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 β-β 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. This looks like a good spot for Si: The treatment of an antiaromatic norcorrole Ni^II complex with a kinetically stabilized silylene provided ring-expansion products in excellent yields by highly regioselective insertion into the β-β pyrrolic C-C bonds. The absorption spectrum of the resulting silicon-containing Ni^II porphyrinoid is substantially red-shifted into the near-infrared region.