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A newpyrene-N-heterocyclic carbene ligand has been obtained andcoordinated to rhodium and iridium, affording the corresponding [MCl(NHC)(COD)]and [MCl(NHC)(CO)2] complexes (M = Ir, Rh). The presenceof the pyrene backbone allows the introduction of a η6-bonded [RuCp]+fragment and facilitates the formationof the corresponding heterometallic complexes of Rh/Ru and Ir/Ru.The stereoelectronic properties of the new ligand have been studiedby means of IR spectroscopy and cyclic voltammetry and demonstratethat the introduction of the [RuCp]+fragment results inthe reduction of the electron-donating power of the ligand. [ABSTRACT FROM AUTHOR]

A bis(imidazolidine)withtwo butylene linkers between the nitrogen atoms of the adjacent heterocycleshas been prepared. This tetracyclic molecule can be coordinated toiridium and palladium following two different methodologies. The coordinationto iridium is achieved by double C(sp3)–H activationof the neutral tetracyclic bis(imidazolidine), which reacts with [IrCl(COD)]2to afford the corresponding bis-NHC complex that containstwo IrCl(COD) fragments. The reaction is facilitated by the additionof 1,5-cyclooctadiene, which is released from the reaction as cyclooctene.The reaction of the bis-NHC[IrCl(COD)] (bis-NHC = bis(imidazolindiylidene))complex with CO allows the formation of the corresponding tetracarbonylcomplex of diiridium. The molecular structures of the two iridiumcomplexes have been determined by means of X-ray crystallography.The reaction of the tetracyclic bis(imidazolidine) with N-bromosuccinimide allows the formation of a tetracyclic bis(imidazolinium)salt, which serves as a traditional bis-NHC precursor. The reactionof this bis(imidazolinium) salt with Pd(OAc)2in the presenceof KI and in acetonitrile allows the formation of the bis-NHC[PdI2(CH3CN)]2complex. The acetonitrileligand can be easily replaced by reaction with 3-chloropyridine, affordingthe corresponding bis-NHC[PdI2(3-Clpyr)]2complex.The two palladium complexes were tested in the acylation of aryl halideswith hydrocinnamaldehyde, showing moderate to low activity. [ABSTRACT FROM AUTHOR]

A series of homo- and hetero-dimetallic complexes ofIr, Rh, and Pd have been obtained using our previously reported Y-shapedtris-NHC ligand. The new complexes can be obtained through the isolationof the corresponding monometallic intermediates (in which the ligandalways coordinates in a chelating form) or by a one-pot stepwise syntheticprotocol that avoids the isolation of the intermediate. The catalyticproperties of the Ir–Pd complexes have been explored in twotandem processes: dehalogenation/transfer hydrogenation of haloacetophenonesand Suzuki-coupling/transfer hydrogenation of p-bromoacetophenone.These two complexes have been also tested in two model reactions typicallycatalyzed by iridium (cyclization of 2-aminophenyl ethyl alcohol toyield indole) and palladium (acylation of bromobenzene with n-hexanal). [ABSTRACT FROM AUTHOR]