4248
J. Phys. Chem. 1992, 96,4248-4254
Photochemistry of Hydrogen Sulfide-Fluorine Complexes in Solid Argon. Infrared Spectra of (HSF) (HF) Complexest Lester Andrews,* Thomas C. McInnis, and Yacine HaMachi* Department of Chemistry, University of Virginia, Charlottesville, Virgina 22901 (Received: October 11, 1991; In Final Form: January 14, 1992)
*
Codepition of H2Sand F2in ex- argon on a cold window at 12 1 K gave sulfur fluorides and evidence for Lewis acid-base precursor complexes. Photolysis of these complexes with 590-1000-nm light formed several new products. Ab initio SCF calculations with the standard double-{ plus polarization function (DZP) basis set were performed to support the identification of new product species. The HSF- -HF and HFS- -HF complexes exhibited H-F stretching modes at 3850 and 3724 cm-I and S-F stretching modes at 759 and 816 cm-I, respectively. The most stable arrangement was a cyclic (HSF)(HF) complex, which exhibited a strongly perturbed H-F stretching mode at 3383 cm-I and librational mode at 508 cm-l. The remarkable observation of F2 dissociation at 590 nm in the hydrogen sulfide complexes, as opposed to F2 dissociation at 290 nm in the (H20)(F2)complex, is attributed to sulfur-fluorine interaction which enhances the continuous red absorption of fluorine.
Introduction Matrix reactions with H2S and F2 have been investigated to compare with previous work performed on the H20and F2 system in this laboratory' and to prepare the new unstable HSF species. Hydrogen ~ u l f i d e ,molecular ~.~ complexes with H2S,4-6and sulfur-fluorine chemistry7+' have been studied extensively by infrared spectroscopy, but the reactive HSF molecule has not been identified, although a tentative assignment has been propared.'O Since H O F complexes with H F have been produced by H 2 0 + F2 reactions,'Ji it is possible that HSF can be made by reacting H2S + F2. In addition, matrix reactions of PH3 and F2produced the phosphorane PH3F2,I2and the possible formation of an analogous compound by the addition of F2 to H2S was worthy of consideration. Experimental Section The vacuum and cryogenic apparatus and techniques for matrix fluorine photochemistry have been described previ~usly.'~-'~ Spectra in the 400-4000-mr1region were recorded using a Nicolet 7199 FTIR spectrometer. The matrices were scanned 500-1000 times at 1-em-' resolution, giving a wavenumber accuracy of f0.3 cm-'. Additional experiments were performed to obtain far-IR spectra using a Perkin-Elmer 983 infrared spectrophotometer; samples were scanned 1-5 times at 2-em-' resolution, giving a *0.5 cm-' wavenumber accuracy. H2S (Matheson) and D2S (approximately 90% deuterium enriched, synthesized by condensing HIS with D20) were diluted with argon to Ar/sample ratios of 50/1, 100/1, 150/1, or 200/1.6 The hydrogen sulfide samples in argon were initially deposited on a 12 f 1 K CsI window at rates ranging from 2 to 6 mmol/h, and the spectrum of HIS or D2S was recorded. Fluorine (Matheson) was diluted with argon to Ar/F2 ratios of 50/1,100/1, or 200/1, passed through a 77 K U - t ~ b e ' ~at. '2-6 ~ mmol/h, and codeposited with the hydrogen sulfide samples for up to 5 h, and another spectrum was recorded. The sample was photolyzed with a high pressure mercury arc (1000 W; BH6-1B, T. J. Sales, Fairfield, NJ) using a cooled 10-cm water filter along with 690-, 590-, or 420-nm Coming glass long-wavelength pass filters backed by Pyrex for 0.5-1.0-h periods, and another spectrum was recorded. The matrix was again photolyzed using the same light source, but with only the H 2 0filter (passes 220-1000 nm), and another spectrum was recorded. The matrix was then warmed to 20-30 K and recooled to 12 K, and another spectrum was recorded. Results Hydrogen sulfide samples were diluted by argon and codeposited at 12 K with fluorine diluted by argon. New product absorptions Taken in part from the M.S. thesis of T.C.M., University of Virginia. $On leave from the Laboratoire de Spectrochimie Moleculaire (URA508), Universite Pierre et Marie Curie, Paris, France.
TABLE I: Product Absorptions (cm-') of Complexes Formed between F2 with H2S and D2S and Their Photolysis Products in Solid Argon'
H,S
+ F7
D,S
+ F7
assignment u,(HF), 1, HSF--HF u,(HF), 2, HFS- -HF u,(HF), 3, (H,S)(HSF)--HF v,(HF), 4, cyclic-(HSF)(HF) v(S-H), C, (H2S),--F2 (x = 1 or 2) v(S-H), C', (HSD),--F, b(HSF), 5 , HF--HSF G(HSF), 1, HSF--HF v(S-F), 6, FS- -HF u(S-F), 2, HFS--HF u(S-F), 5, HF--HSF v(S-F), 1, HSF--HF uI(HF), 4, cyclic-(HSF)(HF) UI(HF),4 VI(HF),2 VI(HF),2 VI(HF),1 'Bands at 3769, 3667, and 3631 cm-l that increased markedly on annealing are probably due to (HF), complexes with HSF involving hydrogen bonding to sulfur. bProbably masked by 736-cm-I band. 3850.7 3724.4 3703.8 3383, 3380 2594.3 2587.9 1022.8 1013.6 820.5 8 15.9 787.8 759.5 515 sh 508 45 1 436 413
2822.9 2733.3 2720.7 2516, 2509 1874.4 1887.5, 1880.6 b 740.6 820.9 820.9 79 1.6 763.3 381 sh 375 33 1 319
for H2S and D2S reactions with F2 will be presented. H2S F2. Twelve codeposition experiments were performed with H2Sand F2using different combinations of argon dilutions of H2S (50/1, 100/1, 150/1, and 200/1) and F2 (50/1, 100/1, and 200/ 1) and different cold window temperatures. Infrared spectra are illustrated in Figures 1-3 for a 12 K experiment, with 100/1 samples and 6 mmol/h spray-on rates, and new product absorptions are listed in Table I. Absorptions labeled HF at
+
(1) McInnis, T. C.; Andrews, L. J . Phys. Chem. 1992, 96, 2051.
(2) Tursi, A. J.; Nixon, E. R. J . Chem. Phys. 1970, 53, 518. See also: Pacansky, J.; Calder, V. J . Chem. Phys. 1970, 53, 4519. (3) Barnes, A. J.; Howells, J. D. R. J . Chem. Soc.,Faraday Trans. 2 1977, 68, 729. (4) Agarwal, U. P.; Barnes, A. J.; Orville-Thomas, W. J. Can. J . Chem. 1985, 63, 1705. ( 5 ) Legon, A. C.; Millen, D. J. Acc. Chem. Res. 1987, 20, 39. (6) Arlinghaus, R. T.; Andrews, L. Znorg. Chem. 1985, 24, 523. (7) Haas, A.; Willner, H. Spectrochim. Acta 1978, 34, 541. (8) Redington, R. L.; Berney, C. V. J. Chem. Phys. 1965, 43, 2020. (9) Hassanzadeh, P.; Andrews, L. J. Phys. Chem. 1992, 96, 79. (IO) Machara, N. P.; Auk, B. S. J . Mol. Srruc. 1988, 172, 129. (11) Noble, P. N.; Pimentel, G.C. Spectrochim. Acra 1968, 24A. 797. (12) Andrews, L.; Withnall, R. Znorg. Chem. 1989, 28, 494. (13) Johnson, G.L.; Andrews, L. J . Am. Chem. SOC.1980, 102, 5736. (14) Johnson, G. L.; Andrews, L. J. Am. Chem. SOC.1982, 104, 3043. (15) Andrews, L.; Johnson, G.L. J . Phys. Chem. 1984,88,425. (16) Andrews, L.; Lascola, R. J . Am. Chem. SOC.1987, 109, 6243.
0022-3654/92/2096-4248$03.00/0 0 1992 American Chemical Society
The Journal of Physical Chemistry, Vol. 96, No. 11, I992 4249
Photochemistry of H2S-F2 Complexes in Ar(s)
4 1
I
4
211'
N
a.
N
a.
N
-I 1100
1000
900
600 $00 UfiVENUMEEAS
Boo
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400
Figure 3. Infrared spectra in the 400-1 lOO-cm-' region for the sample shown in Figure 1.
4
'+OOO
3h00
3f00
3600
3800
3500
3300
3400
UAVENUMBERS
Figure 1. Infrared spectra in the 3300-4000-cm-' region for Ar/H2S = 100/1 and Ar/F, = 100/1 samples using 6 mmoles/h spray-on rate: (a) from codeposition at 12 f 1 K, (b) after photolysis with 590-nmcutoff filter for 0.5 h, (c) after full arc 220-1000-nm photolysis for 0.5 h, and (d) after annealing to 25 1 K.
*
w
u Z
a
m?
a
D v)
m Q:
I
'
3
N
9
2400
2800
zfoo
2600
2500
I
2400
Wf3VENUMBERS
Figure 2. Infrared spectra in the 2400-2900-cm-' region for the sample shown in Figure 1. Hydrogen sulfide sample contains approximately 10% deuterium enrichment.
3962.7, 3954.1, and 3919.5 cm-l are due to hydrogen fluoride; which came in part from reaction during deposition and in part from the F2 ~amp1e.I~ The absorption at 3881.4 cm-I, labeled N, is due to the Nz-HF complex, and the 3756.4-cm-' band, labeled W, is due to water."J* The weak absorptions at 3711.5 and
3564.0 cm-' are due to H2S--(HF)2, while stronger bands at 3652, 508, and 48 1 an-'are due to the Ha--HF complex.6 Absorptions at 2629.9, 2620.3, 2581.8, and 2568.8 cm-' are assigned to the HIS precursor monomer and dimer.2q3 Previously identified sulfur-fluorine reaction products were found in the 700-1000-Cm-i SiF4 impurity in fluorine absorbed at 1023.2 cm-I, and a band due to SF, was observed at 938.1 cm-1.19,20The 884.4-, 859.8-, and 705.5-cm-' bands belong to SF,! while the absorptions at 832.6 and 804.6 cm-' are attributed to SFp7 Finally, the bands at 797.9 and 740.6 are due to OSF2.* These latter reaction products were weaker in experiments with slower deposition rates and lower sample concentrations, and stronger in experiments with higher (up to 17 f 1 K) cold window temperature. In the H F stretching region, photolysis with 590-1000-nm radiation produced a sharp absorption at 3850.7 cm-' with a site splitting at 3842.6 an-',both labeled 1. The bands decreased 75% upon full arc (220-1OOO-nm) photolysis and showed slight growth on annealing. A weak absorption appeared at 3769.2 cm-' on full arc photolysis and doubled on annealing. A very strong absorption appeared at 3724.4 cm-I, labeled 2, upon photolysis at 590 nm. Full arc photolysis increased the latter absorption by 40% while annealing allowed slight growth. An equally strong absorption, labeled 3, appeared at 3703.8 cm-' on 590-nm photolysis, but 220-nm photolysis produced a marked decrease in the absorption, although annealing caused the band to grow back to nearly 50% of its original intensity. New bands appeared at 3667 and 3631 cm-' on 220-nm photolysis and grew markedly on annealing. Finally, a strong, broad absorption labeled 4 appeared at 3383 cm-' on 590-nm photolysis, increased markedly on 220-nm irradiation, and was decreased slightly on annealing. In the S-H stretching region, an absorption at 2594.3 cm-I, labeled C, formed on deposition and decreased markedly upon 590-nm photolysis. In the H-S-X bending region, a medium intensity band at 1013.6 cm-', labeled 1, and weak new 1022.8cm-' absorption on top of SiF,, labeled 5, appeared upon 590-nm photolysis; 220-nm photolysis caused a 75% decrease in the 1013.6-cm-' absorption, whereas the new absorption at 1022.8 cm-' was destroyed leaving the original SiF, band at 1023.2 an-'. (17) Redington, R. L.; Milligan, D. E. J . Chem. Phys. 1962, 37. 2162. (18) Ayers, G. P.; Pullin, A. D. E.Spectrochim. Acro 1976, 32A, 1629. (19) Jones, L. H.; Swanson, B. 1.; Ekberg, S.A. J . Chem. Phys. 1984.81, 5268.
(20) Swanson, B. 1.; Jones, L. H . J . Chem. Phys. 1981, 74, 3205.
4250 The Journal of Physical Chemistry, Vol. 96, No. 11, 1992
Andrews et al.
4
C'
DIS--DF
I 2950
2850
z'rso 2650 WAVENUMBERS
1900 1800 l+OO WWENUMEERS Figure 5. Infrared spectra in the 1700-2100-cm-' region for the sample shown in Figure 4. 00
zsso
2450
Figure 4. Infrared spectra in the 2450-2950-cm-' region for Ar/D2S = 100/1, approximately 90% deuterium enriched, and Ar/F2 = 50/1 samples: (a) from codeposition at 12 f 1 K, (b) after photolysis with 420-nm cutoff filter for 0.67 h, and (c) after full arc 220-1000-nm photolysis for 0.75 h.
In the S-F stretching region deposition produced weak bands at 986,778,760,726, and 533 cm-' and strong bands at 386 and 280 cm-I. Red photolysis markedly decreased the 986-, 760-, and 533-cm-' bands, while 220-nm photolysis destroyed the 778-, 726-, 386-, and 280-cm-' bands. In addition, codeposition produced a weak absorption at 820.5 cm-I, labeled 5. Filtered photolysis increased the 820.5-cm-' band and produced a new 815.9-cm-' band, labeled 2; full arc photolysis and annealing continued this trend. A new band, labeled 5, appeared at 787.8 cm-I on 590-nm photolysis; full arc photolysis destroyed this absorption, and annealing allowed for some regrowth. The sharp band at 759.5 cm-I, labeled 1, appeared with filtered photolysis and decreased by approximately 75% upon full arc photolysis, while annealing had little effect. Annealing increased weak SF4 absorptions and produced OzFat 1489 cm-1,21but SF6and OSF2bands were not changed. In the lower frequency region, 590-nm photolysis produced a new 508-cm-l absorption with a 5 15-cm-I shoulder, labeled 4, new absorptions a t 451 and 436 cm-I, both labeled 2, and a new band at 413 cm-I, labeled 1. Some DF impurity in the system was evidenced by the D F absorption at 2896.2 and 2877.3 cm-I in the HzS experiment^.'^ In addition, the weak band at 2687.3 cm-l is due to the HzS--DF complex.6 A small amount (10%) of deuterium impurity gave the 1 band at 2822.9 cm-I, the 2 band at 2727.2 cm-I, the 3 band at 2722 cm-l, the 4 band at 2516 cm-' (Figure 2), and C' bands of comparable intensity a t 2587.9 and 1880.6 cm-I. An experiment using Ar/HzS = 100/1 and Ar/Fz = 200/1 and a 2 mmol/h spray-on rate is noteworthy in contrast. The product yield was about 0.3 times the new absorptions in Figures (21) Arkell, A. J . Am. Chem. SOC.1965, 87, 4057.
2000
1 and 3 and the SFz, SF,, OSFz, SF,, and species 6 product bands were absent from the spectrum. In this experiment 690-1000.nm filtered photolysis gave the 1, 2, 4-6 product bands with absorbances in the 0.01-0.04 range. Photolysis at 630-1000 nm tripled these band absorbances; photolysis at 590-1000 nm increased these bands another 50% and the isolated HF bands attained a 10% increase in absorbance. A final 220-100anm photolysis reduced group 1 bands by lo%, increased group 2 and 4 bands by 50% almost destroyed group 3, reduced group 5 by 50%, and increased the 6 band by 50%. Annealing to 29 f 1 K reduced group 1 bands by 40%,left group 2 and 4 bands unchanged, increased the species 3 band by 600%, increased the group 5 bands by 300%, increased the species 6 band by 200%, and produced weak SF4 and OzF bands. A final H2S/F2experiment was done with 1% samples of each reagent and the slower spray-on rate, but annealing was performed before photolysis. None of the above product bands appeared on annealing to 21 K, and annealing to 29 K produced only weak SF4 and 820.5-cm-' species 6 bands. Photolysis at 590 nm produced the group 1-6 bands as described above with the same relative intensities for 1, 2, 4, and 5 bands, but the 3 band was e n h a n d , 220-nm photolysis increased the group 2,4, and 6 bands and decreased group 1 and 5 bands as before, but a larger relative yield of the 3769-, 3667-, and 3631-cm-l bands was observed. D&3+ FS.Seven deposition experiments were performed with D2Sand Fz using varying combinations of argon dilutions of D2S (75/1, 100/1, and 200/1) and Fz (50/1, 100/1, and 200/1). Infrared spectra are illustrated in Figures 4-6, and new product absorptions are listed in Table I. Absorptions labeled DF at 2895.6 and 2876.5 cm-I are due to deuterium fluoride, and absorption at 2845.6 cm-I, labeled N , is due to the N2--DF complex.12 The bands at 2684.3, 2630.3, and 2508.6 cm-l are due to D2S--DF and D,S--(DF), respectively! Because of the synthesis procedure, a weak hydrogen-containing dimer band was found at 2579.0 cm-', but (D& bands were observed at 1870.7 and 1862.1 c ~ - I . ~ J No shift was observed for SF6, SF4,SF2,and SOF2in the deuterium experiments. Owing to the presence of hydrogen impurity in the deuteriated precursor, the H F stretching region revealed photolysis product
The Journal of Physical Chemistry, Vol. 96, No. 11, 1992 4251
Photochemistry of H2S-F2 Complexes in Ar(s)
N.1
1
a
m?
a
I
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I
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850
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Figure 6. Infrared spectra in the 450-1050-cm-' region for the sample shown in Figure 4.
bands at 3850.2, 3720.2, and 3380 cm-'. b In the D F stretching region, photolysis with a 420-nm light produced sharp absorptions at 2822.9 cm-I with a 2817.8-cm-l F shoulder, both labeled 1. Full arc photolysis produced a slight increase in the absorptions. Visible photolysis also yielded bands at 2733.3 and 2720.7 cm-I, labeled 2 and 3, respectively, while 220-nm photolysis caused the 2733.3 cm-'band to increase slightly and the band labeled 3 decreased by almost 40%. A strong band labeled 4 was observed a t 2509 cm-' with a 2516-cm-' shoulder (Figure 4). In the S-D stretching region, three sharp bands at 1887.5, 1880.6, and 1874.4 cm-l, labeled C', C', and C", respectively, were formed upon deposition and destroyed upon 420-nm photolysis (Figure 5). The S-F stretching region revealed a weak band at 820.9 cm-I, C labeled 2, which formed on deposition and increased only slightly on successive photolyses. A sharp band at 791.6 cm-' with a shoulder at 788.3 cm-l, labeled 5, grew in upon 420-nm photolysis. The bands decreased by nearly 45% on full arc photolysis. A more intense, sharp absorption at 763.3 cm-l, labeled 1, and a 506-cm-I band with 514-cm-l shoulder were produced by filtered photolysis; full arc photolysis produced only a slight increase in the products (Figure 6). Finally, far-infrared experiments showed photolysis product bands at 375 cm-' with a 381-cm-l shoulder and a t 331 and 319 cm-I. A 519-cm-l band and very strong absorptions at F 387 and 282 cm-I were formed on deposition, disappeared upon 220 nm photolysis, and were reformed in part on annealing. Calculations. Ab initio calculations have been carried out at d the S C F level with the HONDO 7.0 computer p r ~ g r a mon ~ ~ , ~ Figure ~ 7. (a) Cyclic (HSF)(HF), (b) HSF--HF, (c) HFS--HF, and (d) HF, HIS, HSF, H2SF2,and four complex species involving H F FSH- -FH. and HSF (Figure 7). All the calculations have been performed with the standard double-{ plus polarization function (DZP) basis systems involving relatively highly polarizable molecules, like HSF, set. Geometries were fully optimized using analytical gradients. were not taken into account. Accordingly, agreement with exVibrational frequencies and IR intensities were also calculated periment cannot be more than qualitative. However, the present within the double harmonic approximation to help in the intergoal is not to get the most accurate geometrical parameters and pretation of the experimental data and to ensure that the structures interaction energies but rather to help in the interpretation of the obtained were true minima. Force constants were obtained via experimental spectra. This level of theory should nonetheless the finite difference of analytical first derivatives, while dipole reproduce the relative trends obtained with more sophisticated derivatives were obtained numerically. Since the calculations were calculations. done at the S C F level, dispersion forces, which are important in The optimized geometries, HF stretching frequencies, dipole moments, and interaction energies are reported in Table 11. Four isomers of the (HF)(HSF) complex were considered in this study, (22) Dupuis, M.; Watts, J. D.; War, H. 0.;Hurst, G. J. B. Comput. Phys. a cyclic structure (Figure 7a), HSF- -HF (Figure 7b), HFS- -HF Commun. 1989, 52, 415. (Figure 7c), and FSH--FH (Figure 7d). (23) Dupuis, M.; Rhys, J.; King, H. F. J . Chem. Phys. 1976, 65, 111.
4252 The Journal of Physical Chemistry, Vol. 96, No. 11, 1992
Andrews et al.
TABLE 11: Calculated Bond Distances ( r , A), Bond Angles (a,deg), HF Stretching Frequencies (u, cm-I), Dipole Moments (fi, D), and Interaction Energies (Ei,kcal/mol) intermolecular a(HSH) molecule r(HF) r(SH) r(SF) distance a(HSF) WF) c1 Eint HF 0.903 4513 2.03 1.331 94.1 1.34 H2S HSF 1.331 1.610 95.9 2.03 1.319 1.701 102.0 1.04 H2SF2 1.614 96.1 FSH- -FH 0.904 1.329 2.418 4494 3.93 -1.91 0.906 1.331 1.605 2.627 HFS- -HF 96.3 4433 2.53 -2.59 1.624 0.906 1.330 1.942 95.1 HSF- -HF 4455 4.63 -3.84 0.907 1.33 1 1.626 1.993 cyclic(HSF) (HF) 95.1 4440 1.82 -4.22 2.708 TABLE III: Calculated Vibrational Frequencies at the SCF/DZP Level for SF, HSF, HfiF1, and (HSF)(HF) Complexes molecule frequencies, cm-' SF 907 (822 observed)" HSF 2855, 1132, 879b DSF 2051, 829, 880 2966, 2939, 1386, 1344, 1235, 672: 606, H2SF2 397,' 41 3' 2138, 2104, 1008, 959, 902, 606, D2SF2 393: 386'
FSH- -FH HFS- -HF DSF- -DF HSF- -HF DSF- -DF cyclic(HSF) (HF) cyclic(DSF)(DF)
4494, 2878, 1137, 873, 152, 122 4433, 2856, 1132, 888,423, 372 3214, 2052, 829, 889, 303, 268 4455, 2863, 1128, 853, 414, 382 3229, 2057, 825, 855, 297, 274 4440, 2862, 1136, 850, 466, 393 3219, 2056, 829, 852, 337, 283
"Reference 9. bMost intense band by factor of 10.
