Eight-connected coordination framework supported by tricopper(II) secondary building blocks

In a series of coordination polymers based upon 4,4′-bitriazole (btr) [Cu₃Cl₂(H₂O)₂(btr)₄]₂(ZnCl₄)₂(Cl₃ZnOZnCl₃), [Cu₃Cl₂(H₂O)₂(btr)₄](MCl₄)₂ (M = Cd; Hg), eight-connected metal-organic frameworks related to a CsCl (bcu) structure originate in the functionality of trinuclear copper/chloride ensembles bridged by the organic ligands. [Cu₃Cl₄(btr)₄]Cl₂ complex adopts simpler 1D polymeric structure also incorporating trinuclear copper/chloride clusters.     

Analysis of anisotropic effects in trinuclear metal carbonyl compounds by visualization of through-space NMR shielding

Through-space NMR shieldings were calculated for trinuclear metal-carbonyl compounds [M₃(CO)₁₂] (M = Fe, Ru, Os), employing the nucleus-independent chemical shift approach. The through-space shieldings were visualized as a contour plot of iso-chemical shielding surfaces, and were applied to quantify the overall anisotropic effect of the carbonyl groups, as well as to identify the influence of the transition metal on the scopes of the corresponding anisotropy cones. The shielding surfaces show that the anisotropic effect of the carbonyl groups at equatorial positions changes depending on the metal. This effect was associated with π–backdonation from the metal to the carbonyl groups in that position, in agreement with geometric data as well as calculated NMR parameters. Therefore, visualization of the through-space NMR shieldings of trinuclear metal-carbonyl compounds of group 8 is able to reflect the distinct arrangements of the carbonyl groups in these organometallic compounds.     

Metal cluster topology. 1. Osmium carbonyl clusters

Important theoretical approaches to metal cluster bonding including the Wade-Mingos skeletal electron pair method, the Teo topological electron count, the King-Rouvray graph theory derived method, and Lauher's extended Hückel calculations are shown to agree in their apparent skeletal electron counts for the most prevalent metal cluster polyhedra including the tetrahedron, the trigonal bipyramid (both ordinary and elongated), square pyramid, octahedron, bicapped tetrahedron, pentagonal bipyramid, and capped octahedron. The graph theory derived method is used to treat osmium carbonyl clusters containing from five to eleven osmium atoms. In this connection most osmium carbonyl clusters can be classified into the following types: (1) Clusters exhibiting edge- localized bonding containing multiple tetrahedral chambers (e.g., Os₅(CO)₁₆, Os₆(CO)₁₈, H₂Os₇(CO)₂₀ and HOs₈(CO)₂₂⁻); (2) Capped octahedral clusters derived from osmium carbonyl fragments of the type Os_6+p(CO)_19+2p (p = 0, 1, 2, and 4) (e.g., Os₆- (CO)₁₈²⁻, Os₇(CO)₂₁, Os₈(CO)₂₂²⁻, and H₄Os₁₀- (CO)₂₄²⁻). Other more unusual osmium carbonyl clusters such as the planar Os₆(CO)₁₇ [P(OCH₃)₃]₄, the Os₉ cluster [Os₉(CO)₂₁C₃H₂R]⁻, and the Os₁₁ cluster Os₁₁C(CO)₂₇²⁻ can also be treated satisfactorily by these methods. The importance of the number of ligands around isoelectronic Os_n systems in determining the cluster polyhedron is illustrated by the different cluster polyhedra found for each member of the following isoelectronic pairs: HOs₆- (CO)₁₈⁻/H₂Os₆(CO)₁₈. Os₇(CO)₂₁/H₂Os₇(CO)₂₀, Os₈(CO)₂₂²⁻/HOs₈(CO)₂₂⁻. The tendency for osmium carbonyl clusters frequently to form polyhedra exhibiting edge-localized rather than globally delocalized bonding relates to the facility for osmium carbonyl vertices to contribute more than three internal orbitals to the cluster bonding. In this way Wade's well-known analogy between boron hydride clusters and metal clusters, which assumes exactly three internal orbitals for each vertex atom, is frequently no longer followed in the case of osmium carbonyl clusters.     

Interactions of bis-[μ-chloro-chlorotricarbonylruthenium(II)] and poly-[μ-dichloro-dicarbonylruthenium(II)] with nucleosides

The interactions of dimeric complex bis-[μ-chloro-chlorotricarbonylruthenium(II)], [Ru(CO)₃Cl₂]₂, and the polymeric complex poly-[μ-dichlorodicarbonylruthenium(II)], [Ru(CO)₂Cl₂]_x, with nucleosides (Nucl) in a 1:1 Ru:Nucl molar ratio for the dimer and 1:2 Ru:Nucl for the polymer, resulted in formation of the monomeric mononucleoside [Ru(CO)₃(Nucl)Cl₂] and bis-nucleoside [Ru(CO)₂(Nucl)₂Cl₂] complexes, respectively. The dimer [Ru(CO)₃Cl₂]₂ also gave the ionic bis-nucleoside complexes [Ru(CO)₃(Nucl)₂Cl]Cl in the molar ratio 1:2 Ru:Nucl. The mononucleoside complexes are stable in solution while the bis-nucleoside complexes tend to lose one nucleoside in strong complexing solvents, probably by solvent substitution. The complexes [Ru(CO)₃(Nucl)Cl₂] and [Ru(CO)₂(Nucl)₂Cl₂] with one N(1)H ionizable imino proton undergo ionization in alkaline solution and the complexes [Ru(CO)₃(NuclH⁺)Cl] and [Ru(CO)₂(NuclH⁺)₂], respectively, were isolated. In these deprotonated complexes the nucleosides behave as bidentate ligands, while in the protonated ones they act as monodentate. All Complexes were characterized by elemental analyses and various spectroscopic methods.     

Synthesis of some mixed seven-coordinate complexes of the type [MI2(CO)3LL′] (M = Mo or W;L = pyridine or substituted pyridines; L′ = PPh3, AsPh3 or SbPh3)

The seven-coordinate bisacetonitrile complexes [MI₂(CO)₃(NCMe)₂] (M = Mo or W) react with L′ (L′ = PPh₃, AsPh₃ or SbPh₃) in CH₂Cl₂ at room temperature to give [MI₂(CO)₃(NCMe)L′] which when reacted in situ with L (L = pyridine or substituted pyridines) affords good yields of 28 mixed seven-coordinate complexes [MI₂(CO)₃LL′]. It is likely these reactions occur via successive dissociative displacements of two acetonitrile ligands.     

Novel [Ru(polypyridine)(CO)2Cl2] and [Ru(polypyridine)2(CO)Cl]-type complexes: Characterizing the effects of introducing azopyridyl ligands by electrochemical, spectroscopic and crystallographic measurements

The reaction of ruthenium carbonyl polymer ([Ru(CO)₂Cl₂]_n) with azopyridyl compounds (2,2′-azobispyridine; apy or 2-phenylazopyridine; pap) generated new complexes, [Ru(azo)(CO)₂Cl₂] (azo = apy, pap). [Ru(apy)(CO)₂Cl₂] underwent photodecarbonylation to give a chloro-bridged dimer complex, whereas the corresponding pap complex ([Ru(pap)(CO)₂Cl₂]) was not converted to a dimer. The reactions of the chloro-bridged dimer containing the bpy ligand (bpy = 2,2′-bipyridine) with either apy or pap resulted in the formation of mixed polypyridyl complexes, [Ru(azo)(bpy)(CO)Cl]⁺. The novel complexes containing azo ligands were characterized by various spectroscopic measurements including the determination of X-ray crystallographic structures. Both [Ru(azo)(CO)₂Cl₂] complexes have two CO groups in a cis position to each other and two chlorides in a trans position. The azo groups are situated cis to the CO ligand in [Ru(azo)(bpy)(CO)Cl]⁺. All complexes have azo N-N bond lengths of 1.26-1.29 Å. The complexes exhibited azo-based two-electron reduction processes in electrochemical measurements. The effects of introducing azopyridyl ligands to the ruthenium carbonyl complexes were examined by ligand-based redox potentials, stretching frequencies and force constants of CO groups and bond parameters around Ru-CO moieties.     

The reaction of [Os6(CO)18] with [(SPPh2)2NH]: Facile rearrangement of the metal framework

The reaction of [Os₆(CO)₁₈] 1 with [(SPPh₂)₂NH] in the presence of Me₃NO produces a purple compound characterized spectroscopically and by X-ray crystallography, as [HOs₆(CO)₁₇(SPPh₂)₂N] 2. The structure shows the hexanuclear fragment to have suffered a geometrical rearrangement to give a metal framework that can be described as an edge-bridged tetrahedron with an additional terminal osmium atom bonded to one of the bridged metal atoms. The ligand acts as a bimetallic tetraconnective unit through both sulphur atoms between two non-bonded osmium atoms.     

The reactivity of ruthenium mono(bipyridine) carbonyl complexes in an alcoholic solution of alkali metal carbonates

Chlorine containing ruthenium bipyridine carbonyl compounds react readily in dilute alkaline solutions under a CO atmosphere affording a poorly soluble and air sensitive product that is suggested to have a polymeric nature. Various analysis methods (MS and TPD) were used in the characterisation of the product. The replacement of the axial chloride ligands in trans(Cl), cis(CO)[Ru(bpy)(CO)₂Cl₂] and [Ru(bpy)(CO)₂Cl]₂ is proposed to be the initial step in the polymerisation. The replacement of chlorides in methanolic solution was confirmed by isolating and characterising the dimeric intermediate [Ru(bpy)(CO)₂(COOCH₃)]₂.     

Generation of trans-dioxoruthenium(VI) porphyrins: A photochemical approach

trans-Dioxoruthenium(VI) porphyrin complexes have been developed as one of the best-characterized model systems for heme-containing enzymes. Traditionally, this type of compounds can be prepared by oxidation of ruthenium(II) precursors with peroxyacids and other terminal oxidants under different conditions, depending on the porphyrin ligands. In this work, a new photochemical generation of trans-dioxoruthenium(VI) porphyrins has been developed by extension of the known photo-induced ligand cleavage reactions. Refluxing ruthenium(II) carbonyl porphyrins [Ru^II(Por)(CO)] in carbon tetrachloride afforded dichlororuthenium(IV) complexes [Ru^IV(Por)Cl₂]. Facile exchange of the counterions in [Ru^IV(Por)Cl₂] with Ag(ClO₃) or Ag(BrO₃) gave the corresponding dichlorate [Ru^IV(Por)(ClO₃)₂] or dibromate [Ru^IV(Por)(BrO₃)₂] salts. Visible-light photolysis of the photo-labile porphyrin-ruthenium(IV) dichlorates or dibromates resulted in homolytic cleavage of the two O-Cl or O-Br bonds in the axial ligands to produce trans-dioxoruthenium(IV) species [Ru^VI(Por)O₂] bearing different porphyrin ligands.     

Metal cluster topology. 4. Rhodium carbonyl clusters having fused polyhedra

Previously discussed topological models of metal cluster bonding are now extended to the treatment of anionic rhodium carbonyl clusters having structures consisting of fused polyhedra. Examples of such rhodium carbonyl clusters built from fused octahedra include the ‘biphenyl analogue’ [Rh₁₂(CO)₃₀]⁻², the ‘face-sharing naphthalene analogue’ [Rh₉- (CO)₁₉]³⁻, and the ‘perinaphthene analogue’, [Rh₁₁- (CO)₂₃]³⁻. More complicated anionic rhodium carbonyl clusters treated in this paper include the [Rh₁₃(CO)₂₄H_5−q]^q− anions (q = 2, 3, 4) having an Rh₁₃ centered cuboctahedron, the [Rh₁₄(CO)₂₅- H_4−q]^q− (q = 3,4) and [Rh₁₄(CO)₂₆]²⁻ anions based on a centered pentacapped cube, the [Rh₁₅- (CO)₃₀]³⁻ anion having an Rh₁₅ centered 14-vertex deltahedron, the [Rh₁₅(CO)₂₇]³⁻ anion having a tricapped centered 11-vertex polyhedron, the [Rh₁₇- (CO)₃₀]³⁻ anion having a tetracapped centered cuboctahedron, and the [Rh₂₂(CO)₃₇]⁴⁻ anion having a hexacapped centered cuboctahedron fused to an octahedron so that the octahedron and the cuboctahedron share a triangular face. Analyses of the bonding topologies in [Rh₉(CO)₁₉]³⁻, [Rh₁₇- (CO)₃₀]³⁻, and [Rh₂₂(CO)₃₇]⁴⁻ indicate that a polyhedral network containing several fused globally delocalized polyhedral chambers will not necessarily have a multicenter core bond in the center of each such polyhedral chamber. This observation is of potential importance in extending topological models of metal cluster bonding to bulk metals.     

Synthesis and spectroscopic properties of some new seven-coordinate thioacetamide complexes of molybdenum(II) and tungsten(II)

The compounds [MI₂(CO)₃(NCMe)₂] (M = Mo or W) react with one equivalent of SC(NH₂)Me in CH₂Cl₂ at room temperature to initially give the acetonitrile substituted products [MI₂(CO)₃(NCMe)- {SC(NH₂)Me}] which was isolated for M = W. However, the molybdenum complex rapidly dimerizes with loss of acetonitrile to give the iodide-bridged compound [Mo(σ-I)I(CO)₃ {SC(NH₂)Me}]₂. The tungsten complex does not appear to dimerize, even after stirring at room temperature for 72 h in CH₂Cl₂. Two equivalents of thioacetamide react with [MI₂- (CO)₃(NCMe)₂] in CH₂Cl₂ at room temperature to give the new bisthioacetamide compounds [MI₂- (CO)₃{SC(NH₂)Me}₂] via displacement of the labile acetonitrile ligands. The low temperature (−70 °C) ¹³C NMR spectrum of [WI₂(CO)₃{SC(NH₂)Me}₂] indicates that the geometry of the complex is capped octahedral with a carbonyl ligand in the unique capping position.     

Iron-nickel mixed metal nitrido clusters: Synthesis and solid state structure of the anions [HFe5NiN(CO)14] and [HFe4Ni2N(CO)13]

The two clusters [HFe₅NiN(CO)₁₄]²⁻ (1) and [HFe₄Ni₂N(CO)₁₃]²⁻ (2) were obtained by reaction of [Fe₄N(CO)₁₂]⁻ and [Ni₆(CO)₁₂]²⁻ in refluxing MeCN and EtCN, respectively, along with other Fe-Ni mixed metal clusters. Their solid state structures were determined on the [PPh₄]⁺ salts, and both have an octahedral metal cage, containing an interstitial nitrogen atom. The two Ni atoms in 2 are cis, with a Ni-Ni separation of 2.724(1) Å. The two anions have different stereochemistry of the carbonyl ligands: in 1, five CO’s are semi-bridging, and the remaining nine are terminal; in 2 there are three asymmetric bridging and ten terminal ligands (two for each iron and one for each nickel). The hydride ligands were located in the final difference maps, both bridging a Ni-Fe edge of the clusters but, thanks to the better quality of the diffraction data, the metal-hydrogen distances were refined only in 2. In this cluster, the Fe-H and Ni-H bond lengths are 1.77(2) and 1.79(2) Å, respectively.     

One-step synthesis and reduction of triphenylphosphine carbonyl palladium clusters of variable nuclearities

Heteroleptic triphenylphosphine carbonyl palladium clusters of different nuclearities were prepared under mild conditions by only varying the amount of ligand (PPh₃) used in the synthesis: three different clusters were successfully isolated after CO bubbling in a solution of [Pd₂(dba)₃] (dba = dibenzylideneacetone) with 3, 1 or 0.5 equiv of PPh₃, which led, respectively, to [Pd₄(CO)₅(PPh₃)₄] (1), [Pd₁₀(CO)₁₂(PPh₃)₆] (2) and [Pd_n(CO)_x(PPh₃)_y] (3) (n ≈ 24). The molecular structures of compounds 1 and 2 were determined by X-ray crystallography. The metal cores in these compounds were shown to consist in a butterfly for 1 and a bridged octahedron for 2. Compound 3 was shown to be at the boundary between molecular clusters and colloidal particles with tentative formulation arising from characterization data. These three clusters and the known [Pd₁₀(CO)₁₂(PBu₃)₆] and [Pd₁₂(CO)₁₅(PBu₃)₇] were submitted to NaBH₄ reduction. The Pd₄ cluster 1 did not react. The colloidal Pd_n species led to no isolable product. By contrast, the two Pd₁₀ and the Pd₁₂ clusters led to reduction products, isolated as salts. In the case of the reduced Pd₁₂ cluster, its structure was resolved by X-ray crystallography: the metal core consists of a face-capped octahedron. The reduced species reacted readily with Au(PPh₃)⁺, confirming their anionic nature.     

Trinuclear copper(II) complexes of bis(acylhydrazone) ligands. Structural analysis and magnetic properties of a sulfato-bridged hexanuclear dimer

The synthesis and spectroscopic characterization of the new symmetric, ligand bis(salicylaldehyde)methyliminodiacetylhydrazone (H₄MeImds) is reported. The reactions of H₄ MeImds with copper(II) chloride, nitrate and sulfate give trinuclear metal complexes of formula Cu₃(MeImds)Cl₂ · CHCl₃ · H₂O, Cu₃(MeImds)(NO₃)₂ · 2H₂O and Cu₃(MeImds)(SO₄) · 8H₂O; the trinuclear species are obtained in spite of the used metal:ligand molar ratio. The X-ray crystal structure of [Cu₃(MeImds)(SO₄)(H₂O)₃] · 5H₂O is determined; it consists of linear units, with the nonadentate ligand bound to three copper ions. The trimetallic units are bridged via sulfate anions to give hexanuclear dimers with an imposed centre of symmetry. The magnetic properties of [Cu₃(MeImds)(SO₄)(H₂O)₃] · 5H₂O are characterized by a significant antiferromagnetic coupling within the trimetallic units and by a weak antiferromagnetic coupling between them. The analogous trinuclear copper(II) complexes Cu₃(HImds)Cl₂ · H₂O and Cu₃(HImds)(SO₄) · 4H₂O (H₅Imds, bis(salicylaldehyde)iminodiacetylhydrazone) were also prepared and spectroscopically characterized.     

Spectrophotometric kinetic study and analytical implications of the glucose oxidase-catalyzed reduction of [MIII(LL)2Cl2]+ complexes by d-glucose (M=Os and Ru, LL=2,2′-bipyridine and 1,10-phenanthroline type ligands)

 Glucose oxidase-catalyzed reduction of cis[M^III (LL)₂Cl₂]⁺ (M=Os and Ru) complexes to cis[M^II (LL)₂Cl₂] (LL=2,2′-bipyridine and 1,10-phenanthroline type ligands) by d-glucose is a first-order process in the complex and the enzyme in aqueous buffered solution. The reaction follows MichaelisMenten kinetics in d-glucose and the rate is independent of d-glucose concentration above 0.03 M. The reactivity decreases in the series [Ru(bpy)₂Cl₂]⁺ > [Os(phen)₂Cl₂]⁺ > [Os(4,4′-Me₂bpy)₂Cl₂]⁺ > [Os(4,7Me₂phen)₂Cl₂]⁺. The measured second-order rate constant for the oxidation of reduced glucose oxidase by [Os(phen)₂Cl₂]⁺ in air equals 1.2×10⁵ M^–1 s^–1 at pH 6.7, [d-glucose] 0.05 M, and 25  °C, which is ca. 20% less than that when the reaction solutions are purged with argon. In the case of [Ru(bpy)₂Cl₂]⁺ the rate constant equals 1.8×10⁵ M^–1 s^–1 under similar conditions in air, showing higher reactivity of Ru complexes compared with Os ones. The reduction is pH-dependent with a maximum around 7. Added for solubilization of poorly soluble metal complexes, surfactants decrease the rates of the enzymatic reaction. The retardation effect increases in the series: cetyltrimethylammonium bromide < Triton X-100 < sodium dodecyl sulfate, i.e. on going from positively charged to neutral and then to negatively charged surfactants. The behavior of the Os^III and Ru^III complexes toward reduced glucose oxidase contrasts to that of recently studied ferricenium cations. As opposed to the latter, the former do not show kinetically meaningful binding with the enzyme, and the Michaelis kinetics typical of the ferricenium case is not realized for the Os^III, and Ru^III species. The systems Os^III- or Ru^III-glucose oxidase are convenient for routine "one pot" spectrophotometric monitoring of the d-glucose content in samples, since the metal reduction to M^II is accompanied by a strong increase in absorbance in the visible spectral region. Received: 1 July 1998 / Accepted: 13 January 1999     

Photochemical synthesis method of tungsten(II) complexes [WCl2(CO)3PPh3)2] and [WCl2(CO)2(dppe)]

The photochemical oxidation reaction of W(CO)₆ to [W(CO)₄Cl₂]₂ with CCl₄ was applied in the synthesis of [WCl₂(CO)₃(PPh₃)₂] and [WCl₂(CO)₂₋- (dppe)].     

A bicarbonate bridged diruthenium(I) complex: Key evidence for the decarboxylation step in the base-assisted reduction of Ru2Cl4(CO)6

Base-assisted reduction of [Ru(CO)₃Cl₂]₂ in the presence of NP-Me₂ (2,7-dimethyl-1,8-naphthyridine) in thf provides an unsupported diruthenium(I) complex [Ru₂(CO)₄Cl₂(NP-Me₂)₂] (1). Two NP-Me₂ and four carbonyls bind at equatorial positions and two chlorides occupy sites trans to the Ru-Ru single bond. Reaction of [Ru(CO)₃Cl₂]₂, TlOTf, KOH and NP-Me₂ in acetonitrile, in a sealed container, affords a bicarbonate bridged diruthenium(I) complex [Ru₂(CO)₂(μ-CO)₂(μ-O₂COH)(NP-Me₂)₂](OTf) (2). The in situ generated CO₂ is the source for bicarbonate under basic reaction medium. Isolation of 2 validates the decarboxylation step in the base-assisted reduction of [Ru^II(CO)₃Cl₂]₂ → [Ru^I₂(CO)₄]²⁺.     

Synthesis, characterization and luminescence property of heterobimetallic trinuclear Mo(W)-Ag-S clusters containing 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodecaborane

Reactions of (NH₄)₂MS₄ or (NH₄)₂MOS₃ (M = Mo, W) with AgSCN and closo carborane diphosphine ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ (L) in CH₂Cl₂ yielded four heterobimetallic trinuclear Mo(W)-Ag-S clusters: [Ag₂MoS₄L₂] (1), [Ag₂WS₄L₂] (2), [Ag₂MoOS₃L₂] (3) and [Ag₂WS₄L₂] (4), respectively. All the new clusters have been characterized by elemental analysis, FT-IR, UV-Vis, ¹H and ¹³C NMR spectroscopy and their molecular structures (except for 3) were further confirmed by single-crystal X-ray diffraction. X-ray crystal structure analysis showed that the closo carborane diphosphine ligand was coordinated bidentately to Ag(I) atom through its two phosphorus atoms, resulting in a stable five-member chelating ring between the diphosphine ligand and the metal. The coordination sphere of the central M atom, as well as all the Ag atoms, was tetrahedron. The skeletons of these clusters could be classified into two types: with (NH₄)₂MS₄, the three metal atoms (two Ag atoms and one M atom) are in a linear conformation, while with (NH₄)₂MOS₃, the conformation of the heterobimetallic trinuclear cluster is butterfly shaped. The luminescence properties of the clusters were investigated in CH₂Cl₂ solution at room temperature and for the first time the butterfly-shaped Ag-W-S cluster containing the Ag₂WS₄ core has been proved to show luminescence property.     

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.     

Different reaction behaviour of molybdenum and tungsten - Reactions of the dichloro dioxo dimethyl-bispyridine complexes with thiophenolate

The reaction of the metal complexes MO₂Cl₂(mebipy) (M = Mo, W) with two equivalents thiophenol by the exact same procedure leads to two different products for molybdenum [Mo₂O₄(SPh)₂(mebipy)₂] and tungsten [WO₂(SPh)₂(mebipy)]. To understand why this is the case the redox potentials of the starting materials were measured showing that the redox potential for thiophenol is lower than the redox potentials (M^V ↔ M^VI) for both of the metal precursors. A reduction of the metal and oxidation of the sulfur should be possible for both reactions but occurs only for the molybdenum compound. Theoretical calculations show that different metal-sulfur bond strengths are as well and equally responsible for the differing reaction behaviour as are the redox potentials.