X-ray Crystal Structures of α-KrF<sub>2</sub>, [KrF][MF<sub>6</sub>] (M = As, Sb, Bi), [Kr<sub>2</sub>F<sub>3</sub>][SbF<sub>6</sub>]·KrF<sub>2</sub>, [Kr<sub>2</sub>F<sub>3</sub>]<sub>2</sub>[SbF<sub>6</sub>]<sub>2</sub>·KrF<sub>2</sub>, and [Kr<sub>2</sub>F<sub>3</sub>][AsF<sub>6</sub>]·[KrF][AsF<sub>6</sub>]; Synthesis and Characterization of [Kr<sub>2</sub>F<sub>3</sub>][PF<sub>6</sub>]·<i>n</i>KrF<sub>2</sub>; and Theoretical Studies of KrF<sub>2</sub>, KrF<sup>+</sup>, Kr<sub>2</sub>F<sub>3</sub><sup>+</sup>, and the [KrF][MF<sub>6</sub>] (M = P, As, Sb, Bi) Ion Pairs
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Bibliographic record
Abstract
The crystal structures of alpha-KrF(2) and salts containing the KrF(+) and Kr(2)F(3)(+) cations have been investigated for the first time using low-temperature single-crystal X-ray diffraction. The low-temperature alpha-phase of KrF(2) crystallizes in the tetragonal space group I4/mmm with a = 4.1790(6) A, c = 6.489(1) A, Z = 2, V = 113.32(3) A(3), R(1) = 0.0231, and wR(2) = 0.0534 at -125 degrees C. The [KrF][MF(6)] (M = As, Sb, Bi) salts are isomorphous and isostructural and crystallize in the monoclinic space group P2(1)/c with Z = 4. The unit cell parameters are as follows: beta-[KrF][AsF(6)], a = 5.1753(2) A, b = 10.2019(7) A, c = 10.5763(8) A, beta = 95.298(2) degrees, V = 556.02(6) A(3), R(1) = 0.0265, and wR(2) = 0.0652 at -120 degrees C; [KrF][SbF(6)], a = 5.2922(6) A, b = 10.444(1) A, c = 10.796(1) A, beta = 94.693(4) degrees, V = 594.73(1) A(3), R(1) = 0.0266, wR(2) = 0.0526 at -113 degrees C; [KrF][BiF(6)], a = 5.336(1) A, b = 10.513(2) A, c = 11.046(2) A, beta = 94.79(3) degrees, V = 617.6(2) A(3), R(1) = 0.0344, and wR(2) = 0.0912 at -130 degrees C. The Kr(2)F(3)(+) cation was investigated in [Kr(2)F(3)][SbF(6)].KrF(2), [Kr(2)F(3)](2)[SbF(6)](2).KrF(2), and [Kr(2)F(3)][AsF(6)].[KrF][AsF(6)]. [Kr(2)F(3)](2)[SbF(6)](2).KrF(2) crystallizes in the monoclinic P2(1)/c space group with Z = 4 and a = 8.042(2) A, b = 30.815(6) A, c = 8.137(2) A, beta = 111.945(2) degrees, V = 1870.1(7) A(3), R(1) = 0.0376, and wR(2) = 0.0742 at -125 degrees C. [Kr(2)F(3)][SbF(6)].KrF(2) crystallizes in the triclinic P1 space group with Z = 2 and a = 8.032(3) A, b = 8.559(4) A, c = 8.948(4) A, alpha = 69.659(9) degrees, beta = 63.75(1) degrees, gamma = 82.60(1) degrees, V = 517.1(4) A(3), R(1) = 0.0402, and wR(2) = 0.1039 at -113 degrees C. [Kr(2)F(3)][AsF(6)].[KrF][AsF(6)] crystallizes in the monoclinic space group P2(1)/c with Z = 4 and a = 6.247(1) A, b = 24.705(4) A, c = 8.8616(6) A, beta = 90.304(6) degrees, V = 1367.6(3) A(3), R(1) = 0.0471 and wR(2) = 0.0958 at -120 degrees C. The terminal Kr-F bond lengths of KrF(+) and Kr(2)F(3)(+) are very similar, exhibiting no crystallographically significant variation in the structures investigated (range, 1.765(3)-1.774(6) A and 1.780(7)-1.805(5) A, respectively). The Kr-F bridge bond lengths are significantly longer, with values ranging from 2.089(6) to 2.140(3) A in the KrF(+) salts and from 2.027(5) to 2.065(4) A in the Kr(2)F(3)(+) salts. The Kr-F bond lengths of KrF(2) in [Kr(2)F(3)][SbF(6)].KrF(2) and [Kr(2)F(3)](2)[SbF(6)](2).KrF(2) range from 1.868(4) to 1.888(4) A and are similar to those observed in alpha-KrF(2) (1.894(5) A). The synthesis and Raman spectrum of the new salt, [Kr(2)F(3)][PF(6)].nKrF(2), are also reported. Electron structure calculations at the Hartree-Fock and local density-functional theory levels were used to calculate the gas-phase geometries, charges, Mayer bond orders, and Mayer valencies of KrF(+), KrF(2), Kr(2)F(3)(+), and the ion pairs, [KrF][MF(6)] (M = P, As, Sb, Bi), and to assign their experimental vibrational frequencies.
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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 | 0.034 | 0.023 |
| Meta-epidemiology (narrow) | 0.059 | 0.066 |
| Meta-epidemiology (broad) | 0.054 | 0.028 |
| Bibliometrics | 0.025 | 0.046 |
| Science and technology studies | 0.026 | 0.044 |
| Scholarly communication | 0.018 | 0.025 |
| Open science | 0.036 | 0.031 |
| Research integrity | 0.044 | 0.053 |
| Insufficient payload (model declined to judge) | 0.001 | 0.008 |
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