Ruthenium carbene complexes bearing an anionic carboxylate chelated to a hemilabile ligand

A series of bidentate ruthenium-based NHC complexes with the general formula [(H(2)IMes)(kappa(2)-L-COO)ClRu=CHPh)], where L is either PAr(3), HNR(2), or ROR, were prepared from commercially available [(H(2)IMes)(PCy(3))Cl(2)Ru(CHPh)] (2) and the appropriate ligand. The catalytic activities of the complexes were evaluated in ring-closing metathesis reactions. The type of donor ligand has a major impact on both the initiation behavior and also the stability of the complexes. Upon addition of CuCl to the reaction mixture the initiation is improved for the phosphine or amine containing chelates. For the P,O-chelate, the fast initiation was followed by decomposition. In the case of the N,O-containing chelate, a stable catalytic system was achieved. Trapping experiments support that the nitrogen lone-pair reversibly coordinates CuCl during the reaction.     

Benzenthiolate bridged binuclear group 12 metal complexes with TTF fused dithiolate ligand,a new synthetic approach using cluster-cracking reaction

Novel binuclear dithiolate complexes (Me4N)2[M2-(SPh)2(S2TTF(SMe)2)2] (M = Cd and Zn) have been synthesized by a new cluster-cracking method.     

Four complexes with a bulky carboxylate ligand: syntheses,crystal structures,and luminescent properties

Abstract  

Four complexes of 3,3-diphenylpropanoate (L) and 4,4′-bipyridine as auxiliary bridging ligands were synthesized and characterized, namely [Zn(L)₂(4bpy)(EtOH)₂]_∞ (1), [Co(L)₂(4bpy)(EtOH)₂]_∞ (2), [Ni(L)₂(4bpy)(EtOH)₂]_∞ (3), and [Cu(L)₂(4bpy)(H₂O)]_∞ (4) (4bpy = 4,4′-bipyridine). X-ray single-crystal diffraction analyses show that complexes 1–4 all take one-dimensional (1D) fishbone-like structures incorporating bridging 4bpy ligands. The complexes show different supramolecular frameworks interlinked via intermolecular hydrogen bonds, π···π stacking, and/or C–H···π supramolecular interactions. Complex 3 only has a simple one-dimensional fishbone-like chain, whereas complexes 1 and 2 show two-dimensional supramolecular structures by interchain C–H···O hydrogen bonds. Complex 4 is assembled into two-dimensional layers and then an overall three-dimensional framework by a combination of interchain O–H···O hydrogen bonds and C–H···π supramolecular interactions. The luminescent properties of the ligands and their complexes were investigated.     

pH-dependent self-assembly of copper(II) complexes with a new imidazole-containing polyamine ligand: Synthesis,structure and magnetic property

Four copper(II) complexes were synthesized by reactions of new imidazole-containing polyamine ligand N¹-(2-aminoethyl)-N¹-(1H-imidazol-4-ylmethyl)-ethane-1,2-diamine (HL) with Cu(ClO₄)₂ · 6H₂O under different pH and their structures were characterized by X-ray crystallography. Interestingly, the complexes have diverse structures from protonated ligand [H₃(HL)][CuCl₄] · Cl (1), dinuclear [Cu₂(HL)₂Cl](ClO₄)₃ · H₂O (2), one-dimensional chain polynuclear {[Cu(L)](ClO₄)}_n (3) to cyclic-tetranuclear [Cu₄(L)₄](ClO₄)₄ · 3CH₃CN (4) coordination compounds by varying reaction pH from acidic to basic. The results indicate that the reaction pH has great impact on the formation and structure of the complexes. The magnetic measurements show that there are antiferromagnetic interactions between the Cu(II) centers with g = 2.09, J = −39.0 cm⁻¹ and g = 2.17, J = −36.8 cm⁻¹ for 3 and 4, respectively.     

Syntheses and luminescence of three lanthanide complexes constructed by flexible carboxylate ligand

Three new complexes, namely {[Ln(L)₃(2,2′-Bipy)] _n · H₂O} (Ln = Pr (I), Sm (II), and Nd (III)) (HL = 3-(2-hydroxyphenyl)propanoic acid), have been synthesized and structurally characterized. The structural determinations indicated (CIF files CCDC nos. 1472729 (I), 1472730 (II), 1472734 (III)) that I–III have similar dinuclear structures, which can be further linked into 2D sheet via the hydrogen bond interactions. Furthermore, the luminescent properties of I–III show the strong emissive power and feature.     

Dirhodium paddlewheel with functionalized carboxylate bridges: new building block for self-assembly and immobilization on solid support

A new dirhodium(II,II) paddlewheel complex, [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)] (1), has been synthesized using a predesigned functionalized carboxylate, namely, 4-(ethoxycarbonyl)benzoate. The target product has been crystallized from the acetone solution and structurally characterized as a bis-acetone adduct, [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)(OCMe(2))(2)]·C(6)H(14) (2). By utilizing the ability of dangling ester groups to coordinate to open axial ends of neighboring dirhodium units, 1 can self-assemble to form 2D networks upon crystallization from solutions of noncoordinating solvents such as chlorobenzene and chloroform. The resulting [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)]·2C(6)H(5)Cl (3) and [Rh(2)(O(2)CC(6)H(4)COOC(2)H(5))(4)]·2CHCl(3) (4) products have microporous solid state structures with the pores filled with the corresponding disordered solvent molecules. Notably, 3 and 4 represent unique examples of 2D extended frameworks based on dirhodium tetracarboxylate paddlewheel units devoid of any exogenous ligands. In solution, the dangling ends of carboxylate bridges of 1 have been successfully utilized for condensation reaction with the selected solid support, benzylamine-functionalized polystyrene, allowing successful heterogenization of dirhodium units through the equatorial covalent attachment to the substrate. The resulting solid product was tested as a catalyst in the cyclopropanation reaction of styrene with methyl phenyldiazoacetate to show good yields and diastereoselectivity.     

Imidazole-containing chitosan derivative: a new synthetic approach and sorption properties

A novel method for the synthesis of a hetaryl-containing chelate amino polymer, namely, N-(4(5)-imidazolylmethyl)chitosan (IMC), with a degree of substitution up to 0.3 was proposed. The “synthesis in gel” approach involves direct substitution of the hydroxyl group in 4(5)-imidazolylmethanol. The structures of these polymers were confirmed by ¹H NMR data. For sorption studies, IMC samples were crosslinked with epichlorohydrin and diglycidyl ethers of ethylene glycol and diethylene glycol. The degrees of swelling and sorption properties of the polymers largely depend on the crosslinking agent and the degree of crosslinking. The sorption capacities of IMC for Au^III, Pt^IV, and Pd^II ions are higher than those of the nonmodified polymer. The extraction of noble metal ions from chloride solutions becomes more selective with increasing degree of crosslinking. The sorption capacity of IMC for Co^II and Ni^II ions is higher than those of chitosan and its known N-heterocyclic derivatives.     

N-donor effects on carboxylate binding in mononuclear iron(II) complexes of a sterically hindered benzoate ligand

Using the sterically hindered 2,6-dimesitylbenzoate ligand Mes2ArCO2-, a series of mononuclear Fe(II) carboxylate complexes has been obtained with the general formula (Mes2ArCO2)2Fe(base)2 (base = 1-methylimidazole (MeIm), pyridine (Py), 2-picoline (2-Pic), 2,5-lutidine (2,5-Lut), 2,6-lutidine (2,6-Lut), (base)2 = N,N,N',N'-tetramethylethylenediamine (TMEDA)). For the monodentate base adducts, single-crystal X-ray diffraction studies revealed several different structural types ranging from distorted tetrahedral to distorted octahedral that correlate with the degree of alpha-substitution of the N-donors. Increasing alpha-substitution leads to the lengthening of the Fe-N bond, which in turn results in a change in carboxylate binding mode from eta 1 to eta 2. We surmise that this change is due to an electrostatic effect and is driven by increasing the Lewis acidity of the Fe center. Such a simple process for inducing carboxylate shifts could play a critical role in biological systems.     

Thermodynamics, structure and properties of polynuclear lanthanide complexes with a tripodal ligand: insight into their self-assembly

Self-assembly processes between a tripodal ligand and Ln(III) cations have been investigated by means of supramolecular analytical methods. At an equimolar ratio of components, tetranuclear tetrahedral complexes are readily formed in acetonitrile. The structural analysis of the crystallographic data shows a helical wrapping of binding strands around metallic cations. The properties of this series of highly charged 3D compounds were examined by using NMR spectroscopy and optical methods in solution and in the solid state. In the presence of excess metal, a new trinuclear complex was identified. The X-ray crystal structure elucidated the coordination of metallic cations with two ligands of different conformations. By varying the metal/ligand ratio, a global speciation of this supramolecular system has been evidenced with different spectroscopic methods. In addition, these rather complicated equilibria were successfully characterised with the thermodynamic stability constants. A rational analysis of the self-assembly processes was attempted by using the thermodynamic free energy model and the impact of the ligand structure on the effective concentration is discussed.     

4,5-diazafluorene-based overcrowded alkene: a new ligand for transition metal complexes

[structure: see text] A new ligand system, where a 4,5-diazafluorene-type chelate and a methoxybenzoxanthene unit are coupled by a double bond has been synthesized and fully characterized including X-ray structure. The synthesis and UV-vis spectra of Ru(II), Os(II), and Re(I) complexes with the above-mentioned ligand are also shown.     

Homo- and heteronuclear complexes of a new,vicinal dioxime ligand

A new symmetrical vicinal dioxime, N,N′-bis-{4-[[(2-hydroxyphenyl)methylene]hydrazinecarbonyl]phenyl}diaminoglyoxime (LH₄), was prepared by reacting anti-dichloroglyoxime with salicylaldehyde 4-aminobenzoylhydrazone. The reaction of ligand with Ni²⁺ salts gave mono-and homopentanuclear complexes, [Ni(LH₃)₂] and [Ni₅(LH)₂X₂]. Furthermore, heteropentanuclear complexes of dioxime ligand, [Cu₄Ni(LH)₂X₄], were prepared by the reaction of [Ni(LH₃)₂)] with Cu²⁺ salt and a monodentate ligand (X = SCN⁻, CN⁻, or N ₃ ⁻ ). The structures of both the new symmetrical vicinal dioxime and its complexes were identified by elemental analyses, IR, ¹H NMR, UV-VIS spectra, and magnetic susceptibility. The elemental analyses and spectral data indicate that the hydrazone side of ligand acts as a O,N,O′ tridentate and the fourth position is occupied with monodentate anion such as SCN⁻, CN⁻, N ₃ ⁻ .     

Latrunculins: NMR study,two new toxins and a synthetic approach

A complete ¹H and ¹³C NMR assignment of one of the latrunculins (B) was accomplished with the aid of 2D NMR COSY and CH shift-correlation experiments. The various H-H Coupling constants have been datermined and a conformation of the macrolide and the tetrahydropyran (THP) ring suggested on basis of the J-values and measured NOE's. The absolute configuration of latrunculin-A($\text{1}$) was determined on the grounds of its earlier X-Ray analysis, and a chemical degradation to a known compound. Two novel latrunculins, -C($\text{3}$) and -D($\text{4}$), were isolated from the Red Sea sponge $\text{L. magnifica}$ and their structures elucidated. Starting with L-cysteine a synthon for the latrunculins has been synthesized.     

N-Biphenyl thioureas as carboxylate receptors. Effect of the ligand substituents on the geometry of the complexes

Six new biphenyl thiourea derivatives have been prepared to be used in carboxylate sensing. Experiments carried out with these ligands have demonstrated that the type of interaction with TBA carboxylates is strongly dependent on the substituents in the thiourea moiety. These interactions go from the formation of 1:1 hydrogen-bonded complexes to acid-base reactions. In addition, different geometries have been observed for the complexes being dependent on the conformations of the free ligands in solution.     

Ruthenium-olefin complexes: effect of ligand variation upon geometry

The development of a model system to study ruthenium-olefin complexes relevant to the mechanism of olefin metathesis has been reported recently. Upon addition of the ligand precursor 1,2-divinylbenzene to [RuCl(2)(Py)(2)(H(2)IMes)(==CHPh)] (H(2)IMes=1,3-dimesityl-4,5-dihydroimidazol-2-ylidene), two ruthenium-olefin adducts are formed. Based on (1)H NMR spectroscopy experiments and X-ray crystallographic analysis, these complexes are assigned as side-bound isomers in which the olefin and H(2)IMes ligands are coordinated cis to each other. Herein is reported an investigation of the generality of these observations through variation of the N-heterocyclic carbene ligand and the ligand precursor.     

Two heterometallic complexes with a new macrocyclic oxamido complex ligand

A new macrocyclic oxamido-nickle(II) complex Na₂NiL was synthesized. L denotes the doubly deprotonated forms of (13Z, 19Z)-16-methyl-6,7-dioxo-5,6,7,8-tetrahydrotriben-zo[b,f,l][1,4,8,11]tetraazacyclotetradecine- 13,20-dicarboxylate. Based on the complex ligand Ni(L^2–), two heterometallic complexes [Ca₂(NiL)₂(H₂O)₈] · 10H₂O (I) and [Co(NiL)₂(H₂O)₂][Co(H₂O)₆] · 2.8H₂O (^II) were prepared. X-ray single crystal analyses (CCDC nos. 914618 (^I), 914616 (^II)) revealed that [Ca₂(NiL)₂(H₂O)₈] in I is a molecular box and the trinuclear complex anion [Co(NiL)₂(H₂O)₂]^2–in II is centrosymmetric. Thermogravimetric analyses showed that I exhibited moderately good stability and Co(II) catalyzed the thermal decomposition of II.     

Ru and Os complexes containing a P,N-donor heterotopic ligand: the effect of solvent on stereochemistry

Ruthenium and osmium complexes of the general formula MCl 2(PyP) 2 (where PyP is the P,N- donor ligand 1-(2-diphenylphosphinoethyl)pyrazole) were synthesized from MCl 2(PPh 3) 3 (where M = Ru or Os). Three of the five possible stereoisomers of RuCl 2(PyP) 2 were synthesized and characterized in solution by multinuclear NMR spectroscopy, and the structure of these in the solid state was determined by X-ray crystallography. Two of the analogous Os isomers were also synthesized. It was found that different solvents induced isomerization between these stereoisomers, indicating either lability of the chloride anion or hemilability of the PyP ligand. Bimetallic complexes of the general formula [Ru(mu-Cl)(PyP) 2] 2[X] 2 were synthesized from chloride abstraction from RuCl 2(PyP) 2 using either silver (X = OSO 2CF 3, BF 4) or sodium (X = BPh 4) salts. The osmium analogue of the Ru bimetallic complexes, [Os(mu-Cl)(PyP) 2] 2[BPh 4] 2, was also synthesized. Solid-state structures were obtained using X-ray crystallography for the osmium bimetallic complex and the ruthenium bimetallic complex where X = OSO 2CF 3. The hemilability of PyP was demonstrated through the synthesis of RuCl 2(CO)(kappa (1)- P-PyP)(kappa (2)- P, N-PyP), which contains one pendant PyP ligand, bound through the P-donor atom.     

Synthesis, crystal structures, luminescent and magnetic properties of homodinuclear lanthanide complexes with a flexible tripodal carboxylate ligand

Six new homodinuclear lanthanide(III) complexes with a flexible tripodal carboxylate ligand (H(3)L), of formulae [Ln(2)L(2)(DMF)(4)]·4DMF (Ln = La (1), Nd (2), Eu (3), Gd (4), Tb (5), Dy (6), DMF = N, N-Dimethylformamide) have been synthesized. Among them, 1, 2, 3, 4, 6 were characterized by single-crystal X-ray diffraction, which crystallized in the monoclinic space group P2(1)/n with a = 13.309(2) ?, b = 27.404(4) ?, c = 16.686(3) ?, β = 105.115(2) and V = 5875.2(17) ?(3) for 1, a = 13.3016(5) ?, b = 27.1952(12) ?, c = 16.6339(7) ?, β = 105.030(2) and V = 5811.3(4) ?(3) for 2, a = 13.2797(10) ?, b = 27.072(2) ?, c = 16.6564(13) ?, β = 104.9390(10) and V = 5785.7(8) ?(3) for 3, a = 13.2855(3) ?, b = 27.0074(6) ?, c = 16.6357(3) ?, β = 104.9790(10) and V = 5766.2(2) ?(3) for 4, a = 13.2837(5) ?, b = 26.9105(10) ?, c = 16.6066(6) ?, β = 104.917(2) and V = 5736.3(4) ?(3) for 6. The crystal structures reveal that these complexes are isostructural, and molecules are connected from 0D to 3D supramolecular structures by hydrogen bonds. All of them were characterized by elemental analysis, IR spectroscopy, XRD and TGA. Unusually, non-luminescent Tb(III) complex was obtained. The photophysical property of the Eu(III) complex and the magnetic property of Gd(III) complex are investigated and discussed in detail.     

A modular synthetic approach toward exhaustively stereodiversified ligand libraries

[structure] This report describes a modular approach to the synthesis of stereodiversified natural product-like libraries. Monomers 2 and 3 were coupled in parallel by silyl-tethered olefin metathesis to generate all 16 stereoisomers of cis-enediols 1. All 16 stereoisomers were incorporated into chimerae having flanking peptidic segments. These chimerae exhibited a broad range of hydrophobicities, raising the possibility that stereochemical variation might be used to tune the pharmacologic properties of small molecules.