Synthesis and characterization of Cp*Ir-dithiolene-o-carborane phosphine complexes: A continuous investigation of B−H⋯π interaction

B−H⋯π interaction has attracted increasing attention after its experimental and theoretical verifications in [Cp∗Ir(PR₃)(S₂C₂B₁₀H₁₀)] (R = C₆H₄X, X = H, F, OMe) complexes. In such a template, the entropic factors are excluded by using triphenylphosphines as sterically crowding ligands, which leads to the direct observation of B−H⋯π hydrogen bonds at room temperature in both solution and solid state. In this work, new Cp∗Ir − dithiolene-<i>o</i>-carborane templates with sterically less crowding mono/diphenylphosphine ligands were designed and experimentally synthesised. As a result, non-covalent B−H⋯π hydrogen bonds were detected at low temperatures (down to −80°C) in <b>C1</b> by using low temperature NMR techniques. Furthermore, variable temperature NMR measurement of <b>C0</b> with triphenylphosphine ligation was also performed which indicates the slow rotation of Ir−P bond and the reinforced B−H⋯π interaction at low temperature. These experimental results are consistent with the previous theoretical prediction of the B−H⋯π interaction at low temperature in the B₂H₆⋯benzene model. Additionally, if monophosphine ligand is replaced by diphosphine, a new type of intermolecular B−H⋯π interaction has been crystallographically observed in solid state.