Molecules stereochemically nonrigid

Reductive elimination of dihydrogen may then take place to complete the catalytic cycle  

In addition to converting secondary alcohols into ketones, the platinum caialyst also converts toluene and other benzyl hydrocarbons into dimers. 

Similarities between [Ru(bpy)j]2+ (discussed in Chapter 13) and [PMpopJJ4- are apparent. Reactive excited stales are produced in each when it is subjected to visible light. The excited state ruthenium cation, [Ru(bpy)3l I+, can catalytically convert water to hydrogen and oxygen. The excited slate platinum anion, [Pt,(pop).,l 4, can catalytically convert secondary alcohols to hydrogen and ketones. An important difference, however, is that the ruthenium excited state species results from the transfer of an electron from the metal to a bpy ligand, while in the platinum excited state species the two unpaired electrons are metal centered. As a consequence, platinum reactions can occur by inner sphere mechanisms (an axial coordination site is available), a mode of reaction not readily available to the 18-electron ruthenium complex.201 

204 Obviously a structure is not determined instantly with X-ray diffraction techniques. Rather the structure is instantaneous ia the sense that the time period over which the diffracted wave interacts with the electrons of the molecule is inliniicsimally short with respect to the frequency of atomic morions. 

204 This definition includes all stereochemically nonrigid molecules having identical energy minima und configurations at those minima including molecules such as the pscudoroialionut PFj and FetCOt, tChapler 61. 

If the barrier between the two configurations is thermally accessible, the system is fluxional. 

Like difiiaclion, spectroscopic methods using ultraviolel. visible, or infrared light are generally much faster than molecular vibrations or inlerconversions. and the 

Electron diliiactioo Neutron diffraction X-ray diffractian Ultraviolet VisHile 

Infhtred-Raman Electron spin resonance Nuclear magnetic resonance Quadrupole resonance MOssbauer (iron) q Molecular beam f. -. Slop41ow kinetics 

Academic New York, 1973 Chapter 10. Used with peimission.] 

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Table 2 Leading references for additional selected topics on stereochemically nonrigid molecules...

Reactions of Organometallic Complexes 686 Catalysis by Organometallic Compounds 705 Stereochemically Nonrigid Molecules 723 Conclusion 730... 

Support for a rearrangement mechanism involving a series of 1,2 rather than 1,3 shifts in such stereochemical nonrigid molecules has been found in... 

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