Transition metals ellipticity

Transition Metals. - Carbene complexes of the chromium triad have proven to be attractive reagents in modern organic chemistry. Since the advent of the catalyst RuCl2(CHCH=CPh2)(PR3)2 much interest has been dedicated to the synthesis of the alkenylcarbenes of the Pe triad. Bemad et are the first to describe the aUcenylaminocarbenes of Ru. The ellipticities of the Ru-Ca and C -N bonds are reported to be low. 

As mentioned in Chap. 9 (p. 215) the cyclic decapeptide antamanide exists in several conformations depending on the presence or absence of alkali metal ions and on the polarity of the solvents. The transition of the free form to a complexed one can be easily followed by CD spectra (Fig. 7). On the addition of Na ions or water the large negative ellipticity (Cotton effect) observed in apolar solvents, such as dioxane, disappears and changes into a positive Cotton effect in the same wave length region. 

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