Dimethyl Group IV Metal Complexes of the OSO-Type Ligand Bearing AlMe₂ Moieties

Complexes having two ancillary (tbop)2- ligands where tbopH2 = 2,2‘-thiobis{4-(1,1,3,3-tetramethylbutyl)phenol}, viz., [M(tbop-κ3O,S,O)2] (M = Ti, 1; M = Zr, 2; M = Hf, 3), have been prepared in good yields by amine or HCl elimination from tbopH2. The 1H and 13C NMR studies showed that complexes 1−3 adopt in solution mononuclear structures. Treatment of 1−3 with 2 equiv or an excess of AlMe3 generates heterometallic [M(μ-tbop-κ3O,S,O)2Me2(μ-AlMe2)2] (M = Ti, 4; M = Zr, 5; M = Hf, 6) complexes. The structures of 4−6 were confirmed by NMR spectroscopy; complexes 5 and 6 were further investigated by X-ray crystallography. These studies showed 4−6 to be trimers either in the solid state or in solution. The crystals of 5·CH2Cl2 and 6·CH2Cl2 consist of eight-coordinate dimethyl Zr or Hf centers and two AlMe2 moieties attached to oxygen atoms of the tbop ligands. The saturated coordination sphere of the metal centers in 1−6 makes them inactive in ethene polymerization.