A New Route to Chelating Bis(aryloxide) Ligands and Their Applications to Tantalum and Titanium Organometallic Compounds

A new route to sterically tuned, chelating bis(aryloxide) ligands is described and demonstrated by the synthesis of 2,2‘-ethylenebis(6-isopropylphenol) (1, H2BIPP) and transition metal complexes of its dianion. The utility of these ligands in titanium and tantalum organometallic chemistry is shown in the alkylation of (BIPP)TiCl2 (7) to form (BIPP)TiMe2 (8) and (BIPP)Ti(CH2Ph)2 (9) and in the alkylation of (BIPP)TaCl3 (10) and its base adducts to form (BIPP)TaMe3 (14) and (BIPP)Ta(CH2Ph)3 (13). Structural comparisons of the chelating 2,2‘-ethylenebis(6-isopropylphenoxide) (BIPP) ligand with its analogous, nonchelating bis(2,6-dialkylaryloxide) ligand set are examined in the X-ray diffraction studies of (BIPP)TaCl3(THF)·THF (11·THF) and (BIPP)Ta(CH2C6H5)3 (13).