Acetonitrile Ligands Research Articles

Poly[(acetonitrile-κN)-μ3-thiocyanato-κ3N:S:S-μ2-thiocyanato-κ2N:S-cadmium

The asymmetric unit of the title compound, [Cd(NCS)2(CH3CN)]n, consists of one CdII cation, two thio­cyanate anions and one aceto­nitrile ligand, all in general positions. The CdII cation is coordinated by three N atoms of two thio­cyanate anions and one aceto­nitrile ligand, as well as three S atoms of symmetry-related thio­cyanate anions within a slightly distorted octa­hedral coordination environment. The CdII cations are linked by μ-1,3(N,S) and μ-1,1,3(S,S,N) thio­cyanate anions into layers that are located in the ab plane.

Juxtaposition of the strong back-bonding carbonyl ligand and weak back-bonding acetonitrile ligand in binuclear iron complexes

The binuclear iron complexes (CH3CN)2Fe2(CO) n (n = 7, 6), containing both the strongly back-bonding CO ligand and the weakly back-bonding acetonitrile ligand, have been investigated by density functional theory. The acetonitrile ligands are always found to be terminal in such structures. Heptacarbonyl structures are found at similar energies, with both acetonitrile ligands bonded to the same iron atom or with each acetonitrile ligand bonded to a different iron atom. Various combinations of bridging and semibridging CO groups are found in these (CH3CN)2Fe2(CO)7 structures approaching triply (bridged + semibridged) structures for the structures with symmetrically distributed acetonitrile ligands. The latter structures thus resemble the well-established triply bridged structure for the related binary iron carbonyl Fe2(CO)9. For the hexacarbonyl (CH3CN)2Fe2(CO)6, both triplet unbridged structures and singlet doubly bridged structures are found. The triplet (CH3CN)2Fe2(CO)6 structures have slightly lower energies relative to the singlet structures. The acetonitrile ligands in (CH3CN)2Fe2(CO) n (n = 7, 6) are always found to be terminal ligands. Various combinations of bridging and semibridging CO groups are found in these (CH3CN)2Fe2(CO)7 structures approaching triply (bridged + semibridged) structures for the structures with symmetrically distributed acetonitrile ligands. For the hexacarbonyl (CH3CN)2Fe2(CO)6, both triplet unbridged structures and singlet doubly bridged structures are found.

Tris(acetonitrile-κN)dichlorido(triphenylphosphane-κP)ruthenium(II) acetonitrile monosolvate

In the title complex, [RuCl2(CH3CN)3(C18H15P)]·CH3CN, the coordination geometry of the RuII atom is distorted octa­hedral, defined by one P atom from a tri­phenyl­phosphane ligand, three N atoms from three aceto­nitrile ligands and two Cl atoms. The three acetronitile ligands linearly bind to the RuII atom, with Ru—N—C angles of 172.6 (2), 179.9 (2) and 171.4 (2)°.

The coordination chemistry of two symmetric double-armed oxadiazole-bridged organic ligands with copper salts

Two new symmetric double-armed oxadiazole-bridged ligands, 4-methyl-{5-[5-methyl-2-(pyridin-3-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-3-carboxylate (L1) and 4-methyl-{5-[5-methyl-2-(pyridin-4-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-4-carboxylate (L2), were prepared by the reaction of 2,5-bis(2-hydroxy-5-methylphenyl)-1,3,4-oxadiazole with nicotinoyl chloride and isonicotinoyl chloride, respectively. Ligand L1 can be used as an organic clip to bind Cu(II) cations and generate a molecular complex, bis(4-methyl-{5-[5-methyl-2-(pyridin-3-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-3-carboxylate)bis(perchlorato)copper(II), [Cu(ClO4)2(C28H20N4O5)2], (I). In compound (I), the Cu(II) cation is located on an inversion centre and is hexacoordinated in a distorted octahedral geometry, with the pyridine N atoms of two L1 ligands in the equatorial positions and two weakly coordinating perchlorate counter-ions in the axial positions. The two arms of the L1 ligands bend inward and converge at the Cu(II) coordination point to give rise to a spirometallocycle. Ligand L2 binds Cu(I) cations to generate a supramolecule, diacetonitriledi-μ3-iodido-di-μ2-iodido-bis(4-methyl-{5-[5-methyl-2-(pyridin-4-ylcarbonyloxy)phenyl]-1,3,4-oxadiazol-2-yl}phenyl pyridine-4-carboxylate)tetracopper(I), [Cu4I4(CH3CN)2(C28H20N4O5)2], (II). The asymmetric unit of (II) indicates that it contains two Cu(I) atoms, one L2 ligand, one acetonitrile ligand and two iodide ligands. Both of the Cu(I) atoms are four-coordinated in an approximately tetrahedral environment. The molecule is centrosymmetric and the four I atoms and four Cu(I) atoms form a rope-ladder-type [Cu4I4] unit. Discrete units are linked into one-dimensional chains through π-π interactions.

Halido‐Bridged 1D Mixed‐Valence CuI–CuII Coordination Polymers Bearing a Piperidine‐1‐carbodithioato Ligand: Crystal Structure, Magnetic and Conductive Properties, and Application in Dye‐Sensitized Solar Cells

AbstractNew mixed‐valence CuI–CuII 1D coordination polymers of the structure [CuI2CuIIX2(Pip‐dtc)2(CH3CN)2]n [Pip‐dtc = piperidine‐1‐carbodithioate; X = Br (1a), I (1b)] containing a dithiocarbamate derivative have been synthesized and structurally characterized by X‐ray diffraction. The 1D infinite chains were formed from mononuclear copper units [Cu(Pip‐dtc)2] connected by bromido‐ or iodido‐bridged copper dinuclear units that include acetonitrile ligands {i.e., [Cu2X2(CH3CN)2]}. Evaluation of the magnetic properties of 1a and 1b revealed that these complexes displayed relatively strong antiferromagnetic interactions [J = –20.4 cm–1 (1a) and J = –18.8 cm–1 (1b)] between unpaired electrons of the copper(II) ions through the dinuclear halido–copper(I) units. Impedance spectroscopy revealed that complexes 1a and 1b exhibit intriguing semiconducting properties at activation energies of Ea = 0.78 eV (1a) and Ea = 0.62 eV (1b). Coordination polymers 1a and 1b were then adopted as the sensitizing material in dye‐sensitized solar cells (DSSCs).

Computational mechanistic study on oxidative esterification of alcohols to esters catalyzed by palladium complex

Mechanistic details of palladium-catalyzed oxidative esterification of methanol to methyl formate have been studied by density functional theory (DFT) calculations without using system simplification. A two-step mechanism involving oxidation of methanol to formaldehyde and further oxidation of formaldehyde to methyl formate and four potential reaction pathways for the later step have been proposed and fully characterized. This mechanistic study provides evidence that each oxidation step proceeds via a deprotonation followed by β-H transfer. The results indicate that methoxymethanol oxidation is the most favorable pathway kinetically and thermodynamically in the formation of methyl formate. Comparative studies on the structural and electronic properties of three Pd complexes indicate that the acetate and the acetonitrile ligands play key ligand-accelerated catalytic roles in the reactions, that is, the former acts as a nucleophilic site to facilitate the deprotonation and the latter provides a coordination site to facilitate the β-H transfer.

Synthesis and reactivity of the cyclohexadienyl ruthenium complex [(hhh5-C6H7)Ru(MeCN)3]+ with labile acetonitrile ligands

The UV irradiation of [(h5-C6H7)Ru(C6H6)]+ in MeCN gives the title complex, in which acetonitrile ligands are readily replaced by cyclopentadienide and tricarbollide anions; the structure of the tricarbollide derivative 1-(h5-C6H7)-12-ButNH-1,2,4,12-RuC3B8H10 was established by X-ray diffraction analysis.

Synthesis and characterization of acetamidine rhodium(III) cationic methyl complex, trans-[Rh(Acac)(PPh3)2(CH3){NH[dbnd]C(NH2)CH3}][BPh4], produced by ammination of acetonitrile ligand in trans-[Rh(Acac)(PPh3)2(CH3)(CH3CN)][BPh4

The rhodium(III) cationic methyl acetamidine complex, trans-[Rh(Acac)(PPh3)2(CH3){NHC(NH2)CH3}][BPh4], (1) is formed upon the reaction of trans-[Rh(Acac)(PPh3)2(CH3)(CH3CN)][BPh4] with ammonia gas in CH2Cl2 solution at temperatures between −15 °C and −20 °C. Complex 1 was characterized by elemental analysis, 31P{1H} and 1H NMR spectra, and single crystal X-ray diffraction study. The cation of 1 has a slightly distorted octahedral structure. The equatorial plane contains the acetylacetonate, methyl, and acetamidine ligands; two PPh3 ligands occupy the axial positions . The acetamidine ligand adopts the Z-configuration stabilized by hydrogen bonding with the oxygen atom of the acetylacetonate ligand, HN–H⋯O (1.90 Å). Complex 1 reacts with ammonia gas at temperatures between 0 °C and 20 °C to form cationic monophosphine complex [Rh(Acac)(PPh3)(CH3){NHC(NH2)CH3}(NH3)][BPh4] (2). Complex 2 was characterized by 31P{1H} and 1H NMR spectra without isolation.

New Cu(I)-Ethylene Complexes Based on Tridentate Imine Ligands: Synthesis and Structure

A new bulky facially coordinating N3-donor tach-based ligand (tach: cis,cis-1,3,5-triaminocyclohexane) [1: cis,cis-1,3,5-tris(2-fluoro-6-(trifluoromethyl)benzylideneamino)cyclohexane] has been obtained from the condensation of tach with 3 equiv of the appropriate benzaldehyde. Reaction of 1 with [Cu(NCMe)4][PF6] gave the complex [(1)Cu(NCMe)][PF6]. Displacement of the acetonitrile ligand is possible with CO and C2H4 (3-5 bar). Cu(I)-ethylene complexes of ligands 1 and 2 [2: cis,cis-1,3,5-(mesitylideneamino)cyclohexane] were prepared successfully by treatment of the ligands with CuBr and AgSbF6 in the presence of ethylene. These complexes display reversible complexation of the ethylene molecule under mild changes to pressure, suggesting possible application in olefin separation and extraction.

Photosensitive iron(II)-based CO-releasing molecules (CORMs) with vicinal amino and diphenylphosphino substituted chelating ligands

The reactions of [Fe(H2O)6] [BF4]2 with aminoethyl-diphenylphosphane and 2-(diphenylphosphino)aniline lead to the formation of trans-[Fe(NC-Me)2(H2NCH2CH2PPh2)2] [BF4]2 (1a) and trans-[Fe(NC-Me)2(H2NC6H4-2-PPh2)2] [BF4]2 (1b), respectively. One acetonitrile ligand can be substituted by CO yielding [Fe(CO)(NC-Me)(H2NCH2CH2PPh2)2] [BF4]2 (2a, CORM-P1) and [Fe(CO)(NC-Me)(H2NC6H4-2-PPh2)2] [BF4]2 (2b, CORM-P2). Upon irradiation with visible light, CO is liberated making especially 2a a promising photo-CORM whereas for 2b a slow and incomplete CO release is observed.

Bimetallic Octahedral Ruthenium–Nickel Carbido Cluster Complexes. Synthesis and Structural Characterization

The reaction of Ru5(CO)15(μ5-C) with Ni(COD)2 in acetonitrile at 80 °C affords the bimetallic octahedral ruthenium-nickel cluster complex Ru5Ni(NCMe)(CO)15(μ6-C), 3. The acetonitrile ligand in 3 can be replaced by CO and NH3 to yield Ru5Ni(CO)16(μ6-C), 4, and Ru5Ni(NH3)(CO)15(μ6-C), 5, respectively. Photolysis of compound 3 in benzene and toluene solvent yielded the η(6)-coordinated benzene and toluene Ru5Ni carbido cluster complexes Ru5Ni(CO)13(η(6)-C6H6)(μ6-C), 6, and Ru5Ni(CO)13(η(6)-C7H8)(μ6-C), 7, respectively. All five new compounds were structurally characterized by single-crystal X-ray diffraction analyses.

Reduction and Protonation of Mo(IV) Imido Complexes with depe Coligands: Generation and Reactivity of a S = 1/2 Mo(III) Alkylnitrene Intermediate

Reduction and protonation of Mo(IV) imido complexes with diphosphine coligands constitutes the second part of the Chatt cycle for biomimetic reduction of N2 to ammonia. In order to obtain insights into the corresponding elementary reactions we synthesized the Mo(IV) ethylimido complex [Mo(CH3CN)(NEt)(depe)2](OTf)2 (2-MeCN) from the Mo(IV)-NNH2 precursor [Mo(NNH2)(OTf)(depe)2](OTf) (1). As shown by UV-vis and NMR spectroscopy, exchange of the acetonitrile ligand with one of the counterions in THF results in formation of the so far unknown complex [Mo(OTf)(NEt)(depe)2](OTf) (2-OTf). 2-MeCN and 2-OTf are studied by spectroscopy and X-ray crystallography in conjunction with DFT calculations. Furthermore, both complexes are investigated by cyclic voltammetry and spectroelectrochemistry. The complex 2-OTf undergoes a two-electron reduction in THF associated with loss of the trans ligand triflate. In contrast, 2-MeCN in acetonitrile is reduced to an unprecedented Mo(III) alkylnitrene complex [Mo(NEt)(CH3CN)(depe)2]OTf (5) which abstracts a proton from the parent Mo(IV) compound 2-MeCN, forming the Mo(III) ethylamido complex 5H and a Mo(II) azavinylidene complex 6. Compound 5 is also protonated to the Mo(III) ethylamido complex 5H in the presence of externally added acid and further reduced to the Mo(II) ethylamido complex 7. The results of this study provide further support to a central reaction paradigm of the Schrock and Chatt cycles: double reductions (and double protonations) lead to high-energy intermediates, and therefore, every single reduction has to be followed by a single protonation (and vice versa). Only in this way the biomimetic conversion of dinitrogen to ammonia proceeds on a minimum-energy pathway.

Bis-chelate N-heterocyclic tetracarbene Ru(II) complexes: Synthesis, structure, and catalytic activity toward transfer hydrogenation of ketones

Ru(II) complexes with two chelating di-N-heterocyclic carbenes (NHC) and two acetonitrile ligands (NHC=1,1′-dialkyl-3,3′-methylene-diimidazol-2,2′-diylidene, and alkyl=methyl and n-butyl) were synthesized and structurally characterized. The crystal structures of the complexes determined by X-ray diffraction analyses show that the Ru(II) center is bound to two bidentate carbene ligands and two acetonitrile molecules, forming a distorted octahedron. The complexes prove to be an efficient catalyst having exceedingly high turnover frequencies and good reusability in transfer hydrogenation of ketones.

Improving the “Livingness” of ATRP by Reducing Cu Catalyst Concentration

The mole percentage of dead chains (Tmol %) was quantified in a normal Cu-mediated atom transfer radical polymerization (ATRP) of methyl acrylate with tris(2-pyridylmethyl)amine and tris[2-(dimethylamino)ethyl]amine as the ligands in acetonitrile. The value for Tmol % significantly exceeded the values predicted for conventional termination between two radicals. The main reason for the additional loss of chain-end functionality was identified as a CuI-induced catalytic radical termination (CRT). The mechanism proposed for this CRT involves the formation of highly active R–CuII/L and/or H–CuII/L intermediates which react with radicals to form dead chains and regenerate the CuI activator. The contribution of CRT to the loss of terminal functionality can be significantly decreased by reducing [CuI] to <1 mM, according to recently developed new ATRP processes.

A Series of Dinuclear Copper Complexes Bridged by Phosphanylbipyridine Ligands: Synthesis, Structural Characterization and Electrochemistry

AbstractThe phosphanylbipyridine ligands 6‐(diphenylphosphanyl)‐4,4′‐dimethyl‐2,2′‐bipyridine (PPh2‐Me2‐bipy, a), 4,4′‐di‐tert‐butyl‐6‐(diphenylphosphanyl)‐2,2′‐bipyridine (PPh2‐tBu2‐bipy, b), and 6‐(diisopropylphosphanyl)‐2,2′‐bipyridine (PiPr2bipy, c) and the corresponding dinuclear copper complexes [Cu2(μ‐PPh2‐Me2‐bipy)2(NCCH3)2](PF6)2 (1), [Cu2(μ‐PPh2‐tBu2‐bipy)2(NCCH3)2](PF6)2 (2), [Cu2(μ‐PiPr2bipy)2(μ‐NCCH3)](PF6)2 (3), and [Cu2(μ‐PiPr2bipy)2{μ‐CNCH(CH3)2}](PF6)2 (4) were synthesized. The X‐ray structures of 1–4 show that the complexes are dinuclear with the bidentate bipyridine coordinating to one copper atom and the phosphane moiety coordinating the other copper center. Complexes 3 and 4 possess short Cu–Cu distances with bridging acetonitrile and isocyanide ligands. The cyclic voltammograms of 1–4 were examined under N2 and CO2. Under N2, 1–3 show four quasi‐reversible 1e– reductions, and under CO2, they show current enhancement at the second reduction. In comparison, complex 4 shows four irreversible reductions under N2 and no current enhancement under CO2.

Synthesis and Characterization of New Complexes of (N-P-Amino Diphenyl Amine) Amino (2-Hydroxy Phenyl) Acetonitrile Ligand with Some Transition Metal Ions

The synthesis and characterization of new complexes of Fe(II), Co(II), Ni(II) and Cu(II) with bidentate (N-p-amino diphenyl amine) amino (2-hydroxy phenyl) acetonitrile ligand has been described .The ligand was prepared from 2-hydroxy benzaldehyde and 4-aminodiphenyl amine in the presence of KCN and acidic medium. The complexes were synthesized by treating an ethanolic solution of the ligand with appropriate amount of metal salts (1:2) (M: L) ratio. The complexes were characterized by using metal and elemental analysis, infrared and electronic spectra, molar conductivity, magnetic susceptibility, and mole ratio method. According to the obtained data the probable coordination geometries of Iron, Cobalt, Nickel and Copper in these complexes are octahedral. All complexes were found to be non-electrolyte in absolute ethanol, and the complexes were formulated as (ML2Cl2). Keywords - α-aminonitrile, Cobalt, Copper,Complexes,Iron and Nickel.

Synthesis and Characterization of New Complexes of 2-(6- Methoxybenzo[d]thiazol-2-ylamino)-2-phenyl acetonitrile Ligand with Manganese (II), Cobalt (II), Nickel (II), Copper (II), Zinc (II) Cadmium (II) and Mercury (II) Divalent Transition Metal Ions

The synthesis and characterization of manganese (ІІ), cobalt (ІІ), nickel (ІІ), copper (ІІ), zinc (ІІ), cadmium (ІІ) and mercury (ІІ) bidentate 2-(6-methoxybenzo(d)thiazol-2-ylamino)-2-phenyl acetonitrile ligand which was prepared from Benz aldehyde and 6-methoxybenzo(d)thiazol-2-amine in the presence of KCN and acidic medium. The complexes were synthesized by treating an ethanolic solution of the ligand with appropriate amount of metal salts (1:2) (M: L) ratio. The complexes were characterized by using metal and elemental chemical analysis, molar conductance, magnetic susceptibility measurements, FTIR , electronic spectral and mole ratio method. According to the obtained data the probable coordination geometries of manganese (ІІ), cobalt (ІІ), nickel (ІІ), copper (ІІ) zinc (ІІ), cadmium (ІІ) and mercury (ІІ) in these complexes are octahedral. All complexes were found to be non-electrolyte in absolute ethanol, and the complexes were formulated as (ML2Cl2) XH2O.

A tetranuclear cadmium(II) complex based on the 2-(quinolin-8-yloxy)acetonitrile ligand

The hydrothermal reaction of 2-(quinolin-8-yloxy)acetonitrile and Cd(ClO(4))(2) yielded the noncentrosymmetric coordination complex tetrakis[μ-2-(quinolin-8-yloxy)acetato]tetrakis[μ-2-(quinolin-8-yloxy)acetonitrile]tetracadmium tetrakis(perchlorate) dihydrate, [Cd(4)(C(11)H(8)NO(3))(4)(C(11)H(8)N(2)O)(4)](ClO(4))(4)·2H(2)O. The local coordination environment around the Cd(II) cation can be best described as a capped octahedron defined by two N atoms and five O atoms from three ligands. The Cd(II) cations are linked by the ligands with Cd-O-Cd and Cd-O-C-C-O-Cd bridges, forming tetranuclear units, there being two independent tertranuclear units in the structure. The fourfold rotoinversion centre sits at the centre of each Cd(4) core. The two perchlorate anions in the asymmetric unit are linked by the water molecule through O-H...O hydrogen bonds.

Structural and Spectroscopic Trends in a Series of Half-Sandwich Scorpionate Complexes

Fifteen half-sandwich scorpionate complexes [(L)M(NCMe)(3)](BF(4))(n) (L = tris(3,5-dimethylpyrazol-1-yl)methane, Tpm(Me,Me), n = 2, 1(M), M = Mn, Fe, Co, Ni; L = tris(3-phenylpyrazol-1-yl)methane, Tpm(Ph), n = 2, 2(M), M = Mn, Fe, Co, Ni; L = hydrotris(3,5-dimethylpyrazol-1-yl)borate, [Tp(Me,Me)](-), n = 1, 3(M), M = Fe, Co, Ni; L = hydrotris(3-phenyl-5-methylpyrazol-1-yl)borate, [Tp(Ph,Me)](-), n = 1, 4(M), M = Mn, Fe, Co, Ni) were prepared by addition of the tripodal ligands to solvated [M(NCMe)(x)](2+) (M = Mn, x = 4; M = Fe, Co, Ni, x = 6) precursor complexes. The product complexes were characterized by (1)H NMR (except M = Mn), UV-vis-NIR, and FTIR spectroscopy. The structures of 2(Mn), 2(Ni), 3(Fe), 3(Co), and 4(Fe) were determined by X-ray crystallography. The data were consistent with complexes of high-spin divalent metal ions in idealized piano-stool geometries in all cases. Consequent lability of the acetonitrile ligands will enable use of these complexes as synthetic precursors and as catalysts. Comparison to previously reported structures of 1(Fe), 1(Co), 2(Fe), and 2(Co), the triflate salt analogues of 4(Co) and 4(Ni), as well as related sandwich complexes (e.g., [(Tp(Me,Me))(2)M]) and solvated metal dications [M(NCMe)(6)](2+) reveals numerous trends in M-N bond lengths. Primary among these are the Irving-Williams series, with significant structural effects also arising from ligand charge and sterics. Systematic trends in spectroscopic data were also observed which further elucidate these issues.

A New Direction in Dye-Sensitized Solar Cells Redox Mediator Development: In Situ Fine-Tuning of the Cobalt(II)/(III) Redox Potential through Lewis Base Interactions

Dye-sensitized solar cells (DSCs) are an attractive renewable energy technology currently under intense investigation. In recent years, one area of major interest has been the exploration of alternatives to the classical iodide/triiodide redox shuttle, with particular attention focused on cobalt complexes with the general formula [Co(L)(n)](2+/3+). We introduce a new approach to designing redox mediators that involves the application of [Co(PY5Me(2))(MeCN)](2+/3+) complexes, where PY5Me(2) is the pentadentate ligand, 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine. It is shown, by X-ray crystallography, that the axial acetonitrile (MeCN) ligand can be replaced by more strongly coordinating Lewis bases (B) to give complexes with the general formula [Co(PY5Me(2))(B)](2+/3+), where B = 4-tert-butylpyridine (tBP) or N-methylbenzimidazole (NMBI). These commonly applied DSC electrolyte components are used for the first time to fine-tune the potential of the redox couple to the requirements of the dye through coordinative interactions with the Co(II/III) centers. Application of electrolytes based on the [Co(PY5Me(2))(NMBI)](2+/3+) complex in combination with a commercially available organic sensitizer has enabled us to attain DSC efficiencies of 8.4% and 9.2% at a simulated light intensity of 100% sun (1000 W m(-2) AM1.5 G) and at 10% sun, respectively, higher than analogous devices applying the [Co(bpy)(3)](2+/3+) redox couple, and an open circuit voltage (V(oc)) of almost 1.0 V at 100% sun for devices constructed with the tBP complex.