Near-IR absorbing nickel(II) porphyrinoids prepared by regioselective insertion of silylenes into antiaromatic nickel(II) norcorrole.

The treatment of an antiaromatic norcorrole Ni(II) complex with a kinetically stabilized silylene provided ring-expansion products in excellent yields through the highly regio- and stereoselective insertion into the ß-ß pyrrolic CC bonds. The resultant Ni(II) porphyrinoid monoinsertion product exhibited relatively strong near-IR absorption bands due to the small HOMO-LUMO gap in spite of the disrupted cyclic π-conjugation by the silicon atom.

Reactions of Antiaromatic Norcorrole Ni(II) Complex with Carbenes.

Norcorrole is a ring-contracted porphyrinoid, exhibiting distinct antiaromaticity. Herein, we report the reactions of meso-dimesitylnorcorrole Ni(II) complex with two types of carbenes: dichlorocarbene and an N-heterocyclic carbene (NHC). The reaction with in-situ-generated dichlorocarbene resulted in the double insertion of two chloromethine units to provide a mixture of 5,15-dichloroporphyrin and chlorinated isopyricorroles. The nucleophilic NHC attacked the 3-position of the norcorrole core and the subsequent proton transfer furnished a nonconjugated macrocycle incorporating a diazafulvene segment.

Modulation of the coordination geometries of NCN and NCNC Rh complexes for ambidextrous chiral catalysts.

A chirality switch between novel NCN pincer Rh complexes and a related double cyclometalated NCNC Rh complex containing secondary amino groups is described. Their catalytic abilities were determined in asymmetric alkynylation of ethyl trifluoropyruvate, and the change in the coordination geometry of the Rh catalysts affected the stereochemistry of the products.