The addition of alkylberyllium hydrides to some unsaturated compounds
Organoberyllium hydrides (RBeH; R = Me, Et, Ph) can be prepared, as diethyl ether complexes, from R2Be, BeBr2, and LiH. The liquid diethyl ether complex of methylberyllium hydride is a dimer, (MeBeH,Et2O)2, in benzene like the pyridine complex (MeBeH,py)2. About five-sixths of the ether can be removed from the ether complexes by gentle heating under reduced pressure, whereupon broad infared absorptions develop similar to that of beryllium hydride. Methylberyllium hydride in the presence of ether slowly reduces methyl iodide to methane, and it rapidly adds to benzylideneaniline and to benzaldehyde giving [PhCH2(Ph)NBeMe]2 and (PhCH2OBeMe)4, respectively. Benzophenone in contrast gives the monomeric complexes Ph2CHOBeMe,Et2O and Ph2CHOBeMe, tetrahydrofuran. Sodium diethylberyllium hydride reacts readily with ethylene in the presence of diethyl ether, but very slowly in its absence. Ethylberyllium hydride reacts rapidly with terminal olefins in the presence of ether at ca. 80°, very slowly with pent-2-ene, and no reaction with 2-methylbut-2-ene could be observed. Beryllium hydride adds to pent-1-ene in the presence of a little ethylberyllium hydride, but not detectably in its absence.