Os(CO)2(η-SC5H4N(O))(η-SC5H4N): structural evidence for the transformation of pyridine-2-thione N-oxide to pyridine-2-thiolate in osmium complexes

The reaction of Os₃(CO)₁₂ with an excess of 1-hydroxypyridine-2-thione and Me₃NO gives three mononuclear osmium complexes Os(CO)₂(η²-SC₅H₄N(O))₂ (1), Os(CO)₂(η²-SC₅H₄N(O))(η²-SC₅H₄N) (2), and Os(CO)₂(η²-SC₅H₄N)₂ (3). The results of single-crystal X-ray analyses reveal that complex 1 contains two O,S-chelate pyridine-2-thione N-oxide (PyOS) ligands, whereas complex 2 contains one O,S-chelate PyOS and one N,S-chelate pyridine-2-thiolate group. The unique structure of 2 provides evidence of the pathway for this transformation. When this reaction was monitored by ¹H NMR spectroscopy the triosmium complexes Os₃(CO)₁₀(μ-H)(μ-η¹-S-C₅H₄N(O)) (4) and Os₃(CO)₉(μ-H)(μ-η¹:η²-SC₅H₄N(O)) (5) were identified as intermediates in the formation of the mononuclear final products 1-3. The proposed pathway is further supported by the observation of several dinuclear osmium intermediates by electrospray ionization mass spectrometry. In addition, the reaction of Os₃(CO)₁₂ with 1-hydroxypyridine-2-thione in the absence of Me₃NO at 90 °C generated mononuclear complex 2 as the major product along with smaller amounts of complexes 1 and 3. These results suggest that the N-oxide facilitates the decarbonylation reaction. Crystal data for 1: monoclinic, space group C2/c, a = 26.9990(5) Å, b = 7.6230(7) Å, c = 14.2980(13) Å, β = 101.620(2)°, V = 2882.4(4) ų, Z = 8. Crystal data for 2: monoclinic, space group C2/c, a = 5.7884(3) Å, b = 13.9667(7) Å, c = 17.2575(9) Å, β = 96.686(1)°, V = 1385.69(12) ų, Z = 4.     

Synthesis,structural characterization and properties of one-dimensional coordination polymers of cobalt(II)- and nickel(II)-phosphonate complexes with 2,2′-bipyridine as a secondary ligand component: Observation of both cis and trans conformations of a diphosphonic acid

Two new isomorphous cobalt and nickel phosphonates [M^II(2,2′-bipy)₂LH₄]_n[LH₂]_n, M = Co (compound 1), M = Ni (compound 2) were hydrothermally synthesized from p-xylylenediphosphonic acid (LH₄) and the corresponding metal salts with 2,2′-bipyridine as secondary ligand component. Both the compounds 1 and 2 are characterized by routine elemental analyses, IR-, electronic-spectral analyses, thermogravimetric studies and unambiguously characterized by single crystal X-ray crystallography. The structures were refined in monoclinic space group C2/c. The crystal structure consists of 1D [M(2,2′-bipy)₂LH₄]²⁺ chains and [LH₂]²⁻ anions. The flexibility of non-rigid ligand p-xylylenediphosphonic acid (LH₄) tends to adopt a rare cis conformation in the crystal structure to meet the coordination requirement of the metal center from the usual trans conformation. The hydrogen bonding in the crystal structure leads to cylindrical tubes that extend via p-xylylenediphosphonic acid resulting in a 2D supramolecular sheet throughout the crystal. Compounds 1 and 2 are additionally characterized by thermogravimetric studies.     

Dioxomolybdenum(VI) complexes containing N-heterocyclic carbenes

Compound MoO₂Cl₂(THF)₂ reacts with two equivalents of 1,3-dialkyl substituted 4,5-dimethylimidazol-2-ylidenes to give the dioxomolybdenum(VI) complexes MoO₂Cl₂(L^R)₂ [R = Me (1), i-Pr (2)]. Treatment of MoO₂Cl₂(THF)₂ with one equivalent of the N-heterocyclic carbenes L^Me, L^i-Pr and ^C1L^n-Bu (L^Me = 1,3,4,5-tetramethylimidazol-2-ylidene, L^i-Pr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, and ^C1L^n-Bu = 1,3-dibutyl-4,5-dichloroimidazol-2-ylidene) affords the monocarbene adducts MoO₂Cl₂(L^R) [R = Me (3), i-Pr (4)] and MoO₂Cl₂(^C1L^n-Bu) (5), respectively. Decomposition of complexes 1-5 affords a molybdenum oxychloride anion [Mo₂O₅Cl₄]²⁻ as an imidazolium salt.     

Synthesis and crystal structure of a new open-framework iron phosphate (NH4)4Fe3(OH)2F2[H3(PO4)4]: Novel linear trimer of corner-sharing Fe(III) octahedra

A new iron phosphate (NH₄)₄Fe₃(OH)₂F₂[H₃(PO₄)₄] has been synthesized hydrothermally at HF concentrations from 0.5 to 1.2 mL. Single-crystal X-ray diffraction analysis reveals its three-dimensional open-framework structure (monoclinic, space group P2₁/n (No. 14), a=6.2614(13) Å, b=9.844(2) Å, c=14.271(3) Å, β=92.11(1)°, V=879.0(3) Å³). This structure is built from isolated linear trimers of corner-sharing Fe(III) octahedra, which are linked by (PO₄) groups to form ten-membered-ring channels along [1 0 0]. This isolated, linear trimer of corner-sharing Fe(III) octahedra, [(FeO₄)₃(OH)₂F₂], is new and adds to the diverse linkages of Fe polyhedra as secondary building units in iron phosphates. The trivalent iron at octahedral sites for the title compound has been confirmed by synchrotron Fe K-edge XANES spectra and magnetic measurements. Magnetic measurements also show that this compound exhibit a strong antiferromagnetic exchange below T_N=17 K, consistent with superexchange interactions expected for the linear trimer of ferric octahedra with the Fe-F-Fe angle of 132.5°.     

Diverse coordination of two ligands in ferromagnetic [Cu(μ-HCO2)2(3-pyOH)]n and [Cu2(μ-HCO2)2(μ-3-pyOH)2(3-pyOH)2(HCO2)2]n

Two novel polynuclear complexes with methanoate anions and 3-hydroxypyridine ligands [Cu(μ-HCO₂)₂(3-pyOH)]_n (1) and [Cu₂(μ-HCO₂)₂(μ-3-pyOH)₂(3-pyOH)₂(HCO₂)₂]_n (2), respectively, were synthesized and characterized. The central copper atom in 1 is surrounded by four methanoates and a 3-pyOH molecule, forming a square-pyramidal CuO₃NO chromophore. All the methanoates are bidentate and serve as bridges between the adjacent copper ions via syn-anti and anti–anti coordination. The basal square coordination axes are formed by O(syn), N(3-pyOH) (1.974(2), 2.016(2) Å) and O(anti), O(anti) (1.945(2), 1.960(2) Å), while the third O(anti) (2.247(2) Å) is on the top of the pyramid. A ferromagnetic transition with an exchange constant 2J/k_B = 9.2 cm⁻¹ is found for 1 below 20 K. This interaction probably takes place through two syn-anti methanoates extended in a chain through the 2D structure. On the other hand, two monoatomic Cu–O–Cu intra-dinuclear asymmetric (1.986(2), 2.415(2) Å) bridges of two methanoates in [Cu₂(HCO₂)₄(3-pyOH)₄] (2) are present. An elongated distorted octahedral coordination sphere around each copper(II) atom is completed by an additional monodentate terminal methanoate (1.975(2) Å), two N-coordinated 3-pyOH (2.005(2), 2.002(2) Å) and the third weakly O-coordinated 3-pyOH (2.732(2) Å). Although a shorter Cu?Cu distance is noticed in 2 than in 1 (4.690(1) Å 1, 3.442(1) Å 2), much weaker ferromagnetism is found in 2.     

Synthesis,crystal structure and magnetic properties of a new dinuclear copper(II) amino acid complex [Cu2(l-arg)2(μ-HPO4-O)(μ-HPO4-O,O′)(μ-OH)] · (H3O) · (H2O)6

A novel dinuclear copper(II) complex with the amino acid l-arginine (l-arg), with mono and bidentate HPO₄²⁻ oxoanions and an OH⁻ anion. [Cu₂(l-arg)₂(μ-HPO₄-O)(μ-HPO₄-O,O′)(μ-OH)]⁻ · (H₃O)⁺ · 6H₂O (1) was prepared and its structure was determined by X-ray diffraction methods. The two independent copper ions are in a distorted square pyramidal coordination, each bonded to one l-arginine molecule. These two Cu(l-arg) units are bridged by two monoatomic equatorial–apical oxygen ligands belonging to a monodentate hydrogenphosphate group, and to the hydroxyl group. The copper ions in the dinuclear unit at d = 3.1948(8) Å are also connected by two equatorial oxygen belonging to a bidentate hydrogenphosphate. This dinuclear character and bridging scheme, not common for metal–amino acid compounds, is a consequence of the properties of the phosphate anions. The magnetic susceptibility at temperatures between 2 and 300 K and the isothermal magnetization curves at T = 2.29(1) K with applied fields up to 9 T were measured. The magnetic data indicate an antiferromagnetic intradinuclear exchange coupling J/k_B = −3.7(1) K and using a molecular field approximation we estimated a weaker ferromagnetic interaction J′/k_B ∼ 0.3 K between neighbour dinuclear units.     

Structure and redox behavior of Ru(II)-diene complexes

A series of Ru(acac)₂(η⁴-diene) complexes containing cis- and trans-diene coordination have been investigated by cyclic voltammetry to correlate structural bonding and conformation patterns of diene ligands with redox behaviors. The solid-state structure of Ru(acac)₂(2,3-dimethyl-1,3-butadiene) has been determined by single crystal X-ray diffraction methods. Ru(acac)₂(2,3-dimethyl-1,3-butadiene) crystallizes in the monoclinic space group C2/c with a = 12.368(2) Å, b = 17.0600(2) Å, c = 16.0110(2) Å, β = 98.4405(10)° and V = 3341.38(10) ų for Z = 8. A structural comparison between several Ru-trans-η⁴-diene complexes and Ru-η⁴-1,3-cyclohexadiene revealed no difference in the Ru-C(diene) bond distances. However, through cyclic voltammetry experiments these species demonstrated different redox behavior, as function of the coordinated diene ligand.     

Chiral self-assembly of triorganotin complexes: Syntheses, characterization, crystal structures and antitumor activity of organotin(IV) complexes containing (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid ligands

Six new chiral triorganotin(IV) complexes, {(R₃Sn)₂[C₃H₆(COO)₂]}_n (R = Me: 1; Bu: 2), {(R₃Sn)₂[C₄H₈(COO)₂]}_n (R = Me: 3; Bu: 4), and {(R₃Sn)₂[C₂H₄O(COO)₂]}_n (R = Me: 5; Bu: 6) have been prepared by treatment of (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid, with the corresponding R₃SnCl (R = Me, Bu) and sodium ethoxide in methanol. All the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and TGA. Except for 3, all of the complexes were also characterized by X-ray crystallography. The structural analyses reveal that complexes 1 and 5 have 2D network structures in which (R)-(+)-methylsuccinic acid and l-(−)-malic acid act as tetradentate ligands coordinated to trimethyltin(IV) ions. Complexes 2 and 4 have 3D metal-organic framework structures in which the deprotoned acids serve as tetradentate ligands. Complex 6 adopts a 1D zigzag chain structure and forms a 2D supramolecular framework through intermolecular C-H?O interactions. In addition, the antitumor activities of complexes 1-6 have been studied. We also have measured the specific rotation of the chiral dicarboxylic acids and the organotin derivatives.     

Four distinctive 1-D lanthanide carboxylate coordination polymers: Synthesis,crystal structures and spectral properties

Four novel lanthanide coordination polymers [Pr(mal)(OH)(bipy) · 2H₂O]_n (1), {[Dy¹(SBA)₃(H₂O)₂][Dy²(SBA)₃(H₂O)₂] · 4H₂O}_n (2), {[Tb(OHnic)(Onic)(H₂O)₅ · (OHnicH)] · H₂O}_n (3) and {[Sm(OHnic)(Onic)(H₂O)₅ · (OHnicH)] · H₂O}_n (4) (Hmal = maleic acid, HSBA = 4-sulfobenzoic acid, OHnicH = 6-hydroxynicotinic acid and bipy = 2,2′-bipyridine) have been synthesized and determined by single crystal X-ray diffraction. Complex 1 is a 1-D helical chain with seven-coordinated praseodymium centers. Complex 2 forms 1-D chain-like molecular structure containing two crystallographically unique dysprosium centers, the Dy¹ center is seven-coordinated while Dy² is eight-coordinated. The isomorphous complexes 3 and 4 exhibit an unprecedented 1-D chain-like polymeric structure through hydroxyl oxygen atoms of bridging Onic²⁻ anions linking up the neighboring central ions, and there exist three types of 6-OHnicH ligands in the structural unit which is rare for lanthanide carboxylate complexes. The photophysical properties of these complexes were studied using ultraviolet absorption spectra, fluorescence excitation and emission spectra.     

The phospha-Michael addition of dimethyl- and diphenylphosphites to the η-N-maleimidato ligand: Inhibition of serine hydrolases by half-sandwich metallocarbonyl azaphosphonates

Dialkyl- and diphenyl phosphites react with the (η⁵-C₅H₅)M(CO)_x(η¹-N-maleimidato) (M = Fe, Mo; x = 2 or 3) complexes giving products of the phospha-Michael addition to the η¹-N-maleimidato ligand. One of these complexes (M = Fe, x = 2) was characterized by X-ray diffraction. The synthesized metallocarbonyl azaphosphonates and the corresponding iron phosphonic acid act as inhibitors of certain serine hydrolases (AChE and BChE). The kinetic assays were performed and revealed that inhibition mechanism depends strongly on the enzyme and the structure of the inhibitor.     

Palladium nitrosyl carboxylate clusters: Synthesis and reactivity. X-ray structures of Pd4(μ-CO)2(μ-NO)(μ-RCO2)5 (R = Pr, Bu)

New palladium nitrosyl carboxylate complexes Pd₈(CO)_4−m(NO)_m(NO₂)₄(RCO₂)₈ (m = 2, 4) were obtained by the treatment of palladium carbonyl carboxylates clusters cyclo-Pd_n(μ-CO)_n(μ-RCO₂)_n (n = 6) (1) with gaseous nitrogen monoxide. These complexes are the products of CO substitution in early described Pd₈(CO)₄(NO₂)₄(RCO₂)₈ clusters. By adding an excess of corresponding acid to reaction mixture Pd₄(CO)₂(NO)(RCO₂)₅ complexes were obtained, their structures were determined by X-ray diffraction analysis. These clusters are intermediate products of transformation of 6-nuclear initial clusters into various 8-nuclear complexes. This fact demonstrates that carboxylate ligands can be used as stabilizers for intermediate unstable polynuclear palladium compounds.     

Synthesis and structures of CpFe(CO)2(κE-ECS2Ph) and [CpFe(CO)(κS,E-ECS2Ph)] (E = S,Se)

The iron trithiocarbonato complex CpFe(CO)₂(κS-SCS₂Ph) (1a) and its selenodithiocarbonato analogue CpFe(CO)₂(κSe-SeCS₂Ph) (1b) were generated by room temperature reactions of (μ-E_x)[CpFe(CO)₂]₂ (E = S; x = 2, 3. E = Se; x = 1) with PhSC(S)Cl. These compounds can be converted into the complexes CpFe(CO)(κ²S,E-ECS₂Ph) [E = S (2a), Se (2b)], in which the trithiocarbonato or the selenodithiocarbonato ligand is bonded to the iron in a chelate form, under photolytic conditions. The composition and structure of all products have been verified by elemental analyses, IR and ¹H NMR spectroscopies. The crystal structures for compounds 1a, 1b, and 2b show a three-legged piano-stool configuration at Fe in each complex. The spectroscopic and structural data in this work are commensurate with the electronic factor of the S- and Se-donor ligands.     

Novel platinum pyridinehydroxamic acid complexes: Synthesis,characterisation, X-ray crystallographic study and nitric oxide related properties

Herein, we describe the synthesis and characterisation of a novel class of Pt^II and Pt^IV pyridinehydroxamic acid (pyhaH) complexes of general formula cis-[Pt^IICl₂(x-pyhaH)₂] and cis-[Pt^IVCl₄(x-pyhaH)₂], respectively (where x = 3 or 4) in which the pyridinehydroxamic acid is coordinated to the platinum ion via the pyridine nitrogen only leaving the hydroxamic acid free to potentially release cytotoxic nitric oxide (NO). The crystal structure of the Pt^IV derivative, cis-[PtCl₄(4-pyhaH)₂] · 2CH₃OH is reported. To establish the biological effect of the uncoordinated hydroxamic acid moiety in the Pt^II compounds synthesised, the corresponding pyridinecarboxylic acid (pycaH) complexes of general formula cis-[Pt^IICl₂(x-pycaH)₂] (where x = 3 or 4) and the Pt^II pyridine (py) complex, cis-[Pt^IICl₂(py)₂] were synthesised and served as reference standards. The NO-releasing properties of each of the Pt^II compounds, the pyhaH and the pycaH ligands were studied. The Pt^II pyridinehydroxamic acid derivatives were found to induce potent in vitro effects attributable to either NO-release from the hydroxamic acid moiety and/or stimulation of inducible nitric oxide synthase of endothelial cells.     

X-ray structure and multinuclear NMR studies of platinum(II) complexes with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one

New dichloride platinum(II) complexes with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) have been synthesized and characterized by thermal analysis, infrared and ¹H, ¹³C, ¹⁵N, ¹⁹⁵Pt NMR spectroscopy. X-ray crystal structures of cis-PtCl₂(NH₃)(HmtpO) (1) and cis-PtCl₂(HmtpO)₂ · 4H₂O (2b) were determined to R = 0.0332 and R = 0.0802, respectively. In both complexes the Pt(II) ions have a square-planar geometry with two adjacent corners being occupied by two nitrogens of HmtpO molecules for 2b or NH₃ and HmtpO molecules for 1, whereas the remaining adjacent corners are occupied by two chloride anions. Spectroscopic data confirm the square planar geometry with N(3) bonded HmtpO, S-bonded dimethylsulfoxide and two trans chloride anions for trans-PtCl₂(dmso) · 4H₂O (3).     

Magnetic single-component molecular conductors exhibiting strong π-d interactions

Single-component molecular conductors [M(tmdt)₂] (tmdt = trimethylenetetrathiafulvalenedithiolate; M = Ni, Au, Pt, Cu), exhibit a variety of electromagnetic properties, which originate from the differences of the metal’s d-orbitals role in the band structure formation. The [Au(tmdt)₂] crystal undergoes an antiferromagnetic transition at 110 K, while maintaining a metallic state at lower temperatures. The Au analog has a high magnetic transition temperature as compared to traditional magnetic molecular conductors due to the strong three-dimensional (3-D) structure and the contribution of the metal d-orbitals. The single-component molecular conductor, [Cu(tmdt)₂], with π- and d-like frontier orbitals is isostructural with other metallic [M(tmdt)₂] systems (M = Ni, Pt, Au). The Cu(tmdt)₂ molecule is planar, which strikingly contrasts the tetrahedral coordination of Cu(dmdt)₂ (dmdt = dimethyltetrathiafulvalenedithiolate) with similarly extended TTF type ligands. Interestingly, unlike other [M(tmdt)₂] with metallic behavior, [Cu(tmdt)₂] shows semiconducting behavior at room temperature (σ(RT) = ∼7 S cm⁻¹). The RT conductivity increased linearly with increased pressure to 110 S cm⁻¹ at 15 kbar despite the compressed pellet sample. The magnetic susceptibility indicates one-dimensional (1-D) Heisenberg behavior with J = 117 cm⁻¹ and shows antiferromagnetic ordering at 13 K. The [Cu(tmdt)₂] is a new multi-frontier π-d system, which introduces a d(σ)-type frontier orbital around the Fermi level of the π-like metal bands.     

An experimental and a DFT study on the synthesis, spectroscopic characterization, and reactivity of the adducts of dimethyl- and diphenyltin(IV) dichlorides with γ-pyrones [4H-pyran-4-one (PYR) and 2,6-dimethyl-4H-pyran-4-one (DMP)]: Crystal structure of Ph2SnCl2(PYR)

The Sn(IV) R₂SnCl₂(γ-pyrone)_n [R = Me or Ph; γ-pyrone = 4H-pyran-4-one (PYR) or 2,6-dimethyl-4H-pyran-4-one (DMP); n = 1 or 2] adducts have been synthesized and investigated. The adducts Ph₂SnCl₂(PYR) (1), Me₂SnCl₂(PYR)₂ (2), Ph₂SnCl₂(DMP) (3) and Me₂SnCl₂(PYR)(PNO) (4), (PNO = 4-methylpyridine N-oxide) have been prepared by the addition of the corresponding γ-pyrone to chloroform solution of R₂SnCl₂. The new compounds have been characterized by elemental analysis and spectroscopic (IR, ¹H, ¹³C NMR and Mössbauer) means. The single-crystal diffraction study of 1 shows the Sn(IV) to be five-coordinate, [Sn-O and Sn-Cl(1), Sn-Cl(2) distances of 2.3190(13) and 2.4312(6), 2.3653(7), respectively], and the Cl-Sn-Cl bond angle to be 91.17°. The reactivity of 2 towards bipy, Ph₃PO, QNO (Q = quinoline) resulted in complete displacement of PYR and formation of already known compounds whereas, the PNO displaced only one equivalent of PYR, causing the preparation of the new mixed complex 4, possibly through a S_N¹ formation mechanism. DFT/B3LYP molecular orbital calculations were carried out for the 1-4 complexes, their precursors, Ph₂SnCl₂, (5) and Me₂SnCl₂, (6) and the ligands, PYR, DMP and PNO in an attempt to explain the structures and reactivity of the complexes. Optimized resulting geometries, vibrational frequencies, and the electron-accepting ability of the complexes and the precursors towards nucleophiles are discussed.     

Preparation of imine complexes of ruthenium and osmium stabilised by [MCl(η -p-cymene)(PR3)] fragments

Imine complexes [MCl(η ⁶-p-cymene){η¹-NHC(H)Ar}(PR₃)]BPh₄ (1-3) [M = Ru, Os; PR₃ = PPh(OEt)₂, PPh₂OEt; Ar = Ph, p-tolyl] were prepared by reacting MCl₂(η ⁶-p-cymene)(PR₃) precursors with benzyl azide ArCH₂N₃ in the presence of NaBPh₄. Benzophenone-imine complexes [MCl(η ⁶-p-cymene){η¹-NHCPh₂}(PR₃)]BPh₄ (4-6) [M = Ru, Os; PR₃ = PPh(OEt)₂, PPh₂OEt] were also prepared by allowing MCl₂(η ⁶-p-cymene)(PR₃) to react with Ph₂CNH in the presence of NaBPh₄. The complexes were characterised spectroscopically (IR, ¹H, ¹³C, ³¹P, ¹⁵N NMR) and by X-ray crystal structure determination of [RuCl(η ⁶-p-cymene){η¹-NHC(H)-p-tolyl}{PPh(OEt)₂}]BPh₄ (1b).     

Synthesis, characterization and reactivity of tribenzylphosphine rhodium and iridium complexes

New rhodium and iridium complexes, with the formula [MCl(PBz₃)(cod)] [M = Rh (1), Ir (2)] and [M(PBz₃)₂(cod)]PF₆ [M = Rh (3), Ir (4)] (cod = 1,5-cyclooctadiene), stabilized by the tribenzylphosphine ligand (PBz₃) were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The addition of pyridine to a methanol solution of 1or 2, followed by metathetical reaction with NH₄PF₆, gave the corresponding derivatives [M(py)(PBz₃)(cod)]PF₆ [M = Rh (5), Ir (6)]. At room temperature in CHCl₃ solution, 4 converted spontaneously to the ortho-metallated complex [IrH(PBz₃)(cod){η²-P,C-(C₆H₄CH₂)PBz₂}]PF₆ (7) as a mixture of cis/trans isomers via intramolecular C-H activation of a benzylic phenyl ring. The reaction of 3 or 4 with hydrogen in coordinating solvents gave the dihydrido bis(solvento) derivative [M(H)₂(S)₂(PBz₃)₂]PF₆ (M = Rh, Ir; S = acetone, acetonitrile, THF), that transformed into the corresponding dicarbonyls [M(H)₂(CO)₂(PBz₃)₂]PF₆ by treatment with CO. Analogous cis-dihydrido complexes [M(H)₂(THF)₂(py)(PBz₃)₂]PF₆ (M = Rh, Ir) were observed by reaction of the py derivatives 5 and 6 with H₂.     

A novel 4.6 5-connected metal-organic framework with strong fluorescent emission constructed by m-thioacetatebenzoic acid

A novel uninodal 5-connected metal-organic framework (MOF), [Cd₂L₂(4,4′-bipy)_3/2(H₂O)₂]_n (H₂L=m-thioacetatebenzoic acid and 4,4′-bipy=4,4′-bipyridine), was prepared under hydrothermal condition. It features an unusual brick-wall shape layer by 4,4′-bipy, which consists of right- and left-handed helical chains arrayed alternatively and finally expands by L^2- to a rare 5-connected nov (4⁴.6⁶) topology network. Photoluminescence study reveals that it displays intense structure-related fluorescent emission bands (λ_ex=355 nm) at 450 nm in the solid state at room temperature.     

Synthesis, characterization and electrochemical behavior of some N-heterocyclic carbene-containing active site models of [FeFe]-hydrogenases

Treatment of parent compounds [(μ-SCH₂)₂X]Fe₂(CO)₆ (A, X = O; B, X = NBu-t; C, X = NC₆H₄OMe-p) with N-heterocyclic carbene I_Mes (I_Mes = 1,3-bis(mesityl)imidazol-2-ylidene) generated in situ through reaction of imidazolium salt I_Mes ·HCl with n-BuLi or t-BuOK afforded the monocarbene-substituted complexes [(μ-SCH₂)₂X]Fe₂(CO)₅(I_Mes) (1, X = O; 2, X = NBu-t; 3, X = NC₆H₄OMe-p). Similarly, the monocarbene and dicarbene-substituted complexes [(μ-SCH₂)₂NBu-t]Fe₂(CO)₅[I^∗_Mes(CH₂)₃I^∗_Mes]·HBr (4) and [(μ-SCH₂)₂CH₂Fe₂(CO)₅]₂[μ-I^∗_Mes(CH₂)₃I^∗_Mes] (5, I^∗_Mes = 1-(mesityl)imidazol-2-ylidene) could be prepared by reactions of parent compound B with the mono-NHC ligand-containing imidazolium salt [I^∗_Mes(CH₂)₃I^∗_Mes] · HBr and parent compound [(μ-SCH₂)₂CH₂]Fe₂(CO)₆ (D) with di-NHC ligand I^∗_Mes(CH₂)₃I^∗_Mes (both NHC ligands were generated in situ from reaction of n-BuLi with imidazolium salt [I^∗_MesI^∗_Mes(CH₂)₃I^∗_Mes] · 2HBr), respectively. The imidazolium salt [I^∗_Mes(CH₂)₃I^∗_Mes] · 2HBr was prepared by reaction of 1-(mesityl)imidazole with Br(CH₂)₃Br. All the new model compounds 1-5 and imidazolium salt [I^∗_Mes(CH₂)₃I^∗_Mes] · 2HBr were fully characterized by elemental analysis, spectroscopy, and X-ray crystallography. On the basis of electrochemical studies of 1 and 2, compound 2 was found to be a catalyst for proton reduction to hydrogen. In addition, an EECC mechanism for this electrocatalytic reaction is preliminarily suggested.