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Reactivity of the B−H Bond in Tris(pyrazolyl)hydroborato Zinc Complexes:  Unexpected Example of Zinc Hydride Formation in a Protic Solvent and Its Relevance towards Hydrogen Transfer to NAD+ Mimics by Tris(pyrazolyl)hydroborato Zinc Complexes in Alcoholic Media

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journal contribution
posted on 25.01.2002 by Catherine Bergquist, Lawrence Koutcher, Amanda L. Vaught, Gerard Parkin
Solutions of the zinc hydroxide complex [TpBut,Me]ZnOH in alcohols (ROH; R = Me, Et, Pri) achieve hydride transfer to the NAD+ model, 10-methylacridinium perchlorate. Deuterium labeling studies, however, demonstrate that the source of the hydride is not the alcohol but, rather, the B−H group of the [TpBut,Me] ligand. A further example in which a [TpBut,Me] ligand acts as a hydride donor is provided by the reaction of the aqua complex {[TpBut,Me]Zn(OH2)}[HOB(C6F5)3] with MeOH to generate the zinc hydride complex [TpBut,Me]ZnH. The present study therefore provides a caveat for the often assumed inertness of the B−H group in tris(pyrazolyl)hydroborato ligands, especially in the presence of reactive cationic species.