Structural analysis and photoluminescence properties of low dimensional lanthanide tetracyanometallates

The synthesis of a number of lanthanide tetracyanometallate (TCM) compounds have been carried out by reaction of Ln³⁺ nitrate salts and potassium tetracyanometallates in solvent systems containing dimethylsulfoxide and water. These reactions result in the isolation of three distinct structure types: (1) monoclinic [Ln(DMSO)₄(H₂O)₃M(CN)₄](M(CN)₄)_0.5·2H₂O (Ln = Eu, Tb and M = Pd, Pt), (2) orthorhombic {La(DMSO)₃(H₂O)₂(NO₃)M(CN)₄}_∞·H₂O (M = Pd, Pt), and (3) orthorhombic {Ln(DMSO)₃(H₂O)(NO₃)M(CN)₄}_∞ (Ln = Tb and M = Pd, Pt; Ln = Er, Yb and M = Pt) in the form of single crystals. Single-crystal X-ray diffraction has been used to investigate their structural features. Structure type 1 is a zero dimensional ionic compound with a M/Ln ratio of 1.5:1. It contains coordinated as well as uncoordinated [M(CN)₄]²⁻ (M = Pd, Pt) anions and features relatively long platinophilic interactions. Structure types 2 and 3 differ quite drastically from structure type 1, but they are very similar to each other. Both of the latter are one-dimensional in nature due to chains containing linkage of Ln³⁺ coordination spheres with trans-bridging [M(CN)₄]²⁻ anions. These coordination polymers both have a M/Ln ratio of 1:1, a lack of platinophilic interactions, and incorporation of a bidentate NO₃⁻ for charge balance. Photoluminescence properties for select Eu³⁺ and Tb³⁺ compounds have been investigated. They show characteristic absorption and emission for the Ln³⁺ ions, but no significant influence of the tetracyanometallate anions.     

Formation and structural chemistry of the unusual cyanide-bridged dinuclear species [Ru2(NN)2(CN)7] (NN = 2,2′-bipyridine or 1,10-phenanthroline)

Crystallisation of simple cyanoruthenate complex anions [Ru(NN)(CN)₄]²⁻ (NN = 2,2′-bipyridine or 1,10-phenanthroline) in the presence of Lewis-acidic cations such as Ln(III) or guanidinium cations results, in addition to the expected [Ru(NN)(CN)₄]²⁻ salts, in the formation of small amounts of salts of the dinuclear species [Ru₂(NN)₂(CN)₇]³⁻. These cyanide-bridged anions have arisen from the combination of two monomer units [Ru(NN)(CN)₄]²⁻ following the loss of one cyanide, presumably as HCN. The crystal structures of [Nd(H₂O)_5.5][Ru₂(bipy)₂(CN)₇] · 11H₂O and [Pr(H₂O)₆][Ru₂(phen)₂(CN)₇] · 9H₂O show that the cyanoruthenate anions form Ru-CN-Ln bridges to the Ln(III) cations, resulting in infinite coordination polymers consisting of fused Ru₂Ln₂(μ-CN)₄ squares and Ru₄Ln₂(μ-CN)₆ hexagons, which alternate to form a one-dimensional chain. In [CH₆N₃]₃[Ru₂(bipy)₂(CN)₇] · 2H₂O in contrast the discrete complex anions are involved in an extensive network of hydrogen-bonding involving terminal cyanide ligands, water molecules, and guanidinium cations. In the [Ru₂(NN)₂(CN)₇]³⁻ anions themselves the two NN ligands are approximately eclipsed, lying on the same side of the central Ru-CN-Ru axis, such that their peripheries are in close contact. Consequently, when NN = 4,4′-^tBu₂-2,2′-bipyridine the steric bulk of the t-butyl groups prevents the formation of the dinuclear anions, and the only product is the simple salt of the monomer, [CH₆N₃]₂[Ru(^tBu₂bipy)(CN)₄] · 2H₂O. We demonstrated by electrospray mass spectrometry that the dinuclear by-product [Ru₂(phen)₂(CN)₇]³⁻ could be formed in significant amounts during the synthesis of monomeric [Ru(phen)(CN)₄]²⁻ if the reaction time was too long or the medium too acidic. In the solid state the luminescence properties of [Ru₂(bipy)₂(CN)₇]³⁻ (as its guanidinium salt) are comparable to those of monomeric [Ru(bipy)(CN)₄]²⁻, with a ³MLCT emission at 581 nm.     

Photoactive trans ammine/amine diazido platinum(IV) complexes

The synthesis and characterisation of eight new octahedral Pt^IV complexes of the type trans,trans,trans-[Pt(N₃)₂(OH)₂(NH₃)(Am)] where Am = methylamine (2), ethylamine (4), thiazole (6), 2-picoline (8), 3-picoline (10), 4-picoline (12), cyclohexylamine (14), and quinoline (16) are reported, including the X-ray crystal structures of complexes 2, 8, and 14 as well as that of two of the precursor Pt^II complexes (trans-[Pt(N₃)₂(NH₃)(methylamine)] (1) and trans-[Pt(N₃)₂(NH₃)(cyclohexylamine)] (13)). Irradiation with UVA light rapidly induces loss in intensity of the azide-to-Pt^IV charge-transfer bands and gives rise to photoreduction of platinum. These complexes have potential for use as photoactivated anticancer agents.     

Tungsten complexes of aromatic and aliphatic thioaldehydes

Reaction of PPN[W(CO)₃(R₂PC₂H₄PR₂)(SH)] (PPN=Ph₃PNPPh₃; R=Me, 1; R=Ph, 2) with aromatic aldehydes in the presence of trifluoroacetic acid gave tungsten complexes of thiobenzaldehydes mer-[W(CO)₃(R₂PC₂H₄PR₂)(η²-SCHR^′)] (R=Me, 3a-3f; R=Ph, 4a-4e) in high yields. Analogous complexes of aliphatic thioaldehydes mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-SCHR^′)] (3g-3l) could only be obtained from the highly electron-rich thiolate complex 1. The structure of 3i (R^′=i-Bu) was determined by X-ray crystallography. In solution the complexes 3 and 4 are in equilibrium with small quantities of their isomers fac-[W(CO)₃(R₂PC₂H₄PR₂)(η²-SCHR^′)]. Reaction of complexes 3 with dimethylsulfate followed by salt metathesis with NH₄PF₆ gave the alkylation products mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-MeSCHR^′)]PF₆ (5a-5l) as mixtures of E and Z isomers. The methylated thioformaldehyde complex mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(η²-MeSCH₂)]PF₆ (5m) was prepared similarly. Nucleophilic addition of hydride (from LiAlH₄) to 5 initially gave thioether complexes mer-[W(CO)₃(Me₂PC₂H₄PMe₂)(MeSCH₂R^′)] (mer-6) which rapidly isomerized to fac-[W(CO)₃(Me₂PC₂H₄PMe₂)(MeSCH₂R^′)] (fac-6).     

Synthesis and crystal structure of a salicylatooxovanadium(V) complex of an aminebis(phenolate) ligand: Kinetic studies on its formation from corresponding alkoxo complexes

Synthesis and single crystal X-ray structures of H₂L¹ and VO(L¹)(HL) [H₂L¹ = N,N-bis(2-hydroxy-3,5-ditertiarybutyl)-N′,N′-dimethylethylendiamine) or simply aminebis(phenol) and H₂L = salicylic acid) are reported here. The complex [VO(L¹)(HL)] is in distorted octahedral geometry under O₄N₂ donor environment where the basal core is defined by O(1), O(3), O(2) and N(5) atoms and two axial coordinates are occupied by O(4), an alkoxo-group and N(1), an imino-nitrogen atom. The electron spray mass spectrometric study on [VO(L¹)(HL)] in MeCN clearly points out the existence of single species in solution. Again, the ⁵¹V NMR of the bulk polycrystalline sample reveals that the complex [VO(L¹)(HL)] mainly exists in three out of four possible isomers. The formation of [VO(L¹)(HL)] from both [VO(L¹)(OMe)] and [VO(L¹)(OEt)] was followed kinetically by reacting with salicylic acid in MeCN. The presence of isosbestic point indicates a clean conversion of the reactants to product.     

The concentration controlled 1D and 2D supramolecular isomers of lanthanide with 2,2’-bipyridyl-3,3’-dicarboxylate and phenanthroline

The reactions of 2,2′-bipyridyl-3,3′-dicarboxylic acid (H₂bpdc) and 1,10-phenanthroline (phen) with lanthanide (III) salts in different concentrations under hydrothermal conditions formed two series of supramolecular isomers of 1D zigzag chains of [Ln(bpdc)_1.5(phen)(H₂O)]_n·3nH₂O (1Ln·3H₂O), and 2D frameworks of [Ln(bpdc)_1.5(phen)(H₂O)]_n (2Ln), (Ln = Ho, Er, Tm, and Yb). At lower concentrations, the supramolecular isomers of 1Ln were formed, in which each isomer has a dinuclear centrosymmetric dimeric unit of [Ln₂(phen)₂(H₂O)₂(μ₂-bpdc)₂]²⁺, and the dimeric units are alternately connected by μ₂-bpdc²⁻ to form a 1D zigzag chain of 1Ln. At higher concentrations, the supramolecular isomers of 2Ln were formed. All the compounds of 2Ln are isomorphous, in which two μ₃-bpdc²⁻ bridge two [Ln(phen)(H₂O)]³⁺ units to yield a 1D double-chains of [Ln₂(phen)₂(H₂O)₂(bpdc)₂]_n²ⁿ⁺, and [Ln₂(phen)₂(H₂O)₂(bpdc)₂]_n²ⁿ⁺ chains are further connected by μ₄-bpdc²⁻ to form a 2D network of [Ln(bpdc)_1.5(phen)(H₂O)]_n. The 2D sheets are combined through the intersheet π-π interactions between the adjacent phen molecules to form a 3D structure of 2Ln. The compounds of Er(III), and Yb(III) exhibit corresponding characteristic photoluminescence in the near-infrared (NIR) region, in which 1Ln and 2Ln show obviously different emission intensity due to their different structures.     

Synthesis and properties of new trinuclear Mo(II) complexes containing imidazole and benzimidazole ferrocene units

The reaction of FcCOCl (Fc = (C₅H₅)Fe(C₅H₄)) with benzimidazole or imidazole in 1:1 ratio gives the ferrocenyl derivatives FcCO(benzim) (L1) or FcCO(im) (L2), respectively. Two molecules of L1 or L2 can replace two nitrile ligands in [Mo(η³-C₃H₅)(CO)₂(CH₃CN)₂Br] or [Mo(η³- C₅H₅O)(CO)₂(CH₃CN)₂Br] leading to the new trinuclear complexes [Mo(η³-C₃H₅)(CO)₂(L)₂Br] (C1 for L = L1; C3 for L = L2) and [Mo(η³-C₅H₅O)(CO)₂(L)₂Br] (C2 for L = L1; C4 for L = L2) with L1 and L2 acting as N-monodentade ligands. L1, L2 and C2 were characterized by X-ray diffraction studies. [Mo(η³-C₅H₅O)(CO)₂(L1)₂Br] was shown to be a trinuclear species, with the two L1 molecules occupying one equatorial and one axial position in the coordination sphere of Mo(II). Cyclic voltammetric studies were performed for the two ligands L1 and L2, as well as for their molybdenum complexes, and kinetic and thermodynamic data for the corresponding redox processes obtained. In agreement with the nature of the frontier orbitals obtained from DFT calculations, L1 and L2 exhibit one oxidation process at the Fe(II) center, while C1, C3, and C4 display another oxidation wave at lower potentials, associated with the oxidation of Mo(II).     

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.     

Synthesis of [SnPh2(SR)2] SR = SC6F4-4-H, SC6F5: Reactivity towards group 10 transition metal complexes

The organometallic tin(IV) complexes [SnPh₂(SR^F)₂] SR^F = ⁻SC₆F₄-4-H (1), ⁻SC₆F₅ (2), were synthesized and their reactivity with [MCl₂(PPh₃)₂] M = Ni, Pd and Pt explored. Thus, transmetallation products were obtained affording polymeric [Ni(SR^F)(μ-SR^F)]_n, monomeric cis-[Pt(PPh₃)₂(SC₆F₄-4-H)₂] (3) and cis-[Pt(PPh₃)₂(SC₆F₅)₂] (4) and dimeric species [Pd(PPh₃)(SC₆F₄-4-H)(μ-SC₆F₄-4-H)]₂ (5) and [Pd(PPh₃)(SC₆F₅)(μ-SC₆F₅)]₂ (6) for Ni, Pt and Pd, respectively. The crystal structures of complexes 1, 2, 3, 4 and 6 were determined.     

Synthesis of amidate-hanging platinum mononuclear complexes by base hydrolysis of nitrile complexes

The “amidate-hanging” Pt mononuclear complexes, which can easily bind a second metal ion with the non-coordinated oxygen atoms in the amidate moieties, have been synthesized and characterized by ¹H NMR, MS, IR spectroscopy, and single crystal X-ray analysis. Five new complexes with various amidate ligands and co-ligands, cis-[Pt(PVM)₂(en)] · 4H₂O (1, PVM = pivaloamidate, en = ethylenediamine), cis-[Pt(PVM)₂(NH₂CH₃)₂] · H₂O (2), cis-[Pt(PVM)₂(NH₂^tBu)₂] (3), cis-[Pt(TCM)₂(NH₃)₂] (4, TCM = trichloroacetamidate), and cis-[Pt(BZM)₂(NH₃)₂] (5, BZM = benzamidate), were successfully synthesized by direct base hydrolysis of the corresponding Pt nitrile complexes, cis-[Pt(NCR)₂(Am)₂]²⁺ (P1, P2, P3, and P5) (NCR = nitrile, Am = amine). These nitrile complexes were obtained by introducing nitriles into the Pt aqua complexes, cis-[Pt(OH₂)₂(Am)₂](ClO₄)₂, whereas introduction of trichloronitrile into [Pt(OH₂)₂(NH₃)₂](ClO₄)₂ induced more facilitated water nucleophilic attack to afford [Pt(TCM)(NH(COH)CCl₃)(NH₃)₂](ClO₄) (P4). The base treatments of the precursor complexes (P1-5) lead to produce “amidate-hanging” Pt mononuclear complexes (1-5) without geometry isomerization. The ¹⁹⁵Pt chemical shifts for 1-5 exhibit subtle differences of the Pt electron densities among them.     

Syntheses and molecular structures of Co-Na and Co-K coordination polymers constructed using mono- and bis-chelated cobalt(III) complexes of bis(2-pyridylcarbonyl)amide ion

Four new hetero-bimetallic Co³⁺-Na⁺ and Co³⁺-K⁺ coordination polymers having the molecular formulae [Na(H₂O)Co(L)(N₃)₃]_n (1), [Na₂Co(L)(N₃)₃(H₂O)₅][Co(L)(N₃)₃] (2), K[Co(L)(NCS)₃]·H₂O (3) and K[Co(L)₂][Co(NCS)₄]·0.5H₂O (4), were synthesized. Compounds 1-4 were characterized by single crystal X-ray diffraction, IR, UV-Vis, and thermogravimetric methods. These bimetallic systems have EE, EO azide bridge (1, 2) as well as bent (1, 2, 3) and linear (1, 4) aquo bridges. Important features observed among them were: a Z-shaped and diamond-shaped Co₂Na₂ clusters in 1, a centrosymmetric double ladder like polymer based on Na₄ cluster in 2, and a linear KOK core having paddle-wheel structure in 4.     

Pd(II) complexes containing N-alkyl-3-pyridine-5-trifluoromethyl pyrazole ligands: Synthesis, NMR studies and X-ray crystal structures

Palladium [PdCl₂(L)] complexes with N-alkylpyridylpyrazole derived ligands [2-(5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L¹), 2-(1-ethyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L²), 2-(1-octyl-5-trifluoromethyl-1H-pyrazol-3-yl)pyridine (L³), and 2-(3-pyridin-2-yl-5-trifluoromethyl-pyrazol-1-yl)ethanol (L⁴) were synthesised. The crystal and molecular structures of [PdCl₂(L)] (L = L², L³, L⁴) were resolved by X-ray diffraction, and consist of monomeric cis-[PdCl₂(L)] molecules. The palladium centre has a typical square-planar geometry, with a slight tetrahedral distortion. The tetra-coordinate metal atom is bonded to one pyridinic nitrogen, one pyrazolic nitrogen and two chlorine ligands in cis disposition. Reaction of L (L², L⁴) with [Pd(CH₃CN)₄](BF₄)₂, in the ratio 1M:2L, gave complexes [Pd(L)]₂(BF₄)₂. Treatment of [PdCl₂(L)] (L = L², L⁴) with NaBF₄ and pyridine (py) and treatment of the same complexes with AgBF₄ and triphenylphosphine (PPh₃) yielded [Pd(L)(py)₂](BF₄)₂ and [Pd(L)(PPh₃)₂](BF₄)₂ complexes, respectively. Finally, reaction of [PdCl₂(L⁴)] with 1 equiv of AgBF₄ yields [PdCl(L⁴)](BF₄).     

Dithiocarbazate complexes with the [M(PPh3)] (M═Pd or Pt) moiety: Synthesis, characterization and anti-Tripanosoma cruzi activity

New neutral Pd(II) and Pt(II) complexes of the type [M(L)(PPh₃)] (M═Pd or Pt) were prepared in crystalline form in high-yield synthesis with the S-benzyldithiocarbazates and S-4-nitrobenzyldithiocarbazates derivatives from 2-hydroxyacetophenone, H₂L^1a and H₂L^1b, and benzoylacetone, H₂L^2a and H₂L^2b. The new complexes [Pt(L^1a)(PPh₃)] (1), [Pd(L^1a)(PPh₃)] (2), [Pt(L^1b)(PPh₃)] (3), [Pd(L^1b)(PPh₃)] (4), [Pt(L^2a)(PPh₃)] (5), [Pd(L^2a)(PPh₃)] (6), [Pt(L^2b)(PPh₃)] (7) and [Pd(L^2b)(PPh₃)] (8) were characterized on the basis of elemental analysis, conductivity measurements, UV-visible, IR, electrospray ionization mass spectrometry (ESI-MS), NMR (¹H and ³¹P) and by X-ray diffraction studies. The studies showed that differently from what was observed for the H₂L^1a and H₂L^1b ligands, H₂L^2a and H₂L^2b assume cyclic forms as 5-hydroxypyrazolinic. Upon coordination, H₂L^2a and H₂L^2b suffer ring-opening reaction, coordinating in the same manner as H₂L^1a and H₂L^1b, deprotonated and in O,N,S-tridentate mode to the (MPPh₃)²⁺ moiety. All complexes show a quite similar planar fourfold environment around the M(II) center. Furthermore, these complexes exhibited biological activity on extra and intracellular forms of Trypanosoma cruzi in a time- and concentration-dependent manner with IC₅₀ values ranging from 7.8 to 18.7 μM, while the ligand H₂L^2a presented a trypanocidal activity on trypomastigote form better than the standard drug benznidazole.     

Hydrothermal syntheses, structures and properties of five rare earth coordination polymers with (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid

Hydrothermal reactions of rare earth ions(III) with a flexible building unit (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid (H₂tzda) lead to five novel coordination polymers with 1D chain and 3D network structures, namely, {[Y₂(tzda)₃(H₂O)₁₀] · 5H₂O}_n (1) and [Ln₂(tzda)₃(H₂O)₅]_n [Ln = Er (2), Pr (3), Nd (4), Eu (5)]. Compound 1 has one-dimensional ribbon-like chain structure constructed by [Y₂(tzda)₃] units through the syn-anti bidentate bridging mode of carboxylate groups. Compounds 2-5 possess compact three-dimensional network structures which are made up of [Ln₂(tzda)₃] (Ln = Er, Pr, Nd and Eu) units bridged by carboxylate groups. In these compounds, the flexible tzda²⁻ ligand is versatile and displays six different coordination fashions to meet the requirement of the coordination preference of the metal center. Furthermore, the magnetic behaviors for 2-5 in the temperature range of 5.0-300 K and photoluminescent property of 5 are significantly investigated in this paper.     

Structure, magnetic properties and nuclease activity of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) complexes

New complexes of formulae [Cu(HL²)(H₂O)(NO₃)](NO₃) (1), [{Cu(L¹)(tfa)}₂] (2), [{Cu(L¹)}₂(pz)](ClO₄)₂ (3) and {[{Cu(L¹)}₂(dca)](ClO₄)}_n (4), where HL¹ = pyridine-2-carbaldehyde thiosemicarbazone, HL² = pyridine-2-carbaldehyde 4N-methylthiosemicarbazone, Htfa = trifluoroacetic acid (CF₃COOH), pz = pyrazine (C₄H₄N₂) and dca = dicyanamide [N(CN)₂]⁻, have been synthesized and characterized. The crystal structures of these compounds are built up of monomers (1), dinuclear entities with the metal centers bridged through the non-thiosemicarbazone coligand (2 and 3) and 1D chains of dimers (4). In all the cases, square-pyramidal copper(II) ions are present, except for the square-planar ones in 3. Magnetic measurements show antiferromagnetic couplings in 2, 3 and 4. The susceptibility data were fitted by the Bleaney-Bowers’ equation for copper(II) dimers derived from H = -2JS₁S₂ being the obtained J/k values −4.8, −4.3 and −5.1 K for compounds 2-4, respectively. The magnetic susceptibility of the already known [{Cu(HL¹)(tfa)}₂](tfa)₂ compound has been also measured for the first time. The J/k value is -0.3 K, lower than that in 2. The nuclease activity of 3 and 4 has been analyzed.     

Synthesis and structural characterization of trans-[Mo2(H2DMepyF)2(CH3CN)4](BF4)6 (HDMepyF=N,N-di(6-methyl-2-pyridyl)formamidine)

Reaction of Mo₂(O₂CCH₃)₂(DMepyF)₂ (HDMepyF=N,N^′-di(6-methyl-2-pyridyl)formamidine) with HBF₄ in CH₂Cl₂/CH₃CN afforded the complex trans-[Mo₂(H₂DMepyF)₂(CH₃CN)₄](BF₄)₆ (1), which crystallized in two forms, trans-[Mo₂(H₂DMepyF)₂(CH₃CN)₄](ax-CH₃CN)₂(BF ₄)₆ · 2CH₃CN (1a), and trans- [Mo₂(H₂DMepyF)₂(CH₃CN)₄](ax-BF₄) ₂(BF₄)₄ · 2CH₃CN (1b). The molecular structures of complexes (1) consist of two quadruply bonded molybdenum atoms, which are spanned by two trans-bridging formamidinate ligands and coordinated by four trans-CH₃CN. Each H₂DMepyF⁺ ligand adopts an s-cis,s-cis- conformation. The difference between 1a and 1b is that complex 1a contains two CH₃CN molecules as axial ligands, while 1b contains two BF₄⁻ anions as axial ligands. Complex 1 is the first dimolybdenum complex containing a pair of trans bridging ligands and two pairs of trans-CH₃CN ligands.     

A 3-D (3,5)-connected Cd coordination framework with unique twofold interpenetrating (4·6)(4·6·8) network topology

Assembly of N,N′-bis(4-picolinoyl)hydrazine (H₂L) with cadmium nitrate in the presence of dicyanamide anion (dca) affords a new coordination polymer {[Cd(HL)(dca)] · (H₂O)_0.5}_n (1), in which the [Cd(HL)]_n layers are extended by dca bridges to result in a three-dimensional (3-D) coordination framework. The network structure of 1 has unusual (3,5)-connectivity and represents a new type of (4·6²)(4·6⁶·8³) topology. Two such identical and complementary networks are entangled to generate a twofold parallel interpenetrating supramolecular lattice.     

Conversion of 2-(aminomethyl) substituted pyridine and quinoline to their dicarbonyldiimides using copper(II) acetate

In air, hydrated ethanolic (95%) solution of 2-(aminomethyl) substituted pyridine and quinoline, on stirring with half equivalent of Cu(OAc)₂·H₂O, respectively afforded [Cu(bpca)(OAc)(H₂O)]·H₂O (1) and [Cu(bqca)(OAc)(H₂O)] (2) {bpca = bis(2-pyridylcarbonyl)diimide ion and bqca = bis(2-quinolylcarbonyl)diimide ion} in good yields. These reactions involve oxidation of the methylene group and formation of the bond between nitrogen and carbon in N-C(O) through coupling. The complex [Cu(pqca)(OAc)(H₂O)]₃[Cu₂(OAc)₄(EtOH)₂]_1.5 (3) {pqca = (2-pyridylcarbonyl)(2-quinolylcarbonyl)diimide ion} was synthesized by stirring an ethanolic solution of the Schiff base [(2-pyridyl)-N-((2-quinolyl)methylene)methanamine] (L1) and with one equivalent of Cu(OAc)₂·H₂O. A plausible mechanism for the conversion has been proposed. The free ligands were isolated as crystalline solids from compounds 1-3, by extrusion of Cu²⁺ ion using EDTA²⁻. The molecular structures of 1-3 and bqcaH were established by X-ray crystallography and compounds having quinolyl group have π-stacking interactions.     

Synthesis, structure, photophysical and electrochemical behavior of 2-amino-anthracene triosmium clusters

The reactions of 2-amino-anthracene with [Os₃(CO)₁₀(CH₃CN)₂] have been studied and the products structurally characterized by spectroscopic, X-ray diffraction, photophysical and electrochemical techniques. At room temperature in CH₂Cl₂ two major, isomeric products are obtained [Os₃(CO)₁₀(μ-η²-(N-C(1))-NH₂C₁₄H₈)(μ-H)] (1, 14%) and [Os₃(CO)₁₀(μ-η²-(N-C(3))-NHC₁₄H₉)(μ-H)] (2, 35%) along with a trace amount of the dihydrido complex [Os₃(CO)₉(μ-η²-(N-C(3))-NHC₁₄H₈)(μ-H)₂] (3). In refluxing tetrahydrofuran only complexes 2 and 3 are obtained in 24% and 28%, respectively. A separate experiment shows that complex 1 slowly converts to 2 and that the rearrangement is catalyzed by adventitious water and involves proton transfer to the anthracene ring. Complex 1 is stereochemically non-rigid; exhibiting edge to edge hydride migration while 2 is stereochemically rigid. Complex 3 is also stereochemically non-rigid showing a site exchange process of the magnetically nonequivalent hydrides typical for trinuclear dihydrides. Interestingly, 2 decarbonylates cleanly to the electronically unsaturated 46e⁻ cluster [Os₃(CO)₉(μ₃-η²-(N-C(3))-NHC₁₀H₉)(μ-H)] (4, 68%) in refluxing cyclohexane, while photolysis of 2 in CH₂Cl₂ yields only a small amount of 3 along with considerable decomposition. The mechanism of the conversion of 1 to 2 and the dependence of the product distribution on solvent are discussed. All four compounds are luminescent with compounds 1-3 showing emissions that can be assigned to radiative decay associated with the anthracene ligand. Complexes 1-3 all show irreversible 1e⁻ reductions in the range of −1.85-2.14 V while 4 shows a nicely reversible 1e⁻ wave at −1.16 V and a quasi-reversible second 1e⁻ wave at −1.62 V. Irreversible oxidations are observed in the range from +0.35 to +0.49 V. The relationship between the cluster ligand configurations and the observed electrochemical and photochemical behavior is discussed and compared with that of the free ligand.     

Stereospecific interactions between dinuclear complex cations involving square-planar [Pt(II)(μ-S)2(bpy)] (bpy = 2,2′-bipyridine) frameworks derived from optically active octahedral Co(III) units with d- or l-penicillaminates

The reaction of the octahedral mononuclear complex, trans(N)-[Co(l-pen-N,O,S)₂]⁻ (pen = penicillaminate), with [PtCl₂(bpy)] (bpy = 2,2′-bipyridine) stereoselectively gave an optically active S-bridged dinuclear complex, [Pt(bpy){Co(l-pen)₂}]Cl · 3H₂O (2Cl · 3H₂O), whose structure is enantiomeric to the previously reported [Pt(bpy){Co(d-pen)₂}]Cl · 3H₂O (1Cl · 3H₂O). The mixture of equimolar amounts of 1Cl · 3H₂O and 2Cl · 3H₂O in H₂O crystallizes as [Pt(bpy){Co(d-pen)₂}]_0.5[Pt(bpy){Co(l-pen)₂}]_0.5Cl · 7H₂O (3Cl · 7H₂O), in which the enantiomeric complex cations 1 and 2 are included in the ratio of 1:1. The crystal structures of 2Cl · 3H₂O and 3Cl · 7H₂O were determined by X-ray crystallography, and compared with that of 1Cl · 3H₂O. The structural feature for 2 is essentially consistent with that for 1, except for the absolute configurations around the octahedral Co(III) center. The optically active complex cation 2 exists as a monomer, accompanied by no intermolecular interactions in the π-electronic systems of bpy moieties. In the crystals of 3Cl · 7H₂O, on the other hand, the enantiomeric complex cations, [Pt(bpy){Co(d-pen)₂}]⁺ and [Pt(bpy){Co(l-pen)₂}]⁺, are arranged alternately while overlapping the bpy planes along a axis, and the π electronic system of the bpy framework in [Pt(bpy){Co(d-pen)₂}]⁺ interacts with those in [Pt(bpy){Co(l-pen)₂}]⁺. Differences between the crystal structures of 2Cl · 3H₂O and3Cl · 7H₂O significantly reflect their diffuse reflectance spectra. In aqueous solution, each cation in both 2Cl · 3H₂O and 3Cl · 7H₂O is comparatively put on a free environment without such intermolecular interactions.