Reactions of triosmium clusters Os3(CO)11(MeCN) and (μ-H)Os3(CO)10(μ-OH) withL-α-serine ethyl ester and ethanolamine

A series of novel chiral complexes with ,¹and ,² coordination of organic ligands were prepared by reactions of Os₃(CO)₁₁(MeCN) and (-H)Os₃(CO)₁₀(-OH) withL--serine ethyl ester and ethanolamine. The diastereomeric cluster complexes with serine ligands were separated by crystallization or chromatography. The structures of the compounds obtained were confirmed by¹H NMR and IR spectroscopy, mass-spectrometry, elemental analysis, and X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 525–530, March, 1994.     

Triosmium clusters with μ3-AsR group as a building block for hexaosmium-arsenic cluster synthesis. Synthesis and characterisation of [(CO)11Os3As(Os3(CO)9H3)] and [(CO)9H3Os3As(Os3(CO)9H3)]. Crystal structure of [(CO)11Os3As(Os3(CO)9H3)]

Reaction of the activated cluster [Os₃(CO)₁₁(CNMe)] with primary arsine AsH₃ forms the arsinidine compound [H₂Os₃(μ₃-AsH)(CO)₁₁] (1a, 1b), which on further reaction with [Os₃(CO)₁₁(NCMe)] yields [(CO)₁₁Os₃As(Os₃(CO)₉H₃)] (2) and with [H₂Os₃(CO)₁₀] yields [H₂Os₃(CO)₉As(Os₃(CO)₉H₂)] (3). Similarly [H₂Os₃(CO)₁₀] reacts with AsH₃ at room temperature to afford 3 in good yields. Thermal degradation and rearrangement of 2 gives the pentanuclear cluster [H₂Os₅(CO)₁₇AsH] (4).     

Reactions of Unsaturated Quinoline Triosmium Clusters [Os3(CO)9(μ3-η2-C9H5(4-R)N)(μ-H)] (R=Me or H) with Tetramethylthiourea: X-ray Structures of [Os3(CO)8(μ-η2-C9H5(4-Me)N)(η2-SC(NMe2NCH2Me)(μ-H)2] and [Os3(CO)9(μ-η2-C9H6N)(η1-SC(NMe2)2)(μ-H)]

Treatment of the electronically unsaturated 4-methylquinoline triosmium cluster $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_3\hbox{-}\upeta^{2}\hbox{-}\hbox{C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upmu\hbox{-H})]$ (1) with tetramethylthiourea in refluxing cyclohexane at 81°C gave $[\hbox{Os}_{3}\hbox{(CO)}_{8}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upeta^2\hbox{-SC}(\hbox{NMe}_2\hbox{NCH}_2\hbox{Me})(\upmu \hbox{-H})_2]$ (2) and $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N})(\upeta^1\hbox{-SC}(\hbox{NMe}_2)_2)(\upmu\hbox{-H})]$ (3). In contrast, a similar reaction of the corresponding quinoline compound $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_{3}\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upmu\hbox{-H})]$ (4) with tetramethylthiourea afforded $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upeta^{1}\hbox{-SC(NMe}_{2})_{2})(\upmu\hbox{-H)}]$ (5) as the only product. Compound 2 contains a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and a quinolyl ligand coordinated to the Os₃ triangle via the nitrogen lone pair and the C(8) atom of the carbocyclic ring. In 3 and 5, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom, which is also bound to the carbon atom of the quinolyl ligand. Compounds 3 and 5 react with PPh₃ at room temperature to give the previously reported phosphine substituted products $[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N)(PPh}_{3})(\upmu\hbox{-H)}]$ (6) and $[\hbox{Os}_{3}\hbox{(CO}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N)(PPh}_{3})(\upmu\hbox{-H)}]$ (7) by the displacement of the tetramethylthiourea ligand.     

New triosmium–iridium clusters: Synthesis and molecular structure of [Os3Ir2(Cp1)2(μ-OH)(μ-CO)2(CO)8Cl] (1), [Os3IrCp1(μ-OH)(CO)10Cl] (2), [Os3IrCp1(μ-H)(μ-Cl)(η3,μ3-C5H2N(NH2)Br)(CO)9] (3) and [Os3IrCp1(μ-Cl)2(η2,μ3-C5H3N(NH)Br)(CO)7] (4)

The trinuclear osmium carbonyl cluster, [Os₃(CO)₁₀(MeCN)₂], is allowed to react with 1 equiv. of [IrCp¹Cl₂]₂ (Cp¹ = pentamethylcyclopentadiene) in refluxing dichloromethane to give two new osmium–iridium mixed-metal clusters, [Os₃Ir₂(Cp¹)₂(μ-OH)(μ-CO)₂(CO)₈Cl] (1) and [Os₃IrCp¹(μ-OH)(CO)₁₀Cl] (2), in moderate yields. In the presence of a pyridyl ligand, [C₅H₃N(NH₂)Br], however, the products isolated are different. Two osmium–iridium clusters with different coordination modes of the pyridyl ligand are afforded, [Os₃IrCp¹(μ-H)(μ-Cl)(η³,μ₃-C₅H₂N(NH₂)Br)(CO)₉] (3) and [Os₃IrCp¹(μ-Cl)₂ (η²,μ₃-C₅H₃N(NH)Br)(CO)₇] (4). All of the new compounds are characterized by conventional spectroscopic methods, and their structures are determined by single-crystal X-ray diffraction analysis.     

Microwave Promoted Oxidative Addition Reactions of Os3(CO)12: Efficient Syntheses of Triosmium Clusters of the Type Os3(μ-X)2(CO)10 and Os3(μ-H)(μ-OR)(CO)10

Microwave heating allows for the high-yield, one-step synthesis of the known triosmium complexes Os₃(μ-Br)₂(CO)₁₀ (1), Os₃(μ-I)₂(CO)₁₀ (2), and Os₃(μ-H)(μ-OR)(CO)₁₀ with R = methyl (3), ethyl (4), isopropyl (5), n-butyl (6), and phenyl (7). In addition, the new clusters Os₃(μ-H)(μ-OR)(CO)₁₀ with R = n-propyl (8), sec-butyl (9), isobutyl (10), and tert-butyl (11) are synthesized in a microwave reactor. The preparation of these complexes is easily accomplished without the need to first prepare an activated derivative of Os₃(CO)₁₂, and without the need to exclude air from the reaction vessel. The syntheses of complexes 1 and 2 are carried out in less than 15 min by heating stoichiometric mixtures of Os₃(CO)₁₂ and the appropriate halogen in cyclohexane. Clusters 3–6 and 8–10 are prepared by the microwave irradiation of Os₃(CO)₁₂ in neat alcohols, while clusters 7 and 11 are prepared from mixtures of Os₃(CO)₁₂, alcohol and 1,2-dichlorobenzene. Structural characterization of clusters 2, 4, and 5 was carried out by X-ray crystallographic analysis. High resolution X-ray crystal structures of two other oxidative addition products, Os₃(CO)₁₂I₂ (12) and Os₃(μ-H)(μ-O₂CC₆H₅)(CO)₁₀ (13), are also presented.     

Synthesis and structure of Os3(μ-H)3(CO)9(μ3-Sn)Os3(μ-H)(CO)10(PEt2Ph): The first osmium cluster containing a face-capping tin atom

Pyrolysis a the cluster Os₃(µ-H h (CO)₁₀ (SnMe2 H) produced an as yet unidentified purple duster, which upon reaction with PEt₂Ph at room temperature, gave essentially a quantitative yield of the cluster Os₃(µ-H)₃(CO)₉(µ₃-Sn) Os₃(µ-H)(CO)₁₀(PEt₂Ph), 4. The X-ray structure of 4 (as the toluene solvate) shows that it consists Or two Os, triangles linked through a µ₄-Sn unit, such that one of the Os₃ triangle is µ₃-bonded to the Sn atom (Os-Sn range 2.689(2)–2.707(2) Å) and the other is bonded via a single covalent bond (Os-Sn = 2.643(2) Å). The phosphine ligand occupies the equatorial site on a second osmium atom a be latter Os₃ moiety that is syn to the Sn atom; the unique bridging hydride ligarid is believed to occupy a site that Acis to both the P and Sn atoms. Crystallographic data for compound4. 0.5C₇H₈: space group,P ; ca= 11862(4) Å,b = 12.940(4) Å,c = 16.513(5) Å, =68.96(3),=80.60(3)°,=62.49(2).R=0.029, 4118 observed reflections.     

Reactions of Triruthenium Clusters with Quinolines: X-Ray Structures of [Ru3(μ-CO)(CO)7{μ3-η2-P(C6H5)CH2P(C6H5)2)}{μ-η2-C9H5(CH3)N}] and [Ru3(CO)10(μ-H){μ-η2-C9H6N}]

The reactions of [Ru₃(CO)₁₀(μ-dppm)] 4 with quinolines afforded [Ru₃ (μ-CO)(CO)₇{μ₃-η²-P(C₆H₅)CH₂P(C₆H₅)₂)}{μ-η²-C₉H₅(R)N}] (8, R = 4-Me; 9, R = H) as the major products along with small amounts of known compound [Ru₃(CO)₉{μ₃-η³-P(C₆H₅)CH₂P(C₆H₅)(C₆H₄)}] 5. The molecular structure of 8 has been determined by single crystal X-ray studies. The reaction of 5 with 4-methylquinoline in refluxing cyclohexane afforded 8 and two known dinuclear compounds, [Ru₂(CO)₆{μ-CH₂P(C₆H₅)(C₆H₄)P(C₆H₅}] 10 and [Ru₂(CO)₆ {μ-(C₆H₄)P(C₆H₅)(CH₂)P(C₆H₅}] 11, in 40, 12, and 10% yields, respectively. The compounds 10 and 11 are also formed from the thermolysis of 4 in addition to the major compound 5. The solid state structure of the previously reported [Ru₃(CO)₁₀(η-H){μ-η²-C₉H₆N}] 2a is also reported for comparison.     

Probing the aromaticity of the [(H(t)Ac)3(μ2-H)6], [(H(t)Th)3(μ2-H)6],(+), and [(H(t)Pa)3(μ2-H)6] clusters

In this study we report about the aromaticity of the prototypical [(H(t)Ac)(3)(μ(2)-H)(6)], [(H(t)Th)(3)(μ(2)-H)(6)](+), and [(H(t)Pa)(3)(μ(2)-H)(6)] clusters via two magnetic criteria: nucleus-independent chemical shifts (NICS) and the magnetically induced current density. All-electron density functional theory calculations were carried out using the two-component zeroth-order regular approach and the four-component Dirac-Coulomb Hamiltonian, including scalar and spin-orbit relativistic effects. Four-component current density maps and the integration of induced ring-current susceptibilities clearly show that the clusters [(H(t)Ac)(3)(μ(2)-H)(6)] and [(H(t)Th)(3)(μ(2)-H)(6)](+) are non-aromatic whereas [(H(t)Pa)(3)(μ(2)-H)(6)] is anti-aromatic. However, for the thorium cluster we find a discrepancy between the current density plots and the classification through the NICS index. Our results also demonstrate the increasing influence of f orbitals, on bonding and magnetic properties, with increasing atomic number in these clusters. We think that the enhanced electron mobility in [(H(t)Pa)(3)(μ(2)-H)(6)] is due the significant 5f character of its valence shell. Also the participation of f orbitals in bonding is the reason why the protactinium cluster has the shortest bond lengths of the three clusters. This study provides another example showing that the magnetically induced current density approach can give more reliable results than the NICS index.     

Reactivity of triosmium clusters with 3,4-dimethyl-1-phenylphosphole and cyanoethyldi-tert-butylphosphine ligands: X-ray crystal structures of [Os3(CO)9(μ-OH)(μ-H)(η1-PhPC4H2Me2)] and [Os3(CO)11(η1- t Bu2PC2H4CN)]

Reaction of [Os₃(μ-H)₂(CO)₁₀] with 3,4-dimethyl-1-phenylphosphole in refluxing cyclohexane affords two substituted triosmium clusters: [Os₃(CO)₉(μ-H)(μ³:η¹:η¹:η²-PhPC₄H₃Me₂)] (1) and [Os₃(CO)₉(H)(μ²-η¹:η²-PhPC₄H₄Me₂)] (2), of which cluster 2 exhibits two chromatographically non-separable isomeric forms attributed to terminal and bridging coordination of the hydride ligand, respectively. When this reaction is performed in refluxing THF, the only product is the cluster [Os₃(CO)₉(μ-OH)(μ-H)(η¹-PhPC₄H₂Me₂)] (3). Crystallographic information obtained for cluster 3 shows the phosphole ligand occupying an equatorial position, as expected, while the OH group is asymmetrically bridging unlike previously reported similar compounds. Additionally, interaction of the labile cluster [Os₃(CO)₁₁(CH₃CN)] with cyanoethyldi-tert-butylphosphine in dichloromethane at room temperature was found to give [Os₃(CO)₁₁(η¹- ^t Bu₂PC₂H₄CN)] (4) as the only product; its crystallographic characterization shows that the phosphine ligand coordinates by means of the phosphorus atom in an equatorial fashion, analogous to compound 3.     

Synthesis and X-ray crystal structure of the electron-deficient metal carbonyl cluster [Os3(CO)5(μ3-H)(μ-H)(μ-PtBu2)2(μ-Ph2PCH2PPh2)]

The reaction of [Os₃(CO)₁₀(μ-dppm)] (1) with ^tBu₂PH in refluxing diglyme results in the electron-deficient metal cluster complex [Os₃(CO)₅(μ₃-H)(μ-P^tBu₂)₂(μ-dppm)] (2) (dppm = Ph₂PCH₂PPh₂) in good yields. The molecular structure of 2 has been established by a single crystal X-ray structure analysis. In contrast to the known homologue [Ru₃(μ-CO)(CO)₄(μ₃-H)(μ-H)(μ-P^tBu₂)₂(μ-dppm)] (3), no bridging carbonyl ligand was found in 2. The electronically unsaturated cluster 2 does not react with carbon monoxide under elevated pressure, therefore 2 seems to be coordinatively saturated by reason of the high steric demands of the phosphido ligands.     

Reactivity of the Unsaturated Triosmium Cluster [Os3(CO)8{Ph2PCH2P(Ph)C6H4}(μ-H)] with Thiols

The reaction of the unsaturated cluster [(-H)Os₃(CO)₈{Ph₂PCH₂P(Ph)C₆H₄}] 2 with C₂H₅SH, CH₃CH(CH₃)SH and C₆H₅SH are reported. The reaction of 2 with C₂H₅SH yields the new complexes [Os₃(CO)₈(-SC₂H₅)(¹-SC₂H₅){Ph₂PCH₂P(Ph)C₆H₄}(-H)] 9 and [Os₃(CO)₈)(SC₂H₅)(Ph₂PCH₂P)(Ph)C₆H₄}] 8 in 24 and 57% yields respectively and the known compound [(Os₃(CO)₈)(-SC₂H₅)(-dppm)(-H)] 7 in 5% yield. Compound 9, which exists as two isomers in solution, converts into 8 almost quantitatively in solution at 25°C and more rapidly in refluxing hexane. Compound8 reacts with H₂ at 110°C to give 7 in high yield (86%). Treatment of 2 with propane-2-thiol yields [Os₃(CO)₈{-SCH(CH₃)CH₃}{Ph₂PCH₂P(Ph)C₆H₄}] 10 and [(Os₃(CO)₈{-SCH(CH₃)CH₃}{¹-SCH(CH₃)CH₃}{Ph₂PCH₂P(Ph)C₆H₄}(-H)] 11 in 75 and 3% yields respectively while with C₆H₅SH, [(Os₃(CO)₈(-SC₆H₅)(-dppm)(-H)] 6 is obtained as the only product in 75% yield. In both 8 and 10, the thiolato ligand bridges the Os–Os edge which is also bridged by the metallated phenyl group. The new compounds have been characterized by elemental analyses and spectroscopic methods (IR, ¹H and ³¹P NMR). The molecular structures of 7, 8, 9 and 10 are reported as determined by X-ray diffraction studies.     

Study of allylic rearrangement in (μ-H)Os3(μ-O=CNRCH2CH=CH2)(CO)10 (R=H or CH3) clusters

The migration of the double bond in the allylcarboxamide ligands of (μ-H)Os₃(μ-O=CN RCH₂CH=CH₂) (CO)₁₀ (R=H (1) or CH₃ (2)), (μ-D)Os₃(μ-O=CNDCH₂CH=CH₂) (CO)₁₀, and (μ-H)Os₃(μ-O=CNHCD₂CH=CH₂)(CO)₁₀ clusters was studied by¹H,²H, and¹³C NMR spectroscopy. Neither μ-D nor ND groups in the deuterated complexes are directly involved in prototropic processes of allylic rearrangement. Initially, the deuterium atom of the CD₂ group migrates to the ψ-carbon atom of the allyl fragment to form the −CD=CH-CH₂D propenyl moiety, in which the deuterium and hydrogen atoms are gradually redistributed between the ψ-and β-carbon atoms. The triosmium cluster complexes containing the bridging carboxamide ligands O=CNRR' catalyze the allylic rearrangement ofN-allylacetamide. Based on the data obtained, the probable scheme of the allylic rearrangements in clusters1 and2 was proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2182–2186, November, 1999.     

Synthesis and structures of complexes Os3(μ-H)2(CO)7(μ-RC5H3N){μ3-Ph2PCH2P(C6H4)Ph} (R = H, Me) with ortho-metalated pyridine ligands. The revised structure of the triosmium cluster ”Os3(μ-H)2(CO)7(μ-C6H4){μ3-Ph2PCH2P(C6H4)Ph}”

The structure of the previously synthesized triosmium cluster was revised. The structure Os₃(μ-H)₂(CO)₇(μ-C₆H₄){μ₃-Ph₂PCH₂P(C₆H₄)Ph} suggested earlier was not confirmed. The cluster has the composition Os₃(μ-H)₂(CO)₇(μ-C₅H₄N){μ₃-Ph₂PCH₂P(C₆H₄)Ph} and contains the ortho-metalated pyridine ligand. The X-ray diffraction study of the complex Os₃(μ-H)₂(CO)₇(μ-MeC₅H₃N){μ₃-Ph₂PCH₂P(C₆H₄)Ph} containing the ortho-metalated 4-methylpyridine ligand made it possible to distinguish between the C and N atoms of the pyridine ligands in the resulting triosmium clusters.     

Protonation and acylation of the heterometallic complexes (μ-H)Os3(μ-O2CC5H4FeCp)(CO)10 and Fe{(μ-O2CC5H4)(μ-H)Os3(CO)10}2

The reactions of the heterometallic complexes (-H)Os₃(-O₂CC₅H₄FeCp)(CO)₁₀ (1) and Fe{(-O₂CC₅H₄)(-H)Os₃(CO)₁₀}₂ (2) with CF₃COOH, CF₃SO₃H, and AcCl were studied. The reaction of 1 with CF₃COOH involves interaction with the Cp ligands, protonation of the O atom of the bridging carboxylate group, and oxidative degradation of the complex. At low concentrations, CF₃SO₃H protonates the O atom of the bridging carboxylate group, while at high concentrations, degradation of the complex takes place. The reaction of complex 2with either CF₃COOH or low concentrations of CF₃SO₃H results in successive elimination of two [(-H)Os₃(CO)₁₀] cluster fragments due to protonation of the O atoms of the carboxylate groups. In the case of high CF₃SO₃H concentrations, the Os—Os bonds of both cluster fragments of 2 are also protonated to give the [Fe{(-O₂CC₅H₄)(-H)₂Os₃(CO)₁₀}₂]²⁺ dication. The Friedel—Crafts acylation of 1 takes place only when a large excess of AcCl and AlCl₃ is used to give two new complexes, (-H)Os₃(-O₂CC₅H₄FeC₅H₄C(O)CH₃)(CO)₁₀ and (-H)Os₃(-O₂CC₅H₃C(O)CH₃FeCp)(CO)₁₀ in a 2 : 1 ratio.     

Synthesis and structure of three isomeric cluster complexes (μ-H)Os3μ-O2CC5H4Mn(CO)3(PPh3)2(CO)8

The reaction of (μ-H)Os₃μ-O₂CC₅H₄Mn(CO)₃(CO)₁₀ with PPh₃ in the presence of Me₃NO gave mono- and disubstituted heterometallic complexes (μ-H)Os₃μ-O₂CC₅H₄Mn(CO)₃(PPh₃)(CO)₉ and (μ-H)Os₃μ-O₂CC₅H₄Mn(CO)₃ (PPh₃)₂(CO)₈. Crystal structure determination was performed for three isomeric cluster complexes (μ-H)Os₃μ-O₂CC₅H₄Mn(CO)₃(PPh₃)₂(CO)₈, which are both geometrical and conformational isomers differing in color. The geometrical isomerism is due to the attachment of the PPh₃ group at different vertices of the Os₃ triangle relative to the O₂CC₅H₄Mn(CO)₃ bridging ligand. The conform ational isomerism implies that the molecules have the same arrangement of ligands and differ only in the values of bond angles between the planar fragments of the clusters.     

Clusters containing ynamine ligands. 4. The synthesis and characterizations of ReMn(CO)8 [μ-MeC2NMe2] and ReMn(CO)7 [μ-MeCC(NMe2)C(NMe2)CMe] and the development of a bonding model for the coordination of ynamines to M2(CO)8 clusters

The compound ReMn(CO)₈ (-MeC₂NMe₂),2 was obtained in 11% yield by the decarbonylation of ReMn(CO)₁₀ with Me₃NO followed by reaction MeC₂NMe₂. Compound2 will add one equivalent of MeC₂NMe₂ at 25°C to yield the mixed metal complex ReMn(CO)₇ [-C(Me) C(NMe₂) C(NMe₂) C(Me)],3 in 7% yield. Compounds2 and3 were characterized by IR,¹H NMR, and single crystal x-ray diffraction analyses. Compound2 exists as two isomers. Each isomer contains an asymmetric bridging ynamine ligand. The principal isomer has the amine-substituted carbon atom coordinated to the manganese atom. The minor isomer has the amine-substituted carbon atom coordinated to the rhenium atom. In compound3 the two ynamines have been coupled in a head-to-head fashion to produce a ferrole-like structure in which the coupled ligands are -bonded to the manganese atom. Extended Hückel molecular orbital calculations were performed on the parent complex Re₂(CO)₈ (-MeC₂NMe₂),1 to try to understand the reasons for the preferred asymmetric coordination of the ynamine ligand in1 and2. It was found that the asymmetric coordination permits a strong stabilizing interaction between the one of the * orbitals of the ligand and the metallic orbital that is principally responsible for the formation of the metal-metal bond. Crystal Data: for2: space group=P2₁/c,a=9.740(1)Å,b=11.293(2)Å,c=15.483(3)Å, =97.46(1)°,Z=4, 1876 reflections,R=0.026; for3: space group=Pca2₁,a=17.541(2)Å,b=8.441(1)Å,c=14.033(3)Å,Z=4, 1335 reflections,R=0.022.     

Synthesis,chemical, and electrochemical characterization of the [Ag13{μ3-Fe(CO)4}] n− (n = 3, 4, 5) cluster anions: X-Ray structural determination of [N(PPh3)2]3 [Ag12(μ12-Ag){μ3Fe(CO)4}8]1

The oxidation of the [Fe(CO)₄]^2– dianion with Ag⁺ salts occurs through a particularinner-sphere mechanism, which involves an intermediate cascade of silver clusters stabilized by Fe(CO)₄ ligands. The last detectable Ag-Fe cluster of the sequence is the [Ag₁₃{-Fe(CO)₄}₈]^3– trianion, which has been selectively obtained by using ca. 1.7 equivalents of Ag⁺ per mole of [Fe(CO)₄]^2–. The [Ag₁₃{-Fe(CO)₄}₈]^3–- trianion has been isolated in a crystalline state with several quaternary cations, and has been characterized by X-ray diffraction studies of its bis(triphenylphosphine)iminium salt. [N(PPh₃)₂]₃ [Ag₁₃{ ₃-Fe(CO)₄}₈]·2(CH₃)₂CO, monoclinic, space group P2₁ (No.4),a = 16.284(2) Å,b =18.767(5) Å,c = 25.905(4) Å, = 90.46(1)°,V = 7916(3) ų,Z = 2,R = 0.0324. The molecular structure of the anion consists of a centered cuboctahedron of silver atoms with the triangular faces capped by Fe(CO)₄ units. Chemical reduction of ( Ag₁₃{ ₃-Fe(CO)₄}₈]^3– affords the corresponding [Ag₁₃{ ₃-Fe(CO)₄)₈]^4–, which in turn gives [Ag₁₃{ ₃-Fe(CO)₄)₈]^5– and [Ag₆{ ₃-Fe(CO)₄}₄]^– upon further reduction. Electrochemical investigations confirm the reversibility of the [Ag₁₃{ ₃-Fe(CO)₄}₈]^3–/4– redox change. Furthermore, in spite of some electrode poisoning effects, evidence of the existence of the [Ag₁₃{ ₃-Fe(CO)₄}₈]^5– pentaanion was obtained. The yet structurally uncharacterized [Ag₆{ ₃-Fe(CO)₄)₄]^2– dianion is quantitatively obtained by reaction of [Fe(CO)₄]^2– with ca. 1.5 equivalents of Ag⁺ or by addition of one equivalent of Ag⁺ to solutions of the [Ag₅{Fe(CO)₄}₄]^3– trianion. All attempts to isolate its quaternary salts as crystalline materials failed owing to formation of amorphous insoluble precipitates. The above series of ₃-Fe(CO)₄ octa-capped cuboctahedral Ag₁₃ clusters can be envisioned as the Ag⁺ . Ag and Ag^– cryptates of the [Ag₁₂{}₃-Fe(CO)₄}₈]^4– cryptand. respectively.Dedicated to Prof L. F. Dahl on his 65th birthday.