Gas-Phase Coordination of Mg<sup>+</sup>, (<i>c</i>-C<sub>5</sub>H<sub>5</sub>)Mg<sup>+</sup>, and (<i>c</i>-C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>Mg<sup>+</sup> with Saturated Hydrocarbons
Bibliographic record
Abstract
The coordination of the electronic ground states of Mg +, ( c -C 5 H 5 )Mg +, and ( c -C 5 H 5 ) 2 Mg + with the straight-chain saturated hydrocarbons methane, ethane, n -propane, n -butane, n -pentane, n -hexane, and n -heptane has been investigated in the gas phase in helium at room temperature and moderate pressures. Reaction rate coefficients and product distributions were measured with the selected-ion flow tube (SIFT) technique operating at 294 ± 3 K and a helium buffer-gas pressure of 0.35 ± 0.01 Torr. Rate coefficients were measured for all observed ligation steps (or upper limits in the case of nonreactions), and bond connectivities in the coordinated ions were probed with multicollision-induced dissociation. Only single ligation was observed. The rate of ligation was found to depend on the size of the saturated hydrocarbon, increasing with increasing size until the collision rate is reached, and on the degree of ligation with c -C 5 H 5 . Mg + was found to be unreactive with methane and ethane, k < 10 -13 cm 3 molecule -1 s -1, but ligation was observed with the other hydrocarbons, k ≥ 7 × 10 -12 cm 3 molecule -1 s -1 . Single ligation of Mg + with c -C 5 H 5 substantially enhances the efficiency of subsequent ligation: the ligation is rapid, k ≥ 1.4 × 10 -10 cm 3 molecule -1 s -1, with all the saturated hydrocarbons investigated. Double ligation with c -C 5 H 5 completely shuts down the efficiency of ligation: no reaction was observed between the saturated hydrocarbons and the full-sandwich magnesocene cation, k < 10 -13 cm 3 molecule -1 s -1 . A linear correlation is reported between the measured thresholds for multicollision-induced dissociation and the polarizability of the hydrocarbon ligand. With a view to published calculations by Bauschlicher et al. for Mg + −CH 4 and Mg + −C 2 H 4, this correlation is consistent with end-on structures for the Mg + −L and ( c -C 5 H 5 )Mg + −L species observed in this study. A detailed study using density functional theory for the interaction of Mg + with three rotamers of n -pentane indicates that interconversion of different isomers of Mg + − n -C 5 H 12 should be easy, even at room temperature and that the ligated species Mg + − n -C 5 H 12 is “dynamic” rather than “static”. Stronger bonding (by a factor of about two) is indicated for ( c -C 5 H 5 )Mg + −L by the multicollision CID experiments, and this is consistent with a formal description of ( c -C 5 H 5 )Mg + as ( c -C 5 H 5 ) - Mg 2+ .
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How this classification was reachedexpand
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) | 0.004 | 0.003 |
| Meta-epidemiology (broad) | 0.005 | 0.002 |
| Bibliometrics | 0.000 | 0.003 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.002 | 0.007 |
| 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 itClassification
machine, unvalidatedMachine predicted; both teacher heads agree on what is shown here.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".