Intramolecular C(sp 3 )−H bond activation reactions mediated by low-valent cobalt, both Co(I) and Co(0), have been observed in the reactions of the three-coordinate cobalt complex [Co(IMes) 2 Cl] (IMes = 1,3-dimesitylimidazol-2-ylidene) with alkylation reagents and sodium amalgam. The reactions with alkylation reagents gave [Co(IMes)(IMes′)(N 2 )], featuring a metalated IMes′ anion, whereas the oneelectron-reduction reaction afforded [Co(IMes′) 2 ]. The Co(II) complex can react with CO, isocyanide, and a diazo compound to furnish interesting cobalt complexes bearing functionalized N-heterocyclic carbene ligands. The establishment of these conversions demonstrates the capability of low-valent cobalt with coordination unsaturation to mediate C(sp 3 )−H bond activation and functionalization.

ethylimidazolium iodide was heated in CH 2 Cl 2 solution with silver oxide to afford a stair polymer of N-heterocyclic carbene silver(I), which gave strong anthracene-type fluorescence. The carbene moiety could be displaced from this polymer by pyridine to afford a known polymer with a similar shape but a tighter framework; this polymer showed an emission band at 579 nm arising from a Ag-Ag interaction.

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The 9-methylanthracene photodimer (6) and lepidopterene (7) were prepared by a photo-dimerisation reaction of 1-(9-anthracenylmethyl)-3-ethylimidazolium iodide (1) or α, α'-di[1-(9-anthracenylmethyl) imidazolium]- p-xylene dibromide (2). Compound 6 is derived from the head-tail [4+4] cycloaddition of two molecular 9-methylanthracenes, and the butterfly-shaped compound 7 is formed via the 9-methyleneanthracene radical in a two steps precess. The single crystal structure of 6 was determined by X-ray diffraction analysis. The changes of luminescent intensities of compounds 1, 2 and 7 are reported.