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

Abstract

ABSTRACTB−H⋯π interaction has attracted increasing attention after its experimental and theoretical verifications in [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 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.