Microwave spectroscopy has been the most accurate and precise method for measuring structural parameters of free molecules. Pulsed-beam Fourier transform spectroscopy technique has been widely used to measure structures for both small and big complexes with greatly improved sensitivity and resolution. A Flygare-Balle type pulsed beam spectrometer was constructed at the University of Arizona in 1983 initially to measure structures of weakly bound complexes. Since then structures of many new transition metal organometallic complexes, weakly bound complexes and hydrogen bonded complexes have been determined. In this poster, we present very recent structural studies on transition metal hydrides; dihydrides, metallacycles and substituted ferrocenes. There has been a considerable interest in understanding the mechanism of hydride transfer reactions of the C5H5M(CO)3H; (M=Cr, Mo,W) type complexes. Here we present the gas phase structural data for Mo and W species. Secondly, we report gas phase structural results on dihydride species; (C5H5)2WH2. Recently there has been much interest and discussion on these types of complexes as researchers believe that these can be used as hydrogen storage devices. Next we present very recent gas phase results for a metallacycle, C2H4Os(CO)4. The olefin activated metal complexes of this type are very important because they have been extensively used in organic synthesis. Finally, microwave structural results for two ferrocene based organometallic complexes, (C5H5)Fe(C5H4R); R=CCH, CHO will be presented. These substituted ferrocenes find wide spread of applications in various fields of Chemistry.