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(L2) (M = Pd, Pt; L2 = bpy, 1,10-Phenanthroline) and C...O and C...E Bond Formation at Palladium(IV)

Abstract

Oxidation of PdMe2(L2) [L2 = 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen)] by diphenyl diselenide provides the first examples of stable dimethylpalladium(IV) complexes PdMe2(SePh)2(L2), and pallada(IV)cyclic Pd(CH2CH2CH2CH2)(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 [L2 = bpy, orthorhombic Pnma; L2 = phen, triclinic P1 bar; an additional phase for PtMe2(SePh)2(phen), tetragonal, I41/a]. The complexes PdMe2(SePh)2(L2) decompose at moderate temperatures in CDCl3 following first-order behavior [L2 = bpy, Ea ~46 kJ mol-1, DSact(20 °C) ~ -170 J K-1 mol-1; L2 = phen, Ea ~36 kJ mol-1, DSact(20 °C) ~ -204 J K-1 mol-1] to give ethane and Se(Ph)Me, together with small quantities of SePh2. 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 PdMe2(bpy) or Pd(CH2CH2CH2CH2)(bpy) by (O2CPh)2 or (SPh)2.