Reaction of Ti (OiPr) 4 with various bis (β-diketones) and bis (β-ketoesters)(LH2) results in the formation of dimeric complexes [Ti (OiPr) 2L] 2, where each metal centre is coordinated by two terminal OiPr ligands and two bridging β-diketonate or β-ketoesterate groups (L). Macrocycles containing two M (OiPr) 2 moieties are thus formed. Reaction of Zr (OiPr) 4 with the same bis (β-diketones) and bis (β-ketoesters) results in different compounds, ...