Reactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer Reactions
We report a comprehensive combined experimental and DFT investigation of the synthesis, molecular and electronic structures, and reactivity of terminal hydrazido complexes with CO2, CS2, isocyanates, and isothiocyanates. Reaction of Cp*Ti{MeC(NiPr) 2}(NtBu) with hydrazines R1R 2NNH2 gave the structu...
| Main Authors: | , , , , , , , |
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| Format: | Journal article |
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2011
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| _version_ | 1797070799276867584 |
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| author | Tiong, P Nova, A Groom, L Schwarz, A Selby, J Schofield, A Clot, E Mountford, P |
| author_facet | Tiong, P Nova, A Groom, L Schwarz, A Selby, J Schofield, A Clot, E Mountford, P |
| author_sort | Tiong, P |
| collection | OXFORD |
| description | We report a comprehensive combined experimental and DFT investigation of the synthesis, molecular and electronic structures, and reactivity of terminal hydrazido complexes with CO2, CS2, isocyanates, and isothiocyanates. Reaction of Cp*Ti{MeC(NiPr) 2}(NtBu) with hydrazines R1R 2NNH2 gave the structurally characterized series of hydrazides Cp*Ti{MeC(NiPr)2}(NNR1R 2) (R1 = Ph, R2 = Ph (13), Me (14); R 1 = R2 = Me (15)). The energetics of this imide/hydrazine exchange reaction, as well as the electronic and molecular structures of 13-15, have been evaluated by DFT and compared with those of their methyl and phenyl imido counterparts. Reaction of 13-15 with CO2 or CS2 gave Ti=Nα cycloaddition products of the type Cp* Ti{MeC(NiPr)2}{N(NR2)C(E)E} (R = Ph, Me; E = O, S) and, in the case of CO2, cycloaddition-insertion products Cp*Ti{MeC(NiPr)2}{OC(O)N(NR2)C(O)O}, in which 2 equivs of CO2 had effectively inserted into Ti=N α. Reaction of 13 with isocyanates and isothiocyanates also gave stable cycloaddition products. Cp*Ti{MeC(NiPr) 2}{N(NPh2)C(NTol)O} reacted further with CO2 to give a mixed cycloaddition-insertion product. The tBuNCO moiety in Cp*Ti{MeC(NiPr)2}{N(NPh2)C(N tBu)O} could be displaced by CO2 or TolNCO. In contrast, the reactions of 15 are dominated by cycloaddition-elimination reactions. Reaction with tBuNCO or Ar′NCO (2 equivs) gave tBuNCNNMe2 or the heterocycle 1,2,4-N(Me) 2NC(NAr′)N(Ar′)C(O), respectively, along with [Cp*Ti{MeC(NiPr)2}(μ-O)]2. With TolNCO (2 equivs), Cp*Ti{MeC(NiPr)2}{OC(NNMe 2)N(Tol)C(NTol)O} was formed via a series of cycloaddition- elimination and cycloaddition-insertion steps. The energetics and mechanisms of the cycloaddition, cycloaddition-insertion, and cycloaddition-extrusion processes of various model imido and hydrazido complexes have been investigated using DFT. In the latter (metathesis) reactions, the reaction outcomes depend on a delicate balance of the relative affinities of NR or NNR2 for the metal center or the organic fragment (CO, CS, or RNC). © 2011 American Chemical Society. |
| first_indexed | 2024-03-06T22:44:08Z |
| format | Journal article |
| id | oxford-uuid:5c91ba1d-7a36-4bcd-8420-d6f0d802995c |
| institution | University of Oxford |
| last_indexed | 2024-03-06T22:44:08Z |
| publishDate | 2011 |
| record_format | dspace |
| spelling | oxford-uuid:5c91ba1d-7a36-4bcd-8420-d6f0d802995c2022-03-26T17:29:05ZReactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer ReactionsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:5c91ba1d-7a36-4bcd-8420-d6f0d802995cSymplectic Elements at Oxford2011Tiong, PNova, AGroom, LSchwarz, ASelby, JSchofield, AClot, EMountford, PWe report a comprehensive combined experimental and DFT investigation of the synthesis, molecular and electronic structures, and reactivity of terminal hydrazido complexes with CO2, CS2, isocyanates, and isothiocyanates. Reaction of Cp*Ti{MeC(NiPr) 2}(NtBu) with hydrazines R1R 2NNH2 gave the structurally characterized series of hydrazides Cp*Ti{MeC(NiPr)2}(NNR1R 2) (R1 = Ph, R2 = Ph (13), Me (14); R 1 = R2 = Me (15)). The energetics of this imide/hydrazine exchange reaction, as well as the electronic and molecular structures of 13-15, have been evaluated by DFT and compared with those of their methyl and phenyl imido counterparts. Reaction of 13-15 with CO2 or CS2 gave Ti=Nα cycloaddition products of the type Cp* Ti{MeC(NiPr)2}{N(NR2)C(E)E} (R = Ph, Me; E = O, S) and, in the case of CO2, cycloaddition-insertion products Cp*Ti{MeC(NiPr)2}{OC(O)N(NR2)C(O)O}, in which 2 equivs of CO2 had effectively inserted into Ti=N α. Reaction of 13 with isocyanates and isothiocyanates also gave stable cycloaddition products. Cp*Ti{MeC(NiPr) 2}{N(NPh2)C(NTol)O} reacted further with CO2 to give a mixed cycloaddition-insertion product. The tBuNCO moiety in Cp*Ti{MeC(NiPr)2}{N(NPh2)C(N tBu)O} could be displaced by CO2 or TolNCO. In contrast, the reactions of 15 are dominated by cycloaddition-elimination reactions. Reaction with tBuNCO or Ar′NCO (2 equivs) gave tBuNCNNMe2 or the heterocycle 1,2,4-N(Me) 2NC(NAr′)N(Ar′)C(O), respectively, along with [Cp*Ti{MeC(NiPr)2}(μ-O)]2. With TolNCO (2 equivs), Cp*Ti{MeC(NiPr)2}{OC(NNMe 2)N(Tol)C(NTol)O} was formed via a series of cycloaddition- elimination and cycloaddition-insertion steps. The energetics and mechanisms of the cycloaddition, cycloaddition-insertion, and cycloaddition-extrusion processes of various model imido and hydrazido complexes have been investigated using DFT. In the latter (metathesis) reactions, the reaction outcomes depend on a delicate balance of the relative affinities of NR or NNR2 for the metal center or the organic fragment (CO, CS, or RNC). © 2011 American Chemical Society. |
| spellingShingle | Tiong, P Nova, A Groom, L Schwarz, A Selby, J Schofield, A Clot, E Mountford, P Reactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer Reactions |
| title | Reactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer Reactions |
| title_full | Reactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer Reactions |
| title_fullStr | Reactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer Reactions |
| title_full_unstemmed | Reactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer Reactions |
| title_short | Reactions of Cyclopentadienyl-Amidinate Titanium Hydrazides with CO2, CS2, and Isocyanates: Ti=N-alpha Cycloaddition, Cycloaddition-Insertion, and Cycloaddition-NNR2 Group Transfer Reactions |
| title_sort | reactions of cyclopentadienyl amidinate titanium hydrazides with co2 cs2 and isocyanates ti n alpha cycloaddition cycloaddition insertion and cycloaddition nnr2 group transfer reactions |
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