Mesoionic Janus-Type Dicarbene: Complexes, Adducts, and Catalytic Studies.

The preparations of homo- and hetero-bimetallic complexes as well as thiourea and selenourea derivatives of a mesoionic Janus-type N-heterocyclic dicarbene (diNHC) are reported. Analogues of its monocationic intermediate NHC have also been obtained for comparison. Using the main group adducts, the π-acceptor properties of both NHCs were determined using low temperature 77 Se NMR spectroscopy completing their stereoelectronic profiling. Moreover, catalytic investigations reveal that the mesoionic dipalladium Janus-diNHC complex can be used in the sequential C2- and C5-arylation of 1-methylpyrrole for the preparation of non-symmetrical 2,5-diarylpyrroles.