Synthesis, crystal structure and reactivity of bis(μ-2methylpyridine N-oxide-κ2O:O)bis[dibromido(2-methylpyridine N-oxide-κO)cobalt(II)] butanol monosolvate

Reaction of CoBr2 with 2-methylpyridine N-oxide in n-butanol leads to the formation of the title compound, [CoBr2](2)(2-methylpyridine N-oxide)(4)center dot n-butanol or [Co2Br4(C6H7NO)(4)]center dot C4H10O. The asymmetric unit of the title compound consists of one CoII cation as well as two bromide anions and two 2-methylpyridine N-oxide coligands in general positions and one n-butanol molecule that is disordered around a center of inversion. The Co-II cations are fivefold coordinated by two bromide anions and one terminal as well as two bridging 2-methylpyridine N-oxide and linked by two symmetry-related mu-1,1(O,O) 2-methylpyridine N-oxide coligands into dinuclear units that are located on centers of inversion. In the crystal structure, the dinuclear units are also connected via pairs of C-H...Br hydrogen bonds into chains that elongate in the b-axis direction. The n-butanol molecules are located between the chains and are linked via O-H center dot center dot center dot Br hydrogen bonds each to one chain. Powder X-ray diffraction (PXRD) measurements reveal that a pure phase has been obtained. Measurements using thermogravimetry and differential thermoanalysis shows one mass loss up to 523 K, in which the n-butanol molecules are removed. PXRD measurements of the residue obtained after n-butanol removal shows that a completely different crystalline phase has been obtained and IR investigations indicate significant structural changes in the Co coordination.