Intra- and inter-ion-pair protonic-hydridic bonding in polyhydridobis(phosphine)rhenates
Bibliographic record
Abstract
The hexahydridobis(phosphine)rhenate anions, [ReH 6 (PR 3 ) 2 ] - (PR 3 = PCy 3 , P-i-Pr 3 , PPh 3 , PMe 3 ) were generated by potassium hydride deprotonation of the neutral heptahydride conjugate acids (ReH 7 (PR 3 ) 2 ), isolated as their [K(18-crown-6)] + and [K(1,10-diaza-18-crown-6)] + salts, and characterized by NMR and IR spectroscopy and elemental analyses. Structures from single crystal X-ray diffraction were obtained for the [K(1,10-diaza-18-crown-6)] + salts and these indicate the presence of short protonichydridic bonds involving the hydrides of the anions and the proton donor NH moieties of the cations. The structure of [K(1,10-diaza-18-crown-6)][ReH 6 (P-i-Pr 3 ) 2 ] adopts a one-dimensional zigzag chain with alternating cations and anions connected and held together by inter-ion N-H···H x -Re interactions (x = 1 or 2). Short distances between the NH protons of the cations and hydrides of the anion ranging from 1.6 to 1.9 Å are estimated for this complex. A different kind of chain structure is observed for [K(1,10-diaza-18-crown-6)][ReH 6 (PMe 3 ) 2 ] in which the combined effects of inter-ion protonichydridic bonding (N-H···H x -Re) and inter-ion electrostatic interactions (ReH - x ···K + ···H - x Re), result in one-dimensional networks of alternating cations and anions, with the metals and hydrides occupying the interior and the organic moieties of the phosphine ligands and crown ether lining the exterior of cylindrical supramolecular assemblies. A combination of intra- and inter-ion protonic-hydridic and intra-ion-pair electrostatic interactions in [K(1,10-diaza-18-crown-6)][ReH 6 (PPh 3 ) 2 ] result in the formation of discrete two-dimensional {[K(1,10-diaza-18-crown-6)][ReH 6 (PPh 3 ) 2 ]} 4 tetramers. The PCy 3 salt is disordered but appears to consist of isolated 1:1 ion pairs containing strong intra-ion-pair NH···HRe bonding. The solid-state IR spectra of the [K(1,10-diaza-18-crown-6)] + salts show low-frequency shifts for the NH bands relative to [K(1,10-diaza-18-crown-6)][BPh 4 ], and perturbed Re-H bands relative to those in the [K(18-crown-6)] + salts. The magnitude of ΔνNH is related to the basicity of the anion as indicated by the pKα THF of the conjugate acid form (ReH 7 (PR 3 ) 2 ), which increases as PPh 3 < < PMe 3 < P-i-Pr 3 < PCy 3 . Solution 1 H NMR, NOE, and T 1 relaxation measurements of [K(1,10-diaza-18-crown-6)][ReH 6 (PPh 3 ) 2 ] indicate that these interactions also persist in toluene solutions of this compound.Key words: rhenium, hydride, phosphine, hydrogen bonding, self-assembly.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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; a candidate call from one teacher head, not a consensus.
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".