Coordination of a Schiff base as an iminium-phenone zwitterion in a double ligand-bridged fac-[Re(CO)3]+ dimer

The ligand-bridged dimers [Re(CO)₃(μ-H₂salet)]₂ (1) and [{Re(CO)₃}₂(μ-salpd)] (2) are formed by the reactions of [Re(CO)₅Cl] with the potentially heptadentate Schiff base 2,2′,2″-tris(salicylideneimino)triethylamine (H₃salet) and the hexadentate N¹-(3-(2-hydroxybenzylidene-amino)propylamino)ethyl)-benzylidenepropane-1,3-diamine (H₂salpd) respectively. In 1, the two H₂salet ligands bridge two fac-[Re(CO)₃]⁺ moieties. Mono-dentate coordination is by a neutral phenone oxygen atom, generated by the conversion of one salicylideneimine entity to an iminium zwitter-ion. In 2 each fac-[Re(CO)₃]⁺ core resides in a ‘3 + 0’ environment. In both complexes π–π interaction between the phenolate rings contribute to the stability. The crystal structures of 1 and 2 were determined by X-ray single crystal diffraction. Spectroscopic results are also reported.     

A triheterometallic cluster: synthesis and structural characterisation of a cyclopentadienyl-substituted pentanuclear cluster based on an Os3CoRu metal core

The ionic coupling of the carbonyl cluster anion [Os₃Co(CO)₁₃]⁻ (1) with [Ru(η⁵-C₅H₅)(NCMe)₃]⁺ affords the new pentanuclear triheterometallic cluster Os₃CoRu(CO)₁₃(η⁵-C₅H₅) (2) as well as the known bimetallic cluster compounds HOs₃Ru(CO)₁₁(η⁵-C₅H₅) and Os₃Ru₂(CO)₁₁(η⁵-C₅H₅)₂. The crystal structure of cluster 2 shows that the metal framework is based on a trigonal bipyramid (approximate C_s symmetry) with the Ru, Co and an Os atom occupying the equatorial metal plane.     

The first iodine induced halide abstraction reaction: synthesis and molecular structure of fac-[Re(CO)3(NCMe)3]·BrI2

Equimolar quantities of [ReBr(CO)₅] and I₂ react in refluxing acetonitrile for 5 h to give the cationic tris(acetonitrile) complex fac-[Re(CO)₃(NCMe)₃]·BrI₂ (1) in a quantitative yield, via the first iodine promoted halide abstraction reaction. The structure of 1 has, as expected, a facial arrangement of carbonyl and acetonitrile ligands, with the linear anion, BrI₂ as the counter ion.     

Tetrameric rhenium complexes with a glycine-thiourea derivative

[ReNCl₂(PPhMe₂)₃] reacts with the glycine ethylester derivative Et₂NC(S)NC(Ph)NHCH₂COOEt, HL(GlyEt), in methanol under hydrolysis of the ester and formation of the tetrameric, nitrido-bridged rhenium(V) compound [{ReN{fac-L(Gly)}(PMe₂Ph)}{ReN{mer-L(Gly)}(H₂O)}]₂. Both facial and meridional coordination has been found for the tridentate {L(Gly)}^2? ligand in the building blocks of the tetramer. Syn and anti isomers with respect to the PPhMe₂ ligands have been isolated and characterized by X-ray diffraction.     

A very labile monomeric 1,5-cyclooctadiene complex of W(II) and its transformation to dimeric [(μ-Cl)2W2(GeCl3)2(CO)6(NCMe)2]

The photochemical oxidative addition of 1 equiv. of GeCl₄ to [W(CO)₄(η²,η²-1,5-C₈H₁₂)] affords the very labile seven-coordinate complex of tungsten(II) [WCl(GeCl₃)(CO)₃(η²,η²-1,5-C₈H₁₂)] (1). The structure of compound 1 has been established by IR and ¹H NMR spectroscopic methods. A very labile 1,5-cyclooctadiene ligand of 1 in dichloromethane/acetonitrile solution leaves the coordination sphere of tungsten to give a dimeric seven-coordinate compound of tungsten(II) [(μ-Cl)₂W₂(GeCl₃)₂(CO)₆(NCMe)₂] (2). The crystal structure of a new dimeric compound containing W–Ge bonds (2) was determined by X-ray diffraction studies.     

Two novel three-dimensional coordination polymers with [Ag(CN)2]− as bridging ligands: synthesis and structural characterization of {KMn[Ag(CN)2]3(H2O) }n and {Mn[Ag(CN)2]2(bpy)2}n (bpy=4,4′-bipyridine)

Two novel three-dimensional coordination polymers {KMn[Ag(CN)₂]₃(H₂O)}_n 1 and {Mn[Ag(CN)₂(bpy)]₂}_n 2 have been prepared and structurally as well as magnetically characterized. In both compounds, the three-dimensional networks are constructed entirely by coordinative linkages with all the CN⁻ anions of [Ag(CN)₂]⁻, bpy and water ligands involved in bridging and the novel 3-D structure of 1 is unprecedented.     

Two Mn(II)–Au(I) supramolecular assemblies bonded by coordination,aurophilicity and hydrogen-bonding, π–π interactions and their magnetic properties

Two Mn(II)–Au(I) supramolecular assemblies {{Mn[Au(CN)₂]₂(H₂O)₄} [Au(CN)₂]₂(H₂bpy) · H₂O}(bpy = 4,4′-bipyridine) 1 and {Mn(4,4′-dmbpy) [Au(CN)₂]₂(CH₃OH)} (4,4′-dmbpy = 4,4′-dimethyl-bipyridine) 2 have been synthesized and magnetic properties have been investigated The interplay of aurophilicity, coordination, hydrogen-bonding and π–π interactions in two complexes result in three-dimensional network.     

Mono- and dinuclear rhenium(I) compounds with bidentate benzimidazole chelators

A mononuclear rhenium(I) complex, fac-[Re(CO)₃(bzch)Cl] (1), where bzch = 2-benzimidazole-4H-chromen-4-one, was isolated from the equimolar reaction between the Schiff base ligand 2-(2-aminophenyliminomethyl)-4H-chromen-4-one (H₂pch) and [Re(CO)₅Cl]. The 1:2 molar ratio reactions between [Re(CO)₅Cl] and N-(2-hydroxybenzylidene)-benzimidazole (Hbzp) afforded a dinuclear rhenium(I) compound, (μ-bzp)₂[Re(CO)₃]₂ (2). These new rhenium(I) compounds were characterized by NMR, UV–vis, IR, and emission spectroscopy, as well as conductance measurements and single crystal X-ray diffraction. The emission spectra for 1 in dichloromethane were well-resolved and could be deconvoluted into three main bands. The emission spectra for 2 were red-shifted by > 140 nm and markedly broadened relative to those of 1.     

Use of semi-rigid polyyne ligands to direct the shapes of metal clusters. The reaction of Pt2Ru4(CO)18 with o-bis(phenylethynyl) benzene

The reaction of Pt₂Ru₄(CO)₁₈ (1) with o-bis(phenylethynyl)benzene (2) has yielded the product Pt₂Ru₄(CO)₁₄[μ₅-C₆H₄(C₂Ph₂)₂] (3) which exhibits an unexpected ‘raft’ structure for the six metal atoms. Both alkyne groups are coordinated to the same side of the cluster as triple bridges across neighboring PtRu₂ triangles. Compound 3 has two valence electrons less than the 90 electron configuration usually observed for raft clusters.     

Synthesis and structural characterization of isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarboranes stabilized by the agostic bonding interaction

The [7-Me₃N-nido-7-CB₁₀H₁₂] (1), after being treated with two molar equiv. of Proton Sponge, reacts with [(η⁴-C₁₀H₁₂)₂Rh₂(μ-Cl)₂] (2) in benzene–ethanol solution affording two isomeric monocarbon (η-dicyclopentenyl)-closo-rhodacarborane complexes, differing in hapticity of the carbocyclic ligand, viz. [2,2-{(2′,3′-η²):(5′-η¹)-C₁₀H₁₃}-1-(Me₃N)-2,1-closo-RhCB₁₀H₁₀] (3) and [2-{(1′-3′-η³)-C₁₀H₁₃}-1-(Me₃N)-2,1-closo-RhCB₁₀H₁₀] (4). Isomeric compounds 3 and 4 were characterized by analytical, multinuclear NMR spectroscopic data as well as by single-crystal X-ray diffraction study, which revealed the existence of an agostic C–H⋯Rh interaction in both the species.     

Synthesis,structure and stability of fac-[FeII(CO)3X3]1− (X = Br,I)

fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are synthesized and their structures have been determined. They are the first crystallographically characterized iron tricarbonyl trihalide complexes. fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are fairly thermally stable and therefore lead themselves as excellent starting materials for the preparation of various iron carbonyl complexes since both the halide and carbonyl ligands are substitutionally labile.     

Study of the cytotoxic activity of alkenyl-substituted ansa-titanocene complexes

The cytotoxic activity on tumour cell lines, human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x and normal immunocompetent cells, was tested for four different ansa-titanocene dichloride derivatives with potentially reactive substituents [Ti{Me(CH₂CH)Si(η⁵-₅Me₄) (η⁵-C₅H₄)}Cl₂] (1), [Ti{Me(H)Si(η⁵-C₅Me₄)₂}Cl₂] (2), [Ti{Me{(CH₂CH)Me₂SiCH₂CH₂}Si(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (3) and [Ti{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃(CMe₂(CH₂CH₂CHCH₂)))}Cl₂] (4), showing a very promising activity and opening up the possibility of extensive investigation in this field.     

Two distinct ferroceneyl carboxylate Pb(II) complexes with the same composition prepared by two different synthetic methods: The substitution of precursor and one-pot reaction

Through substituation reaction, one lead ferroceneyl carboxylate polymer, namely [Pb(μ₂-OOCClH₃C₆Fc)₂(phen)]_n 1a [Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄)] was synthesized from precursor [Pb(μ₂-η²-OOCClH₃C₆Fc)₂(CH₃OH)₂]_n 1. However, a mononuclear Pb(II) complex {[Pb(η²-OOCClH₃C₆Fc)₂(phen)]·(CH₃OH)·(H₂O)} 2 could be obtained from the traditional one-pot reaction of FcC₆H₃ClCOONa and Pb(OAc)₂ with 1,10-phenantholine (phen). The electrochemical studies of 1, 1a, 2 and FcC₆H₃ClCOOH indicate that the half-wave potentials of the ferrocenyl moieties in these complexes are all shifted to positive potential compared with that of FcC₆H₃ClCOOH.     

A rhenium(I) compound bearing a dimerized chromone NO bidentate chelator

Herein, we communicate the synthesis of a novel rhenium(I) complex, fac-[Re(CO)₃(chrpychr)Br] (1) from the equimolar reaction between 2-(4-oxo-4H-chromen-3-yl)-5H-chromeno[2,3-d]pyrimidin-5-one (chrpychr) and [Re(CO)₅Br]. The metal complex 1 was characterized via ¹H NMR-, IR- and UV–Vis spectroscopy and conductivity measurements. Single crystal X-ray analysis provides definitive confirmation in the structural elucidation of 1. DFT studies of 1 aided in the interpretation of its experimental IR spectrum.     

Coordination assemblies of CdII/ZnII/CoII with the 3-(pyridin-4-yl) benzoate tecton: Structural diversity and properties

Three novel coordination polymers{[CdL₂(HL)(H₂O)]·(H₂O)}_n (1), [Zn₂(OH)L₃]_n (2) and [CoL₂(H₂O)]_n (3) have been hydrothermally synthesized from M(NO₃)₂·nH₂O (M^II = Cd^II, Zn^II and Co^II) and an unsymmetrical tecton 3-(pyridin-4-yl) benzoic acid (HL). All complexes show interesting structural patterns, namely, unprecedented 1D double-stranded supramolecular clasp for 1, novel (3,5,6)-connected helical tubular double layer for 2, 2-fold interpenetrating cds network for 3. The fluorescent and thermal properties of complexes 1, 2 and/or 3 have also been investigated.     

A novel dianionic seven-coordinate complex of tungsten(II), [WCl3(GeCl3)(CO)3]2−: Synthesis,spectroscopic properties and X-ray crystal structure

A new dianionic complex of tungsten(II), [(WCl₃(GeCl₃)(CO)₃]²⁻ (1²⁻), containing the piperidinium cations [Hpip]⁺ as the counter ions, has been obtained from the reaction between [W(CO)₄(pip)₂] and GeCl₄ in dichloromethane solution, and its molecular structure has been elucidated by single-crystal X-ray diffraction studies. The chemical properties of complex 1 were investigated by IR and NMR spectroscopy in solution.     

Supramolecular Polymers and Chiral Phosphine Oxides by Oxidation of Gold(I) Complexes

The chiral diphosphine ligand R,R-cyclo-C₆H₁₀-trans-1,2-{NHC(=O)C₆H₄-2-PPh₂}₂, 1, forms complexes with gold(I) of formula [Au(1)]Cl, 2, and [(ClAu)₂(µ-1)], 3, in which the diphosphine acts as a trans-chelate and bridging ligand, respectively. Oxidation of these gold(I) complexes leads to dissociation and oxidation of the diphosphine ligand to form the corresponding diphosphine dioxide R,R-cyclo-C₆H₁₀-1,2-{NHC(=O)C₆H₄-2-P(=O)Ph₂}₂, which has been crystallized in its protonated form and as complexes with Na⁺ and Fe²⁺, with [AuBr₂]^? or [AuBr₄]^? anions. Some of these compounds form supramolecular polymers by intermolecular hydrogen bonding.     

Tricarbonyl rhenium complex of 2,6-bis(8′-quinolinyl)pyridine: Synthesis,spectroscopic characterization,X-ray structure and DFT calculations

2,6-Bis(8′-quinolinyl)pyridine (bqp) reacts with pentacarbonyl rhenium chloride in toluene to give fac,fac-[Re(bqp-κ³N)(CO)₃](Cl). X-ray crystallographic data on fac,fac-[Re(bqp-κ³N)(CO)₃](Cl) show that the bqp ligand and carbonyl ligands achieve a mutually facial arrangement. A mix of MLCT and π–π* ligand centered transitions is observed for the low energy UV–vis absorption bands. The complex is emissive in solution and appears to be dominated by a MLCT-based process. Electronic and structural characteristics are supported by DFT calculations.     

Capturing copper(II) ions using {Cu(tpy)(bpy)} domains

The reaction of 6,6"'-dimethyl-2,2':6',2":6",2'"-quaterpyridine (2) with 2,2':6',2"-terpyridine (tpy) and Cu(NO₃)^·3H₂O leads to the formation of [Cu(tpy)(2)]²⁺ and [Cu₂(tpy)₂(2)]⁴⁺, isolated as the hexafluoridophosphate salts. Single crystal structures of [Cu₂(tpy)₂(2)][PF₆]₄·2H₂O and [Cu(tpy)(2)][PF₆]₂·MeCN are presented and illustrate the special stability of the 5-coordinate {Cu(tpy)(bpy)}²⁺ motif in mono- and dinuclear environments.     

Organometallic boxes built from 5,10,15,20-tetra(4-pyridyl)porphyrin panels and hydroxyquinonato-bridged diruthenium clips

Self-assembly of 5,10,15,20-tetra(4-pyridyl)porphyrin (tpp-H₂) tetradentate panels with dinuclear arene ruthenium clips [Ru₂(η⁶-arene)₂(dhbq)Cl₂] (arene = C₆H₅Me, p-PrⁱC₆H₄Me, C₆Me₆; dhbq = 2,5-dihydroxy-1,4-benzoquinonato) affords the cationic organometallic boxes [Ru₈(η⁶-C₆H₅Me)₈(tpp-H₂)₂(dhbq)₄]⁸⁺ ([1]⁸⁺), [Ru₈(η⁶-p-PrⁱC₆H₄Me)₈(tpp-H₂)₂(dhbq)₄]⁸⁺ ([2]⁸⁺) and [Ru₈(η⁶-C₆Me₆)₈(tpp-H₂)₂(dhbq)₄]⁸⁺ ([3]⁸⁺). These octanuclear cations have been isolated as their triflate salts and characterised by mass spectrometry, NMR and IR spectroscopy. The molecular structure of these systems was deduced by one-dimensional and two-dimensional NMR experiments (ROESY, COSY, HSQC).