Silver, Gold, Palladium, and Platinum N-heterocyclic Carbene Complexes Containing a Selenoether-Functionalized Imidazol-2-ylidene Moiety

The selenoether-functionalized imidazolium salt N-[(phenylseleno)methylene)]-N'-methylimidazolium chloride (LH+Cl-) was transformed into the metal-carbene complexes [AgCl(L)], [AuCl(L)], [PdCl2(L)], and [PtCl2(L)] by the reaction with Ag2O and an additional transmetalation reaction of [AgCl(L)] with [(THT)AuCl], [(COD)PdCl2], and [(COD)PtCl2], respectively (THT = tetrahydrothiophene, COD = cyclooctadiene). The compound [AuI2Cl(L)] was prepared by oxidation of [AuCl(L)] with elemental iodine. The microwave-assisted decomposition of [PdCl2(L)] in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIm]NTf2) or in propylene carbonate led to the formation of Pd17Se15 nanoparticles of 51 +/- 17 or 26 +/- 7 nm diameter, respectively. The decomposition of the platinum complex resulted in either small Pt clusters around 1 nm size from the ionic liquid suspension or Pt nanoparticles of 3 +/- 1 nm diameter in propylene carbonate. High-resolution X-ray photoelectron spectroscopy (HR-XPS) and C-13 cross-polarization magic-angle spinning (CP MAS) NMR indicated that the surface of Pt clusters and crystalline Pt nanoparticles is formed by an amorphous Pt(II)/Se shell and by carbene ligand residues.