Acetonitrile Ligands Research Articles

Triaceto-nitrile-(1,4,7-trimethyl-1,4,7-tri-aza-cyclonona-ne)cobalt(II) bis-(tetra-phenyl-borate).

The title cobalt(II) complex, [Co(C2H3N)3(C9H21N3)](C24H20B)2 or [(tacn)Co(NCMe)3][BPh4]2, has been characterized by single-crystal X-ray diffraction. It incorporates the well-known macrocyclic tacn (1,4,7-trimethyl-1,4,7-tri-aza-cyclo-nona-ne) ligand, which is coordinated facially to the metal center. The complex crystallizes in space group P21/c with Z = 4. The divalent cobalt ion exhibits a six-coordinate octa-hedral geometry by one tacn and three aceto-nitrile ligands. Two non-coordinating tetra-phenyl-borate (BPh4 -) anions are also present.

Zerovalent ruthenium complexes of secondary alkoxyphosphines

The reaction of [RuHCl(CO)L3] (L = PPh3) with cyclohexylphosphine (PH2Cy) affords [RuHCl(CO)L2(PH2Cy)], protonation of which in acetonitrile with HX affords [RuCl(NCMe)(CO)L2(PH2Cy)]X (X = ClO4, OTf, PF6) salts while HCl provides [RuCl2(CO)L2(PH2Cy)]. The labile chloride and/or acetonitrile ligands are replaced by CO, CNC6H2Me3-2,4,6, [Et2NCS2]– or [Tp]– (Tp = hydrotris(pyrazolyl)borate) to provide [RuCl(CO)2L2(PH2Cy)]+, [Ru[Cl(CO)(CNC6H2Me3-2,4,6)L2(PH2Cy)]+, [Ru(S2CNEt2)(CO)L2(PH2Cy)]+ and [Ru(CO)L(Tp)(PH2Cy)]+ salts. Deprotonation of [RuCl(CO)2L2(PH2Cy)]OTf in benzene affords [RuCl(PHCy)(CO)2L2], but in methanol the secondary methoxyphosphine complex [Ru(CO)2L2{PH(OMe)Cy}] is obtained, as is [Ru(CO)(CNC6H2Me3-2,4,6)L2{PH(OMe)Cy}] from [Ru[Cl(CO)(CNC6H2Me3-2,4,6)L2(PH2Cy)]OTf. The reactions of [Ru(CO)2L2{PH(OMe)Cy}] with CO, CNC6H2Me3-2,4,6 or dppe afford [Ru(CO)3L{PH(OMe)Cy}], [Ru(CO)2(CNC6H2Me3-2,4,6)L2{PH(OMe)Cy}] or [Ru(CO)2(dppe){PH(OMe)Cy}], resectively, in each case demonstrating a preference for dissociation of PPh3 rather than PH(OMe)Cy. Aerial oxidation of [Ru(CO)2L2{PH(OMe)Cy}] results in oxidation of one carbonyl ligand with formation of the carbonato complex [Ru(O2CO)(CO)L2{PH(OMe)Cy}]. The reaction of [Ru(CO)2L2{PH(OMe)Cy}] with ethynyl benzene provides two diastereomers of [RuH(CCPh)(CO)2L{PH(OMe)Cy}], while with anhydrous HCl, the cyclohexyl phosphine complex [RuCl2(CO)L2(PH2Cy)] is observed.

Tc(NO)(Cp)(PPh3)Cl] and [Tc(NO)(Cp)(PPh3)(NCCH3)](PF6), and Their Reactions with Pyridine and Chalcogen Donors.

Reactions of the technetium(I) nitrosyl complex [Tc(NO)(Cp)(PPh3)Cl] with triphenylphosphine chalcogenides EPPh3 (E = O, S, Se), and Ag(PF6) in a CH2Cl2/MeOH mixture (v/v, 2/1) result in an exchange of the chlorido ligand and the formation of [Tc(NO)(Cp)(PPh3)(EPPh3)](PF6) compounds. The cationic acetonitrile complex [Tc(NO)(Cp)(PPh3)(NCCH3)]+ is formed when the reaction is conducted in NCCH3 without additional ligands. During the isolation of the corresponding PF6- salt a gradual decomposition of the anion was detected in the solvent mixture applied. The yields and the purity of the product increase when the BF4- salt is used instead. The acetonitrile ligand is bound remarkably strongly to technetium and exchange reactions readily proceed only with strong donors, such as pyridine or ligands with 'soft' donor atoms, such as the thioether thioxane. Substitutions on the cyclopentadienyl ring do not significantly influence the ligand exchange behavior of the starting material. 99Tc NMR spectroscopy is a valuable tool for the evaluation of reactions of the complexes of the present study. The extremely large chemical shift range of this method allows the ready detection of corresponding ligand exchange reactions. The observed 99Tc chemical shifts depend on the donor properties of the ligands. DFT calculations support the discussions about the experimental results and provide explanations for some of the unusual findings.

C≡N and N≡O Bond Cleavages of Acetonitrile and Nitrosyl Ligands at a Dimolybdenum Center to Render Ethylidyne and Acetamidinate Ligands.

Extended reduction of [Mo2Cp2(μ-Cl)(μ-PtBu2)(NO)2] (1) with Na(Hg) in acetonitrile (MeCN) at room temperature resulted in an unprecedented full cleavage of the C≡N bond of a coordinated MeCN molecule to yield the vinylidene derivative Na[Mo2Cp2(μ-PtBu2)(μ-CCH2)(NO)2], which upon protonation with (NH4)PF6 gave the ethylidyne complex [Mo2Cp2(μ-PtBu2)(μ-CMe)(NO)2] [Mo1-Mo2 = 2.9218(2) Å] in a selective and reversible way. Controlled reduction of 1 at 273 K yielded instead, after protonation, the 30-electron acetamidinate complex [Mo2Cp2(μ-PtBu2)(μ-κN:κN'-HNCMeNH)(μ-NO)]PF6 [Mo1-Mo2 = 2.603(2) Å], in a process thought to stem from the paramagnetic MeCN-bridged intermediate [Mo2Cp2(μ-PtBu2)(μ-NCMe)(NO)2], followed by a complex sequence of elementary steps including cleavage of the N≡O bond of a nitrosyl ligand.

An extremely electron poor Au(III) trication bearing acetonitrile ligands.

The synthesis and structural characterization of an electron poor Au(III) trication bearing 2 imidazole and 2 acetonitrile ligands is described. The new complex is capable of aryl C-H metalation with the formation of a monomesitylene complex and also demonstrated to be highly oxidizing in the rapid room temperature conversion of cyclohexene to benzene.

Synthesis of Novel Enantiopure Amino- and Azidopyran Building Blocks and Their Click Reactions to Multivalent Carbohydrate Mimetics

AbstractThe synthesis of three enantiopure 1,2-oxazine-derived azides was optimized and the reductions of these compounds to amino alcohols were studied. As a primary aim of this study, the copper-catalyzed (3+2)-cycloadditions of the azides were investigated, employing a series of alkynes, dialkynes, and trialkynes, which afforded the corresponding mono-, di-, and trivalent triazole derivatives with different rigid and flexible core elements. The expected click products were generally obtained in good to excellent yields when copper iodide was employed in presence of tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA) as ligand in acetonitrile at room temperature. Several of the products were subjected to exhaustive hydrogenolysis reactions, leading to enantiopure compounds with aminopyran substructures, which can be regarded as carbohydrate mimetics.

On the formation of inner-sphere solvation complexes in dilute acetonitrile solutions of the Hg(NO3)2 and Hg(TfO)2 salts: a Molecular Dynamics study

The solvation properties of dilute acetonitrile solutions of the Hg(NO3)2 and Hg(TfO)2 salts have been investigated by using Molecular Dynamics simulations. The Hg2+ ion in acetonitrile was found to coordinate both counterions and acetonitrile molecules in its first solvation sphere by forming inner-sphere complexes. However, different geometries of the Hg2+ solvation polyhedra are formed depending on the counterion: in the Hg(NO3)2 salt solution, Hg2+ forms a 8-fold cluster of acetonitrile and nitrate ligands with a square antiprism symmetry, while in the system containing the Hg(TfO)2 salts, the Hg2+ solvation shell is composed of eight ligands arranged in a C2 symmetry.

Valve turning towards on-cycle in cobalt-catalyzed Negishi-type cross-coupling

Ligands and additives are often utilized to stabilize low-valent catalytic metal species experimentally, while their role in suppressing metal deposition has been less studied. Herein, an on-cycle mechanism is reported for CoCl2bpy2 catalyzed Negishi-type cross-coupling. A full catalytic cycle of this kind of reaction was elucidated by multiple spectroscopic studies. The solvent and ligand were found to be essential for the generation of catalytic active Co(I) species, among which acetonitrile and bipyridine ligand are resistant to the disproportionation events of Co(I). Investigations, based on Quick-X-Ray Absorption Fine Structure (Q-XAFS) spectroscopy, Electron Paramagnetic Resonance (EPR), IR allied with DFT calculations, allow comprehensive mechanistic insights that establish the structural information of the catalytic active cobalt species along with the whole catalytic Co(I)/Co(III) cycle. Moreover, the acetonitrile and bipyridine system can be further extended to the acylation, allylation, and benzylation of aryl zinc reagents, which present a broad substrate scope with a catalytic amount of Co salt. Overall, this work provides a basic mechanistic perspective for designing cobalt-catalyzed cross-coupling reactions.

Design of Stereogenic‐at‐Iron Catalysts with a (3+2+1)‐Ligand Sphere

AbstractA stereogenic‐at‐iron(II) catalyst scaffold is introduced which contains one coordinated meridional tridentate imidazolidin‐2‐ylidene‐functionalized 2,2′‐bipyridine, one bidentate pyrazolylpyridine, and one monodentate acetonitrile ligand. This (3+2+1)‐coordination sphere implements a stereogenic iron center. A carbon stereocenter in the N‐heterocyclic carbene moiety controls the absolute metal‐centered configuration. The bench‐stable diamagnetic iron(II) complexes can be synthesized in a highly diastereoselective fashion from iron dibromide in an efficient one‐pot coordination reaction. The obtained enantiopure complexes were applied as chiral catalysts in the ring contraction of an isoxazole to a chiral 2H‐azirine (quantitative yields, up to 90 : 10 er).

A Brief Overview of the General Characteristics and Reactivity Towards Dioxygen of the Ferrous Tris (2-Pyridylmethyl Amine) Series Complexes is Presented

This paper examines the coordination chemistry of iron to TPA-like nitrogenous tripod ligands, focusing on how the spin state of the metal is affected by the presence of steric constraints and the coordination of acetonitrile ligands which can be displaced easily. Additionally, the reactivity of the derivatives with molecular oxygen, the conservation of geometry between the solid state and the solution and the various coordination geometries, electronic properties, and redox properties of ferrous tris(2-pyridylmethyl amine) series complexes are discussed. Furthermore, the molecular mechanisms of reactivity of these complexes are evaluated, providing an outlook for future research

Spectrophotometric study of basic properties of glycosylated tetraphenylporphin derivatives

The paper presents the results of spectrophotometric study of the basic properties of glycosylated substituted derivatives of 5,10,15,20-tetraphenylporphyrin, namely 5-(4′- O -galactosylphenyl)-10,15,20-tris( N -methylpyridin-3-yl)porphine, 5,15-bis(4′- O -galactosylphenyl)-10,20-bis( N -methylpyridin-3-yl)porphine, 5,10,15,20-tetra( N -methylpyridin-3-yl)porphin, 5,10,15,20-tetra(4- O -galactosylphenyl)porphin. The basic properties of the studied ligands in acetonitrile at 298 K were studied by spectrophotometric method. The effect of glycosylated fragments, as constituents of a macromolecule, on protolytic equilibria during acid-base interactions of the ligand in basic media and the change in the reactivity of porphyrin ligands depending on the nature of the peripheral substituent was analyzed.

The double cluster compound [Nb6Cl14(MeCN)4][Nb6Cl14(pyz)4]·6MeCN (Me: methyl, pyz: pyrazine) with a layered structure resulting from weak intermolecular interactions

Abstract The synthesis and the crystal structure of the double cluster compound [Nb6Cl14(MeCN)4][Nb6Cl14(pyz)4]·6CH3CN are described. The synthesis is based on a partial ligand exchange reaction, which proceeds upon dissolving [Nb6Cl14(pyz)4]·2CH2Cl2 in acetonitrile. The compound is built up of two discrete neutral cluster units, which consist of octahedra of Nb6 atoms coordinated by 12 edge-bridging chlorido and two terminal chlorido ligands, and four acetonitrile ligands on one and four pyrazine ligands on the other cluster unit. Co-crystallized acetonitrile molecules are also present. The single-crystal structure determination has revealed a cluster arrangement in which the [Nb6Cl14(pyz)4] units are connected by (halogen) lone-pair–(pyrazine) π interactions. These lead to chains of [Nb6Cl14(pyz)4] clusters. These chains are further connected to cluster layers by (nitrile-halogen) dipole–dipole interactions, in which the [Nb6Cl14(MeCN)4] and co-crystallized MeCN molecules are also involved. These cluster layers are arranged parallel to the crystallographic {011} plane.

Formation and Surface Behavior of Pt and Pd Complexes with Ligand Systems Derived from Nitrile-functionalized Ionic Liquids Studied by XPS.

The front cover artwork is provided by the groups of Prof. Hans-Peter Steinrück and Prof. Peter Wasserscheid at the Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg. The image shows substitution of volatile acetonitrile ligands by a nitrile-functionalized imidazolium cation. The formed cationic complex and the counter ions exhibit a specific preferential orientation at the ionic liquid/gas interface, which can be studied by angle-resolved XPS. Read the full text of the Research Article at 10.1002/cphc.202200391.

Front Cover: Formation and Surface Behavior of Pt and Pd Complexes with Ligand Systems Derived from Nitrile‐functionalized Ionic Liquids Studied by XPS (ChemPhysChem 2/2023)

The Front Cover shows substitution of volatile acetonitrile ligands by a nitrile-functionalized imidazolium cation. The formed cationic complex and the counter ions exhibit a specific preferential orientation at the ionic liquid/gas interface, which can be studied by angle-resolved XPS. More information can be found in the Research Article by Hans-Peter Steinrück and co-workers.

A Planar‐Chiral Palladium Complex Derived from a Weak Oxygen Donor N,N‐Diisopropyl Ferrocenecarboxamide Ligand

AbstractThe reaction of chiral 2‐iodoferrocenecarboxamide, palladium(II) acetate, and triphenylphosphine ligand in acetonitrile has been resulted in the formation of an air‐stable chiral (Sp)‐2‐(N,N‐diisopropyl ferrocenecarboxamide) triphenylphosphine palladium(II) iodide complex. The isolated chiral palladium complex was thoroughly characterized by multi‐nuclear (1H, 13C, 31P) NMR, IR spectroscopy, mass spectrometry, polarimetry, CHN analysis, cyclic voltammetry and single crystal X‐ray crystallography (XRD). The single‐crystal XRD analysis reveals a square planar geometry around the palladium atom with a strong amide oxygen‐Pd bond [2.095(6) Å]. The palladium complex crystallized in the C2‐chiral space group having a Flack parameter value of 0.011(14), which is close to 0 and indicative of the enantiomeric purity of the palladium complex. The electrochemical study reveals a two‐electron redox couple due to the ferrocenyl Fe(II) atom and the palladacyclic Pd(II) center. In differential pulse voltammetry (DPV), two peaks were observed at 450 mV and 590 mV vs. Ag/AgCl. Further, the synthesized chiral palladacyle has also been explored in Suzuki‐Miyaura coupling reaction as a substrate and as a catalyst for Tsuji‐Trost coupling and phosphonation reactions.

Synthesis, crystal structure and thermal properties of bis-(aceto-nitrile-κN)bis-(3-bromo-pyridine-κN)bis-(thio-cyanato-κN)cobalt(II).

Single crystals of the title compound, [Co(NCS)2(C5H4BrN)2(C2H3N)2], were obtained by the reaction of Co(NCS)2 with 3-bromo-pyridine in aceto-nitrile. The CoII cations lie on crystallographic inversion centers and are coordinated by two N-bonded thio-cyanate anions, two 3-bromo-pyridine and two aceto-nitrile ligands thereby forming slightly distorted CoN6 octa-hedra. In the crystal, these complexes are linked by C-H⋯S and C-H⋯N hydrogen bonds into a three-dimensional network. In the direction of the crystallographic b-axis, the complexes are arranged into columns with neighboring 3-bromo-pyridine ligands stacked onto each other, indicating π-π inter-actions. The CN stretching vibration of the thio-cyanate anions is observed at 2066 cm-1, in agreement with the presence of only N-bonded anionic ligands. TG-DTA measurements reveal that in the first mass loss the aceto-nitrile ligands are removed and that in the second step, half of a 3-bromo-pyridine ligand is lost, leading to the formation of a polymeric compound with the composition [(Co(NCS)2)2(C5H4BrN)3] n already reported in the literature.

Preparation, photoluminescence and excited state properties of the homoleptic cluster cation [(W6I8)(CH3CN)6]4.

Solvated tungsten iodide cluster compounds are presented with the homoleptic cluster cation [(W6I8)(CH3CN)6]4+ and the heteroleptic [(W6I8)I(CH3CN)5]3+, synthesized from W6I22 in acetonitrile. Crystal structures were solved and refined on deep red single-crystals of [(W6I8)(CH3CN)6](I3)(BF4)3·H2O, [(W6I8)I(CH3CN)5](I3)2(BF4), and on a yellow single-crystal of [W6I8(CH3CN)6](BF4)4·2(CH3CN) on the basis of X-ray diffraction data. The structure of the homoleptic [(W6I8)(CH3CN)6]4+ cluster is based on the octahedral [W6I8]4+ tungsten iodide cluster core, coordinated by six apical acetonitrile ligands. The electron localisation function of [(W6I8)(CH3CN)6]4+ is calculated and solid-state photoluminescence and its temperature depedence are reported. Additionally, photoluminescence and transient absorption measurements in acetonitrile are shown. Results of the obtained data are compared to compounds containing [(M6I8)I6]2- and [(M6I8)L6]2- (M = Mo or W; L = ligand) clusters.

Experimental Mechanistic Analysis of Carbonyl Hydrosilylation Catalyzed by Abu-Omar’s Rhenium(V) Oxo Complex

Based on new experimental data, a refined mechanistic picture of carbonyl hydrosilylation with hydrosilanes catalyzed by a cationic rhenium(V) oxo complex introduced by Abu-Omar is presented. A stereochemical analysis employing a silicon-stereogenic hydrosilane as a stereochemical probe revealed that both free silylcarboxonium ions and neutral rhenium(V) hydrides are key intermediates in the catalytic cycle. Moreover, nuclear magnetic resonance spectroscopic measurements and further control experiments shed light on the Si–H bond activation and the reactivity of the rhenium(V) hydride. These experiments also contributed to the understanding of the role of the acetonitrile ligand that is introduced with Abu-Omar’s complex. Acetonitrile suppresses overreduction while without deoxygenation prevails.

Zinc‐bis(imino)pyridine Complexes as Catalysts for Azide‐Alkyne Cycloaddition in Water

AbstractTwo new zinc(II) complexes, [2,6‐bis(methylphenyliminomethyl)pyridine]ZnBr2 (2 a) and [2,6‐bis(triflouromethylphenyliminomethyl)pyridine]ZnBr2 (2 b) were synthesized by the reactions of corresponding 2,6‐bis(imino)pyridine based [NNN]‐pincer ligand and anhydrous ZnBr2 in acetonitrile as a solvent. The catalytic properties of zinc(II) complexes were examined in azide‐alkyne cycloaddition reactions in water. The zinc(II) complexes were characterized by UV‐Vis, 1H NMR, IR, elemental analysis and mass spectroscopy. The zinc complex [2,6‐bis(triflouromethylphenyliminomethyl)pyridine]ZnBr2 was characterized by X‐ray crystallography. The zinc(II) complexes efficiently catalyzed the azide‐alkyne cycloaddition reaction for the synthesis of 1,2,3‐triazoles (mixture of 1,4‐ and 1,5‐disubstituted 1,2,3‐triazoles) in water with good to excellent yields.

Acetonitrile Ligand Photosubstitution in Ru(II) Complexes Directly from the 3MLCT State.

The excited states of the series [Ru(tpy)(L)(CH3CN)]n+ (1-11) (n = 1, 2) containing bidentate ligands L with varying electron-donating ability were characterized through Arrhenius analysis of the temperature dependence of their excited-state lifetimes. Complexes 1-11 undergo photoinduced CH3CN dissociation upon 450 nm irradiation with ligand exchange quantum yields that increase with the energy barrier to populating a dissociative triplet ligand field (3LF) state from the lowest-energy triplet metal-to-ligand charge transfer (3MLCT) excited state. Combined with DFT calculations, the data indicate that ligand photodissociation in 1-11 occurs directly from the 3MLCT state instead of a 3LF state. This finding is in contrast to the generally accepted mechanism for ligand photodissociation in Ru(II) complexes and indicates that alternative pathways for photoinduced ligand dissociation are available. These results can widely impact design principles for applications that require ligand photodissociation, such as photochemotherapy and photocatalysis, as well as for those where photosubstitution is undesirable, such as solar energy conversion.