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In recent years there is an increasing awareness of the importance of chiral phosphorus ligands in transition metal organometallic chemistry because of the utility of such complexes in homogeneous catalytic reactions. This thesis deals with synthetic, spectroscopic and X-ray crystallographic studies on ruthenium complexes of chiral and achiral P-N-P type ligands, known as "diphosphazanes", with emphasis on ruthenium carbonyl clusters. Several ruthenium carbonyl clusters have been synthesized and characterized by elemental analyses, ER and NMR (lH, nC and 3lP) spectroscopic data. In several instances, the molecular structures of the clusters have been confirmed by single crystal X-ray diffraction studies. Chapter 1 provides a brief overview of various types of chiral phosphorus ligands and general synthetic routes to diphosphazanes. A brief review of the transition metal chemistry of diphosphazanes and diphosphazane chalcogenides (published since 1994) is presented A review of the literature on the carbonyl clusters of the group-8 transition metals (Fe, Ru, Os) bearing mono- and diphosphines is also included in this chapter The scope and aim of the present investigation is outlined at the end of this chapter. Chapter 2 provides the results obtained in the present investigation and a detailed discussion of the spectroscopic and crystallographic data. The essential feature of the work is summarized at the end of the chapter. Chapter 3 gives a detailed account of the experimental procedure for the synthesis of the compounds and spectroscopic and analytical measurements. The experimental details of X-ray structure determination are also given in this chapter. To save space, the coordinates of the H-atoms and the calculated and observed structure factor tables are not included. In some cases, reference to CCDC deposition number is included. The references of the literature are compiled at the end of the thesis and are indicated in the text by appropriate numbers appearing as superscripts. The compounds synthesized in the present study are represented by bold Arabic numerals and are listed in Appendix I. The abbreviations employed in the thesis conform to those generally used in Chemical Abstracts.