Synthesis, crystal structure and reactivity of bis(μ-2-methylpyridine N-oxide-κ2 O:O)bis[dibromido(2-methylpyridine N-oxide-κO)cobalt(II)] butanol monosolvate

Abstract

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·n-butanol or [Co2Br4(C6H7NO)4]·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 CoII 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 μ-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...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.