(Pyrazolylborato)zinc−Aldehyde Complexes

The zinc hydroxide complex TpCum,MeZn−OH [1, TpCum,Me = tris(3-cumenyl-5-methylpyrazolyl)borate] reacts with trichloroacetaldehyde and pentafluorobenzaldehyde to form the complexes TpCum,MeZn−O(CHOH)R, containing the aldehyde ligands as the deprotonated aldehyde hydrates. 1 and 2-formylphenol, 2,6-diformylphenol and 2-formylthiophenol undergo condensation with the formation of the corresponding phenolate and thiophenolate complexes, in which one formyl group of each is coordinated to the zinc center as part of a six-membered chelate ring. The aldehyde−hydrate and aldehyde−phenolate bonding modes, which were confirmed by three structure determinations, represent two new kinds of aldehyde attachment to transition metal centers.