Crystal structures of (μ₂-η²,η²-4-hydroxybut-2-yn-1-yl 2-bromo-2-methylpropanoate-κ⁴C²,C³:C²,C³)bis[tricarbonylcobalt(II)](Co—Co) and [μ₂-η²,η²-but-2-yne-1,4-diyl bis(2-bromo-2-methylpropanoate)-κ⁴C²,C³:C²,C³]bis[tricarbonylcobalt(II)](Co—Co)

Abstract

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.