Five-, Seven- and Eight-Coordinated Complexes

There is an inverse kinetic isotope effect, k /k-Q = 0.45 0.1 (for decomposition of PtH2(Mc3P)2) compared with PtD2(Me3P)2) in THF at 21 °C. This supports the previous prediction of nearly complete H-H formation in a late transition state. 

geometrical isomerization, phosphine ligand exchange and reductive elimination of H2 all proceed by independent kinetic processes.  

Werner-type complexes with these coordination numbers have been characterized. However a large majority of the complexes showing these coordination numbers are organometallic in nature and generally outside the scope of this book. Examples are shown in Structures 9-11, and discussion of the associated rearrangements will be necessarily brief. 

A large number of optically active square pyramidal organometallic complexes have been described. That shown in 9 is one of a pair of diastereoisomers that can be separated by fractional crystallization into (-I-) and ( —) rotating components. It is optically stable in 

The H nmr spectrum of Zr(Hf)(acac)4 in CHCIF2 shows two Me proton resonances of equal intensity in the slow exchange region only at lowered temperature ( —170°Ci). This observation is consistent with a square antiprism geometry 11. At — 145°C coalescence of the signals occurs arising from complicated intramolecular rearrangements. 

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