Monocyclopentadienyl Phenoxido-Amino and Phenoxido-Amido Titanium Complexes: Synthesis, Characterisation, and Reactivity of Asymmetric Metal Centre Derivatives

Reduction of phenol-imine derivatives R'N=CH(3,5-R2C6H2-2OH) (R = tBu; R' = C6H5 1a, p-MeC6H4 1b, Cy 1c, tBu 1d, 2,6-Me2C6H3 1e; R = H; R' = p-MeC6H4 1f; Cy = cyclohexyl) with MBH4 (M = Li, Na) or AlLiH4 in ethyl ether or thf at room temperature affords the phenol-amine compounds R'NHCH2(3,5-R2C6H2-2-OH) 2a-c and 2e,f. The N-R-[2,4-di-tert-butyl]benzo-1-oxa-3-azine species (R = tBu 2d1, 2,6-Me2C6H3 2e1) are obtained by Mannich reaction of 2,4-di-tert-butylphenol with RNH2 in refluxing methanol. Intermediate 2d1 is converted in ethanol at room temperature into N-tert-butyl[2-hydroxy-3,5-di-tert-butyl]benzylaniine (2d), whereas 2e is not obtained from 2e1 by using this procedure. N-alkyl,N-tert-butyl[2-hydroxy-3,5-di-tert-btityl]benzylamine compounds tBuN(R)CH2(3,5-tBu(2)C(6)H(2)-2-OH) (R = Me 2g, Et 2h, nPr 2i, CH2Ph 2j) are also prepared by the appropriate synthetic method. Treatment of 2a-c with 1 equiv. of TiCpCl3 in the presence of 2.5 equiv. of NEt3 in hexane at room temperature gives the monocyclopentadienyl phenoxido-amido monochloride complexes TiCp[R'NCH2(3,5-tBu(2)C(6)H(2)-2-O)]Cl (R'= C6H5 3a, R'= p-MeC6H4 3b, R'= Cy 3c). The analogous complex Ti(eta(5)-C5H4SiMe2Cl)[C6H5NCH2(3,5-tBu(2)C(6)H(2)-2-O)]-Cl (4a) results from the reaction of 2a with Ti(eta(5)-C5H4Si-Me2Cl)Cl-3. Nevertheless, 2d reacts with TiCpCl3 in hexane in the presence of NEt3 at room temperature yielding the monocyclopentadienyl phenoxido dichloride compound TiCp[tBuNHCH(2)(3,5-tBu(2)C(6)H(2)-2-O)]Cl-2 (5), whereas in ethyl ether and in the absence of NEt3 adduct 5 center dot HCl is obtained, which is further converted into TiCp[tBuNCH(2)(3,5-tBu(2)C(6)H(2)-2-O)]Cl (3d) by addition of a NEt3/ethyl ether solution. The reaction of TiCPCl3 with 2a in the presence of 2.5 equiv. of NEt3 in a polar solvent (thf, CH2Cl2 or toluene) at room temperature affords TiCp[Ph(H)NCH2(3,5-tBu(2)C(6)H(2)-2-O)]Cl (6a) as a mixture of two stereoisomers. All the reported compounds were characterised by the usual analytical and spectroscopic methods and the molecular structures of 2a, 2d, 2e and 3d were determined by X-ray diffraction analysis from suitable single crystals. Preliminary studies of catalytic activity for ethylene polymerisation by using solid methylaluminoxane as cocatalyst were performed. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)