Preparation, X-ray Crystal Structure Determination, Lattice Potential Energy, and Energetics of Formation of the Salt S<sub>4</sub>(AsF<sub>6</sub>)<sub>2</sub>·AsF<sub>3</sub>Containing the Lattice-Stabilized Tetrasulfur [2+] Cation. Implications for the Understanding of the Stability of M<sub>4</sub><sup>2+</sup>and M<sub>2</sub><sup>+</sup>(M = S, Se, and Te) Crystalline Salts
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Bibliographic record
Abstract
S4(AsF6)2.AsF3 was prepared by the reaction of sulfur with arsenic pentafluroide in liquid AsF3 (quantitatively) and in anhydrous HF in the presence of trace amounts of bromine. A single-crystal X-ray structure of the compound has been determined: monoclinic, space group P2(1)/c, Z = 4, a = 7.886(1) A, b = 9.261(2) A, c = 19.191(3) A, beta = 92.82(1) degrees, V = 1399.9(4) A3, T = 293 K, R1 = 0.052 for 1563 reflections (I > 2 sigma (I) 1580 total and 235 parameters). We report a term-by-term calculation of the lattice potential energy of this salt and also use our generalized equation, which estimates lattice energies to assist in probing the homopolyatomic cation thermochemistry in the solid and the gaseous states. We find S4(AsF6)2.AsF3 to be more stable (delta fH degree [S4(AsF6)2.AsF3,c] approximately -4050 +/- 105 kJ/mol) than either the unsolvated S4(AsF6)2 (delta fH degree [S4(AsF6)2,c] approximately -3104 +/- 117 kJ/mol) by 144 kJ/mol or two moles of S2AsF6 (c) and AsF3 (1) by 362 kJ/mol. The greater stability of the S(4)2+ salt arises because of the greater lattice potential energy of the 1:2 solvated salt (1734 kJ/mol) relative to twice that of the 1:1 salt (2 x 541 = 1082 kJ/mol). The relative lattice stabilization enthalpies of M(4)2+ ions relative to two M2+ ions (i.e., in M4(AsF6)2 (c) with respect to two M2AsF6 (c) (M = S, Se, and Te)) are found to be 218, 289, and 365 kJ/mol, respectively. Evaluation of the thermodynamic data implies that appropriate presently available anions are unlikely to stabilize M2+ in the solid phase. A revised value for delta fH degree [Se4(AsF6)2,c] = -3182 +/- 106 kJ/mol is proposed based on estimates of the lattice energy of Se4(AsF6)2 (c) and a previously calculated gasphase dimerization energy of 2Se2+ to Se(4)2+.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it