Titanium η1-pyrrolyl complexes:: Electronic and structural characteristics imposed by the N,N-di(pyrrolyl-α-methyl)-N-methylamine (dpma) ligand

A new tridentate pyrrolyl-based ligand (dpma) has been utilized in the syntheses of two unusual titanium complexes. The trigonal bipyramidal species allow direct structural comparison between dialkylamido, pyrrolyl, and amine ligands within the same coordination sphere. Pyrrolyl ligands have greatly reduced π-donating ability relative to dialkylamides, which leads to Ti-N(pyrrolyl) distances that are ∼0.14 Å longer than the dimethylamido substituents. Reduced π-donation relative to dialkylamido by the pyrrolyl substituents seems to result in enhanced Lewis acidity for dpma derivatives.