Alkali Metal Alkoxides Research Articles

Synthesis of alternating polyesters using a dual catalytic system of alkali metal alkoxides and crown ether

In this study, a dual catalytic system that merges crown ether with alkali metal alkoxides (AMA) is utilized in the ring-opening alternating polymerization (ROAP) of phthalic anhydride (PA) and propylene oxide (PO). This method streamlines the production of polyesters characterized by a fully alternating sequence, a modifiable molar mass (achieving up to 59.3 kg mol−1), and a narrow molar mass distribution (ÐM < 1.26). Analysis of various commercially available AMAs, notably sodium ethoxide (EtONa), sodium methoxide, and lithium ethoxide, in tandem with crown ethers (15-crown-5 and 18-crown-6), underscores the superior catalytic efficacy of the EtONa and 18-crown-6 pairing. This heightened efficiency is attributed to the coordination of crown ether with alkali metal ions, thereby boosting the nucleophilicity of terminal alkoxide anions. The methodology has been successfully deployed in the ROAP of PA, norbornene anhydride, and multiple epoxides, while also simplifying the creation of aliphatic–aromatic block polyesters from a mixture of PA, PO, and lactide. This strategy presents a straightforward approach to polyester production, thus making significant contributions to the evolution of polyester synthesis technology.

Synthesis of sustainable sulfur‐containing polycarbonates from xylose and carbonyl sulfide

AbstractHerein, the six‐membered sulfur‐containing cyclic carbonates was successfully synthesized from d‐ and l‐xylose through an environmental friendly process by employing carbonyl sulfide (COS) as a sustainable C1‐carbonation agent. The ring‐opening polymerization of the monomers were rapidly initiated by bifunctional organocatalysts and alkali metal alkoxides, respectively, under ambient reaction conditions. The resultant sulfur‐containing polycarbonates exhibit high‐temperature resistance and good optical properties. This work furnishes an original and practical strategy for utilizing COS as a sulfur feedstock in biopolymer synthesis.

Activation of polar organometallic reagents with alkali-metal alkoxides

The use of group 1 metal alkoxides as additives to activate s-block organometallics is an established phenomenon in polar organometallic chemistry. Typified by the Lochmann–Schlosser superbase, these reagents have proved to be exceptionally powerful bases for the deprotonative metallation of organic substrates. However, despite their long-standing importance in synthesis, the nature of this activating effect remains to be fully understood. Here we shed light on the origins of the special reactivities of which these reagents are capable, which generally cannot be replicated by their homometallic precursors. In addition, reactivity studies that have established the mixed-metal constitutions of these organometallic reagents are discussed. Opening up new directions in synthesis, the use of lithium alkoxides as additives to promote direct regioselective magnesium (or zinc)/halogen exchange processes to access highly functionalized organometallics is also discussed, with an emphasis on rationalizing the role of each metal in these transformations.

Assessing Alkali-Metal Effects in the Structures and Reactivity of Mixed-Ligand Alkyl/Alkoxide Alkali-Metal Magnesiates.

Advancing the understanding of using alkali‐metal alkoxides as additives to organomagnesium reagents in Mg−Br exchange reactions, a homologous series of mixed‐ligand alkyl/alkoxide alkali‐metal magnesiates [MMg(CH2SiMe3)2(dmem)]2 [dmem=2‐{[2‐(dimethylamino)ethyl]methylamino} ethoxide; M=Li, 1; Na, 2; (THF)K, 3] has been prepared. Structural and spectroscopic studies have established the constitutions of these heteroleptic/heterometallic species, which are retained in arene solution. Evaluation of their reactivity towards 2‐bromoanisole has uncovered a marked alkali‐metal effect with potassium magnesiate 3 being the most efficient of the three ate reagents. Studies probing the constitution of the exchange product from this reaction suggest that the putative [KMgAr2(dmem)]2 (Ar=o‐OMe−C6H4) intermediate undergoes redistribution into its single metal components [KAr]n and [MgAr(dmem)]2 (5). This process can be circumvented by using a different potassium alkoxide containing an aliphatic chain such as KOR’ (R’=2‐ethylhexyl) which undergoes co‐complexation with Mg(CH2SiMe3) to give [KMg(CH2SiMe3)2(OR’)]2 (7). This ate, in turn, reacts quantitatively with 2‐bromoanisole furnishing [KMgAr2(OR’)]2 (9) which is stable in solution as a bimetallic compound. Collectively this work highlights the complexity of these alkali‐metal mediated Mg−Br exchange reactions, where each reaction component can have a profound effect not only on the success of the reaction; but also the stability of the final metalated intermediates prior to their electrophilic interception.

Iodine and alkali metal alkoxides: a simple and versatile catalytic system for fully alternating polyester synthesis from phthalic anhydride and epoxides

Regioselective ROCOP of various epoxides with phthalic anhydride using readily available and economical catalysts i.e. I2 in combination with alkali metal alkoxides was used.

Pentamethylcyclopentadienyl Complexes of Cerium(IV): Synthesis, Reactivity, and Electrochemistry.

Treatment of Cp*2CeCl2K(THF) with alkali-metal alkoxides and siloxides in the presence of hexachloroethane generates the monomeric bis(pentamethylcyclopentadienyl) cerium(IV) complexes Cp*2Ce(OR)2 (Cp* = C5Me5; R = Et, iPr, CH2tBu, tBu, SiMe3, or SiPh3). Large substituents R trigger ligand scrambling to half-sandwich complexes Cp*Ce(OR)3, which could be isolated for R = tBu and SiPh3. Similar reactions with sodium aryloxide NaOAr (OAr = OC6H3iPr2-2,6) led to Cp*2Ce(OAr)Cl. Treatment of tris(cyclopentadienyl) complexes CpR3CeCl (CpH = Cp = C5H5; CpMe = C5H4Me) with NaOAr afforded CpMe2Ce(OAr)2 and Cp3Ce(OAr). The cerium(IV) complexes display a pseudotetrahedral geometry in the solid state. Cyclic voltammetry revealed mostly chemically reversible as well as electrochemically quasi-reversible redox processes with potentials ranging from -0.84 to -1.61 V versus Fc/Fc+. Switching from sandwich to half-sandwich complexes decreased the electrochemical potentials drastically, showing better stabilization of the cerium(IV) center in the case of Cp*Ce(OR)3 than in the case of Cp*2Ce(OR)2. Enhanced stabilization of the cerium +IV oxidation state could be further demonstrated in the series alkoxy > siloxy > aryloxy as well as C5Me5 > C5HMe4.

Alkali Metal Alkoxides in Noyori‐Type Hydrogenations

AbstractThis minireview discusses the accelerative role of alkali metal alkoxides in two important catalytic processes: hydrogenation of ketones and esters with Noyori‐type molecular catalysts. Here I offer my perspective on the unique mechanistic aspects of these reactions – a subject that remains controversial and often misunderstood.

Endohedral Mixed Aggregates: Sodium Alkoxide Cages with Organic or Inorganic Central Anions and Variable Hull.

Alkali metal alkoxides are widely used in chemistry due to their Brønsted basic and nucleophilic properties. Potassium alkoxides assist alkyllithium in the metalation of hydrocarbons in Lochmann‐Schlosser‐bases. Both compounds form mixed aggregates, which enhance the thermal stability, solubility, and the basic reactivity of these mixtures. A very unusual spherical mixed alkoxy aggregate was discovered by Grützmacher et al., where a central dihydrogen phosphide anion is surrounded by a highly dynamic shell of thirteen sodium atoms and a hull of twelve tert‐butoxide groups. This structural motif can be reproduced by a reaction of trimethylsilyl compounds of methane, halogens, or pseudo‐halogens with excess sodium tert‐butoxide. A nucleophilic substitution releases the corresponding anion, which is then encapsulated by the sodium alkoxide units. The compounds are soluble in hydrocarbon solvents, enabling studies of solutions by high‐resolution NMR spectroscopy and IR/Raman studies of the crystalline materials.

Polyesteramides Based on Linseed and Safflower Oils for Protective Coatings

Polyesteramide resins were obtained and evaluated as vehicles and the variations of film performance in relation to the amide linkage were studied. Treatment of either linseed or safflower oils with diethanolamine with catalytic amounts of alkali metal alkoxide under relatively mild conditions led to a substantially complete conversion to N,N-(hydroxyethyl) linseed amide (HELA) and N,N-(hydroxyethyl) safflower amide (HESA). Polymerization of the polyols with diadipyl aromatic amines (aniline, p-toluidine, p-aminophenol and p-aminobenzoic acid) was carried out to yield polyesteramide derivatives having interesting surface coating properties. Such a substitution was claimed to give much harder, tougher, more flexible films with excellent chemical resistance in comparison with alkyd resins of similar oil length. The study includes stoving films mechanical evaluation as gloss percent at 60ºC, adhesion, impact, pencil hardness and bending tests using mild steel plates. The films also possess excellent impact resistance, high scratch hardness values, excellent bending test and good adhesion.

Solvent-Free Glycidyl Carbamate Oligomerization and Solvent Affinity of Oligomers

Polyglycerols are a class of multifunctional polymers obtained from the polymerization of glycidol and its derivatives. Unlike poly(ethylene glycol) (PEG), which is the most common polyether, polyglycerols can exhibit many functionalities on their side chains and can be obtained from renewable resources, mainly glycerol. Hereby, this study will focus on glycidyl carbamates, a new class of monomers readily available from glycerol carbonate, which combines the chemical functionalities of both glycidol and urethane. The polymerization of these glycidyl ethers directly leads to linear poly(glycidyl carbamates), thus avoiding several protection and deprotection steps of the monomers or polymers. This study hence gives a first approach to glycidyl carbamate polymerization. Commonly used initiators in anionic ring-opening polymerization (alkali metal alkoxides) lead to ill-defined compounds after full conversion of the monomers, whereas pyridine derivative initiators lead to oligomers whose structures could be thoroughly described. The results suggest that low basicity and high nucleophilicity are the most suitable conditions to polymerize glycidyl carbamates because of the sensitivity of the urethane moiety. Additionally, a study of the obtained poly(glycidyl carbamates) affinity toward the solvent has been conducted to further describe the properties of these novel original polyethers.

Anionic polymerization of butadiene by dialkylmagnesium / alkali metal alkoxide systems in apolar medium: Polybutadiene microstructure and polymerization control

Lithium based anionic polymerization of butadiene in apolar media allows the obtention of polybutadiene with a high vinyl content by using polar modifier or alkali metal alkoxide. For instance, butadiene polymerization with alkyllithium and potassium tert-pentoxide produces polybutadiene with 50% of vinyl content. The aim of this paper is to develop an approach without any alkyllithium moieties in order to synthesize polybutadiene with a high vinyl content (50%–70%) in a controlled way. To do so bi-metallic systems based on di-n-butylmagnesium in association with potassium or sodium tert-pentoxide were studied in apolar medium. The influence of parameters such as the initiator preformation time and the [Mt]/[Mg] ratio were assessed (Mt = K, Na). The potassium tert-pentoxide-based system was found to produce polybutadienes in a controlled way with 50% of vinyl content, while polybutadienes with up to 70% of vinyl content were obtained in a controlled way with Na based systems.

Ring-opening (co)polymerization of six-membered substituted δ-valerolactones with alkali metal alkoxides

The ring-opening polymerization (ROP) of bio-derived six-membered (substituted) δ-valerolactones, including the 5-Me substituted δ-valerolactone (aka δ-hexalactone (HL)), 2-ethylidene-6-hepten-5-olide (EVL), 2-ethylheptane-5-olide (EHO) and the novel 2-ethylidene-6-heptan-5-olide (MH), is investigated. In comparison to the ubiquitous unsubstituted δ-valerolactone (VL), the presence of a substituent on the lactone ring appears to significantly affect the polymerizability of the monomer, whichever the catalyst/initiator system or the operating conditions. Typical Brönsted acids, organocatalysts or Lewis acidic metal complexes revealed hardly active in the ROP of HL, most likely originating from polymerization/depolymerization issues. Better efficiency was achieved from alkali metal complexes, especially using NaOMe (1–2.5 mol%) from which high-to-quantitative HL conversion was reached within 18 h at 60 °C. Oligomers (M̅n,NMR ≤ 3800 g mol−1, ÐM = 1.22–1.36) were thus synthesized from ROP, as supported by NMR spectroscopy, SEC and MALDI-ToF mass spectrometry analyses. P(HL-co-VL) random copolymers incorporating up to 44 mol% of HL into PVL were next synthesized from the simultaneous HL/VL copolymerization mediated by NaOMe (M̅n,NMR up to 9700 g mol−1, ÐM = 1.21–1.40). The ROP of the sustainable CO2/butadiene-derived EVL, EHO or MH –the original semi-hydrogenated parent lactone–, remained unsuccessful, regardless of the catalytic system.

Self-templated formation of (NiCo)9S8 yolk-shelled spheres for high-performance hybrid supercapacitors.

Rational materials design for the synthesis of desirable hollow micro- and nanostructures has recently revealed the remarkable potential for high-performance energy storage and conversion devices. Owing to their unique "core-void-shell" structural configurations, yolk-shell-structured electrode materials can achieve intimate contact with the electrolyte and alleviate the volume expansion issue during electrochemical cycling, which is therefore poised to further boost the electrochemical properties of hybrid supercapacitors. Herein, a facile self-templated strategy, consisting of a hydrothermal step and a high-temperature sulfurization process, has been developed for the construction of yolk-shell (NiCo)9S8 spheres in situ coated by graphite carbon ((NiCo)9S8/GC) due to the non-equilibrium thermal treatment of alkali metal alkoxides. The as-synthesized yolk-shelled sphere exhibits a high specific capacitance of 1434.4 F g-1 (179.3 mA h g-1) at a current density of 1 A g-1, and good rate capability and cycling stability with 83.1% capacitance retention at 8 A g-1 over 5000 cycles. To further demonstrate its practical application, a hybrid supercapacitor device was assembled using (NiCo)9S8/GC as the battery-type positive electrode and activated carbon (AC) as the capacitive-type electrode. The as-fabricated device can reach a wide voltage window of up to 1.6 V, deliver a high energy density of 55.6 W h kg-1 at a power density of 800.3 W kg-1 and maintain 90.2% of specific capacitance after 3000 cycles.

Synthesis, structures and reduction chemistry of monophthalocyanine scandium hydroxides

The preparation and structural characterization of a pair of scandium(III) phthalocyanine hydroxide complexes were achieved by reaction of PcScCl with alkali metal alkoxides, likely via hydrolysis of soluble PcSc-alkoxide intermediates. A Sc[Formula: see text]Li[Formula: see text]-OH)[Formula: see text] cubane supported by two distorted Pc rings of the form (PcSc)[Formula: see text]-OH)[Formula: see text]Li[Formula: see text](THF)(DME) was isolated from the reaction of PcScCl with LiO[Formula: see text]Pr, while a simpler alkali-metal-free [Pc[Formula: see text]Sc[Formula: see text]-OH)[Formula: see text](THF)] was obtained from addition of NaO[Formula: see text]Bu; both structures are reminiscent of bent metallocenes, with dihedral angles between the two Pc rings of 50.8 and 37.7[Formula: see text]respectively. A soluble PcScOH material can also be obtained directly via hydrolysis of insoluble PcScCl in approximately 95:5 THF:water. Reduction of the Pc ring of PcScCl using KC[Formula: see text] is reversible and generates Pc[Formula: see text] and Pc[Formula: see text]-containing materials that were characterized via UV-vis spectroscopy and, where appropriate EPR and [Formula: see text]H NMR spectroscopy; analogous reductions of the PcScOH-based species were irreversible. Exposure of the air-sensitive, reduced PcScCl-based species to ambient atmosphere generated PcScOH materials analogous to the direct hydrolysis route.

Anionic Polymerization of Butadiene Using Lithium/Potassium Multi-metallic Systems: Influence on Polymerization Control and Polybutadiene Microstructure

Thermal, mechanical, and viscoelastic properties of polybutadiene-based rubber materials are highly dependent on polybutadiene microstructure. The use of polar modifier in association with alkyllithium is a well-known method to obtain polybutadiene with a high vinyl content. Another approach is to use bimetallic initiating species such as alkyllithium combined to heavier alkali metal alkoxide (RONa, ROK…). The polymerization control is nevertheless not achieved and several parameters were found to influence it. Using bimetallic initiating systems based on alkyllithium and a potassium alkoxide, alkyllithium structure, initiator preformation time, and initiator composition were identified as parameters influencing the anionic polymerization process of butadiene and/or polybutadiene microstructure. In addition, the use of trimetallic systems based on alkyllithium, potassium alkoxide, and alkylaluminum was investigated in order to prevent side reactions regardless of the [K]/[Li] ratio and of the initiator preformation time.

Callery strikes out on its own

On Mars-Evans City Road outside Pittsburgh in rural Evans City, Pennsylvania, a sign informs drivers that litter cleanup is sponsored by BASF. True for 13 years, it’s no longer the case. Litter removal is now in the hands of Callery, the revived name for a chemical facility set back on that quiet stretch of road. BASF, the world’s largest chemical company, acquired Callery in 2003 from Mine Safety Appliances (MSA) with big plans to grow it, but in the end it achieved little. Now a small, stand-alone operation controlled by private investors, Callery is out to prove that growth is still very much possible. When BASF paid $65 million for Callery, its executives were no doubt intrigued by the unique Evans City site. Callery calls itself the world’s largest producer of both alkali metal alkoxides and specialty borane complexes. Both types of chemicals are typically used by Callery’s customers as

The Unanticipated Catalytic Activity of Lithium tert-Butoxide/THF in the Interesterification of Rapeseed Oil with Methyl Acetate

Conventionally, the biodiesel (mixture of fatty acid methyl esters, FAME) production proceeds by transesterification of triglycerides with methanol accordingly by the formation of glycerol as a by-product, which cannot be included in biofuel composition. Biodiesel could also be produced via interesterification ensuring full conversion of oil to biofuel, consisting of FAME and triacetin. The most effective catalysts for interesterification reactions are alkali metal alkoxides. The effectivity of alkoxide catalyst depends on its solubility determined by the structure of the alkyl chain. In our previous studies, we have shown that the branched chain catalyst tert-BuOK/THF is highly suitable for the realisation of interesterification reactions. Till now, in the scientific literature, very little is known about the influence of metal ions. In order to investigate the influence of counterion on the activity of alkoxide catalysts, in this work, we have investigated the proceeding of interesterification reactions of rapeseed oil with methyl acetate in the presence of lithium, sodium, and potassium tert-butoxides in THF. Experimentally obtained relationships for catalyst-to-oil molar ratio (COMR) influence rapeseed oil interesterifications with methyl acetate at 55°C for 1 h, with methyl acetate-to-oil molar ratio (MAOMR) 18 showing that the tert-BuONa/THF and tert-BuOK/THF have high and similar activity, but the tert-BuOLi/THF is fundamentally different. The low and diverse activity of lithium tert-butoxide can be explained by the association of ions and very low catalytic activity of ion pairs. Simulation of the influence of association on the FAME formation shows that at COMR 0.1 (sufficient for fast reaction proceeding in the presence of tert-BuONa/THF and tert-BuOK/THF), the concentration of tert-butoxide ions in the presence of tert-BuOLi/THF because of associations lowers from 28 mmol/L to 13 mmol/L, whcih is not sufficient for effective proceeding of reaction. Activity of alkoxides in this reaction is solely determined by the counterion.

The catalytic activity of alkali metal alkoxides and titanium alkoxides in the hydrosilylation of unfunctionalized olefins

The catalytic activities of titanium alkoxides and alkali metal alkoxides for hydrosilylation of unfunctionalized olefins have been studied. Titanium(IV) alkoxides showed excellent catalytic activity, while alkali metal alkoxides have low catalytic activity for the hydrosilylation of olefins. However, by using titanocene dichloride as an additive, alkali metal alkoxides showed also excellent catalytic property for hydrosilylation. In comparison with titanium alkoxides, no α-adduct was obtained by using alkali metal alkoxides/Cp2TiCl2 as catalysts.

SOLUBILITY IN ALCOHOLS AND ALCOHOLYSIS REACTIONS OF CARBONATES, SULFIDES, CYANIDES, AND PHOSPHATES OF ALKALI METALS

The published data on the solubilities of lithium, sodium, potassium, rubidium and cesium carbonates; sodium bicarbonate; sodium sulphide; potassium and sodium cyanides; orthophosphates, hydro- and dihydroorthophosphates of potassium and sodium, as well as sodium pyrophosphate in methanol, ethanol, 2-propanol, 2-methyl-1-propanol, benzyl alcohol, ethylene glycol, methyl cellosolve and glycerol have been considered and collected. A little bit information for salts has been taken from the most common solubility handbooks, but most of data was selected from scientific articles. There is an acid-base equilibrium with the formation of the corresponding alcoholates in the systems "potassium or sodium carbonate/methanol, ethanol, ethylene glycol, ethylene glycol monomethyl ether", "sodium sulphide/methanol, ethanol, 2-propanol, 2-methyl-1-pro-panol, benzyl alcohol", "potassium cyanide/methanol, ethylene glycol, glycerol", "potassium or sodium orthophosphate/ethylene glycol", and "sodium pyrophosphate/ethylene glycol". The mechanism of the reaction of alcoholysis and the formation of alcoholates from the alkali metal salts and alcohols is based on the distribution of the components in phases. Analysis of all phases in the alcohol solutions of alkali metal salts proved the presence of an alcoholysis reaction in some salt/alcohol systems. The concentrations of dissolved salts in alcoholate-generating systems are significantly lower than those determined by the gravimetric method without taking into account the alcoholysis reaction and are considered in the common handbooks "solubilities of the corresponding salts in alcohols". A classification of inorganic alkali metal salts reacting with alcohols in the alcoholysis reaction has been proposed. The analysis of literature data showed that along hydroxides and alkali metal salts, the hydrides, organometallic compounds, acetylenides, nitrides, amides (including alkyl amides) as well as azides can react with alcohols to form alkoxides by alcoholysis reaction. Alcoholysis of salts can be considered as a promising method for the production of alkali metal alkoxides in which the salt is used instead of metal or hydroxide.

Cover Picture: Anionic Copolymerization of Carbonyl Sulfide with Epoxides via Alkali Metal Alkoxides (Chin. J. Chem. 7/2018)

The cover picture shows a protocol of an anionic copolymerization of carbonyl sulfide (COS) with epoxides via alkali metal alkoxides. COS is an analogue of carbon dioxide (CO2), and can be converted to CO2 via the carbonic anhydride enzymes widely existing in nature. It causes acid rain, ozonosphere damage and haze by a series of photochemical reactions. Very simple and low‐cost alkali metal alkoxides are shown as effective catalysts, affording highly transparent poly(monothiocarbonate)s with 100% alternating degree, &gt;99% tail‐to‐head (T‐H) content, high number‐average molecular weights with narrow molecular weight distributions. This is an environment‐friendly and atom‐economic process for making sulfur‐containing polymers. More details are discussed in the article by Zhang et al. on page 625–629. image