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Far-IR spectra of InI, InI2, and InI3
1. PLya Chm. &Us.
197!3.Vol. 40. pp. 2492%.
Papmm f’mr.
in Grot
PAed
Btitaim.
TECHNICAL NOTE FAR-IR SPECTRA OF InI, It& AND InIs K. kHIKAWA and s. IKAWA Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan (Received 21 February 1978;accepkd in revisedform 13June 1978)
Thermal analysis of the indium-iodme system[l, 21 shows the presence of 3 distinct compounds InI, InIs and It& with congntent melting points. Investigations on the crystal structure inch& X-ray d&action of InI[3,4] and InIs[S,6], and Raman and IR spectra of InI,[7-IO]. For solid In1 no attempt was made at assigning the Raman-active bands[ll]. Raman studii of It&[1 I, 121 suggested that the indium diide contained Inbanions. It follows that solid InIs might be most simply formulated as In’[InmI,]. The primary interest in the InIs compound was prompted by the hope of detecting unquivocai evidence of at least two distinct valence states, In’ and In’+ from IR studies. In order to elucidate this fascinating property this paper describes the results of far-IR investigations on three distinct compounds InI, InIs and InI,. Guaranteed reagent-grade InI, puritied by tripie vacuum distillation at 220-23tYCwas crystalline. The indium monoiodide was prepared from the In13, pm&d as above, and a stoichiometric excess of indium metal (99.99% pure). The product was puritied by vacuum distillation at 370_3800C[13], the vapor condensing on a cooler surface as brownish-red crystalline plates. InIs was prepared by reacting stoichiometric amounts of the purified InI and InI compounds at 229-m in uacuo. Tbe composition was checked .by chelatometric (In) and argentometric (I) analysis, with the result 33.0 at.% In. The X-ray powder technique confirmed that the InIs solid included no solid phase of InI[14]. In&urn monoiodide. Figure l(a) and Table 1 show the IR spectrum of ctystahine InI at room temperature. The observed band consists of a singk absorption line at 70cm-‘, associated with a weak shoulder at the hi-frequency side. This result is in strong contrast with previous Raman studIes[l2] which showed 5 Raman bands without assignment. Crystals of In1 have the Cmcm-Dz space group with an elongated 4 mokcule cell[3,4]. Factor group analysis[l5] provides the 3 IR-active modes of B,. +, Bzut. and B3. types for a crystal of InI. The 3 modes
T Fii.
1. Far-IR spectra for InI, InIs and InI,.
Table 1. Vibrational frequencies (in cm-‘) and stretching force constants (K in mdyne/A) of InI, InIs and InI
this work
WI
this work
IR
Raman
IR
70t
211 135 105 78 39
170 126 70 54 45 37
K=0.09
InL (SOhI)
In&
In1
WI
Raman 191 177 138 72 62 47
1141
fII1
191 185 138 74 58 47
InI this work
]71
181
191
223 174 150 122
226 179 157 125 60 49
228 178 158 125 59 49
214 173 153 123 57 48
Raman 185 139 58. 42
K = 0.82
v3V2)
v&41) v#,) ~03
dS,.) vl6@3.) Vl3uL) vd~3.) hdB3.) vI4@2.)
K = 1.42,0.64;[8]
tAssigned to v(In’-I-) in this work. 249
250
TechnioaINotes
approximatelycorrespond to In”-I- stretchingvibrations. along the aa, bs and ca axes respectivelyof the crystal. The umesoIvod band obtained here shows that the frequencies of the 3 mod@ are &se to each other. At this point it can be proposedthat itti is rouphlycharacterizedas a simpleionic crystal,e.g. N&i. Thus the ‘ZtIcm-’band is definitely assigned to the In’-I- stretching Z~diumdii~di~. The KR spectrum of I&, with vibratiounl assinnments. is shown in Pin. Ifbk and Table 1. The absorution Ii&, except for the peati-at 7&m-‘, readiIy correiate‘witb $ soiu~[I6], and the Raman spectra of inb- ions in in the sah (u-~r~;~~lni‘-rI~, as pointed oat in the pmv* ious Raman investigatiotts of solid ir&{f I, 121.it shouid be noted that two i&inactive bands ~,(A~~~~~(~},were cleat@ observed, and the band v&E) splits into two bands at 37 and &cm-‘, respectively. it is clear, therefore, that the compkx anion it&- has a symmetry tower than the point group Td.The band at 70cm-’ was assigned to the Iattiee viiratiou of the In” ion from its simiiarityto the 70cm-t band for the ini crystak it seems reasonableto supposethat the In” ion in crystaikte inIt is surrounded by some units of the anion Ini,- and acted on by a ~~~t~ 8eld similarto that k ini, whichis almosta simpk ionic crystal. In this case the Iattice &ration of the In” ion has a frequency in the same region as the in’ -I- stretchingvibration in ini. This assignment for the ?gcm-’ band in Inis is also supported by Raman studiesfI4]. ‘iite Couiomb ~~ b tween in’ and it&^ directly gives rise to a deviation from Tb point symmetry in the it&~ ion. Thtrs the tbtcidation of the distinct band at 70cm-’ is the minimum necessary to characa terke a mixed-valen~ state consist of in* and in-” and the I&~ ion, with the site symm~ less than Td is solid In&. Since both in” and in’+ exist as separate entities In inia at room temperature, this intermediate compound can be called “inho~~usiy ~~~v~n~‘~ it is worth whik noting thn&the depondenee of tbe “‘in relaxation rates on frequency C vesti8atedfor molten it& is reminiscentof local vaknce Iiucttm tions between the two distinct valence states in’ and In”+[i8]. Zodiac #atone. X-Ray wafyses showed that c~s~~ne I& is built of in& mokeutes with Z& symmetryand has the space group CzA.The infrared spectrumdue to the present work whicit is summarizedin Fig I(c) and Table I, agrees with previous iR studies{7-9fin wbicb the amdysesof the ~~rn~~ bands were satisfactoryperformed. The stretchingforce constant, K, of the in-l bond in the It&ion wns caktdated on the basis of the U~~R~ky force fieid[i9J,using the observedfrequenciesof It&, and the K value for ini was c&ulated rou8hiyusing a formuia for the optically active tat&e vibratiott of the NaCl-tvue s~~~~281. _ The Mues of K fmdyaes per & me listed kTahk 1 together witb those for ini,[g]. The increase in R in passingfrom ini to in& is much more abrupt compared with that in passhtg from init to inij. The magnitude of K ako suggests that the crystat fnl is c~cte~stic of a simpie ionic erystsl, e.g. NaCl, whose K vehtes have a magnitudeof 8.I n&A, e.g.[XI].Badger’sruie[Zl] may be used to cakukta the eq~~urn interuttcleardistance of
in-i in Ini,- for the wornout Inir from vibrational data alone. The bond force constants used in this tstk were substituted by each stretching force constant K for in1. ini? and I&. The distance was &imated as 2.74A 2 0.05 which & eompa&e to the distances 2.64and 2.84&5] of the terminal and bridgedin-i bond in the dimer in&. These separations must be assigned a covalent in-i bond because PauIing[22]gives 2.72A as the sum of the tetrahedral covalent radii of in and I. it is worth whiIe noti that the nearest and second-nearest distances 3.23 and 3.46? of In-i bonds in InIP] become more like the sum of the imivaknt ionic radii of in’ and i-, 3.48A[22]. Ac&~wkdg~ents-We wish to express thanks to Prof. M. Kimura for encant during the course of this work. One of us (K. i.) is also gratefulto him for hostility. 1. Thiel A. and Kaetschii., Z. QASMF. _ TV&em. _ Ckerra.66,288 (iSlO). 2. Peretti E. A., J, Am. Ckem. Sot. Z&5745(1956). 3. Jones R. E. and Temuk~n D. H.. AC& Crvst. 8.847 (19551. 4. WychoffR. W.G., ~~st~st~~~a~s, Vol,2.int~~~ie~~e,New York(1963). 5. Forester J. D., Zaikin A. and TempletonD. ii., Zuorg.C&r. 3,63 (I964). 7, BeattieI. R., Giison T. and Ozin G. A., J. Ckem. Sot. (At, 813 WM. 8. Adams D. M. and Ch~ch~l R. G,, .Z,CZteur,Sot. (A). 2141 (1968);and Z. Ckem. Sot. (A),697(197tB. 9. Greenwood M. N., Prince D. J. and Stranghan B. P., J.
Ckem. Sac, [A), I634 ft%Q. 10. Bncs V. W., Aithras 2. and Okon G., Z. &roe. Affgem, Ckem. 428,193(1976).
Ii. Davies J. B., Waterwo~ L. G. and Worrah I. J., f. hag. Nwi. Ckem. 36, IMM ( 1!474). 12.Con&erasJ. G., Poland 1. S. and Tuck D. G., I. Ckem. SM. @?&onf, 922(1973). 13. Rolsten R. F,, Zodfde &i&is and Mefuf Zedides. Wiley, New York ff%f). 14. ichikawa K., Pukushi K. and S, Ikawa,unpublishedwork. 15. Winston H. and H$lfordR. S.. J. C&em.Pkvs. 17.607 fl9491. I6 WoodwardL. A. attd SingerG. H., f. C&r&.S& 716(1958j. 17. Giskson J., Lloyd M. H. and Tuck D. G,, Znorg.Ckem. I@, 1907(1971). 18. ichihawa K. and Warren W. W. Jr., to be published. 19. Nakamote K., Infmed spet'tm~f~ffo~~~~ aul Cawi&~utj,a C~~~~~~~. W&y, NW York (i!X3), 20. Shimanouchi‘I’,, Tsuboi M. and MiyazawaK., .r. C&m. Pfrys.
35, 159711%1). 21. RadgerR. ha.,J; Ck~~. Pkys. 3,710 (I935), 22. Pauiing L., The Ne#greof tke Chemicaf Bomb. Come11University Press, New York (1968).
197!3.Vol. 40. pp. 2492%.
Papmm f’mr.
in Grot
PAed
Btitaim.
TECHNICAL NOTE FAR-IR SPECTRA OF InI, It& AND InIs K. kHIKAWA and s. IKAWA Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan (Received 21 February 1978;accepkd in revisedform 13June 1978)
Thermal analysis of the indium-iodme system[l, 21 shows the presence of 3 distinct compounds InI, InIs and It& with congntent melting points. Investigations on the crystal structure inch& X-ray d&action of InI[3,4] and InIs[S,6], and Raman and IR spectra of InI,[7-IO]. For solid In1 no attempt was made at assigning the Raman-active bands[ll]. Raman studii of It&[1 I, 121 suggested that the indium diide contained Inbanions. It follows that solid InIs might be most simply formulated as In’[InmI,]. The primary interest in the InIs compound was prompted by the hope of detecting unquivocai evidence of at least two distinct valence states, In’ and In’+ from IR studies. In order to elucidate this fascinating property this paper describes the results of far-IR investigations on three distinct compounds InI, InIs and InI,. Guaranteed reagent-grade InI, puritied by tripie vacuum distillation at 220-23tYCwas crystalline. The indium monoiodide was prepared from the In13, pm&d as above, and a stoichiometric excess of indium metal (99.99% pure). The product was puritied by vacuum distillation at 370_3800C[13], the vapor condensing on a cooler surface as brownish-red crystalline plates. InIs was prepared by reacting stoichiometric amounts of the purified InI and InI compounds at 229-m in uacuo. Tbe composition was checked .by chelatometric (In) and argentometric (I) analysis, with the result 33.0 at.% In. The X-ray powder technique confirmed that the InIs solid included no solid phase of InI[14]. In&urn monoiodide. Figure l(a) and Table 1 show the IR spectrum of ctystahine InI at room temperature. The observed band consists of a singk absorption line at 70cm-‘, associated with a weak shoulder at the hi-frequency side. This result is in strong contrast with previous Raman studIes[l2] which showed 5 Raman bands without assignment. Crystals of In1 have the Cmcm-Dz space group with an elongated 4 mokcule cell[3,4]. Factor group analysis[l5] provides the 3 IR-active modes of B,. +, Bzut. and B3. types for a crystal of InI. The 3 modes
T Fii.
1. Far-IR spectra for InI, InIs and InI,.
Table 1. Vibrational frequencies (in cm-‘) and stretching force constants (K in mdyne/A) of InI, InIs and InI
this work
WI
this work
IR
Raman
IR
70t
211 135 105 78 39
170 126 70 54 45 37
K=0.09
InL (SOhI)
In&
In1
WI
Raman 191 177 138 72 62 47
1141
fII1
191 185 138 74 58 47
InI this work
]71
181
191
223 174 150 122
226 179 157 125 60 49
228 178 158 125 59 49
214 173 153 123 57 48
Raman 185 139 58. 42
K = 0.82
v3V2)
v&41) v#,) ~03
dS,.) vl6@3.) Vl3uL) vd~3.) hdB3.) vI4@2.)
K = 1.42,0.64;[8]
tAssigned to v(In’-I-) in this work. 249
250
TechnioaINotes
approximatelycorrespond to In”-I- stretchingvibrations. along the aa, bs and ca axes respectivelyof the crystal. The umesoIvod band obtained here shows that the frequencies of the 3 mod@ are &se to each other. At this point it can be proposedthat itti is rouphlycharacterizedas a simpleionic crystal,e.g. N&i. Thus the ‘ZtIcm-’band is definitely assigned to the In’-I- stretching Z~diumdii~di~. The KR spectrum of I&, with vibratiounl assinnments. is shown in Pin. Ifbk and Table 1. The absorution Ii&, except for the peati-at 7&m-‘, readiIy correiate‘witb $ soiu~[I6], and the Raman spectra of inb- ions in in the sah (u-~r~;~~lni‘-rI~, as pointed oat in the pmv* ious Raman investigatiotts of solid ir&{f I, 121.it shouid be noted that two i&inactive bands ~,(A~~~~~(~},were cleat@ observed, and the band v&E) splits into two bands at 37 and &cm-‘, respectively. it is clear, therefore, that the compkx anion it&- has a symmetry tower than the point group Td.The band at 70cm-’ was assigned to the Iattiee viiratiou of the In” ion from its simiiarityto the 70cm-t band for the ini crystak it seems reasonableto supposethat the In” ion in crystaikte inIt is surrounded by some units of the anion Ini,- and acted on by a ~~~t~ 8eld similarto that k ini, whichis almosta simpk ionic crystal. In this case the Iattice &ration of the In” ion has a frequency in the same region as the in’ -I- stretchingvibration in ini. This assignment for the ?gcm-’ band in Inis is also supported by Raman studiesfI4]. ‘iite Couiomb ~~ b tween in’ and it&^ directly gives rise to a deviation from Tb point symmetry in the it&~ ion. Thtrs the tbtcidation of the distinct band at 70cm-’ is the minimum necessary to characa terke a mixed-valen~ state consist of in* and in-” and the I&~ ion, with the site symm~ less than Td is solid In&. Since both in” and in’+ exist as separate entities In inia at room temperature, this intermediate compound can be called “inho~~usiy ~~~v~n~‘~ it is worth whik noting thn&the depondenee of tbe “‘in relaxation rates on frequency C vesti8atedfor molten it& is reminiscentof local vaknce Iiucttm tions between the two distinct valence states in’ and In”+[i8]. Zodiac #atone. X-Ray wafyses showed that c~s~~ne I& is built of in& mokeutes with Z& symmetryand has the space group CzA.The infrared spectrumdue to the present work whicit is summarizedin Fig I(c) and Table I, agrees with previous iR studies{7-9fin wbicb the amdysesof the ~~rn~~ bands were satisfactoryperformed. The stretchingforce constant, K, of the in-l bond in the It&ion wns caktdated on the basis of the U~~R~ky force fieid[i9J,using the observedfrequenciesof It&, and the K value for ini was c&ulated rou8hiyusing a formuia for the optically active tat&e vibratiott of the NaCl-tvue s~~~~281. _ The Mues of K fmdyaes per & me listed kTahk 1 together witb those for ini,[g]. The increase in R in passingfrom ini to in& is much more abrupt compared with that in passhtg from init to inij. The magnitude of K ako suggests that the crystat fnl is c~cte~stic of a simpie ionic erystsl, e.g. NaCl, whose K vehtes have a magnitudeof 8.I n&A, e.g.[XI].Badger’sruie[Zl] may be used to cakukta the eq~~urn interuttcleardistance of
in-i in Ini,- for the wornout Inir from vibrational data alone. The bond force constants used in this tstk were substituted by each stretching force constant K for in1. ini? and I&. The distance was &imated as 2.74A 2 0.05 which & eompa&e to the distances 2.64and 2.84&5] of the terminal and bridgedin-i bond in the dimer in&. These separations must be assigned a covalent in-i bond because PauIing[22]gives 2.72A as the sum of the tetrahedral covalent radii of in and I. it is worth whiIe noti that the nearest and second-nearest distances 3.23 and 3.46? of In-i bonds in InIP] become more like the sum of the imivaknt ionic radii of in’ and i-, 3.48A[22]. Ac&~wkdg~ents-We wish to express thanks to Prof. M. Kimura for encant during the course of this work. One of us (K. i.) is also gratefulto him for hostility. 1. Thiel A. and Kaetschii., Z. QASMF. _ TV&em. _ Ckerra.66,288 (iSlO). 2. Peretti E. A., J, Am. Ckem. Sot. Z&5745(1956). 3. Jones R. E. and Temuk~n D. H.. AC& Crvst. 8.847 (19551. 4. WychoffR. W.G., ~~st~st~~~a~s, Vol,2.int~~~ie~~e,New York(1963). 5. Forester J. D., Zaikin A. and TempletonD. ii., Zuorg.C&r. 3,63 (I964). 7, BeattieI. R., Giison T. and Ozin G. A., J. Ckem. Sot. (At, 813 WM. 8. Adams D. M. and Ch~ch~l R. G,, .Z,CZteur,Sot. (A). 2141 (1968);and Z. Ckem. Sot. (A),697(197tB. 9. Greenwood M. N., Prince D. J. and Stranghan B. P., J.
Ckem. Sac, [A), I634 ft%Q. 10. Bncs V. W., Aithras 2. and Okon G., Z. &roe. Affgem, Ckem. 428,193(1976).
Ii. Davies J. B., Waterwo~ L. G. and Worrah I. J., f. hag. Nwi. Ckem. 36, IMM ( 1!474). 12.Con&erasJ. G., Poland 1. S. and Tuck D. G., I. Ckem. SM. @?&onf, 922(1973). 13. Rolsten R. F,, Zodfde &i&is and Mefuf Zedides. Wiley, New York ff%f). 14. ichikawa K., Pukushi K. and S, Ikawa,unpublishedwork. 15. Winston H. and H$lfordR. S.. J. C&em.Pkvs. 17.607 fl9491. I6 WoodwardL. A. attd SingerG. H., f. C&r&.S& 716(1958j. 17. Giskson J., Lloyd M. H. and Tuck D. G,, Znorg.Ckem. I@, 1907(1971). 18. ichihawa K. and Warren W. W. Jr., to be published. 19. Nakamote K., Infmed spet'tm~f~ffo~~~~ aul Cawi&~utj,a C~~~~~~~. W&y, NW York (i!X3), 20. Shimanouchi‘I’,, Tsuboi M. and MiyazawaK., .r. C&m. Pfrys.
35, 159711%1). 21. RadgerR. ha.,J; Ck~~. Pkys. 3,710 (I935), 22. Pauiing L., The Ne#greof tke Chemicaf Bomb. Come11University Press, New York (1968).