Organometallic Complexes Derived from Alkyne-Functionalized Imidazolium Salts

Two 1,3-dialkyne-functionalized imidazolium chlorides, 1,3-dipropynylimidazolium chloride
and 1,3-dipentynylimidazolium chloride, have been prepared from the direct reaction between
the appropriate chloroalkyne and (trimethylsilyl)imidazole. Replacement of the chloride
counterion with BF4- or BPh4- gave four further imidazolium salts, three of which melt
below 100 °C and one of which is a liquid at room temperature. Reactions of the BF4- and
BPh4- salts with Co2(CO)8 afforded complexes in which both of the alkyne functionalities
coordinated to a Co2(CO)6 unit. One of these organometallic derivatives, viz. 1,3-dipentynylimidazolium bis(hexacarbonyldicobalt) tetrafluoroborate, can be classified as an ionic liquid
on the basis of its melting point. The solid-state structures of three of these new salts have
been elucidated by single-crystal X-ray diffraction, revealing extensive networks of C···H···π and π···π interactions. Attempts to prepare carbene derivatives from the functionalized
imidazolium salts have also been made.