Ground-State Electronic Asymmetry in Cp*W(NO)(η<sup>1</sup>-isonitrile)<sub>2</sub>Complexes
Bibliographic record
Abstract
The three Cp*W(NO)(η 1 -isonitrile) 2 complexes [Cp* = η 5 -C 5 Me 5; isonitrile = CNCMe 3 ( 1 ), CN-2,6-Me 2 C 6 H 3 ( 2 ), CN- n -C 4 H 9 ( 3 )] possess asymmetrical “piano-stool” molecular structures in the solid state in which their two isonitrile ligands exhibit distinctly different degrees of W→isonitrile back-bonding. Thus, an X-ray crystallographic analysis of 1 as a benzene hemisolvate has established that it has one essentially linear isonitrile ligand having a C−N bond length of 1.159(5) Å and a C−N−C bond angle of 171.4(5)° and one very bent isonitrile ligand (indicative of considerable W→CNCMe 3 π-back-bonding) having C−N = 1.200(5) Å and C−N−C = 135.1(4)°. Complex 2 crystallizes with two crystallographically independent molecules in the asymmetric unit, and the isonitrile ligands in each of these molecules exhibit metrical parameters similar to those extant in 1 . The presence of the inequivalent isonitrile ligands is also manifested in the IR spectra of the three compounds both in the solid state and in solution. For instance, the Nujol mull IR spectrum of 1 contains absorptions at 2038 and 1853 cm −1, attributable to ν CN of the linear and bent isonitrile ligands, respectively. An Et 2 O solution of 1 exhibits these bands at 2051 and 1855 cm −1 . However, their 1 H and 13 C{ 1 H} NMR spectra indicate that on the NMR time scale all three isonitrile complexes are fluxional in solution. Thus, at room temperature the 1 H and 13 C{ 1 H} NMR spectra of 1 in C 6 D 6 and C 6 D 5 CD 3 indicate the equivalence of the two isonitrile carbon atoms attached to the tungsten center and the slight inequivalence of the CMe 3 components of the two isonitrile ligands, and these spectra remain invariant to −80 °C. The results of DFT calculations on the model complex CpW(NO)(CNMe) 2 reproduce the asymmetric distortion as the optimized geometry from various starting points even though it has a relatively shallow potential well. Interestingly, optimization of the related TpW(NO)(CNMe) 2 [Tp = [HB(C 3 N 2 H 3 ) 3 ] − ] results in a symmetric geometry with isonitrile CNC angles of 177.0° and 177.8°. Hence, it is clearly the interaction of the Cp ligand with the orbitals of the W(NO)(CNMe) 2 fragment that allows the system to get to lower energy by skewing the isonitrile bending to one side.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.025 | 0.002 |
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".