The stepwise addition of increasing amounts of Au(PPh3)Cl to [HRu4(CO)12]3- (1) results in the sequential formation of [HRu4(CO)12(AuPPh3)]2- (2), [HRu4(CO)12(AuPPh3)2]- (3), and HRu4(CO)12(AuPPh3)3 (4). Alternatively, 4 can be obtained upon addition of HBF4·Et2O (two mole equivalents) to 3. Further addition of acid to 3 (three mole equivalents) results in the formation of the tetra-aurated cluster Ru4(CO)12(AuPPh3)4 (5). Compounds 2-5 have been characterized by IR, 1H and 31P{1H} NMR spectroscopies. Moreover, the molecular structures of 3-5 have been determined by single crystal X-ray diffraction as [NEt4][3]·2CH2Cl2, 4-b·2CH2Cl2, 4-a, 5·0.5CH2Cl2·solv, and 5·solv crystalline solids. Two different isomers of 4, that is 4-a and 4-b, have been crystallographically characterized and their rapid interconversion in solution was studied by variable temperature 1H and 31P{1H} NMR spectroscopies. Weak aurophilic Auâ¯Au contacts have been detected in the solid state structures of 3-5. Computational studies have been performed in order to elucidate bonding and isomerism, as well as to predict the possible structure of the elusive species 2.
The first N-ferrocenyl aminocarbyne complex, [Fe2Cp2(CO)2(µ-CO){µ-CN(Me)(Fc)}]CF3SO3 ([2]CF3SO3), was synthesized with an 88% yield from [Fe2Cp2(CO)4], isocyanoferrocene (CNFc), and methyl triflate. The synthesis proceeded through the intermediate formation of [Fe2Cp2(CO)3(CNFc)], 1. Multinuclear NMR experiments revealed the presence of cis and trans isomers for [2]CF3SO3 in organic solvents, in agreement with DFT outcomes. Electrochemical and spectroelectrochemical studies demonstrated one reduction process occurring prevalently at the diiron core and one oxidation involving the ferrocenyl substituent. The oxidation process is expected to favor the redox activation of [2]+ in a biological environment. Both [2]CF3SO3 and its phenyl analogue [Fe2Cp2(CO)2(µ-CO){µ-CN(Me)(Ph)}]CF3SO3 ([3]CF3SO3), prepared for comparison, exerted moderate antiproliferative activity against the human cancer cell lines A431, HCT-15, PSN-1, 2008, and U1285. However, [2]CF3SO3 exhibited a higher cytotoxicity than [3]CF3SO3, showed a substantial ability to induce intracellular ROS production, and outperformed cisplatin in a three-dimensional SCLC cell model.
The two enantiomers of chiral phosphonate 4-phenyldinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepine 4-oxide, O=PPh(BINOL), were synthesized from the proper 1,1'-bi-2-naphtol (BINOL) enantiomer and characterized. The structure of the (S)-enantiomer was elucidated by means of single-crystal X-ray diffraction. The reaction with anhydrous ZnBr2 afforded complexes having the general formula [ZnBr2{O=PPh(BINOL)}2] that showed intense fluorescence centered in the near-UV region rationalized on the basis of TD-DFT calculations. The corresponding Mn(II) complexes with the general formula [MnX2{O=PPh(BINOL)}2] (X = Cl, Br) exhibited dual emission upon excitation with UV light, with the relative intensity of the bands dependent upon the choice of the halide. The highest energy transition is comparable with that of the Zn(II) complex, while the lowest energy emission falls in the red region of the spectrum and is characterized by lifetimes in the hundreds of microseconds range. Although the emission at lower energy can also be achieved by direct excitation of the metal center, the luminescence decay curves suggest that the band in the red range is possibly derived from BINOL-centered excited states populated by intersystem crossing.
The indole scaffold has been established as a key organic moiety for developing new drugs; on the other hand, a range of diiron bis-cyclopentadienyl complexes have recently emerged for their promising anticancer potential. Here, we report the synthesis of novel diiron complexes with an indole-functionalized vinyliminium ligand (2-5) and an indole-lacking analogue for comparative purposes (6), which were characterized by analytical and spectroscopic techniques. Complexes 2-6 are substantially stable in DMSOd6 and DMEM-d solutions at 37 °C (8% average degradation after 48 h) and display a balanced hydrophilic/lipophilic behaviour (LogPow values in the range -0.32 to 0.47), associated with appreciable water solubility. The complexes display selective antiproliferative potency towards several cancer cells in monolayer cultures, mainly in the low micromolar range, with reduced toxicity towards noncancerous epithelial cells. Thus, the cytotoxicity of the complexes is comparable to or better than clinically used metallopharmaceutical cisplatin. Comparing the antiproliferative activity obtained for complexes containing different ligands, we confirmed the importance of the indolyl group in the mechanism of antiproliferative activity of these complexes. Cell-based mechanistic studies suggest that the investigated diiron vinyliminium complexes (DVCs) show cytostatic rather than cytotoxic effects and subsequently induce a population of cells to undergo apoptosis. Furthermore, the molecular mechanism of action involves interactions with mitochondrial DNA and proteins, the reactive oxygen species (ROS)-scavenging properties and antioxidant activity of these complexes in cancer cells. This study highlights the importance of DVCs to their cancer cell activity and reinforces their prospective therapeutic potential as anticancer agents.
Antineoplastic Agents , Coordination Complexes , Neoplasms , Reactive Oxygen Species/metabolism , Antioxidants/pharmacology , Antineoplastic Agents/chemistry , Homeostasis , Indoles/pharmacology , Coordination Complexes/chemistry , Apoptosis , Cell Line, Tumor , Neoplasms/drug therapy
The reaction of [Ru6C(CO)16]2- (1) with NaOH in DMSO resulted in the formation of a highly reduced [Ru6C(CO)15]4- (2), which was readily protonated by acids, such as HBF4·Et2O, to [HRu6C(CO)15]3- (3). Oxidation of 2 with [Cp2Fe][PF6] or [C7H7][BF4] in CH3CN resulted in [Ru6C(CO)15(CH3CN)]2- (5), which was quantitatively converted into 1 after exposure to CO atmosphere. The reaction of 2 with a mild methylating agent such as CH3,I afforded the purported [Ru6C(CO)14(COCH3)]3- (6). By employing a stronger reagent, that is, CF3SO3CH3, a mixture of [HRu6C(CO)16]- (4), [H3Ru6C(CO)15]- (7), and [Ru6C(CO)15(CH3CNCH3)]- (8) was obtained. The molecular structures of 2-5, 7, and 8 were determined by single-crystal X-ray diffraction as their [NEt4]4[2]·CH3CN, [NEt4]3[3], [NEt4][4], [NEt4]2[5], [NEt4][7], and [NEt4][8]·solv salts. The carbyne-carbide cluster 6 was partially characterized by IR spectroscopy and ESI-MS, and its structure was computationally predicted using DFT methods. The redox behavior of 2 and 3 was investigated by electrochemical and IR spectroelectrochemical methods. Computational studies were performed in order to unravel structural and thermodynamic aspects of these octahedral Ru-carbide carbonyl clusters displaying miscellaneous ligands and charges in comparison with related iron derivatives.
The chemistry of 1,2,4,5-tetrazines has attracted considerable interest both from a synthetic and applicative standpoint. Recently, regioselective reactions with alkynes and alkenes have been reported to be favored once the tetrazine ring is coordinated to Re(I), Ru(II), and Ir(III) centers. Aiming to further explore the effects of metal coordination, herein, we unveil the unexplored reactivity of tetrazines with chalcogenocyanate anions. Thus, ruthenium(II) tetrazine complexes, [RuCl{κ2N-3-(2-pyridyl)-6-R-1,2,4,5-tetrazine}(η6-arene)]+ (arene = p-cymene, R = H, [1a]+, R = Me, [1b]+, R = 2-pyridyl, [1c]+; arene = C6Me6, R = H, [1d]+, R = Me, [1e]+; PF6- salts), reacted quantitatively and in mild conditions with M(ECN) salts (M = Na, K, Bu4N; E = O, S, Se). The addition of thiocyanate or selenocyanate to the tetrazine ligand is regioselective and afforded, via N2 release, 1,2,4-triazine-5-chalcogenone heterocycles, the one with selenium being unprecedented. The novel ruthenium complexes [RuCl{κ2N-(2-pyridyl)}{triazine chalcogenone}(η6-arene)] 2a-e (sulfur), 3b, 3d, and 3e (selenium) were characterized by analytical (CHNS analyses, conductivity), spectroscopic (IR, multinuclear and two-dimensional (2D) NMR), and spectrometric (electrospray ionization mass spectrometry (ESI-MS)) techniques. According to density functional theory (DFT) calculations, the nucleophilic attack of SCN- on the tetrazine ring is kinetically driven. Compound 2b is selectively and reversibly mono-protonated on the triazine ring by HCl or other strong acids, affording a single tautomer. When reactions of chalcogenocyanates were performed on the 2,2'-bipyridine (bpy) complex [RuCl(bpy)(η6-p-cymene)]+, the chloride substitution products [Ru(ECN)(bpy)(η6-p-cymene)]+ (E = O, [4]+; E = S, [5]+; E = Se, [6]+) were obtained in 82-90% yields (PF6- salts). Combined spectroscopic data (IR, 1H/13C/77Se NMR) was revealed to be a useful tool to study the linkage isomerism of the chalcogenocyanate ligand in [4-6]+.
Diiron µ-aminocarbyne complexes [Fe2Cp2(NCMe)(CO)(µ-CO){µ-CN(Me)(R)}]CF3SO3 (R = Xyl, [1aNCMe]CF3SO3; R = Me, [1bNCMe]CF3SO3; R = Cy, [1cNCMe]CF3SO3; R = CH2Ph, [1dNCMe]CF3SO3), freshly prepared from tricarbonyl precursors [1a-d]CF3SO3, reacted with NaOCN (in acetone) and NBu4SCN (in dichloromethane) to give [Fe2Cp2(kN-NCO)(CO)(µ-CO){µ-CN(Me)(R)}] (R = Xyl, 2a; Me, 2b; Cy, 2c) and [Fe2Cp2(kN-NCS)(CO)(µ-CO){µ-CN(Me)(CH2Ph)}], 3 in 67-81% yields via substitution of the acetonitrile ligand. The reaction of [1aNCMe-1cNCMe]CF3SO3 with KSeCN in THF at reflux temperature led to the cyanide complexes [Fe2Cp2(CN)(CO)(µ-CO){µ-CNMe(R)}], 6a-c (45-67%). When the reaction of [1aNCMe]CF3SO3 with KSeCN was performed in acetone at room temperature, subsequent careful chromatography allowed the separation of moderate amounts of [Fe2Cp2(kSe-SeCN)(CO)(µ-CO){µ-CN(Me)(Xyl)}], 4a, and [Fe2Cp2(kN-NCSe)(CO)(µ-CO){µ-CN(Me)(Xyl)}], 5a. All products were fully characterized by elemental analysis, IR, and multinuclear NMR spectroscopy; moreover, the molecular structure of trans-6b was ascertained by single crystal X-ray diffraction. DFT calculations were carried out to shed light on the coordination mode and stability of the {NCSe-} fragment.
Heterometallic Chini-type clusters [Pt6-xNix(CO)12]2- (x = 0-6) were obtained by reactions of [Pt6(CO)12]2- with Ni-clusters such as [Ni6(CO)12]2-, [Ni9(CO)18]2- and [H2Ni12(CO)21]2-, or from [Pt9(CO)18]2- and [Ni6(CO)12]2-. The Pt/Ni composition of [Pt6-xNix(CO)12]2- (x = 0-6) depended on the nature of the reagents employed and their stoichiometry. Reactions of [Pt9(CO)18]2- with [Ni9(CO)18]2- and [H2Ni12(CO)21]2-, as well as reactions of [Pt12(CO)24]2- with [Ni6(CO)12]2-, [Ni9(CO)18]2- and [H2Ni12(CO)21]2-, afforded [Pt9-xNix(CO)18]2- (x = 0-9) species. [Pt6-xNix(CO)12]2- (x = 1-5) were converted into [Pt12-xNix(CO)21]4- (x = 2-10) upon heating in CH3CN at 80 °C, with almost complete retention of the Pt/Ni composition. Reaction of [Pt12-xNix(CO)21]4- (x ≈ 8) with HBF4·Et2O afforded the [HPt14+xNi24-x(CO)44]5- (x ≈ 0.7) nanocluster. Finally, [Pt19-xNix(CO)22]4- (x = 2-6) could be obtained by heating [Pt9-xNix(CO)18]2- (x = 1-3) in CH3CN at 80 °C, or [Pt6-xNix(CO)12]2- (2-4) in DMSO at 130 °C. The molecular structures of these new alloy nanoclusters have been determined by single crystal X-ray diffraction. The site preference of Pt and Ni within their metal cages has been computationally investigated. The electrochemical and IR spectroelectrochemical behavior of [Pt19-xNix(CO)22]4- (x = 3.11) has been studied and compared to the isostructural homometallic nanocluster [Pt19(CO)22]4-.
Dimetallic complexes are suitable platforms for the assembly of small molecular units, and the reactivity of bridging alkenyl ligands has been widely investigated to model C-C bond forming processes. Here, we report the unusual coupling of an alkenyl ligand, bridging coordinated on a diruthenium scaffold, with a series of alkynes, revealing two possible outcomes. The diruthenium complex [Ru2Cp2(Cl)(CO)(µ-CO){µ-η1:η2-C(Ph)îCH(Ph)}], 2, was prepared in two steps from [Ru2Cp2(CO)2(µ-CO){µ-η1:η2-C(Ph)îCH(Ph)}]BF4, [1]BF4, in 69% yield. Then, the reaction of 2 with C2(CO2Me)2, promoted by AgCF3SO3 in dichloromethane, afforded in 51% yield the complex [Ru2Cp2(CO)2{µ-η3:η2-C(Ph)CH(Ph)C(CO2Me)C(CO2Me)}]CF3SO3, [3]CF3SO3, containing a ruthenacyclopentene-based hydrocarbyl ligand. On the other hand, 2 reacted with other alkynes and AgX salts to give the butadienyl complexes [Ru2Cp2(CO)2{µ-η3:η2-C(R)CH(R')C(Ph)C(Ph)}]X (R = R' = H, [4]BF4; R = R' = Me, [5]CF3SO3; R = R' = Ph, [6]CF3SO3; R = Ph, R' = H, [7]CF3SO3), in 42-56% yields. All products were characterized by IR and NMR spectroscopy, and by single crystal X-ray diffraction in the cases of 2, [3]CF3SO3 and [6]BF4. DFT calculations highlighted the higher stability of [4-7]+-like structures with respect to the corresponding [3]+-like isomers. It is presumable that [3]+-like isomers initially form as kinetic intermediates, then undergo H-migration which is disfavoured in the presence of carboxylato substituents on the alkyne. Such hypothesis was supported by the computational optimization of the transition states for H-migration in the cases of R = R' = H and R = R' = CO2Me.
The reactions of [HRu3(CO)11]- (1) with M(I) (M = Cu, Ag, and Au) compounds such as [Cu(CH3CN)4][BF4], AgNO3, and Au(Et2S)Cl afford the 2-D molecular alloy clusters [CuRu6(CO)22]- (2), [AgRu6(CO)22]- (3), and [AuRu5(CO)19]- (4), respectively. The reactions of 2-4 with PPh3 result in mixtures of products, among which [Cu2Ru8(CO)26]2- (5), Ru4(CO)12(CuPPh3)4 (6), Ru4(CO)12(AgPPh3)4 (7), Ru(CO)3(PPh3)2 (8), and HRu3(OH)(CO)7(PPh3)3 (9) have been isolated and characterized. The molecular structures of 2-6 and 9 have been determined by single-crystal X-ray diffraction. The metal-metal bonding within 2-5 has been computationally investigated by density functional theory methods. In addition, the [NEt4]+ salts of 2-4 have been tested as catalyst precursors for transfer hydrogenation on the model substrate 4-fluoroacetophenone using iPrOH as a solvent and a hydrogen source.
The molecular Pt nanocluster [Pt27(CO)31]4- (14-) was obtained by thermal decomposition of [Pt15(CO)30]2- in tetrahydrofuran under a H2 atmosphere. The reaction of 14- with increasing amounts of HBF4·Et2O afforded the previously reported [Pt26(CO)32]2- (32-) and [Pt26(CO)32]- (3-). The new nanocluster 14- was characterized by IR and UV-visible spectroscopy, single-crystal X-ray diffraction, direct-current superconducting quantum interference device magnetometry, cyclic voltammetry, IR spectroelectrochemistry (IR SEC), and electrochemical impedance spectroscopy. The cluster displays a cubic-close-packed Pt27 framework generated by the overlapping of four ABCA layers, composed of 3, 7, 11, and 6 atoms, respectively, that encapsulates a fully interstitial Pt4 tetrahedron. One Pt atom is missing within layer 3, and this defect (vacancy) generates local deformations within layers 2 and 3. These local deformations tend to repair the defect (missing atom) and increase the number of Pt-Pt bonding contacts, minimizing the total energy. The cluster 14- is perfectly diamagnetic and displays a rich electrochemical behavior. Indeed, six different oxidation states have been characterized by IR SEC, unraveling the series of 1n- (n = 3-8) isostructural nanoclusters. Computational studies have been carried out to further support the interpretation of the experimental data.
The room temperature reactions with internal alkynes, RCîCR, of the µ-allenyl acetonitrile complex [Ru2Cp2(CO)2(NCMe){µ-η1:η2-C1HîC2îC3Me2}]BF4 (1-NCMe), freshly prepared from the tricarbonyl precursor [Ru2Cp2(CO)3{µ-η1:η2-C1HîC2îC3Me2}]BF4, 1, proceeded with alkyne insertion into ruthenium-allenyl bond and allenyl-CO coupling, affording compounds [Ru2Cp2(CO)2{µ-η2:η5-C(R)C(R)C1HC2(C3MeîCH2)C(OH)}]BF4 (R = Ph, 2; R = CO2Me, 3; R = CO2Et, 4) in 83-94% yields. Deprotonation of 2-4 by triethylamine gave [Ru2Cp2(CO)2{µ-η2:η5-C(R)C(R)CHC(CMeîCH2)C(O)}] (R = Ph, 5; R = CO2Me, 6; R = CO2Et, 7) in 75-88% yields, and 2-4 could be recovered upon HBF4·Et2O addition to 5-7. All the products, 2-7, were fully characterized by elemental analysis, IR and multinuclear NMR spectroscopy. The structure of 2 was ascertained by single crystal X-ray diffraction and investigated by DFT calculations, revealing a six-membered ruthenacycle with Shannon aromaticity index in line with related compounds. The formation of ruthenium-coordinated ruthenabenzenes from a preexistent diruthenium scaffold is a versatile but underdeveloped approach exploiting cooperative effects typical of a dimetallic core.
The µ-(amino)alkylidyne complex [Fe2Cp2(CO)2(µ-CO){µ-CNMe(CH2CHîCH2)}]CF3SO3, [1]CF3SO3, reacted with NBu4CN in dichloromethane affording the µ-(cyano)(amino)alkylidene [Fe2Cp2(CO)2(µ-CO){µ-C(CN)N(Me)(CH2CHîCH2)}], 2, in 91% yield. Decarbonylation of 2 by using Me3NO in acetone at room temperature yielded [Fe2Cp2(CO)(µ-CO){µ-κ3C-C(CN)N(Me)(CH2CHîCH2)}], 3, containing a multidentate alkylidene-alkene ligand occupying both a bridging site and a terminal site, in admixture with the µ-(amino)alkylidyne cyanide product [Fe2Cp2(CN)(CO)(µ-CO){µ-CN(Me)(CH2CHîCH2)}], 4. The reaction of the µ-(amino)alkylidyne imine complex [Fe2Cp2(CO)(µ-CO)(NHîCPh2){µ-CN(Me)(CH2CHîCH2)}]CF3SO3, [7]CF3SO3, with NBu4CN gave 3 with an optimized yield of 75% via imine elimination. According to DFT calculations, 3 is less stable than its geometric isomer 4 by 13.4 kcal mol-1 and quantitative conversion to 4 was achieved by refluxing a THF solution of 3 for 2 hours. No replacement of alkene coordination occurred upon treating 3 with CO or PPh3. The previously unknown compounds 2, 3, 4 and [7]CF3SO3 were fully characterized by analytical and spectroscopic techniques and the structure of 3 was elucidated by single crystal X-ray diffraction.
The elusive mono-hydride tri-anion [HRu4(CO)12]3- (4) has been isolated and fully characterized for the first time. Cluster 4 can be obtained by the deprotonation of [H3Ru4(CO)12]- (2) with NaOH in DMSO. A more convenient synthesis is represented by the reaction of [HRu3(CO)11]- (6) with an excess of NaOH in DMSO. The molecular structure of 4 has been determined by single-crystal X-ray diffraction (SC-XRD) as the [NEt4]3[4] salt. It displays a tetrahedral structure of pseudo C3v symmetry with the unique hydride ligand capping a triangular Ru3 face. Variable temperature (VT) 1H and 13C{1H} NMR experiments indicate that 4 is fluxional in solution and reveal an equilibrium between the C3v isomer found in the solid state and a second isomer with Cs symmetry. Protonation-deprotonation reactions inter-converting H4Ru4(CO)12 (1), [H3Ru4(CO)12]- (2), [H2Ru4(CO)12]2- (3), [HRu4(CO)12]3- (4) and the purported [Ru4(CO)12]4- (5) have been monitored by IR and 1H NMR spectroscopy. Whilst attempting the optimization of the synthesis of 4, crystals of [NEt4]2[Ru3(CO)9(CO3)] ([NEt4]2[7]) were obtained. Anion 7 contains an unprecedented CO32- ion bonded to a zero-valent Ru3(CO)9 fragment. Finally, the reaction of 6 as the [N(PPh3)2]+ ([PPN]+) salt with NaOH in DMSO affords [Ru3(CO)9(NPPh3)]- (9) instead of 4. Computational DFT studies have been carried out in order to support experimental evidence and the location of the hydride ligands as well as to shed light on possible isomers.
We report a screening study aimed to assess for the first time the air- and water-stability and the biological potential of simple metal-carbamates. These molecular metallic species are based on elements belonging to the groups 4-5, 7-9 and 11, and tin, and are easily available from inexpensive reagents. Complexes [Ag(O2CNEt2)] (13-Ag) and [Au(O2CNMe2)(PPh3)] (14-Au) resulted substantially stable in aqueous media and exhibited a potent in vitro cytotoxicity. Especially 13-Ag revealed a significant selectivity against the A549 lung adenocarcinoma and the A2780 ovarian cancer cell lines with respect to the noncancerous HEK293 cell line. Generation of ROS (reactive oxygen species) and mitochondrial membrane depolarization were recognized for 13-Ag and 14-Au; notwithstanding, the cell death mechanism is different in the two cases: apoptosis and cell cycle arrest in G0/G1 phase for 13-Ag; necroptosis and cell cycle arrest in S phase for 14-Au. Both 13-Ag and 14-Au are endowed with antibacterial activity, which is relatively stronger for 13-Ag towards Gram negative and for 14-Au towards Gram positive strains, respectively.
Anti-Infective Agents , Carbamates , Coordination Complexes , Cytotoxins , Gold , Neoplasms/drug therapy , Silver , A549 Cells , Anti-Infective Agents/chemistry , Anti-Infective Agents/pharmacology , Apoptosis/drug effects , Carbamates/chemistry , Carbamates/pharmacology , Cell Cycle Checkpoints/drug effects , Coordination Complexes/chemistry , Coordination Complexes/pharmacology , Cytotoxins/chemistry , Cytotoxins/pharmacology , Gold/chemistry , Gold/pharmacology , HEK293 Cells , Humans , Necroptosis/drug effects , Neoplasms/metabolism , Silver/chemistry , Silver/pharmacology
Bright photoluminescent neutral complexes having general formula [Ln(tbtz)3] (Ln = Eu, Tb; tbtz = tris(benzotriazol-1-yl)borate) were obtained by reacting K[tbtz] with EuCl3 and TbCl3. The emissions in the visible range, related to the f-f transitions of the trivalent lanthanide ions, are observable upon excitation with wavelengths shorter than 350 nm. The most intense emission bands correspond to the 5D0 â 7F4 transition at 699 nm for the europium complex and to the 5D4 â 7F5 transition at 542 nm for the terbium derivative. The luminescence is in all the cases mostly associated with the antenna-effect from the coordinated tbtz ligands. The synthetic approach was successfully extended to the preparation of the analogous yttrium and gadolinium derivatives. Tricapped trigonal prismatic geometry was attributed to the complexes on the basis of luminescence data and DFT calculations. Highly photoluminescent plastic materials were obtained by embedding small amounts of [Eu(tbtz)3] or [Tb(tbtz)3] in poly(methyl methacrylate).
The direct reactions of homometallic [Ni6(CO)12]2- and [Pt6(CO)12]2- Chini carbonyl clusters result in heterometallic Ni-Pt Chini-type clusters of the general formula [Pt6-xNix(CO)12]2- (x = 0-6). Their molecular structures have been determined by single-crystal X-ray diffraction (SC-XRD), showing a common octahedral (staggered, D3d) structure analogous to that of [Ni6(CO)12]2-, whereas [Pt6(CO)12]2- displays a trigonal-prismatic (eclipsed, D3h) structure. This structural change after replacing one single Pt with Ni may be classified as an alloying effect, and it has been theoretically investigated by DFT methods. Spectroscopic (IR and 195Pt and 13C NMR) and ESI-MS studies indicate that mixtures of [Pt6-xNix(CO)12]2- (x = 0-6) clusters are actually present in solution, whose compositions may be varied in an almost continuous way. Thus, they may be viewed as random alloy clusters whose overall compositions depend on the stoichiometry of the reagents.
Reductive carbonylation of RuCl3·3H2O at CO-atmospheric pressure results in the [H3Ru4(CO)12]- (1) polyhydride carbonyl cluster. The one-pot synthesis involves the following steps: heating RuCl3·3H2O at 80 °C in 2-ethoxyethanol for 2 h, addition of three equivalents of KOH, heating at 135 °C for 2 h, addition of a fourth equivalent of KOH and heating at 135 °C for 1 h. The resulting K[1] salt is transformed into [NEt4][1] upon metathesis with [NEt4]Br in H2O. The IR, 1H and 13C{1H} NMR spectroscopic data are in agreement with those reported in the literature. [Ru8(CO)16(X)4(CO3)4]4- (X = Cl, Br, I; 2-X) is formed as a by-product during the synthesis of 1, and the two compounds are separated on the basis of their different solubilities in organic solvents. The nature of the halide of 2-X depends on the [NEt4]X salt used for metathesis. 2-Br is transformed into [Ru10(CO)20(Br)4(CO3)4]2- (3) upon reaction with an excess of HBF4·Et2O. 1 is readily deprotonated by strong bases affording the previously known [H2Ru4(CO)12]2- (4). The reaction of 1 with [Cu(MeCN)4][BF4] affords [H3Ru4(CO)12(CuMeCN)] (7), whereas [H2Ru4(CO)12(CuBr)2]2- (8) is obtained from the reaction of 4 with [Cu(MeCN)4][BF4]/[NEt4]Br. All the compounds have been spectroscopically characterized, their molecular structures determined by single crystal X-ray diffraction (SC-XRD) and investigated using DFT methods in selected cases in order to confirm the hydride positions and to study the relative stability of possible isomers.
The catalytic potential of ammonium halide salts was explored in the coupling reaction of a model aziridine with carbon dioxide, highlighting the superior activity of [NH2Et2]I. Then, working at room temperature, atmospheric CO2 pressure and in the absence of solvent, the [NH2Et2]I-catalyzed synthesis of a series of 5-aryl-2-oxazolidinones was accomplished in good to high yields and excellent selectivity, from 2-aryl-aziridines with N-methyl or N-ethyl groups. NMR studies and DFT calculations outlined the pivotal role of both the diethylammonium cation and the iodide anion. The proposed method represents a convenient choice for obtaining a limited number of valuable molecules for which more complex and more expensive catalytic systems have been reported even in recent years.
Manganese(ii) halide complexes with N,N,N',N'-tetramethyl-P-naphtalen-2-ylphosphonic diamide were synthesized from anhydrous MnX2 salts (X = Cl, Br, I) and characterized. Single-crystal X-ray diffraction revealed in all the cases slightly distorted tetrahedral geometry of the coordination sphere. The photoluminescence spectra showed the superimposition of a green emission, related to the 4T1(4G) â 6A1(6S) transition of Mn(ii), with a band in the red range. Different possible attributions to the lowest-energy emission were taken into account. The emission spectra of the isolated products are dependent upon the nature of the halide and, in the case of X = Br, also upon the excitation wavelength.
