Abstract
We report on the synthesis of mono(aryloxido)titanium(IV) complexes of general formula {Ti[O(o‐R)Ar]X~3~}, with X = O__i__Pr, ArO = 2‐tert‐butyl‐4‐methylphenoxy and R = CMe~3~ (2a), CMe~2~Ph (2b) and CH~2~NMe~2~ (2c). Attempts to reach pure mono(aryloxido) complexes when R = CH~2~NMe(CH~2~Ph) (2d) or CH~2~N(CH~2~Ph)~2~ (2e) were unsuccessful. When R = CH~2~OMe, the analogous mononuclear complex was not obtained, and instead, a dinuclear complex [(2‐tert‐butyl‐4‐methyl‐6‐methoxymethylphenoxy) TiCl(O__i__Pr)(μ~2~‐O__i__Pr)~2~TiCl(O__i__Pr)~2~] (3) was formed. Complexes 2b and 3 were characterized by single‐crystal X‐ray diffraction. The former contains a tetrahedrally coordinated Ti^IV^ centre, whereas in the latter the aryloxido ligand behaves as a chelating–bridging ligand between the two, chemically very different metal centres that form two face‐sharing octahedra. Different synthetic approaches starting from [Ti(O__i__Pr)~4~] or [TiCl(O__i__Pr)~3~] were evaluated and are discussed. The hemilabile behaviour of the aryloxido ligand resulting from reversible coordination of its side arm was studied by variable‐temperature ^1^H NMR spectroscopy for 2c (R = CH~2~NMe~2~). Complexes 2a–d were contacted with ethylene and AlEt~3~ as cocatalyst. When activated with AlEt~3~ (3 equiv.) at 20 bar and 60 °C, complex 2c exhibits interesting activity (2100 g/gTi/h) for the selective dimerization of ethylene to 1‐butene (92 % C~4~^=^; 99^+^% C~4~^=1^). Noticeable differences in catalyst activity were observed when the R group was modified. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)