Cyanide bridged hexanuclear iron complexes

The hexanuclear complexes [Fe₂(NO₃)₂(μ-OR)₂] [NC-Fe(dppe)Cp]₄(PF₆)₂ with OR=OMe or OEt were obtained from Fe(Py)₃(NO₃)₃ and Cp(dppe)Fe-CN in methanol or ethanol. They were identified by a structure determination and by their electrochemical data. Their ν(CN) band positions indicate that the central Fe₂(μ-OR)₂ cores are very strong electron acceptors, which is underlined by strong intervalence transfer bands in the NIR.     

Syntheses and structural characterization of mononuclear Rh-Cp* and Ir-Cp* complexes with η-phenanthrene, η-pyrene and η-triphenylene

Four novel mononuclear Rh-Cp* and Ir-Cp* complexes with polycyclic aromatic hydrocarbons (PAHs), [M(Cp*)(η⁶-PAHs)](BF₄)₂ (M = Rh and Ir; Cp* = η⁵-C₅Me₅; PAHs = phenanthrene (phn), pyrene (pyr) and triphenylene (triph)), were prepared by the reactions of the intermediate [M(Cp*)(Me₂CO)₃]²⁺ with appreciable PAHs. Their structures were characterized by a single crystal X-ray analysis, ¹H, ¹³C {¹H} NMR and 2D NMR techniques. The X-ray crystallographic studies showed that the [M(Cp*)]²⁺ fragment is η⁶-coordinated to one terminal benzene ring in each PAH. In particular, it is interesting to note that the partial π/π/π/π interaction was formed in the Ir-pyr complex [Ir(Cp*)(η⁶-pyr)](BF₄)₂. The 1D and 2D NMR studies described that the Rh-Cp* and Ir-Cp* complexes with PAHs gave unique ¹H and ¹³C {¹H} NMR spectra with positive coordination shifts (Δδ(¹H, ¹³C)) in (CD₃)₂CO at 23 °C, which are likely induced by the local effect and the non-local effect on the coordination of the [M(Cp*)]²⁺ fragment to PAHs. The decreasing of the coupling constants (³J_H-H) in the η⁶-coordinated benzene ring is also induced, with no changes in the uncoordinated benzene rings. The time-course of ¹H NMR spectra showed that Rh-Cp* and Ir-Cp* complexes with PAHs are partially dissociated to [M(Cp*)(Me₂CO)₃]²⁺ and metal-free PAHs in (CD₃)₂CO at 23 °C. It was demonstrated that their stabilities are in the order of Ir-triph, Ir-phn, Ir-pyr and Rh-triph complexes in (CD₃)₂CO.     

(C5Me5)2NbBH4, a new reagent for the synthesis of Ru and Co carbonyl clusters with interstitial boron or carbon

The reaction of Cp*₂NbBH₄ (Cp* = η⁵-C₅Me₅) with Ru₃(CO)₁₂ gave a mixture of compounds, from which only [Cp*₂Nb(CO)₂]₂[Ru₆(CO)₁₆C] (1) could be characterized by spectroscopic and crystallographic methods. ¹¹B NMR spectroscopy proved that interstitial boron may be present in other Ru₆ clusters, but these compounds did not crystallize. The reaction of Cp*₂NbBH₄ with Co₂(CO)₈ gave among others the salts [Cp*₂Nb(CO)₂]₂[Co₆(CO)₁₅C] (4) and [Cp*₂Nb(CO)₂]₃[Co₁₃(CO)₂₄C₂] (5), which were examined by X-ray diffraction studies. The true nature of the interstitial atoms in 5 was deduced from electrochemical investigations, which reveal similar redox properties as for the already known [Co₁₃(CO)₂₄C₂]³⁻ anion.     

First crystallographic determination of dichloro-bridged dinuclear rhodium Cp* complex with neutral Me2CO molecules. [Rh2(Cp*)2(μ-Cl)2(Me2CO)2](BF4)2 (Cp* = η-C5Me5)

The single crystals of dichloro-bridged dinuclear Rh-Cp* complex with neutral Me₂CO molecules, [Rh₂(Cp*)₂(μ-Cl)₂(Me₂CO)₂](BF₄)₂ (Cp* = η⁵-C₅Me₅), was isolated and the structure was in first determined crystallographically.     

Dinuclear ruthenium(II) catecholato and 2,3-naphthalenediolato complexes featuring κ-diaryloxo/η-arene coordination mode

A new dinuclear ruthenium(II) catecholato complex [Cp*Ru(κ²:η⁶-μ₂-1,2-O₂C₆H₄)RuCp*] (3; Cp* = η⁵-C₅Me₅) has been prepared by the reaction of [Cp*RuCl]₄ with 2 equiv. of disodium catecholate in THF. Complex 3 has a dinuclear structure, in which one of the Cp*Ru fragments is κ²-bonded to the two oxygen atoms and the other is η⁶-bonded to the aromatic ring. Similar treatment of [Cp*RuCl]₄ with disodium 2,3-naphthalenediolate affords an analogous κ²:η⁶-bonded dinuclear complex [Cp*Ru(κ²:η⁶-μ₂-2,3-O₂C₁₀H₆)RuCp*] (4) with selective π-complexation at the oxygen-substituted naphthalene ring. The molecular structure of 4 has been determined by X-ray crystallography. The oxygen-bound ruthenium atoms in complexes 3 and 4 are coordinatively unsaturated and readily uptake 1 equiv. of carbon monoxide to give the corresponding carbonyl adducts [Cp*Ru(CO)(κ²:η⁶-μ₂-1,2-O₂C₆H₄)RuCp*] (5) and [Cp*Ru(CO)(κ²:η⁶-μ₂-2,3-O₂C₁₀H₆)RuCp*] (6), respectively.     

A structural investigation of the heterobimetallic carbocation complex [Cp(CO)2Fe{μ-CH2CH(CH2)3}W(CO)3Cp]BPh4

The reaction of [Cp^∗(CO)₂Fe{μ-CH₂CH(CH₂)₃}W(CO)₃Cp]PF₆ with NaBPh₄ in dry acetone gave [Cp^∗(CO)₂Fe{μ-CH₂CH(CH₂)₃}W(CO)₃Cp]BPh₄. The bond Fe-C_β is shorter than that reported for the shorter chain carbocationic complexes. The data suggest that metallacyclopropane character is on the iron side of the molecule both in the solid state and in solution.     

Synthesis and characterization of transition metal complexes bearing tetrafluoro-4-pyridyl substituent on the cyclopentadienyl ring

The reaction of sodium cyclopentadienide (NaCp) with pentafluoropyridine gives Na[4-(C₅F₄N)C₅H₄] (^PyFCpNa, 1) contaminated with starting NaCp from which pure 1 could be extracted with Et₂O. Hydrolysis of 1 and subsequent crystallization gives pure Diels-Alder dimer 1,4-bis(tetrafluoro-4-pyridyl)tricyclo[5.2.1.0^2,6]deca-3,8-diene (2). The reactions of 1 with FeCl₂, [MnBr(CO)₅], CoBr₂, [Ni(NH₃)₆]Cl₂, [TiCl₄(THF)₂] and [CpTiCl₃] cleanly affords the corresponding metallocenes [Fe(^PyFCp)₂] (3), [(^PyFCp)Mn(CO)₃] (5), [Co(^PyFCp)₂] (6), [Ni(^PyFCp)₂] (8), [(^PyFCp)₂TiCl₂] (9) and [(^PyFCp)(Cp)TiCl₂] (10), respectively. Tetrafluoro-4-pyridyl-substituted ferrocene 3 and [Fe(^PyFCp)(Cp)] (4) can be alternatively prepared by the reaction of the respective lithioferrocenes with C₅F₅N in THF. Air-oxidation of complex 6 affords the corresponding cobaltocenium salt [Co(^PyFCp)₂]PF₆ (7). All prepared compounds were characterized spectroscopically and by elemental analysis. The crystal structures of 3-7 were determined, revealing extensive arene π?π stacking and C-H?F-C contacts. Electrochemical studies supported with the spectroscopic data of the prepared metallocene complexes evidenced strong electron-withdrawing nature of the tetrafluoro-4-pyridyl substituent.     

Syntheses and crystal structures of mononuclear and dinuclear (pentamethylcyclopentadienyl)iridium(III) complexes containing 2-mercaptobenzimidazole

A reaction of [Cp*IrCl₂]₂ {Cp* = η⁵-C₅(CH₃)₅} and 2-mercaptobenzimidazole (H₂bimt) in methanol in a 1:2 molar ratio gave a yellow complex of [Cp*IrCl₂(H₂bimt)]·CH₃OH (1). In compound 1 the H₂bimt acts as a monodentately S-donating (κS) ligand. A similar reaction of [Cp*IrCl₂]₂ and H₂bimt in the presence of NaOCH₃ (molar ratio of 1:2:2) gave an orange product (2) on addition of excess amount of NH₄PF₆. Compound 2 was composed of an unsymmetrical dinuclear complex cation, [(Cp*IrCl)₂(μ-Hbimt)(μ-H₂bimt)]⁺, a PF₆⁻ anion, and water molecules of crystallization. In the complex cation, H₂bimt bridges two Ir^III centers by S atom in the μ-κS:κS mode, while the monodeprotonated Hbimt⁻ ligand bridges via S and N atoms in the μ-κS:κN¹ mode.     

The role of cyclopentadienyl versus indenyl in Mo(II) spirodiene complexes reactivity: A DFT mechanistic study

Spiro[2,4]hepta-4,6-diene and spiro[4,4]nona-1,3-diene react with [Mo(CO)₂Cp’(NCCH₃)₂][BF₄] (Cp’ = Cp, Ind; Ind = η⁵-C₉H₇) to afford the corresponding diene complex [Mo(diene)(CO)₂Cp′]⁺. When Cp’ = Ind, the reaction proceeded forward leading to ring opening in the case of the small spiro ring. Although this and another product resulting from migration of the side arm to the carbonyl were detected when Cp’ = Cp, they did not form from the diene complex. A DFT/PBE1PBE study was carried out and showed a kinetically controlled reaction pathway leading from the [Mo(diene)(CO)₂Ind]⁺ to the reaction product, with an activation barrier of 21.3 kcal mol⁻¹. The thermodynamic preferred species was the non-observed complex (insertion), and its formation required higher barriers. In the presence of Cp, all the barriers increased significantly, explaining the inertness of the initial diene complex. The interpretation of this behaviour is associated with the ease of the η⁵ → η³ haptotropic rearrangement of the indenyl, which helps to lower some relevant barriers. This route is not available for the Cp analogue.     

On the nature of mutual inactivation between [Cp*Rh(bpy)(H2O)]2+ and enzymes – analysis and potential remedies

Pentamethylcyclopentadienyl rhodium bipyridine ([Cp*Rh(bpy)(H₂O)]²⁺) is a versatile catalyst to promote biocatalytic redox reactions. However, its major drawback lies in the mutual inactivation of [Cp*Rh(bpy)(H₂O)]²⁺ and the biocatalyst. This interaction was investigated using the alcohol dehydrogenase from Thermus sp. ATN1 (TADH) as model enzyme. TADH binds 4 equiv. of [Cp*Rh(bpy)(H₂O)]²⁺ without detectable decrease in catalytic activity and stability. Higher molar ratios lead to time-, temperature-, and concentration-dependent inactivation of the enzyme suggesting [Cp*Rh(bpy)(H₂O)]²⁺ to function as an ‘unfolding catalyst’. This detrimental activity can be circumvented using strongly coordinating buffers (e.g. (NH₄)₂SO₄) while preserving its activity as NAD(P)H regeneration catalyst under electrochemical reaction conditions.     

Reactions of ‘GaI’ with organometallic transition metal halides

Two approaches towards the synthesis of phosphine ligated half-sandwich complexes [(η^x-C_xH_x)M(PR₃)₂GaI₂]_n containing diiodogallyl ligands have been investigated. Insertion of ‘GaI’ into the Mo-I bond of (η⁷-C₇H₇)Mo(CO)₂I has been shown to yield the crystallographically characterized dimeric complex [(η⁷-C₇H₇)Mo(CO)₂GaI₂]₂ (2). Attempts to substitute the carbonyl ligands by the phosphine ligand dppe [dppe = bis(diphenylphosphino)ethane] have been shown instead to yield the sparingly soluble complex [(η⁷-C₇H₇)Mo(CO)₂GaI₂]₂(μ-dppe) (3) in which the phosphine bridges two [(η⁷-C₇H₇)Mo(CO)₂GaI₂] units via a pair of P → Ga donor/acceptor bonds. By contrast, attempts to insert ‘GaI’ directly into the metal-halogen bond of phosphine ligated complexes such as (η⁵-C₅H₅)Ru(PPh₃)₂Cl or (η⁵-C₅H₅)Ru(dppe)Cl have been shown to result in the formation of the tetraiodogallate species(η⁵-C₅H₅)Ru(PPh₃)₂(μ-I)GaI₃ (5) and [(η⁵-C₅H₅)Ru(dppe)]⁺[GaI₄]⁻ (7).     

Crystallographic and theoretical studies of (η-C5Me5)Ru(2,4-dimethyl-η-pentadienyl) and [(η-C5Me5)Rh(2,4-dimethyl-η-pentadienyl)][BF4]

The determination of the solid state structure of Cp*Ru(2,4-dimethyl-η⁵-pentadienyl) (1), where Cp* = pentamethylcyclopentadienyl, fills the gap in the series of previously established structures of closely related compounds. Compound 1 does not exhibit the ideal C_S symmetry and its conformation is intermediate between the C_S-synperiplanar eclipsed and C_S-antiperiplanar arrangements of the ligands. Density functional theory studies indicate that the C_S-synperiplanar eclipsed, C_S-antiperiplanar, and intermediate conformations of 1 and Cp*Rh(2,4-dimethyl-η⁵-pentadienyl)⁺ (2) do not differ by more than a few tenths of 1 kcal/mol. The geometrical features of cation 2 are similar to those of 1, and in both complexes the pentadienyl ligands are not planar. The metal-carbon distances to the Cp* ligands in 1 and 2 are comparable, while the metal-carbon distances to the pentadienyl moiety are somewhat shorter in the Ru complex. A study of the conformational flexibility of the Cp* ligand in 5610 organometallic complexes showed that it usually shields the central metal by 36.2(10)%, provided the metal-centroid(Cp*) distances are normalized to 2.28 Å. The corresponding values in 1 and 2 are 37.2% and 37.4%, respectively.     

Metal-assisted preparation of the alkenyl ketone and carbonyl complexes from 1-alkyne and H2O: C–C triple bond cleavage of terminal alkyne

Reactions of Cp*RhCl₂(PPh₃) (1) with 1-alkyne and H₂O in the presence of KPF₆ generated alkenyl ketone complexes [Cp*Rh(CRCHCOCH₂R)(PPh₃)](PF₆) (2) (R = Ph (a), C₆H₄−p-Me (b), C₆H₄-p-COOMe (c), C₆H₄-p-NO₂ (d)). A similar complex [Cp*Rh(CPhCHCOCH₂Ph)(PMePh₂)](PF₆) (2e) was obtained by use of Cp*RhCl₂(PMePh₂). It was revealed by X-ray analyses of 2b, 2c and 2e that the complexes 2 consist of the five-membered ring structures bound by the carbon and oxygen atoms of the alkenyl ketone group. Similar reactions of Cp*IrCl₂(PPh₃) (6) or (C₆Me₆)RuCl₂(PPh₃) (7) proceeded with a cleavage of C–C triple bond of 1-alkyne without formation of an alkenyl ketone complex, affording the corresponding carbonyl complexes, [Cp*IrCl(PPh₃)(CO)](PF₆) (8) or [(C₆Me₆)RuCl(PPh₃)(CO)](PF₆) (9). The diphosphine complexes [(Cp*MCl₂)₂{μ-diphos}] (4: M = Rh, diphos = dppm,; 12a: M = Ir, diphos = dppm; 12b: M = Ir, diphos = dppb) gave a Cl-bridged rhodium complex [{Cp*Rh(μ-Cl)}₂{μ-dppm}](PF₆)₂ (5), mono-carbonyl or dicarbonyl iridium complexes,[(Cp*IrCl₂){μ-dppm}{Cp*IrCl(CO)}](PF₆)(13a) or [{Cp*IrCl(CO)}₂{μ-dppb}](PF₆)₂ (14b), respectively.     

The synthesis, structure, reactivity and electrochemical properties of ruthenium complexes featuring cyanoacetylide ligands

The complex [Ru(CCCN)(dppe)Cp*] (1) is readily obtained (ca. 70%) from the sequential reaction of [Ru(CCH₂)(dppe)Cp*]PF₆ with ⁿBuLi and phenyl cyanate. The complex behaves as a typical transition metal acetylide upon reaction with tetracyanoethene, affording a metallated pentacyanobutadiene. Complex 1 is a useful metalloligand, and its reactions with [W(thf)(CO)₅], [RuCl(PPh₃)₂Cp], [RuCl(dppe)Cp*] or cis-[RuCl₂(dppe)₂] all afforded products featuring the M-CCCN-M′ motif, for which ground state structures indicate a degree of polarisation. Electrochemical and spectroelectrochemical studies reveal moderate interactions between the metal centres in the 35-electron dications [{Cp*(dppe)Ru}(μ-CCCN){RuL₂Cp′}]²⁺ (RuL₂Cp′ = Ru(PPh₃)₂Cp, Ru(dppe)Cp*).     

Chemical and structural aspects of cyclopentadienyl uranium(IV) tetrahydroborato complexes

Several new or partially described complexes of uranium(IV) of the series Cp _4−n U(BH ₄) _n [Cp=η ⁵- C ₅H ₅, η ⁵-C ₅H ₄CH ₃ or η ⁵-C ₅H ₄Si(CH ₃) ₃] are reported, mainly in order to systematically compare their physical, chemical and spectroscopic properties. X-ray data of the crystal structure of Cp ₃UBH ₄ are also reported.     

3,5-Bis(diphenylphosphinoethyl)pyrazolate ligand (PNNP) and its dirhodium complexes: Comparison with related quadridentate dinucleating diphenylphosphinomethyl (PNNP) and phthalazine derivatives (PNNP)

Dirhodium carbonyl complex with the 3,5-bis(diphenylphosphinoethyl)pyrazolato ligand (PNNP^C2), [(μ-κ²:κ²-PNNP^C2)Rh₂(CO)₃]BF₄, is prepared and its reactivity is studied as compared with the previously reported 3,5-bis(diphenylphosphinomethyl)pyrazolate (PNNP), [(μ-κ²:κ²-PNNP){Rh(CO)₂}₂]BF₄, and 1,4-bis(diphenylphosphinomethyl)phthalazine (PNNP^Ph) derivatives, [(μ-κ²:κ²-PNNP^Ph){Rh(CO)₂}₂](BF₄)₂. The three quadridentate ligands are different in the size of the central ring and the charge; six-membered ring/neutral (PNNP^C2) vs. five-membered ring/mono-negative (PNNP) vs. six-membered ring/neutral (PNNP^Ph). The number of the carbonyl ligands (n) in the dirhodium carbonyl complexes, [(μ-PNNP)Rh₂(CO)_n](BF₄)_x, is dependent on the dinucleating ligand: n = 2 (PNNP^Ph), 3 (PNNP^C2) and 4 (PNNP^Py). The three dirhodium carbonyl complexes serve as 4e-acceptors, and their reactivities turn out to be very similar as can be seen from formation of the analogous, unique tetranuclear μ₄-acetylide ([(μ-PNNP)₂{Rh(CO)}₄(μ₄-CC-R)](BF₄)_x) and μ₄-dicarbide complexes ([(μ-PNNP)₂{Rh(CO)}₄(μ₄-C₂)](BF₄)_x).     

Electrochemical oxidation of ethanol using Nafion electrodes modified with heterobimetallic catalysts

Chemically modified electrodes were prepared by adsorption of Nafion/catalyst films of the type Nafion/Cp(PPh₃)Ru(μ-I)(μ-dppm)PdCl₂ (N1), Nafion/[η⁵-C₅H₄CH₂CH₂(NHMe₂)⁺]Ru(PPh₃)(μ-I)(μ-dppm)PtCl₂ (N2), Nafion/[η⁵-C₅H₄CH₂CH₂(NHMe₂)⁺]Ru(PPh₃)(μ-Cl)(μ-dppm)PdCl₂ (N3), Nafion/Cp(CO)Fe(μ-I)(μ-dppm)PdI₂ (N4) and Nafion/Cp(CO)Ru(μ-I)(μ-dppm)PtI₂ (N5) on glassy and vitreous carbon electrodes. Cyclic voltammetry and bulk electrolysis experiments were performed to assess the ability of these modified electrodes to electrocatalytically oxidize ethanol. Cyclic voltammograms using the N1-N5 modified glassy carbon electrodes displayed significant catalytic activity compared to oxidation of ethanol catalyzed by 1 in homogeneous solution. Bulk electrolysis of ethanol using electrodes coated with Nafion supported complexes 1-3 resulted in formation of the two- and four-electron oxidation products acetaldehyde and acetic acid, respectively, whilst bulk electrolysis using the complexes 4 and 5 produced only acetaldehyde.     

Trimetallic complexes featuring Group 10 tetracyanometallate dianions as bridging ligands

The trimetallic complexes {Ru(PPh₃)₂Cp}₂{μ-M(CN)₄} and {Ru(dppe)Cp*}₂{μ-M(CN)₄} (M = Ni, Pd, Pt) have been prepared from reactions of RuCl(PPh₃)₂Cp or RuCl(dppe)Cp* with the appropriate tetracyanometallate salt, and structurally characterised. While a similar reaction of FeCl(dppe)Cp with K₂[Pt(CN)₄] afforded {Fe(dppe)Cp}₂{μ-Pt(CN)₄}, the iron cyanide complex Fe(CN)(dppe)Cp was isolated as the only iron containing product from reaction of FeCl(dppe)Cp with K₂[Ni(CN)₄]. The trimetallic complexes can be oxidised in two sequential one-electron steps. Spectroelectrochemical experiments reveal weak NIR absorption bands in the mono-oxidised complexes which are not present in the binuclear complex K[Ru(dppe)Cp*{Pt(CN)₄}], and are therefore attributed to Ru^II → Ru^III charge transfer processes. The coupling parameter, V_ab, extracted using Hush-style analysis falls in the range 250 ± 50 cm⁻¹, consistent with the weak interaction between the Group 8 metal centres. The energy of the IVCT process is dominated by reorganisation energy of the Group 8 metal-ligand fragment.     

Rapid enrichment of (homo)acetogenic consortia from animal feces using a high mass-transfer gas-lift reactor fed with syngas

A gas-lift reactor having a high mass transfer coefficient (k _L a = 80.28 h^?1) for a relatively insoluble gas (carbon monoxide; CO) was used to enrich (homo)acetogens from animal feces. Samples of fecal matter from cow, rabbit, chicken, and goat were used as sources of inoculum for the enrichment of CO and H₂ utilizing microbial consortia. To confirm the successful enrichment, the Hungate roll tube technique was employed to count and then isolate putative CO utilizers. The results of this work showed that CO and H₂ utilizing consortia were established for each inoculum source after 8 days. The number of colony-forming units in cow, rabbit, chicken, and goat fecal samples were 3.83 × 10⁹, 1.03 × 10⁹, 8.3 × 10⁸, and 3.25 × 10⁸ cells/ml, respectively. Forty-two colonies from the animal fecal samples were screened for the ability to utilize CO/H₂. Ten of these 42 colonies were capable of utilizing CO/H₂. Five isolates from cow feces (samples 5, 6, 8, 16, and 22) were highly similar to previously unknown (homo)acetogen, while cow-7 has shown 99 % similarity with Acetobacterium sp. as acetogens. On the other hand, four isolates from chicken feces (samples 3, 8, 10, and 11) have also shown high CO/H₂ utilizing activity. Hence, it is expected that this research could be used as the basis for the rapid enrichment of (homo)acetogenic consortia from various environmental sources.     

Comparative reactivity study of cyclopentadienyl and fulvalene molybdenum complexes

The reactions of cis-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆ (1), in the presence of 1 equiv. of Me₃NO, and [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]₂ (2) with dppe produce CO labilization and formation of the dinuclear zwitterions trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₅(dppe) (3) and disproportionation species [(η⁵-C₅H₄CO₂Me)Mo(CO)₂(dppe)]⁺ [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]⁻ (4), respectively. Using the same method, the reactions of trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆I₂ and (η⁵-C₅H₄CO₂Me)Mo(CO)₃I with PPh₃ in the presence of 1 and 2 equiv. of Me₃NO yield trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₄(PPh₃)₂I₂ (5) and (η⁵-C₅H₄CO₂Me)Mo(CO)₂(PPh₃)I (6). The reactions of the several anionic carbonyl species {trans-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₆}²⁻, [(η⁵:η⁵-C₁₀H₈)W₂(CO)₆]²⁻ and [(η⁵-C₅H₄CO₂Me)Mo(CO)₃]⁻ with S₂Ph₂ give rise to the thiolate–fulvalene complexes cis-1,1′-[η⁵:η⁵-(C₅H₃CO₂Me)₂]Mo₂(CO)₄(μ-SPh)₂ (7) and (η⁵:η⁵-C₁₀H₈)W₂(CO)₆(SPh)₂ (8) and the thiolate-bridged dimer [(η⁵-C₅H₄CO₂Me)Mo(CO)(μ-SPh)]₂ (9). Treatment of 6 with 1 equiv. of HCCCCH and with (η⁵-C₅H₅)Mo(CO)(dppe)(CCCCH), in the presence of CuI at room temperature, afford the cyclopentadiene complexes (η⁵-C₅H₄CO₂Me)Mo(CO)₂(PPh₃)(CCCCH) (10) and (η⁵-C₅H₄CO₂Me)(PPh₃)(CO)₂Mo(CCCC)Mo(CO)(dppe)(η⁵-C₅H₅) (11), respectively. The reaction of (η⁵-C₅H₅)Mo(CO)(dppe)(CCCCH) with Co₂(CO)₈ yields [Co₂{μ-HC₂CC[Mo(CO)(dppe)(η⁵-C₅H₅)]}(CO)₆] (12). All the new compounds have been characterized by analytical and spectroscopic methods.