www.sciencemag.org/cgi/content/full/331/6023/1426/DC1
Supporting Online Material for Regeneration of Ammonia Borane Spent Fuel by Direct Reaction with Hydrazine and Liquid Ammonia Andrew D. Sutton,* Anthony K. Burrell, David A. Dixon, Edward B. Garner III, John C. Gordon,* Tessui Nakagawa, Kevin C. Ott, J. Pierce Robinson, Monica Vasiliu
*To whom correspondence should be addressed. E-mail:
[email protected] (J.C.G.);
[email protected] (A.D.S.) Published 18 March 2011, Science 331, 1426 (2011) DOI: 10.1126/science.1199003
This PDF file includes: Materials and Methods Figs. S1 to S5 Tables S1 to S4 References
Supporting Online Material
Materials and Methods. General Experimental. Hydrazine borane was prepared by mixing a 1:1 ratio of BH3.THF and hydrazine in THF and the volatiles removed in vacuo to yield a white solid. Methylamine borane and hydrazine were purchased from Aldrich Chemical Company and used as received. Dehydrocoupling of borazine (~ 25 mL, Gelest) was performed at ambient temperature in a sealed steel container over several months. Once no liquid (i.e. borazine) remained, the solid was extracted with THF and volatiles removed in vacuo to provide the PB for these studies. 11B NMR spectroscopy (Figure S1) and diffuse-reflectance infrared spectroscopy (Figure S2) verified that this material is analogous to that described in published routes for PB synthesis from borazine (S1, S2 11
B NMR: (THF) δ 31 ppm (s, vbr); IR: 3445 (m), 3230 (br, m), 2505 (m), 1450 (br, s),
1200 (m), 900 (m), 750 (m), 690 (m) cm-1) and used in previous AB regeneration studies (S3). It should be noted that the minor impurities corresponding to resonances at ~ 0 and 13 ppm account for < 1 % of the material (also the boron background from the borosilicate glass NMR tubes and spectrometer probe account for the broad resonance below 0 ppm). 1H, 11B (128 MHz or 96 MHz) NMR spectra were recorded at room temperature on a Bruker AVANCE 400 MHz spectrometer or a Bruker AVANCE 300 MHz spectrometer. 1H spectra were referenced to the residual protons in the solvent and 11
B NMR chemical shifts were referenced to BF3-etherate. Infrared spectra were
recorded using a Thermo-Nicolet Avatar 360 FT-IR with Smart Durasample IIR accessory.
Figure S1. 11B{1H} NMR spectrum of PB used in this study in THF.
Figure S2. Diffuse-reflectance infrared spectrum of PB.
Dissolution of AB in hydrazine. AB (100 mg) was placed in an NMR tube and hydrazine added (0.5 mL). The tube was transferred to the NMR spectrometer with the probe heated to the desired temperature (25, 40 or 60 oC) and spectra recorded at regular intervals for a period of 12 hours.
Solution reaction of PB with hydrazine. PB (100 mg) was dissolved in THF (5 mL) in a stirred vial. Stoichiometric amounts of hydrazine were added (1-20 molar equivalents) and the solution stirred for up to 12 hours. The reaction solution was analyzed was analyzed by 11B NMR spectroscopy. Typically hydrazine borane was the predominant BH3 containing species (70-100 %) with AB as the minor product. In solution, greater
than 3 equivalents of hydrazine per BNH were required to see complete removal of PB resonances.
Conversion of HzB to AB. Hydrazine borane (13 mg, 0.28 mmol) was suspended in liquid ammonia (30mL) at -77 oC in a stainless steel reaction vessel with an internal volume of 75 mL. The reaction vessel was sealed and heated to 60 oC. After 24 hours the vessel was cooled to -77 oC and opened. The ammonia solution was poured into an open beaker from which the ammonia was allowed to evaporate yielding a white solid. After removal of excess ammonia, the resultant solid was confirmed as ammonia borane by 11B NMR (95 % ammonia borane, 5 % hydrazine borane), no other boron containing species were detected. 1H NMR (THF): 3.9 (b, 3 H, -NH), 1.4 (q, 3H, BH). 11B NMR (THF, BF3-etherate): -23.95 (q, JBH 94 Hz).
Regeneration of AB from PB. Polyborazylene (100 mg, 3.7 mmol “BNH”) was suspended in liquid ammonia (30mL) at -77 oC in a stainless steel reaction vessel with an internal volume of 75 mL. Hydrazine (150 mg, 4.7 mmol) was added by syringe. The reaction vessel was sealed and heated to 40 oC. After 24 hours the vessel was cooled to 77 oC and opened. The ammonia solution was poured into a Schlenk flask and immediately placed under vacuum to remove any trace hydrazine. This procedure afforded a solid white powder identified as ammonia borane (0.105 g, 92 % yield). 1H NMR (THF): 3.9 (b, 3 H, -NH), 1.4 (q, 3H, BH). 11B NMR (THF, BF3-etherate): -23.90 (q, JBH 94 Hz). DSC also confirmed the identity and purity of the sample (23).
Figure S3. 11B NMR spectrum in THF for crude material isolated from one-pot PB/N2H4/NH3 reaction after heating at 40 oC for 24 hours resulting in HzB (8 %) and AB (92 %).
Heat Flow (Arb. units)
AB generated from PB
neat AB
50
100
150
200
Temperature (°C) Figure S4. DSC of AB generated from PB and a commercial sample of AB (heating rate: 1 oC min -1) Theoretical/Computational Details We hypothesized that an initial Lewis base exchange followed by ammoniation might provide a more energetically efficient route to the desired product. High level electronic structure calculations at the G3MP2 correlated molecular orbital theory level were used to predict the B-N bond dissociation energies (BDEs) for different amines relative to hydrazine (N2H4, Hz) to determine which bases can displace Hz.. The results of these calculations are provided in Tables S1-S3. We first benchmarked the G3MP2 composite correlated molecular method (S4) and density functional theory (DFT) with the B3LYP exchange-correlation functional (S5, S6) and the DZVP2 basis set (S7) against coupled cluster theory at the CCSD(T) level (S8) with extrapolation to the complete basis set (CBS) limit (S9) using the augmented correlation-consistent basis sets (S10) for the simplest B-N bonds for BH3 binding to NH3 and N2H4. The CCSD(T)/CBS
values were corrected for core-valence corrections (S11, S12) relativistic effects, (S13-16) and zero point energies following procedures previously developed by us (S17-S19) The DFT and G3MP2 calculations were done with the Gaussian program system (S20). The CCSD(T)/CBS calculations were done with the Molpro program system (S21). The benchmark values are shown in Table S1. The G3MP2 values show better agreement with the benchmark CCSD(T)/CBS values for the absolute bond energies than do the DFT values. In the gas phase, the B-N BDE for BH3NH2NH2 is about 5 kcal/mol larger than that of BH3NH3. Thus NH3 will not readily displace N2H4 in the gas phase from BH3NH2NH2.
Table S1. Calibration of methods for the B-N BDE in BH3-NH2NH2 and BH3-NH3 in kcal/mol
BDE
CCSD(T)/CBS
B3LYP/DZVP2
G3MP2
0K
298K
0K
298K
0K
298K
BH3-NH2NH2
31.0
32.2
28.2
29.6
32.2
33.6
BH3-NH3
26.1
27.7
23.4
25.2
26.0
27.7
Table S2 shows all of the different amines (molecular diagrams below) whose energies were predicted to study the exchange process. The dative bond dissociation energies (BDEs) relative to that of BH3NH2NH2 are given as are the estimated total dative bond dissociation energies based on the CCSD(T)/CBS value for BH3NH2NH2 and the DFT and G3MP2 relative dative BDEs. We based our analysis on the G3MP2 values
which are probably good to about 1.5 kcal/mol. The B3LYP B-N BDEs are within a couple of kcal/mol for all compounds except for the tri-substituted amines where they are about 5 to 6 kcal/mol too strongly bonded as compared to the G3MP2 values. It is thus likely that the (C8H18)3N-BH3 BDE at the B3LYP level is overbound by about 5 kcal/mol. These types of issue have been noted before for B-N bonds (S22, S23) as well as issues with errors at the B3LYP level growing with the size of the molecule (S24).
Table S2. Hz-BH3+Amine → R-BH3+Hz (Hz = hydrazine) relative reaction energies and absolute BDEs in kcal/mol. Absolute BDEs obtained relative to CCSD(T) values for BH3NH2NH2 given above
Amine
B3LYP BDE
G3MP2 BDE
absolute
absolute
relative to
relative to
B3LYP
G3MP2
CCSD(T)
CCSD(T)
ΔΔH(rel BDE)
ΔΔH(Rel BDE)
NH2NH2
NH2NH2
0K
298K
0K
298K
0K
298K
0K
298K
NH2(CH2)2NH2
0.6
0.7
0.6
0.8
31.6
32.9
31.6
33.0
NH2(CH2)2NH2BH3
3.1
3.3
3.0
3.3
34.1
35.5
34.0
35.5
1,2-NH2 cyclohexane
-2.9
-2.9
-2.7
-2.5
28.1
29.3
28.3
29.7
cyclohexane
3.8
3.7
2.6
2.7
34.8
35.9
33.6
34.9
1,3-NH2 cyclohexane
0.6
0.9
0.4
0.7
31.6
33.1
31.4
32.9
1,2-NH2BH3
1,3-NH2BH3 cyclohexane
2.7
2.9
2.3
2.6
33.7
35.1
33.3
34.8
1,4-NH2 cyclohexane
2.0
2.1
1.5
1.8
33.0
34.3
32.5
33.9
cyclohexane
2.3
2.6
2.0
2.2
33.3
34.8
33.0
34.4
2,6-luthidine
3.4
3.4
2.8
2.8
34.4
35.6
33.8
35.0
cyclohexane
3.4
3.6
0.7
1.0
34.4
35.8
31.7
33.2
4-diMeAminoPy
1.2
1.2
0.4
0.5
32.2
33.4
31.4
32.7
Ph-NH2
8.0
8.2
7.0
7.3
39.0
40.4
38.0
39.5
2.6.diMePhNH2
7.7
8.0
6.5
6.7
38.7
40.2
37.5
38.9
Et2PhN
7.0
6.9
1.7
1.7
38.0
39.1
32.7
33.9
Me2PhN
8.7
8.5
2.9
2.7
39.7
40.7
33.9
34.9
(C8H18)3N
3.0
2.9
-
-
34.0
35.1
-
-
allylNH2
0.4
0.5
0.3
0.5
31.4
32.7
31.3
32.7
Et3N
3.3
3.0
-1.9
-2.0
34.3
35.2
29.1
30.2
Et2NH
0.8
0.9
-1.5
-1.5
31.8
33.1
29.5
30.7
EtMeNH
-0.7
-0.6
-2.6
-2.5
30.4
31.6
28.4
29.7
Me3N
-0.9
-0.8
-4.4
-4.4
30.1
31.4
26.6
27.8
Me2NH
-1.6
-1.5
-3.3
-3.3
29.5
30.7
27.7
28.9
NH3
4.7
4.4
6.2
5.9
35.7
36.6
37.2
38.1
Me2S
9.4
9.8
7.8
8.3
40.4
42.0
38.8
40.5
Et2S
8.8
9.2
6.9
7.4
39.8
41.4
37.9
39.6
1,4-NH2BH3
2,6-diMe-N-
Ph2S
14.4
14.8
12.1
12.7
45.7
47.0
43.1
44.9
Me2O
14.5
14.7
13.4
13.8
45.5
46.9
44.4
46.0
Diagrams for molecules in Table S2.
1,2-NH2
1,2-NH2BH3
cyclohexane
cyclohexane
1,4-NH2
1,4-NH2BH3
cyclohexane
cyclohexane
4-diMeAminoPy
2.6.diMePhNH2
1,3-NH2 cyclohexane
1,3-NH2BH3 cyclohexane
2,6-lutidine
2,6-diMe-Ncyclohexane
Et2PhN
Me2PhN
Because the calculations show that Hz will not be displaced by NH3 in the gas phase, the reaction thermodynamics for the exchange reaction
BH3Hz + NH3 → BH3NH3 + Hz were calculated in three different solvents (ammonia (NH3), tetrahydrofuran (THF) and dioxane) at 298 K using a self consistent reaction field approach with the COSMO (Conductor-like Screening Model) parameterization as implemented in Gaussian and ADF (S20, S25). We reported the effect of the electrostatic component only as the nonbonded contributions are on the order of only 0.1 kcal/mol. The two implementations differ slightly but in both cases the free energy for the exchange reaction is substantially decreased in NH3 as a solvent. As the dipole moment of the solvent decreases, the free energies approach the gas phase value. Thus BH3NH3 is more stabilized in the polar solvents leading to a decrease in the free energy. Use of LeChatelier’s principle suggests that as N2H4 is removed, the overwhelming presence of NH3, due to it being the solvent, will further drive the reaction to the right. For a free energy change of 1 kcal/mol at 298 K, Keq = 0.2
Table S3. Exchange reaction energies in kcal/mol at 298 K Method
ΔHgas
ΔGgas
ΔGNH3
ΔGTHF
ΔGDioxane
ADF
4.5
4.5
1.0
1.5
3.1
Gaussian
4.5
4.5
1.9
2.2
3.2
The energies of the reactions 4 “BNH” + 5 N2H4 Æ 4 H3N-BH3 + 5 N2 and c-B3N3H6 + 3N2H4 → 3BH3NH3 + 3N2↑ were calculated as follows. The gas phase heats of formation of c-B3N3H6, BH3NH3, and N2H4 were taken from our previous work (S18, S22, S26). The heat of formation of N2 is 0 kcal/mol. The heat of formation of BNH is
taken as 1/12 ΔHf(c-B12N12H12) where the compound has the same structure as coronene. The gas phase ΔHf(c-B12N12H12) was calculated at the G3MP2 level. The heat of formation of solid BH3NH3 is taken from the literature. The heat of formation of solid cB3N3H6 was taken from a combination of the gas phase calculated value combined with the experimental heat of sublimation as outlined in reference S21. The heat of formation of solid c-B12N12H12 was taken by adding the heat of sublimation of coronene. (S27). The heats of formation are given in Table S4. Table S4. Heats of formation in kcal/mol at 298 K Molecule N2
ΔHgas(298K) ΔHsolid(298K) 0
N2H4
23.1
BH3NH3
-14.6
-36.7
B3N3H6
-118.5
-126.6
B12N12H12
-569.0
-606.0
In our initial attempt to further understand the mechanism of the conversion of PB to AB, the energies of the intermediates for the addition of N2H4 molecules to a reasonable model system i.e “BNH2” (borazine) were calculated at the G3MP2B3 level of theory (Figure S5). The initial mapping of the intermediates was done using density functional theory at the B3LYP/DZVP2 level with the G3MP2B3 level used to calculate higher accuracy reaction energies and heats of formation (ΔHf’s) of various species. The G3MP2B3 level was used because the initial geometry optimization in the G3MP2 procedure at the Hartree-Fock level does not always yield reasonable structures. The overall reaction sequence is complicated due to the presence of many reaction steps (well over a hundred reactions). Only one of ten 2nd addition products of trans-
B3N3H6(NH2)2 is shown in Figure S5 with the 3rd addition products limited to that from one intermediate structure. The initial step in the reaction is the addition of N2H4 to a boron atom. The weak N-N bond in coordinated hydrazine can be cleaved, and the released NH2 moiety can then bind to another boron atom either syn or anti. This transformation can directly lead to cleavage of a B-N bond within the “BNH2”units in the early stages of reaction. The addition of more N2H4 can lead to further B-N bond cleavages and the generation of BH(NH2), a potential intermediate which may provide a possible pathway for hydrogen transfer to reform BH3 units. The computational results indicate that the initial reactions are near thermoneutral but that subsequent reactions are exothermic.
B3N3H6
B3N5H10
+ N2H4
-0.6
B3N7H14
-1.2
0.3
+ N2H4
-52.8
-53.0
+ B3N7H14
B3N5H10
B3N7H14
B3N7H14
-22.1
+
+ -9.1
N2H4
B3N7H14
B3N7H14
-50.9
-20.9
-57.5 B3N9H18
B3N9H18
-22.9
+
-12.0
B3N9H18
0.5
B3N9H18
B3N9H18
Figure S5. Energies (ΔH298) in kcal/mol of one of the ten 2nd addition products of trans B3N3H6(NH2)2 and a limited set of 3rd addition products at the G3MP2B3 level.
Our initial calculations show that the addition of N2H4 to “BNH2” can lead to breaking the strong B-N bonds in the ring. This leads to the formation of species like BH(NH2)2 as well as to other nitrogen rich species. The structures that were calculated were not chosen except to place NH2 groups on the borons from cleavage of the N-N bond. This was done because the transfer of a hydride to a boron atom and a proton to an N atom as shown by the following reaction is substantially endothermic N2H4 + c-B3N3H6 → trans N2H2 + c-B3N3H8 by 53.0 kcal/mol in the gas phase using the best available values (S26, S28) (48.9 kcal/mol, G3MP2). The resulting structures are the result of geometry optimization which yielded the species with the N-N bonds and BH(NH2)2. The formation of N-N bonds is not surprising as there are already N-N bonds in the reactant hydrazine and as observed experimentally, BH3N2H4 is an important product. The formation of species like BH(NH2)2 show that it is relatively easy to rehydrogenate the nitrogen but it is more difficult to rehydrogenate the boron. The rehydrogenation of the boron will require transfer of a hydrogen from N2H4 (or possibly N2H2 formed in subsequent steps) to the
+
N2H4
boron and possibly to the adjacent nitrogen. We also investigated the transfer of “H+” to N and “N2H3-“ to B as shown below. This reaction enthalpy is positive, 8.9 kcal/mol, at the G3MP2 level. Thus the addition of two NH2 groups provides consistent thermodynamics to initiate the various reactive steps. Further studies are needed to investigate the rehydrogenation of the boron and the formation of the other product N2, possibly via N2H2 reactions. Diimide is known to hydrogenate C-C double and triple bonds in olefins and acetylenes, although not aromatic ones, so it is possible that it may be an important intermediate once the aromatic character of the c-B3N3H6 is removed.
Supporting References S1. P. J. Fazen, E. E. Remsen, J. S. Beck, P. J. Carroll, A. R. McGhie, L. G. Sneddon, Synthesis, properties and ceramic conversion reactions of polyborazylene. A high-yield polymeric precursor to boron nitride. Chem. Mater., 7, 1942-1956 (1995).
S2. P. J. Fazen, J. S. Beck, A. T. Lynch, E. E. Remsen, L. G. Sneddon, Thermally induced borazine dehydropolymerization reactions. Synthesis and ceramic conversion reactions of a new high-yield polymeric precursor to boron nitride. Chem. Mater., 2, 9697 (1990).
S3. B. L. Davis, D. A. Dixon, E. B. Garner, J. C. Gordon, M. H. Matus, F. H. Stephens, Efficient regeneration of partially spent ammonia borane fuel. Angew. Chem. 48, 68126816 (2009).
S4. L.A. Curtiss, P.C. Redfern, K. Raghavachari, V. Rassolov J. A. Pople, Range Separated Local Hybrids. J. Chem. Phys. 110, 4703 (1999).
S5. A. D. Becke, Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648 (1993).
S6. C. Lee, W. Yang, R. G. Parr, Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B 37, 785 (1998).
S7. N. Godbout, D. R. Salahub, J. Andzelm, E. Wimmer, Optimization of Gaussian-type basis sets for local spin density functional calculations. Part I. Boron through neon, optimization technique and validation. Can. J. Chem., 70, 560 (1992).
S8. R. J. Bartlett, M. Musial, Coupled-cluster theory in quantum chemistry. Rev. Mod. Phys. 79, 291 (2007).
S9. K. A. Peterson, D. E. Woon, T. H. Dunning, Jr. Benchmark calculations with correlated molecular wave functions. IV. The classical barrier height of the H+H2 Æ H2+H reaction. J. Chem. Phys. 100, 7410 (1994).
S10. R. A. Kendall, T. H. Dunning, Jr., R. J. Harrison, Electron affinities of the first-row atoms revisited. Systematic basis sets and wave functions. J. Chem. Phys. 96, 6796 (1992).
S11. D. E. Woon, T. H. Dunning, Jr., Gaussian basis sets for use in correlated molecular calculations. V. Core-valence basis sets for boron through neon. J. Chem. Phys. 103, 4572 (1995). S12. K. A. Peterson, T. H. Dunning, Jr. Accurate correlation consistent basis sets for the molecular core-valence correlation effects: The second row atoms Al-Ar, and the first row atoms B-Ne revisited. J. Chem. Phys 117, 10548 (2002). S13. M. Douglas, N. M Kroll, Quantum electrodynamical corrections to the fine structure of helium. Ann. Phys. 82, 89-155 (1974). S14. B. A. Hess, Applicability of the no-pair equation with free-particle projection operators to atomic and molecular structure calculations. Phys. Rev. A. 32, 756-763 (1985). S15. B. A. Hess, Relativistic electronic-structure calculations emplying a two-component no-pair formalism with external-field projection operators. Phys. Rev. A. 33, 3742-3748 (1986). S16. W. A. de Jong, R. J. Harrison, D. A. Dixon, Parallel Douglas-Kroll energy and gradients in NWChem : Estimating scalar relativistic effects using Douglass-Kroll contracted basis sets. J. Chem. Phys. 114, 48-54 (2001). S17. M. H. Matus, K. Anderson, D. M. Camaioni, S. T. Autrey, and D. A. Dixon, Reliable Predictions of the Thermochemistry of Boron-Nitrogen Hydrogen Storage Compounds: BxNxHy, x = 2, 3. J. Phys. Chem A., 111, 4411-4421 (2007) S18. D. A. Dixon, M. Gutowski, Thermodynamic Properties of Molecular Borane Amines and the [BH4-][NH4+] Salt for Chemical Hydrogen Storage Systems from Ab Initio Electronic Structure Theory. J. Phys. Chem. A, 109, 5129-5135 (2005)
S19. D. Feller, K.A. Peterson, D.A. Dixon, A survey of factors contributing to accurate theoretical predictions of atomization energies and molecular structures. J. Chem. Phys., 129 204015 (32 pages) (2008) S20. M. J. Frisch, G. W. T., H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuna, G. A. Voth P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowshi, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Revision C. 02, Gaussian, Inc., Wallingford, CT, 2004. S21. MOLPRO, version 2009.1, a package of ab initio programs,H.-J. Werner, P. J. Knowles, F. R. Manby, M. Schütz, P. Celani, G. Knizia, T. Korona, R. Lindh, A. Mitrushenkov, G. Rauhut, T. B. Adler, R. D. Amos, A. Bernhardsson, A. Berning, D. L. Cooper, M. J. O. Deegan, A. J. Dobbyn, F. Eckert, E. Goll, C. Hampel, A. Hesselmann, G. Hetzer, T. Hrenar, G. Jansen, C. Köppl, Y. Liu, A. W. Lloyd, R. A. Mata, A. J. May, S. J. McNicholas, W. Meyer, M. E. Mura, A. Nicklaß, P. Palmieri, K. Pflüger, R. Pitzer, M. Reiher, T. Shiozaki, H. Stoll, A. J. Stone, R. Tarroni, T. Thorsteinsson, M. Wang, A. Wolf, see http://www.molpro.net
S22. M. H. Matus, K. Anderson, D. M. Camaioni, S. T. Autrey, and D. A. Dixon, “Reliable Predictions of the Thermochemistry of Boron-Nitrogen Hydrogen Storage Compounds: BxNxHy, x = 2, 3,” J. Phys. Chem A., 111, 4411-4421 (2007).
S23. T. M. Gilbert, Tests of the MP2 model and various DFT models in predicting the structures and B-N bond dissociation energies of amine-boranes (X3C)mH3-mBN(CH3)nH3-n (X = H, F; m = 0-3; n = 0-3): Poor performance of the B3LYP approach for dative B-N bonds. J. Phys. Chem. A, 108, 2550-2554 (2004). S24. P.C. Redfern, P. Zapol, L. A. Curtiss, K. Raghavachari, Assessment of Gaussian-3 and Density Functional Theories for enthalpy of formation of C1-C16 alkanes. J. Phys. Chem. A, 104, 5850-5854 (2000). S25. Baerends, E. J.; Austchbach, J.; Berces, A.; Bickelhaupt, F. M.; Bo, C.; Boerrigter, P. M.; Cavallo, L.; Chong, D. P.; L., D.; Dickson, R. M.; Ellis, D. E.; van Faassen, M.; Fan, L.; Fischer, T. H.; Fonseca Guerra, C.; van Gisbergen, S. J. A.; Gotz, A. W.; Groeneveld, J. A.; Gritsenko, O. V.; Gruning, M.; Harris, F. E.; van den Hoek, P.; Jacob, C. R.; Jacobsen, H.; Jensen, L.; van Kessel, G.; Kootstra, F.; Krykunov, M. V.; van Lenthe, E.; McCormack, D. A.; Michalak, A.; Neugebauer, J.; Nicu, V. P.; Osinga, V. P.; Patchkovskii, S.; Philipsen, P. H. T.; Post, D.; Pye, C. C.; Ravenek, W.; Rodriguez, J. I.; Ros, P.; Schipper, P. R. T.; Schreckenbach, G.; Snijders, J. G.; Sola, M.; Swart, M.; Swerhone, D.; te Velde, G.; Vernooijs, P.; Versluis, L.; Visscher, L.; Visser, O.; Wang, F.; Wesolowski, T. A.; van Wezenbeek, E. M.; Wiesenekker, G.; Wolff, S. K.; Woo, T. K.; Yakovlev, A. L.; Ziegler, T., SCM, ADF2008.01, Amsterdam, The Netherlands, 2008. S26. M. H. Matus, A. J. Arduengo, III, and D. A. Dixon, The Heats of Formation of Diazene, Hydrazine, N2H3+, N2H5+, N2H, and N2H3 and the Methyl Derivatives, CH3NNH, CH3NNCH3, and CH3HNNHCH3. J. Phys. Chem. A, 110, 10116-10121 (2006)
S27. J. S. Chickos, P. Webb, G. Nichols, T. Kiyobayashi, P.-C. Cheng, L. Scott, The enthalpy of vaporization and sublimation of corannulene, coronene, and perylene at T = 298.15 K. J. Chem. Thermodynamics, 34, 1195–1206 (2002).
S28. M. H. Matus, K. Anderson, D. M. Camaioni, S. T. Autrey, and D. A. Dixon, “Reliable Predictions of the Thermochemistry of Boron-Nitrogen Hydrogen Storage Compounds: BxNxHy, x = 2, 3,” J. Phys. Chem A., 111, 4411-4421 (2007).
