Aluminum amine-bis(phenolate) complexes for ring-opening polymerization of rac-lactide and ε-caprolactone

Five aluminum-based amine-bis(phenolate) complexes, three of them novel, with variation of the pendant donor arm were synthesized in excellent yields, and characterized by NMR spectroscopy and X-ray crystallography. The quantitative conversion of the aluminum alkyl species to the corresponding benzyl alkoxide was achieved by the addition of 1 mol eq. of benzyl alcohol, and was confirmed by 1H NMR spectroscopy. The aluminum alkoxides were excellent mediators for the ring-opening polymerization (ROP) of rac-lactide, yielding atactic poly(lactic acid), having excellent correlation between theoretical and calculated molecular weights accompanied by narrow molecular weight distributions. ROP of ε-caprolactone by the aluminum alkoxides showed modest control at 50°C in toluene, but much greater control was achieved when polymerizations were conducted at 25°C, with narrower molecular weight distributions observed in some cases. A relationship between the complex pendant donor arm and the resulting activity in the ROP of both rac-lactide and ε-caprolactone is discussed

Warum spielen wir Computerspiele? Von Counter Strike bis World of Warcraft: wie sich Identität in Online-Spielen konstituiert

Seit der Entstehung der ersten Computerspiele in den achtziger Jahren sind diese mittlerweile aus dem Alltag kaum mehr wegzudenken. Im Rahmen dieser Arbeit soll der Frage nachgegangen werden, wie sich Identitäten in Online-Spielen konstruieren. Hierfür wurden verschiedene Identitätskonzepte auf ihre Relevanz für Online-Spieler-Identitäten untersucht, es wurden sieben Leitfadeninterviews mit langjährigen Spielern von Online-Rollenspielen (MMORPGs), Strategiespielen (MOBAs) und Ego-Shootern durchgeführt und im Hinblick auf die Identitätskonstruktion ausgewertet

Bis(μ-diethyl­phosphido-κ2 P:P)bis­[bis(2,4,6-trimethyl­phen­yl)indium(III)]

The title compound, [In2(C9H11)4(C4H10P)2], contains a centrosymmetric In2P2 core with short inter­molecular In—P bonds. This core has acute P—In—P and obtuse In—P—In bond angles compared with other [R 2InPR′2]2 analogues, due to the presence of the bulky aromatic substituents on the In atom and the non-sterically demanding ethyl substituents on the P atom

(E)-3-Bromo-N-(1,3-oxazolidin-2-yl­idene)benzamide

The five- and six-membered rings in the title compound, C10H9BrN2O2, are essentially coplanar. This is consistent with a highly conjugated system, as seen in the short N—C bond distances of 1.308 (6) and 1.317 (5) Å

2,2′-(3,3′-Dihexyl-2,2′-bithio­phene-5,5′-di­yl)bis­(4,4,5,5-tetra­methyl-1,3,2-dioxaborolane)

In the title mol­ecule, C32H52B2O4S2, the two thio­phene rings are twisted by 67.34 (2)°. In the crystal, weak C—H⋯O hydrogen bonds link mol­ecules related by translation along the a axis into chains

There Ain\u27t No Flies On Auntie

Elderly woman with fur boa and circlet made of flowers; Green stripe in background with separated jagged stripe above and belowhttps://scholarsjunction.msstate.edu/cht-sheet-music/11145/thumbnail.jp

Ring-opening polymerization of <em>rac</em>-lactide and ε-caprolactone using zinc and calcium salicylaldiminato complexes

Tridentate Schiff base complexes of zinc and calcium were prepared and tested in the ring-opening polymerization of ε-caprolactone and rac-lactide to generate biodegradable polymeric materials from biocompatible metals. Alteration of the pendant donor arm attached to the imine backbone provides some control over catalyst composition and polymerization activity. Complexes of the formula [ONN]ZnN(SiMe3)2, where [ONN] = 2-(N-donor arm-imine)[4,6-di(tert-butyl)phenoxide], were isolated with ethyldimethylamine, ethylpiperidine, and ethylmorpholine substituents, while disproportionation led to the isolation of [ONN]2Zn complexes with methylpyridine, quinoline, and ethyldiisopropylamine derivatives, two of which were crystallographically characterized. Calcium complexes were more stable and novel [ONN]CaN(SiMe3)2 complexes with ethylpiperidine and ethyldiisopropylamine substituents were reported. Zinc and calcium catalysts coordinated to a single tridentate ligand were effective at initiating the polymerization of ε-caprolactone, but did not control the polymerizations, whereas the bis(ligand) complexes produced no polymer. These catalysts were effective at controlling the polymerization of rac-lactide. Coordinatively saturated complexes inhibit the polymerization, while initiation from either the amido or ligand alkoxide functionalities produces poly(lactic acid) with low polydispersities. </jats:p