Question

Due to the presence of ambidentate ligands coordination compounds show isomerism. Palladium complexes of the type $[Pd{({C_6}{H_5})_2}{(N{O_2})_2}]$ and $[Pd{({C_6}{H_5})_2}{(ONO)_2}]$ are?
A. Linkage isomers
B. Coordination isomers
C. Ionization isomers
D. Geometrical isomers

Answer 1

Hint: Ligands are the ions or atoms or molecules present inside or outside a coordination complex which binds to the central metal atom. Ligands are of various types like unidentate, bidentate, tridentate etc. Ambidentate ligand \[SC{N^ - }\] ion has two donor atoms \[N\] and \[S\] . It links to metal as either\[M - SCN\] or \[M - NCS\].

Complete step by step answer:
i. A ligand is an ion or molecule that donates a pair of electrons to a central metal atom or ion to form a coordinate metal. Ambidentate ligand is a type of ligand that has the ability to bind a central atom through atoms of two different elements.
ii. Coordination compounds are chemical compounds consisting of an array of ions or neutral molecules that bind to a central atom via covalent bonds. Coordination compounds are also known as coordination complexes. These molecules or ions that bind to the central atom are known as ligands (also known as complexing agents).
iii. Palladium and nickel complexes catalyze the reaction of organometallic reagents (\[R - M\]) with aryl or alkenyl halides and related compounds (\[{R^1} - X\] ) to give cross-coupling products \[R - {R^1}\]
iv. Ligand (s) which have two different affinity sites, known as ambush ligands, e.g. \[NCS\],\[N{O_2}\]etc. Here $NCS$ has two binding sites in \[N\] and \[S\]. Therefore, $NCS$ (thiocyanate) can bind a metal ion in two ways. Thus, coordination compounds containing $NCS$ as ligands may show linkage isomerism and are linkage isomers.

So, the correct answer is Option A.

Note: The ligands which are present inside the coordination complex satisfy the secondary valency or the coordination number of the central atom. The ligands or ions which are present outside the coordination complex satisfy the primary valency or the oxidation state of the metal ion.