The Synthesis, Vibrational Spectra, and Molecular Structure of [Ir(CO)<sub>6</sub>][SbF<sub>6</sub>]<sub>3</sub>·4HF − The First Structurally Characterized Salt with a Tripositive, Homoleptic Metal Carbonyl Cation and the First Example of a Tetrahedral Hydrogen-Bonded (HF)<sub>4</sub> Cluster
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Bibliographic record
Abstract
The reductive carbonylation of IrF(6) in a dilute solution of SbF(5) in anhydrous HF (1:6 by volume) produces surprisingly at 25 degrees C and 1.5 atm CO the complex salt [Ir(CO)(6)][SbF(6)](3).4HF, while [Ir(CO)(6)][Sb(2)F(11)](3) is obtained in liquid SbF(5) under similar conditions. Vibrational spectra in the CO stretching range for both salts and [Ir(CO)(6)](3+)((solv)) are identical within error limits, and nu(CO)(av) is with 2269 cm(-1) the highest average stretching frequency so far observed for octahedral metal carbonyl cations. A vibrational assignment supported by DFT calculations is presented, and the vibrational fundamentals are compared to those of [Os(CO)(6)](2+). The molecular structure of [Ir(CO)(6)][SbF(6)](3).4HF is determined by single-crystal X-ray diffraction. Crystal data for [Ir(CO)(6)][SbF(6)](3).4HF: rhombohedral, R3c (No. 161), a = 14.630(4) A, c = 18.377(7) A, V = 3406.4(18) A(3), Z = 6, T = 150 K, R(1) = 0.0338 [I > 2sigma (I)], wR(2) = 0.0797). The average Ir-C bond length in the octahedral [Ir(CO)(6)](3+) cation is with 2.029(10) the longest observed for iridium carbonyl derivatives, consistent with the absence of Ir --> CO pi-back-bonding. The four solvate HF molecules form a tetrahedron via long, asymmetric, and partly delocalized hydrogen bonds with F-F edge lengths of 2.857 (3x) and 2.914 (3x) A. There is no precedent for a polyhedral (HF)(n) cluster in the gas, liquid, or solid phase. The four F atoms of the (HF)(4) cluster are coordinated to the C atoms of the six CO ligands of the cation, which again is without precedent. The coordination of one of the F atoms to three C atoms in a iso-tridentate mode with contact distances C-F(8) of 2.641(10) A is most unusual. The observed tight C-F coordination in [Ir(CO)(6)][SbF(6)](3).4HF provides conclusive evidence for the presence of electrophilic carbon in the cation and illustrates how superelectrophilic cations such as [Ir(CO)(6)](3+) are solvent stabilized in the conjugate Brønsted-Lewis superacid HF-SbF(5).
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
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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