¹H and ¹³C NMR study of α‐acetylenic P^III and P^IV derivatives. Signs and magnitudes of <i>J</i>(PC) and <i>J</i>(PH)

Abstract

Abstract All J (PH) and J (PC) values, including signs, have been obtained in acetylenic and propynylic phosphorus derivatives, R 2 P(X)CCH and R 2 P(X)CCCH 3 (X  oxygen, lone pair and R  C 6 H 5 , N(CH 3 ) 2 , OC 2 H 5 , N(C 6 H 5 ) 2 , Cl) from 1 H and 13 C NMR spectra. In P IV derivatives the following signs are obtained: 1 J (PC)+, 2 J (PC)+, 3 J (PC)+, 3 J (PH)+, 4 J (PH). Linear relations are observed between 1 J (PC), 2 J (PC) and 3 J (PC) versus 3 J (PH), indicating that these coupling constants are mainly dependent on the Fermi contact term, though the other terms of the Ramsey theory do not seem to be negligible for 1 J (PC) and 2 J (PC). In P III derivatives these signs are: 1 J (PC)‐ and +, 2 J (PC)+, 3 J (PC)‐, 3 J (PH)‐, 4 J (PH)+. Only 3 J (PC) and 3 J (PH) reflect a small contribution of the Fermi contact term while in 1 J (PC) and 2 J (PC) this contribution seems to be negligible relative to the orbital and/or spin dipolar coupling mechanisms.