The reduction of trans-[Pd(NHC)(2)Cl-2] (NHC = IMes, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; (IPr2)-Pr-i = 1,3-bis-isopropylimidazol-2-ylidene) with potassium graphite under an atmosphere of CO affords the palladium NHC carbonyl clusters [Pd-3(mu-CO)(3)(NHC)(3)] (NHC = IMes, 1; (IPr2)-Pr-i, 3). Treatment of 1 with SO2 at room temperature yields the bridging SO2 complex [Pd-3(mu-SO2)(3)(IMes)(3)] (4) in quantitative yield. Complexes 1, 3 and 4 have been structurally characterised by X-ray crystallography. (C) 2009 Elsevier B. V. All rights reserved.