Synthesis and characterisation of some dimeric η2-diyne compounds of cobalt

Abstract

The organometallic dimers [{Co2(CO)6}2(diyne)] [diyne = C6H4(CO2CH2C2H)2-1,2 1, HC2CH2OC6H4OCH2C2H 2 or HC2(CH2)5C2H 3] have been synthesized from reactions between [Co2(CO)8] and the appropriate diyne ligands. However, the reaction of [Co2(CO)8] with diprop-2-ynyl ether HC2CH2OCH2C2H under similar conditions gave the expected product [{Co2(CO)6}2(µ-HC2CH2OCH2C2H)] 4 and the unexpected product [Co4(CO)10(µ-CO){µ4-η∶η3-CC(CH2OCH2)CCH2}] 5. The products have been characterised by infrared, 1H NMR spectroscopy and C/H analyses, and 2, 4 and 5 also by single-crystal X-ray crystallography. In 2 and 4 both “yne” fragments of the diyne ligand are bonded to a Co2(CO)6 fragment with the CC vector essentially perpendicular to the Co–Co vector. However, in 5 hydrogen migration and new C–C bond formation has led to novel structural features, such as µ3-CCo3 and η3-C3Co units and a “C4O” ring.