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

ABSTRACT

B−H⋯π interaction has attracted increasing attention after its experimental and theoretical verifications in [${\mathrm{Cp}}^{\ast }$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 ${\mathrm{Cp}}^{\ast }$Ir − dithiolene-o-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 C1 by using low temperature NMR techniques. Furthermore, variable temperature NMR measurement of C0 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.

GRAPHICAL ABSTRACT

KEYWORDS:

• B−H⋯π interaction
• carborane
• iridium complex
• phosphine

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Natural Science Foundation of China under Grant 21472086 and 21531004.