Crystal structures of (μ(2)-η(2),η(2)-4-hydroxybut-2-yn-1-yl 2-bromo-2-methylpropanoate-κ(4) C (2),C (3):C (2),C (3))bis[tricarbonylcobalt(II)](Co—Co) and [μ(2)-η(2),η(2)-but-2-yne-1,4-diyl bis(2-bromo-2-methyl­propanoate)-κ(4) C (2),C (3):C (2),C (3)]bis[tricarbonylcobalt(II)](Co—Co)

The title compounds, [Co(2)(C(8)H(11)BrO(3))(CO)(6)], (1), and [Co(2)(C(12)H(16)Br(2)O(4))(CO)(6)], (2), result from the replacement of two carbonyl ligands from dicobalt octa­carbonyl by the alkynes 4-hy­droxy­but-2-ynyl 2-bromo-2-methyl­propano­ate and but-2-yne-1,4-diyl bis­(2-bromo-2-methyl­propano­ate), respectively. Both mol­ecules have classic tetra­hedral C(2)Co(2) cluster cores with the Co(II) atoms in a highly distorted octa­hedral coordination geometry. The alkyne ligands both adopt a cis-bent conformation on coordination. In the crystal structure of (1), classical O—H⋯O and non-classical C—H⋯O contacts form inversion dimers. These combine with weak O⋯O and Br⋯O contacts to stack the mol­ecules into inter­connected columns along the b-axis direction. C—H⋯O and C—H⋯Br contacts stabilize the packing for (2), and a weak Br⋯O contact is also observed. Inter­connected columns of mol­ecules again form along the b-axis direction.