Isobutylberyllium hydride: co-ordination complexes and reactions with olefins. The NNN′N′-tetramethylethylenediamine complex of beryllium hydride

Abstract

Elimination of one molar proportion of 2-methylpropene from di-t-butylberyllium gives a mixture of iso- and t-butylberyllium hydrides. Isobutylberyllium hydride results from the pyrolysis of di-isobutylberyllium or its ether complex; it is a glass, soluble in benzene in which it is extensively associated. Di-t-butylberyllium slowly isomerizes to di-isobutylberyllium at room temperature. The tetrahydrofuran complex of isobutylberyllium hydride is a dimer (BuⁱBeH,THF)₂ in benzene, but the tetramethylethylenediamine (TMED) complex, Buⁱ₂Be₂H₂,TMED, is monomeric. For the reactions of pent-1-ene with BuⁱBeH, BuⁱBeH,OEt₂, and BuⁱBeH,NMe₃ under similar conditions t_½ are in the ratio 1 : 40 : 110.

The preparation of Be₂H₄,TMED, from TMED and the product obtained by pyrolysis of Bu₂ⁱBe,OEt₂ beyond the BuⁱBeH stage is described. The terminal Be–H stretching vibrations result in a strong sharp doublet in the i.r. spectrum at 1787 and 1807 cm.^–1.