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Kekule diradicaloids derived from a classical N-heterocyclic carbene.

ABSTRACT: The direct double carbenylation of 1,4-diiodobenzene and 4,4'-dibromobiphenyl with a classical N-heterocyclic carbene, SIPr (1) (SIPr = :C{N(2,6-iPr₂C₆H₃)}₂CH₂CH₂), by means of nickel catalysis gives rise to 1,3-imidazolinium salts [(SIPr)(C₆H₄)(SIPr)](I)₂ (2) and [(SIPr)(C₆H₄)₂(SIPr)](Br)₂ (3) as off-white solids. Two-electron reduction of 2 and 3 with KC₈ cleanly yields Kekulé diradicaloid compounds [(SIPr)(C₆H₄)(SIPr)] (4) and [(SIPr)(C₆H₄)₂(SIPr)] (5), respectively, as crystalline solids. Structural parameters and DFT as well as CASSCF calculations suggest the closed-shell singlet ground state for 4 and 5. Calculations reveal a very low singlet-triplet energy gap ?E_S-T for 5 (10.7 kcal mol^-1), while ?E_S-T for 4 (29.1 kcal mol^-1) is rather large.

SUBMITTER: Rottschafer D

PROVIDER: S-EPMC5989652 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Kekulé diradicaloids derived from a classical N-heterocyclic carbene.

Rottschäfer Dennis D Neumann Beate B Stammler Hans-Georg HG Andrada Diego M DM Ghadwal Rajendra S RS

Chemical science 20180424 22

The direct double carbenylation of 1,4-diiodobenzene and 4,4'-dibromobiphenyl with a classical N-heterocyclic carbene, SIPr (1) (SIPr = :C{N(2,6-iPr2C6H3)}2CH2CH2), by means of nickel catalysis gives rise to 1,3-imidazolinium salts [(SIPr)(C6H4)(SIPr)](I)2 (2) and [(SIPr)(C6H4)2(SIPr)](Br)2 (3) as off-white solids. Two-electron ...[more]

PMID: 29938024

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