Synthesis, Structure, and Fluxionality of Strained Hypercoordinate Silicon‐Bridged [1]Ferrocenophanes
Bibliographic record
Abstract
Abstract The first hypercoordinate sila[1]ferrocenophanes [fcSiMe(2‐C6H4CH2NMe2)] (5 a) and [fcSi(CH2Cl)(2‐C6H4CH2NMe2)] (5 b) (fc=(η5‐C5H4)Fe(η5‐C5H4)) were synthesized by low‐temperature (−78 °C) reactions of Li[2‐C6H4CH2NMe2] with the appropriate chlorinated sila[1]ferrocenophanes ([fcSiMeCl] (1 a) and [fcSi(CH2Cl)Cl] (1 d), respectively). Single‐crystal Xray diffraction studies revealed pseudo‐trigonal bipyramidal structures for both 5 a and 5 b, with one of the shortest reported Si⋅⋅⋅N distances for an sp3‐hybridized nitrogen atom interacting with a tetraorganosilane detected for 5 a (2.776(2) Å). Elongated SiCipso bonds trans to the donating NMe2 arms (1.919(2) and 1.909(2) Å for 5 a and 5 b, respectively) were observed relative to both the non‐trans bonds (5 a: 1.891(2); 5 b: 1.879(2) Å) and the SiCipso bonds of the non‐hypercoordinate analogues ([fcSiMePh] (1 b): 1.879(4), 1.880(4) Å; [fcSi(CH2Cl)Ph] (1 e): 1.881(2), 1.884(2)). Solution‐state fluxionality of 5 a and 5 b, suggestive of reversible coordination of the NMe2 group to silicon, was demonstrated by means of variable‐temperature NMR studies. The ΔG≠ of the fluxional processes for 5 a and 5 b in CD2Cl2 were estimated to be 35.0 and 37.6 kJ mol−1, respectively (35.8 and 38.3 kJ mol−1 in [D8]toluene). The quaternization of 5 a and 5 b by MeOTf, to give [fcSiMe(2‐C6H4CH2NMe3)][OTf] (7 a‐OTf) and [fcSi(CH2Cl)(2‐C6H4CH2NMe3)][OTf] (7 b‐OTf), respectively, supported the reversibility of NMe2 coordination at the silicon center as the source of fluxionality for 5 a and 5 b. Surprisingly, low room‐temperature stability was detected for 5 b due to its tendency to intramolecularly cyclize and form the spirocyclic [fcSi(cyclo‐CH2NMe2CH2C6H4)]Cl (9‐Cl). This process was observed in both solution and the solid state, and isolation and Xray characterization of 9‐Cl was achieved. The model compound, [Fc2Si(2‐C6H4CH2NMe2)2] (8), synthesized through reaction of [Fc2SiCl2] with two equivalents of Li[2‐C6H4CH2NMe2] at −78 °C, showed a lack of hypercoordination in both the solid state and in solution (down to −80 °C). This suggests that either the reduced steric hindrance around Si or the unique electronics of the strained sila[1]ferrocenophanes is necessary for hypercoordination to occur.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 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".