Question

What characteristics do you expect from an electron deficient hydride with respect to its structure and chemical reaction?

Answer 1

It is expected to be a Lewis acid. For example, diborane `B_(2)H_(6) (dimer of BH_(3))` forms a complex with LiH which gives `H^(-)` ion (Lewis base)
`underset("Lithium hydride")(2LiH)+`underset("Diborane")(B_(2)H_(6)) to `underset("Lithium borohydride")(2Li^(+)[BH_(4)]^(-))`
Similarly, it also combines with trimethuylamine (organinc compound) and carbon monoxide which act as Lewis base to form addition compound.
`B_(2)H_(6)+underset("Trimethylamine")((CH_(3))_(3)) ddot(N) to underset("Addition compound")(2H_(3)B) leftarrow N(CH_(3))_(3)`
`B_(2)H_(6)+CO to underset("Addition compound")((2H_(3)B) leftarrow CO`