New clusters [Co-2(CO)(6)] (2)(mu-HC2RC2H) [R=C6H4(CO2CH2)(2)-1,2 2, CH2OCH
2 3, (CH2)(5) 4] have been isolated from the reaction of Co-2(CO)(8) 1 with
diyne ligands HC equivalent to CRC equivalent to CH, and the structure of
2 has been established by single-crystal X-ray diffraction methods.