Ligands chelating dicarbene

Some bidentate bis(imidazolin-2-ylidene)s 18 have been used for the preparation of complexes with chelating dicarbene ligands [75-80]. The synthesis, properties, and coordination chemistry of tripodal tris(imidazolin-2-ylidene) ligands like 19... 

Chelating dicarbene ligands were found very useful for stabilizing technetium(V) dioxo species, forming complexes of structure 51, which turned out to be stable to water, a potentially very useful feature for the application of these compounds as radiopharmaceuticals/ ... 

C—H activation/functionalization reactions represent one of the classes of chemical transformations that have been most intensively studied in recent years. Poly-NHC metal complexes have a long-standing tradition of involvement as catalysts in these processes, which can be tracked back to their stability under the relatively harsh reaction conditions that are often needed to drive such reactions to completion in a reasonable time. For example, the group of Strassner reported already in 2002 that paUadium(II) complexes with chelating dicarbene ligands can catalyze the... 

Direct arylation can be very efficiently catalyzed also by other metal centers besides paUadium(II), in particular rhodium(III) and ruthenium(II). In 2009, the groups of Ozdemir and Bruneau jointly reported on the catalytic activity of ruthenium(II) compounds with o-xylylene-bridged, chelating dicarbene ligands for the direct arylation of 2-phenylpyridine. Good catalytic efficiencies were observed even with aryl chlorides as substrates, so that the process resulted in the predominant formation ofbis-o-arylated products (Fig. 20). ... 

Chelating Carbene Ligands and Metal Complexes Potentially, bidentate coordinating dicarbenes are accessible by alkylation of 1-methylimidazole with 1,3-dibromopropane to produce bis(imidazolium bromides) (Scheme 2.162) [52]. The benefits of its high water solubility were utiUzed when an aqueous solution of the bromide was treated with 2 equiv of NH4PF5 to produce the corresponding hexafluorophosphate. Addition of [Rh(COD)Cl]2 to the latter in THF and subsequent deprotonation with an excess of KOtBu afforded a cationic Rh(COD) complex [47]. Replacement of COD by CO could be realized in... 

Methylation of the dihaptothioacyl complex 22 affords compound 23 containing a bidentate carbene ligand, which on reaction with chloride ion leads to the neutral monodentate carbene complex 24 (50,51). The chelate carbene complex 26 is generated in a novel interligand reaction from the thiocarboxamidothiocarbonyl cation 25. The thiocarbonyl carbon acts as the electrophilic component in this reaction, and 26 is further alkylated to a bidentate dicarbene species (52). 

First attempts to isolate monocarbene-hydrido complexes by oxidative addition of A -(2-pyridyl)imidazolium cations to Pd° with utilization of the chelate effect of the donor-functionalized carbene ligand failed and only the dicarbene complexes such as 29 were isolated [112]. The iridium hydrido complex 30 was obtained in the oxidative addition of an W-(2-pyridylmethyl)imidazolium cation to iridium(I) (Fig. 11) [113]. This reaction proceeds most likely via the initial coordination of the nitrogen donor which brings the imidazolium C2-H bond in close proximity to the metal center. No reaction was observed with Rh under these conditions. 

Sluijter SN, Elsevier CJ. Synthesis and reactivity of heteroditopic dicarbene rhodium(I) and iridium(I) complexes bearing chelating 1,2,3-triazolylidene—itnidazolylidene ligands. Organometallics. 2014 33 6389-6397. 

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