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 ¹³C 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.