePh 2. Similar C⋯C, C⋯O, C⋯S, and C⋯Se bond formation processes occur on decomposition of palladium(IV) species that are too unstable to be isolated on the oxidation of PdMe 2(bpy) or Pd(CH 2CH 2CH 2CH 2)(bpy) by (O 2CPh) 2 or (SPh) 2.