E4 Butterfly Complexes (E=P,As) as Chelating Ligands

The coordination properties of new types of bidentate phosphane and arsane ligands with a narrow bite angle are reported. The reactions of [{Cp′′′Fe(CO)₂}₂(μ,η^1:1‐P₄)] ( 1 a ) with the copper salt [Cu(CH₃CN)₄][BF₄] leads, depending on the stoichiometry, to the formation of the spiro compound [{{Cp′′′Fe(CO)₂}₂(μ₃,η^1:1:1:1‐P₄)}₂Cu]⁺[BF₄]^? ( 2 ) or the monoadduct [{Cp′′′Fe(CO)₂}₂(μ₃,η^1:1:2‐P₄){Cu(MeCN)}]⁺[BF₄]^? ( 3 ). Similarly, the arsane ligand [{Cp′′′Fe(CO)₂}₂(μ,η^1:1‐As₄)] ( 1 b ) reacts with [Cu(CH₃CN)₄][BF₄] to give [{{Cp′′′Fe(CO)₂}₂(μ₃,η^1:1:1:1‐As₄)}₂Cu]⁺[BF₄]^? ( 5 ). Protonation of 1 a occurs at the “wing tip” phosphorus atoms, which is in line with the results of DFT calculations. The compounds are characterized by spectroscopic methods (heteronuclear NMR spectroscopy and IR spectrometry) and by single‐crystal X‐ray diffraction studies.     

Dinuclear gold(I) Complexes with Bidentate NHC Ligands as Precursors for Alkynyl Complexes via Mechanochemistry

The use of alkynyl gold(I) complexes covers different research fields, such as bioinorganic chemistry, catalysis, and material science, considering the luminescent properties of the complexes. Regarding this last application, we report here the synthesis of three novel dinuclear gold(I) complexes of the general formula [(diNHC)(Au-C≡CPh)₂]: two Au-C≡CPh units are connected by a bridging di(N-heterocyclic carbene) ligand, which should favor the establishment of semi-supported aurophilic interactions. The complexes can be easily synthesized through mechanochemistry upon reacting the pristine dibromido complexes [(diNHC)(AuBr)₂] with phenylacetylene and KOH. Interestingly, we were also able to isolate the monosubstituted complex [(diNHC)(Au-C≡CPh)(AuBr)]. The gold(I) species were fully characterized by multinuclear NMR spectroscopy and mass spectrometry. The emission properties were also evaluated, and the salient data are comparable to those of analogous compounds reported in the literature.     

Effects on Coordination of Thioether Sites. 4. Structural Analysis of η3-Tripodal Ligand Manganese(I) Complexes

Crystal structures of a series of manganese(I) complexes containing tripodal ligands were determined. For [η³-{CH₃C(CH₂PPh₂)₂(CH₂SPh)-P,P′,S}Mn(CO)₃]PF₆ ( 1 ): a = 10.856(3) Å, b = 19.698(3) Å, c = 17.596(5) Å, β = 96.17(2)°, monoclinic, Z = 4, P2₁/c, R(F_o) = 0.068, R_w(F_o) = 0.055 for 3617 reflections with I_o > 2σ(I_o). For [η³-{CH₃C(CH₂PPh₂)(CH₂SPh)₂-P,P′,S}Mn(CO)₃]PF₆ ( 2 ): a = 9.890(2) Å, b = 20.403(4) Å, c = 10.269(3) Å, β = 117.44(2)°, monoclinic, Z = 2, P2_l, R(F_o) = 0.050, R_w(F_o) = 0.037 for 1760 reflections with I_o > 2σ(I_o). For [η³-{CH₃C(CH₂PPh₂)₂(CH₂S)-P,P′,S}Mn(CO)₃] ( 4 ): a = 8.191(7) Å, b = 10.495(3) Å, c = 19.858(6) Å, α = 99.61(2)°, β = 96.17(2)°, γ = 92.70(4)°, triclinic, Z = 2, P-I, R(F_o) = 0.048, R_w(F_o) = 0.039 for 2973 reflections with I_o > 2σ(I_o). There is no significant difference in the bond lengths of Mn-S bonds among three species in their crystal structures [2.325(2) Å in 1; 2.358(4) in 2; 2.380(2) in 4], but the better donating ability of thiolate in complex 4 appears on the lower frequencies of its carbonyl stretching absorptions.     

Electrochemistry Inside Microdroplets of Kerosene: Electroanalysis of (Methylcyclopentadienyl) Manganese(I) Tricarbonyl(I)

A novel electrochemical technique for the determination of (methycyclopentadienyl) manganese(I) tricarbonyl in kerosene is presented. The protocol involves creating an ensemble of microdroplets via spraying a fine mist of the sample under investigation onto an electrode substrate which is then immersed into an immiscible supported phase of either water or acetonitrile which can be used to voltammetrically interrogate the species of interest. In particular the kerosene|acetonitrile interface allows the study of the electrochemical oxidation of (methycyclopentadienyl) manganese(I) tricarbonyl, MMT which normally occurs at large overpotentials (E_1/2=+1.22 V vs. saturated calomel electrode).     

Synthesis and Crystal Structures of Manganese(II) and ­Cobalt(II) Complexes with 2, 6‐Dimethoxybenzoic Acid and Additional N‐Donor Ligands

Three coordination compounds [Mn₃(dmb)₆(H₂O)₄(4, 4′‐bpy)₃(EtOH)]_n ( 1 ) and [M(dmb)₂(pyz)₂ (H₂O)₂] [M^II = Co ( 2 ), Mn ( 3 )] (Hdmb = 2, 6‐dimethoxybenzoic acid, 4, 4′‐bpy = 4, 4′‐bipyridine, pyz = pyrazine) were synthesized and characterized by single‐crystal X‐ray diffraction analysis. Compound 1 consists of infinite 1D polymeric chains, in which the metal entities are bridged by 4, 4′‐bpy ligands. There are four crystallographically independent Mn^II atoms in the linear chain with different coordination modes, which is only scarcely reported for linear polymers. The isostructural crystals of 2 and 3 are composed of neutral mononuclear complexes. In crystal the complexes are combined into chains by intermolecular O–H ··· N hydrogen bonds and π–π interactions between antiparallel pyrazine molecules.     

A one pot multi-component CuAAC “click” approach to bidentate and tridentate pyridyl-1,2,3-triazole ligands: Synthesis,X-ray structures and copper(II) and silver(I) complexes

A one pot, multi-component CuAAC reaction has been developed for the generation of alkyl, benzyl or aryl substituted bi and tridentate pyridyl-1,2,3-triazole ligands from their corresponding halides, sodium azide and alkynes in excellent yields. The ligands have been fully characterized by elemental analysis, HR-ESMS, IR, ¹H and ¹³C NMR and in the ferrocenyl substituted cases the structures were confirmed by X-ray crystallography. Additionally, we have examined the coordination chemistry of these ligands and found that a variety of geometrically diverse Cu(II) and Ag(I) complexes, including interesting tri and tetrasilver complexes, can be formed.     

Tricarbonyl Complexes of Rhenium(I) with Acetylpyridine Benzoylhydrazone and Related Ligands

Novel rhenium(I) tricarbonyl complexes have been prepared by reactions of (Et₄N)₂[Re(CO)₃Br₃] with acetylpyridine benzoylhydrazone, Hapbhyd, di(2‐pyridyl)ketone benzoylhydrazone, Hpy₂bhyd, bis(2‐pyridine)ketone, py₂CO, and pyridinealdehyde terephtalaldehydebishydrazone, pytehyd. The ligands remain protonated when no supporting base is added and the following complexes have been isolated: [Re(CO)₃Br(Hapbhyd)], [Re(CO)₃Br(Hpy₂bhyd‐py, hyd)], [Re(CO)₃Br(Hpy₂bhyd‐py¹, py²)], [Re(CO)₃Br(py₂CO‐N, N)] and [Re(CO)₃Br(pytehyd)]. Addition of triethyl amine results in deprotonation of Hapbhyd and the formation of [Re(CO)₃(OH₂)(apbhyd)], whereas Hpy₂bhyd is hydrolysed and a rhenium complex with the monoanionic bis(2‐pyridyl)hydroxymethanolato ligand, {py₂C(OH)O}^‐, is formed. The same compound, [Re(CO)₃{py₂C(OH)O}], is obtained when triethyl amine and water are added to a mixture of (Et₄N)₂[Re(CO)₃Br₃] and py₂CO. The air‐stable products have been studied by spectroscopic methods and X‐ray crystallography.     

On the Reaction of [(CO)3Fe(μ‐Me2NCO)2Fe(CO)2(NHMe2)] with Chelating Ligands — X‐Ray Structures of New Binuclear μ‐Carbamoyl Complexes

Reaction of the binuclear μ‐carbamoyl complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(HNMe₂)] ( 1 ) in toluene with the chelating ligands Ph₂PCH₂PPh₂ (dppm) and Ph₂PCH₂CH₂PPh₂ (dppe) gives different results. With dppm only the complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(dppm)] ( 3 ) with a dangling ligand is obtained under replacement of amine, whereas with dppe depending on the reaction conditions up to three compounds are found. A 1 : 1 mixture of the educts generates the related complex [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂(dppe)] ( 4 ) together with the tetranuclear complex [{(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)₂}₂(dppe)] (5 ). 4 slowly converts into [(CO)₃Fe(μ‐Me₂NCO)₂Fe(CO)(dppe)] ( 6 ) with dppe acting as a chelating ligand. 6 is the first compound in this series in which one of the five CO groups is replaced by another donor. A 2 : 1 molar ratio of 1 and dppe quantitatively produces 5 . Addition of CO to a solution of 6 proceeds under slow reversible conversion of the complex into 4 . The compounds were characterized by the usual spectroscopic methods; 3 , 5 and 6 were also studied by X‐ray diffraction analyses.     

Synthesis and Characterization of Di‐ and Tricarbonylhydridomanganese(I) Complexes

Hydrido complexes [MnH(CO)₃L^1–3] [L¹ = 1,2‐bis‐(diphenylphosphanoxy)‐ethane ( 1 ); L² = 1,2‐bis‐(diisopropylphosphanoxy)ethane ( 2 ); L³ = 1,3‐bis‐(diphenylphosphanoxy)‐propane ( 3 )] were prepared by treating [MnH(CO)₅] with the appropriate bidentate ligand by heating to reflux. Photoirradiation of a toluene solution of complexes 1 and 2 in the presence of PPh_n(OR)_3–n (n = 0, 1; R = Me, Et) leads to the replacement of a CO ligand by the corresponding monodentate phosphite or phosphonite ligand to give new hydrido compounds of formula [MnH(CO)₂(L^1–2)(L)] [L = P(OMe)₃ ( 1a – 2a ); P(OEt)₃ ( 1b – 2b ); PPh(OMe)₂ ( 1c – 2c ); PPh(OEt)₂ ( 1d – 2d )]. All complexes were characterized by IR, ¹H, ¹³C and ³¹P NMR spectroscopy. In case of compounds 2 and 3 , suitable crystals for X‐ray diffraction studies were isolated.     

Trifluoromethylated 3-(Pyrazol-1-yl)propanamide (PPA) Ligands

The new PPA ligands 3-[5-methyl-3-(trifluoromethyl)-1H-pyrazol-1-yl]propanamide (CF₃MePPA; 3 ) and 3-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]propanamide ((CF₃)₂PPA; 4 ) were synthesized by Aza-Michael addition of the specific pyrazole derivatives to acrylamide. Both products were characterized by elemental analyses, IR and NMR spectroscopy, and mass spectrometry. X-Ray structure determination of 3 revealed the presence of a one-dimensional hydrogen-bonded structure in the solid state. The ligating ability of the new ligands towards PdCl₂ was studied, showing that 3 behaves similar to Me₂PPA and reacts cleanly with PdCl₂ to afford the sparingly soluble complex PdCl₂(CF₃MePPA-κN)₂. By contrast, the donor ability of pyrazolyl group in 4 was found to be considerably reduced, thus resulting in the formation of the unusual complex PdCl₂{(CF₃)₂PPA-κN}{(CF₃)₂PPA-κO}.     

Chelating Ligands Tethered to Carbon Nanotubes

Summary: Carbon nanotubes offer an inert platform on which various species may be supported. A range of applications have been addressed using this approach. Anchoring sites on the nanotubes are usually groups introduced via an oxidative procedure. These groups provide convenient reactive functionality that can be accessed in a variety of ways. In this case, carboxyl functionality have been utilized to attach, through a linker, a good coordinating ligands, 1-10-phenanthroline. In the first instance, 1,10-phenanthroline was converted to the 5,6-epoxide by treatment with hypochlorite. The epoxide was opened in sulfuric acid to generate the 5-hydroxy compound. This, in turn, was treated with ethylene oxide in the presence of a base to provide the alkoxylated compound. The alcohol terminus, as the alkoxide, was used to couple the nanotubes by displacement of tosyl anion from the methylol ester. The carboxyl groups at the nanotubes surface were reduced to the corresponding alcohol and treated with p-toluenesulfonyl chloride in the presence of pyridine to generate the tosylate used for coupling. In a second approach the carboxyl groups were converted to the corresponding acid chloride which was treated with alkoxylated phenanthroline to achieve coupling via an ester linkage.     

Rapid Determination of Methylcyclopentadienyl Manganese Tricarbonyl in Gasoline by FAAS

ABSTRACT

A new method using microemulsified samples is presented. The method is suitable for the determination of manganese, present as methylcyclopentadienyl manganese tricarbonyl, in gasoline in the range 0～75μg ml^?1. The method has the advantage of simplicity, speed and the use of aqeous standards for calibration instead of organic standards. Coexistent elements do not disturb the determination. Results obtained by this method were better than those obtained by other methods for the same samples.     

Dibromomanganese(II) complexes with hexamethylphosphoramide and phenylphosphonic bis(diamide) ligands

Tetrahedral dibromomanganese(II) complexes having formulas [MnBr₂{O?=?PR(NMe₂)₂}₂] (R?=?NMe₂ (1); Ph (2)) were isolated and characterized by single crystal X-ray diffraction. [MnBr₂{O?=?P(NMe₂)₃}₂] (1) crystallizes in the monoclinic C2/c space group. The asymmetric unit contains one half of the molecule with the Mn(II) atom in a distorted tetrahedral coordination. The intermolecular network of this coordination compound was studied by generating and inspecting its Hirshfeld surface, while the weak intramolecular hydrogen bonds were investigated computationally by AIM analysis in the gas phase and in solution. The Hirshfeld analysis was extended to the related [MnBr₂{O?=?PPh(NMe₂)₂}₂] complex (2).     

Hydride and dihydrogen dicarbonylrhenium(I) complexes with phosphites, phosphonites and phosphinites

Photoirradiation of a toluene solution of [ReH(CO)₃(L)] [S. Bolaño, J. Bravo, R. Carballo, S. García-Fontán, U. Abram, E.M. Vázquez-López, Polyhedron 18 (1999) 1431-1436] [L = 1,2-bis(diphenylphosphinoxy)ethane] in the presence of PPh_n(OR)_3−n (n = 0, 1; R = Me, Et) leads to the replacement of a CO ligand by the corresponding monodentate phosphite or phosphonite ligand to give new hydride compounds of formula [ReH(CO)₂(L)(L′)] [L′ = P(OMe)₃ (1); P(OEt)₃ (2); PPh(OMe)₂ (3); PPh(OEt)₂ (4)]. Protonation of compounds 1-4 in CD₂Cl₂, with HBF₄.OMe₂ or with HOOCCF₃ at 193 K in a NMR tube, gave the corresponding dihydrogen complexes. When the temperature was increased from 193 to 293 K, the η²-H₂ ligand was replaced by OMe₂ or ⁻OOCCF₃ groups (depending on the acid employed) to give new stable complexes and the loss of H₂ gas.     

Synthesis,Structure, and Properties of Iron(II) and Manganese(II) Bis[Tris(1‐Ethyl‐4‐Methylimidazolyl‐κN)Phosphine] Complexes

Fe^IIL₂(OTf)₂ ( 1 ) and Mn^IIL₂(OTf)₂ ( 2 ) (L = tris(1‐ethyl‐4‐methylimidazolyl‐κN)phosphine; OTf= trifluoromethanesulfonate) were synthesized and their X‐ray structures were determined. Both complexes possess distorted octahedral geometry with high spin electron configuration at ambient temperature. Compound 1 exhibits a quasi‐reversible wave with E_1/2 of 0.745 V versus Ag/AgNO₃. Variable temperature magnetic measurements indicate that no spin‐crossover phenomenon for 1 is observed between 2.5 and 300 K. In addition, a plot of 1/χ_M versus T(K) is linear with a Curie constant of 3.48 emu mol^?1 K.     

Molybdenum Tricarbonyl Complexes Supported by Linear PNP Ligands: Influence of P- and N-Substituents on Relative Stability,Stereoisomerism and on the Activation of Small Molecules

Series of linear tridentate PN^PhP^R-ligands (R=Me, Et, Pln, Ph, Cyp, ⁱPr, Cy, ^tBu) and molybdenum tricarbonyl complexes [Mo(CO)₃PN^PhP^R] (R=Ph, Et, Cyp, ⁱPr, Cy,) were synthesized and characterized using NMR-, IR-, and Raman spectroscopy as well as X-ray crystallography. The influence of the different phosphine donor groups of the PN^PhP^R ligands on the bonding and activation of CO ligands is investigated. Importantly, all complexes are found to adopt a fac geometry, both in solution and in the solid state. This is in contrast to analogous complexes supported by PN^HP ligands. DFT calculations reveal that the phenyl ring at the central amine function is the cause of the preferred geometry, hindering isomerization to a mer geometry.