Question

The incorrect statement regarding 'X' in given reaction is :

$BF_3 + LiAlH_4 \xrightarrow{Ether} (X) + LiF + AlF_3$

• A. Twelve electrons are involved in bonding
• B. Four, two centre-two electron bonds
• C. Two, three centre-two electron bonds
• D. X does not react with $NH_3$

Answer 1

Answer: (D)

X does not react with $NH_3$

Answer 2

The reaction between $BF_3$ and $LiAlH_4$ in ether yields diborane ($B_2H_6$). Diborane has 12 valence electrons involved in bonding, four 2-center-2-electron bonds (terminal B-H bonds), and two 3-center-2-electron bonds (bridging B-H-B bonds). Diborane readily reacts with $NH_3$, making the statement "X does not react with $NH_3$" incorrect. At low temperatures, $B_2H_6 + 2 NH_3 \rightarrow [H_2B(NH_3)_2]^+ [BH_4]^-$. At higher temperatures, $3 B_2H_6 + 6 NH_3 \xrightarrow{heat} 2 B_3N_3H_6 + 18 H_2$.