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A series of amine bis(phenolato)lanthanide methyl and amido complexes were synthesized by general salt metathesis reaction in this paper. The reaction of anhydrous lanthanide trichlorides with 1 equiv of sodium amine bis(phenolate) LNa2 [L = Me2NCH2CH2N{CH2-(2-O-C6H2-But2-3,5)}2] in THF at room temperature gave the amine bis(phenolate) lanthanide chlorides LLnCl(THF) (Ln = Yb (1), Ln = Er (2)). Complexes 1 and 2 can be used as starting materials to prepare amine bis(phenolate) lanthanide derivatives. Complexes 1 and 2 reacted with lithium methyl and lithium amide, respectively, to give the corresponding lanthanide methyl and amido products LLnMe(THF) (Ln = Yb (3), Ln = Er (4)) and LLnNPh2(THF) (Ln = Yb (5), Ln = Er (6)). These complexes were well characterized by elemental analyses and IR spectra. The definitive molecular structures of complexes 1, 2, 3, 5, and 6 were provided by single-crystal X-ray analyses. Reactivity studies of complexes 3, 5, and 6 have shown them to be efficient initiators for the r...

Reaction of anhydrous ErCl 3 with sodium salt of carbon-bridged biphenolate, MBMPNa 2 (MBMP 2− =2,2′-methylene-bis (6- tert -butyl-4-methyl-phenoxo)), in 1:2 molar ratio in THF at room temperature gave the lanthanide ‘ate’ complexes (THF)Er(MBMP) 2 Na(THF) 2 ( 1 ) in high isolated yield. Similarly reaction of anhydrous SmCl 3 with 2 equiv. of MBMPNa 2 in THF, then crystallization from toluene in the presence of TMEDA, afforded the final product (THF)Sm(MBMP) 2 Na(TMEDA) ( 2 ). Both complexes 1 and 2 were well characterized by elemental analysis, IR spectra, and X-ray diffraction analysis. Preliminary results revealed that these complexes are able to act as Lewis acid to catalyze the Diels–Alder reaction of cyclopentadiene with methyl acrylate in good activity and stereoselectivity.

Three lanthanide “ate” complexes L2YbM(THF)n supported by amine bis(phenolate) ligand [L=Me2NCH2CH2N{CH2-(2-O-C6H2-But2-2,4)}2; M=Li, n=2 (1); M=Na, n=2 (2); M=K, n=3 (3)] were synthesized by the metathesis reactions of LM2 with anhydrous YbCl3 in 2:1 molar ratio in high yield. All the complexes were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. The influence of the alkali metal ions on the molecular structure of these lanthanide complexes has been elucidated.

The synthesis and structures of new lanthanide complexes supported by the carbon-bridged diphenolato ligand 2,2′-methylenebis(6-tert-butyl-4-methylphenolato) (MBMP2–) are described. Reactions of anhydrous lanthanide trichlorides with Na2MBMP in a 1:2 molar ratio in THF at room temperature afforded the corresponding “ate” (diphenolato)lanthanide complexes [(THF)nLn(MBMP)2Na(THF)2] [Ln = Nd (1), Sm (2), n = 2; Ln = Yb, n = 1 (3)]. Recrystallisation of complexes 1–3 from toluene in the presence of DME gave the discrete ion-pair complexes [(MBMP)2Ln(THF)2][Na(DME)2(THF)2] [Ln = Nd (4), Sm (5), Yb (6)]. These complexes have been fully characterised. The single-crystal structural analyses of 1, 3 and 6 revealed that the coordination geometries of the lanthanide ions can be best described as distorted octahedral in complexes 1 and 6 and distorted trigonal-bipyramidal in complex 3. It was found that these lanthanide complexes are able to act as Lewis acids to catalyse the Diels–Alder reactions of cyclopentadiene with substituted dienophiles with good activity and stereoselectivity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Reactions of [Pt(PCy(3))(2)] (Cy = cyclohexyl) with group 12 metal dihalides have afforded the novel metal only Lewis pair (MOLP) complexes, [(Cy(3)P)(2)Pt→MX(2)] (M = Zn or Cd, X = Br or I), or the oxidative addition product, trans-[(Cy(3)P)(2)(I)PtHgI]. The zinc complex represents the first MOLP to contain an unsupported Pt→Zn linkage.

Asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylarsole and ethyl vinyl ketone was promoted by the palladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary. The keto group in the resulting arsanorbornene cycloadducts could be located stereospecifically in the endo or exo position by controlling the electronic properties of the organopalladium promoter. In the intermolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 2:1. In the intramolecular process, however, only one As–O bidentate arsanorbornene palladium complex was produced stereoselectively. The arsenic-elimination reaction was readily observed on the corresponding endo- and exo-ketoarsine ligands. The absolute configuration and the coordination property of the enantiomerically pure endo-cycloadduct had been established by single-crystal X-ray analysis.

An ytterbium–lithium inverse crown ether complex stabilized by amine-bridged bis(phenolate) ligands (LYbBr)2(μ4-O)(μ3-Li) (1) [L = Me2NCH2CH2N{CH2-(2-O- C6H2-But2-3,5)}2] was isolated as a byproduct from the reaction of LYbCl(THF) with CH3Li in THF in a very low isolated yield. Further study revealed that the inverse crown ether complexes can be synthesized in a controlled manner by the reaction of bis(phenolate) lanthanide chloride with an in situ mixture of n-BuLi with water in THF. A second inverse crown ether complex (L′YbCl)2(μ4-O)(μ3-Li) (2) [L′ = Me2NCH2CH2N{CH2-(2-O-C6H2-But-3-Me-5)}2] was prepared in high isolated yield and well characterized.

Breast cancer resistance protein (BCRP/ABCG2) specifically transports various chemotherapeutic agents and is involved in the development of multidrug resistance (MDR) in cancer cells. MicroRNAs (miRNAs) can play an important role in modulating the sensitivity of cancer cells to chemotherapeutic agents. Therefore, after confirming that BCRP was increased in the mitoxantrone (MX)-resistant MCF-7 breast cancer cell line MCF-7/MX compared with its parental sensitive MCF-7 cell line, we aimed to explore the miRNAs that regulate BCRP expression and sensitize breast cancer cells to chemotherapeutic agents. In the present study, bioinformatic analysis indicated that miR-487a was one of the miRNAs that could bind to the 3' untranslated region (3'UTR) of BCRP. Quantitative RT-PCR (qRT-PCR) analysis demonstrated that the expression of miR-487a was reduced in MCF-7/MX cells, and a luciferase reporter assay demonstrated that miR-487a directly bound to the 3'UTR of BCRP. Moreover, ectopic miR-487a down-regulated BCRP expression at the mRNA and protein levels, increasing the intracellular accumulation and cytotoxicity of MX in resistant MCF-7/MX breast cancer cells. Meanwhile, inhibition of miR-487a increased BCRP expression at the mRNA and protein levels and induced MX resistance in sensitive MCF-7 breast cancer cells. Furthermore, the reduced expression of BCRP and increased antitumor effects of MX were also detected in MCF-7/MX xenograft tumors treated with the miR-487a agmir. Thus, our results suggested that miR-487a can directly regulate BCRP expression and reverse chemotherapeutic drug resistance in a subset of breast cancers.

A series of enantiomerically pure 1,2-diester substituted P,N-ligands incorporating two chiral carbons in the backbone were generated in high yields and high stereoselectivity from acetylenedicarboxylate via initial hydrophosphination using diphenylphosphine followed by hydroamination with various primary and secondary amines. The reactions were activated and stereochemically controlled by the organopalladium complex containing ortho-palladated (S)-(1-(dimethylamino)ethyl)naphthalene under mild conditions. The absolute stereochemistry and the coordination chemistry of P,N-products were determined by the single crystal X-ray diffraction analysis. All the chiral P,N-ligands could be liberated from the palladium template without loss of optical purity. Subsequent recomplexation to selected chiral palladium centers confirmed the optical purity of the new functionalized chiral P,N-ligands.

The organopalladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]phenylene as the chiral auxiliary has been used as the chiral template to promote the asymmetric cycloaddition reaction between diphenylvinylphosphine and 3,4-dimethyl-1-phenylarsole. A diphenylphosphino-substituted asymmetrical heterobidentate arsanorbornene (As-P) ligand was obtained stereoselectively on the chiral palladium template in moderate yield. The chiral benzylamine auxiliary could be removed chemoselectively from the template by treatment with HCl to produce the neutral complex [(As-P)PdCl2]. In contrast to their reported P-P analogue, the arsenic donor in the dichloro complex could be eliminated stereospecifically under mild reaction conditions to generate the corresponding 1-(diphenylphosphino)-3,4-dimethyl-2,4-cyclohexadiene, which remained as a bidentate ligand at the PdCl2 unit via phosphorus and the eta2-C4-C5 double bond. The arsenic-elimination process was found to be influenced by the halo ligand in [(As-P)PdX2]. A similar process was observed with the analogous dibromo complex, but the corresponding diiodo species did not show similar reactivity. All of the novel As-Pd complexes have been characterized by X-ray crystallography.

The asymmetric cycloaddition reactions of 3,4-dimethyl-1-phenylarsole and (Z/E)-diphenyl-1-propenylphosphine/diphenyl-1-styrylphosphine promoted by a chiral organopalladium(ii) complex derived from (S)-[1-(dimethylamino)ethyl]naphthalene proceeded stereoselectively to generate different exo/endo-products. The reactions involving the (Z/E)-methyl substituted phosphines gave the individual optically pure exo- and endo-cycloadducts in very high stereoselectivity (33 : 1). However, when the methyl group was replaced by a Ph moiety both (Z/E)-phenyl substituted phosphines produced the same endo-cycloadduct in a stereoselectivity of 15 : 1. Every reaction produced five new chiral centers (four of them are sterically independent) in a single step and all three optically pure As-P heterobidentate ligands were obtained in high yields. The mechanism involved in the conversion of exo- to endo-product was investigated via density functional theory calculations. Computational results were consistent with the experimentally observed endo/exo-selectivity.