Stereoselective Dihapto-Binding of Prochiral Aromatic Compounds by TpRe(CO)(PMe3): Synthesis, Characterization, Stability, and Enantiofacial Discrimination (Tp = hydrido(tris)pyrazolylborate)

Synthetic access to {TpRe(CO)(PMe₃)} and the ability of this fragment to bind unsaturated compounds are reported. A variety of complexes of the type TpRe(CO)(PMe₃)(η²-L) (L = cyclohexene, cyclopentene, naphthalene, phenanthrene, thiophene, 2-methylthiophene, furan, or acetone) have been isolated and characterized, and stereochemical and stability issues of aromatic molecules bound to {TpRe(CO)(PMe₃)} are discussed in detail. In particular, a solid-state structural study of TpRe(CO)(PMe₃)(η²-cyclohexene) has provided a foundation for a discussion of the stereoelectronic features of the Re(I) fragment, and substitution reactions of an aromatic ligand by acetone provide insight into the stability of these aromatic complexes. In addition, a solid-state X-ray diffraction study of the Re(II) complex TpRe(CO)(PMe₃)(OTf) (OTf = trifluoromethanesulfonate) is presented.