Zr-IV and Ta-V complexes with methane-bridged bis(aryloxy) ligands

The bis(aryloxy) ligand precursor compounds bis(2-trimethylsiloxy-5-tbutylp henyl)methane (L-SiMe3) and its bromoderivative (2-trimethylsiloxy-3-bromo- 5-tbutylphenyl)(2'-trimethylsiloxy-5'-tbutylphenyl) (L-Br-SiMe3) are prepar ed in analogy to the corresponding calixarenes in excellent yields. X-ray s tructure analysis for L-Br-SiMe3: space group P2(1)/c, a = 12.462(7), b = 1 0.466(6), c = (14) Angstrom, beta = 105.02(4)degrees, V = 2937(3) Angstrom( 3), Z = 4. L-SiMe3 and L-Br-SiMe3 react with Zr-IV and Ta-V chlorides in ve ry good yields forming di- and trinuclear complexes. From the reaction of C pZrCl3 with L-Br-SiMe3 in the ratio of 3:2 a Zr-3 complex (7) is obtained, with one L-Br ligand only, which Zr atoms are bridged by a mu(3)-oxygen. Th e X-ray structure analysis of 7 (space group R (3) over bar, a = 33.23(6), c = 24.47(8) Angstrom, V = 23405(128) Angstrom(3) Z = 18) additionally reve als that one phenolate oxygen atom of the L-Br ligand is terminally bound t o a distorted tetragonal-pyramidal coordinated Zr atom, while the second ph enolate oxygen atom of the L-Br ligand forms a bridge to another Zr atom wi th a distorted octahedral coordination. The third Zr atom is also found in a distorted octahedral coordination made. The reactions of L-SiMe3 and L-Br -SiMe3 with CpTaCl4 and TaCl5 yield dinuclear Ta complexes with a bridging bis(aryloxy) ligand. NMR spectroscopic data point out that the coordination of the bis(aryloxy) ligands in the Ta complexes very much resembles that i n the Zr-3-complex with one terminal and one bridging phenolate oxygen atom . The Zr-3 and the Ta complexes (LTa2Cp2Cl6)-Ta-Br and LTa2Cl8 were tested with respect to their catalytic properties in olefin polymerisation reactio ns in the presence of MAO.