Novel μ3-oxo complexes prepared from Cp*Zr(BH3R)3 (R = H, CH3) and B(C6F5)3 in diethyl ether

Abstract

From the reactions of Cp*ZrCl₃ with 3 equiv. of LiBH₃R (R = CH₃, Ph), the organotrihydroborate complexes, Cp*Zr(BH₃CH₃)₃, 1, and Cp*Zr(BH₃Ph)₃, 2, were isolated. One of the Zr–H–B bonding interactions in 2 could be described as an intermediate case between the bidentate and tridentate modes. Reactions of 1 and Cp*Zr(BH₄)₃, 3, with Lewis acid B(C₆F₅)₃ in diethyl ether produced the novel 14-electron ionic compounds [(μ₃-O)(μ₂-OC₂H₅)₃{(Cp*Zr(OC₂H₅))₂(BCH₃)}][HB(C₆F₅)₃], 4, and [(μ₃-O)(μ₂-OC₂H₅)₃{(Cp*Zr(OC₂H₅))₂(BOC₂H₅)}][HB(C₆F₅)₃], 5, respectively. These two unique compounds resulted from a sequential cleavage of Zr–H–B bonds of 1 and 3 and C–O bonds of ether followed by the formation of O–B bonds. The solid state single crystal X-ray analyses revealed that both compounds have similar structures. A μ₃-oxygen bridges two zirconiums and a boron atom. The latter three atoms are further connected by three μ₂-bridging ethoxy groups giving rise to three four-membered metallacycles within the structure of each cation.