Iridium Atoms Research Articles

The Addition of Gold and Tin to Bismuth-Triiridium Carbonyl Complexes.

The reaction of Ir3(CO)9(μ3-Bi) with PhAu(NHC) (1), where NHC = 1,3-bis(2,6-diisopropylphenylimidazol-2-ylidene), has yielded the compound Ir3(CO)8(Ph)(μ3-Bi)[μ-Au(NHC)] (2) by the loss of one CO ligand and the oxidative addition of the Au-C (phenyl) bond of 1 to one of the iridium atoms. The Au(NHC) group bridges one of the Ir-Bi bonds of the cluster. On the basis of X-ray crystal structural analysis and molecular orbital and quantum theory of atoms in molecules calculations, the Au-Bi interaction was determined to be substantial and is comparable in character to the Ir-Bi and Ir-Ir bonds in this cluster. Compound 2 reacts with 2 equiv of HSnPh3 to yield the compound Ir3(CO)7(SnPh3)2(μ3-Bi)[μ-Au(NHC)](μ-H) (3), which contains two terminally coordinated SnPh3 ligands. Compound 3 reacts with H2O to yield the compound Ir3(μ3-Bi)(CO)7[μ-Ph2Sn(OH)SnPh2][μ-Au(NHC)] (4) by cleavage of a phenyl ring from each of the SnPh3 ligands and formation of a bridging OH group between the two tin atoms to form a chelating Ph2Sn(OH)SnPh2 ligand.

Binuclear cyclopentadienyliridium hydride chemistry: Terminal versus bridging hydride and cyclopentadienyl ligands

The cyclopentadienyliridium hydrides Cp2Ir2Hn (Cp=η5-C5H5; n=6, 4, 2, 0), and CpIrHn (n=4, 2) related to the experimentally known pentamethyl cyclopentadienyliridium hydrides Cp∗2Ir2Hn (Cp∗=η5-Me5C5; n=6, 2) and Cp∗IrH4 have been investigated by density functional theory. The lowest energy Cp2Ir2Hn (n=6, 4, 2) structures are predicted to have terminal Cp rings with the central Ir2 unit bridged by two hydrogen atoms. For the hexahydride Cp2Ir2H6, such doubly bridged Cp2Ir2(μ-H)2H4 structures are bent, leading to trans and cis structures of similar energies with an unbridged Cp2Ir2H6 isomer lying only ∼4kcal/mol above the bridged structures. This suggests fluxional behavior consistent with experimental data on the temperature dependence of the proton NMR spectrum of the closely related Cp∗2Ir2H6. The tetrahydride Cp2Ir2H4 is predicted to undergo slightly exothermic disproportionation into Cp2Ir2H6+Cp2Ir2H2 and thus not be a viable species. This is consistent with the failure to find any Cp∗2Ir2H4 in the Cp∗2Ir2Hn systems. The doubly bridged dihydride Cp2Ir2(μ-H)2 is a particularly favorable species since it lies more than 18kcal/mol in energy below any other isomer. Higher energy Cp2Ir2Hn (n=4, 2) structures have one or two bridging Cp rings and exclusively terminal hydrogen atoms. Related structures are the lowest energy structures for the hydride-free Cp2Ir2. A higher energy Cp2Ir2 structure consists of two CpIr units linked solely by an Ir–Ir bond. Analysis of the frontier molecular orbitals indicates this Ir–Ir bond to be the quadruple bond required to give each iridium atom the favored 18-electron configuration. However, this quadruple bond is a 2σ+2π bond with no δ components and thus differs from the σ+2π+δ quadruple bond found in the long-known Re2Cl82−.

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

There is significant interest in the catalytic properties of substituted iridium carbonyl clusters but little thermodynamic information available characterizing them. The low-energy isomers of Irx(PH3)y(CO)z (x=1, 2, 4) were investigated with density functional theory and correlated molecular orbital theory at the coupled cluster CCSD(T) level. The relative energies and ligand dissociation energies were calculated. Differences in relative energies are consequences of both electronic and steric effects of the phosphines and carbonyls. The calculations predict three fundamental structural types for Ir2(PH3)y(CO)z: C2v, C2, and D3d. Ten exchange–correlation functionals were used for the ligand dissociation energy calculations in addition to CCSD(T) for the smaller clusters. The ωB97X-D functional gave the most consistent ligand dissociation energies as compared with the CCSD(T) benchmark calculations, and, so it was used to predict the dissociation energies for larger clusters when CCSD(T) calculations were infeasible. The dissociation energies characteristic of Ir4(PH3)y(CO)z were in the range of ∼30 to ∼60kcal/mol. Dissociation of a bridging ligand often involved a hydrogen atom transfer from a phosphine to a coordinatively unsaturated iridium atom and a phosphine converting from a bridging site to an equatorial site. The products of such reactions are predicted to have lower relative energies than other isomers. Phosphines act as σ-electron donors, and there is a trend of an increase in carbonyl ligand dissociation energies as more phosphines are substituted in the small clusters.

The influence of the composition of eight-atom Pt–Ir clusters on the magnetic properties

The energetic stability, electronic structure and magnetic properties of Pt8–nIrn clusters have been investigated by employing the spin-polarised generalised gradient approximation. The cubic structure is expected to be the effective building block in Ir-rich clusters after optimisation extensively. The average binding energy of all the clusters presents the linear increment trend with iridium atoms, due to the stronger interaction between Ir atoms than Pt atoms. Bader charge analysis shows how tiny charge transfers from iridium to platinum. The atomic moments of Ir are larger than that of Pt, and the Ir-rich clusters show greater moments than the Pt-rich cluster, with the exception of Ir8 and Ir7Pt. A unique magnetic property is found in the Pt4Ir4 cluster, where two Pt atoms show antiferromagnetic alignment and the other atoms are found to be aligned ferromagnetically.

Nd39Ir10.98In36.02 – A complex intergrowth structure with CsCl- and AlB2-related slabs

Abstract The ternary indide Nd39Ir10.98In36.02 was synthesized by arc-melting and characterized by single crystal X-ray diffraction. Nd39Ir10.98In36.02 crystallizes with a new structure type: Pearson code oP172, Pbam, a = 3175.4(6), b = 3762.5(8), c = 378.02(8) pm, wR2 = 0.0828, 5544 F 2 values, and 262 variables. Although the structure contains 44 crystallographically independent sites, it can easily be explained as an intergrowth structure of CsCl and AlB2 related slabs. The larger indium atoms fill all distorted CsCl slabs. The trigonal prismatic (AlB2) slabs have no uniform size. The larger ones are filled by indium and the smaller ones by the iridium atoms. Additionally, one trigonal prism shows a mixed occupancy by indium and iridium. The crystal chemistry of Nd39Ir10.98In36.02 is discussed in the context of other intergrowth structures with the same simple slabs.

Coordination Complexes of Pentamethylcyclopentadienyl Iridium(III) Diiodide with Tin(II) Phthalocyanine and Pentamethylcyclopentadienyl Iridium(II) Halide with Fullerene C60– Anions

Synthetic approaches to iridium complexes of metal phthalocyanines (Pc) and fullerene anions have been developed to give three types of complexes. The compound{(Cp*IrIIII2)SnIIPc(2−)}·2C6H4Cl2 (1) (Cp* is pentamethylcyclopentadienyl) is the first crystalline complex of a metal phthalocyanine in which an iridium(III) atom is bonded to the central tin(II) atom of Pc via a Sn–Ir bond length of 2.58 Å. In (TBA+)(C60•–){(Cp*IrIIII2)SnIIPc(2−)}·0.5C6H14 (2), the {(Cp*IrIIII2)SnIIPc(2−)} units cocrystallize with (TBA+)(C60•–) to form double chains of C60•– anions and closely packed chains of {(Cp*IrIIII2)SnIIPc(2−)}. Interactions between the fullerene and phthalocyanine subsystems are realized through π–π stacking of the Cp* groups of {(Cp*IrIIII2)SnIIPc(2−)} and the C60•– pentagons. Furthermore, the spins of the C60•– are strongly antiferromagnetically coupled in the chains with an exchange interaction J/kB = −31 K. Anionic (TBA+){(Cp*IrIICl)(η2-C60–)}·1.34C6H4Cl2 (3) and (TBA+){(Cp*IrIII)(η2-C60–)}·1.3C6H4Cl2·0.2C6H14 (4) are the first transition metal complexes containing η2-bonded C60– anions, with the Cp*IrIICl and Cp*IrIII units η2-coordinated to the 6–6 bonds of C60–. Magnetic measurements indicate diamagnetism of the {(Cp*IrIICl)(η2-C60–)} and {(Cp*IrIII)(η2-C60–)} anions due to the formation of a coordination bond between two initially paramagnetic Cp*IrIICl or Cp*IrIII groups and C60•– units. DFT calculations support a diamagnetic singlet ground state of 4, in which the singlet–triplet energy gap is greater than 0.8 eV. DFT calculations also indicate that the C60 molecules are negatively charged.

Conversion of CO2and C2H6to Propanoic Acid on an Iridium-Modified Graphene Oxide Surface: Quantum-Chemical Investigation

Using density-functional theory, we performed calculations on a single-atom catalyst (SAC) comprising an iridium atom on a modified graphene oxide (Ir1-GO) surface to investigate the conversion of CO2 and C2H6 molecules to propanoic acid. The great catalytic activity of this surface is due to the strong adsorption of C2H6 and CO2 (−0.92 and −0.56 eV adsorption energies, respectively). First, C2H6 is dehydrogenated at an oxide site of the surface to form C2H5 + OH with a barrier of height 0.63 eV; the adsorbed CO2 then reacts with ethyl to form C2H5COO or COOC2H5 with barriers of 0.95 and 1.70 eV, respectively. Less likely, the adsorbed CO2 might be hydrogenated by hydroxyl to form HCOO or COOH, with energy barriers of 1.34 and 1.49 eV, respectively. We predict that the most likely path for the conversion of the adsorbed CO2 and ethane molecules on the Ir1-graphene oxide surface would involve the formation of propanoic acid (C2H5COOH). To understand the interaction between adsorbates and surfaces, we calculated and analyzed the local densities of states (LDOS) and the electron localization function (ELF).

Iridium Half-Sandwich Complexes with Di- and Tridentate Bis(pyridylimino)isoindolato Ligands: Stoichiometric and Catalytic Reactivity

A series of κ2-(N,N)-coordinated bis(2-pyridylimino)isoindolato (BPI) complexes [Cp*Ir(BPI)Cl], which possess “three-legged piano-stool” structures, with the iridium atom being coordinated by the Cp* ligand 2 × N and Cl, were prepared via deprotonation of the BPIH ligands with either potassium hydride or LDA and subsequent reaction with [Cp*IrCl2]2 in THF. Cationic complexes [Cp*Ir(BPI)]+ containing κ3-(N,N,N)-coordinated BPI ligands were prepared as well as complexes with bidentate-coordinated BPI ligands, where the chloride ligand was substituted by either neutral or anionic ligands. Substitution in the ortho-position of the PBI ligands led to the formation of cycloiridated κ3-(N,N,C) species. Upon substitution of the anionic ligand by triphenylphosphine, a product was obtained with a hitherto unobserved κ2-(N,N) coordination of oMe-BPI to the metal center via the deprotonated nitrogen atom of the isoindole unit and one of the imine nitrogen atoms of the BPI ligand. A series of (para-cymene) osmium half...

Electrogenerated chemiluminescence from heteroleptic iridium(III) complexes with multicolor emission.

Electrogenerated chemiluminescence (ECL) with different emission colors is important in the development of multichannel analytical techniques. In this report, five new heteroleptic iridium(III) complexes were synthesized, and their photophysical, electrochemical, and ECL properties were studied. Here, 2-(2,4-difluorophenyl)pyridine (dfppy, complex 1), 2-phenylbenzo[d]thiazole (bt, complex 2), and 2-phenylpyridine (ppy, complex 3) were used as the main ligands to tune the emission color, while avobenzone (avo) was used as the ancillary ligand. For comparison, complexes 4 and 5 with 2-phenylpyridine and 2-phenylbenzo[d]thiazole as the main ligand, respectively, and acetyl acetone (acac) as the ancillary ligand were also synthesized. All five iridium(III) complexes had strong intraligand absorption bands (π–π*) in the UV region (below 350 nm) and a featureless MLCT (d−π*) transition in the visible 400–500 nm range. Multicolored emissions were observed for these five iridium(III) complexes, including green, orange, and red for complexes 4, 5, 2, 1, 3, respectively. Density functional theory calculations indicate that the electronic density of the highest occupied molecular orbital is entirely located on the C^N ligands and the iridium atom, while the formation of the lowest unoccupied molecular orbital (LUMO) is complicated. The LUMO is mainly assigned to the ancillary ligand for complexes 1 and 3 but to the C^N ligand for complexes 2, 4, and 5. Cyclic voltammetry studies showed that all these complexes have a reversible oxidation wave, but no reduction waves were found in the electrochemical windows of CH2Cl2. The E1/2(ox) values of these complexes ranged from 0.642 to 0.978 V for complexes 3, 4, 2, 5, 1, (in increasing order) and are all lower than that of Ru(bpy)3(2+). Most importantly, when using tripropylamine as a coreactant, complexes 1–5 exhibited intense ECL signals with an emission wavelength centered at 616, 580, 663, 536, and 569 nm, respectively. In addition, complexes 1, 2, and 5 displayed approximately 2, 11, and 214 times higher ECL efficiencies than Ru(bpy)3(2+) under identical conditions.

Theoretical investigations on the structural, spectroscopic and photophysical properties of iridium (III) complexes with non-conjugated ligands toward blue phosphor in OLEDs

To achieve true blue-emitting iridium(III) complexes for organic light-emitting diodes, we theoretically designed a complex (dfbpy)2Ir(PˆN) (2, PˆN = 5-(diphenylphosphinomethyl)-3-(trifluoromethyl)pyrazole), dfbpy = 2-(2,4-difluorobenzyl)-pyridine), which derived from its prototype complex (dfppy)2Ir(PˆN) (1, dfppy: 2-(4,6-difluorophenyl)pyridine) by the insertion of methylene group between the pyridyl and phenyl segments. Then, their geometrical and electronic structure, absorption and emission were systematically and comparatively investigated using density functional theory calculations. It is found that the highest occupied molecular orbital (HOMO) (π component) of the functionalized complex 2 resides mainly on metal iridium atom and dfbpy ligand, whereas the lowest unoccupied molecular orbital (LUMO) is predominantly centered on π* orbital of cyclometalated dfbpy chelates. Our calculated results reveal the absorption at the 359 nm for 2 can be attributed to the mixture of MdπLπ*(dfbpy)CT (metal-ligand charge transition, MLCT) and ILπ(dfbpy)→π*(dfbpy)CT (intra-ligand charge transition, ILCT) transitions. In particular, the maxima emission for 2 is at 450 nm, which presents a blue shift up to 80 nm as compared to prototype complex 1, indicating the introduction of methylene group is a feasible strategy to archive true blue-emitting materials.

Fluorescence in rhoda- and iridacyclopentadienes neglecting the spin-orbit coupling of the heavy atom: the ligand dominates.

We present a detailed photophysical study and theoretical analysis of 2,5-bis(arylethynyl)rhodacyclopenta-2,4-dienes (1a–c and 2a–c) and a 2,5-bis(arylethynyl)iridacyclopenta-2,4-diene (3). Despite the presence of heavy atoms, these systems display unusually intense fluorescence from the S1 excited state and no phosphorescence from T1. The S1 → T1 intersystem crossing (ISC) is remarkably slow with a rate constant of 108 s–1 (i.e., on the nanosecond time scale). Traditionally, for organometallic systems bearing 4d or 5d metals, ISC is 2–3 orders of magnitude faster. Emission lifetime measurements suggest that the title compounds undergo S1 → T1 interconversion mainly via a thermally activated ISC channel above 233 K. The associated experimental activation energy is found to be ΔHISC = 28 kJ mol–1 (2340 cm–1) for 1a, which is supported by density functional theory (DFT) and time-dependent DFT calculations [ΔHISC(calc.) = 11 kJ mol–1 (920 cm–1) for 1a-H]. However, below 233 K a second, temperature-independent ISC process via spin–orbit coupling occurs. The calculated lifetime for this S1 → T1 ISC process is 1.1 s, indicating that although this is the main path for triplet state formation upon photoexcitation in common organometallic luminophores, it plays a minor role in our Rh compounds. Thus, the organic π-chromophore ligand seems to neglect the presence of the heavy rhodium or iridium atom, winning control over the excited-state photophysical behavior. This is attributed to a large energy separation of the ligand-centered highest occupied molecular orbital (HOMO) and lowest unoccupied MO (LUMO) from the metal-centered orbitals. The lowest excited states S1 and T1 arise exclusively from a HOMO-to-LUMO transition. The weak metal participation and the cumulenic distortion of the T1 state associated with a large S1–T1 energy separation favor an “organic-like” photophysical behavior.

Effect of the Reduction Temperature on the Activity and Selectivity of Titania-Supported Iridium Nanoparticles for Methylcyclopentane Reaction

The catalytic performance of Ir/TiO2 reduced at low (573 K, LTR) and high temperature (773 K, HTR) was studied in the methylcyclopentane (MCP) reaction at atmospheric pressure in a flow system. Ir/Al2O3 was used as the reference catalyst. Catalysts were prepared by deposition–precipitation with urea and characterized by ICP, H2-TPR, HAADF-STEM, Cs-STEM, and DRIFTS. For LTR samples, the activity follows the order Ir/TiO2 > Ir/Al2O3, and at low conversion and temperature, ring opening (RO) of MCP is selective (2MP/3MP = 2.7; n-H/3MP = 0.05) with SRO = 100%. As the reaction temperature increased, C1–C5 products appeared but Ir/TiO2 was still more selective to RO products than Ir/Al2O3. Ir/TiO2 HTR was significantly less active, with SRO = 100% and a product distribution approaching a nonselective behavior with n-H/3MP = 1. This was not observed in the case of Ir/Al2O3 HTR. The structure of Ir/TiO2 HTR included nanoparticles, clusters of few atoms, and isolated iridium atoms. The results were analyzed in ligh...

Selective molecular recognition by nanoscale environments in a supported iridium cluster catalyst.

The active sites of enzymes are contained within nanoscale environments that exhibit exquisite levels of specificity to particular molecules. The development of such nanoscale environments on synthetic surfaces, which would be capable of discriminating between molecules that would nominally bind in a similar way to the surface, could be of use in nanosensing, selective catalysis and gas separation. However, mimicking such subtle behaviour, even crudely, with a synthetic system remains a significant challenge. Here, we show that the reactive sites on the surface of a tetrairidium cluster can be controlled by using three calixarene-phosphine ligands to create a selective nanoscale environment at the metal surface. Each ligand is 1.4 nm in length and envelopes the cluster core in a manner that discriminates between the reactivities of the basal-plane and apical iridium atoms. CO ligands are initially present on the clusters and can be selectively removed from the basal-plane sites by thermal dissociation and from the apical sites by reactive decarbonylation with the bulky reactant trimethylamine-N-oxide. Both steps lead to the creation of metal sites that can bind CO molecules, but only the reactive decarbonylation step creates vacancies that are also able to bond to ethylene, and catalyse its hydrogenation.

Ionization cross section measurements for autoionizing states of iridium and rhenium

New autoionizing states for neutral iridium and rhenium atoms were observed in the continuum structure near the first ionization limit by using a two-colour two-step laser resonance ionization technique. The saturation curves for the autoionizing states were measured, and the ionization cross sections were experimentally determined by solving the rate equations for the ground, intermediate, and autoionizing state populations. Efficient ionization schemes are expected to be useful for applications such as laser ion sources of unstable nuclei.

Geometries, stabilities, electronic and magnetic properties of small PdnIr (n = 1–8) clusters from first-principles calculations

The geometrical structures, relative stabilities, electronic and magnetic properties of small PdnIr (n = 1–8) clusters have been systematically investigated using density functional theory at the B3PW91 level. The optimised geometries show that the lowest-energy structures of PdnIr clusters prefer a three-dimensional configuration. The relative stability of these clusters was examined by analysis of the binding energies per atom, fragmentation energies, the second-order difference of energies and the HOMO–LUMO energy gaps as a function of cluster size. The obtained results exhibit that the Pd2Ir, Pd3Ir and Pd5Ir clusters are more stable than their neighbouring clusters. The energy gap of the Pd2Ir cluster is the largest of all the clusters (2.258 eV). In addition, the charge transfers, vertical ionisation potentials, vertical electron affinities and chemical hardness were calculated and discussed. The magnetism calculations indicate that the total magnetic moment of PdnIr clusters is mainly localised on the iridium atom for Pd1–6Ir clusters. Meanwhile, the 5d orbital plays the key role in the magnetic moment of the iridium atom.

High-pressure formation and stabilization of binary iridium hydrides

A new class of binary iridium hydrides (IrxHy) is investigated in the 1 atm to 125 GPa pressure range at the ab initio level, using DFT. Upon compression a number of hydrides are predicted to stabilize in the excess hydrogen environment. Static stabilization pressure is calculated to be ∼14 and ∼5 GPa at which a dihydride (Ibam, Z = 2) and a trihydride (P63mc, Z = 2) stabilize thermodynamically, respectively. In both the di- and the trihydride iridium and hydrogen atoms form short contacts in the range typical for covalent interactions. All of the reported hydrides exhibit metallic character with the notable exception of IrH3 (P63mc, Z = 2) which exhibits a non-zero band gap and a molecular character at intermediate pressures.

Lead-flux Growth of Eu4Ir8As7 Crystals

Single crystals of the new arsenide Eu4Ir8As7 were grown from a lead flux. The structure was refined on the basis of single-crystal X-ray diffractometer data: Ca4Ir8P7 type, P21=m, a=1311.3(1), b = 408:4(1), c = 1360:3(1) pm, β = 98:45(1)°, wR2=0.0640, 1985 F2 values, 95 variables. The iridium and arsenic atoms in the Eu4Ir8As7 structure build up a complex three-dimensional, covalently bonded [Ir8As7] network with Ir-As distances ranging from 239 to 260 pm. Each iridium atom has three or four arsenic neighbors in slightly distorted trigonal-planar or tetrahedral coordination. The four crystallographically independent europium atoms fill cavities of coordination numbers 12, 13, and 15 (2) within the [Ir8As7] network. Parts of the Eu4Ir8As7 structure resemble known simpler structure types, and one can describe the Eu4Ir8As7 structure as an intergrowth variant of CaBe2Ge2-, TiNiSi- and AlB2-related slabs.

Structures and Bonding of η2-Bridging CO Ligands and Their Influence on the Structures and Rearrangements of Higher Nuclearity Metal Carbonyl Cluster Complexes

Three products were obtained from the reaction of IrRu3(CO)13(μ3-H) with P(But)3 in a hexane solution at reflux for 30 min. These have been identified as IrRu3(CO)12[P(But)3](μ-H) (1; 15% yield), IrRu2(CO)9[P(But)3](μ-H) (2; 29% yield), and IrRu3(CO)10(μ3-η2-CO)[P(But)3]2(μ-H) (3; 19% yield). Compound 1 is simply a P(But)3 derivative of IrRu3(CO)13(μ3-H). Compound 2 is electronically unsaturated and has a vacant coordination site located on the iridium atom. Compound 3 contains a butterfly tetrahedral cluster of four metal atoms with a rare η2 triply bridging CO ligand. Compound 3 reacts with Ru(CO)5 to yield the higher nuclearity cluster complex IrRu4(CO)12(μ4-η2-CO)[P(But)3]2(μ3-H) (4), which contains five metal atoms arranged in the form of an iridium-capped butterfly tetrahedron of four ruthenium atoms. Compound 4 contains a η2-quadruply bridging CO ligand. Compound 4 reacts with CO to yield the compound IrRu4(CO)14P(But)3(μ4-η2-CO)(μ-H), 5 which contains five metal atoms in the form of a spiked-tetra...

Semibridging Phenyl Ligands in Iridium–Copper and Iridium–Silver Cluster Compounds: Synthesis, Structures, and Bonding

Reactions of the tetrairidium anion [Ir4(CO)11(Ph)]– (1) with [Cu(NCMe)4][BF4] and Ag[NO3] have yielded the new iridium–copper and iridium–silver complexes Ir4(CO)11(μ-η1-Ph)[μ3-Cu(NCMe)] (2) and [Et4N][{Ir4(CO)11Ph}2(μ4-Ag)] (3), respectively. Compound 2 consists of a tetrahedral Ir4 cluster with a Cu(NCMe) group bridging one of the Ir3 triangular faces of the cluster and a semibridging η1-phenyl ligand that is σ–π-coordinated as a bridge across one of the Ir–Cu bonds. The complex anion of 3 contains two Ir4(CO)11Ph anions linked by a single quadruply bridging silver atom that has adopted a bow-tie geometry between the four iridium atoms. It contains two terminally coordinated σ-phenyl ligands. Compound 3 reacts with a second equivalent of Ag[NO3] to yield the uncharged complex [Ir4(CO)11]2(μ4-Ag)(μ-Ag)(μ3-Ph)(μ-Ph) (4), which contains two Ir4(CO)11 clusters linked by a quadruply bridging silver atom and one triply bridging Ph ligand. The second Ag atom in 4 is an edge bridge on one of the Ir4 clusters, and the second Ph ligand bridges an Ir–Ag bond to it. When it is dissolved in NCMe, compound 4 is split in two and adds 1 equiv of NCMe to the Ag atom in each half to form the compound Ir4(CO)11(η1-Ph)[μ3-Ag(NCMe)] (5; 73% yield). Unlike 2, the phenyl ligand in 5 is terminally coordinated. The NCMe ligand is coordinated to the Ag atom. When 4 was treated with PPh3, the complex Ir4(CO)11(μ-η1-Ph)[μ3-Ag(PPh3)] (6) was obtained in 87% yield. The cluster of 6 is structurally similar to that of 5 except that the phenyl ligand has adopted a semibridging coordination to the silver atom, similar to that found between the phenyl ligand and the copper atom in 2. All of the new products were characterized by single-crystal X-ray diffraction analyses. The bonding of the bridging phenyl ligands to the clusters in 2 and 4 was analyzed by DFT computational methods.

Di-μ2-chlorido-bis[chlorido(η5-2,3,4,5-tetramethyl-1-propylcyclopentadienyl)iridium(III)

The asymmetric unit of the title complex, [Ir2Cl4(C12H19)2], a versatile starting material for the preparation of uniquely substituted penta­alkyl­cyclo­penta­dien­yl–iridium complexes, consists of an iridium(III) atom, a substituted cyclo­penta­dienyl ligand and two chlorine ligands. The full dimer is generated by an inversion center. In the dimer, the two IrIII atoms and two bridging Cl atoms form a perfectly planar ring. The two IrIII atoms and the two terminal Cl atoms also form a rigorous plane that is orthogonal [89.48 (3)°] to the Ir2Cl2 ring. The plane of the cyclo­penta­dienyl ligand forms a dihedral angle of 54.06 (7)° with respect to the Ir2Cl2 ring.