Splitting of Hydrogen Sulfide by Group 14 Elements (Si, Ge, Sn, Pb) in

Aug 9, 2018 - School of Chemical Science and Engineering,. Tongji University, Shanghai, 200092,. China. Email Address: [email protected] (X.L.)...
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Splitting of Hydrogen Sulfide by Group 14 Elements (Si, Ge, Sn, Pb) in Excess Argon at Cryogenic Temperatures Xing Liu,*,† Xiaorui Liu,† and Xuefeng Wang*,‡ †

College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China Shanghai Key Lab of Chemical Assessment and Sustainability, School of Chemical Science and Engineering, Tongji University, Shanghai, 200092, China



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S Supporting Information *

ABSTRACT: The water gas reaction C + H2O → CO + H2 has been employed for centuries; however little is known for analogous reaction M + H2S → MS + H2 (M = Si, Ge, Sn, Pb). In addition, this latter reaction is intriguing in its function of converting pollutant H2S to clean energy source H2. We report herein the reactions of laser-ablated Group 14 atom M (M = Si, Ge, Sn, Pb) with H2S using matrix isolation infrared spectroscopy as well as the state-of-the-art quantum chemical calculations. Important reactive intermediates HMSH with high active H (protonic Hδ+ and hydridic Hδ−) are identified. In addition, the reaction mechanisms are established for insertion reaction M + H2S → HMSH, and photoinduced H2 elimination reactions of HMSH → MS+ H2 and H2SiS → SiS+ H2 in low-temperature matrices.





INTRODUTION

EXPERIMENTAL AND COMPUTATIONAL METHODS Laser-ablated group 14 atoms (Si, Ge, Sn, Pb) were reacted with H2S in excess argon during condensation at 4 K using a Sumitomo Heavy Industries RDK-205D cryocooler, and the methods were described previously.15,16 New species that formed in solid matrix were identified and characterized from matrix isolation infrared spectra using H2S, H234S and D2S reagents. The Nd:YAG laser fundamental (Continuum Minilite II, 1064 nm, 15 Hz repetition rate with 5 ns pulse width) was focused (about 10 mJ/pulse) onto silicon, germanium, tin and lead targets (Alfa Aesar), which produced bright plumes from the target surfaces spreading uniformly to the 4 K CsI window. The H2S (Matheson) was further purified (condensed and degassed) before using, and deuteriumenriched sample was synthesized by reacting ferrous sulfide with H2SO4 diluted in D2O. The sample of H234S was prepared by reacting H2SO4 (4M) with Fe34S, which is formed from the reaction of pure iron powder with sulfur-34 (98.8% 34S, Cambridge Isotope Laboratories) at a temperature of around 350 °C. All the samples were dried over fresh P2O5 powder.17 FTIR spectra were recorded on a Bruker Vertex 80v spectrometer at 0.5 cm−1 resolution between 4000 and 400 cm−1 using a MCTB detector. Matrix samples were annealed at different temperatures, and some selected ones were subjected

The reactivity of the group 14 elements has been extensively studied in the past few decades,1−9 and it has been established that this group atoms can readily form complexes even with water.10−12 Spectroscopic evidence of the isomers HMOH (M = Si, Ge, Sn, Pb) and H2MO (M = Si, Ge) have also been reported.10−12 More interestingly, the weak infrared absorptions due to MO (M = Si, Ge, Sn) were observed increasing at the expense of HMOH on photolysis,10−12 implying one possible way of H2 elimination. It will be of great significance if similar process occurs for the sulfur substituted reagent gas H2S, because the H2S-splitting reaction, especially the underlying mechanism, is extremely important for both toxic pollution control and hydrogen energy regeneration. Although a previous study suggests silanethione (H2SiS) as the most stable species in the target reaction,the decomposition product SiS + H2 is more favorable along the reaction coordinate.13,14 To explore the potential of H2 elimination from H2S, we investigate the reactions of M (M = Si, Ge, Sn, Pb) atoms with hydrogen sulfide molecules using matrix isolation infrared spectroscopy and state-of-the-art quantum chemical calculations. We found that the infrared spectra recorded after irradiation of argon matrices containing H2S and M atoms show very strong bands due to MS species. The generated MHy (y = 1, 2, 4) hydrides further confirmed the H2 production. Additionally, distinctive reaction mechanism of group 14 elements in the relevant reactions is revealed based on our theoretical calculations. © XXXX American Chemical Society

Received: May 10, 2018 Revised: August 7, 2018 Published: August 9, 2018 A

DOI: 10.1021/acs.jpca.8b04428 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry A

Table 1. Calculated and Observed M−H, M−S, and S−H Stretching Frequencies of HMSH (1A′) (M = Si, Ge, Sn, Pb) and H2SiS (1A1) Moleculesa B3LYP H2S

D2S

CCSD(T) 34

H2 S

H2S

499.1(41) 2038.1(225) 2664.3(0)

499.2(40) 1466.4(118) 1913.1(0)

492.1(40) 2038.1(225) 2662.0(0)

520.0 2067.1 2695.8

385.9(37) 1890.8(307) 2667.8(0)

381.6(35) 1346.3(157) 1915.8(0)

378.1(35) 1890.8(307) 2665.5(0)

401.8 1925.0 2702.2

319.9(38) 1660.7(446) 2679.0(1)

315.8(38) 1179.7(226) 1923.8(1)

312.6(37) 1660.7(446) 2676.6 (1)

325.5 1675.5 2710.6

286.4(36) 1579.4(506) 2679.9(1)

282.6(36) 1120.0(255) 1924.5(0)

279.2(34) 1579.4(506) 2677.5 (1)

288.7 1558.0 2707.2

1012.9(123) 2216.9(77) 2230.1(96)

771.9(96) 1587.2(51) 1614.2(56)

1012.9(122) 2216.9(77) 2230.1(96)

1013.6 2261.0 2272.4

obsd 34

D2S HSiSH 516.0 1487.1 1935.6 HGeSH 397.1 1370.8 1940.3 HSnSH 320.8 1190.1 1946.4 HPbSH 285.0 1104.8 1943.9 H2SiS 771.7 1619.0 1644.5

H2 S

H2S

D2S

H234S

mode assignment

512.7 2067.1 2693.4

1960.4

1428.5

1960.4

Si−S str Si−H str S−H str

394.5 1925.0 2699.8

1823.1

1315.0

1823.1

Ge−S str Ge−H str S−H str

317.8 1675.4 2708.2

1653.0

1188.1

1653.0

Sn−S str Sn−H str S−H str

281.6 1558.0 2704.8

1538.1

1103.5

1538.1

Pb−S str Pb−H str S−H str

1013.5 2261.0 2272.4

986.0 2153.4 2167.1

762.2 1535.2 1571.7

986.0 2153.4 2167.1

H−Si−H bend Si−H sym-str Si−H antisym-str

Frequencies and intensities (in parentheses) are in cm−1 and km mol−1.

a

Figure 1. Infrared spectra of the Si atom and H2S reaction products in solid argon at 4 K. (a) Si + 0.2% H2S deposition for 60 min; (b) after annealing to 20 K; (c) after 300 < λ < 780 nm irradiation; (d) after full-arc irradiation; (e) after annealing to 35 K; f−j reproduce the spectra of a−e except replacing 0.2% H2S with 0.4% (H2S + H234S); k−o reproduce the spectra of a−e except replacing 0.2% H2S with 0.4% (H2S + HDS + D2S).

accurate energy and reliable vibrational frequencies for the reaction products. Geometries were fully relaxed during optimization, and the optimized geometry was confirmed by vibrational analysis.

to irradiation from a medium-pressure mercury arc lamp (Philips, 175W) with the outer globe removed. Complementary electronic structure calculations were carried out using the Gaussian 09 package,18 the B3LYP density functional,19,20 and coupled-cluster methods including triple excitations CCSD(T).21 During all the calculations, the 6-311++g(3df,3pd) basis set22 was used for H, S, Si and Ge, and the Stuttgart ECPS23 for Sn and Pb in order to provide



RESULTS AND DISCUSSION Infrared spectra for the reaction products of M (M = Si, Ge, Sn, Pb) atoms with H2S molecules in excess argon will be B

DOI: 10.1021/acs.jpca.8b04428 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry A

Figure 2. Infrared spectra of the M (M = Ge, Sn, Pb) atom and H2S reaction products in solid argon at 4 K. (a) Ge + 0.2% H2S deposition for 60 min; (b) after annealing to 20 K; (c) after 300 < λ < 780 nm irradiation; (d) after full-arc irradiation; (e) after annealing to 35 K; f−j reproduce the spectra of a−e except replacing Ge with Sn; k−o reproduce the spectra of a−e except replacing Ge with Pb.

Figure 3. Infrared spectra of the M (M = Ge, Sn, Pb) atom and H2S reaction products in solid argon at 4 K. (a) Ge + 0.2% H234S deposition for 60 min; (b) after annealing to 20 K; (c) after 300 < λ < 780 nm irradiation; (d) after full-arc irradiation; (e) after annealing to 35 K; f−j reproduce the spectra of a−e except replacing Ge with Sn; k−o reproduce the spectra of a−e except replacing Ge with Pb.

presented. Complementary experiments were also carried out with isotopologues for product identification. Common species, such as MSx (x = 1−2), MHy (y = 1, 2, 4) and trace amount of oxides have been identified in previous papers.24−29 The new products bands in this paper are listed in Table 1 and Table S1 in the Supporting Information. Infrared Spectra. The infrared spectra of laser-ablated Si atom reactions with hydrogen sulfide prediluted in argon are illustrated in Figure 1. A weak band at 1960.4 cm−1 in the Si− H stretching vibration region was observed on initial sample

deposition which enhanced significantly on annealing to 20 K but completely disappeared on 300 < λ < 780 nm irradiation. After this irradiation treatment, the group bands at 2167.1, 2153.4, and 986.0 cm−1 appeared which decreased by about two-thirds on the broadband irradiation, contrasting sharply with the eminent growth of the absorptions due to SiS and SiS2.24 On final annealing to 35 K, the band at 1960.4 cm−1 restored partly, and the silicon hydrides SiH, SiH2 and even SiH4 were observed.25When germanium, tin and lead targets were employed instead (Figures 2, 3, and 4), weak profiles at C

DOI: 10.1021/acs.jpca.8b04428 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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Figure 4. Infrared spectra of the M (M = Ge, Sn, Pb) atom and D2S reaction products in solid argon at 4 K. (a) Ge + 0.2% D2S deposition for 60 min; (b) after annealing to 20 K; (c) after 300 < λ < 780 nm irradiation; (d) after full-arc irradiation; (e) after annealing to 35 K; f−j reproduce the spectra of a−e except replacing Ge with Sn; k−o reproduce the spectra of a−e except replacing Ge with Pb.

Figure 5. Infrared spectra of the M (M = Ge, Sn, Pb) atom and H2S reaction products in solid argon at 4 K. (a) M + 0.2% H2S deposition for 60 min; (b) after annealing to 20 K; (c) after 300 < λ < 780 nm irradiation; (d) after full-arc irradiation; (e) after annealing to 35 K; f−j reproduce the spectra of a−e except replacing H2S with H234S; k−o reproduce the spectra of a−e except replacing 0.2% H2S with 0.4% (H2S + H234S) mixture.

1823.1 cm−1 (site at 1816.5 cm−1), 1653.0 cm−1 and 1538.1 cm−1 (site at 1525.2 cm−1) in the M-H (M = Ge, Sn, Pb) stretching vibration region were observed, respectively. Different with the counterpart band in the silicon spectra, little changes were observed for these bands on annealing, however, drastic variations were observed on photolysis. Similarly, the bands due to MSx (x = 1−2),26,27 and MHy (y = 1, 2),28,29 were produced (Figure 5).

Calculations. Considering the characteristic distribution of the product bands (M-H stretching and H-M-H bending vibration region), the exploration for new species was carried out on the M inserted product HMSH with both the cis- and trans- conformation. Also, the H2MS molecules affording HM-H bending vibrational modes are immediately come into mind. In view of the MS species in our spectra, the dissociative products MS + H2 were optimized as well. Figure 6 illustrates D

DOI: 10.1021/acs.jpca.8b04428 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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Figure 6. Optimized structures for cis-HMSH, trans-HMSH, and H2MS (M = Si, Ge, Sn, Pb) molecules based on CCSD(T) (bold values) and B3LYP (bond lengths in Angstroms, and bond angles in degrees).

our B3LYP calculation (Tables 1 and S2). Since the rest of the bands of this molecule are at least five times less in intensity than the Si−H fundamental based on our frequency calculation, it is hard to observe these modes experimentally. Figure 2 illustrates the reactions for M + H2S (M = Ge, Sn, Pb). Similar to the Si−H stretching mode of HSiSH, the M−H stretching modes of HMSH molecules were observed at 1823.1 (HGeSH), 1653.0 (HSnSH), and 1538.1 cm−1 (HPbSH) on initial sample deposition but maintained a constant absorbance on annealing and nearly disappeared on stepwise photolysis. In the following experiments with H234S sample (Figure 3), no shifts were observed for those bands, which parallel exactly what the calculation predicts for the M−H stretching vibrational mode of a HMSH molecule. The absorptions due to M−D stretching modes of the DMSD molecules were observed at 1315.0 (DGeSD), 1188.1 (DSnSD), and 1103.5 cm−1 (DPbSD), defining H/D isotopic ratios of 1.386, 1.391, and 1.394, respectively. DFT calculations are in agreement with our experiments. With the B3LYP functional the M−H stretching mode of the HMSH molecule is predicted at 1890.8 (HGeSH), 1660.7 (HSnSH), and 1579.4 cm−1 (HPbSH), which is overestimated by 3.7%, 0.5%, and 2.7%, respectively. With deuterium substitution the calculated H/D isotopic ratio of the M−D stretching mode is 1.0404, 1.0408, and 1.0410, respectively, reproducing our experimental observations very well. Hence, the HMSH intermediates were effectively trapped in the low-temperature matrices. For a full list of the computed infrared active modes of these molecules see Tables S3 and S4 in the Supporting Information. From these tables it is clear that the strongest IR intensity is predicted for the M−H stretching mode of the HMSH (M = Ge, Sn, Pb) molecule. Besides, the

the converged structures with CCSD(T) as well as the B3LYP functional. In general, the trans-HMSH molecule is thermodynamically more favorable than the cis-HMSH by about 2.0 kcal/mol. Notice the dissociative product MS + H2 is energetically more preferred for Si or Ge. Interestingly, the H2MS is the least stable species except H2SiS that is the most stable on Si + H2S potential energy surfaces. In addition, it is worth noting that the ground states for the above-mentioned low-lying isomers are all singlets. Assignments: HMSH (M = Si, Ge, Sn, Pb). Typical IR spectra of reactions of Si atom with H2S in excess argon are illustrated in Figure 1. It is clear that the SiS (739.1 cm−1) band dominated our spectra on initial sample deposition. Subsequent annealing to 20 K had less effect on the SiS absorption than the weak band at 1960.4 cm−1, which increased by almost 3-fold. Since this new absorption gave no shifts with 34S-enriched sample (Figure 1, middle trace), the involvement of the sulfur atom in this vibrational mode can be ruled out. Besides, notice its location in between the SiH (1953.4 cm−1) and SiH2 (ν3 1976.2 cm−1, site at 1972.8 cm−1) fundamentals;25 this peak is probably due to Si−H stretching vibration. Interestingly, the computed frequency for the Si−H stretching vibration of a HSiSH molecule (cis 2035.3 cm−1; trans 2038.1 cm−1) is in the intermediate region of SiH (calcd 2017.7 cm−1) and SiH2 (calcd 2041.3 cm−1), which matches our experimental observation very well. In the following experiment, the Si−D stretching frequency of the DSiSD molecule was observed at 1428.5 cm−1 with a 1.372 H/D isotopic ratio, which is very close to our calculations (1.390). In addition, it is worth noting that the Si−H stretching mode of the HSiSH molecule is the most prominent band based on E

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Figure 7. PES for the formation of cis-HSiSH molecule in the reaction of Si with H2S.

patterns with H2S/H234S mixture (Figure 1, middle trace), as well as no shifts with H2S/HDS/D2S reagent (Figure 1, upper trace). As for the MS (M = Ge, Sn, Pb) species (Figure 5), their absorptions at 571.7, 569.2, and 566.8 cm−1 (70Ge32S, 72 Ge32S, and 74Ge32S)26 and 480.5 cm−1 (SnS)27 were prominent except PbS,27 for which there is a sharp decrease of the ratio of signal-to-noise. The spectroscopic feature for Pb34S (marked by arrows) might be the weakest, which was barely resolved in our spectra. In addition, no bands were detected for MS2 (M = Sn, Pb) species,26,27 except GeS2 at 661.8, 657.5, and 653.3 cm−1. It should be noted that the most stable MS2 species for Si and Ge is the linear-SMS as what we observed here; however, those for Sn and Pb are cyc-MS2.32 Notice their computed infrared active modes are slightly higher than 400 cm−1 (cyc-SnS2:468.7 cm−1, cyc-PbS2:457.8 cm−1), and the corresponding intensities are very weak (cyc-SnS2:6.0 km mol−1, cyc-PbS2:5.0 km mol−1), suggesting it is very difficult to detect these species in our experiments. Reaction Mechanisms. Since all of these species have singlet ground states, the ground state PES should be singlet accordingly. To obtain an overall profile of the reaction, initial complexes like M−H2S molecules were investigated for which the triplet states are energetically more favorable. It seems that the entrance channel of the S−H bond activation involves the spin crossover between the singlet and the triplet potential energy surfaces. Figure 7 illustrates the initial stage of the reaction of Si with H2S; it is clear that the spin crossing directs this reaction to proceed through an alternative energy surface to produce singlet HSiSH, reducing the total energy by 63.6 kcal/mol, and this barrierless reaction is also consistent with its production on annealing. Similar behavior had also been observed for dehydrogenation of H2S on Si(100) at low temperature.33,34 In contrast, the HMSH molecules (M = Ge, Sn, Pb) with noticeable barriers (Figure 8) in the reaction path cannot be produced in this same procedure. However, ground state atoms with high translational energy as well as a small proportion of excited atoms can be produced in the laserablation process,35,36 which can trigger the insertion reaction.

dominance of the M−H band increases from Si to Pb, agreeing with the absence of the observation of more vibrational bands of those molecules. H2SiS. A group of bands at 2167.1, 2153.4, and 986.0 cm−1 tracked together in the remaining procedures, which might belong to different vibrational modes for one molecule. In the following experiment with H2S/H234S sample, none of these bands exhibited sulfur-34 dependence. On the contrary, triplet splitting patterns were observed for all three bands with a H2S/ HDS/D2S mixture (Figure 1, upper trace), suggesting the participation of two equivalent hydrogen atoms in each vibrational mode. We observed that the growth of these bands is at the expense of the HSiSH molecule, so one plausible product will be H2SiS, the isomer of HSiSH, which is a C2v planar molecule with exactly two equivalent hydrogen atoms. Even more persuading facts can be inferred from Table 1, for example, the band positions for three major absorptions, which were predicted at 2230.1, 2216.9, and 1012.9 cm−1 and are in agreement with the above-mentioned observations. In addition, the computed H/D isotopic ratios (1.382, 1.397, and 1.312) also reproduce our observations (1.379, 1.403, and 1.294). Overall, the agreement between the observed and the computed spectra for the H2SiS molecule is excellent, and it substantiates this assignment. Interestingly, the rotational spectra of silanethione had been detected in the centimeter band,30,31 and the geometrical parameters optimized using coupled-cluster (CC) techniques with correlation-consistent polarized valence and polarized core−valence basis sets are comparable to the current study. The calculated frequencies for the H2MS (M = Ge, Sn, Pb) molecules are listed in Table S5 (Supporting Information); however, no bands were observed for those molecules. Sulfides. The absorptions for silanethione, H2SiS, dramatically decreased on broadband irradiation, while steady band growth was observed for a diatomic molecule SiS at 739.1 cm−1. Also, the band due to SiS2 at 918.0 cm−1 appeared in this same treatment. Species like SiS and SiS2 had been reported previously,24 and the existence of both of the two molecules can be substantiated by their doublet and triplet splitting F

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Since SiS + H2 and silanethione are more stable than the insertion product HSiSH by 4.3 and 13.5(cis) /1.7 and 10.9 (trans) kcal/mol based on the CCSD(T) calculations. It is likely that these species can be accessed by irradiation, which have been confirmed in our experiments. Figure 9 illustrates the ground state PES of HSiSH isomerization; it is clear that both of the reaction barriers of the rate determination step for HSiSH → SiS + H2 decomposition (32.0 kcal/mol) and HSiSH → H2SiS isomerization (43.7 kcal/mol) are unreachable by annealing at a low-temperature range, which is in accord with our observations of the photoinduced reactions. Similar conclusions can also be drawn for the rest of the elements in this group (Ge, Sn, Pb) when referring to Figure 10. It is also clear that the H2SiS molecule is the most stable species in the Si + H2S reaction (Figure 10). However, the situation changed when Si is replaced by M (M = Ge, Sn, Pb), and the H2MS molecule became the least stable species among selected isomers. Besides, the stability of H2MS molecule decreases from silicon to lead, defining an increasing energyconsumption step for its production. Thus, the absence of H2MS species (M = Ge, Sn, Pb) even on irradiation is reasonable in our experiments. Interestingly, SiS can be generated when H2S is passed over heated Si (Wacker).24 In our experiment it seems that the M + H2S reaction can be very effectively quenched after the primary reaction (M + H2S → HMSH), and the energy-rich intermediates HMSH, which is fragment readily in the gas phase, can be stabilized in solid matrices.37 Hence, the H2 elimination reaction can be best described as M + H2S → HMSH → MS + H2(M = Si, Ge, Sn, Pb). Interestingly still, the reaction M + H2S → MS + H2 resembles the water gas reaction38 C + H2O → CO + H2 in a way of elements substitution. Since the latter reaction inspires numerous studies in methanol,39 dimethyl ether (DME),40 and Fischer−Tropsch

Figure 8. PES for the formation of cis-HMSH molecule in the reaction of M (M = Ge, Sn, Pb) with H2S.

Figure 9. Ground state (singlet-state) PES for the isomerization reaction of the cis-HSiSH molecule. G

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Figure 10. Comaprison for the ground state PES for the isomerization reaction of the cis-HMSH (M = Si, Ge, Sn, Pb) molecule (the most stable species are marked by arrows).

Figure 11. Wiberg bond index and natural population (bold values in parentheses) of H2S, HSiSH, and H2SiS molecules based on NBO analysis.

synthesis,41 the former reaction, especially the reaction of H2S with earth-abundant Si, will be of fundamental value in the chemistry of S−H bond activation and efficient transformation. Bonding Considerations. The carbon atom has a great tendency to induce H2 elimination from water and CO with a robust bond being formed. Similarly, the reaction Si + H2S → SiS + H2 is likely to occur thermodynamically, and the bond energy of the diatomic SiS molecule is up to 615.8 kJ/mol.24 Notice sulfur and silicon are among the least elements in interstellar space, while their combination SiS is extraordinarily abundant.42,43 Figure 11 compares the Wiberg bond index and natural population of H2S, HSiSH, and H2SiS molecules based on natural bond orbital (NBO) analysis;44 the bond orders of these species are straightforward from the Wiberg bond index, and it is of particular interest to note that protonic Hδ+ and hydridic Hδ− coexist in the HSiSH intermediate, contrasting sharply with the hydrogens in H2S and H2SiS. Similar results are also obtained for HMSH (M = Ge, Sn, Pb) intermediate

(Figure S1 in the Supporting Information). A well-known analogy bearing such like hydrogens is NH3BH3, and a common salient feature of these molecules is the facile release of H2 under mild conditions.45,46 However, different with NH3BH3, the currently identified HMSH is a reactive intermediate with excess energy that can be utilized further in H2 elimination, in which two oppositely charged hydrogens of HMSH will approach each other, weakening the bonds between M−H and S−H while strengthening the bond between M−S (Figures 9 and 10). Obviously, the transition state formed with bonding H−H and M−S is much stabilized, and this is also consistent with the fact that the most optimal reaction path of HMSH isomerization is H2 elimination.



CONCLUSION The current study reveals that when employing group 14 elements as reagents the M atom (M = Si, Ge, Sn, Pb) can insert into the S−H bond to form HMSH molecules. However, H

DOI: 10.1021/acs.jpca.8b04428 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry A

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these molecules are not stable. They can decompose to MS + H2 on stepwise irradiations. Besides, the HSiSH molecule can either decompose to SiS + H2 or isomerize to H2SiS on 300 < λ < 780 nm irradiation. In contradiction with previous theoretical studies,13,14 the silanethione produced at this stage decomposed to SiS + H2 on the following broadband irradiation. Overall, the H2 elimination reaction from H2S in low-temperature matrices can be triggered effectively by irradiation with the participation of group 14 atoms.



ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpca.8b04428. Infrared absorptions observed for the new products of the reactions of Si, Ge, Sn, Pb atoms and isotopic H2S molecules; calculated frequencies of the low-lying isomers of Si + H2S; summary of the calculated frequencies of cis-HMSH (1A′), trans-HMSH (1A′), and H2MS (1A1) molecules (M = Ge, Sn, Pb); comparison of the Wiberg bond index and natural population of HMSH and H2MS (M = Ge, Sn, Pb) molecules based on NBO analysis (PDF)



AUTHOR INFORMATION

Corresponding Authors

*Phone: +86-23-68254602. E-mail: [email protected]. *Phone: +86-21-65980301. E-mail: [email protected]. ORCID

Xing Liu: 0000-0002-7285-2515 Xuefeng Wang: 0000-0001-6588-997X Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS This work was supported by Frontier and Applied Basic Research of Chongqing (Grant No. cstc2018jcyjAX0191), Fundamental Research Funds for the Central Universities (Grant Nos. SWU115072 and XDJK2016C030), and the National Natural Science Foundation of China (Grant No. 21373152).



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DOI: 10.1021/acs.jpca.8b04428 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.jpca.8b04428 J. Phys. Chem. A XXXX, XXX, XXX−XXX