The crystal structure of the title compound has been determined from 2829 independent reflections measured by diffractometer. Crystals are triclinic, space group P, with the (non-conventional) unit-cell parameters, a= 9·492(4), b= 9·754(5), c= 9·243(5)Å, α= 89·91(5)°, β= 90·28(5)°, γ= 108·30(2)°, and Z= 2. The structure was solved by Patterson and Fourier techniques, and refined by full-matrix least-squares methods to R= 3·4%. The compound consists of cobalt(II) ions co-ordinated in a pseudotetrahedral manner to the two nitrogen donor atoms in the ligand and to the two chloride ions. The two Co–CI distances are slightly different [2·219(1) and 2·227(1)Å], and the Co–N (quinoline) bond distance [2·014(2)Å] is somewhat shorter than Co–N (quinuclidinone)[2·064(2)Å]. The bond angles about Co are distorted from their pure tetrahedral value, the smallest being [100·35(9)°] the chelate ‘bite’ angle. The ligand is almost planar (excluding the two ethylene bridges), and the molecule therefore possesses an approximate mirror plane bisecting the Cl–Co–Cl angle.