In order to isolate a monometallic Mg radical, the precursor (Am)MgI⋅(CAAC) (1) was prepared (Am=tBuC(N‐DIPP)2, DIPP=2,6‐diisopropylphenyl, CAAC=cyclic (alkyl)(amino)carbene). Reduction of a solution ...of 1 in toluene with the reducing agent K/KI led to formation of a deep purple complex that rapidly decomposed. Ball‐milling of 1 with K/KI gave the low‐valent MgI complex (Am)Mg⋅(CAAC) (2) which after rapid extraction with pentane and crystallization was isolated in 15 % yield. Although a benzene solution of 2 decomposes rapidly to give Mg(Am)2 (3) and unidentified products, the radical is stable in the solid state. Its crystal structure shows planar trigonal coordination at Mg. The extremely short Mg−C distance of 2.056(2) Å indicates strong Mg−CAAC bonding. Calculations and EPR measurements show that most of the spin density is in a π* orbital located at the C−N bond in CAAC, leading to significant C−N bond elongation. This is supported by calculated NPA charges in 2: Mg +1.73, CAAC −0.82. Similar metal‐to‐CAAC charge transfer was calculated for M0(CAAC)2 and MI(CAAC)2+ (M=Be, Mg, Ca) complexes in which the metal charges range from +1.50 to +1.70. Although the spin density of the radical is mainly located at the CAAC ligand, complex 2 reacts as a low‐valent MgI complex: reaction with a I2 solution in toluene gave (Am)MgI⋅(CAAC) (1) as the major product.
Ball‐milling of a magnesium iodide precursor with K/KI gave a mononuclear Mg radical which is stabilized by a CAAC ligand. Although stable in the crystalline state, the complex decomposed rapidly in solution. According to calculations and EPR spectroscopy, most of the spin density is localized on the CAAC ligand.
A unique method of bisphenol/bisnaphthol synthesis is being proposed, serendipitously discovered in the course of the careful analysis of an aminophenol methylation reaction. The insightful ...exploration of the synthesis of N- or O-methylated species, originating from functionalized phenols obtained by a conventional strategy, provided the opportunity to discover an unexpected reaction pathway yielding various bisphenols. Sodium complexes were found to be crucial intermediates in the synthetic scenario. Their formation, which is usually an imperceptive step, was substantial for the productive outcome of functional group protection. Thorough exploration revealed an essential structural motif of aminophenolate, necessary for the successful outcome of the reaction, and also enabled establishing the limitations of the new method. The work demonstrated that a slight change in the perspective and close inspection of the synthetic nuances can answer the important question concerning what a specific target-oriented synthesis strategy is lacking.
A series of aminophenolate and aminonaphtholate homoleptic zinc complexes were obtained using a simple and unique synthetic strategy. A rigorous analysis of the byproduct supported modifications of ...the main course of the bis-chelation reaction. Controlled alcoholysis was followed by alternation and controlled anaerobic hydrolysis of ethyl-zinc aminophenolate or aminonaphtholate complexes. This new and intriguing reaction yielded a new class of zinc corona complexes. All the synthesized complexes were fully characterized in the solid state and in solution using X-ray and spectroscopic methods as well as density functional theory calculations.
Low‐valent Mg(I) complexes by ball‐milling Jędrzkiewicz, Dawid; Langer, Jens; Harder, Sjoerd
Zeitschrift für anorganische und allgemeine Chemie (1950),
October 14, 2022, Letnik:
648, Številka:
19
Journal Article
Recenzirano
Odprti dostop
Mechanochemistry has great potential in the syntheses of low‐valent Mg(I) complexes. Magnesium iodide precursors with three different β‐diketiminate (BDI) ligands of varying bulk have been reduced ...with K/KI (or Na/NaCl) using the ball‐mill. Depending on the steric bulk of the ligand, the raw products are intensely colored powders, indicating the presence of (BDI)Mg⋅ radicals. Extraction with pentane gave (BDI)Mg−Mg(BDI) in excellent yields. Reaction of the powder with H2 prior to extraction gave (BDI)MgH2. Extraction with benzene gave (BDI)Mg(C6H6)Mg(BDI) with a dearomatized puckered benzene dianion. Ball‐milling in the presence of triphenylbenzene gave a dinuclear Mg complex with a Ph3C6H3‐dianion which slowly decomposed to (BDI)Mg−Mg(BDI) and Ph3C6H3.
A novel and successful application of ring-closing reactions of aminophenols has been proposed for the formation of a new type of 1,3-benzoxazine ionic derivatives. The optimization of the reaction ...and detailed computational studies have been reported for the estimation of heterocyclic ring stability and its further transformation, which is crucial in the polymerization process. The molecular structure of the obtained compounds has been fully characterized by applying X-ray analysis and spectroscopic methods. The novel benzoxazines undergo an intriguing thermal reaction leading to classical benzoxazines and chloroalkanes, which is the first step of transformation before polymerization. To gain more insights into the transformation behavior of ionic benzoxazine derivatives, the Fourier transform infrared (FT-IR) spectra of gaseous products were recorded in experiments with near simultaneous FT-IR/TGA measurements. The combination of thermogravimetry with FT-IR spectroscopy enables the quantitative and qualitative characterization of thermal transformation products and clarification of the reaction mechanism. The experimental data have been verified by applying DFT(B3LYP) and DFT(M062x) theoretical studies.
A family of homo- and heteroleptic zinc complexes bearing aminonaphtholate ligands was synthesized and fully characterized. Using NMR spectroscopy and DFT calculation, bis-alkoxy-bridged complexes ...LZn(μ-OR)2 were confirmed to have dimeric structures in solution, analogous to those obtained via X-ray crystallography. Surprisingly, a detailed experimental and theoretical study of the catalytic activity of LZn(μ-OR)2 in the ring-opening polymerization (ROP) of lactides showed that although well-defined alkoxy dimers possess a single-site structural motif, the most active initiator is obtained during in situ alcoholysis of the alkylzinc precursor. These results indicate that rational ancillary and alkoxy ligand design that takes into account its mutual interaction on monomer coordination may be key to the synthesis of new high-performance ROP catalysts.
Complex (DIPePBDI)Ca2(C6H6), with a C6H62− dianion bridging two Ca2+ ions, reacts with benzene to yield (DIPePBDI)Ca2(biphenyl) with a bridging biphenyl2− dianion (DIPePBDI=HCC(Me)N‐DIPeP2; ...DIPeP=2,6‐CH(Et)2‐phenyl). The biphenyl complex was also prepared by reacting (DIPePBDI)Ca2(C6H6) with biphenyl or by reduction of (DIPePBDI)CaI2 with KC8 in presence of biphenyl. Benzene‐benzene coupling was also observed when the deep purple product of ball‐milling (DIPPBDI)CaI(THF)2 with K/KI was extracted with benzene (DIPP=2,6‐CH(Me)2‐phenyl) giving crystalline (DIPPBDI)Ca(THF)2(biphenyl) (52 % yield). Reduction of (DIPePBDI)SrI2 with KC8 gave highly labile (DIPePBDI)Sr2(C6H6) as a black powder (61 % yield) which reacts rapidly and selectively with benzene to (DIPePBDI)Sr2(biphenyl). DFT calculations show that the most likely route for biphenyl formation is a pathway in which the C6H62− dianion attacks neutral benzene. This is facilitated by metal‐benzene coordination.
Attempts to isolate low‐valent (BDI)Ae‐Ae(BDI) complexes led to reduction of the benzene solvent and formation of (BDI)Ae‐(C6H6)‐Ae(BDI); BDI=β‐diketiminate ligand, Ae=Ca or Sr. Reaction of bridging C6H62− with benzene gave (biphenyl)2− complexes. Ball‐milling is an efficient synthetic tool for this dehydrogenative benzene‐benzene coupling. Calculations suggest attack of C6H62− at benzene. This is facilitated by Ae2+⋅⋅⋅benzene coordination.
To investigate the effects of (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD), tocopherol polyethylene glycol 1000 succinate (TPGS), sodium desoxycholate ...(SDOCH), trimethyl chitosan (TMC), and sodium caprate (C10) on the plasma concentration and the oral bioavailability of tigecycline in broiler chickens. To test the effects of the excipients on absorption of tigecycline, a tetracycline that is poorly absorbed from the gastrointestinal tract, broiler chickens were used as an animal model. Tigecycline (10 mg/kg body weight) was administered intravenously, orally, and orally with one of the excipients. Plasma samples were taken after administration. To measure tigecycline concentrations, high-performance liquid chromatography coupled with tandem mass spectrometry was used. Compartmental and non-compartmental analyses were used for pharmacokinetic analyses of mean plasma concentrations versus time. With the exception of sodium caprate, all the excipients significantly increased the area under the curve and bioavailability of tigecycline (p < 0.05). These parameters were approximately doubled by HP-β-CD, TPGS, and SDOCH, with 95% confidence intervals (95% CIs) for the difference that included only increases of 1.5-fold or higher (bioavailability: control, 1.67%; HP-β-CD, 3.24%; TPGS, 3.30%; and SDOCH, 3.24%). The increases in these parameters were smaller with DM-β-CD and TMC (DM-β-CD, 2.41%; TMC, 2.55%), and the 95% CIs ranged from close to no difference to nearly double the values in the control group. These results indicate that HP-β-CD, TPGS, and SDOCH substantially increase the area under the curve and oral bioavailability of tigecycline. They suggest that DM-β-CD and TMC may also substantially increase these parameters, but more research is needed for more precise estimates of their effects.
Among the broad palette of POSS hybrids, the mono-functionalized ones can be considered as attractive starting blocks for further structural expansion. In this paper, we report on the poorly known ...group represented by N-containing derivatives which have great potential in many areas of organic and coordination chemistry. By using Buchwald-Hartwig amination, and starting from (3-aminopropyl)hepta(isobutyl)octasilsesquioxane and different aryl bromides, we obtained eight novel mono-substituted amine-POSS derivatives
via
C(sp
2
)-N bond creation. In the next step, selected hybrids were used in metalation reactions by using palladium acetate. The driving force of this reaction is the formation of the metallacycle entity possessing the {PdN-H O-C-O} core, which is built by POSS attached amine fragments and acetate ligands, which points to a non-typical behavior in comparison to the conventional reaction between Pd(OAc)
2
and classical amines. The resulting coordination entities show very good solubility, which is not always possible with fully substituted POSS ligands and, which should be emphasized, is strongly demanded in potential applications,
e.g.
in catalysis. Herein, we report on the first palladium compounds containing mono-functionalized amine-POSS ligands, with a pseudochelate interaction stabilized by a hydrogen bond. For a detailed picture of the stability of the chelate rings maintained by hydrogen bonds, DFT calculations were carried out. Furthermore, the preliminary catalytic behavior of the resulting Pd(
ii
) coordination compounds has been examined in the Suzuki-Miyaura coupling. All the obtained compounds were characterized by using EA, NMR (
1
H,
13
C,
29
Si), and HR-MS.
The unexpected reaction between mono-functionalized amino-POSS and palladium acetate (different from the well-known pathway between a classical amine and a palladium salt) leads to novel coordination entities.
An efficient synthesis strategy of a well-defined polylactide-dye conjugate in a controlled fashion is presented. The introduction of coloring species as end groups of polylactide (PLA) has been ...performed by using new homoleptic aminophenolate magnesium or zinc coordination compounds. The molecular structure of metal complexes has been determined in solution by NMR spectroscopy, and in the solid state by X-ray analysis. Lastingly colored polymers were obtained with 2-4-(Nitrophenylazo)-
-ethylphenylaminoethanol (Disperse Red 1) and 2-4-(2-Chloro-4-nitrophenylazo)-
-ethylphenylaminoethanol (Disperse Red 13) at very high lactide conversions, based on MALDI-ToF measurement, and the macromolecules were nearly fully chain end dye-functionalized. Based on
H NMR, the DP
of conjugates was in the range of 10-300, which was consistent with the reaction setup. Various methods of gel-permeation chromatography (GPC) analysis were applied, and they demonstrated that the number-average molar mass (
) values (polystyrene (PS) standards) were a bit higher than calculated, the molar mass distribution index (Ɖ
) values were moderate to high, the TDA (triple detection array) system was inappropriate for analysis, measurements with PDA (photo diode array) detection at 470 nm gave nearly the same molar mass distributions such as the refractometer, and the relative absorbance of conjugates at 470 nm increased linearly versus (DP
)
. The presented approach connects the gap between the current strategy of obtaining colored polymer fibers and the design of tailor-made initiators with eco polyesters designed for the targeted applications.
PDF
