Abstract: This thesis describes the synthesis and characterization of some transtion metal (Ru,Os, Mo) organometalics derived form nitrogen, phosphorous and oxygen containing ligands. The first chapter of thesis contains a brief introduction of synthesis, structure and application of cluster chemistry. The second chapter describes the reactivity of compound [Ru3(CO)12] with 2 – vinyl pyridine ligand. The reaction of [Ru3(CO)12] with 2–vinyl pyridine ligand in refluxing THF afforded the pentanuclear compound [Ru5(CO)14(µ -H)2(µ4-η6–NC5H4CH =C)]. In this reaction C – H activation at the vinyl carbon atom takes place with coordination of pyridyl nitrogen atom to a ruthenium atom. This Compound has been characterized by IR, 1H NMR and 31P {1H} NMR together with single crystal X–ray diffraction study. The third chapter describes the reactivity of [Ru3 (CO)10(µ-dppm)] with 2– vinyl pyridine in refluxing THF afforded. In this reaction the coordination of pyridyl nitrogen is accompanied by C– H activation of one vinyl proton. This Compound has been characterized by IR, 1H NMR and 31P {1H} NMR together with single crystal X–ray diffraction study. The fourth chapter describes the reaction of [Os3(CO)10(McCN)2] with dl– tryptophan in refluxing condition. However the ligand was not-reactive. [HOs3 (CO)10 (µ-OH)] was obtained probably from water present in the reaction mixture. This compound has been identified on the basis of IR, 1H NMR spectroscopic data. The fifth chapter describes the reaction of [Mo (CO)5(MeCN)] with tris – 2 – furyl phosphine which yielded [Mo(CO)5(C12H9O3P)] characterized by IR, 1H NMR, 31P{1H NMR} and Mass spectroscopic data.