Search

Bent (hetero)allenes such as carbodicarbenes and carbodiphosphoranes can act as neutral C‐donor ligands, and diverse applications in coordination chemistry have been reported. N‐Heterocyclic diazoolefins are heterocumulenes, which can function in a similar fashion as L‐type ligands. Herein, we describe the synthesis and the reactivity of an anionic diazoolefin. This compound displays distinct reactivity compared to neutral diazoolefins, as evidenced by the preparation of diazo compounds via protonation, alkylation, or silylation. The anionic diazoolefin can be employed as an ambidentate, X‐type ligand in salt metathesis reactions with metal halide complexes. Extrusion of dinitrogen was observed in a reaction with PCl(NiPr2)2, resulting in a stable phosphinocarbene. [ABSTRACT FROM AUTHOR]

The head‐to‐tail dimerization of N‐heterocyclic diazoolefins is described. The products of these formal (3+3) cycloaddition reactions are strongly reducing quinoidal tetrazines. Oxidation of the tetrazines occurs in a stepwise fashion, and we were able to isolate a stable radical cation and diamagnetic dications. The latter are also accessible by oxidative dimerization of diazoolefins. [ABSTRACT FROM AUTHOR]

Homometallic copper complexes with alkenylidene ligands are discussed as intermediates in catalysis but the isolation of such complexes has remained elusive. Herein, we report the structural characterization of copper complexes with bridging and terminal alkenylidene ligands. The compounds were obtained by irradiation of CuI complexes with N‐heterocyclic diazoolefin ligands. The complex with a terminal alkenylidene ligand required isolation in a crystalline matrix, and its structural characterization was enabled by in crystallo photolysis at low temperature. [ABSTRACT FROM AUTHOR]

Ethynylbenziodoxol(on)e (EBX) cyclic hypervalent iodine reagents are now established reagents for the alkynylation of radicals and nucleophiles, yet they present limited possibilities for further structure and reactivity modification. Herein, the first synthesis is reported for the corresponding ethynylbenziodazolone (EBZ) reagents, in which the oxygen atom in the iodoheterocycle is replaced by a nitrogen atom. The substituent on the nitrogen enables further fine‐tuning of the reagent structure and reactivity. EBZ reagents are obtained easily from the corresponding benzamides by using a one‐step procedure, and display reactivity comparable to that of EBX reagents. In particular, they are applied in an asymmetric copper‐catalyzed oxyalkynylation of diazo compounds, which proceeds in high yield and enantioselectivity for a broad range of substituents on the diazo compounds and the alkyne. [ABSTRACT FROM AUTHOR]