M.Sc.

Taking in account the basic ideas in coordination chemistry governing the structure and reactivity of these compounds especially those of Palladium and Platinum complexes, a new set of Pd(II) and Pt(II) square planar complexes with varying structural isomerism have been prepared and studied. Their structure and spectral behavior have been discussed based on hard and soft acid base principles, back π-bonding, and redox behavior.

The work in this thesis involves four parts:

Part one: Synthesis of 2,5-disubstituted-1,3,4-thiadiazoles:

For the synthesis of the titled compounds the following sequence of steps (step -1- to step -8- ) were followed.

Step-1- : Synthesis of 2,5-dimercapto-1,3,4-thiadiazole [1].

It was prepared by cyclization of hydrazine hydrate with carbon disulfide in alkaline medium.

The scheme of this work involves synthesis of different five and six membered heterocyclic rings starting from 4-nitrophenyl hydrazine and two different acid hydrazides (benzoic hydrazide and            p-chlorobenzoic hydrazide) which were synthesized from their carboxylic acids.This work is divided into four different parts:

First part: