31P‐NMR‐Untersuchung und Alkylierung von N‐Hetaryl‐triphenylphosphanimiden: Ableitung von σ−‐Konstanten verschiedener N‐Ringsysteme aus den 31P‐chemischen Verschiebungen

Abstract

31P‐N.M.R. Investigation and Alkylation of N‐Hetaryl‐triphenylphosphanimides: Estimation of σ−‐Constants for Several N‐Ring Systems from the 31P Chemical ShiftsOn the basis of a Hammett‐lide relationship we have used the 31P chemical shifts of N‐hetaryl‐triphenylphosphanimides 2 to estimate σ−‐constants resp. σ−‐differences of several N‐heteroaromatic rings. The electron‐withdrawing influence of these rings on the P chemical shift is additionally increased by a short‐range electrical field and magnetic anisotropy effect respectively in case the phosphazene group is linked with the α‐position of the hetarene. If one aza substituent is neighbouring to the detector group, this through space effect leads to a downfield shift of about 7 ppm. All compounds are alkylated with methyliocide at the ring N atoms and give the quaternary salts 3. The pyridine‐N‐oxide derivative 2n exists in the open‐chain form and reacts with methyliodide at the O atom.