Abstract
The P(IV)↔H spin–spin transfer across the N─H· · · O−−P+ intramolecular H-bond previously observed NMR spectroscopically for Z stereoisomers of hydrazones of O,O′ -diisopropyl 1-oxoalkanephosphonates, 2h J PH = 2.95 ± 0.35 Hz, was rationalized using Fermi-contact (FC) contributions to such J PH couplings. Moreover, the FC terms were found to be dominant terms of these 2h J PH couplings. The applied FPT-DFT(B3LYP) FC calculational approach was successfully tested on J PH couplings in model phosphorus esters. As a result, linear relation J PH obsd (CDCl3) vs. J FC PH calcd was established for different long-range J PH couplings occurring via an oxygen atom of the phosphoryl group.
Dedicated to Professor Marian Mikołajczyk from the CBMiM PAN in Łódź, Poland, on the occasion of his 70th birthday.
Notes
a Absolute values experimentally measured3,4 for both isomers in the E/Z mixture (excluding 1a)
b spin perturbation placed on the H-bonded proton4c
cspin perturbation placed on the P nucleus4c
d predicted using Gaussian 03 (all four Ramsey's terms considered)
e the FC term was found as identical with that FPT computed according to footnote b
f estimated with the scaling relationship given in ref.[20]
g not detected; h not computed.