Physical image vs. structure relation, 5.: Multinuclear NMR structural study on some hydrazones of O,O-dialkyl 1-oxoalkanephosphonates

An unambiguous method for determination of the configuration of any single O,O-dialkyl 1-oxoalkanephosphonate hydrazones based on H-1, C-13, P-31 NMR data has been elaborated; the use of (1)J(CP) (P-C=N) couplings is the most fruitful. The C-12/C-13 isotope effects on the 31P chemical shifts of selected compounds have been measured. For primary hydrazones the E/Z isomerisation with stabilisation of their Z forms through an intramolecular R-bonding has been proven. In addition, for the latter stereoisomers small scalar couplings between II-blinded groups N-H...O=P have been found, J(HP) 2.4-3.4 Hz. The possibility of the across IT-bridge transfer of spin-spin interactions in these forms is also discussed.