Bis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activation
The reaction of the bis(pentalene)dititanium complex Ti2(μ:η5,η5-Pn†)2 (Pn† = C8H4(1,4-SiiPr3)2) (1) with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene results in intramolecular C–H activation of an isopropyl substituent to form a tucked-in hydride (3). Whilst pyridine will also e...
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| Format: | Journal article |
| Language: | English |
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Royal Society of Chemistry
2018
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| _version_ | 1797074317907853312 |
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| author | Tsoureas, N Green, J Cloke, F |
| author_facet | Tsoureas, N Green, J Cloke, F |
| author_sort | Tsoureas, N |
| collection | OXFORD |
| description | The reaction of the bis(pentalene)dititanium complex Ti2(μ:η5,η5-Pn†)2 (Pn† = C8H4(1,4-SiiPr3)2) (1) with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene results in intramolecular C–H activation of an isopropyl substituent to form a tucked-in hydride (3). Whilst pyridine will also effect this cyclometallation reaction to form (5), the pyridine analogue of (3), the bases 1,2,4,5-tetramethyl-imidazole, 2,6-lutidine, DABCO or trimethylphosphine are ineffective. The reaction of (1) with 2,6-dichloro-pyridine affords crystallographically characterised (6) which is the product of oxidative addition of one of the C–Cl bonds in 2,6-dichloro-pyridine across the Ti–Ti double bond in (1). The tucked-in hydride (3) reacts with hydrogen to afford a dihydride complex (4) in which the tuck-in process has been reversed; detailed experimental and computational studies on this reaction using D2, HD or H2/D2 support a mechanism for the formation of (4) which does not involve σ-bond metathesis of H2 with the tucked-in C–H bond in (3). The reaction of (3) with tBuCCH yields the corresponding acetylide hydrido complex (7), where deuteration studies show that again the reaction does not proceed via σ-bond metathesis. Finally, treatment of (3) with HCl affords the chloro-derivative (9) [(NHC)Ti(μ-H)Ti{(μ,η5:η5)Pn†}2Cl], whereas protonation with [NEt3H]BPh4 yielded a cationic hydride (10) featuring an agostic interaction between a Ti centre and an iPr Me group. |
| first_indexed | 2024-03-06T23:34:22Z |
| format | Journal article |
| id | oxford-uuid:6d22dff5-d1c1-4b5f-ba58-e65629fc8b24 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:34:22Z |
| publishDate | 2018 |
| publisher | Royal Society of Chemistry |
| record_format | dspace |
| spelling | oxford-uuid:6d22dff5-d1c1-4b5f-ba58-e65629fc8b242022-03-26T19:15:52ZBis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activationJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:6d22dff5-d1c1-4b5f-ba58-e65629fc8b24EnglishSymplectic Elements at OxfordRoyal Society of Chemistry2018Tsoureas, NGreen, JCloke, FThe reaction of the bis(pentalene)dititanium complex Ti2(μ:η5,η5-Pn†)2 (Pn† = C8H4(1,4-SiiPr3)2) (1) with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene results in intramolecular C–H activation of an isopropyl substituent to form a tucked-in hydride (3). Whilst pyridine will also effect this cyclometallation reaction to form (5), the pyridine analogue of (3), the bases 1,2,4,5-tetramethyl-imidazole, 2,6-lutidine, DABCO or trimethylphosphine are ineffective. The reaction of (1) with 2,6-dichloro-pyridine affords crystallographically characterised (6) which is the product of oxidative addition of one of the C–Cl bonds in 2,6-dichloro-pyridine across the Ti–Ti double bond in (1). The tucked-in hydride (3) reacts with hydrogen to afford a dihydride complex (4) in which the tuck-in process has been reversed; detailed experimental and computational studies on this reaction using D2, HD or H2/D2 support a mechanism for the formation of (4) which does not involve σ-bond metathesis of H2 with the tucked-in C–H bond in (3). The reaction of (3) with tBuCCH yields the corresponding acetylide hydrido complex (7), where deuteration studies show that again the reaction does not proceed via σ-bond metathesis. Finally, treatment of (3) with HCl affords the chloro-derivative (9) [(NHC)Ti(μ-H)Ti{(μ,η5:η5)Pn†}2Cl], whereas protonation with [NEt3H]BPh4 yielded a cationic hydride (10) featuring an agostic interaction between a Ti centre and an iPr Me group. |
| spellingShingle | Tsoureas, N Green, J Cloke, F Bis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activation |
| title | Bis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activation |
| title_full | Bis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activation |
| title_fullStr | Bis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activation |
| title_full_unstemmed | Bis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activation |
| title_short | Bis(pentalene)dititanium chemistry: C–H, C–X and H–H bond activation |
| title_sort | bis pentalene dititanium chemistry c h c x and h h bond activation |
| work_keys_str_mv | AT tsoureasn bispentalenedititaniumchemistrychcxandhhbondactivation AT greenj bispentalenedititaniumchemistrychcxandhhbondactivation AT clokef bispentalenedititaniumchemistrychcxandhhbondactivation |