Question

In $LiAl{H_4}$ , the ligand is:
A. $H$
B. ${H^ + }$
C. ${H^ - }$
D. $2{H_2}$

Answer 1

Hint: Chemical formula of lithium aluminium hydride is $Li\left[ {Al{{(H)}_4}} \right]$ . Coordination sphere contains aluminium (central metal on) and hydride ion.

 Complete step by step answer:
In coordination compounds, those species present in the square bracket are collectively known as coordination sphere and outer species are known as ionization sphere or counter ion.

Ligands form coordinate bonds with the central atom or ion present in the coordination sphere. In the coordination compounds, electron donor species present in the coordination sphere and making coordinate bonds with the central atom or ion are known as ligands. In $Li\left[ {Al{{(H)}_4}} \right]$ , aluminium is a central metal ion and 4 ${H^ - }$ ions are ligands. These ${H^ - }$ ions form coordinate bonds with central metal ions ($A{l^{ + 3}}$) and $L{i^ + }$ ions are known as counter ions.

So, the correct answer is (C).

Additional Information: Coordination compounds are having coordinate bonds between central atoms or ions and ligands. Coordination spheres of coordination compounds retain their identity in the solutions. Ligands are classified on the many basis i.e. on the basis of denticity, on the basis of charge, on the basis donor sites, on the basis of ring formation etc. On the basis of charge ligands are classified into three categories as positive ligands, negative ligands and neutral ligands. On the basis of denticity ligands are classified as monodentate ligands, bidentate ligands, tridentate ligands, tetradentate ligands, ambidentate ligands etc.

Note:
In the coordination sphere two types of species are present i.e. electron donor species and electron acceptor species. Electron acceptor species are known as central atom or ion and electron donor species are known as ligands.