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)

Abstract

The structures of two alkyne-hexacarbonyl-dicobalt complexes are reported, each with potential ATRP initiator substrates as substituents on the alkynes. The complexes each form tetrahedral C ₂Co ₂ cluster cores with classical sawhorse conformations, while a feature of the crystal packing is the formation of inversion dimers for both molecules.

Abstract

The title compounds, [Co ₂(C ₈H ₁₁BrO ₃)(CO) ₆], (1), and [Co ₂(C ₁₂H ₁₆Br ₂O 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 ₂Co 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.