Synthesis, anticancer evaluation of novel hybrid pyrazole-based chalcones, molecular docking, DNA fragmentation, and gene expression: in vitro studies.

A unique series of pyrazolyl-chalcone derivatives was synthesized via the method of Claisen-Schmidt condensation. The desired chalcone derivatives 7a-d and 9a-f were obtained in good yields by reacting the 4-acetyl-5-thiophene-pyrazole with the appropriate heteroaryl aldehyde derivatives. The novel chalcones have undergone complete elemental analysis, 1H-NMR, 13C-NMR, mass spectrometry, and IR characterization. The three human cancer cell lines MCF7 (human Caucasian breast adenocarcinoma), PC3 (prostatic cancer) and PACA2 (pancreatic carcinoma) as well as the normal cell line BJ1 (normal skin fibroblasts) were tested in vitro for the anti-cancer properties of the newly synthesized chalcone derivatives. When compared to the reference medicine doxorubicin (IC50 = 52.1 µM), compound 9e showed the most promise derivative (IC50 = 27.6 µM) against PACA2 cells, while compound 7d demonstrated anticancer efficacy (IC50 = 42.6 µM against MCF7 cells compared to the reference drug doxorubicin (IC50 = 48 µM). Using breast and pancreatic cell lines, the gene expression, DNA damage, and DNA fragmentation percentages for compounds 7d and 9e were evaluated. Moreover, the molecular docking study of compounds 7d and 9e was assessed. The binding affinities of compound 9e toward P53 mutant Y220C was -22 kcal per mole, while those of compound 7d towards Bcl2 and CDK4 were -27.81 and -26.9 kcal per mole, respectively, compared to the standard values (-15.82, -33.96 and -29.9 kcal per mole).

Green, facile synthesis and evaluation of unsymmetrical carbamide derivatives as antimicrobial and anticancer agents with mechanistic insights.

A very practical method for the synthesis of unsymmetrical carbamide derivatives in good to excellent yield was presented, without the need for any catalyst and at room temperature. Using a facile and robust protocol, fifteen unsymmetrical carbamide derivatives (9-23) bearing different aliphatic amine moieties were designed and synthesized by the reaction of secondary aliphatic amines with isocyanate derivatives in the presence of acetonitrile as an appropriate solvent in good to excellent yields. Trusted instruments like IR, mass spectrometry, NMR spectra, and elemental analyses were employed to validate the purity and chemical structures of the synthesized compounds. All the synthesized compounds were tested as antimicrobial agents against some clinically bacterial pathogens such as Salmonella typhimurium, Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. Compounds 15, 16, 17, 19 and 22 showed potent antimicrobial activity with promising MIC values compared to the positive controls. Moreover, compounds 15 and 22 provide a potent lipid peroxidation (LPO) of the bacterial cell wall. On the other hand, we investigated the anti-proliferative activity of compounds 9-23 against selected human cancerous cell lines of breast (MCF-7), colon (HCT-116), and lung (A549) relative to healthy noncancerous control skin fibroblast cells (BJ-1). The mechanism of their cytotoxic activity has been also examined by immunoassaying the levels of key anti- and pro-apoptotic protein markers. The results of MTT assay revealed that compounds 10, 13, 21, 22 and 23 possessed highly cytotoxic effects. Out of these, three synthesized compounds 13, 21 and 22 showed cytotoxicity with IC50 values (13, IC50 = 62.4 ± 0.128 and 22, IC50 = 91.6 ± 0.112 µM, respectively, on MCF-7), (13, IC50 = 43.5 ± 0.15 and 21, IC50 = 38.5 ± 0.17 µM, respectively, on HCT-116). Cell cycle and apoptosis/necrosis assays demonstrated that compounds 13 and 22 induced S and G2/M phase cell cycle arrest in MCF-7 cells, while only compound 13 had this effect on HCT-116 cells. Furthermore, compound 13 exhibited the greatest potency in inducing apoptosis in both cell lines compared to compounds 21 and 22. Docking studies indicated that compounds 10, 13, 21 and 23 could potentially inhibit enzymes and exert promising antimicrobial effects, as evidenced by their lower binding energies and various types of interactions observed at the active sites of key enzymes such as Sterol 14-demethylase of C. albicans, Dihydropteroate synthase of S. aureus, LasR of P. aeruginosa, Glucosamine-6-phosphate synthase of K. pneumenia and Gyrase B of B. subtilis. Moreover, 13, 21, and 22 demonstrated minimal binding energy and favorable affinity towards the active pocket of anticancer receptor proteins, including CDK2, EGFR, Erα, Topoisomerase II and VEGFFR. Physicochemical properties, drug-likeness, and ADME (absorption, distribution, metabolism, excretion, and toxicity) parameters of the selected compounds were also computed.

Evaluation of Pyrazolyl-Indolizine Derivatives as Antimicrobial Agents: Synthesis, In vitro, In silico ADMET and Molecular Docking Studies.

Herein, we report analogues of s-indacene by the synthesis of novel indolizine derivatives. Using chloroform as an appropriate solvent, sixteen derivatives of pyrazolyl-indolizine (4--19) were prepared by the reaction of 3-(dimethylamino)-1-(1H-pyrrol-2-yl)prop-2-en-1-one (1) with hydrazonoyl chloride derivatives (2) in the presence of triethylamine in good to excellent yields. We used NMR spectra, IR, mass spectrometry, as well as elemental analyses to prove the chemical structures and the purity of the synthesized compounds 4-19. Among all tested compounds 5, 9, 13 and 19 had a potent antimicrobial efficiency against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aerginousea, Sallmonella typhemerium, and Candida albicans. Furthermore, a significant increase in lipid peroxidation (LPO) toward the Gram-negative bacteria, Pseudomonas aeruginosa when treated with compound 9 was observed, while compound 13 remarkably increased the cell membrane oxidation of Salmonella typhimurium. Additionally, we utilized docking studies and in silico methods to evaluate the drug-likeness, physicochemical properties, and ADMET profiles of the compounds. The results of the molecular docking simulation revealed that the synthesized compounds displayed decreased binding energy when interacting with the active sites of important enzymes, including Sterol 14-demethylase of C. albicans, Dihydropteroate synthase of S. aureus, LasR of P. aeruginosa, Glucosamine-6-phosphate synthase of S. typhimurium, and Gyrase B of B. subtilis.

Design, synthesis, structure elucidation, antimicrobial, molecular docking, and SAR studies of novel urea derivatives bearing tricyclic aromatic hydrocarbon rings.

The targeted compounds were prepared using both (9H-fluoren-9-ylidene)hydrazine (1) and 10H-phenothiazine (2) as starting materials. The treatment of 1 or 2 with different isocyanates afforded the title compounds 7a-d, 8a, and 8b in excellent yield. All compounds were characterized and ascertained by infrared, nuclear magnetic resonance, and elemental analyses as well as single-crystal X-ray diffraction. The antimicrobial efficiency of all was tested in vitro, and a noticeable inhibition activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans was obtained by compounds 7a, 7b, 8a, and 8b. Moreover, the biofilm mechanism activity was strongly inhibited by compounds 7b and 8b for all bacterial pathogens, with a percentage ratio of more than 55%. The findings from the molecular docking simulation revealed that compounds 7a, 7b, 8a, and 8b exhibited favorable binding energies and interacted effectively with the active sites of sterol 14-demethylase, dihydropteroate synthase, gyrase B, LasR (major transcriptional activator of P. aeruginosa), and carbapenemase for C. albicans, S. aureus, B. subtills, K. pneumoniae, and P. aeruginosa, respectively. These results suggest that the compounds have the potential to inhibit the activity of these enzymes and demonstrate promising antimicrobial properties. Moreover, the in silico evaluation of drug likeness and absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles for compounds 7a, 7b, 8a, and 8b demonstrated their compatibility with Lipinski's, Ghose's, Veber's, Muegge's, and Egan's rules. These findings suggest that these compounds possess favorable physicochemical properties, making them promising candidates for continued drug development efforts.

Impact of trifluoromethyl and sulfonyl groups on the biological activity of novel aryl-urea derivatives: synthesis, in-vitro, in-silico and SAR studies.

We designed and prepared a novel series of urea derivatives with/without sulfonyl group in their structures to investigate the impact of the sulfonyl group on the biological activity of the evaluated compounds. Antibacterial investigations indicated that derivatives 7, 8, 9, and 11 had the most antibacterial property of all the compounds examined, their minimum inhibitory concentrations (MICs) determined against B. mycoides, E. coli, and C. albicans, with compound 8 being the most active at a MIC value of 4.88 µg/mL. Anti-cancer activity has been tested against eight human cancer cell lines; A549, HCT116, PC3, A431, HePG2, HOS, PACA2 and BJ1. Compounds 7, 8 and 9 emerged IC50 values better than Doxorubicin as a reference drug. Compounds 7 and 8 showed IC50 = 44.4 and 22.4 µM respectively against PACA2 compared to Doxorubicin (IC50 = 52.1 µM). Compound 9 showed IC50 = 17.8, 12.4, and 17.6 µM against HCT116, HePG2, and HOS, respectively. qRT-PCR revealed the down-regulation of PALB2 in compounds 7 and 15 treated PACA2 cells. Also, the down-regulation of BRCA1 and BRCA2 was shown in compound 7 treated PC3 cells. As regard A549 cells, compound 8 decreased the expression level of EGFR and KRAS genes. While compounds 7 and 9 down-regulated TP53 and FASN in HCT116 cells. Molecular docking was done against Escherichia coli enoyl reductase and human Son of sevenless homolog 1 (SOS1) and the results showed the promising inhibition of the studied proteins.

Design, synthesis, in vitro anticancer, molecular docking and SAR studies of new series of pyrrolo[2,3-d]pyrimidine derivatives.

The current study involves the design and synthesis of a newly synthesized pyrrolo[2,3-d]pyrimidine derivatives to contain chlorine atoms in positions 4 and 6 and trichloromethyl group in position 2 using microwave technique as a new and robust approach for preparation of this type of pyrrolo[2,3-d]pyrimidine derivatives. The chemical structure of the synthesized pyrrolo[2,3-d]pyrimidine derivatives 3-19 was well-characterized using spectral and elemental analyses as well as single-crystal X-ray diffraction. All compounds were tested in vitro against seven selected human cancer cell lines, namely, MCF7, A549, HCT116, PC3, HePG2, PACA2 and BJ1 using MTT assay. It was found that compounds 14a, 16b and 18b were the most active toward MCF7 with IC50 (1.7, 5.7, and 3.4 µg/ml, respectively) relative to doxorubicin (Dox.) (26.1 µg/ml). Additionally, compound 17 exerted promising cytotoxic effects against HePG2 and PACA2 with IC50 (8.7 and 6.4 µg/ml, respectively) relative to Dox. (21.6 and 28.3 µg/ml, respectively). The molecular docking study confirmed our ELISA result which showed the promising binding affinities of compounds 14a and 17 against Bcl2 anti-apoptotic protein. At the gene expression level, P53, BAX, DR4 and DR5 were up-regulated, while Bcl2, Il-8, and CDK4 were down-regulated in 14a, 14b and 18b treated MCF7 cells. At the protein level, compound 14b increased the activity of Caspase 8 and BAX (18.263 and 14.25 pg/ml) relative to Dox. (3.99 and 4.92 pg/ml, respectively), while the activity of Bcl2 was greatly decreased in 14a treated MCF7 (2.4 pg/ml) compared with Dox. (14.37 pg/ml). Compounds 14a and 14b caused cell cycle arrest at the G1/S phase in MCF7. Compounds 16b and 18b induced the apoptotic death of MCF7 cells. In addition, the percentage of fragmented DNA was increased significantly in 14a treated MCF7 cells.

Anticancer activity of novel 3-(furan-2-yl)pyrazolyl and 3-(thiophen-2-yl)pyrazolyl hybrid chalcones: Synthesis and in vitro studies.

Twelve novel chalcone derivatives were prepared using the Claisen-Schmidt condensation reaction. The reaction of 4-acetyl-5-furan/thiophene-pyrazole derivatives 5 with the corresponding aldehydes 6 afforded the targeted chalcone derivatives 7a-l in good yields. The newly synthesized chalcones were fully characterized by spectrometric and elemental analyses. The in vitro anticancer activities of the novel compounds 7a-l were evaluated against four human cancer cell lines: HepG2 (human hepatocellular carcinoma), MCF7 (human Caucasian breast adenocarcinoma), A549 (lung carcinoma), and BJ1 (normal skin fibroblasts). Compound 7g emerged as the most promising compound, with IC50 = 27.7 µg/ml against A549 cells compared to the reference drug doxorubicin (IC50 = 28.3 µg/ml), and IC50 = 26.6 µg/ml against HepG2 cells compared to the reference drug doxorubicin (IC50 = 21.6 µg/ml). The gene expression and DNA damage values and the DNA fragmentation percentages for compound 7g were determined on the lung and liver cell lines. The expression levels of the AMY2A and FOXG1 genes increased significantly (p < 0.01) in the negative samples of lung cancer cells compared with treated cells. Also, the expression values of the PKM and PSPH genes improved significantly (p < 0.01) in the negative samples compared with treated samples of liver cancer cells. The DNA damage values increased significantly (p < 0.01) in treated lung cell line samples (7g) and the positive control. The results showed a significant decrease (p < 0.05) in DNA damage values in the negative samples of liver cancer cells compared to those treated with 7g. However, the DNA fragmentation values increased significantly (p < 0.01) in the treated lung and liver cell line samples compared with the negative control.

Synthesis, antimicrobial, anti-cancer and in silico studies of new urea derivatives.

The reaction of an alkyl or aryl isocyanates with some primary amines in acetonitrile at room temperature afforded the corresponding alkyl- and aryl-urea derivatives. All the prepared urea compounds have been elucidated by FTIR, NMR, and elemental analysis. The compounds 1 and 3 were confirmed by single-crystal X-ray diffraction. The 4-tolylsulfonyl isocyanate reacted with the aryl amines 1, 2, 3, and 2,4-dichloroaniline to afford the corresponding sulfonylurea derivatives 5-8. Likewise, the reaction of the isocyanates with 2,4-dichloroaniline, 5-methyl isoxazole-3-amine, and 2-aminothiazole derivatives gave the corresponding urea derivatives 9-17. All the prepared compounds 5-17 were tested in vitro as anti-microbial and anti-HepG2 agents. Moreover, analyzing gene expression of TP53-exon4 and TP53-exon7, DNA damage values, and DNA fragmentation percentages have been discussed. The compounds 5 and 8 recorded the highest activity against the tested microbial strains with maximum activity against C. albicans (50 mm) and B. mycoides (40 mm), respectively. The compounds 5 inhibited the growth of E. coli, S. aureus, and C. Albicans at the MIC level of 0.0489 µM, while the compound 8 was able to inhibit the visible growth of E. coli and C. albicans at MIC value of 3.13 µM and S. aureus at 0.3912 µM. In the same line, compound 5 showed the best cytotoxic activity against the HepG2 cell line (IC50 = 4.25 µM) compared to 5 fluorouracil with IC50 = 316.25 µM. Expression analysis of liver cancer related to a gene including TP53-exon4 and TP53-exon7 was used in HepG2 Liver cancer cell lines using RT-qPCR. The expression values of TP53-exon4 and TP53-exon7 genes were decreased. The DNA damage values and DNA fragmentation percentages were increased significantly (P < 0.01) in the treated HepG2 (5) sample compared with the negative control. Docking studies were performed for the synthetic compounds against 2 bacterial proteins (DNA gyrase subunit B, and penicillin binding protein 1a) that are known targets for some antibiotics, and one cell division protein kinase 2 (CDK2) as target for anticancer drugs.

Novel [l,2,4]triazolo[3,4-a]isoquinoline chalcones as new chemotherapeutic agents: Block IAP tyrosine kinase domain and induce both intrinsic and extrinsic pathways of apoptosis.

Two novel chemotherapeutic chalcones were synthesized and their structures were confirmed by different spectral tools. Theoretical studies such as molecular modeling were done to detect the mechanism of action of these compounds. In vitro cytotoxicity showed a strong effect against all tested cell lines (MCF7, A459, HepG2, and HCT116), and low toxic effect against normal human melanocytes (HFB4). The lung carcinoma cell line was chosen for further molecular studies. Real-time PCR demonstrated that the two compounds upregulated gene expression of (BAX, p53, casp-3, casp-8, casp-9) genes and decreased the expression of anti-apoptotic genes bcl2, CDK4, and MMP1. Flow-cytometry indicated that cell cycle arrest of A459 was induced at the G2/M phase and the apoptotic percentage increased significantly compared to the control sample. Cytochrome c oxidase and VEGF enzyme activity were detected by ELISA assay. SEM tool was used to follow the morphological changes that occurred on the cell surface, cell granulation, and average roughness of the cell surface. The change in the number and morphology of mitochondria, cell shrinkage, increase in the number of cytoplasmic organelles, membrane blebbing, chromatin condensation, and apoptotic bodies were observed using TEM. The obtained data suggested that new chalcones exerted their pathways on lung carcinoma through induction of two pathways of apoptosis. Graphical abstract Novel chalcones were prepared and confirmed by different spectral tools. Docking simulations were done to detect the mechanism of action. In vitro cytotoxicity indicated a strong effect against different cancer cell lines and low toxic effects against normal human melanocytes (HFB4). The lung carcinoma cell line was chosen for further molecular studies that include Real-time PCR, Flow-cytometry, Cytochrome c oxidase, and ELISA assay. SEM and TEM tool were used to follow the morphological changes occurred on the cell surface.

Novel 2-cyanoacrylamido-4,5,6,7-tetrahydrobenzo[b]thiophene derivatives as potent anticancer agents.

Ethyl 2-acrylamido-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate as well as its corresponding bis-derivatives, 5-10, with aliphatic linkers were synthesized, fully characterized, and tested as novel anticancer agents. The targeted compounds, 5-10, were obtained by the Knoevenagel condensation reactions of bis-o- or -p-aldehyde with a molar ratio of ethyl 2-(2-cyanoacetamido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate of 2 in the presence of piperidine in excellent yields (93-98%). The in vitro anticancer activities of the prepared compounds were evaluated against HepG2, MCF-7, HCT-116, and BJ1 cells. Compounds 7 and 9 emerged as the most promising compounds, with IC50 values of 13.5 and 32.2 µg/ml, respectively, against HepG2 cells, compared with the reference drug doxorubicin (IC50 : 21.6 µg/ml). Real-time reverse-transcription polymerase chain reaction was used to measure the changes in expression levels of the COL10A1 and COL11A1, ESR1, and ERBB2, or AXIN1 and CDKN2A genes within the treated cells, as genetic markers for colon, breast, or liver cancers, respectively. Treatment of the colon cancer cells with compounds 5, 9, and 10, or breast and liver cancers cells with compounds 7, 8, 9, and 10 downregulated the expression of the investigated tumor markers. The DNA damage values (depending on comet and DNA fragmentation assays) increased significantly upon treatment of colon cancer cells with compounds 5, 9, and 10, and breast and liver cells with compounds 8, 9, and 10. The structure-activity relationship suggested that the increase of the chain of the alkyl linker increases the anticancer activity and the compounds with bis-cyanoacrylamide moieties are more active than those with one cyanoacrylamide moiety.

Molecular Docking Study, Cytotoxicity, Cell Cycle Arrest and Apoptotic Induction of Novel Chalcones Incorporating Thiadiazolyl Isoquinoline in Cervical Cancer.

BACKGROUND: Chalcones are naturally occurring compounds found in various plant species which are widely used for the traditional popular treatments. Chalcones are distinguished secondary metabolites reported to display diverse biological activities such as antiviral, antiplatelet, anti-inflammatory, anticancer, antibacterial and antioxidant agents. The presence of a,ß-unsaturated carbonyl group in chalcones is assumed to be responsible for their bioactivity. In addition, heterocyclic compounds having nitrogen such as isoquinolines are of considerable interest as they constitute the core structural element of many alkaloids that have enormous pharmacological activities. OBJECTIVE: The objective of this study is the synthesis and biological activity of novel chalcones incorporating thiadiazolyl isoquinoline as potential anticancer candidates. Different genetic tools were used in an attempt to know the mechanism of action of this compound against breast cancer. METHODS: An efficient one pot synthesis of novel chalcones incorporating thiadiazolyl isoquinoline was developed. The cytotoxic activity of the novel synthesized compounds was performed against four different kinds of cancer cell lines. RESULTS: Among all the tested derivatives, chalcone 3 has the best cytotoxic profile against A549, MCF7, and HeLa cell lines, with IC50s 66.1, 51.3, and 85.1µM, respectively. Molecular docking studies for chalcone 3 revealed that CDK2, and EGFRTK domains have strong binding affinities toward the novel chalcone 3, while tubulin-colchicine-ustiloxin, and VEGFRTK domains illustrated moderate mode of binding. CONCLUSION: We have developed an efficient method for the synthesis of novel chalcones incorporating thiadiazolyl isoquinoline. All compounds showed better cytotoxicity results against four kinds of cancer cell lines (A549, MCF7, HCT116, and HELA cells). The results depicted that chalcone 3 has a high and promising cytotoxic effect against HELA cell line and the mechanism of cytotoxicity was widely studied through different theoretical and experimental tools. Thus, the newly synthesized derivative 3 can be utilized as a novel chemotherapeutic compound for cervical carcinoma.

Synthesis, structural characterization and in vivo anti-diabetic evaluation of some new sulfonylurea derivatives in normal and silicate coated nanoparticle forms as anti-hyperglycemic agents.

Series of new sulfonylurea derivatives (gliclazide analogues) was synthesized and characterized. Thus, p-tolylsulfonylisocyanate was left to react with different amino derivatives under mild conditions to afford the desired sulfonylurea derivatives 1-5. The molecular structure of the compound N-(2,6-Dichlorophenylcarbamoyl)-4-methylbenzenesulfonamide, 1c has been elucidated by single crystal X-ray diffraction. Anti-diabetic properties of the synthesized compounds relative to anti-diabetic drug (gliclazidem MR60) were carried out, where most of the tested compounds showed significant activity for reducing the blood glucose level. The results revealed that compounds 1c and 5 showed better anti-diabetic activities compared with gliclazide. Activity of the most potent derivatives of sulfonylurea compounds namely 1c and 5 were increased using coated nanostructure tetraethyl orthosilicate (TEOS) as a modified release (MR) agent. The effect of the prepared sulfonylurea compounds against the diabetic condition was investigated using specific selected biomarkers as of liver enzyme activities as transaminases (AST, ALT) and alkaline phosphatase (ALP), lipids profiles; total cholesterol (TC), triacylglycerols (TG) and total lipid (TL). The antioxidants, oxidative stress biomarkers and histological examination were also examined and discussed.

Cyclooctatetraenyl calcium and strontium amido complexes.

This paper reports the synthesis and structural characterisation of a series of cyclooctatetraenyl (C8H8) complexes of calcium and strontium, most of them containing the bis(trimethylsilyl)amido ligand. Mixing MI2 (M = Ca, Sr), KN(SiMe3)2 and K2(C8H8) in thf in a 2 : 2 : 1 ratio gave the inverse sandwich amido complexes [[{(Me3Si)2N}M(thf)x]2(µ-C8H8)] (M = Ca, x = 1; M = Sr, x = 2) (1-Ca, 1-Sr) in fair to good yields. From a 1 : 1 : 1 ratio, the mixed potassium calcium complex [[{(Me3Si)2N}Ca(thf)](µ-C8H8)K] (2) was obtained in good yield. The reaction of 2 with a 1 : 1 mixture of CaI2 and KN(SiMe3)2 yielded 1-Ca confirming that the reaction could be carried out stepwise. Attempts at making heterobimetallic calcium strontium amido complexes from the reaction of 2 with Sr{N(SiMe3)2}2 led to redistribution reactions which afforded the potassium strontium complex [[K{(Me3Si)2N}2Sr]2(µ-C8H8)] (3) among other species. Complex 3 was more conveniently synthesised in fair yield starting from a 2 : 4 : 1 molar mixture of SrI2, KN(SiMe3)2 and K2(C8H8), respectively. Treatment of 2 with PhC[triple bond, length as m-dash]CH in benzene yielded an insoluble complex tentatively formulated as the polymeric complex [CaK(CCPh)(C8H8)(thf)x]n (4). Upon dissolution in thf, 4 underwent a redistribution reaction yielding the X-ray characterised [{Ca(µ-C8H8)2}K2(thf)2] (5) and a homoleptic calcium alkynyl complex [Ca(CCPh)2(thf)x]. Several compounds were characterised by X-ray diffraction as discrete or polymeric structures where CaCπ interactions were identified in some cases. Despite identified drawbacks, such as the lability of the coordinated thf ligands and facile redistribution reactions, this study represents the first synthetic approach to cyclooctatetraenyl heavy alkaline-earth metal amido complexes.

Crystal structures of two ytterbium(III) complexes comprising alkynylamidinate ligands.

Two ytterbium(III) complexes comprising alkynylamidinate ligands, namely bis-(η5-cyclo-penta-dien-yl)(3-cyclo-propyl-N,N'-diiso-propyl-propynamidinato-κ2N,N')ytterbium(III), [Yb(C5H5)2(C12H19N2)] or Cp2Yb[( i Pr2N)2C-C≡C-c-C3H5] (1) and tris-(3-phenyl-N,N'-di-cyclo-hexyl-propynamidinato-κ2N,N')ytterbium(III), [Yb(C21H27N2)3] or Yb[(CyN)2C-C≡C-Ph]3 (Cy = cyclo-hex-yl) (2) have been synthesized and structurally characterized. Both complexes are monomers; for complex 2, the contribution to the scattering from highly disordered toluene solvent molecules in these voids was removed with the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9-18] in PLATON. The stated crystal data for Mr, µ etc. do not take these into account.

Formation and structure of the first metal complexes comprising amidino-guanidinate ligands.

The first metal complexes comprising amidino-guanidinate ligands have been prepared and structurally characterized, namely bis-[µ-N,N',N'',N'''-tetraisopropyl-1-(1-butyl-amidinato)guanidinato-κ3N1,N2:N2]bis-[(tetra-hydro-furan)lithium], [Li2(C18H37N4)2(C4H8O)2], (2), and [bis-(tetra-hydro-furan)-lithium]-di-µ-chlorido-{(N,N'-di-cyclo-hexyl-1-butyl-amidinato-κ2N1,N2)[N,N',N'',N'''-tetra-cyclo-hexyl-1-(1-butyl-amidinato)guanidinato-κ2N1,N2]holmate(III)}, [HoLiCl2(C4H8O)2(C17H31N2)(C30H53N4)], (3). The novel lithium amidino-guanidinate precursors Li[ n BuC(=NR)(NR)C(NR)2] [1: R = Cy (cyclo-hex-yl), 2: R = i Pr) were obtained by treatment of N,N'-diorganocarbodi-imides, R-N=C=N-R (R = i Pr, Cy), with 0.5 equivalents of n-butyl-lithium under well-defined reaction conditions. An X-ray diffraction study of 2 revealed a ladder-type dimeric structure in the solid state. Reaction of anhydrous holmium(III) chloride with in situ-prepared 2 afforded the unexpected holmium 'ate' complex [ n BuC(=NCy)(NCy)C(NCy)2]Ho[ n BuC(NCy)2](µ-Cl)2Li(THF)2 (3) in 71% yield. An X-ray crystal structure determination of 3 showed that this complex contains both an amidinate ligand and the new amidino-guanidinate ligand.

Five different types of η(8)-cyclooctatetraenyl-lanthanide half-sandwich complexes from one ligand set, including a "giant neodymium wheel".

The lithium-cyclopropylethynylamidinates Li[c-C3H5-C[triple bond, length as m-dash]C-C(NR)2] (1a: R = (i)Pr, 1b: R = cyclohexyl (Cy)) have been used as precursors for the preparation of five new series of half-sandwich complexes. These complexes contain the large flat cyclooctatetraenyl ligand (C8H8(2-), commonly abbreviated as COT), and were isolated as solvated, unsolvated and inverse sandwich complexes. Treatment of the halide precursors [(COT)Pr(µ-Cl)(THF)2]2 with 1b and [(COT)Nd(µ-Cl)(THF)2]2 with 1a and 1b in THF in a 1 : 2 molar ratio, respectively, afforded (COT)Ln[µ-c-C3H5-C[triple bond, length as m-dash]C-C(NR)2]2Li(L) (2: Ln = Pr, R = Cy, L = Et2O; 3: Ln = Nd, R = (i)Pr, L = THF; 4: Ln = Nd, R = Cy, L = THF). Treatment of the dimeric cerium(iii) bis(cyclopropylethynylamidinate) complexes [{c-C3H5-C[triple bond, length as m-dash]C-C(NR)2}2Ce(µ-Cl)(THF)]2 (5: R = (i)Pr; 6: R = Cy) in situ with K2C8H8 in a 1 : 1 molar ratio in THF at room temperature afforded the inverse-sandwich complexes (µ-η(8):η(8)-COT)[Ce{c-C3H5-C[triple bond, length as m-dash]C-C(NR)2}2]2 (7: R = (i)Pr; 8: R = Cy). This reaction represents a new method for encapsulation of a planar (C8H8)(2-) ring in lanthanide complexes containing amidinate ligands in the outer decks. Novel unsolvated dinuclear lanthanide half-sandwich complexes were prepared by using the precursors 1a, 1b and COT(2-). Unlike the complexes 2-4, the reaction of [(COT)Pr(µ-Cl)(THF)2]2 with 1a afforded the unsolvated centrosymmetric complex [(COT)Pr(µ-c-C3H5-C[triple bond, length as m-dash]C-C(N(i)Pr)2)]2 (9). These dimeric structures could be also accessed by reaction of LnCl3 (Ln = Ce or Nd) with 1a or 1b and K2COT in a 1 : 1 : 1 molar ratio as a one-pot reaction to give novel [(COT)Ln(µ-c-C3H5-C[triple bond, length as m-dash]C-C(NR)2)]2 complexes (10: Ln = Ce, R = (i)Pr; 11: Ln = Ce, R = Cy; 12: Ln = Nd, R = (i)Pr). Similar treatment of HoCl3 with 1a or 1b and K2COT as three-component reactions in a 1 : 1 : 1 molar ratio afforded the solvated half-sandwich complexes (COT)Ho(c-C3H5-C[triple bond, length as m-dash]C-C(NR)2)(THF) (13: R = (i)Pr; 14: R = Cy). A unique multidecker sandwich complex [(µ-η(8):η(8)-COT){Nd(c-C3H5-C[triple bond, length as m-dash]C-C(NCy)2)(µ-Cl)}2]4 (15) was prepared by reaction of anhydrous NdCl3 with K2COT and 1b in a one-pot reaction. The solid state structure of 15 revealed the presence of an unprecedented macrocyclic sandwich compound ("giant neodymium wheel") consisting of four COT rings sandwiched between eight Nd(3+) ions, and each Nd(3+) ion is bonded to one amidinate ligand and bridged by two chlorine atoms with the neighbouring Nd(3+) ion.