Zinc Complexes Supported by Maltolato Ligands: Synthesis, Structure, Solution Behavior, and Application in Ring-Opening Polymerization of Lactides

A series of novel zinc alkoxides supported by chelating maltolato (MalO; MalOH = maltol) ligands were successfully synthesized and characterized. Reaction of MalOH with ZnEt₂ (3:4) gives a trinuclear cluster [Zn₃(Et)₂(MalO)₄] (<b>1</b>), which spontaneously disproportionates in solution to mononuclear species [Zn­(MalO)₂] (<b>1a</b>) and [Zn­(Et)­(MalO)] (<b>1b</b>); (<b>1a</b>) and (<b>1b</b>) form [Zn­(MalO)₂(py)] (<b>2</b>), [Zn­(Et)­(MalO)­(py)] (<b>3</b>), [Zn­(MalO)₂]₂ (<b>(1a)₂</b>), [Zn­(MalO)­(OBn)]₂ (<b>(1c)₂</b>), and [Zn₄(Et)₂(OEt)₂(MalO)₄] (<b>4</b>) on addition of pyridine, benzyl alcohol (BnOH), or dry O₂, respectively. Compounds <b>1</b>, <b>2</b>, <b>(1a)</b>_<b>2</b>, and <b>4</b> were characterized by elemental analysis, NMR, ESI-MS, and single-crystal X-ray structural analysis. Variable-temperature NMR experiments showed that <b>(1a)</b>_<b>2</b> and <b>(1c)</b>_<b>2</b> are in equilibrium with the monomeric form in solution. The addition of l-lactide (l-LA) to a combination of <b>1</b> and 2 equiv of BnOH in dichloromethane at room temperature in different molar ratios leads to rapid and efficient generation of poly­(l-LA) with end-capped BnO groups. According to kinetic studies, propagation by [Zn­(OBn)­(MalO)] (<b>1c</b>) is first-order with respect to both the monomer and <b>1c</b> concentrations; <b>1a</b> in ring-opening polymerization of l-LA shows no activity. These results suggest a single-site active species in the ring-opening polymerization of l-LA

Zinc Complexes Supported by Maltolato Ligands: Synthesis, Structure, Solution Behavior, and Application in Ring-Opening Polymerization of Lactides

A series of novel zinc alkoxides supported by chelating maltolato (MalO; MalOH = maltol) ligands were successfully synthesized and characterized. Reaction of MalOH with ZnEt₂ (3:4) gives a trinuclear cluster [Zn₃(Et)₂(MalO)₄] (<b>1</b>), which spontaneously disproportionates in solution to mononuclear species [Zn­(MalO)₂] (<b>1a</b>) and [Zn­(Et)­(MalO)] (<b>1b</b>); (<b>1a</b>) and (<b>1b</b>) form [Zn­(MalO)₂(py)] (<b>2</b>), [Zn­(Et)­(MalO)­(py)] (<b>3</b>), [Zn­(MalO)₂]₂ (<b>(1a)₂</b>), [Zn­(MalO)­(OBn)]₂ (<b>(1c)₂</b>), and [Zn₄(Et)₂(OEt)₂(MalO)₄] (<b>4</b>) on addition of pyridine, benzyl alcohol (BnOH), or dry O₂, respectively. Compounds <b>1</b>, <b>2</b>, <b>(1a)</b>_<b>2</b>, and <b>4</b> were characterized by elemental analysis, NMR, ESI-MS, and single-crystal X-ray structural analysis. Variable-temperature NMR experiments showed that <b>(1a)</b>_<b>2</b> and <b>(1c)</b>_<b>2</b> are in equilibrium with the monomeric form in solution. The addition of l-lactide (l-LA) to a combination of <b>1</b> and 2 equiv of BnOH in dichloromethane at room temperature in different molar ratios leads to rapid and efficient generation of poly­(l-LA) with end-capped BnO groups. According to kinetic studies, propagation by [Zn­(OBn)­(MalO)] (<b>1c</b>) is first-order with respect to both the monomer and <b>1c</b> concentrations; <b>1a</b> in ring-opening polymerization of l-LA shows no activity. These results suggest a single-site active species in the ring-opening polymerization of l-LA

Solvothermal Alcoholysis Routes for Recycling Polylactide Waste as Lactic Acid Esters

In this work, we investigated the possible use of polylactide (PLA), a biodegradable polymer obtained from renewable biofeedstock, to produce a range of industrially useful lactic acid esters. We describe a simple and convenient solvothermal alcoholysis method for large-scale recycling of PLA resins or residues from disposable packaging in the presence of the appropriate alcohol under catalyst-free or catalytic conditions. This process proceeds easily both without and with a catalyst. The results show that the best catalytic activities involve magnesium and calcium alkoxides synthesized in situ from organometallic or metallic precursors and an alcohol. We determined the crystal structure of the chiral mononuclear postcatalyst [Ca­(LAc)₂(EL)₂] (<b>1</b>; LAc = lactic acid anion, EL = ethyl lactate), obtained directly from the reactor. Particular emphasis is placed on the operating conditions and high activity of the catalyst used. Key factors that affect the catalytic activity and reaction mechanism are also highlighted

Synthesis of Aluminosilicates Containing a Ba(Sr)–O–Al–O–Si Arrangement of Natural Feldspar Mineral

We report a facile route to multicomponent complexes of [M­{(μ-ddbfo)₂Al­(OSiR₃)₂}₂] (M = Ba, Sr; ddbfoH = 2,3-dihydro-2,2-dimethylbenzofuran-7-ol; R = Ph, O^tBu) as new efficient single-source routes to barium and strontium celsian feldspar Ba­(Sr)­Al₂Si₂O₈. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. These compounds calcined at 1100 °C to give porous material Ba­(Sr)­Al₂Si₂O₈·2SiO₂ as an amorphous silica matrix containing spherical oxide nanocrystals of celsian feldspar of ca. 5 nm diameter, as evidenced by transmission and scanning electron microscopies

Synthesis of Aluminosilicates Containing a Ba(Sr)–O–Al–O–Si Arrangement of Natural Feldspar Mineral

We report a facile route to multicomponent complexes of [M­{(μ-ddbfo)₂Al­(OSiR₃)₂}₂] (M = Ba, Sr; ddbfoH = 2,3-dihydro-2,2-dimethylbenzofuran-7-ol; R = Ph, O^tBu) as new efficient single-source routes to barium and strontium celsian feldspar Ba­(Sr)­Al₂Si₂O₈. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. These compounds calcined at 1100 °C to give porous material Ba­(Sr)­Al₂Si₂O₈·2SiO₂ as an amorphous silica matrix containing spherical oxide nanocrystals of celsian feldspar of ca. 5 nm diameter, as evidenced by transmission and scanning electron microscopies

Impact of Group 13 Metals on Cp₂TiCl₂ Reduction and Structural Characterization of Resulting Compounds

The aim of the current study was to examine the effects of group 13 metals on Cp₂TiCl₂ reduction in the presence of 2-methoxy­ethanol (MeO­Et­OH) or ethanol (EtOH) and the compositions of the resulting products. Direct reaction of Cp₂TiCl₂ and M [Al, Al (Fe contaminated), Ga, In] in toluene/​alcohol for 2 h gave a new family of uncommon homo- and heterometallic compounds: [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Ti₂­(μ,η²-OEt­OMe)₃­(η²-OEt­OMe)₂­Cl₄] (<b>1</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]Cl (<b>2</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Cp₂Ti­(η²-HOEt­OMe)]­[FeCl₄] (<b>3</b>), [Cp₂Ti­(η²-HOEt­OMe)]­[Ga₂Cl₆]_0.25­[Cl]_0.5 (<b>4</b>), [Cp₃Ti₂­(μ-OEt)₂­(OEt)]­[GaCl₄] (<b>5</b>), [CpTi­(μ,η²-OEt­OMe)­Cl]₂ (<b>6</b>), and [Cp₃Ti₂­(μ,η²-OEt­OMe)­(μ-OEt­OMe)­Cl] (<b>7</b>). The reaction with indium for 48 h resulted in isolation of [TiIn₂­(μ,η²-OEt­OMe)₄­(OEt­OMe)₂­Cl₄] (<b>8</b>), [In₂­(μ-OEt­OMe)₂­(HOEt­OMe)₄­Cl₄]₂ (<b>9</b>), and [Ti­(OEt­OMe)₄] (<b>10</b>). The complexes were characterized using elemental analysis, IR and NMR spectroscopies, and, for <b>1</b>–<b>9</b>, single-crystal X-ray diffraction. The use of metallic gallium and indium to reduce Cp₂­TiCl₂ opens up a previously unexplored path that may provide access to novel and unique compounds

Impact of Group 13 Metals on Cp₂TiCl₂ Reduction and Structural Characterization of Resulting Compounds

The aim of the current study was to examine the effects of group 13 metals on Cp₂TiCl₂ reduction in the presence of 2-methoxy­ethanol (MeO­Et­OH) or ethanol (EtOH) and the compositions of the resulting products. Direct reaction of Cp₂TiCl₂ and M [Al, Al (Fe contaminated), Ga, In] in toluene/​alcohol for 2 h gave a new family of uncommon homo- and heterometallic compounds: [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Ti₂­(μ,η²-OEt­OMe)₃­(η²-OEt­OMe)₂­Cl₄] (<b>1</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]Cl (<b>2</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Cp₂Ti­(η²-HOEt­OMe)]­[FeCl₄] (<b>3</b>), [Cp₂Ti­(η²-HOEt­OMe)]­[Ga₂Cl₆]_0.25­[Cl]_0.5 (<b>4</b>), [Cp₃Ti₂­(μ-OEt)₂­(OEt)]­[GaCl₄] (<b>5</b>), [CpTi­(μ,η²-OEt­OMe)­Cl]₂ (<b>6</b>), and [Cp₃Ti₂­(μ,η²-OEt­OMe)­(μ-OEt­OMe)­Cl] (<b>7</b>). The reaction with indium for 48 h resulted in isolation of [TiIn₂­(μ,η²-OEt­OMe)₄­(OEt­OMe)₂­Cl₄] (<b>8</b>), [In₂­(μ-OEt­OMe)₂­(HOEt­OMe)₄­Cl₄]₂ (<b>9</b>), and [Ti­(OEt­OMe)₄] (<b>10</b>). The complexes were characterized using elemental analysis, IR and NMR spectroscopies, and, for <b>1</b>–<b>9</b>, single-crystal X-ray diffraction. The use of metallic gallium and indium to reduce Cp₂­TiCl₂ opens up a previously unexplored path that may provide access to novel and unique compounds

Synthesis and Structural Characterization of Magnesium Drug Complexes: Efficient Initiators for Forming Polylactide–Drug Conjugates

Five novel magnesium alkoxides supported by drug chelating agents <i>pridinolum</i> (PriOH = 1,1-diphenyl-3-(1-piperidinyl)-1-propanol) and <i>venlafaxinum</i> (VenlOH = (<i>RS</i>)-1-[2-dimethylamino-1-(4-methoxyphenyl)-ethyl]­cyclohexanol) were successfully synthesized and characterized. Direct reaction of PriOH and VenlOH with MgBu₂ (1:1) in toluene gives the dimeric compounds [Mg­(μ,η²-OPri)^<i>n</i>Bu]₂ (<b>1</b>) and [Mg­(μ,η²-VenlO)^<i>n</i>Bu]₂ (<b>2</b>), respectively. Furthermore, the crystallization of an equimolar mixture of <b>1</b> and <b>2</b> in toluene yields heteroleptic magnesium complex [Mg­(μ,η²-OVenl)­(η¹-OPri)]₂ (<b>3</b>). Moreover, reactions of <b>1</b> and <b>2</b> with 2 molar equivs of the corresponding drug–ligands give the homoleptic magnesium bis-alkoxides [Mg­(μ,η²-OPri)­(η¹-OPri)]₂ (<b>4</b>) and [Mg­(μ,η²-OVenl)­(η¹-OVenl)]₂ (<b>5</b>). The treatment of compound <b>1</b> with 2 equivs of VenlOH or <b>2</b> with 2 equivs of PriOH leads to the formation of <b>3</b>. Complexes <b>1</b>–<b>5</b> were characterized by elemental analysis, nuclear magnetic resonance, and single crystal X-ray diffraction (for <b>1</b>–<b>4</b>). It was found that complexes <b>1</b>–<b>5</b> are efficient initiators of the ring-opening polymerization of l-LA, yielding PLA-OPri and PLA-OVenl conjugates, respectively. Moreover, the ring-opening polymerization of l-LA initiated by <b>3</b> led to the simultaneous generation of a blend of poly-l-lactide conjugates with end-capped VenlO and PriO groups

Synthesis of Functionalized Materials Using Aryloxo-Organometallic Compounds toward Spinel-like MM′₂O₄ (M = Ba²⁺, Sr²⁺; M′ = In³⁺, Al³⁺) Double Oxides

The predesigned single-source precursors [Ba­{(μ-ddbfo)₂InMe₂}₂] (<b>1</b>), [Me₂In­(μ-ddbfo)]₂ (<b>2</b>), [Sr­{(μ-ddbfo)₂AlMe₂}₂] (<b>4</b>), and [Me₂Al­(μ-ddbfo)]₂ (<b>5</b>) (ddbfoH = 2,3-dihydro-2,2-dimethylbenzofuran-7-ol) for spinel-like double oxides and group 13 oxide materials were prepared via the direct reaction of the homoleptic aryloxide [M­(ddbfoH)₄]­(ddbfo)₂·ddbfoH (M = Ba²⁺, Sr²⁺ (<b>3</b>)) and InMe₃ or AlMe₃ in toluene. In all of the reactions, there was an organometallic-driven abstraction of the OH protons from the 7-benzofuranols in the Ba²⁺ and Sr²⁺ cation sphere. All compounds were characterized by elemental analysis, ¹H NMR, and FT-IR spectroscopy. In addition, the molecular structures of <b>1</b>, <b>2</b>, and <b>3</b> were determined by single-crystal X-ray diffraction. The oxide products derived from the compounds mentioned above were studied using elemental analysis, Raman spectroscopy, X-ray powder diffraction, and scanning and transmission electron microscopy equipped with an energy-dispersive spectrometer. Moreover, their specific surface area and mesopore size distribution were evaluated using nitrogen porosimetry. Preliminary investigations of the Eu-doped SrAl₂O₄ and In₂O₃ phosphors revealed that the oxides obtained could be considered as matrices for lanthanide ions

Synthesis of Functionalized Materials Using Aryloxo-Organometallic Compounds toward Spinel-like MM′₂O₄ (M = Ba²⁺, Sr²⁺; M′ = In³⁺, Al³⁺) Double Oxides

The predesigned single-source precursors [Ba­{(μ-ddbfo)₂InMe₂}₂] (<b>1</b>), [Me₂In­(μ-ddbfo)]₂ (<b>2</b>), [Sr­{(μ-ddbfo)₂AlMe₂}₂] (<b>4</b>), and [Me₂Al­(μ-ddbfo)]₂ (<b>5</b>) (ddbfoH = 2,3-dihydro-2,2-dimethylbenzofuran-7-ol) for spinel-like double oxides and group 13 oxide materials were prepared via the direct reaction of the homoleptic aryloxide [M­(ddbfoH)₄]­(ddbfo)₂·ddbfoH (M = Ba²⁺, Sr²⁺ (<b>3</b>)) and InMe₃ or AlMe₃ in toluene. In all of the reactions, there was an organometallic-driven abstraction of the OH protons from the 7-benzofuranols in the Ba²⁺ and Sr²⁺ cation sphere. All compounds were characterized by elemental analysis, ¹H NMR, and FT-IR spectroscopy. In addition, the molecular structures of <b>1</b>, <b>2</b>, and <b>3</b> were determined by single-crystal X-ray diffraction. The oxide products derived from the compounds mentioned above were studied using elemental analysis, Raman spectroscopy, X-ray powder diffraction, and scanning and transmission electron microscopy equipped with an energy-dispersive spectrometer. Moreover, their specific surface area and mesopore size distribution were evaluated using nitrogen porosimetry. Preliminary investigations of the Eu-doped SrAl₂O₄ and In₂O₃ phosphors revealed that the oxides obtained could be considered as matrices for lanthanide ions