Resisting B–H oxidative addition: The divergent reactivity of the o-carborane and carba-closo-dodecaborate ligand substituents

• The CB11H11− ligand substituent is resistant to B–H oxidative addition.
• The CB11H11− ligand substituent allows the isolation of Iridium(I) anions.
• A comparative study of isoelectronic carboranyl phosphine complexes is described.

Here, we report a study of two isoelectronic Ir(I) complexes supported by different carboranyl phosphines, bearing either o-carborane or carba-closo-dodecaborate ligand substituents. The neutral Ir(I) complex containing the o-carboranyl phosphine ligand is not isolable and undergoes spontaneous B–H cyclometalation to afford an Ir(III) hydride. In contrast, the anionic Ir(I) complex supported by a phosphine with a carba-closo-dodecaborate ligand R-group is stable towards B–H activation. This divergent reactivity has important implications for the design of carborane containing ligands for catalysis. Both compounds are fully characterized by multinuclear NMR spectroscopy, HRMS spectrometry, and single crystal x-ray diffraction studies.

The neutral Ir(I) complex containing the o-carboranyl phosphine ligand is not isolable and undergoes spontaneous B–H cyclometalation to afford an Ir(III) hydride. In contrast, the anionic Ir(I) complex supported by a phosphine with a carba-closo-dodecaborate ligand R-group is stable towards B–H activation.Figure optionsDownload as PowerPoint slide