Rh2[(R)-(+)-MTPA]4 as an NMR auxiliary for the enantiodifferentiation of chiral secondary and tertiary phosphine–borane complexes

Abstract The direct chiral recognition of secondary and tertiary phosphine–borane complexes is made possible by applying the dirhodium method (NMR in the presence of Rh 2 [( R )-(+)-MTPA] 4 , Rh ∗ ). Due to the acid lability of the phosphine–borane complexes, it is advisable to use deuterated benzene as solvent rather than deuterated chloroform. The decomposition of the phosphine–borane complexes and the resulting Rh ∗ –phosphine adducts are also studied.