Cyclic bis(β-diketonate)- and bis(β-ketoesterate)-bridged titanium and zirconium alkoxide derivatives.

Reaction of Ti(OiPr)(4) with various bis(β-diketones) and bis(β-ketoesters) (LH(2)) results in the formation of dimeric complexes Ti(OiPr)(2)L, 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, depending on the organic spacer connecting the two functional groups. With shorter spacers, the compounds ZrL(OiPr)(2)·2iPrOH are obtained, with the same structures as the corresponding titanium complexes. With longer spacers, however, complexes with a higher degree of substitution are formed, such as (ZrL(2))(2) and Zr(2)L(3)(OiPr)(2)·2iPrOH. The molecular weight and structure of all compounds was elucidated by ESI-MS. MS/MS of the corresponding M+Na precursor ions confirmed the proposed structures based on structure-specific product ions. Solution NMR experiments and DFT calculations additionally supported the proposed structures.