Magnesium, calcium and zinc [N2N'] heteroscorpionate complexes
A new family of sterically demanding N2N′ heteroscorpionate pro-ligands (HC(tBu2pz)2SiMe2N(H)R (R = iPr, tBu, Ph, Xyl)) has been prepared via a straightforward modular synthetic route. An extensive study into the synthesis and characterisation of lithium, magnesium, calcium and zinc complexes suppor...
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| Format: | Journal article |
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Royal Society of Chemistry
2019
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| _version_ | 1797073944863309824 |
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| author | Luna Barros, M Cushion, M Schwarz, A Turner, Z Mountford, P |
| author_facet | Luna Barros, M Cushion, M Schwarz, A Turner, Z Mountford, P |
| author_sort | Luna Barros, M |
| collection | OXFORD |
| description | A new family of sterically demanding N2N′ heteroscorpionate pro-ligands (HC(tBu2pz)2SiMe2N(H)R (R = iPr, tBu, Ph, Xyl)) has been prepared via a straightforward modular synthetic route. An extensive study into the synthesis and characterisation of lithium, magnesium, calcium and zinc complexes supported by both 3,5-tBu and 3,5-Me substituted N2N′ ligand families has been conducted. Attempted deprotonation of the pro-ligands with nBuLi afforded the corresponding lithium salts Li{HC(tBu2pz)2SiMe2NR} (R = iPr (1), tBu (2), Ph (3) and Xyl (4)) but air- and thermal-sensitivity limited the yields of these potentially useful precursors; only the sterically encumbered ligand system allowed clean reactivity. Magnesium methyl complexes Mg{HC(tBu2pz)2SiMe2NR}Me (R = iPr (5) and R = Ph (6)) were prepared using an excess of the Grignard reagent MeMgCl. Magnesium butyl complexes were synthesised in good yields using the dialkyl precursor MgnBu2 to afford Mg{HC(R′2pz)2SiMe2NR}nBu (R′ = Me; R = iPr (7), tBu (8), Ad (9), Ph (10). R′ = tBu; R = iPr (11), Ph (12)). Protonolylsis reactions were used to synthesise magnesium and calcium amide complexes Mg{HC(R′2pz)2SiMe2NR}{N(SiHMe2)2} (R′ = Me; R = iPr (13), tBu (14), Ph (15). R′ = tBu; R = Ph (16)) or Mg{HC(R′2pz)2SiMe2NR}{N(SiMe3)2} (R′ = Me; R = iPr (17), tBu (18), Ph (19). R′ = tBu; R = Ph (20)), and Ca{HC(R′2pz)2SiMe2NR}{N(SiMe2)2} (L) (R′ = Me; L = thf; R = iPr (21), tBu (22), Ph (23). R′ = tBu; L = none; R = Ph (24). Zinc methyl complexes Zn{HC(R′2pz)2SiMe2NR}Me (R′ = Me; R = iPr (25), tBu (26), Ph (27). R′ = tBu; R = Ph (28)) were prepared by reaction of the N2N′ heteroscorpionate pro-ligands with ZnMe2. In preliminary studies, magnesium amide complexes 16 and 20 were evaluated as initiators for the ring-opening polymerisation (ROP) of ε-caprolactone (ε-CL) and rac-lactide (rac-LA). Although the overall polymerisation control was poor, 16 and 20 were found to be active initiators. |
| first_indexed | 2024-03-06T23:29:11Z |
| format | Journal article |
| id | oxford-uuid:6b6d34f6-a1cc-41b5-96fc-712dba147181 |
| institution | University of Oxford |
| last_indexed | 2024-03-06T23:29:11Z |
| publishDate | 2019 |
| publisher | Royal Society of Chemistry |
| record_format | dspace |
| spelling | oxford-uuid:6b6d34f6-a1cc-41b5-96fc-712dba1471812022-03-26T19:03:58ZMagnesium, calcium and zinc [N2N'] heteroscorpionate complexesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:6b6d34f6-a1cc-41b5-96fc-712dba147181Symplectic Elements at OxfordRoyal Society of Chemistry2019Luna Barros, MCushion, MSchwarz, ATurner, ZMountford, PA new family of sterically demanding N2N′ heteroscorpionate pro-ligands (HC(tBu2pz)2SiMe2N(H)R (R = iPr, tBu, Ph, Xyl)) has been prepared via a straightforward modular synthetic route. An extensive study into the synthesis and characterisation of lithium, magnesium, calcium and zinc complexes supported by both 3,5-tBu and 3,5-Me substituted N2N′ ligand families has been conducted. Attempted deprotonation of the pro-ligands with nBuLi afforded the corresponding lithium salts Li{HC(tBu2pz)2SiMe2NR} (R = iPr (1), tBu (2), Ph (3) and Xyl (4)) but air- and thermal-sensitivity limited the yields of these potentially useful precursors; only the sterically encumbered ligand system allowed clean reactivity. Magnesium methyl complexes Mg{HC(tBu2pz)2SiMe2NR}Me (R = iPr (5) and R = Ph (6)) were prepared using an excess of the Grignard reagent MeMgCl. Magnesium butyl complexes were synthesised in good yields using the dialkyl precursor MgnBu2 to afford Mg{HC(R′2pz)2SiMe2NR}nBu (R′ = Me; R = iPr (7), tBu (8), Ad (9), Ph (10). R′ = tBu; R = iPr (11), Ph (12)). Protonolylsis reactions were used to synthesise magnesium and calcium amide complexes Mg{HC(R′2pz)2SiMe2NR}{N(SiHMe2)2} (R′ = Me; R = iPr (13), tBu (14), Ph (15). R′ = tBu; R = Ph (16)) or Mg{HC(R′2pz)2SiMe2NR}{N(SiMe3)2} (R′ = Me; R = iPr (17), tBu (18), Ph (19). R′ = tBu; R = Ph (20)), and Ca{HC(R′2pz)2SiMe2NR}{N(SiMe2)2} (L) (R′ = Me; L = thf; R = iPr (21), tBu (22), Ph (23). R′ = tBu; L = none; R = Ph (24). Zinc methyl complexes Zn{HC(R′2pz)2SiMe2NR}Me (R′ = Me; R = iPr (25), tBu (26), Ph (27). R′ = tBu; R = Ph (28)) were prepared by reaction of the N2N′ heteroscorpionate pro-ligands with ZnMe2. In preliminary studies, magnesium amide complexes 16 and 20 were evaluated as initiators for the ring-opening polymerisation (ROP) of ε-caprolactone (ε-CL) and rac-lactide (rac-LA). Although the overall polymerisation control was poor, 16 and 20 were found to be active initiators. |
| spellingShingle | Luna Barros, M Cushion, M Schwarz, A Turner, Z Mountford, P Magnesium, calcium and zinc [N2N'] heteroscorpionate complexes |
| title | Magnesium, calcium and zinc [N2N'] heteroscorpionate complexes |
| title_full | Magnesium, calcium and zinc [N2N'] heteroscorpionate complexes |
| title_fullStr | Magnesium, calcium and zinc [N2N'] heteroscorpionate complexes |
| title_full_unstemmed | Magnesium, calcium and zinc [N2N'] heteroscorpionate complexes |
| title_short | Magnesium, calcium and zinc [N2N'] heteroscorpionate complexes |
| title_sort | magnesium calcium and zinc n2n heteroscorpionate complexes |
| work_keys_str_mv | AT lunabarrosm magnesiumcalciumandzincn2nheteroscorpionatecomplexes AT cushionm magnesiumcalciumandzincn2nheteroscorpionatecomplexes AT schwarza magnesiumcalciumandzincn2nheteroscorpionatecomplexes AT turnerz magnesiumcalciumandzincn2nheteroscorpionatecomplexes AT mountfordp magnesiumcalciumandzincn2nheteroscorpionatecomplexes |