Beryllium borohydride complexes, L,BeB₂H₈(L = Et₂O, Me₃P, Me₂PH, Et₃P, Me₃N, and Me₂NH) are liquid at room temperature and monomeric in benzene solution. Their formation has been followed tensimetrically. The trimethylphosphine complex, Me₃PBeB₂H₈, absorbs a further mol. of trimethylphosphine giving a solid from which trimethylphosphine–borane and some free trimethylphosphine can be evaporated, leaving a viscous liquid residue, whose infrared spectrum contains the broad absorption at ca. 1750 cm.^–1 characteristic of polymeric beryllium hydride.

The infrared spectrum of beryllium deuteride, prepared from triphenylphosphine and beryllium borodeuteride is compared with that of beryllium hydride.