Thio(bisphenolato) complexes of the type [M₂(µ-tbop-κ³O,S,O)₂Cl₄] [M = Zr 1, Hf 2 and tbop = 2,2′-thiobis{4-(1,1,3,3-tetramethyl-butyl)phenolate}] were prepared by HCl elimination from tbopH₂ and MCl₄. Substitution of the chlorides in 1 and 2 by 2,6-diisopropylphenolato groups (dipp) generates new compounds [M₂(µ-tbop-κ³O,S,O)₂(dipp)₄] (M = Zr 3, Hf 4). The structures of 1–4 were confirmed by NMR spectroscopy; complexes 3 and 4 were further investigated by X-ray crystallography. These studies showed 1–4 to be dimers either in the solid state or in solution and to have metal centers adopting distorted octahedral geometry. However treatment of MCl₄ with [Al₂(µ-OEt)₂(tbop-κ³O,S,O)₂] or [Al₂(µ-tbop-κ³O,S,O)₂Me₂] gave heterotrinuclear complexes [M(tbop-κ³O,S,O)₂Cl₂(µ-AlX₂)₂] (M = Zr, X = Cl 5, X = Me 7 and M = Hf, X = Cl 6, X = Me 8) for which the single-crystal X-ray diffraction analysis showed zirconium and hafnium centers to have eight-coordinate dodecahedral geometry. Complexes 1–6 after activation with aluminium alkyls and supporting on MgCl₂ showed a lack of activity in the ethene polymerization process and moderate activity towards 1-hexene producing high molecular weight atactic poly(1-hexenes).