A series of new titanium complexes of the general type Ti(mbmp)X2 (X = Br, I; OMe, OiPr, OtBu), containing a bidentate bis(phenoxy) ligand derived from 2,2'-methylenebis(6-tert-butyl-4-methylphenol) (mbmpH2), was prepared. The 'H-chemical shifts for the protons of the methylene link were found to vary considerably as a function of the ligand X. Reaction of Ti(OiPr)4 with two equivalents of mbmpH2 gave the C2-symmetric spiro-titanate complex Ti(mbmp)2.The crystalline labile solvent adducts of the dichloro complex Ti(mbmp)C12 with THF and DME were isolated and characterized. A single-crystal X-ray structural analysis revealed the THF adduct to be a mono(THF) adduct with a trigonalbipyramidal configuration, the bidentate mbmp ligand spanning an apical and equatorial site and the THF ligand occupying the remaining apical position.Mononuclear titanium complexes Ti(OR)2X2 [(OR), = 2,2'-methylenebis(6-tert-butyl-4-methylphenoxy) (mbmp); 2,2'-thiobis(6-tert-butyl-4-methylphenoxy) (tbmp); X = CI, OiPr] containing bidentate phenoxy ligands derived from the sterically demanding bis(pheno1s) mbmpH2 and tbmpH2 have been reported to polymerize 1 -alkenes, styrene, and 1,3-dienes when activated with methylaluminoxane These soluble titanium phenoxy complexes constitute a new class of homogeneous polymerization catalysts distinct from the well-known ansa-metallocene systems that contain two cyclopentadienyl ligands linked by a covalent bridge (Brintzinger-type ligands). In order to rationally control activity, stereoselectivity, and copolymerization behavior of catalysts based on such bidentate phenoxy ligands, detailed information about the coordination sphere around the titanium center is required. To date, however, only a limited number of transition metal complexes containing the mbmp ligand have been doc~mented[~,~I. Mononuclear titanium complexes of the formula Ti(mbmp)X, with X = Cl, Me, q3-BH4, and X2 = (q5-C5H5)C1 were reported to display a C,-symmetric structure in the solid state with a strongly puckered eight-membered chelate ring in a boat conformati~n[~I. The 'H-NMR chemical shifts for the two methylene protons of the bridge was found to vary considerably as a function of the ligand X, although their relationship with the various conformations of the eight-membered metallacycle remained undefinedL5I. In order to obtain more detailed information about the ligand environment of the Ti(mbmp) fragment, we attempted to augment the number of complexes in this series by preparing mbmp complexes previously not described. We report here that the mbmp ligand forms besides mono(1igand) titanium complexes of the general formula Ti(mbmp)X2(L) (X = anionic ligand, L = two-electron ligand) also a mononuclear bis(1igand) complex (mbmp),Ti with a spirotitanate structure.
Results and DiscussionWhen the easily prepared orange-red dichloro complex Ti(mbmp)C12[31 is treated with halotrimethylsilane Me3SiX (X = Br, I) in hexane for 3 d, the corresponding red-brown dibromo and dark red diiodo derivatives Ti(mbmp)X2 (X = Br, I) are cleanly...