Synthesis and Structures of Cobalt(II) Coordination Compounds with Isomeric Forms of Octadecahydroeicosaborate Anion

Coordination compounds [Co(DMF)6][B20H18] containing isomeric forms of the macropolyhedral cluster [trans-B20H18]2– and [iso-B20H18]2– have been synthesized. Complex [Co(DMF)6][trans-B20H18] has been prepared by the reaction of a salt of the boron cluster anion with cobalt(II) chloride in dimethylformamide; complex [Co(DMF)6][iso-B20H18] has been isolated when recrystallized from water during spontaneous isomerization of the macropolyhedral cluster. The coordination compounds have been identified by IR spectroscopy, 11B NMR spectroscopy, and X-ray diffraction analysis.