Tricoordinate substituents, electrical effects

Based on the results set forth in Table 17, all of the tricoordinate substituents of Group 15 elements seem to have an overall electrical effect which is determined by the nature of... 

Also examined were the chemical shifts of substituted nickel carbonyls, X—Ni(CO)3 . The ligands, X, had the form MZ3 where M is a group 15 element, usually phosphorus. It can be seen on inspection of the equations we have used to estimate electrical-effect parameters for Group 15 tricoordinate substituents that we can use these parameters as a measure of the electrical effect of the X groups in this data set. The best regression equation obtained is ... 

Electrical and Steric Effects of Substituents Bonded to Phosphorus Tricoordinate Phosphorus... 

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