Alkoxyberyllium tetrahydroborates: t-butoxyberyllium pentane-2,4-dionate and complexes of t-butoxyberyllium oxide

Abstract

The tetrahydroborates Me₂EtCOBeBH₄ and Et₃COBeBH₄ are dimeric in contrast to monomeric (BH₄)₂Be₃(OBu^t)₄. t-Butoxyberyllium tetrahydroborate is unreactive to olefins and does not reduce acetone or benzophenone in toluene, but reduces benzophenone in ether. With acetone and tetrahydrofuran, the oxide, {Bu^tOBe(thf)}₂O, is formed, and pyridine gives {Bu^tOBe(py)}₂O. The pentane-2,4-dionato-complex, {Bu^tOBe(C₅H₅O₂)}₂, is formed from the diketone and either Bu^tOBeBH₄ or Bu^tOBeMe. Reaction of pentane-2,4-dione with t-butoxy-beryllium tetrahydroborate appears to proceed by two competing paths, one leading to the pentane-2,4-dionate mentioned above and the other to reduction of the dione giving 4,6-dimethyl-1,3,2-dioxaborinan, which was also synthesised from diborane and either pentane-2,4-dione or pentane-2,4-diol.