Nickel trans orientation

The thermodynamic stability of the 18-electron complex 64 (in the absence of added donors) may be the result of the unfavorable trans orientation across the nickel of the terminal carbon atoms. Addition of another ligand probably displaces the trans double bond and allows the complex to rearrange to the more favorable 69, which then leads to ttt-CDT. 

Compression molded (150°C for 3 minutes press chilled with cold water immediately thereafter) samples of poly(trans-l,4-hexadiene) (14) and poly(5-methyl-l,4-hexadiene) were examined with a General Electric (XRD-3) X-ray unit. Transmission Laue X-ray photographs were taken using nickel filtered copper X-radiation. Samples were stretched to four times of their original lengths to obtain oriented fibers. The fiber patterns were obtained in a flat plate film holder with the specimen to film distance standardized at 5 centimeters. X-ray diffraction patterns were similarly obtained for the hydrogenated sample of poly(5-methyl-l,4-hexadiene). 

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