title: Crystal structures of (μ2-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 [μ2-η(2),η(2)-but-2-yne-1,4-diyl bis(2-bromo-2-methyl-propanoate)-κ(4) C (2),C (3):C (2),C (3)]bis[tricarbonylcobalt(II)](Co-Co).
abstract: The title compounds, [Co2(C8H11BrO3)(CO)6], (1), and [Co2(C12H16Br2O4)(CO)6], (2), result from the replacement of two carbonyl ligands from dicobalt octa-carbonyl by the alkynes 4-hy-droxy-but-2-ynyl 2-bromo-2-methyl-propano-ate and but-2-yne-1,4-diyl bis-(2-bromo-2-methyl-propano-ate), respectively. Both mol-ecules have classic tetra-hedral C2Co2 cluster cores with the Co(II) atoms in a highly distorted octa-hedral 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 mol-ecules into inter-connected 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. Inter-connected columns of mol-ecules again form along the b-axis direction.
authors.affiliation: Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
authors.forename: C John
authors.initials: CJ
authors.lastname: McAdam
authors.affiliation: Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Moratti
authors.affiliation: Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Robinson
authors.affiliation: Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
authors.forename: Jim
authors.initials: J
authors.lastname: Simpson
authors.affiliation: Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
authors.forename: Roderick G
authors.initials: RG
authors.lastname: Stanley
keywords: alkyne-hexa­carbonyl-dicobalt complex; alkynes; crystal structure