Triorganyl- and Diorganyloxozirconium Hydridoborates – Synthesis and Structures


  • Metal Hydridoborates and Hydridoborato Metallates, 34. Part 33: Ref.17


The reactions of Zr(OBu)4 and Zr(OEt)4 with H3B·THF in THF led to HB(OR)2 and B(OR)3, but no zirconium tetrahydroborate [(RO)4–nZr(BH4)n] could be isolated. On the contrary, the reactions of [tBu3CO]4–nZrCln and [tBu3SiO]4–nZrCln with LiBH4 generated the tetrahydroborates [(RO)3Zr(BH4)] and [(RO)2Zr(BH4)2]. These can be used to produce by hydroborate exchange dihydridodiorganyl borates [(RO)4–nZr(H2BC8H14)n] and byproducts. The structures of the new zirconium hydridoborates have been determined by X-ray crystallography. Compound [(tBu3CO)3Zr(H2BC8H14)] shows site-disordered dihydroborate units with agostic Zr–H–C interactions, while [(tBu3SiO)2Zr(H2BC8H14)2] is quite symmetric (C2/c). The corresponding tetrahydridoborates possess in most cases μ31-bonded ZrH3BH groups.