Observation of the Ba(0) Complex BaNi(CO) <sub>3</sub> <sup>–</sup> Featuring the Shortest Bond between Barium and Transition Metal
Bibliographic record
Abstract
The heteronuclear barium–nickel anion complex BaNi(CO) 3 – is prepared in the gas phase and studied by mass-selected infrared photodissociation spectroscopy as well as quantum chemistry calculations. The complex exhibits a 2 A 1 ground electronic state and adopts a C 3 v equilibrium geometry with all three carbonyl ligands coordinated to the nickel center. The Ba–Ni bond distance closely approximates the sum of their covalent radii. Bonding analysis reveals significant covalent interactions between Ba(0) and Ni(CO) 3 –, involving both a Ba(0)–Ni(CO) 3 – covalent half-bond and a Ba(0) → Ni(CO) 3 – dative bonding interaction. This work represents the first observation of a compound containing true Ba(0) in its ground state 6s 2 electron configuration and features the shortest covalent Ba-transition metal single bond. These findings expand the chemistry of heavy alkaline earth metals in low oxidation states and suggest a potential route for the synthesis of Ba(0) compounds in the condensed phase.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 source (direct Gemma or distilled Codex), 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".