Formation Of Ir Research Articles

Spectroelectrochemistry of Water Oxidation Kinetics in Molecular versus Heterogeneous Oxide Iridium Electrocatalysts.

Water oxidation is the step limiting the efficiency of electrocatalytic hydrogen production from water. Spectroelectrochemical analyses are employed to make a direct comparison of water oxidation reaction kinetics between a molecular catalyst, the dimeric iridium catalyst [Ir2(pyalc)2(H2O)4-(μ-O)]2+ (IrMolecular, pyalc = 2-(2′pyridinyl)-2-propanolate) immobilized on a mesoporous indium tin oxide (ITO) substrate, with that of an heterogeneous electrocatalyst, an amorphous hydrous iridium (IrOx) film. For both systems, four analogous redox states were detected, with the formation of Ir(4+)–Ir(5+) being the potential-determining step in both cases. However, the two systems exhibit distinct water oxidation reaction kinetics, with potential-independent first-order kinetics for IrMolecular contrasting with potential-dependent kinetics for IrOx. This is attributed to water oxidation on the heterogeneous catalyst requiring co-operative effects between neighboring oxidized Ir centers. The ability of IrMolecular to drive water oxidation without such co-operative effects is explained by the specific coordination environment around its Ir centers. These distinctions between molecular and heterogeneous reaction kinetics are shown to explain the differences observed in their water oxidation electrocatalytic performance under different potential conditions.

Density functional theory insights into the bonding of CH3OH and CH3O with Ir(111) surface

Introduction: Understanding the adsorption characteristics of CH3OH and CH3O on the noble metal surfaces is essential for designing better catalysts for the on-board production of hydrogen from CH3OH. This study aims to provide insights into the adsorption behavior of these molecules on Ir(111) surface.
 Methods: The adsorption structure, the adsorption energy, and the bonding mechanism of CH3OH and CH3O with Ir(111) surface were investigated by means of the density functional theory (DFT) calculations and the Bader charge analysis.
 Results: The DFT results show that the adsorption of CH3OH and CH3O is driven by the formation of Ir–O bond at the top site of the surface by the overlap of O-2p and Ir-5d orbitals. The overlap of these orbitals is greater in the absorption of CH3O, resulting in stronger adsorption energy of CH3O (2.23 eV vs. 0.32 eV). In agreement with the adsorption strength, the charge transfer from CH3O to the surface is significantly larger than from CH3OH (0.386 e vs. 0.073 e).
 Conclusion: Although driven by the same adsorption bond, the difference in the molecular characteristics leads to a marked difference in the absorption strength of CH3OH and CH3O on Ir(111) surface.

INSULIN RESISTANCE AS AN INDICATOR OF DIFFERENTIATION FOR THE FORMATION OF RISK GROUPS FOR NON-ALCOHOLIC FATTY LIVER DISEASE IN PATIENTS WITHOUT TYPE 2 DIABETES MELLITUS, AS A PART OF ONTOLOGICAL MODEL OF NON-ALCOHOLIC FATTY LIVER DISEASE

The aim: Using cluster analysis, to identify a high-risk group for NAFLD and develop a differential approach to examination, treatment and prevention of the disease based on IR indices, among NAFLD and non-NAFLD patients without type 2 diabetes mellitus (T2DM). Materials and methods: Clinical, anthropometric, laboratory methods, ultrasound, computational and statistical techniques were applied. Results: Cluster analysis was performed on the laboratory tests results: glucose, insulin, HOMA-IR index, HOMA2 Calculator (%B – beta-cell function, %S – insulin sensitivity, IR – insulin resistance). 5 groups of patients were formed, according to increasing HOMA-IR index and IR. Group II was found to be transient in IR formation, it included the majority of non-NAFLD patients (87%), and we consider it to be the risk group for NAFLD. Group V – with the highest IR scores, where 92% of patients had NAFLD and 73% had a high Fatty Liver Index – is considered to be a very high-risk group for developing T2DM. Conclusions: 1. According to the results of cluster analysis, 5 groups of patients with different IR levels were identified. 2. In the second group, where non-NAFLD patients predominate, insulin resistance begins to form. 3. Groups III and IV – patients with high HOMA-IR index – had significant ultrasound findings indicating hepatic steatosis. 4. Group V included patients with NAFLD, with high HOMA-IR index and the highest risk of developing T2DM.

Lattice dynamics and structural transition of the hyperhoneycomb iridate β−Li2IrO3 investigated by high-pressure Raman scattering

We report a polarized Raman scattering study of the lattice dynamics of $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ under hydrostatic pressures up to 7.62 GPa. At ambient pressure, $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ exhibits the hyperhoneycomb crystal structure and a magnetically ordered state of spin-orbit entangled ${J}_{\mathrm{eff}}$ = 1/2 moments that are strongly influenced by bond-directional (Kitaev) exchange interactions. At a critical pressure of $\ensuremath{\sim}\phantom{\rule{0.16em}{0ex}}4.1$ GPa, the phonon spectrum changes abruptly, consistent with the reported structural transition into a monoclinic, dimerized phase. A comparison to the phonon spectra obtained from density-functional calculations shows reasonable overall agreement. The calculations also indicate that the high-pressure phase is a nonmagnetic insulator driven by the formation of Ir--Ir dimer bonds. Our results thus indicate a strong sensitivity of the electronic properties of $\ensuremath{\beta}\ensuremath{-}{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ to the pressure-induced structural transition.

Pressure-induced collapse of the spin-orbital Mott state in the hyperhoneycomb iridate β−Li2IrO3

Hyperhoneycomb iridate $\beta$-Li$_2$IrO$_3$ is a three-dimensional analogue of two-dimensional honeycomb iridates, such as $\alpha$-Li$_2$IrO$_3$, which recently appeared as another playground for the physics of Kitaev-type spin liquid. $\beta$-Li$_2$IrO$_3$ shows a non-collinear spiral ordering of spin-orbital-entangled $J_{\rm eff}$ = 1/2 moments at low temperature, which is known to be suppressed under a pressure of $\sim$2 GPa. With further increase of pressure, a structural transition is observed at $P_{\rm S}$ $\sim$ 4 GPa at room temperature. Using the neutron powder diffraction technique, the crystal structure in the high-pressure phase of $\beta$-Li$_2$IrO$_3$ above $P_{\rm S}$ was refined, which indicates the formation of Ir$_2$ dimers on the zig-zag chains, with the Ir-Ir distance even shorter than that of metallic Ir. We argue that the strong dimerization stabilizes the bonding molecular orbital state comprising the two local $d_{zx}$-orbitals on the Ir-O$_2$-Ir bond plane, which conflicts with the equal superposition of $d_{xy}$-, $d_{yz}$- and $d_{zx}$- orbitals in the $J_{\rm eff}$ = 1/2 wave function produced by strong spin-orbit coupling. The results of resonant inelastic x-ray scattering (RIXS) measurements and the electronic structure calculations are fully consistent with the collapse of the $J_{\rm eff}$ = 1/2 state. A subtle competition of various electronic phases is universal in honeycomb-based Kitaev materials.

Identification of the active complex for CO oxidation over single-atom Ir-on-MgAl2O4 catalysts

Supported single atoms provide an opportunity to design new heterogeneous catalysts while optimizing the utilization of noble metals. However, identification of the active single-atom structure is required for understanding the reaction mechanism and guiding catalyst design. Here, we use in situ infrared spectroscopy, operando X-ray absorption spectroscopy and quantum chemical calculations to identify the active single-atom complex as well as the resting state of the Ir/MgAl2O4 catalysts during the low-temperature CO oxidation. In contrast to poisoning of iridium nanoparticles by CO, here we show that the formation of Ir(CO) on single atoms results in a different reaction mechanism and high activity for low-temperature CO oxidation. This is due to the ability of single atoms to coordinate with multiple ligands, where Ir(CO) provides an interfacial site for facile O2 activation between Ir and Al and lowers the reaction barrier between gas-phase CO(g) and *O in Ir(CO)(O) through an Eley–Rideal mechanism. Single-atom catalysts are receiving much attention, but insights into their active sites or the differences in reactivity with conventional nanoparticles are still controversial. Now, operando studies on CO oxidation with Ir/MgAl2O4 accompanied by computational investigations reveal important features of this class of catalyst.

Study of the Coordination Modes of Hybrid NNCp Cyclopentadienyl/Scorpionate Ligands in Ir Compounds.

A new coordination mode for the hybrid scorpionate/cyclopentadienyl ligand bpzcp, [bpzcp = 2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethylcyclopentadienyl] is observed in iridium complexes. The reaction of the lithium precursor, [Li(bpzcp)(THF)], with a range of [IrCl(diene)]2 compounds leads to an unprecedented binding mode of the hybrid scorpionate/cyclopentadienyl ligand as η5-Cp-coordinated and the formation of Ir(I) derivatives [Ir(η5-Cp-bpzcp)(η4-cod)] (1), [Ir(η5-Cp-bpzcp){η4-CH2═C(Me)C(Me)═CH2}] (2), [Ir(η5-Cp-bpzcp)(η2-coe)2] (3), and [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2] (4). The Ir(I) complex 4 reacts with CO or bromine to afford the compound [Ir(η5-Cp-bpzcp)(CO)2] (5) and the 18e- Ir(III) complex [Ir(κ-N-η5-Cp-bpzcpBr2)Br2] (6), respectively. Reaction of the iridium compounds (2-4) with CuI or [PdCl2(CH3CN)2] yields the heterobimetallic iridium-copper or iridium-palladium complexes [Ir(η5-Cp-bpzcp){η4-CH2═C(Me)C(Me)═CH2}(μ-bpzcp){CuI(κ2-NN-bpzcp)}] (7), [Ir(η5-Cp-bpzcp)(η2-coe)2}(μ-bpzcp){CuI(κ2-NN-bpzcp)}] (8), [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2}(μ-bpzcp){CuI(κ2-NN-bpzcp)}] (9), [Ir(η5-Cp-bpzcp)(coe)2}(μ-bpzcp){PdCl2(κ2-NN-bpzcp)}] (10), and [Ir(η5-Cp-bpzcp)(η2-CH2═CH2)2(μ-bpzcp){PdCl2(κ2-NN-bpzcp)}] (11). All products were characterized by spectroscopic methods and the X-ray crystal structures of 1, 2, 3, 4, and 6 were also established.

The reactivity of coordinatively unsaturated iridium methylene complex Ir CH2[N(SiMe2CH2PPh2)2]: A quantum chemistry study

Abstract The mechanisms for the reactions of the coordinatively unsaturated iridium methylene complex Ir CH2[N(SiMe2CH2PPh2)2] with a variety of small molecules including H2, PMe3, CO, Al2Me6, and CH3I have been investigated by the density functional theory (DFT) calculations. The calculation results showed that the reaction of methylene complex with H2 generates the trihydride amine IrH3[HN(SiMe2CH2PPh2)2] via a series of oxidative addition and reductive elimination steps. The reaction of methylene complex with PMe3 produces the square planar complex Ir(PMe3)[N(SiMe2CH2PPh2)2] and CH2 PMe3, and the latter can further react with methylene complex to give ethene. The reaction of methylene complex with CO results in the formation of Ir(CO)[(CH2PPh2CH2SiMe2NSiMe2CH2PPh2)] by the formation of C P bond. The reactions of methylene complex with Al2Me6 and methyl iodide were also examined, and the oxidative addition step can afford a metal–carbon bond that undergoes a C C bond forming migratory insertion to ultimately lead to the formation of ethene. Present study can provide new insights into the reactivity of transition metal methylene complex.

The role of systemic inflammation in the pathogenesis of insulin resistance and metabolic syndrome in patients with chronic hepatitis C.

To determine the role of nonspecific inflammation in the formation of IR and metabolic syndrome in patients with chronic hepatitis C. The study included 205 patients with CHC aged 18 to 69 years. Patients with CHC are randomized into two groups depending on the presence of IR: group 1 - patients with a HOMA index ≥2.77, which corresponded to IR (n=110); group 2 (n=95). The levels of serum iron, C-reactive protein (CRP), serum ferritin and adipose tissue hormones [leptin, resistin, adiponectin and tumor necrosis factor-α (TNF-α)] were additionally investigated. At all stages of development of IR, nonspecific inflammation was detected (according to ferritin, CRP and serum iron), increasing with increasing HOMA index [Homeostasis Model of Assessment - Insulin Resistance (HOMA-IR)] (Matthews D., 1985), metabolic syndrome and its components. In the analysis of indicators in patients with chronic hepatitis C with a body mass index <25 kg/m2, conjugacy of IR with low-intensity inflammation, high viral load and hypersecretion of TNF-α was detected. Given the high predictor role of CRP indicators in predicting IR, it should be used as a surrogate screening marker of IR in patients with chronic hepatitis C and should be actively treated for violations.

Crystal structure and thermal properties of K3[Ir(C2O4)3]·4.25H2O and K3[Ir(C2O4)3]·0.5KCl·4H2O

The structures of K3[Ir(C2O4)3]·0.5KCl·4H2O and K3[Ir(C2O4)3]·4.25H2O were determined by single-crystal X-ray diffraction. Thermal transformations of the compounds were studied by several physical methods. Single-step coordination sphere decomposition followed by formation of Ir and CO2 was shown. It is found that the redox process with CO2 release passes easier for K3[Ir(C2O4)3]·0.5KCl compound than for K3[Ir(C2O4)3] one.

Support effect on the bimetallic structure of Ir–Re catalysts and their performances in glycerol hydrogenolysis

Comparative study was made between the bimetallic Ir–Re catalyst supported on amorphous silica-alumina (ASA) and the ones supported on de-aluminated ASA (D-ASA) to elucidate the effects of surface Al in the support on the Ir–Re structure and their catalytic behavior in glycerol hydrogenolysis. The Ir–Re interaction is greatly inhibited because of the stronger interaction between Re species and (Si-)Al-OH sites on ASA surface, resulting in the appearance of highly dispersed Re clusters and large Ir crystals after reduction. The barely synergy between the isolated Ir and Re metals in addition to the decreased metal dispersion restrains the glycerol hydrogenolysis reaction over Ir–Re/ASA. On the other hand, the retained mobility of Re species on ‘inert’ D-ASA supports offers the intimate contact between Ir and Re species and hence the formation of Ir–Re alloy catalysts after reduction, promoting greatly the synergy between Ir and Re species in glycerol hydrogenolysis.

Accurate Prediction of IrH Bond Dissociation Enthalpies by Density Functional Theory Methods

AbstractThe iridium hydride complexes have been extensively used in organic reactions, such as oxidation and hydrogenation reactions. In many of these reactions, the dissociation or formation of IrH bond plays an important role in determining the overall reaction rates and yields. In the present study, the accuracy of different theoretical methods for prediction of IrH bond strengths has been examined on the basis of the previously reported IrH BDEs of 17 different complexes. Comparing the performance of different DFT functionals (e.g. B3LYP, TPSS, M06), different basis sets (including the different effective core potentials (ECP) on Ir and I atoms, and the total electron basis sets on the other atoms), and different solvation models (SMD, CPCM, and IEFPCM) in solution phase single point calculations, we found that the gas‐phase calculation with TPSS/(LanL2DZ: 6‐31G(d)) method is relatively more accurate than the other gas‐phase calculation methods, and can well simulate the IrH BDEs in low‐polarity solvents (such as chlorobenzene and dichloroethane). Finally, efforts were put in analyzing the structure‐activity relationships between the ligand structure (around Ir center) and the IrH BDEs. We wish the present study could benefit future studies on the Ir‐H complexes involved organic reactions.

Generating Parahydrogen-Induced Polarization Using Immobilized Iridium Complexes in the Gas-Phase Hydrogenation of Carbon–Carbon Double and Triple Bonds

Immobilized iridium complexes synthesized using [Ir(COD)Cl]2 by anchoring on hydrous and anhydrous silica gels were studied in terms of generating parahydrogen-induced polarization (PHIP) in the gas-phase hydrogenation of propylene and propyne. Distinguishing differences in the hydrogenations of carbon–carbon double and triple bonds were found. It has been shown that in the double bond hydrogenation both catalysts are very active even at 25 °C. The reaction yield in continuous flow experiments is more than 70 %, whereas the obtained PHIP degrees are very low. In the case of the triple bond hydrogenation, a more or less active hydrogenation reaction was observed at relatively high temperatures (≈70–80 °C) for the catalyst immobilized on anhydrous silica, while the catalyst immobilized on hydrous silica was inactive at these temperatures. Contrary to the double bond hydrogenation, the triple bond hydrogenation provided significant signal enhancements observed in 1H nuclear magnetic resonance spectra for the signals corresponding to protons of vinyl fragments of product propylene in both PASADENA and ALTADENA experiments. The catalyst, however, is not stable under the triple bond hydrogenation reaction conditions, and deactivates within several minutes. It was also found that at higher temperatures (100–120 °C), this catalyst demonstrates a reactivation most likely associated with the reduction of Ir(I) that results in the formation of Ir(0) surface metal nanoparticles.

Aliphatic pincer-type POCOP ligands and their complexation behaviour with iridium: Crystal structure of an iridium(III) phosphinite complex

Reaction of 2 equivalents of 1,3-bis-(di- tert-butylphosphinito)-2-methyl-propane ( 1a) with [Ir(COD)Cl] 2 affords the first aliphatic diphosphinite PCP pincer complex with iridium, Ir(H){( t-Bu 2POCH 2) 2C(Me)}Cl ( 2). The poor yield of 2 is partly explained by the formation of a di-nuclear byproduct [IrCl(COD)] 2( μ 2-{( t-Bu 2POCH 2) 2CH(Me)}) ( 3). Reaction of 1,3-bis-(di- iso-propylphosphinito)-2-methyl-propane ( 1b) under the same condition does not give any cyclometallation, and reaction with IrCl 3·H 2O in DMF leads to complete decomposition of the pincer ligand under the formation of Ir(H)( i-Pr 2P(OH)) 3(CO) ( 4), underpinning the comparatively low thermal stability of aliphatic phosphinite pincer systems.

Evidence for C−H···X−Ir (X = Cl or I) Hydrogen Bonding between Imidazolium Salts and Iridium-Bound Halides and Formation of Ir(I) NHC Complexes

Reactions between an N,N′-adamantyl-substituted bis(imidazolium) diiodide (CHimidCHCHimid)I2 (1) and the dinuclear iridium(I) complex ([Ir(μ-X)(cod)]2 [X = Cl, I (prepared in situ)] in the absence ...

Growth Behavior and Interfacial Character of Ir<SUB>3</SUB>Y Precipitates in the Ir<SUB>2</SUB>Y Lave Phase Matrix

A C15 Laves phase Ir 2 Y that forms in the Ir-Y binary system develops off-stoichiometry toward the Ir-rich composition at high temperatures, and its range of homogeneity becomes narrow with decreasing temperatures. One consequence of this solubility behavior is the formation of Ir 3 Y precipitates within the Ir 2 Y matrix of an Ir-30mol%Y alloy. The orientation relationship between Ir 3 Y and Ir 2 Y has been identified as: (0001) Ir3Y // (111) Ir2Y and [2110] Ir3Y // [110] Ir2Y . The similarity in the crystal structures of the two phases yields a plate-like Ir 3 Y precipitate showing a typical Widmanstatten structure. The growth of the precipitates has been suggested to follow the ledge mechanism. The interfacial character between the two phases has been identified in this study.

Alkyl dehydrogenation in iridium tri-cyclopentyl phosphines

The iridium cyclooctadiene complex incorporating a tricyclopentyl phosphine ligand (PCyp 3), Ir(η 2:η 2-C 8H 12)(PCyp 3)Cl, has been prepared. Removal of the chloride from this complex using Na [ BAr F 4 ] [ Ar F = C 6 H 3 ( CF 3 ) 2 ] in CH 2Cl 2/arene solvent results in dehydrogenation (C–H activation followed by β-H transfer) of one of the alkyl phosphine rings and formation of the complexes [ Ir ( η 6 - C 6 H 5 X ) { PCyp 2 ( η 2 - C 5 H 7 ) } ] [ BAr F 4 ] (X = H, F) which contain a hybrid phosphine–alkene ligand. These complexes are formed alongside another product (5–20% yield) that has been identified as [ Ir ( η 2 : η 2 - C 8 H 12 ) { PCyp 2 ( η 2 - C 5 H 7 ) } ] [ BAr F 4 ] , which can be prepared in high yield by an alternative, and slightly modified, route. This complex is with a minor isomer that has been tentatively identified as [ Ir ( η 2 : η 3 - C 8 H 11 ) ( H ) { PCyp 2 ( η 2 - C 5 H 7 ) } ] [ BAr F 4 ] , which results from allylic C–H activation of cyclooctadiene. Addition of H 2 to [ Ir ( η 2 : η 2 - C 8 H 12 ) { PCyp 2 ( η 2 - C 5 H 7 ) } ] [ BAr F 4 ] and its isomer in arene solvent (C 6H 5X, X = F, H) forms the dihydrido η 6-arene Ir(III) complexes [ Ir ( H ) 2 ( η 6 - C 6 H 5 X ) ( PCyp 3 ) ] [ BAr F 4 ] . In contrast, hydrogenation in CH 2Cl 2 alone results in the formation of Ir ( H ) 2 ( PCyp 3 ) { η 6 - ( C 6 H 3 ( CF 3 ) 2 ) BAr F 3 } in which the [ BAr F 4 ] - anion is now acting as a ligand through one of its aryl rings. The fluorobenzene complex [ Ir ( H ) 2 ( η 6 - C 6 H 5 F ) ( PCyp 3 ) ] [ BAr F 4 ] can be cleanly converted to [ Ir ( η 6 - C 6 H 5 F ) { PCyp 2 ( η 2 - C 5 H 7 ) } ] [ BAr F 4 ] by addition of the hydrogen acceptor tert-butylethene (tbe).

Metal Carbonyl Cluster Synthesis in Nanocages: Spectroscopic Evidence of Intermediates in the Formation of Ir4(CO)12in Zeolite NaY

The assembly of Ir4(CO)12 from Ir(CO)2(acac) precursors in the supercages of zeolite NaY was investigated by extended X-ray absorption fine structure (EXAFS) and in-situ infrared (IR) spectroscopies. The data show that the conditions of pretreatment of the zeolite significantly affect the formation process of Ir4(CO)12. When the zeolite was initially largely dehydrated, so that the precursor molecules were well dispersed in the zeolite cages, dimeric intermediates in the formation of Ir4(CO)12 (approximated as Ir2(CO)8) were observed by both IR and EXAFS spectroscopies. In contrast, when the zeolite initially contained a substantial amount of water, the resultant Ir4 clusters were formed faster than those in dehydrated zeolite, and evidence of intermediates was not observed. The results show how synthesis in the confined spaces of the zeolite nanoporesin the absence of solventsaffords opportunities to control and elucidate the chemistry, different from that in solution.

Synthesis of η2:σ2-Diene Complexes of Iridium(III) by the Reaction of η4:π2-Diene Iridium(I) Species with Lewis Bases

Treatment of the η4-diene complex TpMe2Ir(η4-CH2C(Me)C(Me)CH2) (1) with a variety of soft and hard Lewis bases induces an unprecedented change in the binding mode of the diene ligand from η4:π2 to η2:σ2 and formation of Ir(III) derivatives of composition TpMe2Ir(η2:σ2-CH2C(Me)C(Me)CH2)(L) (4) (L = CO, PMe3, MeCN, C5H5N, etc.). Similar reactivity is exhibited by the analogous compounds TpMe2Ir(η4-CH2C(Me)CHCH2) (2) and TpMe2Ir(η4-CH2CHCHCH2) (3); the facility with which the transformation occurs follows the sequence 1 > 2 > 3. The study of these processes under kinetic and thermodynamic control suggests that metal-based Lewis acid centers of composition TpMe2Ir(R)(R‘) (R and R‘ = alkyl groups) are of intermediate soft−hard nature.

Structural studies of the hydrido-bridged iridium gold complexes ‘IrHm{CH3C(CH2PPh2)3}{Au(PR3)}n’

The X-ray crystal structure of [{(triphos)H(3−x)Ir}(μ-H)x{Au(PR3)}][PF6] (triphos=CH3C(CH2PPh2)3, x=2) shows that the gold atom builds two almost equal Ir-H-Au bridges with the he ‘IrH3(triphos)’ building block. The Ir-H-Au bridging parameters are typical of three-center-two-electron interactions. The X-ray crystal structure of [{(triphos)H(3−y)Ir}(μ-H)y{Au(PR3)}2][PF6]2 shows that each gold atom builds two Ir(μ2-H)Au bridges with the three hydrides of the ‘IrH3(triphos)’ building block; one Ir(μ3-H)Au2 bridge is also present (y=3). The relative positions of the Ir, H, Au and P atoms show that typical three-center-two-electron interactions predominate in this compound, in which there is no direct Au-Au bonding. The neutron diffraction structure of [{(triphos)Ir}(μ-H)2{Au(PPh3)}3][PF6]2 confirms the earlier hypothesis that only two of the three Ir-Au edges are associated with a hydride with formation of Ir(μ2-H)Au bridges. The presence or absence of the latter ligand changes the Ir-Au distance only marginally, in contrast to the general trend in hydride clusters. It is shown that the formation of a ‘classical’ cluster in this set of compounds requires a quadrimetallic unit and the two additional electrons generated by loss of a proton from an Ir-H bond in the trication [{(triphos)Ir (μ2-H)3{Au(PR3)}3}3+.