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)CH 2] (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{(OC6H 3Ph)(2)CH2}(mu-OPri)(OPri)](2) (3). Structural studies show 2 (CHCl3 solvat e) 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-coord inate titanium atoms linked directly by two bridging isopropoxide ligands. Treatment of [MCl5] (M=Nb, Ta) with 1 equiv. of 1 leads to sparingly solubl e 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 isos tructural in the solid state (benzene solvates) with a mer arrangement of c hloride groups and the pyridine trans to one of the di-aryloxide oxygen ato ms. 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 c haracterized 9 (benzene solvate) presumably arises via the presence of trac e amounts of water during workup. Reaction of 1 with [Ta(NMe2)(5)] allows i solation of derivatives [Ta{(OC6H3Ph)(2)CH2}(2)(NMe2)(HNMe2)] (10) (cis-nit rogen 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 catio n and partial occupancies for the three types of benzene solvate molecule. The niobium trichloride 4 acts as a catalyst precursor for benzene hydrogen ation 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 rese rved.