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

Explanation

Electron-deficient hydribes have less number of electrons as required to form normal covalent bonds. To make up this deficiency, They exist in polymeric form, such as `B_(2)H_(6),B_(4)H_(10)` etc.Further to make up this deficiency, they react with many metals, non-metals and their compounds, hence they are highly reactive.
`2B_(2)H_(6)rarrNa[BH_(4)]+Na(B_(3)H_(8)]`
`B_(2)H_(6)+3Cl_(2)rarr 2 BCI_(3)+6HCI`
`B_(2)H_(6)+HCIrarr B_(2)H_(5)CL+H_(2)`
Since they are electron-deficient compounds, they act as Lewis acids and thus complexes with Lewis bases.
Lewis acid,Lewis base,Complex
`B_(2)H_(6)+2N Me_(3)rarr 2 [H_(3)B larr NMe_(3)]`
`B_(2)H_(6)+2Et_(2) S rarr 2 [H_(3)B larr SEt_(2)]`