Deprotonation and Addition Reactions of Frustrated Lewis Pairs with Alkynes
Bibliographic record
Abstract
Deprotonation of terminal alkynes is effected by the treatment with t Bu 3 P and B(C 6 F 5 ) 3 to give [ t Bu 3 PH][PhCCB(C 6 F 5 ) 3 ] ( 1a ) and [ t Bu 3 PH][RCCB(C 6 F 5 ) 3 ] (R = n Bu 2, t Bu 3, Me 3 Si 4, and CpFe(C 5 H 4 ) 5 ). In a similar fashion, FLP deprotonation of 1,4-diethynylbenzene was employed to prepare the salt [ t Bu 3 PH] 2 [(C 6 F 5 ) 3 BCC(C 6 H 4 )CCB(C 6 F 5 ) 3 ] ( 6 ). As well, use of differing Lewis acids afforded the species [ t Bu 3 PH][PhCCEAr 3 ] (EAr 3 = Al(C 6 F 5 ) 3 7, PhB(C 6 F 5 ) 2 8, BPh 3 9 ). The corresponding reaction of Me 3 SiCCSiMe 3 afforded [ t Bu 3 PSiMe 3 ][Me 3 SiCCB(C 6 F 5 ) 3 ] ( 10 ). For less basic phosphines, phosphine/borane addition reactions were observed with alkynes. Thus the species E -R 3 P(Ph)C═C(H)B(C 6 F 5 ) 3 (R = o -tol 11, Ph 12 ) were prepared. In the latter case, Ph 3 P·B(C 6 F 5 ) 3 was employed. Similarly, E -Ph 3 P(CpFe(C 5 H 4 ))C═C(H)B(C 6 F 5 ) 3 ( 13 ), E -Ph 3 P(Ph)C═C(Me)B(C 6 F 5 ) 3 ( 14 ), E -R 2 PH(Ph)C═C(H)B(C 6 F 5 ) 3 (R = Ph 15, C 6 H 2 Me 3 16 ), and E -(C 6 H 2 t Bu 3 )PH 2 (Ph)C═C(H)B(C 6 F 5 ) 3 ( 17 ) were prepared. Again, variation in the Lewis acid afforded E -Ph 3 P(Ph)C═C(H)EAr 3 (EAr 3 = PhB(C 6 F 5 ) 2 18, Al(C 6 F 5 ) 3 19 ), E -Ph 3 P( n Bu)C═C(H)Al(C 6 F 5 ) 3 ( 20 ), and E -( o -tol) 3 P(Ph)C═C(H)Al(C 6 F 5 ) 3 ( 21 ). The macrocyclic [(H)C═C(Ph)Mes 2 PC 6 F 4 B(C 6 F 5 ) 2 ] 2 ( 22 ) was prepared from the analogous alkyne addition to Mes 2 PC 6 F 4 B(C 6 F 5 ) 2, while E -Ph 2 PCH 2 CH 2 PPh 2 (Ph)C═C(H)B(C 6 F 5 ) 3 ( 23 ) and E -(CH 2 PPh 2 (Ph)C═C(H)B(C 6 F 5 ) 3 ) 2 ( 24 ) were derived from the reactions of Ph 2 PCH 2 CH 2 PPh 2 . The related addition reaction involving 1,4-diethynylbenzene gave E -HC≡CC 6 H 4 C(PPh 3 )═C(H)B(C 6 F 5 ) 3 ( 25 ), while subsequent reaction with t Bu 3 P and B(C 6 F 5 ) 3 yielded the unusual salt/zwitterion [ t Bu 3 PH][(C 6 F 5 ) 3 BCC≡C 6 H 4 C(PPh 3 )═C(H)-B(C 6 F 5 ) 3 ] ( 26 ). Reaction of PhCH 2 NMe 2 with PhCCH and B(C 6 F 5 ) 3 gave give a 84:16 mixture of [PhCH 2 NMe 2 H][PhCCB(C 6 F 5 ) 3 ] ( 27a ) and PhCH 2 NMe 2 (Ph)C═C(H)B(C 6 F 5 ) 3 ( 27b ), while imines were used to prepare [( t Bu)HN═CHPh][PhCCB(C 6 F 5 ) 3 ] ( 28 ) and [( t Bu)HN═CPh 2 ][PhCCB(C 6 F 5 ) 3 ] ( 29 ). The corresponding reaction of t BuNCN t Bu, B(C 6 F 5 ) 3, and two equivalents of PhCCH led to the unusual product [ t BuNCN(H)C(Ph)═C(H) t Bu][PhCCB(C 6 F 5 ) 3 ] ( 30 ). Finally, non-pnictogen Lewis bases were explored. The reaction of the N-heterocyclic carbene I t Bu with B(C 6 F 5 ) 3 and PhCCH was shown to yield the deprotonation product [I t BuH][PhCCB(C 6 F 5 ) 3 ] ( 31 ), while the sulfides R 2 S gave E -R 2 S(Ph)C═C(H)B(C 6 F 5 ) 3 (R = Me 32, PhCH 2 33 ). The formation of these latter sulfide zwitterions was demonstrated to be reversible.
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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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".