Ruthenium readily forms coordinate-complexes and these complexes have their applications in diverse fields. A survey of literature shows that designing of new ligands that can be complexed with Ruthenium (Ru) in various oxidation states can lead to development of new materials with diverse applications. In 21st century the gravity of approach of material science together with computer science has shifted from, how to make a molecule to what molecule to make, in other words molecular design. And now these are also quantized. As we know that physics, chemistry, and biology were explored at atomic levels and finally mathematical data were fed to grow required software for aimed simulations. The aim of present study is to study halides and mixed halides of Ru(II), which more precisely can help in the development of new Ru(II) complexes of desired application and or can help in fine tuning the property of pre-existing Ru(II) complexes. Thus, this study of atomistic details of halides of Ru(II) compounds along with construction of molecular orbital diagram at a glance will provide an insight of physicochemical, biochemical, electrochemical, thermochemical, magnetic, spectrochemical, catalytic, photoactive, and materialistic details. And this will help to solve the difficulties of synthesis of various complexes yet not synthesized. We know that all chemical reaction of complex compounds will be affected firstly by availability of vacant orbital(s) on metal ion (Ru2+) and secondly by the easiness of donation of electron pair(s) by ligands as we have also studied cloud-expanding effect, nephelauxetic effect, and electrochemical series of these Ruthenium(II) halides. The substitution reaction of complex compounds will also be mechanized and new substitution products (compounds) can also be prepared as topological analysis have also been made, those yet cannot synthesize by ordinary methods in required time and required cost too. Hence the halides of Ru(II) studied firstly. With the help of results of these studies, we will able to study complexation of these halides with selective ligands to form selective complex compounds of Ru(II) yet not prepared or have difficulties in preparation.

Halides amd mixedhalides of Ru(II), sd-hybridation, MO diagram, EHT, PM3