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D A I Y U ?;AKAB.IURS AND I I A S A J I
KUBO
Pure Quadrupole Resonance of Halogens in Some R,[MX,] Type Complexes
by Daiyu Nakaniura and Masaji Kubo Department of Chemistry, Nagoya Uniaersity, Chikusa, 'Vagoya, Japan
(Receiced M a y 18, 1964)
The pure quadrupole resonance of halogens in soine hexahaloplatinates(1V) was observed a t various temperatures. The hexachloroplatiiiates(1V) and hexabroinoplatinates(1V) show a single resonaiice line in agreement with the Kz [PtC&]structure of these complexes. Aiiiinonium hexaiodoplatinate(1V) shows a single resonance line at room and Dry Ice temperatures, but two lines a t liquid nitrogen temperature, indicating that the syinnietry of the crystal is lower than cubic symmetry. Rubidium hexaiodotellurate(1V) shows three transition points a t about -40, -16, and 5 5 O , above which the crystal has cubic syininetry. The resonance frequency of halogens in K ~ [ P t C l type ~ ] crystals increases progressively while the absolute value of the temperature coefficients of resonance frequencies decreases with increasing size of cations and decreasing temperature. Ainiiionium hexachloroplatinate(1V) and hexabroiiioplatinate(1V) are exceptions to this rule, a rotational transition being found to exist a t 0-lo for the latter compound.
Introduction Wc have observed the pure quadrupole resonance of halogens in various hexahalo complexes of the general type Rz [1ux6] having different central nietal atoms M,lW6 The main object of the study was the quantitative estimation of the covalent character of nietalligand bonds in these coiiiplexes from the quadrupole resonance frequencies a t liquid nitrogen temperature. Owing to the high accuracy obtainable in radiowave spectroscopy, it is possible to determine the possible effect of temperature and neighboring cations on the electronic structure of complex anions. I:roin the observed tcinperature dependence of the resonance frequencies, one can discover phase transitions in crystals which are less readily accessible by inore laborious inethods such as X-ray crystallography and heat capacity measurements. We have therefore prepared a number of hexahaloplatinates(1V) differing in the kind of cations and rubidiuiii hexaiodotellurate(1V) and deteriiiined the pure quadrupole resonance frequencies a t teiiiperatures between room and liquid nitrogen temperatures.
Experimental Appamtus. A Dean type self-quenching superregenerative spectroineter already describcd was used for the observation of quadrupole signals of chlorine iqotopes. For detecting the resonance frequencies The Journal of Ph.ysico.1 Chemistry
of bromine and iodine, a self-quenching super-regenerative spectroineter equipped with Lecher lines was employed. Resonance frequencies were determined at room, Dry Ice, and liquid nitrogen temperatures. Whenever the existence of transition points mas suspected from data a t these temperatures, ineasurenients were also made between -70 and 70' a t temperature intervals of several degrees or less. Materials. All the complexes studied were synthesized in accordance to methods described in the literature. Ainiiioniuni hexachloroplatinate(1V) was prepared by adding aniinoniuin chloride to a solution of hexachloroplatinic(1V) acid in hydrochloric acid.' The resulting yellow powder crystals were washed several times with dilute hydrochloric acid. Hexabroinoplatinic(1V) acid enneahydrate was obtained by the dissolution of platinum black in an aqueous solution of broinine and hydrobromic acid followed by the (1) D. Nakamura, Y. Kurita, K. I t o , a n d - M . Kubo, J . Am. Chem. Soc., 82, 5783 (1960). (2) K . Ito, D. Nakamura, Y . Kurita, K . Ito, and M. Kubo, ibid.,83,
4526 (1961). (3) D. Naknmura, K . I t o , and M .Kubo, ibid.,84, I63 (1962). (4) D. Naknmura, K. Ito, and M.Kubo, Inorg. Chem., 1, 592 (1962). ( 5 ) D. Snkamurii, K. I t a . and & Kubo, 'I, ihid., 2 , 61 (1963). (6) K . I t o , D. Nakamurn. K. I t o , and M .Kubo, ibid., 2 , 690 (1963). (7) G . Brnuer, '' Hnndbuch der prapnrntiven nnorgnnischen Chemie," Ferdinand Enke Verlag, Stuttgnrt, 1954, p. 1174.
I’URE
QUADRUPOLE RESONASCE O F H.4LOGENs
I N SOME
removal of exces8 bromine and hydrogen I n order to prepare sodiuiii hexabroiiioplatinate(IY) hexahydrate, sodium bromide was added to a solution of hexabronioplatiiiic(1V) acid in dilute hydrobromic acid.8 Orange-yellow crystals were separated and washed several times with dilute hydrobromic acid. Aiiinioniuiii hexaiodoplatinate(1V) was prepared by adding hexachloroplatinic(1V) acid to a concentrated solution of excess aiiinioniuin iodide. Black powder crystals formed were washed twice with cold water. Complexes differing from the foregoing ones in the kind of cations were synthesized in a similar manner. Ru bidiuiii hexaiodotellurate(1V) was formed when rubidium iodide was added to a solution of tellurium dioxide in hydriodic acids3 The resulting black crystals were washed with hydriodic acid solution and dried. Since no data for this compound were available in the literature, chemical analysis was performed for the identification of the complex. A n a l . Calcd. for RbeTeIG:Te, 12.0; I, 71.8. Found: Te, 12.1; I, 71.1.
Rz [~\$XG] COMPLEXES
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Table I : Pure Quadrupole Resonmce Frequencies of Halogens in Some R P [ M X ~Complexes ]
Compound
(NHa)sPtCle
RbnPtCle
CsnPtCls HPPtBrs.9Hz0 NazPtBr6.6Hz0
(”4)2PtBr6
RbzPtBr6
Results The resonance frequencies of 35Cl,79Br, and lZ7I CszPtBrd observed at room, Dry Ice, and liquid nitrogen temperatures are listed in Table I. Those of less abundant (SH4)zPtIe isotopes are omitted, because they give correct isotope frequency ratios, ~ ( ~ ~ C l ) / v ( ~=~ C1.269 l ) and V ( ~ ~ B ~ ) / v(81Br)= 1.197.
Discussion Number of Resonance Lines and the Crystal Structure. All hexachloroplatinates(1V) and hexabronioplatinates(IV) studied show a, single resonance line. This is in agreeiiient with the iresults of X-ray crystal analysis on aniiiioniuni, rubidium, and cesium hexachloroplatinates(1V) and hexabronioplatinates(IV), which are reported’” to forin I
