A Family of Group 4 Metal Alkoxo Complexes with an M 3 ( μ 3 ‐O) Core Relevant to Ziegler–Natta Catalyst Intermediates

Reactions of [Mg(thffo) 2 ] ( 1 ) or [Ca(thffo) 2 ] ( 2 ) with ZrCl 4 or HfCl 4 in a CH 2 Cl 2 /THF/CH 3 CN mixture give thermally stable neutral heterobimetallic tetranuclear complexes [M 3 M′( μ x ‐O)( μ , η 2 ‐thffo) 6 (Cl) 6 ] (thffo=tetrahydrofurfuroxide; M/M′/ x : 3 , Zr/Mg/3; 4 , Hf/Mg/3; 5 , Zr/Ca/4; 6 , Hf/Ca/4) as colorless crystals in 75–82 % yield. X‐ray diffraction studies show complexes 3 – 5 to contain oxo‐bridged M 3 triangles that are capped by an alkaline earth metal‐containing moiety to form species of C 3 symmetry. Reactions of ZrCl 4 and HfCl 4 with pure tetrahydrofurfuryl alcohol in EtOH and MeOH provide ionic complexes [M 3 ( μ 3 ‐O)( μ , η 2 ‐thffo) 3 (L) 3 (Cl) 6 ]Cl (M/L: 8 , Zr/EtOH; 9 , Hf/EtOH; 10 , Zr/MeOH) in 66–79 % yield. Complexes 8 – 10 consist of M 3 triangles that are analogous to those in 3 – 6 and possess similar overall symmetry, as shown by X‐ray crystallography. Changes in the reaction conditions afforded the asymmetric neutral dimer [Zr 2 ( μ ‐thffo) 2 (thffoH)(Cl) 6 ] ( 7 ) and the homometallic [Zr 3 ( μ 3 ‐O)( μ , η 2 ‐thp) 3 (thf) 2 (Cl) 7 ] ( 11 ).