The vibrational spectra of Al2Br6, Al2I6, Ga2Br6, Ga2I6, and In2I6

Abstract

The Raman and i.r. spectra of the title compounds are recorded in various phases. Using helium-neon laser excitation the Raman spectra of intensely coloured melts of Ga,l , and ln216 are recorded. Vibrational assignments are made for all compounds using a normal-co-ordinate treatment identical to that used previously for Ga, CI , .ON the basis of new experimental data coupled with normal-co-ordinate calculations, two of us recently made a major reassignment of the Ga,Cl, mo1ecule.l It was subsequently suggested to us that the treatment could not be extended to Ga,Br6. As we were interested in possible reasons for this behaviour we decided to reinvestigate a number of Group I11 trihalide molecules of the type M,X,. In particular we wished to examine M,I, species where the spectral data were very restricted. Raman and i.r. data on the title compounds are reported in Tables 1-5.The calculated values reported in these Tables were obtained by techniques identical to those developed in the earlier paper,l which should also be consulted for nomenclature. Our assignments frequently differ from those of earlier workers, largely owing to the fact that we have available the results of normal-co-ordinate analyses. However, the generally improved spectral data (attributable at least in part to excellent instrumentation) also helped, notably in the assignment of polarised bands.Aluminium Tribromide (Table 1) .-The most recent assignments for this molecule are due to Miller,2 whose calculated values include predictions for the i.r.-active bands. Our polarisation data unambiguously confirm

Vapour pressures and sublimation enthalpy of solid indium(III) iodide

“…This finding disagrees with the investigations of Akishin et al (2) and of Beattie et al (3) These authors only found the monomeric form in the vapour; on the other hand, Broude (4) considers it to comprise the dimeric form alone. Bencze et al's (1) results agree with those of Giricheva et al, (5,6) who, from electron diffraction measurements, estimated the mole fraction x{In 2 I 6 (g)} 1 0.2 at T = 473 K. The vaporization of InI 3 was previously studied by other researchers.…”

“…Some interesting applications of InI 3 vapour were described by Bencze et al (1) These authors, using the Knudsen effusion technique coupled with a mass-spectrometer, observed several ionic species in the spectra over solid InI 3 , but proved that InI 3 (g) and In 2 I 6 (g) are the only gaseous species present in the vapour. This finding disagrees with the investigations of Akishin et al (2) and of Beattie et al (3) These authors only found the monomeric form in the vapour; on the other hand, Broude (4) considers it to comprise the dimeric form alone.…”

Synthesis and characterization of Hg(II) complexes of Me3MCH2SeMe, (M = Si, Ge). Crystal structures of [HgX2(Me3SiCH2SeMe)]2, X = Cl, Br, I

“…Similarly the Hg-X, bending mode, G(Hg-X,), can be assigned by comparison with v2 in HgC12 (126) (33), HgBr2 (66) (34), and Hg12 (26 cm-' (32) , and 162cm-' respectively also match the increase in the bond lengths of Hg-Se along the series, i.e., 2.70(1), 2.81(2), and 2.862(2)A. In species such as A12X6, Ga2X6, and In216, where there are both bridging and terminal halogen bonds, the ratio of the assigned frequencies, v(M-Xb), varies from approximately 1 :2 (e.g., in A1216) (35) to 3:4 (e.g., Ga2C16) (36). The assignments in the [HgX2(Me3-MCH2SeMe:,I2 adducts fall in this range, with the biggest difference being noted for the chloride, where there is the largest differtnce between the Hg-Cl,, 2.354(5), and HgClb, 2.70(1) A, bond lengths.…”

Theoretical studies on vibrational spectra of some aluminum halides: Effect of theoretical methods and basis sets

“…However, later studies described the aluminum triiodide crystals to be molecular, consisting of Al 2 I 6 units [14]. On the other hand, there have been numerous spectroscopic studies of aluminum halides, including matrix isolation infrared (IR) spectroscopic study [15,16] and an IR and Raman spectroscopic study of the melt [17] and gas-phase [18][19][20]. Although ab initio molecular orbital [21,22] calculations have been performed for AlX 3 and Al 2 X 6 (X = Cl and Br), little has been studied for these molecules by high-level computational techniques [23,24].…”