Electron-deficient hydrides do not have sufficient number of electrons to form normal covalent bonds. Therefore , to mak up this defiency , they generally exist in polymeric forms such as `B_(2)H_(6)` , `B_(4)H_(10)`, `(AlH_(3))_(n)` etc.
further to make up this deficiency of electrons , they react with many metals, non-metals and their compounds. Hence, electron-deficient hydrides are very reactive as shown below :
`B_(2)H_(6)(g) + 3O_(2)(g) to B_(2)O_(3)(g) + 3H_(2)O(g)`
`NaH (s) + B_(2)H_(6)(g) overset("Diethyl ether")to underset("Sod. borohydride")(2Na^(+) [BH_(4)]^(-)(s)`
Being electron -deficient compounds, they act as Lewis acids, and thus from complexes with Lewis bases. For example.
`underset("Diborane")(B_(2)H_(6))+underset("Trimethylamine")(2NMe_(3)) to underset("Complex")(2H_(3)B larr NMe_(3))`
`B_(2)H_(6) + underset("Carbon monoxide")(2:CO) to underset("Complex")(2H_(3)B larr CO)`
