`NaBH_(4)` is ionic compound contain `BH_(4)^(-)` tetrahydridoborate ion and in solid state `NaBH_(4)` has sodium chloride structure. Not all tetrahydridoborates are ionic. The beryllium, aluminium and transition metal borohydrides become increasingly covalent and volatile. In these type of tetrabydrido borate the `BH_(4)^(-)` form covalent bond with metal ion. One or more H atoms in a `BH_(4)^(-)` act as a bridged bond to metal, forming a three centre bond with two electrons shared by three atoms. The `BH_(4)^(-)` is usually in that it may fonn one two or three such three centre bonds to the metal ion when fonns covalent bond.
`Be(BH_(4))_(2)` and `AI(BH_(4))_(3)` are covalent and structures are given below:

Options

A. Each tetrahydride borate form two hydrogen bridges
B. Two `BH_(4)` form 2 hydrogen bridges and one `BH_(4)` from one hydrogen bridge
C. One `BH_(4)` from 2 hydrogen bridge and two `BH_(4)` form one hydrogen bridge
D. B form only 2c - 2e bond

Answer

A