Induction of atropisomeric chirality on heavily substituted phosphametallocenes

The solution behavior of the diphospha- and the monophosphametallocenes with (-)-menthyl substituents was investigated by variable-temperature NMR measurements in toluene-d(8). Because of the bulky and chiral (-)-menthyl substituents which restrict the rotation of the eta(5)-phospholyl/ eta(5)-cyclopentadienyl ligands with respect to each other, the tetra[(-)-menthyl]phosphometallocenes were observed as mixtures of two slowly interconverting diastereomers.