Synthesis of 11-vertex cobalt bis(diphenylphosphine) complexes based on medium-size non-icosahedral carborane 5,6-nido-C2B8H12. Molecular structure of complex [1,1-{κ2-1′,2′-Ph2P(CH2)2PPh2}-1-H-isonido-1,2,4-CoC2B8H10]

The reactions of suspensions of the freshly prepared complexes [Ph₂P(CH₂)_nPPh₂] CoCl₂ (n = 2 (dppeCoCl₂), n = 3 (dpppCoCl₂), n = 4 (dppbCoCl₂); dppe is bis(diphenylphosphino)ethane, dppp is 1,3-bis(diphenylphosphino)propane, dppb is 1,4-bis-(diphenylphosphino)butane) with the salts [Na][R₂C₂B₈H₉] (R = H, Ph), which were obtained in situ by the treatment of carboranes 5,6-nido-R₂C₂B₈H₁₀ (R = H (1a), Ph (1b)) with NaH in THF at room temperature, afforded 18-electron cobaltahydridocarboranes with isonido structures, [1,1-{κ²-Ph₂P(CH₂)_nPPh₂}-1-H-isonido-1,2,4-CoR₂C₂B₈H₈] (R = H, n = 2 (2a), 3 (2b), 4 (2c); R = Ph, n = 2 (2d)). The treatment of nido-carborane 1a with potassium hydroxide followed by the addition of [Ph₂P(CH₂)_nPPh₂]CoCl₂ (n = 2–4) in ethanol at 20 °C resulted in the formation of ethoxy-substituted complexes [1,1-{κ²-Ph₂P(CH₂)_nPPh₂}-1-H-3-(EtO)-isonido-1,2,4-CoC₂B₈H₉] (3a–c, n = 2–4) apart from compounds 2a–c. All the newly prepared compounds were characterized by a combination of elemental analysis, multinuclear NMR spectroscopy, and IR spectroscopy. The structure of complex 2a was studied by X-ray diffraction analysis.