Synthesis Of A Hybrid M-Terphenyl/O-Carborane Building Block: Applications In Phosphine Ligand Design

A hybrid terphenyl/o-carborane ligand building block is synthesized by the reaction of m-terphenylalkyne with B10H14. This sterically demanding substituent can be installed into ligands, as demonstrated by the preparation of carboranylphosphine. The bulky phosphine reacts with [ClRh(CO)(2)](2) to produce monophosphine complex ClRhL(CO)(2), which subsequently extrudes CO under vacuum to afford the dimeric species [ClRhL(CO)](2). The latter complex does not react with excess phosphine and is resistant toward cyclometalation, which is in contrast to related o-carborane phosphine complexes. Data from a single-crystal X-ray diffraction study are utilized to quantify the steric impact of the ligand via the percent buried volume approach.