Bond stretch isomerization

Bond-Stretch Isomerism and the Reactivity of some Highly Strained Tricyclic Hydrocarbons towards Acids and Bases... 

Figure 5.5 Bond-stretch isomerism for tetrametallabicyclo[l. 1.0]butanes (E = Si, Ge).

Gibson, V. C. and McPartlin, M., Bond Stretch Isomerism Fact or Artefact , J. Chem. Soc., Dalton Trans., 1992,947-956. 

Bond-stretch isomerism was found in plumbaprismane, 33, M = Pb, which collapses to a six-membered monocycle, and in plumbacubane 34, M = Pb, where two bonds are stretched to form two six-membered rings as shown in 43195. Activation energies for all the isomerizations described above are not available. 

It has been pointed out that the well-known and genuine phenomenon of spin-state isomerism, where molecules of the same composition and general structure will often show significant metrical differences in different spin states, should not be confused with the alleged bond-stretch isomerism.16... 

An example of one of the problems that can result when interpreting X-ray diffraction results comes from bond-stretch isomerism." The complex mer-MoCl2(PMe2Ph)3 was observed to exist as blue... 

Gibson s chapter also includes a brief historical commentary on the distortional or bond-stretch isomerism debate concerning green and blue forms of [Mo(0)Cl2 PMe2Ph)2] initiated by Chatt, Manojlovic-Muir and Muir in 1971. 

This account would not be complete without mention of distortional isomerism, a term Joe Chatt was to coin in describing two isomeric forms of the six-coordinate compounds, [Mo(0)Cl2(PMe2Ph)3] (35, Figure 12) in a short communication published in Chem. Commun. in 1971, but which later was to spark an intense debate into the reality or otherwise of the phenomenon of bond stretch isomerism. We followed the debate with some interest, since we had inadvertently stumbled across seven-coordinate oxo and sulfido compounds of niobium of the type [Nb(E)Cl3(PMe3)3] (E = O or S 36) which seemed to show a closely related effect. 

Figure 12 Six-coordinate molybdenum and seven-coordinate niobium complexes which appeared to display the phenomenon of bond-stretch isomerism...

A REINVESTIGATION OF BOND-STRETCH ISOMERISM IN c/s-iner-MoOCl2(PMe2Ph)3... 

The interpretation of x-ray diffraction data in providing experimental evidence for bond-stretch isomerism in cis-mer-Mo(0)Cl2(PMe2Ph)3 provides an extreme illustration... 

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