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The article presents abstracts on chemistry topics that are published within the issue including discrete metal complexes, quasi-octahedral iron pyrite mesocrystals, and synthesis of a sanguarine derivative through crystal-solution interactions.

This paper presents the first dysprosium(iii) complex, [{(MeMeArO)3tacn}DyIII(THF)] (1Dy), that shows oxygen-sensitive luminescence. The synthesis, structure and oxygen-sensitive luminescence properties of 1Dy are reported (Φ = 0.050 and τ = 17.7 μs under N2, Φ = 0.011 and τ = 4.1 μs under O2 and KSV = 305 M−1 in THF; KSV = 0.0077%−1 in polystyrene film). The oxygen sensitive mechanism of 1Dy is discussed based on the photophysical properties of the corresponding gadolinium(iii) complex, [{(MeMeArO)3tacn}GdIII(THF)]. [ABSTRACT FROM AUTHOR]

A theoretical investigation into eighteen recently synthesized Pt(II) complexes [(R1n-CNC-R2n)Pt(L)] with doubly deprotonated cyclometalated R1n-CNC-R2n ligands (n = 1-9, R1n-CNC-R2n = 2,6- diphenylpyridine derivatives) and L ligands (L = DMSO, 1-9; L = -CuN≡Ar, 1a-9a), which are used as emitters in orange-red emitting diodes, is reported in this paper. Geometric and electronic structures, absorption and emission spectra, phosphorescence quantum yields, and electroluminescence (EL) efficiency were investigated by DFT and TDDFT methods. We focused on the influence of the primary ligand (R1n-CNC-R2n) and auxiliary ligand (L) on the optical and electronic properties of Pt(II) complexes by introducing carbazole, fluorene, and thiophene group in the primary ligand and/or the replacement of DMSO by -CuN-Ar as an ancillary ligand. The incorporation of carbazole, fluorene, and thiophene into the primary ligand caused the red-shift of absorption and emission spectra. The metal-ligand bond length is contracted where -CuN-Ar was employed as the secondary ligand, which facilitate the metal to ligand charge transfer (MLCT). The larger involvement of MLCT character in emission process is beneficial for improving the quantum yields of 2a-9a. For EL efficiency, all the complexes have a good balance of reorganization energy as potential systems for fabricating effective OLEDs devices except for 1 and 1a. In addition, two new molecules were designed with comparable or better EL efficiency. [ABSTRACT FROM AUTHOR]

A quinoline-based C3-symmetric fluorescent probe (1), N,N′,N′′-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(1-(quinolin-2-yl)-N-(quinolin-2-ylmethyl)methanamine), has been developed which can selectively detect Zn2+ without the interference of Cd2+via significant enhancement in emission intensity (fluorescence “turn-ON”) associated with distinct fluorescence colour changes and very low detection limits (35.60 × 10−9 M in acetonitrile and 29.45 × 10−8 M in 50% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile media). Importantly, this sensor is operative with a broad pH window (pH 4–10). The sensing phenomenon has been duly studied through UV-vis, steady-state, and time-resolved fluorescence spectroscopic methods indicating 1 : 3 stoichiometric binding between 1 and Zn2+ which is further corroborated by 1H NMR studies. Density functional theoretical (DFT) calculations provide the optimized molecular geometry and properties of the zinc complex, 1[Zn(ClO4)]33+, which is proposed to be formed in acetonitrile. The results are in line with the solution-state experimental findings. The single crystal X-ray study provides the solid state structure of the trinuclear Zn2+ complex showing solubility in an aqueous buffer (10 mM HEPES, pH = 7.4). Finally, the resulting trinuclear Zn2+ complex has been utilized as a fluorescence “turn-OFF” sensor for the selective detection of pyrophosphate in a 70% aqueous buffer (10 mM HEPES, pH = 7.4) acetonitrile solvent with a nanomolar detection limit (45.37 × 10−9 M). [ABSTRACT FROM AUTHOR]

The reaction of certain metal salts with N,N′-bis(2-hydroxyethyl)ethylenediamine (bishydeten) and [Ag(CN)2]− resulted in [Ni(bishydeten)2][Ag(CN)2]2·H2O (C1), [Cu(bishydeten)2Ag2(CN)4] (C2) and [Cd(bishydeten)0.5]2[Ag(CN)2]4·3H2O (C3), characterized by elemental, magnetic (C1 and C2), FT-IR, EPR (C2), ESI-MS, thermal, spectroscopic (C1, C2 or C3), and X-ray diffraction (C3) techniques. A detailed study of the antiproliferative and apoptotic properties of all the compounds and [Ag(CN)2]− was carried out using the BrdU Cell Proliferation Assay (BCPA), DNA laddering assay and TUNEL method on HT29, HeLa, C6, and Vero cell lines. These compounds exhibiting a very strong antiproliferative effect even at low micromolar concentrations were found to have cytostatic activity, whereas [Ag(CN)2]− had cytotoxic activity. The cells exposed to the compounds showed DNA laddering formations and the appearance of apoptotic bodies. Also, application of the test compounds at low concentrations was associated with a pronounced loss of the adhesive, migratory, and topoisomerase I activity of the treated tumor cell lines. Immunohistochemical staining analysis demonstrated that these complexes significantly reduced the level of Bcl-2 while causing the accumulation of P53 in HeLa and HT29 cells. Absorbance and emission spectral data reveal that the complexes interact with the DNA via a groove binding mode of interaction. [ABSTRACT FROM AUTHOR]

An expedient procedure is reported for the preparation of the synthetically valuable Au(i) complex [Au(MeCN)(PtBu2C6H4Ph-2)][BF4] (Echavarren's catalyst) directly from gold powder using [NO][BF4] in acetonitrile. The synthetic method obviates the potential presence of silver or halide impurities that follow from the tedious conventional synthesis, and have otherwise been shown to moderate catalyst performance. [ABSTRACT FROM AUTHOR]

A series of dimethyldihydropyrene-appended metal complexes has been synthesized and thoroughly characterized using electrochemical and spectroscopic methods. The ring-opening reaction undergone by the dimethyldihydropyrene core under visible light irradiation proceeds much more efficiently when the metal complexes and the photochromic moiety are connected through a pyridinium-bridge vs a phenyl bridge. The clean electrochemical and photochemical responses of these hybrid systems make them good candidates for the conception of new multi-addressable photo- and redox-switches. [ABSTRACT FROM AUTHOR]

This article reports the synthesis and the characterization of two Cp*2Ln (Ln = Sm and Yb) fragments containing the tetramethylbiphosphinine (tmbp) ligand in equatorial position. The solid-state data indicate the reduction of the tmbp ligand with the decamethylsamarocene fragment along with the oxidation of the metal center, while the metrical parameters highlight a more dubious electronic structure for the tmbp adduct of the decamethylytterbocene fragment. 1H and 31P NMR have been recorded for both complexes and show the unambiguous oxidation of the samarium complex. On the other hand, the NMR data for Cp*2Yb(tmpb) exhibit weakly shifted paramagnetic resonances along with a weak effective moment in solution; a situation that is neither in agreement with a divalent metal center and a neutral ligand, nor with an oxidized ytterbium ion and a radical tmbp ligand. In addition to these experimental data, theoretical calculations were performed on both complexes. DFT calculations highlight a large orbital contribution and an f occupation of 5.4 for the samarium complex, which is to compare to an f occupation of 13.8 and less orbital interactions in the ytterbium complex. [ABSTRACT FROM AUTHOR]

New 5,5-diethylbarbiturate (barb) complexes of Ni(ii), Cu(ii) and Zn(ii) with 1,10-phenanthroline (phen) and 2,2′-dipyridylamine (dpya), namely [Ni(phen-κN,N′)3]Cl(barb)·7H2O (1), [Cu(barb-κN)(barb-κ2N,O)(phen-κN,N′)]·H2O (2), [Cu(barb-κN)2(phen-κN,N′)] (2a), [Zn(barb-κN)2(phen-κN,N′)]·H2O (3), [Ni(barb-κ2N,O)(dpya-κN,N′)2]Cl·2H2O (4), [Cu(barb-κ2N,O)2(dpya-κN,N′)]·2H2O (5) and [Zn(barb-κN)2(dpya-κN,N′)] (6), were synthesized and characterized by elemental analysis, UV-vis, FT-IR and ESI-MS. The structures of the complexes were determined by X-ray crystallography. Notably, 3 and 6 were fluorescent in MeOH : H2O at rt. The interaction of the complexes with fish sperm (FS) DNA and bovine serum albumin (BSA) was investigated in detail by various techniques. The complexes exhibited groove binding along with a partial intercalative interaction with DNA, while the hydrogen bonding and hydrophobic interactions played a major role in binding to BSA. It is noteworthy that 2 exhibited the highest affinity towards DNA and BSA. Enzyme inhibition assay showed that 1–4 show a preference for both A/T and G/C rich sequences in pUC19 DNA, while 5 and 6 display a binding specificity to the G/C and A/T rich regions, respectively. These findings were further supported by molecular docking. The cellular uptake studies suggested that 2 was deposited mostly in the membrane fraction of the cells. Among the present complexes, 2 exhibited a very strong cytotoxic effect on A549, MCF-7, HT-29 and DU-145 cancer cells, being more potent than cisplatin. Moreover, 2 induces cell death through the apoptotic mode obtained by flow cytometry. [ABSTRACT FROM AUTHOR]

The one-pot synthesis of 1,2-disubstituted benzimidazoles by the transfer hydrogenation of azobenzene, using benzylamine as a hydrogen donor, sequential rearrangement of hydrazobenzene to semidine and further condensation with N-benzylideneamine is reported, catalyzed by 2 mol% of [Ni(COD)2] : dippe. The N2 substitution on benzimidazole can be controlled by the selection of different azobenzenes and C2 substitution will only depend on the chosen benzylamine. The current methodology avoids the addition of external oxidants, which are needed in the classical benzimidazole synthesis. In addition, the byproduct, N-benzylideneamine, obtained from dehydrogenation of benzylamine produced 2,4,5-trisubstituted imidazolines by cyclization and C–H functionalization, and this route was optimized with the use of 2 mol% of [Ni(COD)2] : 2PPh3. [ABSTRACT FROM AUTHOR]

A new series of glycosylated Pt(iv) complexes were designed, synthesized and evaluated for antitumor activities in vitro and in vivo. The incorporation of glycosyl groups to the Pt(iv) system has much influence on the antitumor abilities. Four lead compounds with activities comparable or even superior to cisplatin and oxaliplatin are screened out. These Pt(iv) complexes could be reduced to release Pt(ii) complexes and cause the death of tumour cells. The apoptosis-inducing properties of these compounds are similar to cisplatin. The accumulation of the glycosylated Pt(iv) complexes in cells and DNA is higher than cisplatin and oxaliplatin. The in vivo assay demonstrates that the tested compounds inhibit the growth of HepG2 tumors with low toxicity. [ABSTRACT FROM AUTHOR]

The reaction of ligand L, N,N-bis(pyridin-2-ylmethyl)acetamide, with five transition metal salts, FeCl3·6H2O, CuCl2·2H2O, Cu(ClO4)2·6H2O, ZnCl2 and K2PtCl4/KI, produced five metal complexes, [(μ-O)(FeClL′)(FeCl3)] (1), [CuLCl2] (2), [CuBPA(ClO4)(CHCN)] ClO4 (3), [ZnLCl2] (4) and [PtLI2] (5), where L′ = 1-(2,4,5-tri(pyridin-2-yl)-3-(pyridin-2-ylmethyl)imidazolidin-1-yl)ethanone which formed in situ, and BPA = bis(pyridin-2-ylmethyl)amine. The ligand and complexes were characterized by a variety of spectroscopic techniques including X-ray single crystal diffraction where applicable. Depending on the metal ion and auxiliary ligand of the complex, the acetyl group of the ligand L could be either intact or cleaved. When ferric chloride hexahydrate was used, the deacetylation proceeded even further and a novel heterocyclic compound (L′) was formed in situ. A possible mechanism was proposed for the formation of the heterocyclic compound found in complex 1. Our results indicate that to cleave effectively an amide bond, it is essential for a metal centre to bind to the amide bond and the metal centre is of sufficient Lewis acidity. [ABSTRACT FROM AUTHOR]

Ligands based upon 4-carboxamide-2-phenylquinoline derivatives have been synthesised with solubilising octyl hydrocarbon chains and tethered aromatic chromophores to give naphthyl (HL2), anthracenyl (HL3) and pyrenyl (HL4) ligand variants, together with a non-chromophoric analogue (HL1) for comparison. 1H NMR spectroscopic studies of the ligands showed that two non-interchangeable isomers exist for HL2 and HL4 while only one isomer exists for HL1 and HL3. Supporting DFT calculations on HL4 suggest that the two isomers may be closely isoenergetic with a relatively high barrier to exchange of ca. 100 kJ mol−1. These new ligands were cyclometalated with Pt(ii) to give complexes [Pt(L1–4)(acac)] (acac = acetylacetonate). The spectroscopically characterised complexes were studied using multinuclear NMR spectroscopy including 195Pt{1H} NMR studies which revealed δPtca. −2785 ppm for [Pt(L1–4)(acac)]. X-ray crystallographic studies were undertaken on [Pt(L3)(acac)] and [Pt(L4)(acac)], each showing the weakly distorted square planar geometry at Pt(ii); the structure of [Pt(L3)(acac)] showed evidence for intermolecular Pt–Pt interactions. The UV-vis. absorption studies show that the spectral profiles for [Pt(L2–4)(acac)] are a composite of the organic chromophore centred bands and a broad 1MLCT (5d →π*) band (ca. 440 nm) associated with the complex. Luminescence studies showed that complexes [Pt(L2–4)(acac)] are dual emissive with fluorescence characteristic of the tethered fluorophore and long-lived phosphorescence attributed to 3MLCT emission. In the case of the pyrenyl derivative, [Pt(L4)(acac)], the close energetic matching of the 3MLCT and 3LCpyr excited states led to an elongation of the 3MLCT emission lifetime (τ = 42 μs) under degassed solvent conditions, suggestive of energy transfer processes between the two states. [ABSTRACT FROM AUTHOR]

To focus on the high importance of low-valent main group metal complexes, which can be applied to catalytic transformations, this article deals with the promising new ligand system (4-MeNCOC6H3)2CH2 (1). It is patterned on the well known nacnac ligand and further development of the parent bisheterocyclo methanes. In comparison with the results of previous studies based on the bisheterocyclo methanes (NCOC6H4)2CH2 and (NCOC6H4)2CH2 derivative 1 was modified by adding a methyl group to the annulated benzene perimeters to enhance the steric protection of a potentially coordinated main group metal cation. On reaction of 1 with group 13 trimethyl reagents and dialkyl aluminium halides the ligand backbone gets deprotonated and the two endocyclic nitrogen donor atoms coordinate with the remaining organometallic fragment to form a six-membered metalla heterocycle. The synthesis of [Me2Al{(4-MeNCOC6H3)2CH}] (2), [Me2Ga{(4-MeNCOC6H3)2CH}] (3), [Me2In{(4-MeNCOC6H3)2CH}] (4), [ClMeAl{(4-MeNCOC6H3)2CH}] (5), [IMeAl{(4-MeNCOC6H3)2CH}] (6) and [IEtAl{(4-MeNCOC6H3)2CH}] (7) could be accomplished. A structural comparison of those metallated species based on single crystal X-ray analyses identifies them as ideal precursors generating new low-valent main group complexes. [ABSTRACT FROM AUTHOR]

Two “end-off” compartmental ligands, 2-formyl-4-chloro-6-N-ethylmorpholine-iminomethyl-phenol (HL1) and 2-formyl-4-methyl-6-N-ethylpyrrolidine-iminomethyl-phenol (HL2) have been designed and three complexes of Mn(ii), one mono-, one di- and a polynuclear, namely Mn(L1)(SCN)2(H2O)] (1), [Mn2(L1)(OAc)2](BPh4)] (2), and [Mn2(L2)(OAc)2(dca)]n (3) have been synthesized and structurally characterized. Variable temperature magnetic studies of 2 and 3 have been performed and data analyses reveal that Mn centers are antiferromagnetic coupled with J = −9.15 cm−1 and J = −46.89, respectively. Catecholase activity of all the complexes has been investigated using 3,5-di-tert-butyl catechol (3,5-DTBC). All are highly active and the activity order on the basis of the kcat value is 2 ＞ 1 ＞ 3. In order to unveil whether the metal centered redox participation or the radical pathway is responsible for the catecholase-like activity of the complexes, detailed EPR and cyclic voltammetric (CV) studies have been performed. In addition to the six-line EPR spectrum characteristic to Mn(ii), an additional peak at g∼ 2 is observed when the EPR study is done with the mixture of 3,5-DTBC and the catalyst, suggesting the formation of an organic radical, most likely ligand centered. The CV experiment with the mixture of 3,5-DTBC and the catalyst reveals ligand centered reduction rather than reduction of Mn(ii) to Mn(i). It is thus inferred that complexes 1–3 show catecholase-like activity due to radical generation. [ABSTRACT FROM AUTHOR]

We have synthesized four Ir(iii) metal complexes (1–4) bearing dual fluorine-free cyclometalates that are derived from 2′,6′-dimethoxy-4-t-butyl-2,3′-bipyridine (pypy)H or 2-(2,4-dimethoxypyrimidin-5-yl)-4-t-butylpyridine (pmpy)H and a third ancillary, e.g. 5-pyridin-2-yl-pyrazolate (Pz) or 5-pyridin-2-yl-pyrrolide (Pr), respectively. The Ir(iii) complexes 3 and 4 were examined by X-ray diffraction studies for providing the structural proofs. Photophysical properties were next measured in CH2Cl2 at RT, among which the pypy complexes 1 and 2 showed an identical structured emission with an E0-0 peak located at 458 nm, while the corresponding pmpy derivative 3 displayed the most blue-shifted E0-0 peak at 444 nm. Organic light-emitting diodes (OLEDs) were fabricated using multiple layered architecture and the aforementioned phosphor at 8 wt% doping level. The associated OLED performances, cf. max. E.Q.E. = 9.0%, 14.3%, 5.8% and 9.4% and CIEx,y coordinates at (0.16, 0.22), (0.16, 0.24), (0.16, 0.17) and (0.16, 0.20) at 100 cd m−2 for phosphors 1–4 in sequence, confirmed their potential to act as blue dopants for phosphorescent OLEDs. [ABSTRACT FROM AUTHOR]

A series of mono- and bi-metallic metal complexes (with CuII, PtII and ZnII) with substituted polypyridyl ligands have been prepared and their binding affinities towards quadruplex (c-Myc and human telomeric) and duplex DNA (ds26 and calf thymus) determined using fluorescent indicator displacement (FID) assays and UV/vis spectroscopic titrations. These studies have shown that the number of aromatic rings and number/position of cyclic amine substituents on the ligands, play an important role in defining the DNA binding abilities of the resulting metal complexes. We also show that bi-metallic complexes prepared using a novel terpyridine-cyclen ligand have higher affinity towards G-quadruplex DNA as compared to their mono-metallic counterparts. Cytotoxicity assays were carried out for all the new complexes against an osteosarcoma cancer cell line (U2OS) as well as a normal fibroblast cell line (GM05757). Several of these compounds displayed cytotoxicity similar to that of cisplatin. [ABSTRACT FROM AUTHOR]

The synthesis, stoichiometry, and structural characterization of a homoleptic, cationic europium(iii) complex with three neutral tetraalkyldiglycolamide ligands are reported. The tri (bismuth tetrachloride)tris- (N,N,N',N'-tetra-n-octyldiglycolamide)Eu salt, [Eu(TODGA)3][(BiCl4)3] obtained from methanol was examined by Eu L3-edge X-ray absorption spectroscopy (XAS) to reveal an inner-sphere coordination of Eu3+ that arises from 9 O atoms and two next-nearest coordination spheres that arise from 6 carbon atoms each. A structural model is proposed in which each TODGA ligand with its O = Ca - Cb - O - Cb - Ca = O backbone acts as a tridentate O donor, where the two carbonyl O atoms and the one ether O atom bond to Eu3+. Given the structural rigidity of the tridentate coordination motif in [Eu(TODGA)3]3+ with six 5-membered chelate rings, the six Eu-Ca and six Eu-Cb interactions are readily resolved in the EXAFS (extended X-ray absorption fine structure) spectrum. The three charge balancing [BiCl4]- anions are beyond the cationic [Eu(TODGA)3]3+ cluster in an outer sphere environment that is too distant to be detected by XAS. Despite their sizeable length and propensity for entanglement, the four n-octyl groups of each TODGA (for a total of twelve) do not perturb the Eu3+ coordination environment over that seen from previously reported single-crystal structures of tripositive lanthanide (Ln3+) complexes with tetraalkyldiglycolamide ligands (of the same 1: 3 metal-to-ligand ratio stoichiometry) but having shorter /-propyl and /-butyl groups. The present results set the foundation for understanding advanced solvent extraction processes for the separation of the minor, tripositive actinides (Am, Cm) from the Ln3+ ions in terms of the local structure of Eu3+ in a solid state coordination complex with TODGA. [ABSTRACT FROM AUTHOR]

A series of six-coordination copper(II) complexes containing bis(3,5-di-t-butylpyrazol-1-yl)acetate (bdtbpza) and N-heterocycles or chelating aliphatic ligands have been synthesized. The steric bulkiness of bis(pyrazol-1-yl)acetate anchors two bdtbpza to situate a trans position and to adopt an O-bound monodentate coordination mode with other nitrogen bases occupying the basal plane. Five mononuclear mixed ligand complexes, [Cu(bdtbpza)2(py)4] 1, [Cu(bdtbpza)2(t-Bupy)4] 2, [Cu(bdtbpza)2(pym)2(MeOH)2] 3, [Cu(bdtbpza)2(eda)2] 4, [Cu(bdtbpza)2(tmeda)(H2O)2] 5, where py = pyridine, t-Bupy = tert-butylpyridine, pym = pyrimidine, eda = ethylenediamine, and tmeda = tetramethylethylenediamine, were isolated and thoroughly characterized. Intriguingly, the heteroleptic complex 5, which has two aquo-ligands oriented in the cis positions, demonstrates higher catecholase-like activity in performing aerial oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) than other bis(pyrazolyl)-acetate-embedded copper complexes reported herein, which suggests the essential role of labile cisaquo ligands to promote the catalytic reaction. [ABSTRACT FROM AUTHOR]

Lithiation of the sterically demanding bis(iminophosphoranyl)methane H2C{Ph2P(vNDip)}2 (Dip = 2,6-iPr2C6H3), H2L, with alkyllithium reagents afforded the methandiide complexes [(LLi2)2] 2, [LLi2(OEt2)2] 4, [LLi2(THF)3] 5, [LLi2(THF)2] 6, and [LLi2(PMDTA)] 7 (PMDTA = N,N,N',N'',N''-pentamethyldiethylenetriamine), from various solvents or after the addition of donor molecules. The complex [HC(Ph2PNDip)(Ph2P)Li-(THF)2] 3 was further identified as a by-product under certain conditions. Further lithiation of the methandiide in ortho-position of one P-bound phenyl group affords complexes of the trianionic ligand L'3-, and the complexes [(L'Li3)2] 8 and [L'Li3(THF)4] 9 were obtained. Different isomeric forms for the methandiide units investigated in solution and in the solid state are described, and the crystal structures of complexes 2, 3, and 5-9 are reported. [ABSTRACT FROM AUTHOR]

Using an interlocking co-complexation approach, a homologous series of unsolvated alkali-metal zincates [MZn(CH2SiMe3)3] (M = Li 1, Na 2, K 3) was prepared by reacting equimolar amounts of Zn(CH2SiMe3)2 with the relevant alkali-metal alkyl M(CH2SiMe3) employing non-coordinating hexane as a solvent. X-ray crystallographic studies reveal that these heterobimetallic compounds exhibit unprecedented supramolecular assemblies made up exclusively of a three-fold combination of M-CH2, Zn-CH2 and M...Me interactions. Revealing an important alkali-metal effect, 1 displays a linear chain structure; whereas 2 and 3 form much more intricate 3D and 2D coordination networks respectively. Shedding new light into the formation of these solvent-free zincates, DFT calculations indicate that the infinite degree of aggregation observed in 1-3 plays a major role in thermodynamically driving the co-complexation reactions of their homometallic precursors. NMR spectroscopic studies suggest that in C6D6 solution 1-3 exist as discrete contacted ion-pair species, where the alkali-metal is partially solvated by molecules of deuterated solvent. The supramolecular assemblies of 1-3 can be easily deaggregated by adding the polydentate N-donors PMDETA (N,N,N',N'',N''-pentamethyldiethylenetriamine) or TMEDA (N,N,N',N'- tetramethylethylenediamine), affording monomeric [(PMDETA)LiZn(CH2SiMe3)3] (4) and [(TMEDA)2NaZn-(CH2SiMe3)3] (5). [ABSTRACT FROM AUTHOR]

A series of heteroleptic strontium complexes (1-9) using a combination of different aminoalkoxides and 2,2,6,6-tetramethyl-3,5-heptanedionate (tmhd) were prepared to examine the effect of the bulkiness and coordination ability of the aminoalkoxide ligand in these complexes as well as potential strontium precursors. All complexes were characterized by FT-IR, FT-NMR, elemental analyses, and thermo-gravimetric (TG) analyses. The crystal structure analyses of 1, 2, 4, and 5 demonstrate their stability in the dimer form and the unwillingness of the strontium atom to form more than six coordination bonds in these complexes. The complex 5 shows an unusual picture: the existence of one hexa-coordinated and one pentacoordinated strontium atom side by side in its dimer structure. The introduction of ether groups as coordination sites in complexes 6-9 led to a decrease in steric hindrance which resulted in the formation of the complex 7 as a tetramer. The complex 7 shows a unique Sr4O4 cubane core where oxygen atoms undergo μ3-bridging between strontium atoms. The TG analyses show that the complexes exhibit a stepwise decomposition character, with the major mass losses in the region 150-400 °C. [ABSTRACT FROM AUTHOR]

The reaction of Ap9MeLu(CH2SiMe3)2(thf) (Ap9Me = (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)-pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH3 affords a trinuclear alkyl-hydrido cluster [(Ap9MeLu)3(μ²-H)3(μ³-H)2(CH2SiMe3)(thf)2]. The analogous reactions with Ap9MeLn(CH2SiMe3)2(thf) (Ln = Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido complexes [(Ap9MeLn)3(μ²-H)3(μ³-H)2(CH2SiMe3)(thf)2] and [(Ap9MeLn)3(μ²-H)3(μ³-H)2(CH2SiH2Ph)(thf)2] differing in the alkyl group. The DFT calculations of [(Ap*Y)3(μ²-H)3(μ³-H)2(CH2SiMe3)(thf)2] (Ap* = (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the HOMO on the Ap*-Y(1A)-CH2SiMe3 fragment, thus explaining its enhanced reactivity. Analysis of the electron density distribution reveals the Y-H and H-H bonding interactions in the (Y)3(μ²-H)3(μ³-H)2 moiety. The NMR studies of diamagnetic complexes [(Ap9MeLu)3(μ²-H)3(μ³-H)2(CH2SiMe3)(thf)2] and [(Ap*Y)3(μ²-H)3(μ³-H)2(CH2SiMe3)(thf)2] demonstrated that the trinuclear cores are retained in the solution and revealed exchange between μ³- and μ²-bridging hydrido ligands. Complexes [(Ap*Ln)3(μ²-H)3-(μ³-H)2(CH2SiMe3)(thf)2], the cationic yttrium hydrido cluster [(Ap*Y)3(μ²-H)3(μ³-H)2(thf)3]+[B(C6F5)4]- as well as [(Ap9MeLn)3(μ²-H)3(μ³-H)2(CH2SiMe3)(thf)2] proved to be active in catalysis of ethylene polymerization under mild conditions. [ABSTRACT FROM AUTHOR]

The reaction of 2-{[2-(1H-imidazol-4-yl)-ethylimino]-methyl}-phenol (L1), 2,4-di-tert-butyl-6-{[2-(1Himidazol- 4-yl)-ethylimino]-methyl}-phenol (L2) or 4-tert-butyl-2-{[2-(1H-imidazol-4-yl)-ethylimino]- methyl}-phenol (L3) with iron(II) precursors produced either iron(II) or iron(III) complexes, depending on the nature of the anions in the iron(II) precursor and the ligand. When the anion is chloride and the ligand L1, the product is [(L1)2Fe][FeCl4] (1), but when the anion is triflate (OTf-) and the ligand is L2, the product is [(L2)2Fe][OTf]2 (2). With iron(II) halides and tert-butyl groups on the phenoxy ligands L2 and L3, the iron(III) complexes [(L2)FeX2] {where X = Cl (3), Br (4) and I = (5)} and [(L3)FeCl2] (6) were formed. Complexes 1-6 were characterised by a combination of elemental analyses, IR spectroscopy and mass spectrometry; and in selected cases (3 and 4) by single crystal X-ray crystallography. The crystal structures of 3 and 4 indicated that the iron(II) precursors oxidised to iron(III) in forming complexes 3-6; an observation that was corroborated by the magnetic properties and the 57Fe Mössbauer spectra of 3 and 4. The iron(III) complexes 3-6 were used as pre-catalysts for the oligomerisation and polymerisation of ethylene. Products of these ethylene reactions depended on the solvent used. In toluene ethylene oligomerised mainly to 1-butene and was followed by the 1-butene alkylating the solvent to form butyl-toluenes via a Friedel-Crafts alkylation reaction. In chlorobenzene, ethylene oligomerised mainly to a mixture of C4-C12 alkenes. Interestingly small amounts of butyl-chlorobenzenes and hexyl-chlorobenzenes were also formed via a Friedel-Crafts alkylation with butenes and hexenes from the oligomerisation of ethylene. [ABSTRACT FROM AUTHOR]

The tris(2-mercapto-1-methylbenzimidazolyl)hydroborato cadmium complexes, {[TmMeBenz]Cd(μ-Cl)}2 and [TmMeBenz]CdI, have been synthesized via the reactions of [TmMeBenz]K with CdCl2 and CdI2, respectively. While X-ray diffraction studies demonstrate that the iodide derivative, [TmMeBenz]CdI, is a monomer, the chloride derivative, {[TmMeBenz]Cd(μ-Cl)}2, exists as a dimer, which is unprecedented for Group 12 [TmR]MX (X = Cl, Br, I) compounds. Furthermore, the cadmium centers of {[TmMeBenz]Cd(μ-Cl)}2 are trigonal bipyramidal, which is an uncommon motif for cadmium complexes with a [S3Cl2] coordination sphere. [ABSTRACT FROM AUTHOR]

A series of new N-heterocyclic carbene palladium complexes bearing AsPh3 and SbPh3 functions PdCl2(IMes)(AsPh3) (1a), PdCl2(IMes)(SbPh3) (1b), PdCl2(IPr)(AsPh3) (1c), PdCl2(IPr)(SbPh3) (1d), PdCl2(SIMes)- (AsPh3) (2a), PdCl2(SIMes)(SbPh3) (2b), PdCl2(SIPr)(AsPh3) (2c), and PdCl2(SIPr)(SbPh3) (2d) (IMes = N,N'-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene; IPr = N,N'-bis-(2,6-di(iso-propyl)phenyl)imidazol- 2-ylidene; SIMes = N,N'-bis-(2,4,6-trimethylphenyl)imidazolidin-2-ylidene; SIPr = N,N'-bis-(2,6-di(isopropyl) phenyl)imidazolidin-2-ylidene) was synthesized and fully characterized by 1H NMR, 13C NMR, and FT-IR spectroscopy, elemental analysis and single-crystal X-ray crystallography. The catalytic potential of these arsine and stibine-stabilized carbene palladium complexes for Pd-mediated transformations was investigated with various substrates in the Hiyama cross-coupling reactions and Buchwald-Hartwig aminations. The results demonstrate that these complexes show high catalytic activity and good tolerance to various chemical functions. [ABSTRACT FROM AUTHOR]

Five new metal complexes, {[Ni(DIDP)(m-bdc)(H2O)]·5H2O}n (1), {[Zn(DIDP)(hfipbb)]·2DMA}n (2), {[Zn-(DIDP)(4,4'-sdb)]·H2O}n (3), {[Co(DIDP)(p-bdc)]}n (4), and {[Co2(DIDP)(hfipbb)2]·H2O}n (5), have been synthesized by reactions of the corresponding metal ions with a V-shaped ligand 2,8-di(1H-imidazol-1-yl)- dibenzothiophene (DIDP) and different aromatic dicarboxylic acids, namely isophthalic acid (m-H2bdc), terephthalic acid (p-H2bdc), 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb), and 4,4'-sulfonyldicarboxylic acid (4,4'-H2sdb), respectively. The structures of the complexes were determined by X-ray single-crystal diffraction. Complex 1 is a 1D chain structure containing a one-dimensional channel along the a direction and is further extended via O-H...S hydrogen bonds and C-H...π stacking interactions into a 3D framework. Complex 2 exhibits a quasi 2D + 2D → 2D with parallel polycatenation of 2D (4, 4) nets. Complex 3 displays an unusual 2D + 2D → 3D parallel polycatenated framework based on a 2D 63-hcb network. Complex 4 shows a 2D 4-connected {44·6²}-sql network containing a one-dimensional channel along the b direction. The adjacent 2D networks are further extended via C-H...O hydrogen bonds into a 3D supramolecular framework. Complex 5 features a 2-fold interpenetrating 3D framework with a 6-connected {412·6³} pcu topology. Furthermore, the thermal stability for 1-5 and luminescence properties of 2 and 3 have been studied. Moreover, the solid-state UV-visible spectroscopy experiments show that complexes 1-5 are all optical semiconductors with band gaps of 3.06, 3.18, 3.23, 2.98, and 3.17 eV, respectively. [ABSTRACT FROM AUTHOR]

Eighteen Mn complexes with N-donor and carboxylate ligands have been synthesized and characterized. Three Mn complexes among them are new and are reported for the first time. The reactions of oxygen evolution in the presence of oxone (2KHSO5·KHSO4·K2SO4) and cerium(IV) ammonium nitrate catalyzed by these complexes are studied and characterized by UV-visible spectroscopy, X-ray diffraction spectrometry, dynamic light scattering, Fourier transform infrared spectroscopy, electron paramagnetic resonance spectroscopy, transmission electron microscopy, scanning electron microscopy, membrane-inlet mass spectrometry and electrochemistry. Some of these complexes evolve oxygen in the presence of oxone as a primary oxidant. CO2 and MnO4 - are other products of these reactions. Based on spectroscopic studies, the true catalysts for oxygen evolution in these reactions are different. We proposed that for the oxygen evolution reactions in the presence of oxone, the true catalysts are both high valent Mn complexes and Mn oxides, but for the reactions in the presence of cerium(IV) ammonium nitrate, the active catalyst is most probably a Mn oxide. [ABSTRACT FROM AUTHOR]

Eleven heteroleptic Bi(V) complexes of the form [BiPh3(O2CR)2] have been synthesised and fully characterised. The carboxylate ligands are derived from a series of simple substituted benzoic acids, four of which are common non-steroidal anti-inflammatories (NSAIDs). The solid-state structures of eight of the complexes were determined by single crystal X-ray diffraction, and all were shown to adopt a typical trigonal bipyramidal geometry with chelating carboxylate ligands. Nine of the complexes were assessed for their anti-parasitic activity against Leishmania major promastigotes and their cytotoxicity towards human fibroblasts. The assays indicated that while the complexes showed good anti-leishmanial activity with IC50 values ranging from 0.6 to 2.5 μM they were also non-selectively toxic towards the fibroblasts at similar or slightly higher concentrations. Using 1H NMR, the stability of one of the complexes, [Bi(C6H5)3(O2CC6H3(m-OH)2)2] was studied in water, DMSO and in the DMEM culture medium. This showed that while the Bi(V) complex was stable in D2O and DMSO, the complex slowly decomposed in the culture medium undergoing reduction to give BiPh3 and the free acid. Since the acids and BiPh3 were not toxic to either the parasites or fibroblasts at the concentrations studied, the implication is that the Bi(V) complexes are stable enough for long enough to have significant in vitro anti-parasitic activity. [ABSTRACT FROM AUTHOR]

The coordination properties of phosphinoferrocene oxazolines with Group 11 metal ions were probed through a series of reactions between various metal precursors and the model ligand, rac-1-[4,5-dihydro-4,4-dimethyl-2-oxazolyl]-2-(diphenylphosphino)ferrocene (1). The reactions of 1 with CuX and AgCl produced the halide-bridged dimers [M(μ-X)(1-κ2N,P)], where M/X = Cu/Cl (2a), Cu/Br (2b), Cu/I (2c), and Ag/Cl (3), whereas the reaction with [AuCl(tht)] (tht = tetrahydrothiophene) yielded the chlorogold(i) complex [AuCl(1-κP)] (4). When metal precursors without strongly coordinating halide ligands were used (viz., [Cu(MeCN)4][PF6] and AgClO4), the complexation reactions generated bis-chelate complexes [M(1-κ2N,P)2]X (5: M/X = Cu/PF6, 6: M/X = Ag/ClO4). A similar reaction with [Au(tht)2]ClO4 produced [Au(1-κP)2]ClO4 (7), wherein the gold centre is linearly coordinated by two phosphine moieties. All complexes except for 4 were structurally authenticated by X-ray crystallography. The observed coordination behaviour and structures of the isolated complexes are discussed in the context of the catalytic properties of chiral ligands structurally related to the model compound 1. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation of anodic metals (M = cobalt, nickel, copper, zinc and cadmium) in a solution of the ligand 1H-anthra[1,2-d]imidazol-6,11-dione-2-[2-hydroxyphenyl] [H2L] afforded homoleptic [ML] compounds. The addition to the electrochemical cell of coligands (L′) such as 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) allowed the synthesis, in one step, of heteroleptic [MLL′] compounds. The crystal structures of H2L (1), [CoL(MeOH)]2 (2), [CoL(phen)]2 (3), [NiL(bpy)]2 (4), [CuL(bpy)] (5), [CuL(phen)] (6) and [CdL(bpy)]2 (7) have been determined by X-ray diffraction techniques. The crystal structures of 2, 3, 4 and 7 consist of dimeric species in which both metallic atoms are connected through two phenolate bridges in a penta-coordinated (2) or hexa-coordinated (3, 4 and 7) environment. Copper compounds 5 and 6 are monomeric species with the metal in a pentacoordinated [N4O] environment. In all the compounds, the main interactions responsible for the crystal packing are classic (N–H…O, O–H…N and O–H…O) and non-classic (C–H…O and C–H…N) hydrogen bond interactions, and π interactions (π–π-stacking and C–H…π). All compounds were also characterized by microanalysis, IR spectroscopy, FAB mass spectrometry and 1H NMR spectroscopy. Magnetic susceptibility data were measured for 2–4 over the temperature range 2–300 K, and their analysis has revealed the occurrence of intramolecular antiferromagnetic coupling for 2 (J = −2 cm−1) and ferromagnetic coupling for 3 (J = 7.8 cm−1) and 4 (J = 2.8 cm−1) [J being the isotropic magnetic coupling parameter]. The nature of the magnetic coupling in 2–4 is correlated with the magnitude of the M–Ophenolate–M angle between the phenolate bridge and the metallic centers [M(ii) = Co, Ni]. The in vitro antimicrobial properties of the novel ligand and its metal complexes were detected against Gram positive and Gram negative bacteria and fungi. [NiL(bpy)]2 and all tested Cd(ii) complexes were the most active compounds, showing the highest inhibitory effect against bacilli (MIC 1.5–3 μg mL−1) and Sarcina, Streptococci and Haemophilus influenzae bacterial strains (MIC 12–50 μg mL−1), while almost no antifungal properties were observed. [ABSTRACT FROM AUTHOR]

Benzimidazoles are chemically and pharmaceutically important, and an environmentally benign synthetic method based on acceptorless dehydrogenative condensation of primary alcohols and benzene-1,2-diamine is developed in this work. Three Ru(ii) hydride complexes [RuHCl(CO)(PNS(O))] (containing two isomers 1a and 1b) and [RuHCl(CO)(PPh3)(SNCNHC)]PF6 (2) based on two new quinoline-based ligands 2-(diphenylphosphanylmethyl)-8-phenylsulfinylquinoline (PNS(O)) and 1-mesityl-3-(8-phenylthioquinolyl-2-methyl)-2-imidazole carbene (SNCNHC) are prepared and fully characterized. These complexes catalyse the condensation of benzyl alcohol and benzene-1,2-diamine to 2-phenylbenzimidazole with the liberation of H2, and the catalytic activity follows the order: 1a≈1b ＞ 2. When 0.2 mol% of 1a and 2 mol% of NaBPh4 were used, various 2-functionalized benzimidazoles were obtained in good yields (70–85%) and high turnover numbers (TONs ∼ 425). This homogeneous system does not need oxidants or stoichiometric strong bases (KOH or KOtBu, etc.) that are normally used in the reported homogeneous systems, and thus is a greener process. [ABSTRACT FROM AUTHOR]

Among the coinage metal complexes displaying luminescent properties, those bearing C-donor aryl ligands have an increasing part in the chemistry of these metals. These types of ligands confer a high kinetic and thermodynamic stability on the complexes, but they can also be involved in the photoluminescent behaviour of the complexes. The development of new aryl-containing complexes of group eleven metals, the study of their photoluminescent properties and their related properties and applications are discussed in this perspective. Among these, luminescent gold(i) and gold(iii) compounds are being intensively used for the development of new properties with potential applications such as, for instance, electroluminescence, triboluminescence, mechanochromism, aggregated induced emissions, quenching, luminescent liquid crystals, low molecular weight gelators and photocatalysts, among others. [ABSTRACT FROM AUTHOR]

N,N′-Bis(2,6-R-phenyl)-2,6-pyridinedicarboxamides (L: R = Cl, L1; R = F, L2; R = H, L3; R = Me, L4; R = Et, L5; R = iPr, L6) were designed as neutral ligands, and the corresponding nickel complexes LNiBr2 (Ni1–Ni6) were synthesized as precatalysts for ethylene oligomerization. All new ligands were fully characterized by NMR, and FT-IR spectroscopy, and elemental analysis, while the nickel complexes were examined using FT-IR spectroscopy and elemental analysis. The coordination mode of the ligand with nickel in complexes Ni5 and Ni6 was tridentate (O^N^O), as established by single crystal X-ray diffractions. All the nickel complexes Ni1–Ni6 were tested for ethylene oligomerization with different alkylaluminum compounds as cocatalysts, and diethylaluminum chloride (Et2AlCl) was proved to be the most effective. Upon activation with Et2AlCl, all nickel complexes showed high catalytic activity (up to 7.55 × 105 g mol−1 (Ni) h−1 atm−1) with good selectivity for α-C4. [ABSTRACT FROM AUTHOR]

Agostic interactions are often used to activate inert C–H bonds, and thus facilitate new reactions. We report the first example of designed catalysts based on the agostic interaction. Novel copper(i) complexes [BBN(pzx)2]Cu(PPh3)n (BBN = 9-borabicyclo[3.3.1]nonane; pzx = 3-substituted pyrazole; x = H, n = 2; x = Me, n = 1) and {[BBN(pziPr)2]Cu}2 have been synthesized and characterized. Single crystal studies of the three compounds show weak intramolecular C–H…Cu interactions which can be assigned as agostic or anagostic interactions. Catalytic studies of these complexes toward carbenoid insertion into N–H bonds indicate these weak interactions act as a “switch” which will be turned “on” if interacting with the substrate and “off” if eliminating the product and regenerating the weak interaction. The process of the “switch” turning “on” or “off”, which is related to the catalytic effect, is found to be influenced by both steric effects and the solvent: a less sterically hindered catalyst in non-coordinating benzene results in high yield, while a more sterically hindered catalyst in coordinating THF results in relatively low yield. [ABSTRACT FROM AUTHOR]

The first 3H-1,3-azaphospholo-pyridines 2a–c were synthesized as racemic mixtures in modest to medium yield by the reaction of N-(2-chloropyrid-3-yl)-trimethylacetimidoyl chloride 1 with RPLi2 (R = Ph, n-Bu, i-Bu), generated from RPH2 and BuLi in THF at −70 °C, and studied with respect to their suitability as ligands (L) in transition metal complexes. Reactions of 2a with group 6 metal(0) pentacarbonyls led to P-coordinated LM(CO)5 complexes 3a–5a (Cr, Mo, W) and the reaction of 2c with (norbornadiene)Mo(CO)4 surprisingly to 4c. [Rh(1,5-COD)Cl]2 and 2a,b, in metal/ligand ratio 1 : 1, furnished LRh(1,5-COD)Cl complexes 6a,b with P-coordination, 6b accompanied by a minor contamination by the bis-coordinated L[Rh(COD)Cl]2 complex 7b. Reactions of 2a,b with [(allyl)PdCl]2 proceeded in THF with dismutation of N-coordinated (allyl)PdCl and formed with 2a a labile crude product [(2a){(allyl)PdCl}1.2(PdCl2)0.8]·C4H8O, with the composition close to L[Pd(allyl)Cl]PdCl2 THF (8a·THF), which converted during crystallization to 9a, whereas 2b directly formed the N,N′-PdCl2-bridged bis[LPd(allyl)chloride] complex 9b. Conversion of 2b with equimolar amounts of Pd(CH3CN)2Cl2 in THF, or Na2PdCl4 in methanol, gave rise to the dimeric P,N-bridging complex 10b. Crystal structure analyses of 6a (rac), 9b·2CDCl3 (meso), 10b·4.5THF and 10b·2D6-acetone (rac) provided detailed structural information. 10b, but more efficiently complexes formed in situ from 2a,b and Pd2(DBA)3 or Pd(OAc)2, catalysed the arylamination of 2-bromopyridine with 2,4,6-trimethylaniline. [ABSTRACT FROM AUTHOR]

Four Ru(ii)/Ir(iii) metalloligands have been designed and synthesized from polypyridine and bibenzimidazole (BiBzIm) organic ligands, which show strong visible light absorption via metal-to-ligand charge transfer (MLCT) transitions. Nd/Yb(iii) complexes were further assembled from these Ru(ii)/Ir(iii) metalloligands, and Ln(iii)-centered NIR emissions can be efficiently sensitized by 3MLCT states of the metalloligands in the visible-light region. The energy transfer rates for the complexes are generally in the order Nd ＞ Yb, which is due to the better matching between 3MLCT states of Ru(ii)/Ir(iii) metalloligands and densely distributed excited states of Nd(iii) ions. Long decayed lifetimes on a μs scale and high quantum yields up to 1% are obtained in these lanthanide complexes, suggesting that the Ru(ii)/Ir(iii) metalloligands can serve as a good visible light harvesting antenna to efficiently sensitize Ln(iii)-based NIR luminescence. [ABSTRACT FROM AUTHOR]

This Tutorial Review presents an overview on the synthesis, characterization and applications of metal complexes containing curcumin (=1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) and its derivatives as ligands. Innovative synthetic strategies leading to soluble and crystallizable metal curcumin complexes are outlined in detail. Special emphasis is placed on the highly promising and exciting medicinal applications of metal curcumin complexes, with the three most important areas being anticancer activity and selective cytotoxicity, anti-Alzheimer's disease activity, and antioxidative/neuroprotective effects. Overall, this Tutorial Review provides the first general overview of this emerging and rapidly expanding field of interdisciplinary research. [ABSTRACT FROM AUTHOR]

Two windmill-like Ag3Cu5 alkynyl clusters were synthesized and characterized. They display novel PL and ECL properties, which could be modified by changing the substituent on the alkynyl ligands. According to the study of electrochemical behaviours, ECL behaviours and ECL emission spectra of the Ag3Cu5 clusters, a possible ECL mechanism was proposed. [ABSTRACT FROM AUTHOR]

Base-stabilized silanone molybdenum complexes were synthesized by the oxygenation of the MvSi bond in the silyl(silylene)molybdenum complex with 1 eq. of PNO in the presence of Lewis base L. The PNOcoordinated silanone complex (L = PNO) was converted to cis-[Cp*-(OC)2.Mo{OSiMe3(OSiMeS2)}(PMe3)] in the presence of excess PMe3. [ABSTRACT FROM AUTHOR]

Zinc and aluminum complexes supported by N,N,O-chelate ligands were synthesized and characterized. The zinc complexes [Zn(Et){2-{OC(R¹)vCH}-6-(3,5-Me2C3HN2)C5H3N}]2 (R¹ = Ph, 1a; R¹ = But, 1b) were synthesized by reaction of ligand precursors 2-{R¹C(O)CH2}-6-(3,5-Me2C3HN2)C5H3N (R¹ = Ph, HL¹; R¹ = But, HL²) with ZnEt2. The aluminum complexes [Al(R)2{2-{OC(Ph)vCH}-6-(3,5-Me2C3HN2)C5H3N}] (R = Me, 2a; R = Et, 2b) were synthesized by reaction of HL¹ with AlMe3 or AlEt3. Similar treatment of the ligand precursor 2-{Ph2C(OH)CH2}-6-(3,5-Me2C3HN2)C5H3N (HL³) with AlMe3 or AlEt3 afforded aluminum complexes [Al(R)2{2-{OC(Ph)2CH2}-6-(3,5-Me2C3HN2)C5H3N}] (R = Me, 3a; R = Et, 3b). The complexes were characterized by ¹H and 13C{¹H} NMR spectroscopy, elemental analyses and single crystal X-ray diffraction (for 1a, 1b, 2b and 3a). All the complexes are active to catalyze the ring-opening polymerization of ε-caprolactone in the presence of BnOH, leading to polycaprolactone with good molecular weight control and relatively narrow molecular weight distribution. The zinc complexes/BnOH showed good catalytic activity for the ring-opening polymerization of rac-lactide, displaying good molecular weight control and very narrow molecular weight distributions. The PLA catalyzed by complex 1a/BnOH showed somewhat hetero-stereoselectivity with Pr up to 0.73 when the polymerization was performed in THF at 0 °C. Complex 1a/BnOH also catalyzed block copolymerization of ε-CL and rac-LA with good molecular weight control of the polymer. Kinetic studies of the polymerization reactions were performed. [ABSTRACT FROM AUTHOR]

Reaction of the lithiated N-heterocyclic carbene [:C[N(2,6-iPr2C6H3)]2(CH)CLi]n (LiIPr) with KOtBu in diethylether (Et2O) afforded the novel organo-potassium compound [:C[N(2,6-iPr2C6H3)]2(CH)CK(THF)2] (KIPr·2THF). Both LiIPr and KIPr can be interpreted as ditopic carbanionic carbenes (or alkali metal salts of anionic "dicarbenes") and are interesting precursors for the synthesis of novel metal complexes bearing carbanionic carbenes as ligands. Reaction of KIPr with M[N(SiMe3)2]2 (M = Zn, Sn) afforded salts of the anionic three coordinate complexes [M{C(CH)[N(2,6-iPr2C6H3)]2C:}{N(SiMe3)2}2]- (M = Zn (1) and Sn (2)). Contrasting reactivity was observed for the other group 14 bis-amide compounds M[N(SiMe3)2]2 (M = Ge, Pb), which initially appear to yield analogous 1:1 complexes (M = Ge (3) and Pb (4)), however over time give rise to compounds bearing two ditopic carbanionic carbenes ([M{C(CH)[N(2,6-iPr2C6H3)]2C:}2-{N(SiMe3)2}]-; Ge (5) and Pb (6)) and the tris-amide anions ([M{N(SiMe3)3}]-), presumably via a Schlenktype equilibrium. Compounds 5 and 6 can be directly synthesized by reacting M[N(SiMe3)2]2 (M = Ge, Pb) with two equivalents of KIPr, respectively. [ABSTRACT FROM AUTHOR]

Reactions of a pincer ligand 2-(1H-pyrazol-1-yl)-6-(1H-pyrazol-3-yl)pyridine (pzpypzH) with Cu(NO3)2, Cu(ClO4)2, CuSO4, CuCl2 or CuI produced three dinuclear Cu(II) complexes [{Cu(NO3)}(µ-pzpypz)]2 (1), [{Cu(ClO4)}(μ-pzpypz)]2 (2), [Cu2(μ-SO4)(μ-pzpypz)2]·2MeOH (3·2MeOH), one mononuclear Cu(II) complex [CuCl2(pzpypzH)] (4) and one trinuclear Cu(I)/Cu(II) complex [(ICu)(μ-I)2Cu2(μ-pzpypz)2] (5), respectively. Treatment of 4 with two equiv. of AgNO3 in DMF also gave rise to 1. Complexes 1-5 were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 or 2 has a dimeric structure in which two {Cu(X)} (X = NO3, ClO4) fragments are interconnected by two μ-pzpypz- ligands. 3 also adopts a dimeric structure in which two Cu(II) centers are interconnected by a pair of μ-pzpypz- ligands and one μ-SO42- ion. The Cu(II) center in 4 is five-coordinated by three N atoms of the pzpypzH ligand and two Cl atoms. In 5, two Cu(II) centers are bridged by two μ-pzpypz- ligands and one CuI32- unit, forming a unique trinuclear structure. Complexes 1-5 displayed high catalytic activity toward the ammoxidation of alcohols to nitriles and the aerobic oxidation of alcohols to aldehydes in H2O. The nitrile or aldehyde products could be readily separated from the catalytic system by extraction and the residual aqueous solution containing 1 retained good activity for several cycles. [ABSTRACT FROM AUTHOR]

Three bis(1,2,3-triazolylidene) silver(I) complexes were synthesized, and the ruthenium complexes ([RCH2N2(NMe)C2Ph)]RuCl2(p-cymene) (R = C6H2Me3 4a1, C6H2iPr3 4b1) were isolated as major products with the minor C(sp²)-H activated products ([RCH2N2(NMe)C2C6H4)]RuCl(p-cymene) (R = C6H2Me3 4a2, C6H2iPr3 4b2). In the related case where R = Ph, the species ([PhCH2N2(NMe)C2Ph)]RuCl2(p-cymene) 4c1 was obtained with two C(sp²)-H activated products [PhCH2N2(NMe)C2C6H4)]RuCl(p-cymene) 4c2 and [(C6H4)CH2N2(NMe)C2Ph)]RuCl(p-cymene) 4c3 derived from metallation of the N and C-bound arene rings. Heating a solution of 4a1 at 45 °C over three weeks resulted in a ruthenium(II)(1,2,3-triazolylidene) complex [(C6H2Me3)CH2N2(NMe)C2Ph)]RuCl2 5a, where the pendant mesityl group on the triazolylidene moiety displaced the p-cymene ligand. The complexes 4a1, 4b1, 4c1 and 5a displayed moderate catalytic activities in base-free oxidation of benzyl alcohols to benzaldehydes and oxidative homocoupling of benzyl amines to imines using oxygen as oxidant. [ABSTRACT FROM AUTHOR]