Zur Nucleophilie des sterisch anspruchsvollen Basenanions von Lithiumdiisopropylamid beim Protonenersatz gegen das isolobale AuPPh3-Kation in [(μ-H)(μ-PPh2) (CO)8Re2]

Nucleophilic Property of the Bulk Anion of the Base Lithium diisopropylamide at the Proton Exchange vs. the Isolobal AuPPh₃ Cation in [(μ-H) (μ-PPh₂) (CO)₈Re₂] The proton exchange in the starting material [(μ-H)(μ-PPh₂)(CO)₈Re₂] vs. the isolobal [AuPPh₃]⁺ cation when reacted with the steric expansive base LDA depending on reaction temperature leads to the three-membered metal ring substance [(μ-PPh₂)(CO)₈Re₂(AuPPh₃)] or the metallatetrahedron complex [(μ-C-(N i-Prop₂)O)(μ-PPh₂)(CO)₆Re₂(AuPPh₃)₂]. The tetrahedral cluster compound obtained through the nucleophilic property of LDA shows by means of cyclic voltammetry a reversible and a irreversible one-electron transfer redox step. The single crystal X-ray analysis of the compound with a tetrahedral Au₂Re₂ core gives following values of metal-metal bond lengths: Re? Re 312.2(2) pm, Au? Au 270.9(2) pm, and Au? Re 297.7(2) pm. The acyl diisopropylamido groups bridging the Re? Re bond is planar.     

Dynamic Permutational Isomerism in a closo‐Cluster

Permutational isomers of trigonal bipyramidal [W₂RhIr₂(CO)₉(η⁵‐C₅H₅)₂(η⁵‐C₅HMe₄)] result from competitive capping of either a W₂Ir or a WIr₂ face of the tetrahedral cluster [W₂Ir₂(CO)₁₀(η⁵‐C₅H₅)₂] from its reaction with [Rh(CO)₂(η⁵‐C₅HMe₄)]. The permutational isomers slowly interconvert in solution by a cluster metal vertex exchange that is proposed to proceed by Rh?Ir and Rh?W bond cleavage and reformation, and via the intermediacy of an edge‐bridged tetrahedral transition state. The permutational isomers display differing chemical and physical properties: replacement of CO by PPh₃ occurs at one permutational isomer only, while the isomers display distinct optical power limiting behavior.     

Syntheses of some mixed AuOs and PtOs clusters and the X-ray structure of [Os4H2(CO)12(AuPPh3)2]

Some reactions of [Os₄H₃(CO)₁₂AuPR₃] (R = Et, Ph) resulting in the formation of [Os₄H₂(CO)₁₂(AuPR₃)₂] are presented. A single-crystal X-ray structure of [Os₄H₂(CO)₁₂(AuPPh₃)₂] is reported and reveals a novel Ph₃PAuAuPPh₃ unit asymmetrically bridging one edge of an Os₄ tetrahedron, the first example of a mixed gold-metal carbonyl cluster with an AuAu bond.     

Synthese und Kristallstruktur von (C5H5)Mo(CO)3(AuPPh3) und [(C5H5)Mo(CO)2(AuPPh3)4]PF6

Synthesis and Crystal Structure of (C₅H₅)Mo(CO)₃(AuPPh₃) and [(C₅H₅)Mo(CO)₂(AuPPh₃)₄]PF₆ CpMo(CO)₃(AuPPh₃) is obtained by the reaction of Li[CpMo(CO)₃] with Ph₃PAuCl at ?95°C in CH₂Cl₂. It crystallizes in the monoclinic space group C2/c with a = 2625.1(7), b = 883.2(1), c = 2328.4(7) pm, β = 116.39(1)° und Z = 8. In the complex the AuPPh₃ group is coordinated to the CpMo(CO)₃ fragment with a Au? Mo bond of 271,0 pm. The Mo atom thus achieves a square pyramidal coordination with the center of the Cp ring in apical position. CpMo(CO)₃(AuPPh₃) reacts under uv irradiation with an excess of Ph₃PAuN₃ to afford the cluster cation [CpMo(CO)₂(AuPPh₃)₄]⁺. It crystallizes as [CpMo(CO)₂(AuPPh₃)₄]PF₆ · 2 CH₂Cl₂ in the orthorhombic space group P2₁2₁2₁ with a = 1553.9(1), b = 1793.8(2), c = 2809.8(7) pm und Z = 4. The five metal atoms form a trigonal bipyramidal cluster skeleton with the Mo atom in equatorial position. The Mo? Au distances range from 275.5 to 280.8 pm, and the Au? Au distances are between 281.2 and 285.6 pm.     

Iridium Cluster Chemistry: The Synthesis and the Solid State Structures of [HIr5(CO)12]2− and [HIr4(CO)10PPh3]−

The cluster [HIr₅(CO)₁₂]^2- (1) was prepared by condensation of [HIr₄(CO)₁₁]^- and [Ir(CO)₄]^- (molar ratio 1:1) in refluxing THF, with almost quantitative yields. Its solid state structure was determined by X-ray diffraction at low temperature on the salt [PPh₃CH₂Ph]₂[HIr₅(CO)₁₂]. The metal atoms define a trigonal bipyramidal arrangement. The hydride ligand was located indirectly as a bridge between apical and equatorial metal atoms. The phosphine-substituted cluster [HIr₄(CO)₁₀PPh₃]^- (2) was synthetized by CO displacement on [HIr₄(CO)₁₁]^-, in THF at room temperature. This reaction is selective, with no traces of polysubstitution products. In the solid state, the hydride and the triphenylphosphine are axially bound on basal iridium atoms; the terminal hydrogen atom was directly located by X-ray analysis at a Ir–H distance of 1.57(9) Å. On the contrary, two isomers are present in THF solution, and they interconvert rapidly at room temperature, as shown by¹H and ³¹P NMR spectra.     

[Fec3(μ3-CR)(CO)10]− Cluster anions as building blocks for the synthesis of mixed-metal clusters: II. Synthesis of HFe3Rh(μ4-η2-CCHR)(CO)11 clusters (R = H or C6H5) and study of their catalytic activity (R = C6H5) under hydroformylation and hydrogenation conditions

The mixed-metal vinylidene clusters HFe₃Rh(CO)₁₁(CCHR) (R = H, C₆H₅) have been synthesized via the reaction of [HFe₃(CO)₃CCHR][P(C₆H₅)₄] with [RhCl(CO)₂]₂ in the presence of a thallium salt. The reaction initially gives the [Fe₃Rh(CO)₁₁]CCHR][P(C₆H₅)₄] cluster which leads to the final products by protonation. Spectroscopic data indicate a μ₄-η² mode of bonding for the vinylidene ligand. A structure with a Fe₃Rh core in a butterfly configuration and in which the rhodium atom occupy a wing-tip site is proposed. The catalytic activity of HFe₃Rh(CO)₁₁(CCH(C₆H₅)) (80% yield) has been checked in hydroformylation and hydrogenation. In hydroformylation the cluster shows the same activity as Rh₄(CO)₁₂, whereas in hydrogenation the mixed-metal system shows specific activity; isomerization of 1-heptene to cis and trans 2-heptene takes place with no more than 14% heptane formation. The cluster is broken down during the catalysis, and some H₃Fe₃CO)₉(μ₃-CCH₂(C₆H₅)) is formed. The latter cluster is not an active catalyst, and under the same conditions use of Rh₄(CO)₁₂ results mainly in hydrogenation of 1-heptene. These observations suggest that the active species is a mixed iron-rhodium system.     

Photochemische Synthese von Eisencarbonylclustern

Zusammenfassung Die UV-spektroskopische Analyse der Spektren wäßrigäthanol. Lösungen von Pentacarbonyleisen während der Bestrahlung zeigt das Auftreten des Ions Hydrogen-undecacarbonyltriferrat [HFe₃(CO)₁₁]^–. Aus Tetraarylphosphoniumbromiden und Pentacarbonyleisen in Äthanol können bei 10–15°C photochemisch Salze des Typs [PR₄]⁺[HFe₃(CO)₁₁]^– hergestellt werden. Die Röntgenphotoelektronenspektren (ESCA-Spektren) des Eisenclusters [HFe₃(CO)₁₁]^– enthalten für dasL _III-Niveau (2p_3/2) des Eisens zwei Emissionsmaxima, deren Auftreten im Einklang steht mit dem aus den Röntgenstrukturanalysen undMößbauerspektren abzuleitenden Vorhandensein zweier chemisch nicht äquivalenter Arten von Eisenatomen in diesen Fe₃-Einheiten.

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Photochemical synthesis of iron-carbonyl clusters

The UV-spectroscopic analyses of the spectra of aqueousethanolic solutions of pentacarbonyl iron during irradiation show the appearance of the ion of hydrogen-undecacarbonyltri-ferrate [HFe₃(CO)₁₁]^–. From tetraarylphosphonium bromides and pentacarbonyl iron in ethanol salts of the type [PR₄]⁺[HFe₃(CO)₁₁]^– were prepared photochemically within the temperature of 10–15°C. The X-ray photoelectron spectra (ESCA-spectra) of the cluster [HFe₃(CO)₁₁]^– contains two maxima of emission from theL _III-level (2p_3/2) of iron. The appearance of these maxima confirm the existence of two chemically different kind of iron atoms in the Fe₃-unit of these clusters. A fact, which is known from X-ray analysis andMößbauer spectroscopy.

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Mit 4 Abbildungen

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Herrn Prof. Dr.F. Asinger zum 65. Geburtstag gewidmet.     

Synthesis and structural characterization of the first transition metal cluster containing a PPh2AuPPh3 ligand,Ir4(CO)8(μ-CO)3(PPh2AuPPh3), and its conversion into Ir4(CO)9(μ-CO)(μ-PPh2)(μ-AuPPh3)

Deprotonation of Ir₄(CO)₁₁PPh₂H (1) in the presence of [AuPPh₃][PF₆] yields the novel species Ir₄(CO)₁₁(PPh₂AuPPh₃) (2), which possesses a tetrahedral framework bearing a terminally bound PPh₂AuPPh₃ ligand. When heated in toluene, 2 is converted into the phosphido species Ir₄(CO)₁₀(μ-PPh₂)(μ-AuPPh₃).     

New PF3 and Carbonyl Chemistry of Tantalum

Reduction of [TaCl₅] by six equivalents of alkali metal naphthalenide in 1,2-dimethoxyethane at −60°C followed by treatment with gaseous PF₃ provides the first homoleptic phosphane complex containing tantalum in the −1 oxidation state, [Ta(PF₃)₆]⁻. This can be protonated by concentrated sulfuric acid to yield the previously unknown highly acidic and volatile hydride [HTa(PF₃)₆]. An improved normal-pressure synthesis of [Ta(CO)₆]⁻ is described. Reduction of the latter species by sodium in liquid ammonia gives the carbonyl trianion [Ta(CO)₅]³⁻ which undergoes monoprotonation and stannylation to form [HTa(CO)₅]²⁻ and [Ph₃SnTa(CO)₅]²⁻, respectively. The hydride is a useful precursor to [(Ph₃PAu)₃Ta(CO)₅], the only known gold cluster of tantalum.     

Hydrierung aromatischer Nitrile auf dem Fe3(CO)9-Cluster

Hydrogenation of Aromatic Nitriles on the Fe₃(CO)₉ Cluster The μ₃-nitrile bridged clusters Fe₃(CO)₉(μ₃-η²-N≡CR) ( 3 , R = phenyl, p-tolyl, p-anisyl) consume hydrogen upon heating in solution with formation of the acimidoyl- and the alkylideneimido-bridged clusters HFe₃(CO)₉(μ₃-η²-HN=CR) ( 1 ) and HFe₃(CO)₉(μ₃-η²-N=CHR) ( 2 ). These can be obtained in a better way by successive H⁺ and H^– addition with NaBH₄ and H₃PO₄. HFe₃(CO)₉(μ₃-η²-N=CHR) ( 2 ) adds P(OMe)₃ with concomitant hydrogen migration to form Fe₃(CO)₉P(OMe)₃(μ₃-η¹-N–CH₂R) ( 6 ). The phosphite-substituted cluster Fe₃(CO)₈P(OMe)₃(μ₃-η²-N≡CPh) ( 5 a ) on the other hand is converted by the H⁺/H^– addition to the products HFe₃(CO)₈P(OMe)₃(μ₃-η²-HN=CPh) ( 7 a ) and HFe₃(CO)₈P(OMe)₃(μ₃-η²-N=CHPh) ( 8 a ).     

A dihydrogen bond between a bridging hydride and the NH proton of a coordinated dimethylamine: solid state, solution and theoretical characterization

The addition of one equivalent of dimethylamine (DMA) to the 44 valence-electron triangular cluster anion [Re₃(μ₃-H)(μ-H)₃(CO)₉]⁻ (1) affords the novel unsaturated derivative [Re₃(μ-H)₄(CO)₉(DMA)]⁻ (2, 46 valence electrons) which contains a dimethylamine molecule terminally coordinated to a cluster vertex. Theoretical calculations (DFT) reveal that in the more stable conformation the dimethylamine NH proton is directed towards the hydride bridging the opposite cluster edge in syn position, the close proximity of the ligands bound to the cluster surface allowing the formation of an unconventional N-H ? (μ-H)Re₂ hydrogen bond. The presence of this conformation in the solid state has been proven by an X-ray structural analysis of crystalline [PPh₄]2. Spectroscopic evidences (IR and NMR) indicate that the dihydrogen bond is maintained also in solution and, by the evaluation of the proton spin-lattice relaxation rates at variable temperature, a good estimate of the H ? H distance in solution has been determined.     

Pentaruthenium-Based Borides Stabilized by Gold(I) Phosphine Units

The pentaruthenium boride cluster [Ru₅(CO)₁₅B]^- has been prepared from [Ru₆(CO)₁₇B]^- but is unstable. The Ru₅(CO)₁₅B-core can be stabilized in the form of [Ru₅(CO)₁₅BAuPR₃] (R=Ph or o-tolyl). Addition of [(Ph₃PAu)₃O][BF₄] to [Ru₅(CO)₁₅B]^- gives the trigold derivative [Ru₅(CO)₁₄B(AuPPh₃)₃] which possesses an novel core structure.     

Controlled Expansion of a Strong‐Field Iron Nitride Cluster: Multi‐Site Ligand Substitution as a Strategy for Activating Interstitial Nitride Nucleophilicity

Multimetallic clusters have long been investigated as molecular surrogates for reactive sites on metal surfaces. In the case of the μ₄‐nitrido cluster [Fe₄(μ₄‐N)(CO)₁₂]^?, this analogy is limited owing to the electron‐withdrawing effect of carbonyl ligands on the iron nitride core. Described here is the synthesis and reactivity of [Fe₄(μ₄‐N)(CO)₈(CNAr^Mes2)₄]^?, an electron‐rich analogue of [Fe₄(μ₄‐N)(CO)₁₂]^?, where the interstitial nitride displays significant nucleophilicity. This characteristic enables rational expansion with main‐group and transition‐metal centers to yield unsaturated sites. The resulting clusters display surface‐like reactivity through coordination‐sphere‐dependent atom rearrangement and metal–metal cooperativity.     

Structure and dynamic properties of substituted carbonylhydride clusters H2RuOs3(CO)13 and H4Ru4(CO)12 containing functionalized phosphines

The derivatives of the H₂RuOs₃(CO)₁₃ and H₄Ru₄(CO)₁₂ carbonylhydride clusters containing functionalized (including chiral) phosphines were synthesized. The solid-state structure of H₂RuOs₃(CO)₁₂(Ph₂P(C₄H₃S)) was determined by X-ray diffraction analysis. The structures of other compounds in solution were determined using IR and ¹H and ³¹P NMR spectroscopy. A study of the temperature dependences of the ¹H NMR spectra of the phosphine-substituted tetrahedral clusters along with the analysis of literature data for their analogs showed that compounds of this type exist in solution as an equilibrium mixture of isomers, which differ in arrangement of the hydride ligands at the cluster skeleton. Interconversion of the isomeric forms is due to migration of the hydride ligands over the cluster skeleton. A general model for this dynamic process was proposed. The model is consistent with both our data and earlier results of other authors. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1294–1301, July, 2007.     

Synthese und Strukturen von [Cu8As3(AsSiMe3)2(dppb)4]+‐[Cu{As2(SiMe3)2}{As4(SiMe3)4}]‐, [Cu8As3(AsSiMe3)2(dppb)4]+‐[Cu{As(SiMe3)2}2]‐ und [Cu10(Sb3)2(SbSiMe3)2(dppm)6]

The reaction of CuCl, LiAs(SiMe₃)₂ and dppb (Bis(diphenylphosphino)butane) leads to the formation of ionic cluster complexes. Depending on the reaction conditions one can isolate [Cu₈As₃(AsSiMe₃)₂(dppb)₄]⁺[Cu{As₂(SiMe₃)₂}{As₄(SiMe₃)₄}]^‐ ( 1 ) and [Cu₈As₃(AsSiMe₃)₂(dppb)₄]⁺[Cu{As(SiMe₃)₂}₂]^‐ ( 2 ). The same reaction of CuCl, dppm (Bis(diphenylphosphino)methane) and LiSb(SiMe₃)₂ leads to the neutral cluster complex [Cu₁₀(Sb₃)₂(SbSiMe₃)₂(dppm)₆] ( 3 ). The structures of 1‐3 have been solved by X‐ray single crystal analyses.     

Facile CH Bond Formation by Reductive Elimination at a Dinuclear Metal Site

The electronically unsaturated dirhenium complex [Re₂(CO)₈(µ‐AuPPh₃)(µ‐Ph)] ( 1 ) was obtained from the reaction of [Re₂(CO)₈{µ‐η²‐C(H)?C(H)nBu}(µ‐H)] with [Au(PPh₃)Ph]. The bridging {AuPPh₃} group was replaced by a bridging hydrido ligand to yield the unsaturated dirhenium complex [Re₂(CO)₈(µ‐H)(µ‐Ph)] ( 2 ) by reaction of 1 with HSnPh₃. Compound 2 reductively eliminates benzene upon addition of NCMe at 25 °C. The electronic structure of 2 and the mechanism of the reductive elimination of the benzene molecule in its reaction with NCMe were investigated by DFT computational analyses.     

Reactivity of Yttrium Carboxylates Toward Alkylaluminum Hydrides

Yttrocene‐carboxylate complex [Cp*₂Y(OOCAr^Me)] (Cp*=C₅Me₅, Ar^Me=C₆H₂Me₃‐2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare‐earth‐metal carboxylates. Equimolar reactions with bis‐neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*₂Y(μ‐OOCAr^Me)(μ‐H)AlR₂] (R=CH₂SiMe₃, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium‐aluminum‐hydride complex [{Cp*₂Y(μ‐H)AlMe₂(μ‐H)AlMe₂(μ‐CH₃)}₂] could be isolated, which features a 12‐membered‐ring structure. The adduct complexes [Cp*₂Y(μ‐OOCAr^Me)(μ‐H)AlR₂] display identical ¹J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar ⁸⁹Y NMR shifts of δ=?88.1 ppm (R=CH₂SiMe₃) and δ=?86.3 ppm (R=Me) in the ⁸⁹Y DEPT45 NMR experiments.     

[(TeMe2)Mn(CO)4(μ5-Te)(μ4-Te)Mn4(CO)12]−: A Pentacoordinate Bridging Tellurido Ligand in a Square-Pyramidal Geometry

The first Te–Mn–CO clusters were obtained by the thermal reaction of K₂TeO₃ with [Mn₂(CO)₁₀] in MeOH. The basicity of the μ₄-Te ligand in the octahedral cluster anion [(μ₄-Te)₂Mn₄(CO)₁₂]²⁻ is demonstrated by its binding to the fragment [(TeMe₂)Mn(CO)₄]⁺ in an axial fashion to afford the novel cluster 1 .     

Pentanuclear Gold(I) Cluster with an Axially Chiral Biaryl Center: Synthesis and Chiral Transformation

We synthesized and structurally characterized a novel pentanuclear gold(I) cluster by a Ag(I)‐mediated organometallic transformation. The racemic mixture of this pentanuclear gold cluster has been successfully transformed into an enantio‐rich hexanuclear cluster compound by adding adscititious chiral species [Au₂(S‐BINAP)₂]²⁺ (S‐BINAP = (S)‐2,2’‐bis(diphenylphosphino)‐1,1’‐binaphthyl). In this process, a [AuPPh₃]⁺ species in the pentanuclear cluster is replaced by [Au₂(S‐BINAP)₂]²⁺. This strategy represents a new method for the designed construction of chiral metal clusters.     

Use of the Cationic Fragments [Ru(η5-C5H5) (MeCN)3]+ and [M(η6-C6H5R)(MeCN)3]+ (M=Os, Ru; R=H, Me) as Ionic Coupling Reagents in the Synthesis of the Clusters [Os4M2(CO)12(η6-C6H5R)], [Os4M(CO)12(η6-C6H6)(Au2dppm)] and [Os5Ru(CO)15(η5-C5H5)(AuPPh3)]*

The clusters [H₂Os₄M(CO)₁₂eta⁶-C₆H₆)] (M=Os, Ru) may be deprotonated to generate anions [Os₄M(CO)₁₂eta⁶-C₆H₆)]^2- which react with [M′eta⁶-C₆H₅R) (MeCN)₃]²⁺(M^′=Os, Ru; R=H, Me) to give the bicapped tetrahedral clusters [Os₄(CO)₁₂MM′eta⁶-C₆H₅R)₂]. Whereas [Os₄(CO)₁₂M₂eta⁶-C₆H₆)₂] (M=Os, Ru) have one Meta⁶-C₆H₆) unit in a site connected to three other metals, {3}, and one in a site connected to four other metals, {4}, [Os₄(CO)₁₂OsRueta⁶-C₆H₆)₂] has the Rueta⁶-C₆H₆) unit in the {3} site irrespective of whether the Os or Ru anion is capped. Coupling of these anions with Au₂dppm yields [Os₄M(CO)₁₂eta⁶-C₆H₆)(Au₂dppm)] (M=Os, Ru), which have the arene ligand in the axial site of a trigonal bipyramid and the digold unit capping two faces. Reduction of [H₂Os₅(CO)₁₅] with K/Ph₂CO and coupling with [Rueta⁵-C₅H₅)(MeCN)₃]²⁺yields the monoanion [Os₅(CO)₁₅Rueta⁵-C₅H₅)]^? which reacts with [AuPPh₃]⁺ generating [Os₅(CO)₁₅Rueta⁵-C₅H₅)(AuPPh₃)] with the “Ru(C₅H₅)” unit in the terminal {3} site.