C-13, N-15, SI-29 AND P-31 NMR-STUDY OF N-TRIMETHYLSILYLAMINOPHOSPHORUS COMPOUNDS - SIGN DETERMINATION OF COUPLING-CONSTANTS AND APPLICATION OF HAHN-ECHO EXTENDED PULSE SEQUENCES

N-Trimethylsilylaminophosphorus compounds containing phosphorus in different oxidation states [P(III) and P(V)] and with different coordination numbers (2, 3 or 4) were studied by C-13, N-14, Si-29 and P-31 NMR, using a variety of one- and two-dimensional (2D) techniques, including Hahn-echo extended (HEED) pulse sequences. These techniques were demonstrated by the determination of the signs of all coupling constants involving the H-1, C-13, N-15, Si-29 and P-31 nuclei in bis(trimethylsilyl)aminodimethylphosphane (1). Appropriate experiments, including inverse 2D H-1{N-15} correlations, were performed for the other compounds in order to determine the signs of the coupling constants. A geometric dependence of 2J(P-31, N, Si-29) was proved for bis(trimethylsilyl)amino(tert-butyl)chlorophosphane (2c), where large negative 2J(P-31, Si-29) and a small positive 2J(P-31, Si-29) values, indicate syn and anti orientations, respectively, of the N-Si bond relative to the phosphorus lone pair of electrons. The HEED pulse sequences allow the rapid determination of isotope-induced shifts, (1)DELTA-N-15/14(P-31), as shown for 1, derivatives of 1 and 2c.