Octahedral cyanohydroxo cluster complex trans-[Re6Se8(CN)4(OH)2]: Synthesis, crystal structure, and properties

A hexarhenium cyanohydroxo anionic cluster complex [Re₆Se₈(CN)₄(OH)₂]⁴⁻ was synthesized for the first time starting from [Re₆Se₈(OH)₆]⁴⁻, which was crystallized as a salt of the composition Cs_2.75K_1.25[Re₆Se₈(CN)₄(OH)₂]·H₂O (1). The reaction of the complex with Cu²⁺ in an aqueous ammonia or methylamine solutions afforded [Cu(NH₃)₅]₂[Re₆Se₈(CN)₄(OH)₂]·8H₂O (2) or [{Cu(CH₃NH₂)₄}₂Re₆Se₈(CN)₄(OH)₂] (3), respectively. All of these three compounds were characterized by a single-crystal X-ray diffraction method. Compound 1 is crystallized in the tetragonal space group I4/m with eight formula units per cell (a = b = 17.4823(14) Å, c = 19.430(2) Å, V = 5938.3(10) Å³); compound 2 is crystallized in the monoclinic space group P2₁/n with two formula units per cell (a = 12.1845(13) Å, b = 8.6554(9) Å, c = 19.2568(19) Å, β = 91.081(2)°, V = 2030.5(4) Å³); compound 3 is crystallized in the orthorhombic space group Cmcm with four formula units per cell (a = 19.816(4) Å, b = 14.611(3) Å, c = 13.751(3) Å, V = 3981.2(13) Å³). The luminescence properties of 1 were studied in both aqueous solution and solid state. In addition, the electronic structure of [Re₆Se₈(CN)₄(OH)₂]⁴⁻ was elucidated by DFT calculations.     

Novel supramolecular compounds based on Cucurbit[6]uril, 1,8-diaminooctane and octahedral thiohydroxo anions with cluster core [Re6S8]

Supramolecular compounds {C₈N₂H₂₂@Cuc[6]}{Re₆S₈(H₂O)₂(OH)₄}·18H₂O (1), and K₂{C₈N₂H₂₂@Cuc[6]}{Re₆S₈(OH)₆}·14H₂O (2) were obtained by crystallization from aqueous solutions that contained the macrocyclic cavitand cucurbit[6]uril (C₃₆H₃₆N₂₄O₁₂), 1,8-diaminooctane and the cluster thiohydroxo complex [Re₆S₈(OH)₆]⁴⁻. The resultant composition of the formed compounds depends on the experiment technique. According to the X-ray diffraction analysis, 1,8-diaminooctane molecules are encapsulated within the cavity of the cucurbit[6]uril molecules in such a way that the aminogroups are above and below the plane of the cavitand. The 1,8-diaminooctane molecules formed hydrogen bonds with the cavitand and the cluster thiohydroxo complexes to give chains.     

A new self-assembled inorganic-organic hybrid layered compound containing hexarhenium cluster: [MV][{Mn(CH3OH)2}{Re6Se8(CN)6}]

A new layered compound, [MV][{Mn(CH₃OH)₂}{Re₆Se₈(CN)₆}] (1) consists of a layer alternately knitted by hexarhenium cluster and Mn complex, and MV²⁺ cations (methyl viologen dication = 1,1′-dimethyl-4,4′-bipyridilium dication) reside between the layers. The title compound 1 is the first layered framework containing cyano-hexarhenium clusters with photoactive guest molecules, MV²⁺. The MV²⁺ can be partly exchanged by H₂TMB²⁺ (N,N,N′,N′-tetramethylbenzidine dication) to form a compound [H₂TMB²⁺]_x[MV²⁺]_1−x [{Mn(CH₃OH)₂}{Re₆Se₈(CN)₆}] (2) showing an electronic interaction between the layered framework and [H₂TMB]²⁺ cation.     

Mixed chloride-phosphine complexes of the dirhenium core. Part 11. Reactions of [Re2Cl8] with secondary phosphines, PCy2H and PPh2H

The reaction between the dirhenium(III,III) anion, [Re₂Cl₈]²⁻, and the secondary phosphine, PCy₂H, yields a mixture of products as a result of disproportionation, namely, a dirhenium(II,III) chloride-phosphine complex 1,3,6-Re₂Cl₅(PCy₂H)₃ (1) and a dirhenium(IV) face-sharing bioctahedral compound with bridging phosphido groups, [Buⁿ ₄N][Re₂(μ-PCy₂)₃Cl₆] (2). The diphenylphosphine analogue of 2, [Buⁿ ₄N][Re₂(μ-PPh₂)₃Cl₆] (3) has been similarly prepared from the reaction of [Re₂Cl₈]²⁻ with PPh₂H. An interesting dirhenium(III,III) complex, [Buⁿ ₄N]₂[Re₂(μ-PPh₂)₂(PPh₂H)₂Cl₆] (4) having both neutral terminal phosphines and anionic phosphido bridges, has also been isolated as an intermediate in the latter system. Crystal structures of 1-4 have been determined by X-ray crystallography. The compounds were also characterized by cyclic voltammetry, IR and ³¹P NMR spectroscopy.     

Electrochemical behavior of S,S-bridged adducts of square planar metalladithiolene complexes [M(S2C2Ph2)2](M=Ni, Pd, and Pt)

The electrochemical behavior of the S,S^′-bridged adducts of square planar metalladithiolene complexes was investigated by using cyclic voltammetry and electrochemical spectroscopies (visible, near-IR, and ESR). The norbornene-bridged S,S^′-adduct [Ni(S₂C₂Ph₂)₂(C₇H₈)] (2a; C₇H₈=norbornene) formed by [Ni(S₂C₂Ph₂)₂] (1a) and quadricyclane (Q) was dissociated by an electrochemical reduction, and anion 1a⁻ and norbornadiene (NBD) were formed. Q was isomerized to NBD in the overall reaction. The o-xylyl-bridged S,S^′-adduct [Ni(S₂C₂Ph₂)₂(CH₂)₂(C₆H₄)] (3a; (CH₂)₂(C₆H₄)=o-xylyl) was also dissociated by an electrochemical reduction, and this reaction gave the o-xylyl radical (o-quinodimethane). The reduction of complex 3a in the presence of excess o-xylylene dibromide underwent the catalytic formation of o-quinodimethane. The butylene-bridged S,S^′-adduct [Ni(S₂C₂Ph₂)₂(CH₂)₄] (4a; (CH₂)₄=butylene) was stable on an electrochemical reduction. The lifetimes of reduced species of these adducts 2a-4a were influenced by the stability of the eliminated group (stability: NBD > o-xylyl radical (o-quinodimethane) > butylene radical). Therefore, the reduced species are stable in the sequence 4a⁻ > 3a⁻ > 2a⁻. Although the palladium complex [Pd(S₂C₂Ph₂)₂] (1b) was easier to reduce than the nickel complex 1a or the platinum complex [Pt(S₂C₂Ph₂)₂] (1c), their S,S^′-adducts were easier to reduce in the order of Ni adduct > Pd adduct > Pt adduct.     

Octahedral rhenium cluster complexes with organic ligands: Synthesis, structure and properties of [Re6Q8(3,5-Me2PzH)6]Br2 · 2(3,5-Me2PzH) (Q = S, Se)

Two new octahedral cluster complexes - [Re₆S₈(3,5-Me₂PzH)₆]Br₂ · 2(3,5-Me₂PzH) (1) and [Re₆Se₈(3,5-Me₂PzH)₆]Br₂ · 2(3,5-Me₂PzH) (2), where 3,5-Me₂PzH is 3,5-dimethylpyrazole, have been synthesized using reaction of rhenium chalcobromide complexes Cs₄[Re₆S₈Br₆] · 2H₂O and Cs₃[Re₆Se₈Br₆] · H₂O, respectively, with molten 3,5-dimethylpyrazole. Both compounds synthesized were characterized by X-ray single-crystal diffraction and chemical analysis, IR and luminescent spectra.     

Syntheses and structures of the heterometallic clusters [(Ph3PAu)3Re(CO)4], [(Ph3PAu)4Re(CO)4], [(Ph3PAu)6AuRe2(CO)8], and [(Ph3PAu)6Re(CO)3]

The reaction of [HRe₃(CO)₁₂]²⁻ with an excess of Ph₃PAuCl in CH₂Cl₂ yields [(Ph₃PAu)₄Re(CO)₄]⁺ as the main product, which crystallizes as [(Ph₃PAu)₄Re(CO)₄]PF₆ · CH₂Cl₂ (1 · CH₂Cl₂) after the addition of KPF₆.The crystal structure determination reveals a trigonal bipyramidal Au₄Re cluster with the Re atom in equatorial position.If [(Ph₃PAu)₄Re(CO)₄]⁺ is reacted with PPh₄Cl, a cation [Ph₃PAu]⁺ is eliminated as Ph₃PAuCl, and the neutral cluster [(Ph₃PAu)₃Re(CO)₄] (2) is formed.It combines with excess [(Ph₃PAu)₄Re(CO)₄]⁺ to afford the cluster cation, [(Ph₃PAu)₆AuRe₂(CO)₈]⁺. It crystallizes from CH₂Cl₂ as[(Ph₃PAu)₆AuRe₂(CO)₈]PF₆ · 4CH₂Cl₂ (3 · 4CH₂Cl₂). In [(Ph₃PAu)₃Re(CO)₄] the metal atoms are arranged in form of a lozenge while in [(Ph₃PAu)₆AuRe₂(CO)₈]⁺ two Au₄Re trigonal bipyramids are connected by a common axial Au atom.The treatment of [(Ph₃PAu)₄Re(CO)₄]⁺ with KOH and Ph₃PAuCl in methanol yields the cluster cation [(Ph₃PAu)₆Re(CO)₃]⁺, which crystallizes with from CH₂Cl₂ as [(Ph₃PAu)₆Re(CO)₃]PF₆ · CH₂Cl₂ (4 · CH₂Cl₂). The metal atoms in this cluster form a pentagonal bipyramid with the Re atom in the axial position.     

Oxoselenide triangular molybdenum clusters: Synthesis and characterization of [Mo3SeO3(acac)3(py)3]PF6

New cluster complex [Mo₃SeO₃(acac)₃(py)₃]⁺ was obtained by ligand substitution in the aqua complex [Mo₃SeO₃(H₂O)₉]⁴⁺. Crystal structure was determined for [Mo₃SeO₃(acac)₃(py)₃]PF₆·C₆H₅CH₃. The complex was characterized by ⁷⁷Se NMR, electrospray mass-spectrometry, and cyclic voltammetry. DFT calculations were used to confirm the assignment of chemical shift and to study Mo-Mo bonding in the cluster core.     

Interactions of tertiary phosphines with p-benzoquinones; X-ray structures of [HO(CH2)3]3PC6H2(O)(OH)(MeO) and Ph3PC6H3(O)(OH)

Phosphonium zwitterions of a known type were obtained in high yield via a 1:1 reaction of p-benzoquinone or methoxy-p-benzoquinone with the tertiary phosphines R₃P [R = (CH₂)₃OH, Ph, Et, Me] and Ph₂MeP, in acetone or benzene at room temperature. In all cases, attack of the P-atom occurs at a C-atom rather than at an O-atom. The products were characterized to various degrees by elemental analysis, ³¹P{¹H}, ¹H and ¹³C NMR spectroscopies, and mass spectrometry, and two of the zwitterions, the new [HO(CH₂)₃]₃P⁺C₆H₂(O⁻)(OH)(MeO) and the known Ph₃P⁺C₆H₃(O⁻)(OH), were structurally characterized by X-ray analysis. The PEt₃ reaction also produces small amounts of the ‘dimeric’, μ-oxo co-product Et₃P⁺C₆H₂(O⁻)(OH)-O-C₆H₃(O⁻)P⁺Et₃ that is tentatively characterized by 1D- and 2D-NMR data. 2,5-Di-tert-butyl- and 2,3,5,6-tetramethyl-p-benzoquinone do not react with [HO(CH₂)₃]₃P under the conditions noted above. Heating D₂O solutions of the water-soluble zwitterions R₃P⁺C₆H₃(O⁻)(OH) [R = (CH₂)₃OH, Et] at 90 °C for 72 h leads to complete H/D exchange of the H-atom in the position ortho to the phosphonium center.     

Coordination chemistry of acrylamide 6: Formation and structural characterization of [Fe(O-OC(NH2)CHCH2)6][Fe2OCl6]

The new acrylamide iron(II)/iron(III) complex [Fe(O-OC(NH₂)CHCH₂)₆][Fe₂OCl₆] (1) was obtained by the reaction of a mixture of anhydrous FeCl₂ and anhydrous FeCl₃ with acrylamide (molar ratio 1:2:6) in 98% pure commercial nitromethane under nitrogen atmosphere. According to an X-ray structural analysis, the acrylamide ligands in the cation are coordinated via the amide-oxygen atoms. The formation of the (μ-oxo)bis[trichloroferrate(III)]²⁻ anion presumably resulted from partial hydrolysis of FeCl₃ or [FeCl₄]⁻ by small amounts of water in the nitromethane and/or by the nitromethane itself.     

A new example of a tetranuclear iron(III) cluster containing the [Fe4O2] core: preparation, X-ray crystal structure, magnetochemistry and Mössbauer study of [Fe4O2(O2CMe)6(N3)2(phen)2]

Two synthetic procedures have been employed that allow access to the new tetranuclear cluster [Fe₄O₂(O₂CMe)₆(N₃)₂(phen)₂] (1), where phen is 1,10-phenanthroline. Complex 1 · 3MeCN displays an unusual structural asymmetry (observed for the second time) in its [Fe₄O₂]⁸⁺ core that can be considered as a hybrid of the bent (butterfly) and planar dispositions of four metal ions seen previously in such compounds with transition metals. Complex 1 has been characterized by variable-temperature magnetic susceptibility studies, and by IR and variable-temperature ⁵⁷Fe Mössbauer spectroscopies. Magnetochemical data reveal a diamagnetic ground state (S=0) with antiferromagnetic body-body and body-wingtip interactions between the iron(III) ions of the butterfly core (J_bb=−11 cm⁻¹, J_wb=−70 cm⁻¹). Magnetochemical and Mössbauer studies on 1 show that its structural asymmetry has practically no influence on these properties compared with the more symmetric types.     

Further studies on the coordination chemistry of [Pt2(μ-S)2(PPh3)4] towards indium(III) substrates

The reactivity of the metalloligand [Pt₂(μ-S)₂(PPh₃)₄] towards a variety of indium(III) substrates has been explored. Reaction with excess In(NO₃)₃ and halide (KBr or NaI) gave the four-coordinate adducts [Pt₂(μ-S)₂(PPh₃)₄InX₂]⁺[InX₄]⁻ (X = Br, I). An X-ray structure determination on the iodo complex revealed a slightly distorted tetrahedral coordination geometry at indium. In contrast, reaction of [Pt₂(μ-S)₂(PPh₃)₄] with indium(III) chloride was more complex; the ion [Pt₂(μ-S)₂(PPh₃)₄InCl₂]⁺ was initially observed in solution (using ESI mass spectrometry), and isolated as its BPh₄⁻ salt. Analysis of [Pt₂(μ-S)₂(PPh₃)₄InCl₂]⁺[BPh₄]⁻ by ESI MS showed the parent cation when analysed in MeCN solution. However in solutions containing methanol, partial solvolysis occurred to give the di-indium species [{Pt₂(μ-S)₂(PPh₃)₄InCl(OMe)}₂]²⁺ (proposed to contain an In₂(μ-OMe)₂ unit with five-coordinate indium) and its fragment ion [Pt₂(μ-S)₂(PPh₃)₄InCl(OMe)]⁺. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with InCl₃·3H₂O, 8-hydroxyquinoline (HQ) and trimethylamine in methanol gave the adduct [Pt₂(μ-S)₂(PPh₃)₄InQ₂]⁺, isolated as its PF₆⁻ salt. The same cationic complex is formed when [Pt₂(μ-S)₂(PPh₃)₄] is reacted with InQ₃ in methanol, but in this case the product is contaminated with the mononuclear complex [(Ph₃P)₂PtQ]⁺ formed by disintegration of the trinuclear complex [Pt₂(μ-S)₂(PPh₃)₄InQ₂]⁺ with byproduct Q⁻. [(Ph₃P)₂PtQ]⁺BPh₄⁻ was independently prepared from cis-[PtCl₂(PPh₃)₂] and HQ/Me₃N, and is the first example of a platinum 8-hydroxyquinolinate complex containing phosphine ligands.     

Structural characterization, electrochemistry, and spectroelectrochemistry of trans-dioxorhenium(V) complex with 4-methoxypyridine, [ReO2(4-MeOpy)4]PF6, and characterization of [ReO2(4-MeOpy)4] generated electrochemically

Crystal structure of [ReO₂(4-MeOpy)₄][PF₆] (4-MeOpy = 4-methoxypyridine) complex has been examined by the single crystal X-ray analytical method. This complex shows a trans-dioxo geometry (average Re-O bond length = 1.766(2) Å) and its equatorial plane is occupied by four 4-MeOpy molecules (average Re-N bond length = 2.156(4) Å). Electrochemical reaction of [ReO₂(4-MeOpy)₄]⁺ in CH₃CN solution containing tetra-n-butylammonium perchlorate as a supporting electrolyte has been studied using cyclic voltammetry at 24 °C. Cyclic voltammograms show one redox couple around 0.65 V (E_pa) and 0.58 V (E_pc) [versus ferrocene/ferrocenium ion redox couple, (Fc/Fc⁺)]. Potential differences between two peaks (ΔE_p) at scan rates in the range from 0.01 to 0.10 V s⁻¹ are 65 mV, which is almost consistent with the theoretical ΔE_p value (59 mV) for the reversible one electron transfer reaction at 24 °C. The ratio of anodic peak currents to cathodic ones is 1.04 ± 0.03 and the (E_pa + E_pc)/2 value is constant, 0.613 ± 0.001 V versus Fc/Fc⁺, regardless of the scan rate. Spectroelectrochemical experiments have also been carried out by applying potentials from 0.40 to 0.77 V versus Fc/Fc⁺ with an optically transparent thin layer electrode. It was found that the UV-visible absorption spectra show clear isosbestic points at 228, 276, and 384 nm, and that the electron stoichiometry is evaluated as 1.03 from the Nernstian plot. These results indicate that the [ReO₂(4-MeOpy)₄]⁺ complex is oxidized reversibly to the [ReO₂(4-MeOpy)₄]²⁺ complex. Furthermore, it was clarified that the [ReO₂(4-MeOpy)₄]²⁺ in CH₃CN has the characteristic absorption bands at 236, 278, 330, 478, and 543 nm and their molar absorption coefficients are 4.3 × 10⁴, 4.5 × 10³, 1.0 × 10⁴, and 6.1 × 10³ M⁻¹ cm⁻¹ (M = mol dm⁻³), respectively.     

Synthesis, crystal structure and vibrational spectroscopy of a novel mixed ligands Ni(II) pentaborate: [Ni(C4H10N2)(C2H8N2)2][B5O6(OH)4]2

A novel organic-inorganic hybrid pentaborate [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂][B₅O₆(OH)₄]₂ has been synthesized by hydrothermal reaction and characterized by FT-IR, Raman spectroscopy, elemental analyses and DTA-TGA. Its crystal structure was determined from single crystal X-ray diffraction. The structure consists of isolated polyborate anion [B₅O₆(OH)₄]⁻ and nickel complex cation of [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺, in which the two kinds of ligands come from the decomposition of triethylenetriamine material. The [B₅O₆(OH)₄]⁻ units are connected to one another through hydrogen bonds, forming a three-dimensional framework with large channel along the a and c axes, in which the templating [Ni(C₄H₁₀N₂)(C₂H₈N₂)₂]²⁺ cations are located. The assignments of the record FT-IR absorption frequencies and Raman shifts were given.     

Hydrothermal synthesis and structural investigation of silver magnesium complex of benzenehexacarboxylic acid (mellitic acid), Ag2Mg2[C6(COO)6] · 8H2O with two-dimensional layered structure

Crystal and molecular structure of silver magnesium mellitate, Ag₂Mg₂[C₆(COO)₆] · 8H₂O, was synthesized hydrothermally and characterized by X-ray structure analysis. The complex crystallizes in the monoclinic system, space group P2/n, with unit cell dimensions of a=7.4347(2), b=9.9858(2), c=14.4248(3) Å, β=99.2429(5)°, V=1055.01(4) ų, and Z=2. The structure was solved and refined to R=0.036 (R_w=0.045) for 1707 independent reflections [I_o>2σ(I_o)]. The Ag cations are coordinated by six carboxylic oxygen atoms of mellitate anions with composition of [C₆(COO)₆]⁶⁻ on the (1 0 1) plane; each mellitate anion linking three neighboring Ag distorted trigonal prisms produces a two-dimensional layered structure parallel to (1 0 1). The Mg cations, which are coordinated by four water molecules and two carboxylic oxygen atoms, are intercalated between the two-dimensional layer stacks. The carboxylate group coordinated to Mg and Ag cations serve as a tridentate ligand in that structure. The number of water molecules incorporated into the mellitate compound is controlled mainly by ionic radii of metal cation in the structure. Furthermore, the ionic radii of metal cations in the mellitate compound play an essential role in arrangement of mellitate anions in the structure, whether as a one-dimensional infinite chain, a two-dimensional layered structure, or a three-dimensional framework structure.     

Synthesis and structural characterization of dinuclear iridium hydrido complex with 3,6-bis(2-pyridyl)tetrazine, [Ir2(H)4(PPh3)4(bptz)](PF6)2 · 4CH2Cl2

Reaction of the precursor Ir complex [Ir(H)₂(PPh₃)₂(Me₂CO)₂]PF₆ with 3,6-bis(2-pyridyl)tetrazine (bptz) in CH₂Cl₂ gave a novel dinuclear Ir hydrido complex [Ir₂(H)₄(PPh₃)₄(bptz)](PF₆)₂ · 4CH₂Cl₂. Crystallographic study described an interesting coordination environment having a π-π interaction and ¹H NMR study showed unique upfield shifts of pyridyl rings that are likely induced by the ring current effect of neighboring PPh₃ ligands.     

Heterometal cubane-type WFe3S4 and related clusters trigonally symmetrized with hydrotris(3,5-dimethylpyrazolyl)borate

The scope of formation and structures of tungsten-iron-sulfur clusters has been explored using reactions based on [(Tp*)WS₃]¹⁻ (1) as the ultimate precursor. The reaction system 1/FeCl₂/NaSEt/S affords the cubane cluster [(Tp*)WFe₃S₄Cl₃]¹⁻ (2), which with NaSEt is converted to [(Tp*)WFe₃S₄(SEt)₃]¹⁻ (3).Clusters 2 and 3 contain the cubane [WFe₃(μ₃-S)₄]³⁺ core.Complex 1 with FeCl₂/NaSEt forms [(Tp*)WFe₂S₃Cl₂(SEt)]¹⁻ (4) with the cuboidal [WFe₂(μ₂-S)₂(μ₃-S)(μ₂-SR)]²⁺ core.Treatment of 2 with excess Et₃P yields the edge-bridged double [(Tp*)₂W₂Fe₆S₈(PEt₃)₄] (5) with the [W₂Fe₆(μ₃-S)₆(μ₄-S)₂] core. Reaction of 2 with excess leads a mixture of products, from which [(Tp*)₂W₂Fe₅S₉Na(SH)(MeCN)]³⁻(6) was identified.This cluster, as closely related [(Tp)₂Mo₂Fe₆S₉(SH)₂]³⁻, exhibits a core topology [W₂Fe₅Na(μ₂-S)₂(μ₃-S)₆(μ₆-S)] very similar to the P^N cluster of nitrogenase. All reactions were carried out in acetonitrile. The structures of 2-6 were established crystallographically as Et₄N⁺ salts. In the cubane series, substitution of tungsten for molybdenum decreases the [MFe₃S₄]^3+/2+ redox potential by ca. 0.20 V but has a negligible effect on electron distribution. This work expands the small set of previously known weak-field W-Fe-S clusters, demonstrates the existence of tungsten-containing edge-bridged double cubanes and clusters with the P^N core topology, and introduces a new cuboidal core structure as found in 4 (Tp = hydrotris(pyrazolyl)borate, Tp* = hydrotris(3,5-dimethylpyrazolyl)borate).     

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.     

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.     

Use of a cubane-type Mo3CoS4 molecular cluster as paramagnetic unit in the synthesis of hybrid charge-transfer salts

Selective substitution of the chlorine atom coordinated to cobalt in the paramagnetic Mo₃(CoCl)S₄(dmpe)₃Cl₃ (dmpe = 1,2-bis(dimethylphosphanyl) ethane) complex with a S = 1/2 ground state has been achieved by iodine oxidation to afford the also paramagnetic [Mo₃(CoI)S₄(dmpe)₃Cl₃]I ([1]I) salt with a S = 1 ground state in almost quantitative yield. Replacement of chorine by iodine has no significant effect on the structural and electrochemical properties of the Mo₃CoS₄ system. Metathesis of the [1]I salt with the paramagnetic nickel anionic dithiolate [Ni(mnt)₂]⁻ (mnt = maleonitrilodithiolate) affords [1]₂[Ni(mnt)₂]. The stoichiometry evidenced by X-ray analysis reveals that reduction of the [Ni(mnt)₂]⁻ radical to the corresponding diamagnetic closed shell [Ni(mnt)₂]²⁻ dianion, presumably via dismutation, has occurred during the metathesis process. The crystal structure of [1]₂[Ni(mnt)₂] consists of [Ni(mnt)₂]²⁻ dianions sandwiched by two cluster 1⁺ cations which yield {1⁺·[Ni(mnt)₂]²⁻·1⁺} subunits arranged along the crystallographic c axis. Magnetic susceptibility measurements for [1]₂[Ni(mnt)₂] show a χT product of 0.99 emu K/mol largely unchanged in the 10-300 K range. This behavior agrees with the presence of an S = 1 cluster 1⁺ cation while the Ni(mnt)₂ moiety does not contribute to the paramagnetism of the sample.