(Pyrazolylborato)zinc - Aldehyde complexes

The zinc hydroxide complex Tp(Cum,Me)Zn-OH [1, Tp(Cum,Me) = tris(3 -cumenyl -5-methylpyrazolyl)borate] reacts with trichloroacetaldehyde and pentafluor obenzaldehyde to form the complexes Tp(Cum,Mo)Zn-O(CHOH)R, containing the a ldehyde ligands as the deprotonated aldehyde hydrates. 1 and 2-formylphenol , 2,6-diformylphenol and 2-formylthiophenol undergo condensation with the f ormation of the corresponding phenolate and thiophenolate complexes, in whi ch 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 bond ing modes, which were confirmed by three structure determinations, represen t two new kinds of aldehyde attachment to transition metal centers.