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Question: Assume the complex [Ni(PPh3)2 (SCN)2] is paramagnetic The analogous complex of Pd (II) is diamagneti...

Assume the complex [Ni(PPh3)2 (SCN)2] is paramagnetic The analogous complex of Pd (II) is diamagnetic The Isomerism shown by Pd (II) complex is/are

A

Linkage

B

Optical

C

Geometrical

D

Polymerization

Answer

Linkage, Geometrical

Explanation

Solution

The complex [Pd(PPh3)2 (SCN)2] is a 4-coordinate Pd(II) complex. Since it is diamagnetic, it adopts a square planar geometry, which is typical for Pd(II) (d8 ion). The complex is of the type [MA2B2], where M = Pd, A = PPh3, and B = SCN.

  1. Geometrical Isomerism: Square planar complexes of the type [MA2B2] can exist as cis and trans isomers. In cis-[Pd(PPh3)2 (SCN)2], the two PPh3 ligands are adjacent, and the two SCN ligands are adjacent. In trans-[Pd(PPh3)2 (SCN)2], the two PPh3 ligands are opposite, and the two SCN ligands are opposite. Therefore, the complex shows geometrical isomerism.

  2. Linkage Isomerism: The thiocyanate ligand (SCN-) is an ambidentate ligand, meaning it can coordinate to the metal center through either the sulfur atom (thiocyanato, -SCN) or the nitrogen atom (isothiocyanato, -NCS). Thus, the complex can exist as [Pd(PPh3)2 (SCN)2] (both S-bonded), [Pd(PPh3)2 (NCS)2] (both N-bonded), or [Pd(PPh3)2 (SCN)(NCS)] (one S-bonded, one N-bonded). These are linkage isomers. Therefore, the complex shows linkage isomerism.

  3. Optical Isomerism: Square planar complexes generally possess a plane of symmetry and are therefore not optically active. Simple [MA2B2] square planar complexes, including their cis and trans forms, are superimposable on their mirror images and do not show optical isomerism.

  4. Polymerization Isomerism: This type of isomerism involves complexes with the same empirical formula but different molecular formulas (different degrees of polymerization). The given complex is a simple mononuclear complex and does not exhibit polymerization isomerism.

Based on the analysis, the Pd(II) complex [Pd(PPh3)2 (SCN)2] exhibits both Linkage isomerism (due to the ambidentate SCN- ligand) and Geometrical isomerism (due to the square planar [MA2B2] structure).