Diaryl Tellurium Dihalides: FromTe-Tetracoordinated Compounds toTe-Tricoordinated Molecular Complexes

X-ray structural studies demonstrate that diaryl tellurium diiodides can be constrained by steric factors (ortho-alkyl substituents) to adopt a trigonal pyramidal structure in preference to the expected bisphenoidal structure. DFT calculations are shown to reproduce successfully structural details of the title compounds; they allow one to predict which coordination number should be energetically favored. All compounds are chiral, but the barrier to stereomutation by intra- and intermolecular pathways (60–85 kJmol−1) is rather low.