Group 4 and 5 metal derivatives of 2,2′-methylene-bis(6-phenylphenoxide)

Addition of the phenol 2,2'-methylene-bis( 6-phenylphenol) [(HOC6H3Ph)(2)CH2] (1) (1 equiv. per Ti) to hydrocarbon solutions of [TiCl4] or [Ti(OPri)(4)] leads to dimeric products [Ti{(OC6H3Ph)(2)CH2}Cl-2](2) (2) and [Ti{(OC6H3Ph)(2)CH2}(mu-OPri)(OPri)](2) (3). Structural studies show 2 (CHCl3 solvate) to consist in the solid state of two tetrahedral titanium centers linked by one end of two di-aryloxide ligands. Tn contrast, 3 contains five-coordinate titanium atoms linked directly by two bridging isopropoxide ligands. Treatment of [MCl5] (M=Nb, Ta) with 1 equiv. of 1 leads to sparingly soluble trichlorides 4 and 5 which react with pyridine to form soluble adducts [M{(OC6H3Ph)(2)CH2}Cl-3(py)] (M = Nb, 6; M=Ta, 7). Compounds 6 and 7 are isostructural in the solid state (benzene solvates) with a mer arrangement of chloride groups and the pyridine trans to one of the di-aryloxide oxygen atoms. Treatment of 7 with PMe2Ph leads to the products [Ta{(OC6H3Ph)(2)CH2}Cl-3(PMe2Ph)] (8) and [HPMe2Ph] [Ta{(OC6H3Ph)(2)CH2}Cl-4] (9). Structurally characterized 9 (benzene solvate) presumably arises via the presence of trace amounts of water during workup. Reaction of 1 with [Ta(NMe2)(5)] allows isolation of derivatives [Ta{(OC6H3Ph)(2)CH2}(2)(NMe2)(HNMe2)] (10) (cis-nitrogen atoms by NMR) and [H2NMe2][Ta{(OC6H3Ph)(2)CH2}(3)] (11) depending on the stoichiometry. The anion in 11 was shown by crystallography to contain an octahedral arrangement, of oxygen atoms about the tantalum metal center. The crystallographic study of 11 is complicated by a disorder of the cation and partial occupancies for the three types of benzene solvate molecule. The niobium trichloride 4 acts as a catalyst precursor for benzene hydrogenation although with lower activity than reported for monodentate aryloxide precursors. During the catalysis the ortho-phenyl rings of the di-aryloxide ligand are not hydrogenated. (C) 2000 Elsevier Science Ltd All rights reserved.