NMR spectroscopic technique can be applied on structure elucida tion,probeof molecular motion an d determinationof phsical proper ties.The first subjectof this re search is to evaluate electron d ensity dispersed onto the carbon yl’s antibonding pi-orbitalsin t ungsten pentacarbonyl complexes, W(CO)5L{L=PPh3,PPh2Me,PPhMe2,PMe 3}.Experimental results indicate that these phosphines are subst antiallyp-accepting ligands.The p-electrondensity on the rest ca rbonyl groups are affected by su bstituents’ s-basicityand p-acid ity in a competitive manner.Toge ther with earlier studies,it is found that substitution effects on 2p-population for axial and r adial carbonyls are well predict ed by number of metal’s d-orbita ls through which back-bonding pr oceeds.For p-neutral or p-donati ng ligands,,these effects are st rongly directional.The second pa rt of this research is to invest igate reorientational dynamics i nCCl3CN,which is characterized b y thespinning and tumbling diffu sion constant.These two motions can be solved by measuring the r eorientationalcorrelation times, tc,for both the CN and CCl vecto rs. Measurements of the values o f tc were accomplished bynitroge n-14 and chlorine-35 NMR quadrup olar relaxation time(T2q)experim ents.We have also utilized carbo n-13 chemical shift anisotropysp in-lattice relaxation times(T1CS A) todetermine tc(CN).Derived ma gnitudes ofspinning and tumbling diffusion constants reveal this molecule undergoes a significan tly anisotropicreorientation.Reo rientational diffusionconstants obtained from T1CSA(13C) andT2q( 14N)are in good consistence at v arious temperatures. Hence,this studyhas laid foundation for fut ure researchperformed on investi gation of bonding in M-CN comple xes.
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