Lithium and sodium beryllium hydrides

Abstract

Lithium and sodium beryllium hydrides, M₂BeH₄(M = Li or Na), are left as insoluble residues when diethylberyllium is evaporated (160–180°) from mixtures of BeCl₂+ 4MEt₂BeH after removal of MCl. Similar reactions of BeCl₂+ 3MEt₂BeH give products approximating in composition to MBeH₃, but these are believed to consist of M₂BeH₄+ BeH₂ since their X-ray powder patterns contain (with the exception of one weak line in each case) only the lines due to M₂BeH₄. Sodium beryllium hydride dissolves in methanol to give NaBe(OMe)₃,MeOH, and the same product is formed from beryllium and methanolic sodium methoxide.

Somewhat similar hydrides, though of less definite composition ca. M_1–2BeH_2–3, are precipitated when MEt₃AlH reacts in solution with Be(OBu^t)₂, EtBeH, or Et₂Be.

Lithium diethylberyllium hydride crystallises from either as a solvate, LiOEt₂Et₂BeH, m. p. 33–35°, from which ether can be separated at 35–40° under reduced pressure to give benzene-insoluble LiEt₂BeH; at 80° diethylberyllium is lost as well as ether.