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 degreesC and one of which is a liquid at room temperature. Reactions of the BF4- and BPh4- salts with Co-2(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(...)pi and pi(...)pi interactions. Attempts to prepare carbene derivatives from the functionalized imidazolium salts have also been made.