Rebecca L. Jones, Zoë R. Turner, Clement G. Collins Rice and Dermot O’Hare*,
{"title":"由苯氧基-亚胺 NON 配体支持的异极性钙配合物:通过配体辅助的活化单体机制聚合环酯","authors":"Rebecca L. Jones, Zoë R. Turner, Clement G. Collins Rice and Dermot O’Hare*, ","doi":"10.1021/acs.organomet.4c00028","DOIUrl":null,"url":null,"abstract":"<p >Phenoxy-imine NON pro-ligands H<sup>R,Dipp</sup>L [1-OH-2,6-(HC═NDipp)-4-R-C<sub>6</sub>H<sub>2</sub>, where R = H, Me, or <sup><i>t</i></sup>Bu] were deprotonated using KH to afford the corresponding potassium salts <sup>R,Dipp</sup>LK·thf<sub><i>x</i></sub> [R = H (<b>1·thf</b><sub><b><i>x</i></b></sub>), Me (<b>2·thf</b><sub><b><i>x</i></b></sub>), and <sup><i>t</i></sup>Bu (<b>3·thf</b><sub><b><i>x</i></b></sub>)]. The addition of crown ether (18-c-6) to these salts allowed for the structures of the resulting adducts to be elucidated in the solid state: <b>[1(18-c-6)]</b><sub><b><i>n</i></b></sub>, <b>[2(18-c-6)]</b><sub><b><i>n</i></b></sub>, and <b>[3(18-c-6)(thf)]</b>. The derivatives with the smaller <i>para</i>-substituents were found to be 1D coordination polymers stabilized by unusual non-covalent interactions between the diisopropyl-methyl groups and the potassium center. Heteroleptic calcium complexes <sup>R,Dipp</sup>LCaI(thf)<sub>3</sub> [R = H (<b>4</b>), Me (<b>5</b>), and <sup><i>t</i></sup>Bu (<b>6</b>)] were prepared by the salt metathesis reaction of <b>1–3·thf</b><sub><b><i>x</i></b></sub> with CaI<sub>2</sub>. Complexes <b>4–6</b> were evaluated as initiators for the ring-opening polymerization of lactide monomers and were all found to be active; the addition of benzyl alcohol resulted in large rate increases, e.g., ∼12-fold difference for <b>6</b> (0.70 vs 0.06 h<sup>–1</sup>). The propagation rate constants were found to lie within the range 88–135 M<sup>–1</sup> h<sup>–1</sup>. Variation of co-initiator concentration revealed only a fractional dependence; this agrees with the other experimental observations, which suggest that the heteroleptic catalysts work via a “ligand-assisted, activated monomer” mechanism.</p>","PeriodicalId":56,"journal":{"name":"Organometallics","volume":null,"pages":null},"PeriodicalIF":2.5000,"publicationDate":"2024-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acs.organomet.4c00028","citationCount":"0","resultStr":"{\"title\":\"Heteroleptic Calcium Complexes Supported by a Phenoxy-Imine NON Ligand: Polymerization of Cyclic Esters by a Ligand-Assisted, Activated-Monomer Mechanism\",\"authors\":\"Rebecca L. Jones, Zoë R. Turner, Clement G. Collins Rice and Dermot O’Hare*, \",\"doi\":\"10.1021/acs.organomet.4c00028\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p >Phenoxy-imine NON pro-ligands H<sup>R,Dipp</sup>L [1-OH-2,6-(HC═NDipp)-4-R-C<sub>6</sub>H<sub>2</sub>, where R = H, Me, or <sup><i>t</i></sup>Bu] were deprotonated using KH to afford the corresponding potassium salts <sup>R,Dipp</sup>LK·thf<sub><i>x</i></sub> [R = H (<b>1·thf</b><sub><b><i>x</i></b></sub>), Me (<b>2·thf</b><sub><b><i>x</i></b></sub>), and <sup><i>t</i></sup>Bu (<b>3·thf</b><sub><b><i>x</i></b></sub>)]. The addition of crown ether (18-c-6) to these salts allowed for the structures of the resulting adducts to be elucidated in the solid state: <b>[1(18-c-6)]</b><sub><b><i>n</i></b></sub>, <b>[2(18-c-6)]</b><sub><b><i>n</i></b></sub>, and <b>[3(18-c-6)(thf)]</b>. The derivatives with the smaller <i>para</i>-substituents were found to be 1D coordination polymers stabilized by unusual non-covalent interactions between the diisopropyl-methyl groups and the potassium center. Heteroleptic calcium complexes <sup>R,Dipp</sup>LCaI(thf)<sub>3</sub> [R = H (<b>4</b>), Me (<b>5</b>), and <sup><i>t</i></sup>Bu (<b>6</b>)] were prepared by the salt metathesis reaction of <b>1–3·thf</b><sub><b><i>x</i></b></sub> with CaI<sub>2</sub>. Complexes <b>4–6</b> were evaluated as initiators for the ring-opening polymerization of lactide monomers and were all found to be active; the addition of benzyl alcohol resulted in large rate increases, e.g., ∼12-fold difference for <b>6</b> (0.70 vs 0.06 h<sup>–1</sup>). The propagation rate constants were found to lie within the range 88–135 M<sup>–1</sup> h<sup>–1</sup>. Variation of co-initiator concentration revealed only a fractional dependence; this agrees with the other experimental observations, which suggest that the heteroleptic catalysts work via a “ligand-assisted, activated monomer” mechanism.</p>\",\"PeriodicalId\":56,\"journal\":{\"name\":\"Organometallics\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.5000,\"publicationDate\":\"2024-04-15\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://pubs.acs.org/doi/epdf/10.1021/acs.organomet.4c00028\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Organometallics\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://pubs.acs.org/doi/10.1021/acs.organomet.4c00028\",\"RegionNum\":3,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"CHEMISTRY, INORGANIC & NUCLEAR\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Organometallics","FirstCategoryId":"92","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acs.organomet.4c00028","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, INORGANIC & NUCLEAR","Score":null,"Total":0}
Heteroleptic Calcium Complexes Supported by a Phenoxy-Imine NON Ligand: Polymerization of Cyclic Esters by a Ligand-Assisted, Activated-Monomer Mechanism
Phenoxy-imine NON pro-ligands HR,DippL [1-OH-2,6-(HC═NDipp)-4-R-C6H2, where R = H, Me, or tBu] were deprotonated using KH to afford the corresponding potassium salts R,DippLK·thfx [R = H (1·thfx), Me (2·thfx), and tBu (3·thfx)]. The addition of crown ether (18-c-6) to these salts allowed for the structures of the resulting adducts to be elucidated in the solid state: [1(18-c-6)]n, [2(18-c-6)]n, and [3(18-c-6)(thf)]. The derivatives with the smaller para-substituents were found to be 1D coordination polymers stabilized by unusual non-covalent interactions between the diisopropyl-methyl groups and the potassium center. Heteroleptic calcium complexes R,DippLCaI(thf)3 [R = H (4), Me (5), and tBu (6)] were prepared by the salt metathesis reaction of 1–3·thfx with CaI2. Complexes 4–6 were evaluated as initiators for the ring-opening polymerization of lactide monomers and were all found to be active; the addition of benzyl alcohol resulted in large rate increases, e.g., ∼12-fold difference for 6 (0.70 vs 0.06 h–1). The propagation rate constants were found to lie within the range 88–135 M–1 h–1. Variation of co-initiator concentration revealed only a fractional dependence; this agrees with the other experimental observations, which suggest that the heteroleptic catalysts work via a “ligand-assisted, activated monomer” mechanism.
期刊介绍:
Organometallics is the flagship journal of organometallic chemistry and records progress in one of the most active fields of science, bridging organic and inorganic chemistry. The journal publishes Articles, Communications, Reviews, and Tutorials (instructional overviews) that depict research on the synthesis, structure, bonding, chemical reactivity, and reaction mechanisms for a variety of applications, including catalyst design and catalytic processes; main-group, transition-metal, and lanthanide and actinide metal chemistry; synthetic aspects of polymer science and materials science; and bioorganometallic chemistry.