THE ¹⁹F N.M.R. SPECTRUM OF IF₇

Abstract

I t is shown that the line shape calculated for the n.m.r. spectrum of a magnetic nucleus attached to a nucleus of spin 5/2 undergoing quadrupole relaxation agrees well with the observed spectrum of iodine heptafluoride. The iodine-fluorine coupling constant was found to be J I F = 2 100 C/S. The apparent magnetic equivalence of the fluorine atoms in IF7 is discussed.The I T nuclear magnetic resonance (n.m.r.) spectrum of IF7 a t room temperature is an extrenlely broad doublet (Fig. 1A). Our spectrum agrees closely with that reported previously (1-4). Muetterties and Packer (3) have suggested that the observed spectrum is a partially collapsed sextet arising from the coupling of seven spectroscopically equivalent fluorines to the iodine which is undergoing quadrupole relaxation. They did not, ho~vever, calculate the expected spectrum. Recently, Suzuki and Kubo (5) have given a general method for calculating multiplet line contours for the resonance of nuclei coupled to a high-spin nucleus which is undergoing quadrupole relaxation. Previous calculations of line shapes for nuclei coupled to nuclei having I = 1 (6, 7) and I = 3/2 (8) may be considered as limited applications of this illore general theory. I t has been pointed out that the theory involves some approximations (5, 6) but the agreement between calculated and experimental line shapes for I = 3/2 (8) indicates that the approximations do not lead t o any serious error. Suzuki and Kubo calculate spectral shapes as a function of a parameter a = (e2;~)2 --9 where e = the charge on an electron, eq = the electric field gradient a t the nucleus, eQ = the quadrupole moment of the nucleus, T , = the correlation time for molecular 'Present address:

The solid-state 19F NMR spectrum of [N(CH3)4][IO2F2], a vibrational study of [N(CH3)4][IO3] and [N(CH3)4][IO3]·2H2O, and the X-ray crystal structures of [N(CH3)4][IO2F2] and [N(CH3)4][IO3]

“…At the current field strength (11.744 T), n( 127 I) = 99.914 MHz, and R = 0.02 corresponds to a quadrupolar coupling constant, x = 5000 MHz, which is of the same order of magnitude as that obtained for the IO 3 À anion (1000 MHz) [34]. The value of 1000 Hz for j 1 J( 127 I-19 F)j is in the expected range when compared with the known and calculated j 1 J( 127 I-19 F)j values for iodine(V) and (VII) fluorides: IF 6 + (2744 Hz) [27], IF 7 (2100 Hz) [28], IF 4 + (F eq : 1572 Hz, F ax : 653 Hz) [37]. The sensitivity to the sign of 1 J( 127 I-19 F) that is observed in these spectral simulations is in accord with the theoretical prediction that the sign of 1 J( 127 I-19 F) for iodine fluorides with iodine in the +5 and +7 oxidation states is negative [37].…”

“…A 1 J( 127 I-19 F) coupling constant of approximately 2100 Hz has been estimated from the 19 F NMR spectrum of IF 7 [28], which is comprised of a broad, saddle-shaped, partially quadrupolecollapsed resonance.…”

“…500 Hz. Because of experimental and theoretical evidence [27,28,37] to the contrary, a 1 J( 127 I-19 F) value of 100 Hz was considered to be unrealistically low and the simulated doublet pattern is not further considered in this discussion; (c) negative values for J when R = AE0.02 and AE0.01 produced doublet patterns for J < 1500 Hz. Using negative J-values and R = AE0.02, doublet patterns were obtained that were skewed in opposite directions with respect to one another (Fig.…”

The Molecular Structures of the Polysulfuryl Fluorides by Vapor Phase Electron Diffraction: S2O5F2 and S3O8F2

“…Gillespie and Robinson (3,4) predicted values for the S-0 bond lengths (1.40 A, terminal and 1.66 A ,bridge) and LO=S=O (120-122') from correlations of these parameters with force constants and vibrational frequencies.…”

N.M.R. spectra of molecules containing quadrupolar nuclei

“…Both high resolution [13][14][15][16][17] and spin-echo [18,19] techniques have been used to study systems containing a quadrupolar nucleus with a small quadrupole moment in cases where relaxation rates are intermediate between the above two extremes. It was the object of this work both to investigate the coupling constants and nitrogen relaxation times in some fluorinated pyridines (A = 14N, X-19F), and to test the validity of an extension to multi-spin systems [20,21--see the succeeding paper] of the equation derived by Pople [9] (describing the shape of the resonance of one spin-89 nucleus coupled to a nucleus relaxed via the quadrupolar mechanism).…”