Chemistry of selenium and tellurium with tetrachelate and macrocyclic ligands

Treatment of meso(tetra-p-tolyl)porphryin, H₂(TTP), or Li₂(TTP) with OSeCl₂ or OSe(NMe₂)₂ in toluene or THF resulted in the formation of the diprotonated porphyrin, [H₄(TTP)]Cl₂ and indicated the reluctance of selenium to insert into the porphyrin core. The molecular structure of [H₄(TTP)]Cl₂ was determined by single-crystal X-ray diffraction and exhibited the typical saddle-shape distortion of diprotonated porphyrins. The molecular structure of (p-MeO-Ph)₂Te(salen) was reexamined by X-ray diffraction. The geometry of the Te(IV) center is strongly influenced by a stereochemically active lone pair and is best described as having an AX₄E disphenoid structure in which the salen oxygen atoms occupy axial positions and the two anisyl ligands reside in equatorial sites. Distances between Te and the salen nitrogen atoms are 2.852(3) and 2.984(3) Å and are largely nonbonding.