Chlorine resonance frequencies are reported for the following at 298°, 194°, and 77°K: CsICb, KICb, KICb·H20, CsICI" RbICI" KICl" KICI,·H20, NaICI,·2H20. Variations due to crystal effects in these substances amount in most cases to less than a megacycle. The average frequencies at room temperature, 19.2 and 22.3 Me/sec, are taken as representative of ICb-and ICI,-ions, respectively, in a crystalline environment. These values are in the neighborhood of half those found for ICI, and suggest a bonding scheme in which the electron distribution is shifted outward toward the chlorine atoms to such an extent that the electron population of iodine orbitals is not so large as to require the use of d orbitals. The conclusion is that d orbitals are rather less important to bonding in the polyhalides than has generally been supposed. The problem of arriving at a practical and meaningful separation of crystal and chemical effects is considered qualitatively, and marked crystal effects evident in the spectra of KICI,· H20 and NaICI,· 2H20 are briefly discussed. *

No abstract

Frequencies are reported for m=±12↔±32 transitions of I127 nuclei in polycrystalline samples at 25°C of CsICl2, RbICl2, KICl2, KICl2·H2O, CsICl4, RbICl4, KICl4, KICl4·H2O, NaICl4·2H2O. The coaxial cavity super-regenerative oscillator (250–610 Mc/sec) used for these measurements is described. The average quadrupole coupling constants are —3110 Mc/sec for ICl2— and +3090 Mc/sec for ICl4—. These values are shown to be entirely consistent with resonance hybrid structures which had been selected previously for the discussion of the chlorine resonance data. The coupling constants are used to estimate electron populations for valence orbitals of I and Cl, and, with certain assumptions, to find approximate MO's of LCAO form for the bonding electrons. The conclusion reached is that the attainment by iodine of higher valences in these ions is due more to transfer of charge to chlorine atoms than to promotion to higher orbitals of iodine. It appears that most of the covalent binding present arises from an MO in which an iodine p orbital is associated with a symmetry orbital made up of collinear sp hybrid orbitals of two attached chlorine atoms.