Synthesis, structure and properties of mixed-sandwich cobalta- and ferra-carboranes with ‘carbon-atoms-adjacent’ C2B9 and C2B10 systems

Several ‘carbon-atoms-adjacent’ mixed sandwich cobalta- and ferra-carboranes incorporating the C2B10 and C2B9 systems were synthesized via salt metathesis reactions followed by the oxidation with oxygen, which included unexpected cobaltacarboranes [(η5-C5H5){η6-[C6H4(CO)(CH2)]C2B10H10}]Co and [(η5-C5H5){η6-[C6H4(CHOH)(CH2)]C2B10H10}]Co. All new metallacarboranes were characterized by various spectroscopic techniques, elemental analyses and single-crystal X-ray diffraction studies. The electrochemical data suggest that cyclopentadienyl is the most electron-rich ligand followed by the C2B9 and then C2B10 systems, and ‘carbon-atoms-adjacent’ C2B10 system is more electron-donating than its ‘carbon-atoms-apart’ counterpart.

Graphical abstractNew ‘carbon-atoms-adjacent’ mixed sandwich cobalta- and ferra-carboranes were synthesized and structurally characterized. The electrochemical data suggest that cyclopentadienyl is the most electron-rich ligand followed by the C2B9 and then C2B10 systems, and ‘carbon-atoms-adjacent’ C2B10 system is more electron-donating than its ‘carbon-atoms-apart’ counterpart.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesis of ferra- and cobalta-carboranes with ‘carbon-atoms-adjacent’ C2B10 and C2B9 systems. ► X-ray structures of all new complexes. ► Electron-donating ability as suggested by electrochemical data: Cp− > [7,8-C2B9H11]2− > [7,8-C2B10H12]2− > [7,9-C2B10H12]2−.