Homo- and Heteropolymetallic Complexes of the Hybrid, Ambidentate N-Heterocyclic Carbene Ligand IMes-acac.

The anionic 5-acetylimidazol-2-ylidene-4-olate , named as "IMes-acac", is composed of fused diaminocarbene and acetylacetonato units in the same IMes-based imidazolyl ring. The bifunctional compound is shown to act as an effective, ditopic bridging ligand for transition metal centers. Several new complexes supported by this ligand were prepared, including the complex [RuCl(-Cym)(κ ,-·H)](BF) (), which can be regarded as a metallated imidazolium salt, the homobimetallic complex [((COD)Rh)(RhCl(COD))(μ-1κ ,:2κ -)] (), the heterobimetallic complexes [((-Cym)ClRu)(RhCl(COD))(μ-1κ ,:2κ -)] (), [((-Cym)ClRu)(RhCl(CO))(μ-1κ ,2κ -)] (), [((-Cym)ClRu)(Cu(IPr))(μ-1κ ,:2κ -)] (), the anionic homoleptic Cu(I) complexes [Cu(κ -)]K ([]K) and [Cu(κ -)](NEt) ([](NEt)), and the heterotrimetallic complex [((-Cym)RuCl)(Cu)(μ-1κ ,:3κ -)(μ-2κ ,:3κ -)](PF) ().

IMes-acac: hybrid combination of diaminocarbene and acetylacetonato sub-units into a new anionic ambidentate NHC ligand.

The mesoionic 5-acetylimidazolium-4-olate serves as precursor for an anionic, hybrid NHC, "IMes-acac", consisting of fused diaminocarbene and acetylacetonato units, whose respective coordination abilities are evaluated by the formation of a series of representative copper(I) complexes illustrating the ambidentate character of the ligand.

Regioselective desymmetrization of diaryltetrahydrofurans via directed ortho-lithiation: an unexpected help from green chemistry.

An efficient functionalization of diaryltetrahydrofurans via a regioselective THF-directed ortho-lithiation is first described. This reaction can be successfully carried out in cyclopentyl methyl ether as a "greener" alternative to Et2O, with better results in terms of yield and selectivity and, surprisingly, also in protic eutectic mixtures competitively with protonolysis.

Gated access to α-lithiated phenyltetrahydrofuran: functionalisation via direct lithiation of the parent oxygen heterocycle.

Cycloreversion of α-lithiated phenyltetrahydrofuran was successfully tamed at -78 °C in a non-coordinating solvent in the presence of TMEDA. This anion showed excellent nucleophilicity and could be intercepted with a variety of structurally different electrophiles to give 2,2-disubstituted derivatives which can be further elaborated to γ-butyrolactones.