Nuclear quadrupole resonance of amidinium tetrachlorophosphorates

Neutral Six-Coordinate Phosphorus

“…In the solid state, however, NQR evidence suggested that rapid cooling of Cl 4 P(NMe) 2 -CCl 3 led to the five-coordinate isomer which then reverted to the six-coordinate form (which according to other evidence seems to be the predominant isomer in the solid state) upon warming above 77 K. 60 A more general study showed the presence of both isomeric forms in the solid and that chlorotropism can occur in the solid state. 61 The IR data suggested that PCl 4 (NMe) 2 CCCl 3 is stable in the solid state without signs of chlorotropism but that the process occurs in solution, shifting to the predominance of the six-coordinate form as the polarity of the solvent increases. 62 A mechanism for the isomerism was proposed based on the migration of an axial chlorine atom to form a contact ion pair in the transition state and the phosphorus adopts first a square-pyramidal geometry which is then easily rearranged to the final trigonal-bipyramidal configuration (Figure 7).…”

“…Dynamic multinuclear ( 1 H, 13 C, and 31 P) NMR studies were used to follow the shift in equilibrium between the two isomers. Also the tetrachloroamidinate systems, PCl 4 (NMe) 2 CX (X ) CCl 3 ) 60 and (X ) Ph, CCl 3 , and CF 3 ) 61 were investigated with 35 Cl NQR spectroscopy. The 31 P NMR parameters for the six-coordinate species identified in this study are given in Table 3.…”

Interaction of Sulfur Dioxide with Aqueous Solutions of Amides

“…(11), (12), (19), and (20) reflecting the law of mass action and Eqs. (21)3 (23) reflecting the conditions of material balance and electroneutrality, we calculated the apparent association constants b I at 278 K (0.01 < Q SO 2 < 0.05 M): (23) where Q Am is the total Am content in the system.…”

“…To do this, we used a system of equations based on the law of mass action [Eqs. (11), (12), (19), (20), (24)] and the conditions of material balance [Eqs. (25), (26)] and electroneutrality [Eq.…”

“…(11)3(14) using the pseudo-gradient method (for details, see [18,19]). According to our results, the concentration dependence of pK 1 and pK* can be described by Eq.…”