Abstract
The synthesis of the new chiral ligand (3,5‐di‐tert__butylpyrazol‐1‐yl)(3′,5′‐dimethylpyrazol‐1‐yl)aceticacid (bpaH^t^^Bu2,Me2^) (4) has been achieved. Two different synthetic routes to its precursor 3,5‐di‐tert‐butyl‐1‐[(3,5‐dimethyl‐1__H‐pyrazol‐1‐yl)methyl]‐1__H__‐pyrazole (bpm^t^^Bu2,Me2^) (3) are reported. Deprotonation at the methylene group, followed by reaction with carbon dioxide, yielded a racemic mixture of 4. The chemical behaviour of bis(3,5‐di‐tert‐butylpyrazol‐1‐yl)acetic acid (bd__t__bpzaH) (2) and the new chiral N,N,O scorpionate ligand 4 involving their coordination to zinc ions was studied. [Zn(bpa^t^^Bu2,Me2^)Cl] (5) was formed from a mixture of ZnCl~2~, 4 and base. Reaction of bis(3,5‐di‐tert‐butylpyrazol‐1‐yl)acetic acid (bd__t__bpzaH) (2) with Zn(CH~3~)~2~ or Zn(CH~2~CH~3~)~2~ gave the alkylzinc complexes [Zn(bd__t__bpza)(CH~3~)] (6) and [Zn(bd__t__bpza)(CH~2~CH~3~)] (7). [Zn(bpa^t^^Bu2,Me2^)(CH~3~)] (8) was obtained from a synthesis analogous to that of 6 with 4. The further reactions of 6 and 8 with acetic acid resulted in the acetato complexes [Zn(OAc)(bd__t__bpza)] (9) and [Zn(OAc)(bpa^t^^Bu2,Me2^)] (10). The chiral methyl complex 8 may serve as a precursor for structural model complexes of the active sites of zinc enzymes, such as thermolysin or carboxypeptidase A. [Zn(bpa^t^^Bu2,Me2^)~2~] (11) was formed from a side reaction. Crystal structures of 4, 5, 8 and 11 were obtained; 5 crystallised as the dimer [Zn(bpa^t^^Bu2,Me2^)Cl]~2~; 11 presents an unusual zinc binding geometry. (© Wiley‐VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003)