Beryllium chloride reacts with lithium aluminium hydride in ether as 2BeCl2 + LiAlH4 -> 2X + LiCl + AlCl3. Which statement about X is correct?

X is polymeric with Be-H-Be three-centre two-electron bridges and gives hydrogen with water

X is a saline hydride containing discrete H- ions like CaH2

X is a discrete linear monomer that does not react with water

X is a volatile molecular hydride that hydrolyses to give BeO and H2 only

JEE Advanced levelSingle correct optionDifficulty 3 of 3sb075

Beryllium chloride reacts with lithium aluminium hydride in ether as $2 BeCl X_{2} + LiAlH X_{4} 2 X + LiCl + AlCl X_{3}$ . Which statement about X is correct?

AX is polymeric with $Be - H - Be$ three-centre two-electron bridges and gives hydrogen with water
BX is a saline hydride containing discrete $H X^{-}$ ions like $CaH X_{2}$
CX is a discrete linear monomer that does not react with water
DX is a volatile molecular hydride that hydrolyses to give $BeO$ and $H X_{2}$ only

Balancing gives X =

BeH X_{2}

. It is a covalent, polymeric solid with 3c-2e hydrogen bridges (an electron-deficient structure, like

(AlH X_{3}) X_{n}

), not an ionic hydride. It hydrolyses as

BeH X_{2} + 2 H X_{2} O Be (OH) X_{2} + 2 H X_{2}