Synthesis, structure, and formation mechanism of the halogen-bridged tricobalt clusters, [Co3Cp3(μ3-CPh)2(μ-X)] (X=Cl, Br, and I)

Reactions of a benzylidyne-capped tricobalt cluster, [Co₃Cp₃(μ₃-CPh)₂] (1), with halogens (X₂ = Cl₂, Br₂, and I₂) in CH₂Cl₂ afforded halogen-adducts of 1. The structure of four isolated salts [Co₃Cp₃(μ₃-CPh)₂(μ-Cl)]PF₆ · MeCN (2PF₆ · MeCN), [Co₃Cp₃(μ₃-CPh)₂(μ-Br)]SbF₆ (3SbF₆), [Co₃Cp₃(μ₃-CPh)₂(μ-I)]SbF₆ · CH₂Cl₂ (4SbF₆ · CH₂Cl₂), and [Co₃Cp₃(μ₃-CPh)₂(μ-I)]I₃ (4I₃) determined by X-ray diffraction can be regarded formally as halide-adducts of 1²⁺. The halogen atom in each structure lies in the Co₃ plane. The halogen-bridged Co-Co edge was elongated (in 2PF₆ · MeCN = 2.6072(4), in 3SbF₆ = 2.6106(7), in 4SbF₆ · CH₂Cl₂ = 2.622(2), and in 4I₃=2.6718(9) Å), and the Co-Co distances that had no halogen-bridge remained unchanged from the Co-Co distance of 1 (2.382(8) Å), (in 2PF₆=2.4037(8) and 2.3948(7), in 3SbF₆=2.3888(6) and 2.4017(7), in 4SbF₆ · CH₂Cl₂ = 2.393(2) and 2.388(1), and in 4I₃ = 2.397(1) and 2.3868(9) Å). The UV-Vis absorption spectra of 2⁺, 3⁺, and 4⁺ had characteristic absorption peaks at 796, 819, and 844 nm, respectively. Cyclic voltammograms of 2PF₆ in CH₂Cl₂ with 0.1 M ⁿBu₄NPF₆ as the supporting electrolyte showed a chemically reversible oxidation (at a potential of 0.75 V versus Fc/Fc⁺), and an irreversible reduction wave at −0.57 V. The irreversible reduction resulted in the recovery of 1. The redox properties of 3⁺ and 4⁺ are very similar to that of 2⁺. Cyclic voltammetry of 1 in 0.1 M ⁿBu₄NCl/MeCN indicates that the formation of 2⁺ is a multi-step reaction. Initially, 1 is oxidized to 1⁺, and then, 1⁺ is coordinated by Cl⁻ followed by immediate oxidation to 2⁺.     

Mixed metal cyanide complexes derived from the CpCo(CN)3 anion

Reaction of the salt KCpCo(CN)₃ (1) with zinc iodide leads to the formation of a highly insoluble Co(III)/Zn(II) polymeric chain. However, pyridine was found to disrupt the aggregate that is formed to yield a crystalline trimetallic complex consisting of two CpCo(CN)₃ anions bridging a Zn(py)₄ dication through the cyanide ligands, [CpCo(CN)₂(μ-CN)]₂Zn(py)₄ (2). Along these same lines, reaction of CpCo(CN)₂PPh₃ (3) with AlCl₃ or CoCl₂ leads to the formation of a highly crystalline Co(II)/Co(III) diamond, [CpCo(PPh₃)(μ-CN)₂CoCl₂]₂ (4). Molecular structures of 1, 2, 3 and 4 were determined by single-crystal X-ray crystallography.     

Syntheses and molecular structures of 6-halogeno-pyridin-2-olate complexes with the diruthenium(2+) core

The complexes [Ru₂(CO)₅(μ-FpyO)₂]₂ (1), [Ru₂(CO)₄(μ-ClpyO)₂]₂ (2), and [Ru₂(CO)₄(μ-BrpyO)₂]₂ (3) were prepared from Ru₃(CO)₁₂ and 6-fluoro-2-hydroxypyridine (FpyOH), 6-chloro-2-hydroxypyridine (ClpyOH) and 6-bromo-2-hydroxypyridine (BrpyOH), respectively, in hot toluene. Compounds 1-3 are coordination dimers with a cyclo-RuORuO motif. By carrying out the reaction in hot methanol, the dinuclear complexes [Ru₂(CO)₄(μ-ClpyO)₂(CH₃OH)] (4) and [Ru₂(CO)₄(μ-BrpyO)₂(CH₃OH)] (5), respectively, were obtained. Treatment of 2 and 3 with triphenylphosphane provided the complexes [Ru₂(CO)₄(μ-ClpyO)₂(PPh₃)] (6) and [Ru₂(CO)₄(μ-BrpyO)₂(PPh₃)] (7), respectively. The solid-state structures of complexes 1, 2, 4, 6, and 7 were determined by single crystal X-ray diffraction. In all cases, a head-head coordination of the two 6-halopyridinolate ligands at the core was found. In all chlorine- or bromine-containing complexes, the axial coordination site at the ruthenium atom neighbored by two Cl or Br atoms remains unoccupied due to steric shielding by the halogen atom. In the fluoropyridinolate complex 1, the same coordination site is occupied by a carbonyl ligand.     

Preferential azido bridging regulating the structural aspects in cobalt(III) and copper(II)-Schiff base complexes: Syntheses, magnetostructural correlations and catalytic studies

A tridentate NNO donor Schiff base ligand [(1Z,3E)-3-((pyridin-2-yl)methylimino)-1-phenylbut-1-en-1-ol = LH] in presence of azide ions coordinates with cobalt(II) and copper(II) ions giving rise to three new coordination complexes [Co₂(L)₂(μ_1,1-N₃)₂(N₃)₂] (1), [Cu₂(L)₂(μ_1,3-N₃)]·ClO₄ (2) and [(μ_1,1-N₃)₂Cu₅(μ-OL)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂]_n (3). The complexes have been characterized by elemental analysis, FT-IR, UV-Vis spectral studies, and single crystal X-ray diffraction studies. These complexes demonstrate that under different synthetic conditions the azide ions and the Schiff base ligand (LH) show different coordination modes with cobalt(II) and copper(II) ions, giving rise to unusual dinuclear and polynuclear species (1, 2 and 3) whose structural variations are discussed. Magneto-structural correlation for the very rare singly μ_1,3-N₃ bridged Cu^II-Schiff base dinuclear species (2) has been studied. In addition, the catalytic properties of 1 for alkene oxidation and the general catalase-like activity behavior of 2 have been discussed.     

Synthesis, characterization and electrocatalysis of diiron propanediselenolate derivatives as the active site models of [FeFe]-hydrogenases

As an extension of our study on the H-cluster model compounds, a series of diiron propanediselenolate (PDS)-type models have been successfully synthesized. Reaction of diselenol HSe(CH₂)₃SeH with Fe₃(CO)₁₂ in THF (tetrahydrofuran) at reflux gave the parent model compound [μ-Se(CH₂)₃Se-μ]Fe₂(CO)₆ (1) in 48% yield. Further reaction of 1 with PPh₃ or PPh₂H in the presence of Me₃NO in MeCN at room temperature afforded the phosphine-monosubstituted model compounds [μ-Se(CH₂)₃Se-μ]Fe₂(CO)₅(L) (2, L = PPh₃; 3, L = PPh₂H) in 76% and 68% yields, respectively. Similarly, the N-heterocyclic carbene I_Mes-monosubstituted model compound [μ-Se(CH₂)₃Se-μ]Fe₂(CO)₅(I_Mes) (4) could be prepared in 46% yield by reaction of imidazolium salt I_Mes · HCl with n-BuLi followed by treatment of the resulting I_Mes ligand with 1 in THF at room temperature. Compounds 1-4 were fully characterized by elemental analysis and various spectroscopic methods. While the structures of 1-4 were further confirmed by X-ray crystallography, the comparative study of 1 and its analog [μ-S(CH₂)₃S-μ]Fe₂(CO)₆ demonstrates that 1 is a better catalyst for TsOH proton reduction to hydrogen under electrochemical conditions.     

Electronic structure of a benzylidyne-capped tricobalt cluster, [Co3Cp3(μ3-CPh)2]. X-ray structures and H NMR paramagnetic shifts of its cation and DFT calculations of its model complex

The cationic tricobalt cluster [Co₃Cp₃(μ₃-CPh)₂]⁺ (1⁺) was synthesized by the electrochemical oxidation of [Co₃Cp₃(μ₃-CPh)₂] (1). A large structural change was observed not only in the Co-Co, but also in the Co-C(cap) bonds upon oxidation of 1 to 1ClO₄. ¹H NMR paramagnetic shifts of this salt were measured in CD₂Cl₂. The π spin density on each sp² carbon atom was estimated to be 0.0089 (o-Ph), −0.0012 (m-Ph), 0.0087 (p-Ph), and 0.0053 (Cp). These values on the phenyl carbon atoms are similar to ca. 1/25 of those of the benzyl radical. It indicates that there is significant spin density on the capping carbon atom, which is delocalized onto the benzylidyne groups from the Co₃C₂ oxidation center by π conjugation between them. These results are consistent with the e^′′ (in the idealized D_3h symmetry) singly occupied molecular orbital (SOMO) of 1⁺, and are reproduced by B3LYP-DFT calculations of a model complex, [Co₃Cp₃(μ₃-CH)₂] (2), and its cation.     

New examples of μ-η:η-disulfido dicopper(II,II) complexes with bis(tetramethylguanidine) ligands

The new ligand N,N′-(2-methyl-2-(2-pyridyl)propan-1,3-diyl)bis(tetramethylguanidine) (L) and its four-coordinate, distorted square-planar copper(II) complex [CuLCl₂] (1) were synthesized and structurally characterized. Similarly, bis(μ-OH)dicopper(II,II) complex [Cu₂L₂(OH)₂](OTf)₂ (2) was synthesized and structurally characterized. The pyridyl group in L does not coordinate in either 1 or 2. New examples of μ-η²:η²-disulfido dicopper(II,II) complexes were synthesized by treating a copper(I) complex of either L or L′ [L′ = 2′,2′-(propane-1,3-diyl)bis(1,1,3,3-tetramethylguanidine)] with elemental sulfur. [Cu₂L₂(S₂)](PF₆)₂ (3) and [Cu₂(S₂)](PF₆)₂ (4) were both structurally characterized, and both structures have two copper(II) ions bridged by a disulfido ligand in a μ-η²:η²-manner. The ligands L and L′ coordinate in a bidentate fashion (like 1 and 2, the pyridyl ring does not coordinate in 3), and the geometry around the copper ions in 3 and 4 is distorted square planar. The metrical parameters of 3 and 4 were found to be similar to other μ-η²:η²-disulfido dicopper(II,II) complexes, and the Cu-S and Cu···Cu distances are among the shortest reported for this class of copper disulfide dimers.     

6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The dinuclear bis(6-X-pyridin-2-olato) ruthenium complexes [Ru₂(μ-XpyO)₂(CO)₄(PPh₃)₂] (X = Cl (4B) and Br (5B)), [Ru₂(μ-XpyO)₂(CO)₄(CH₃CN)₂] (X = Cl (6B), Br (7B) and F (8B)) and [Ru₂(μ-ClpyO)₂(CO)₄(PhCN)₂] (9B) were prepared from the corresponding tetranuclear coordination dimers [Ru₂(μ-XpyO)₂(CO)₄]₂ (1: X = Cl; 2: X = Br) and [Ru₂(μ-FpyO)₂(CO)₆]₂ (3) by treatment with an excess of triphenylphosphane, acetonitrile and benzonitrile, respectively. In the solid state, complexes 4B-9B all have a head-to-tail arrangement of the two pyridonate ligands, as evidenced by X-ray crystal structure analyses of 4B, 6B and 9B, in contrast to the head-to-head arrangement in the precursors 1-3. A temperature- and solvent-dependent equilibrium between the yellow head-to-tail complexes and the red head-to-head complexes 4A-7A and 9A, bearing an axial ligand only at the O,O-substituted ruthenium atom, exists in solution and was studied by NMR spectroscopy. Full ¹H and ¹³C NMR assignments were made in each case. Treatment of 1 and 2 with the N-heterocyclic carbene (NHC) 1-butyl-3-methylimidazolin-2-ylidene provided the complexes [Ru₂(μ-XpyO)₂(CO)₄(NHC)], X = Cl (11A) or Br (12A). An XRD analysis revealed the head-to-head arrangement of the pyridonate ligands and axial coordination of the carbene ligand at the O,O-substituted ruthenium atom. The conversion of 11A and 12A into the corresponding head-to-tail complexes was not possible.     

Mononuclear and dinuclear model hydrolases of nickel and cobalt

Reaction between the dinuclear model hydrolases [M₂(μ-OAc)₂(OAc)₂(μ-H₂O)(tmen)₂]; M = Ni (1); M = Co (2) and trimethylsilyltrifluoromethanesulphonate (TMS-OTf) under identical reaction conditions gives the mononuclear complex [Ni(OAc)(H₂O)₂(tmen)][OTf] · H₂O (3) in the case of nickel and the dinuclear complex [Co₂(μ-OAc)₂(μ-H₂O)₂(tmen)₂][OTf]₂ (4) in the case of cobalt.Reaction of (3) with urea gives the previously reported [Ni(OAc)(urea)₂(tmen)][OTf] (5), whereas (4) gives [Co₂(OAc)₃(urea)(tmen)₂][OTf] (6) previously obtained by direct reaction of (2) with urea. Both (3) and (4) react with monohydroxamic acids (RHA) to give the dihydroxamate bridged dinuclear complexes [M₂(μ-OAc)(μ-RA)₂(tmen)₂][OTf]; M = Ni (7); M = Co (8) previously obtained by the reaction of (1) and (2) with RHA, illustrating the greater ability of hydroxamic acids to stabilize dinuclear complexes over that of urea by means of their bridging mode, and offering a possible explanation for the inhibiting effect of hydroxamic acids by means of their displacing bridging urea in a possible intermediate invoked in the action of urease.     

Synthesis, crystal structures and magnetic properties of the copper(II) complexes containing isophthalate anion as coligand

Two new dinuclear isophthalato-bridged copper(II) complexes [Cu₂(ntb)₂(μ-ipt)](ClO₄)₂·4CH₃OH·0.33H₂O (1), [Cu₂(bbma)₂(μ-ipt)(NO₃)(CH₃OH)]NO₃·CH₃OH (2) and one mononuclear complex [Cu(bbma)(ipt)(CH₃OH)_0.67(H₂O)_0.33]·2CH₃OH (3) containing tetradentate and tridentate poly-benzimidazole ligands were synthesized, where ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine and ipt is isophthalate dianion. All of the complexes were characterized by elemental analysis, IR spectra and X-ray crystallography. The structures of complexes 1 and 2 consist of μ-ipt bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions of both compounds has a distorted square pyramidal geometry. The Cu···Cu distances are 9.142 and 10.435 Å for 1 and 2, respectively. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the bbma ligand, one isophthalate-oxygen atom and one oxygen atom from a coordinated methanol molecule. The magnetic susceptibility measurements at variable temperature over the 2-300 K range for complexes 1 and 2 are reported, with J values to be −0.013 and −0.32 cm⁻¹, respectively. The results show that the two complexes exhibit very weak antiferromagnetic interactions between the dinuclear copper(II) centers.     

Synthesis of new organotitanium (IV) complexes Cp2Ti(SeR)2 and Cp2TiCl(SeR) via tandem reactions involving `Cp2Ti' intermediate. Crystal structures of Cp2TiCl(SeR) (R=p-ClC6H4, p-BrC6H4)

A simple and convenient route for synthesizing organotitanium (IV) complexes with a general formula Cp₂Ti(SeR)₂ or Cp₂TiCl(SeR) has been developed. This synthetic route includes reduction of Cp₂TiCl₂ with Mg and an in situ treatment of the intermediate `Cp₂Ti' with diselenides RSeSeR. Interestingly, while the route involving reaction of Cp₂TiCl₂, Mg and RSeSeR in a molar ratio of 1:1:1 produced Cp₂Ti(SeR)₂, (1-5, R=α-C₁₀H₇, o-MeC₆H₄, m-MeC₆H₄, p-ClC₆H₄, p-BrC₆H₄) in 91-97% yields, the route involving reaction of Cp₂TiCl₂, Mg and RSeSeR in a molar ratio of 1: 0.5: 0.5 afforded Cp₂TiCl(SeR) (6-7, R=p-ClC₆H₄, p-BrC₆H₄) in 70% and 92% yields, respectively. 1-7 are new and have been characterized by elemental analysis and spectroscopy, as well as by X-ray diffraction analysis for 6 and 7. A possible pathway for production of these two types of organotitanium (IV) complexes, mainly depending upon the molar ratio of the starting materials, are briefly discussed.     

Synthesis, characterization and structural diversity of lanthanide chlorides supported by the β-diketiminate ligand [{(2,6-Me2C6H3)NC(Me)}2CH]

Reactions of the β-diketiminate lithium salt L²Li [L²={(2,6-Me₂C₆H₃)NC(Me)}₂CH] with anhydrous LnCl₃ (Ln=Yb, Sm, Nd) in 1:1 molar ratio in THF afforded the new β-diketiminate lanthanide complexes L²LnCl(THF)(μ-Cl)₂Li(THF)₂ (Ln=Yb (1), Sm (2), Nd (3)). Recrystallization of complexes 1-3 from toluene gave the neutral complexes L²LnCl₂(THF)₂ (Ln=Yb (4), Sm (5), Nd (6)). Recrystallization of complexes 4 and 5 in hot toluene for two times gave the dinuclear complexes L²ClLn(μ-Cl)₃LnL²(THF) (Ln=Yb (7), Sm (8)). Treatment of the mother liquor of complex 2 in hot toluene for three times gave the novel trinuclear complex L²SmCl(μ-Cl)₃SmL²(μ-Cl)Li(L²H)(THF) (9). Each of these complexes was well characterized, while complexes 3, 7 and 9 have been characterized by X-ray diffraction structure determination.     

New pyridyl modified phosphines: Synthesis and late transition-metal coordination studies

Using a phosphorus based Mannich condensation reaction the new pyridylphosphines {5-Ph₂PCH₂N(H)}C₅H₃(2-Cl)N (1-Cl) and {2-Ph₂PCH₂N(H)}C₅H₃(5-Br)N (1-Br) have been synthesised in good yields (60% and 88%, respectively) from Ph₂PCH₂OH and the appropriate aminopyridine. The ligands 1-Cl and 1-Br display variable coordination modes depending on the choice of late transition-metal complex used. Hence P-monodentate coordination has been observed for the mononuclear complexes AuCl(1-Cl) (2), AuCl(1-Br) (3), RuCl₂(p-cymene)(1-Cl) (4), RuCl₂(p-cymene)(1-Br) (5), RhCl₂(Cp^∗)(1-Cl) (6), RhCl₂(Cp^∗)(1-Br) (7), IrCl₂(Cp^∗)(1-Cl) (8), IrCl₂(Cp^∗)(1′-Cl) (8′), IrCl₂(Cp^∗)(1-Br) (9), cis-/trans-PdCl₂(1-Cl)₂ (10), cis-/trans-PdCl₂(1-Br)₂ (11), cis-PtCl₂(1-Cl)₂ (12) and cis-PtCl₂(1-Br)₂ (13). Reaction of Pd(Me)Cl(cod) (cod = cycloocta-1,5-diene) with either 1 equiv. of 1-Br or the known pyridylphosphines 1′-Cl, 1-OH or 1-H gave the P/N-chelate complexes Pd(Me)Cl(1-Br-1-H) (14)-(17). All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 4, 5, 10 and 16 · (CH₃)₂SO have been elucidated by single crystal X-ray crystallography. A crystal structure of the dinuclear metallocycle trans,trans-[PdCl₂{μ-P/N-{Ph₂PCH₂N(H)}C₅H₄N}]₂ · CHCl₃, 18 · CHCl₃, has also been determined. Here 1-H bridges, using both P and pyridyl N donors, two dichloropalladium centres affording a 12-membered ring with the PdCl₂ units adopting a head-to-tail arrangement.     

Titanocene complexes with nonlinear pseudohalide ligands: Synthesis, spectroscopic characterization and crystal structure

Binuclear titanocene complexes [Cp₂Ti(tcm)]₂O (4), [Cp₂Ti(dca)]₂O (5) and [Cp₂Ti(dcnm)]₂O (6) (tcm⁻ = tricyanomethanide, dca⁻ = dicyanamide and dcnm⁻ = dicyanonitrosomethanide) were synthesized in moderate yields by the reaction of Cp₂TiCl₂ (1) with respective alkali metal pseudohalide salts in the aqueous solution. When the reaction was carried out in dry organic solvents, mononuclear compounds Cp₂Ti(tcm)₂ (2) and Cp₂Ti(dca)₂ (3) were isolated. Preparation of dipseudohalide complex Cp₂Ti(dcnm)₂ by this manner was unsuccessful due to decomposition of dcnm ligand resulting in formation of oxygen-bridged compound 6. All prepared compounds were characterized by elemental analysis, NMR, Raman, infrared and UV-Vis spectroscopy. Molecular structures of 2, 4 and 6 (two polymorphs) have been determined by single-crystal X-ray diffraction analysis.     

Chalcogenide-capped triruthenium clusters: X-ray structures of [Ru3(CO)6(μ3-CO){P(C4H3S)3}(μ-dppm)(μ3-O)] and [(μ-H)2Ru3(CO)6{P(C4H3S)3}(μ-dppm)(μ3-S)]

Treatment of [Ru₃(CO)₉{P(C₄H₃S)₃}(μ-dppm)] (1) [dppm = bis(diphenylphosphino)methane] with molecular oxygen in benzene at 60 °C affords oxo-capped [Ru₃(CO)₆(μ₃-CO){P(C₄H₃S)₃}(μ-dppm)(μ₃-O)] (2), while with elemental sulfur and selenium related chalcogenide-capped clusters [Ru₃(CO)₆(μ₃-CO){P(C₄H₃S)₃}(μ-dppm)(μ₃-E)] (3, E = S; 5, E = Se) and bis(chalcogenide) clusters [Ru₃(CO)₆{P(C₄H₃S)₃}(μ-dppm)(μ₃-E)₂] (4, E = S; 6, E = Se) result. Reaction of 1 with H₂S in refluxing THF affords the previously reported [(μ-H)₂Ru₃(CO)₇(μ-dppm)(μ₃-S)] (7) together with the new sulfido-capped dihydride [(μ-H)₂Ru₃(CO)₆{P(C₄H₃S)₃}(μ-dppm)(μ₃-S)] (8). All new compounds have been characterized by spectroscopic data, and 2 and 8 by single-crystal X-ray diffraction analyses. Oxo-capped 2 consists of a triangular ruthenium framework capped on opposite sides by oxo and carbonyl groups, while 8 consists of a ruthenium triangle by a capping sulfido ligand and two inequivalent bridging hydride ligands.     

Metal-organic open frameworks with one-dimension channels assembled with pyridine 2,6-dicarboxylic acid and N-containing auxiliary ligands: Syntheses, crystal structures, and physical characterization

Four new complexes, {[Mn(imH)₂(pdc)]·H₂O}_n (1), [Zn₂(pdc)₂(H₂O)₅]·2H₂O (2), [Zn(imH)₂(pdc)]·H₂O (3), {[Zn₂(pdc)₂(bpy)(H₂O)₂]·5H₂O}_n (4) [imH = imidazole pdc = pyridine 2,6-dicarboxylate, bpy = 4,4′-bipyridine] have been synthesized under hydrothermal conditions and structurally characterized by elemental analysis, IR, PXRD, single-crystal X-ray diffraction and thermogravimetric analyses. All the four complexes display a three-dimensional (3D) open framework with one-dimensional (1D) channels that are filled with lattice water molecules. Particularly, in 4, the lattice water molecules form an infinite water chain. Both 1 and 4 consist of 1D polymeric chains. While 2 contains a dinuclear Zn(II) unit, and 3 is a mononuclear complex. Further, the result of thermal analysis of 1 and 2 shows the robustness of the overall supramolecular three-dimensional architecture. Complexes 1, 3, and 4 exhibit strong fluorescent emissions in the solid state at room temperature and could be significant in the field of photoactive materials.     

Rectangular tetranuclear silver(I) and μ8-selenide-centered octanuclear copper(I) complexes containing bis(diphenylphosphino)amide ligands

Interaction of Ag(CF₃CO₂) with bis(diphenylphosphino)amide (dppa) in THF gave a tetranuclear Ag₄-coplanar silver(I) complex [Ag₄(μ-dppa)₂(μ₄-O₂PPh₂)₂(μ-CF₃CO₂)₂] (1). The trinuclear trigonal-bipyramid copper(I) complex [Cu₃(μ₃-Cl)₂(μ-dppa)₃][CuCl₂] (2) was obtained from the reaction of [CuCl] powder with bis(diphenylphosphino)amide (dppa) in THF. Treatment of 2 with (Me₃Si)₂Se in THF afforded a μ₈-selenide-centered octanuclear copper(I) complex [Cu₈(μ₈-Se)(μ₄-Se)(μ₄-SeH)₃(μ-dppa)₄][(Ph₂PO)₂N] (3). The structures of 1-3 were determined by single-crystal X-ray diffraction analyses. Complex 1 comprises a rectangular Ag₄ array with each edge bridged with a pair of μ-dppa, μ₄-O₂PPh₂ and μ-CF₃CO₂ ligands that are approximately perpendicular to each other. Complex 2 contains a trigonal-bipyramid [Cu₃(μ₃-Cl)₂]⁺ core surrounded by three μ-dppa ligands. The cationic complex in 3 consists of four [Cu₂(μ-dppa)] fragments side-capped by one μ₄-Se and three μ₄-SeH ligands and center-connected by a μ₈-Se atom.     

Tunable polymerization of silver complexes with organosulfur ligand: counterions effect, solvent- and temperature-dependence in the formation of silver(I)-thiolate(and/or thione) complexes

The reaction of pyridine-2-thiol with AgBF₄ and AgClO₄ in MeCN gave rise to polymeric compounds [{Ag(HPyS)₂}₂(BF₄)₂]_n (1) and [{Ag(HPyS)₂}₂(ClO₄)₂]_n (2) (HPyS=pyridine-2-thione), respectively, while the similar reaction of pyridine-2-thiol with AgNO₃ resulted in a polymeric compound [{Ag₄(HPyS)₆}(NO₃)₄]_n (3). X-ray single-crystal diffraction analyses showed that the cations of both 1 and 2 possess a single-metal-atom chain structure but that of 3 is a double-metal-atom chain structure. The difference between 1 (or 2) and 3 showed counterion effect in polymerization of silver-thione compounds. In the presence of water, the treatment of pyridine-2-thiol with AgBF₄ in DMF at 0 °C generated a polymeric compound [Ag(SPy)]_n (4) (Spy=pyridine-2-thiolate) with graphite-like layered array of silver ions. Compound 4 can convert into its isomer [Ag₆(SPy)₆]_n (5) through soaking in DMF for 1 month. However, the similar reaction of pyridine-2-thiol with AgBF₄ in MeCN-H₂O (v:v=40:1) at room temperature gave another layered polymeric compound [{Ag₅(Spy)₄(HPyS)}BF₄]_n (6). The preparation of 4, 5, and 6 showed that temperature and solvent exert influence on formation of silver-thiolate polymers. The reaction of AgNO₃ with K₂i-mnt (i-mnt=2,2-dicyanoethene-1,1,-dithiolate) and pyridine-2-thiol gave a polymer [Ag₄(μ₄-i-mnt)₂(μ-HPyS)₂(μ-HPyS)_4/2]_n (7) with one-dimensional (1-D) chain structure consisting of Ag₄ square planar cluster units linked by 1H-pyridine-2-thione ligand. The treatment of AgNO₃ with NaS₂CNEt₂ and pyridine-2-thiol in DMF resulted in another polymeric compound [Ag₄(μ₃-S₂CNEt₂)₂(μ₂-SPy)_4/2]_n (8). The preparation and characterization of these polymeric compounds demonstrated that polymerization of silver(I)-thione and silver(I)-thiolate complexes is tunable through controlling reaction conditions. Semiconducting property studies of 1-8 demonstrated that the electrical conductivity of 4 is 2.04×10⁻⁵ S cm⁻¹ at 25 °C and increases as temperature rises, and those of 1-3 and 5-8 are in the range of 1×10⁻¹²-1×10⁻¹⁵ S cm⁻¹ at room temperature and independent on the temperature, indicating that 1 is a semiconductor and the others are insulators.     

Synthesis and structural characterization of the mono- and diphosphine-containing diiron propanedithiolate complexes related to [FeFe]-hydrogenases. Biomimetic H2 evolution catalyzed by (mu-PDT)Fe2(CO)4[(Ph2P)2N(n-Pr)

As the new H-cluster models, six diiron propanedithiolate (PDT) complexes with mono- and diphosphine ligands have been prepared and structurally characterized. The monophosphine model complex (μ-PDT)Fe₂(CO)₅[Ph₂PNH(t-Bu)] (1) was prepared by reaction of parent complex (μ-PDT)Fe₂(CO)₆ (A) with 1 equiv of Ph₂PNH(t-Bu) in refluxing xylene, whereas A reacted with 1 equiv of Me₃NO · 2H₂O in MeCN at room temperature followed by 1 equiv of Ph₂PH to give the corresponding monophosphine model complex (μ-PDT)Fe₂(CO)₅(Ph₂PH) (2). Further treatment of 2 with 1 equiv of n-BuLi in THF at −78 °C followed by 1 equiv of CpFe(CO)₂I from −78 °C to room temperature afforded monophosphine model complex (μ-PDT)Fe₂(CO)₅[Ph₂PFe(CO)₂Cp] (3), whereas the diphosphine model complexes (μ-PDT)Fe₂(CO)₄(Ph₂PC₂H₄PPh₂) (4), (μ-PDT)Fe₂(CO)₄[(Ph₂P)₂N(n-Pr)] (5) and (μ-PDT)Fe₂(CO)₄[(Ph₂P)₂N(n-Bu)] (6) were obtained by reactions of A with ca.1 equiv of the corresponding diphosphines in refluxing xylene. All the new model complexes were characterized by elemental analysis, spectroscopy and particularly for 1 and 3-6 by X-ray crystallography. On the basis of electrochemical and spectroelectrochemical studies, model 5 was found to be a catalyst for HOAc proton reduction to H₂, and for this electrocatalytic reaction an ECCE mechanism was proposed.     

Synthesis of σ-π-phosphinidene sulfide complexes [Mn2(CO)n(μ-η,η-P(NR2)S)] (n = 8, 9) via direct sulfuration of electrophilic μ-phosphinidenes and photochemical transformation to a trigonal prismatic Mn2P2S2 cluster

The μ-phosphinidene complexes [Mn₂(CO)₈{μ-P(TMP)}] (1) (TMP = tetramethylpiperidyl) and [Mn₂(CO)₈{μ-P(NⁱPr₂)}] (2) react with elemental sulfur to form rare phosphinidene sulfide complexes [Mn₂(CO)₉{μ-η¹,η²-P(TMP)S}] (3) and [Mn₂(CO)₈{μ-η¹,η²-P(NⁱPr₂)S}] (4), respectively. Photolysis of 3 results in the unprecedented conversion to [Mn₂(CO)₆(μ-{κPκ²S}₂-(TMP)(S)P-P(S)(TMP)] (5), which contains a novel 10-electron donor diphosphene disulfide ligand (TMP)(S)P-P(S)(TMP).