Calcium Complexes Research Articles

A calcium delivery system fabricated by poly-γ-glutamic acid: Preparation, characterization, and delivery mechanism studies

Calcium has limited bioavailability owing to the formation of calcium phosphate deposits in the gastrointestinal tract. In this study, a polyglutamic acid (PGA)-Ca complex of calcium chelate was prepared using γ-PGA. The binding constant between γ-PGA and calcium was determined to be 6.50 ± 2.47 × 104 mol/L, where 3.6 units of glutamate was capable of binding one Ca2+. The structure of PGA-Ca was characterized, revealing that Ca2+ chelation promoted the aggregation of γ-PGA molecules, disrupting the network structure and forming a mineralized β-sheet-rich structure. In vitro digestion experiments demonstrated that PGA-Ca better maintained the soluble state of Ca2+ in the intestine compared with CaCl2. Cell absorption experiments showed that PGA-Ca exhibited 20% higher permeability through Caco-2 cell monolayers than CaCl2, indicating its higher bioavailability. Notably, PGA-Ca demonstrated improved absorption in the presence of dietary inhibitors, such as oxalate, tannin, and phytate, which compete with Ca2+. Finally, the molecular mechanism underlying the promotion of calcium absorption by PGA-Ca was investigated using RNA sequencing. The results reveal that PGA-Ca enhanced Ca2+ active transport by upregulating CACNA2D3 and downregulating CBARP, while enhancing paracellular Ca2+ transport by downregulating JAM2. This comprehensive study highlights the potential of PGA-Ca as a highly beneficial calcium-delivery system.

Research advances on CaMKs-mediated neurodevelopmental injury.

Calcium/calmodulin-dependent protein kinases (CaMKs) are important proteins in the calcium signaling cascade response pathway, which can broadly regulate biological functions in vivo. Multifunctional CaMKs play key roles in neural development, including neuronal circuit building, synaptic plasticity establishment, and neurotrophic factor secretion. Currently, four familial proteins, calcium/calmodulin-dependent protein kinase I (CaMKI), calcium/calmodulin-dependent protein kinase II (CaMKII), eukaryotic elongation factor 2 kinase (eEF2K, popularly known as CaMKIII) and calcium/calmodulin-dependent protein kinase IV (CaMKIV), are thought to have been the most extensively studied during neurodevelopment. Although their spatial structures are extremely similar, as well as the initial starting point of activation, both require the activation of calcium and calmodulin (CaM) complexes to be involved in the process, and the phosphorylation sites and modes of each member are different. Furthermore, due to the high structural similarity of CaMKs, their members may play synergistic roles in the regulation of neural development, but different CaMKs also have their own means of regulating neural development. In this review, we first describe the visualized protein structural forms of CaMKI, CaMKII, eEF2K and CaMKIV, and then describe the functions of each kinase in neurodevelopment. After that, we focus on four main mechanisms of neurodevelopmental damage caused by CaMKs: CaMKI/ERK/CREB pathway inhibition leading to dendritic spine structural damage; Ca2+/CaM/CaMKII through induction of mitochondrial kinetic disorders leading to neurodevelopmental damage; CaMKIII/eEF2 hyperphosphorylation affects the establishment of synaptic plasticity; and CaMKIV/JNK/NF-κB through induction of an inflammatory response leading to neurodevelopmental damage. In conclusion, we briefly discuss the pathophysiological significance of aberrant CaMK family expression in neurodevelopmental disorders, as well as the protective effects of conventional CaMKII and CaMKIII antagonists against neurodevelopmental injury.

Вплив комплексу біопротекторів на динаміку активності амінотрансфераз у сироватці крові за умов окремої та одночасної дії свинцю і фтору (експериментальні дослідження)

Lead and fluoride enter the human body individually and simultaneously through water, food, and air, disrupting metabolic processes in liver tissue. The sequential application of a bioprotective complex that reduce the negative effects of lead and fluoride has been insufficiently studied. The aim of the study is to investigate the changes over time in the activity of alanine aminotransferase and aspartate aminotransferase in the blood serum of laboratory animals under prolonged separate and simultaneous exposure to lead and fluoride, without application of bioprotective agents and during the sequential addition of pectin, pectin with calcium, and a complex of pectin, calcium, and antioxidants to the standard animal diet. Materials and Methods. Four clinical trial series were conducted on white rats, each following an orthogonal design 22. Aqueous solutions of Pb(NO3)2 and NaF were administered orally separately and simultaneously over 30 days: in the first series without bioprotective agents, in the second with pectin, in the third with pectin and calcium, and in the fourth with a complex of pectin, calcium, and antioxidants – C, E, and β-carotene vitamins, and selenium. The activity of alanine and aspartate aminotransferases was measured in blood serum on days 3, 15, and 30 in the first and second series of experiments, and on day 30 in the third and fourth series. Results. Separate and simultaneous oral administration of lead and fluoride to white rats leads to increased activity of alanine and aspartate aminotransferases in blood serum. The maximum changes were observed at the end of the experiment. The protective role of pectin alone under long-term fluoride expos ure and simultaneous exposure to lead and fluoride was not sufficiently effective. Concurrent intake of calcium and pectin significantly reduced the increase in transaminase activity, indicating an improvement in the metabolic and functional state of the liver. The application of the bioprotective complex restored the aminotransferase activity in blood serum. Conclusions. The complex of pectin with calcium and antioxidants can be considered an optimal means of correcting aminotransferase activity in blood serum under prolonged separate and simultaneous exposure to lead and fluoride.

Influence of various ion chelators on mechanical, transport and microstructure properties of cement-based materials

Influence mechanism of various ion chelators on the mechanical, transport, and microstructure properties of cement-based materials was explored. The ion chelators included pentasodium diethylenetriamine pentaacetate, tetrasodium ethylenediaminetetraacetate, sodium hexametaphosphate and tetrasodium glutamate diacetate, with a dosage of 1% of the cement mass. The effect of ion chelators on the mechanical, transport, and pore structure properties was evaluated by compressive, sorptivity, and mercury intrusion porosimetry (MIP) tests. The composition and microstructure of hydration products were studied by scanning electron microscope (SEM) and X-ray diffractometer (XRD). Test results indicated that four ion chelators reduced the mechanical and transport properties, and increased the porosity of specimens at 3 d and 7 d. And four ion chelators improved the mechanical and transport properties, and reduced porosity at 28 d and 56 d. The fundamental reason for the differences in the basic properties of cement-based materials caused by the types of ion chelators is that different ion chelators possess various calcium chelating capacities and stability of calcium complexes, which leads to different impact on the complexation substitution reaction process. Moreover, compared to the stability of calcium complexes, the influence of calcium chelating ability on the basic properties of specimens is more significant in the early curing ages.

New insights into the interaction between sorbitol-based liquid-type temperature rise inhibitor and cement hydration: From experiments to molecular dynamic simulations

The use of temperature rise inhibitors (TRIs) holds significant promise in mitigating thermal cracking issues in modern concrete by controlling the precipitation of C-S-H gel, the main product of cement hydration. However, the complexity of their interaction with the non-classical nucleation process of C-S-H remains unclear. This study systematically investigated the influence of a sorbitol-based liquid-type temperature rise inhibitor (L-TRI) on the hydration kinetics of cement suspension using a combination of methods, including conductivity testing, pore solution analysis, and molecular dynamic simulations. It is revealed that the admixture-to-water ratio, rather than admixture-to-cement ratio, governs the effect of L-TRI on cement hydration. The disturbance of L-TRI molecules in the pore solution, mainly calcium complexation and water stabilization, plays a decisive role in inhibiting the secondary nucleation of C-S-H and decelerating the following growth. In contrast, L-TRI has a negligible influence on cement dissolution and the formation of C-S-H precursor.

An Enzyme-Induced Carbonate Precipitation Method for Zn2+, Ni2+, and Cr(VI) Remediation: An Experimental and Simulation Study

Heavy metal contamination has long been a tough challenge. Recently, enzyme-induced carbonate precipitation (EICP) has been proposed to handle this problem. This paper aims to explore the efficacy, process, and mechanisms of EICP using crude sword bean urease extracts to remediate Zn2+, Ni2+, and Cr(VI) contamination. A series of liquid batch tests and geochemical simulations, as well as microscopic analyses, were conducted. The liquid batch test results show that Zn2+, Ni2+, and Cr(VI) can be effectively immobilized by the EICP method, and the highest immobilization percentage was observed for Zn2+, reaching up to 99%. Ni2+ and Cr(VI) were immobilized at 62.4% and 24.4%, respectively. Additionally, the immobilization percentage of heavy metals increased with the concentration of added Ca2+. The simulation results and XRD results reveal that the organic molecules in crude sword bean urease can promote ZnCO3, Zn(OH)2, Zn5(CO3)2(OH)6, and NiCO3 precipitation. The FTIR and SEM-EDS results provide evidence for heavy metal adsorption by the functional groups in crude urease and calcium carbonate. The liquid batch test results, as well as the simulation results and the microscopic analysis results, indicate that the mechanism of EICP in heavy metal remediation can be summarized as biomineralization to form heavy metal carbonate precipitates and metal hydroxide precipitates, adsorption by calcium carbonate, and adsorption or complexation or promoting nucleation by organic molecules.

Silylation-Driven Volatility Enhancement in Mononuclear Calcium, Magnesium, and Barium Complexes with Monomethyl or Silyl Ether and Bis(diketonate).

Magnesium, calcium, and barium heteroleptic complexes were synthesized by the substitution reaction of the bis(trimethylsilyl)amide of Mg(btsa)2·DME, Ca(btsa)2·DME, and Ba(btsa)2·2DME with an ethereal group and hfac ligands (btsa = bis(trimethylsilyl)amide, DME = dimethoxyethane). The compounds Mg(dts)(hfac)2 (1), Ca(dts)(hfac)2 (2), Mg(dmts)(hfac)2 (3), Ca(dmts)(hfac)2 (4), and Ba(dmts)(hfac)2 (5) were fabricated and analyzed using various techniques, including Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermogravimetric analyses, and elemental analysis (dts = 2,2-dimethyl-3,6,9-trioxa-2-siladecane, dmts = 2,2-dimethyl-3,6,9,12-tetraoxa-2-silatridecane, hfac = hexafluoroacetylacetonate). The structures of complexes 2, 4, and 5 were confirmed using single-crystal X-ray crystallography; all complexes display monomeric structures. All compounds underwent trimethylsilylation of the coordinating ethereal alcohols (meeH and tmgeH) in the presence of HMDS as byproducts because of their increasing acidity originating from the electron-withdrawing hfac ligands. (meeH = 2-(2-methoxyethoxy)ethan-1-ol, tmgeH = tri(ethylene glycol) monoethyl ether, HMDS = hexamethyldisilazane).

Oxidized Sulfur Species in Slab Fluids as a Source of Enriched Sulfur Isotope Signatures in Arcs

AbstractRecycling of oxidized sulfur from subducting slabs to the mantle wedge provides simultaneous explanations for the elevated oxygen fugacity (fO2) in subduction zones, their high hydrothermal and magmatic sulfur outputs, and the enriched sulfur isotopic signatures (i.e., δ34S > 0‰) of these outputs. However, a quantitative understanding of the abundance and speciation of sulfur in slab fluids consistent with high pressure experiments is lacking. Here we analyze published experimental data for anhydrite solubility in H2O‐NaCl solutions to calibrate a high‐pressure aqueous speciation model of sulfur within the framework of the deep earth water model. We characterize aqueous complexes, required to account for the high experimental anhydrite solubilities. We then use this framework to predict the speciation and solubility of sulfur in chemically complex fluids in equilibrium with model subducting mafic and ultramafic lithologies, from 2 to 3 GPa and 400 to 800°C at log fO2 from FMQ‐2 to FMQ+4. We show that sulfate complexes of calcium and sodium markedly enhance the stability of sulfate in moderately oxidized fluids in equilibrium with pyrite at fO2 conditions of FMQ+1 to +2, causing large sulfur isotope fractionations up to 10‰ in the fluid relative to the slab. Such fluids could impart oxidized, sulfur‐rich and high δ34S signatures to the mantle wedge that are ultimately transferred to arc magmas, without the need to invoke 34S‐rich subducted lithologies.

Preparation of Calcium-Binding Peptides Derived from Mackerel (Scomber japonicus) Protein and Structural Characterization and Stability Analysis of Its Calcium Complexes.

The purpose of this study was to prepare mackerel peptides (MPs) with calcium-binding capacity through an enzyme method and to investigate the potential role they play in improving the bioavailability of calcium in vitro. The calcium-binding capacity, degree of hydrolysis (DH), molecular weight (MW), and charge distribution changes with the enzymolysis time of MPs were measured. The structural characterization of mackerel peptide-calcium (MP-calcium) complexes was performed using spectroscopy and morphology analysis. The results showed that the maximum calcium-binding capacity of the obtained MPs was 120.95 mg/g when alcalase was used for 3 h, with a DH of 15.45%. Moreover, with an increase in hydrolysis time, the MW of the MPs decreased, and the negative charge increased. The carboxyl and amino groups in aspartic (Asp) and glutamate (Glu) of the MPs may act as calcium-binding sites, which are further assembled into compact nanoscale spherical complexes with calcium ions through intermolecular interactions. Furthermore, even under the influence of oxalic acid, MP-calcium complexes maintained a certain solubility. This study provides a basis for developing new calcium supplements and efficiently utilizing the mackerel protein resource.

Selective and efficient immobilization of cadmium in soil by layered double hydroxides intercalated with the mercaptosuccinic acid

Cadmium (Cd) contamination in cropland poses a significant threat to the quality of agricultural products, but even though in-situ remediation has been extensively applied, non-selective immobilization remains an issue. In order to develop a material that specifically immobilizes Cd in soil, a layered double hydroxide, intercalated with mercaptosuccinic acid (MSA-CFA), was synthesized through co-precipitation. In this case, the MSA-CFA's maximum adsorption capacity was increased from the 513.8 mg·g−1 for unintercalated hydrotalcite CFA to 692.6 mg·g−1. Besides, MSA-CFA efficiently removed 99.25 % of Cd from soil water-extract solution and immobilized up to 70.03 % of bio-available Cd. However, interestingly, its immobilization effects on beneficial metal elements Fe, Mn and Zn were milder, being equivalent to 2/7, 5/7 and 1/2 that of lime, respectively. Moreover, XRD and XPS techniques revealed isomorphous substitution with calcium and sulfhydryl complexation during the Cd adsorption by MSA-CFA. Compared with CFA, the increased adsorption capacity of MSA-CFA for Cd was due to intercalated MSA acting as a new adsorption site, while the enhanced selectivity was contributed by sulfhydryl's affinity for Cd. Altogether, MSA-CFA showed great promise as a competitive and highly efficient candidate amendment in Cd-contaminated soil remediation.

Calcium‐Ligand Cooperation Promoted Activation of N2O, Amine, and H2 as well as Catalytic Hydrogenation of Imines, Quinoline, and Alkenes

AbstractBond activation and catalysis using s‐block metals are of great significance. Herein, a series of calcium pincer complexes with deprotonated side arms have been prepared using pyridine‐based PNP and PNN ligands. The complexes were characterized by NMR and X‐ray crystal diffraction. Utilizing the obtained calcium complexes, unprecedented N2O activation by metal‐ligand cooperation (MLC) involving dearomatization‐aromatization of the pyridine ligand was achieved, generating aromatized calcium diazotate complexes as products. Additionally, the dearomatized calcium complexes were able to activate the N−H bond as well as reversibly activate H2, offering an opportunity for the catalytic hydrogenation of various unsaturated molecules. DFT calculations were applied to analyze the electronic structures of the synthesized complexes and explore possible reaction mechanisms. This study is an important complement to the area of MLC and main‐group metal chemistry.

Calcium-Ligand Cooperation Promoted Activation of N2O, Amine, and H2 as well as Catalytic Hydrogenation of Imines, Quinoline, and Alkenes.

Bond activation and catalysis using s-block metals are of great significance. Herein, a series of calcium pincer complexes with deprotonated side arms have been prepared using pyridine-based PNP and PNN ligands. The complexes were characterized by NMR and X-ray crystal diffraction. Utilizing the obtained calcium complexes, unprecedented N2O activation by metal-ligand cooperation (MLC) involving dearomatization-aromatization of the pyridine ligand was achieved, generating aromatized calcium diazotate complexes as products. Additionally, the dearomatized calcium complexes were able to activate the N-H bond as well as reversibly activate H2, offering an opportunity for the catalytic hydrogenation of various unsaturated molecules. DFT calculations were applied to analyze the electronic structures of the synthesized complexes and explore possible reaction mechanisms. This study is an important complement to the area of MLC and main-group metal chemistry.

Calcium complexes with sulfonic acid-containing flavonoids from the fruits of Phyllanthus acidus

Two rare flavonoid-sulfonic acids complexed with calcium ions, Ca (II)-6‑methoxy-8- sulfonic acid-naringenin complexes and Ca (II)-8-sulfonic acid-isoprunetin complexes, were isolated from the fruits of Phyllanthus acidus (L.) Skeels (Phyllanthaceae). Their planar structures were unambiguously established by extensive interpretation of the HRESIMS, 1D and 2D NMR data, and comparison to the literature data. The single crystal X-ray diffraction analysis revealed the location of sulfonic acid group on flavonoid C-8 position and the existence of metal atom in molecules, which was confirmed further to be calcium by elemental analysis. The two molecules represent the first examples of sulfonic flavonoids coordinated with calcium ions from the natural products. This example enriched the variety of natural product structures. All the isolates were evaluated for their antioxidant and anti-inflammatory activity.

Heteroleptic Calcium Complexes Supported by a Phenoxy-Imine NON Ligand: Polymerization of Cyclic Esters by a Ligand-Assisted, Activated-Monomer Mechanism

Heteroleptic Calcium Complexes Supported by a Phenoxy-Imine NON Ligand: Polymerization of Cyclic Esters by a Ligand-Assisted, Activated-Monomer Mechanism

Unveiling the organic acids with auxiliary functional groups effect on α‐hemihydrate gypsum: Ab initio calculations

AbstractRegulating the crystal morphology of low aspect ratio, short columnar α‐hemihydrate gypsum (α‐HH) is crucial due to its distinctive physical and chemical properties, which make it widely applicable. In this work, succinic acid, malic acid, and maleic acid were selected as the research objects, among which the number and spacing of carboxyl groups were the same, while the auxiliary functional groups were different. The adsorption energy, Mulliken charge population, electronic state density, and charge density difference of the three organic acids on the surfaces of α‐HH were calculated by well‐defined ab initio calculations. The results showed that the synergistic effect of ‐COOH groups is necessary for the effective crystallization of α‐HH. Organic acids interact with the Ca atoms on the crystal surface, as evidenced by their preferential adsorption on the top surface of α‐HH crystals (002). This interaction occurs through a double‐dentate chelation between the carboxyl oxygen atoms at both ends of the organic acid and the Ca atoms on the crystal surface, resulting in the formation of a six‐membered cyclic organic acid calcium complex. This complex hinders ion diffusion and the stacking of crystal surfaces, leading to a decrease in the growth rate along the c‐axis and promoting more extensive crystal development and larger crystal sizes. The work provides insight into the preparation of short prismatic α‐HH using organic acid crystallizing agents.

Liver and spleen predominantly mediate calciprotein particle clearance in a rat model of chronic kidney disease.

Calciprotein particles (CPPs) provide an efficient mineral buffering system to prevent the complexation of phosphate and calcium in the circulation. However, in chronic kidney disease (CKD), the phosphate load exceeds the mineral buffering capacity, resulting in the formation of crystalline CPP2 particles. CPP2 have been associated with cardiovascular events and mortality. Moreover, CPP2 have been demonstrated to induce calcification in vitro. In this study, we examined the fate of CPP2 in a rat model of CKD. Calcification was induced in Sprague-Dawley rats by 5/6 nephrectomy (5/6-Nx) combined with a high-phosphate diet. Control rats received sham surgery and high-phosphate diet. Twelve weeks after surgery, kidney failure was significantly induced in 5/6-Nx rats as determined by enhanced creatinine and urea plasma levels and abnormal kidney histological architecture. Subsequently, radioactive and fluorescent (FITC)-labeled CPP2 ([89Zr]Zr-CPP2-FITC) were injected intravenously to determine clearance in vivo. Using positron emission tomography scans and radioactive biodistribution measurements, it was demonstrated that [89Zr]Zr-CPP2-FITC are mainly present in the liver and spleen in both 5/6-Nx and sham rats. Immunohistochemistry showed that [89Zr]Zr-CPP2-FITC are predominantly taken up by Kupffer cells and macrophages. However, [89Zr]Zr-CPP2-FITC could also be detected in hepatocytes. In the different parts of the aorta and in the blood, low values of [89Zr]Zr-CPP2-FITC were detectable, independent of the presence of calcification. CPP2 are cleared rapidly from the circulation by the liver and spleen in a rat model of CKD. In the liver, Kupffer cells, macrophages, and hepatocytes contribute to CPP2 clearance.NEW & NOTEWORTHY Calciprotein particles (CPPs) buffer calcium and phosphate in the blood to prevent formation of crystals. In CKD, increased phosphate levels may exceed the buffering capacity of CPPs, resulting in crystalline CPPs that induce calcification. This study demonstrates that labeled CPPs are predominantly cleared from the circulation in the liver by Kupffer cells, macrophages, and hepatocytes. Our results suggest that targeting liver CPP clearance may reduce the burden of crystalline CPP in the development of vascular calcification.

Calcium complexation by steroids involved in the steroidogenesis.

Steroids that take part in the pathways of human steroidogenesis are involved in many biological mechanisms where they interact with calcium. In the present work, the binding selectivities and affinities for calcium of progestagens, mineralocorticoids, androstagens, and estrogens were studied by Electrospray Ionization-Mass Spectrometry (ESI-MS). The adduct profile of each steroid was characterized by high resolution and tandem mass spectrometry. The relative stability of the most important adducts was studied by threshold collision induced dissociation, E1/2. Doubly-charged steroid-calcium complexes [nM+Ca]2+ with n=1-6 were predominant in the mass spectra. The adduct [5M+Ca]2+ was the base peak for most 3-keto-steroids, while ligands bearing hindered ketones or α-hydroxy-ketones also yielded [nM+Ca+mH2O]2+ with n=3-4 and m=0-1. Principal component analysis allowed us to spot the main differences and similarities in the binding behavior of these steroids. The isomers testosterone and dehydroepiandrosterone, androstanolone and epiandrosterone, and 17-α-hydroxyprogesterone and 11-deoxycorticosterone showed remarkable differences in their adduct profiles. Computational modeling of representative adducts was performed by density functional theory methods. The possible binding modes at low and high numbers of steroid ligands were determined by calcium Gas Phase Affinity, and through modeling of the complexes and comparison of their relative stabilities, in agreement with the experimental results.

Molecular Mechanisms of Peptide–Calcium Complexes in Enhancing Calcium Absorption: A Transcriptome Analysis of Caco-2 Cells Treated with Whey Protein-Derived Peptides DAF and EAC

Molecular Mechanisms of Peptide–Calcium Complexes in Enhancing Calcium Absorption: A Transcriptome Analysis of Caco-2 Cells Treated with Whey Protein-Derived Peptides DAF and EAC

Hydrochloric Acid Catalyzed Hydrothermal Treatment to Recover Phosphorus from Municipal Sludge

Resource utilization of sludge is critical because traditional sludge treatment methods cause a large amount of nutrient loss. This study investigated the impact of hydrochloric acid quantity, reaction temperature, and time on phosphorus release and migration from municipal sludge during hydrothermal treatment and designed a sludge disposal method for the recovery and utilization of phosphorus resources. We know that hydrochloric acid destroys the complexation of calcium and phosphorus precipitates, leading to the selective transfer of phosphorus to the liquid phase, and that the addition of 1–5% hydrochloric acid corresponds to a phosphorus extraction rate in the range of 0.3–98%. When hydrochloric acid is added, a change in temperature and reaction time has a negligible effect on phosphorus. Phosphorus can be recovered using the liquid product obtained under the optimal hydrothermal reaction conditions (adding 5% HCl at 205 °C for 30 min). After adjusting the pH value and adding the magnesium source, struvite (MgNH4PO4·6H2O) can be precipitated quickly and with high purity. At a cost of USD 27.8/ton of sludge, this method can recover 94% of the phosphorus in the sludge, and the bioavailable phosphorus ratio of the product is 93%, therefore, providing an important alternative to existing phosphorus recovery technologies.

CO reduction by calcium and ytterbium hydride complexes with a bulky monodentate carbazolyl ligand.

The bulky monodentate carbazolyl ligand 1,8-bis(3,5-ditertbutylphenyl)-3,6-ditertbutylcarbazole (dtbpCbz) was employed in the synthesis of monomeric heteroleptic amido carbazolyl complexes of Ca and Yb. For both central metal atoms, dimeric hydride complexes [(dtbpCbz)Ca(benzene)H]2, [(dtbpCbz)Ca(THF)H]2, [(dtbpCbz)Yb(benzene)H]2 and [(dtbpCbz)Yb(THF)H]2 were obtained, which show remarkably poor solubility in organic solvents. The characteristic hydride 1H NMR resonance of [(dtbpCbz)Ca(benzene)H]2 was observed at 2.07 ppm, and for the first time, characteristic vibrational modes of the Ca2H2 and Yb2H2 moiety are discussed. Despite their poor solubility, the hydride complexes could be reacted with CO to yield the corresponding ethenediolate complexes.