A hexagonal planar transition-metal complex.

Transition-metal complexes are widely used in the physical and biological sciences. They have essential roles in catalysis, synthesis, materials science, photophysics and bioinorganic chemistry. Our understanding of transition-metal complexes originates from Alfred Werner's realization that their three-dimensional shape influences their properties and reactivity1, and the intrinsic link between shape and electronic structure is now firmly underpinned by molecular-orbital theory2-5. Despite more than a century of advances in this field, the geometries of transition-metal complexes remain limited to a few well-understood examples. The archetypal geometries of six-coordinate transition metals are octahedral and trigonal prismatic, and although deviations from ideal bond angles and bond lengths are frequent6, alternative parent geometries are extremely rare7. The hexagonal planar coordination environment is known, but it is restricted to condensed metallic phases8, the hexagonal pores of coordination polymers9, or clusters that contain more than one transition metal in close proximity10,11. Such a geometry had been considered12,13 for [Ni(PtBu)6]; however, an analysis of the molecular orbitals suggested that this complex is best described as a 16-electron species with a trigonal planar geometry14. Here we report the isolation and structural characterization of a simple coordination complex in which six ligands form bonds with a central transition metal in a hexagonal planar arrangement. The structure contains a central palladium atom surrounded by three hydride and three magnesium-based ligands. This finding has the potential to introduce additional design principles for transition-metal complexes, with implications for several scientific fields.

Stabilisation of the [SiH6]2- Anion within a Supramolecular Assembly.

The hypercoordinate [SiH6]2- anion is not stable in solution. Here, we report the room temperature, solution stable molecular [SiH6]2- complex, [{KCa(NON)(OEt2)}2][SiH6] (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene)), where the [SiH6]2- anion is stabilised within a supramolecular assembly that mimics the solid-state environment of the anion in the lattice of K2SiH6. Solution-state reactivity of the complex towards carbon monoxide, benzaldehyde, azobenzene and acetonitrile is reported, yielding a range of reduction and C-C coupled products.

Anionic Magnesium and Calcium Hydrides: Transforming CO into Unsaturated Disilyl Ethers.

The synthesis, characterisation and reactivity of two isostructural anionic magnesium and calcium complexes is reported. By X-ray and neutron diffraction techniques, the anionic hydrides are shown to exist as dimers, held together by a range of interactions between the two anions and two bridging potassium cations. Unlike the vast proportion of previously reported dimeric group 2 hydrides, which have hydrides that bridge two group 2 centres, here the hydrides are shown to be "terminal", but stabilised by interactions with the potassium cations. Both anionic hydrides were found to insert and couple CO under mild reaction conditions to give the corresponding group 2 cis-ethenediolate complexes. These cis-ethenediolate complexes were found to undergo salt elimination reactions with silyl chlorides, allowing access to small unsaturated disilyl ethers with a high percentage of their mass originating from the C1 source CO.

The Ambiguous Origin of Thermochromism in Molecular Crystals of Dichalcogenides: Chalcogen Bonds versus Dynamic Se-Se/Te-Te Bonds.

We report thermochromism in crystals of diphenyl diselenide (dpdSe) and diphenyl ditelluride (dpdTe), which is at variance with the commonly known mechanisms of thermochromism in molecular crystals. Variable temperature neutron diffraction studies indicated no conformational change, tautomerization or phase transition between 100 K and 295 K. High-pressure crystallography studies indicated no associated piezochromism in dpdSe and dpdTe crystals. The evolution of the crystal structures and their electronic band structure with pressure and temperature reveal the contributions of intramolecular and intermolecular factors towards the origin of thermochromism-especially the intermolecular Se⋅⋅⋅Se and Te⋅⋅⋅Te chalcogen bonds and torsional modes of vibrations around the dynamic Se-Se and Te-Te bonds. Further, a co-crystal of dpdSe with iodine (dpdSe-I2 ) and an alloy crystal of dpdSe and dpdTe implied a predominantly intramolecular origin of the observed thermochromism associated with vibronic coupling.

Magnesium(I) Reduction of Aluminum(III) Hydride Complexes: Generation of Mixed Valence Aluminum (AlI /Al0 ) Hydride Cluster Compounds, [Al6 H8 (NR3 )2 {Mg(ß-diketiminate)}4 ].

Reduction of a range of amido- and aryloxy-aluminum dihydride complexes, e.g. [AlH2 (NR3 ){N(SiMe3 )2 }] (NR3 =NMe3 or N-methylpiperidine (NMP)), with ß-diketiminato dimagnesium(I) reagents, [{(Ar Nacnac)Mg}2 ] (Ar Nacnac=[HC(MeCNAr)2 ]- , Ar=mesityl (Mes) or 2,6-xylyl (Xyl)), have afforded deep red mixed valence aluminum hydride cluster compounds, [Al6 H8 (NR3 )2 {Mg(Ar Nacnac)}4 ], which have an average Al oxidation state of +0.66, the lowest for any well-defined aluminum hydride compound. In the solid-state, the clusters are shown to have distorted octahedral Al6 cores, having zero-valent Al axial sites and mono-valent AlH2 - equatorial units. Several novel by-products were isolated from the reactions that gave the clusters, including the Mg-Al bonded magnesio-aluminate complexes, [(Ar Nacnac)(Me3 N)Mg-Al(µ-H)3 [{Mg(Ar Nacnac)}2 (µ-H)]]. Computational analyses of one aluminum hydride cluster revealed its Al6 core to be electronically delocalized, and to possess one unoccupied, and six occupied, skeletal molecular orbitals.

Nickel and Palladium Complexes of a PP(O)P Pincer Ligand Based upon a peri-Substituted Acenaphthyl Scaffold and a Secondary Phosphine Oxide.

A PP(O)P pincer ligand based upon a peri-substituted acenaphthyl (Ace) scaffold and a secondary phosphine oxide, (5-Ph2P-Ace-6-)2P(O)H, was prepared and fully characterized including a neutron diffraction study. The reaction with [Ni(H2O)6]Cl2 and PdCl2 produced ionic metal(II) complexes [κ3-P,P',P''((5-Ph2P-Ace-6-)2P(OH))MCl]Cl, which upon addition of Et3N gave rise to zwitterionic metal(II) complexes κ3-P,P',P''((5-Ph2P-Ace-6-)2P(O))MCl (M = Ni, Pd). The reaction with Ni(COD)2 (COD = cyclooctadiene) provided the η3-cyclooctenyl Ni(II) complex κ3-P,P',P''((5-Ph2P-Ace-6-)2P(O))Ni(η3-C8H13). A detailed complementary bonding analysis of the P-H, P-O, and P-M interactions was carried out (M = Ni, Pd).

The Continuum Between Hexagonal Planar and Trigonal Planar Geometries.

New heterometallic hydride complexes that involve the addition of {Mg-H} and {Zn-H} bonds to group 10 transition metals (Pd, Pt) are reported. The side-on coordination of a single {Mg-H} to Pd forms a well-defined σ-complex. In contrast, addition of three {Mg-H} or {Zn-H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X-ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.

Evaluating the relationship between clinical and demographic characteristics of insulin-using people with diabetes and their health outcomes: a cluster analysis application.

BACKGROUND: The aim of this study was to determine how clusters or subgroups of insulin-treated people with diabetes, based upon healthcare resource utilization, select social demographic and clinical characteristics, and diabetes management parameters, are related to health outcomes including acute care visits and hospital admissions. METHODS: This was a non-experimental, retrospective cluster analysis. We utilized Aetna administrative claims data to identify insulin-using people with diabetes with service dates from 01 January 2015 to 30 June 2018. The study included adults over the age of 18 years who had a diagnosis of type 1 (T1DM) or type 2 diabetes mellitus (T2DM) on insulin therapy and had Aetna medical and pharmacy coverage for at least 18 months (6 months prior and 12 months after their index date, defined as either their first insulin prescription fill date or their earliest date allowing for 6 months' prior coverage). We used K-means clustering methods to identify relevant subgroups of people with diabetes based on 13 primary outcome variables. RESULTS: A total of 100,650 insulin-using people with diabetes were identified in the Aetna administrative claims database and met study criteria, including 11,826 (11.7%) with T1DM and 88,824 (88.3%) with T2DM. Of these 79,053 (78.5%) people were existing insulin users. Seven distinct clusters were identified with different characteristics and potential risks of diabetes complications. Overall, clusters were significantly associated with differences in healthcare utilization (emergency room visits, inpatient admissions, and total inpatient days) after multivariable adjustment. CONCLUSIONS: This analysis of healthcare claims data using clustering methodologies identified meaningful subgroups of patients with diabetes using insulin. The subgroups differed in comorbidity burden, healthcare utilization, and demographic factors which could be used to identify higher risk patients and/or guide the management and treatment of diabetes.

Effect of Probiotic Use on Antibiotic Administration Among Care Home Residents: A Randomized Clinical Trial.

Importance: Probiotics are frequently used by residents in care homes (residential homes or nursing homes that provide residents with 24-hour support for personal care or nursing care), although the evidence on whether probiotics prevent infections and reduce antibiotic use in these settings is limited. Objective: To determine whether a daily oral probiotic combination of Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp lactis BB-12 compared with placebo reduces antibiotic administration in care home residents. Design, Setting, and Participants: Placebo-controlled randomized clinical trial of 310 care home residents, aged 65 years and older, recruited from 23 care homes in the United Kingdom between December 2016 and May 2018, with last follow-up on October 31, 2018. Interventions: Study participants were randomized to receive a daily capsule containing a probiotic combination of Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp lactis BB-12 (total cell count per capsule, 1.3 × 1010 to 1.6 × 1010) (n = 155), or daily matched placebo (n = 155), for up to 1 year. Main Outcomes and Measures: The primary outcome was cumulative antibiotic administration days for all-cause infections measured from randomization for up to 1 year. Results: Among 310 randomized care home residents (mean age, 85.3 years; 66.8% women), 195 (62.9%) remained alive and completed the trial. Participant diary data (daily data including study product use, antibiotic administration, and signs of infection) were available for 98.7% randomized to the probiotic group and 97.4% randomized to placebo. Care home residents randomized to the probiotic group had a mean of 12.9 cumulative systemic antibiotic administration days (95% CI, 0 to 18.05), and residents randomized to placebo had a mean of 12.0 days (95% CI, 0 to 16.95) (absolute difference, 0.9 days [95% CI, -3.25 to 5.05]; adjusted incidence rate ratio, 1.13 [95% CI, 0.79 to 1.63]; P = .50). A total of 120 care home residents experienced 283 adverse events (150 adverse events in the probiotic group and 133 in the placebo group). Hospitalizations accounted for 94 of the events in probiotic group and 78 events in the placebo group, and deaths accounted for 33 of the events in the probiotic group and 32 of the events in the placebo group. Conclusions and Relevance: Among care home residents in the United Kingdom, a daily dose of a probiotic combination of Lactobacillus rhamnosus GG and Bifidobacterium animalis subsp lactis BB-12 did not significantly reduce antibiotic administration for all-cause infections. These findings do not support the use of probiotics in this setting. Trial Registration: ISRCTN Identifier:16392920.

Molecular Thorium Trihydrido Clusters Stabilized by Cyclopentadienyl Ligands.

Hydrogenolysis of alkyl-substituted cyclopentadienyl (CpR ) ligated thorium tribenzyl complexes [(CpR )Th(p-CH2 -C6 H4 -Me)3 ] (1-6) afforded the first examples of molecular thorium trihydrido complexes [(CpR )Th(µ-H)3 ]n (CpR =C5 H2 (t Bu)3 or C5 H2 (SiMe3 )3 , n=5; C5 Me4 SiMe3 , n=6; C5 Me5 , n=7; C5 Me4 H, n=8; 7-10 and 12) and [(Cp# )12 Th13 H40 ] (Cp# =C5 H4 SiMe3 ; 13). The nuclearity of the metal hydride clusters depends on the steric profile of the cyclopentadienyl ligands. The hydrogenolysis intermediate, tetra-nuclear octahydrido thorium dibenzylidene complex [(Cpttt )Th(µ-H)2 ]4 (µ-p-CH-C6 H4 -Me)2 (Cpttt =C5 H2 (t Bu)3 ) (11) was also isolated. All of the complexes were characterized by NMR spectroscopy and single-crystal X-ray analysis. Hydride positions in [(CpMe4 )Th(µ-H)3 ]8 (CpMe4 =C5 Me4 H) were further precisely confirmed by single-crystal neutron diffraction. DFT calculations strengthen the experimental assignment of the hydride positions in the complexes 7 to 12.

Measurement of Electric Fields Experienced by Urea Guest Molecules in the 18-Crown-6/Urea (1:5) Host-Guest Complex: An Experimental Reference Point for Electric-Field-Assisted Catalysis.

High-resolution synchrotron and neutron single-crystal diffraction data of 18-crown-6/(pentakis)urea measured at 30 K are combined, with the aim of better appreciating the electrostatics associated with intermolecular interactions in condensed matter. With two 18-crown-6 molecules and five different urea molecules in the crystal, this represents the most ambitious combined X-ray/synchrotron and neutron experimental charge density analysis to date on a cocrystal or host-guest system incorporating such a large number of unique molecules. The dipole moments of the five urea guest molecules in the crystal are enhanced considerably compared to values determined for isolated molecules, and 2D maps of the electrostatic potential and electric field show clearly how the urea molecules are oriented with dipole moments aligned along the electric field exerted by their molecular neighbors. Experimental electric fields in the range of 10-19 GV m-1, obtained for the five different urea environments, corroborate independent measurements of electric fields in the active sites of enzymes and provide an important experimental reference point for recent discussions focused on electric-field-assisted catalysis.

Proximity Enforced Agostic Interactions Involving Closed-Shell Coinage Metal Ions.

A proximity enforcing diarylsilane ligand is reported, which gives rise to unusual Si-H···M interactions with the d10 metal ions Cu+ and Ag+ upon complexation. These interactions are studied in detail both experimentally and computationally and can be classified to be weakly agostic in nature for the Si-H···Cu interaction. The Si-H···Ag interaction has more signatures of an electrostatic contact.

Correction to: Effects of workload, work complexity, and repeated alerts on alert fatigue in a clinical decision support system.

Following publication of the original article [1], the authors reported that the article erroneously stated that Dr. Ancker was affiliated with the Tehran University of Medical Sciences. Dr. Ancker is not affiliated with that institution.

Investigation of an Unusual Crystal Habit of Hydrochlorothiazide Reveals Large Polar Enantiopure Domains and a Possible Crystal Nucleation Mechanism.

The observation of an unusual crystal habit in the common diuretic drug hydrochlorothiazide (HCT), and identification of its subtle conformational chirality, has stimulated a detailed investigation of its crystalline forms. Enantiomeric conformers of HCT resolve into an unusual structure of conjoined enantiomorphic twin crystals comprising enantiopure domains of opposite chirality. The purity of the domains and the chiral molecular conformation are confirmed by spatially revolved synchrotron micro-XRD experiments and neutron diffraction, respectively. Macroscopic inversion twin symmetry observed between the crystal wings suggests a pseudoracemic structure that is not a solid solution or a layered crystal structure, but an unusual structural variant of conglomerates and racemic twins. Computed interaction energies for molecular pairs in the racemic and enantiopure polymorphs of HCT, and the observation of large opposing unit-cell dipole moments for the enantiopure domains in these twin crystals, suggest a plausible crystal nucleation mechanism for this unusual crystal habit.

Redox-Dependent Metal-Metal Bonding in Trinuclear Metal Chains: Probing the Transition from Covalent Bonding to Exchange Coupling.

The synthesis and physical properties of two new cationic tri-metallic chains, [(PEt3 )3 RuCl3 M'Cl3 Ru(PEt3 )3 ]1+ , M'=Rh and Ir are reported. These are isostructural with a previously reported 17-electron all-ruthenium analogue, but replacing a d5 RuIII ion in the central position with d6 RhIII /IrIII has a significant impact on the nature of the metal-metal interactions. All three materials have been characterized electrochemically at the 18-, 17- and 16-electron levels. X-ray crystallography and spectroelectrochemistry, complemented by electronic structure analysis at the DFT and CASPT2 levels, indicate that whilst the presence of a RuIII ion in the center of the chain allows multi-center covalent bonding to develop, a closed-shell RhIII /IrIII ion pushes the system towards the exchange-coupled limit, where the outer Ru centers are only weakly interacting. This family of three isostructural compounds reveals how changes in metal composition can have subtle effects on physical properties of systems that lie close to the localized/delocalized borderline.

Synthesis and X-Ray Crystallographic Characterisation of Frustum-Shaped Ligated [Cu18 H16 (DPPE)6 ]2+ and [Cu16 H14 (DPPA)6 ]2+ Nanoclusters and Studies on Their H2 Evolution Reactions.

We report new structural motifs for Cu nanoclusters that conceptually represent seed crystals for large face-centred cubic (FCC) crystal growth. Kinetically controlled syntheses, high resolution mass spectrometry experiments for determination of the dication formulae and crystallographic characterisation were carried out for [Cu18 H16 (DPPE)6 ][BF4 ][Cl] (DPPE=bis(diphenylphosphino)ethane) and [Cu16 H14 (DPPA)6 ][(BF4 )2 ] (DPPA=bis(diphenylphosphino)amine) polyhydrido nanoclusters, which feature the unprecedented bifrustum and frustum metal-core architecture in metal nanoclusters. The Cu18 nanocluster contains two Cu9 frustum cupolae and the Cu16 nanocluster has one Cu9 frustum cupola and a Cu7 distorted hexagonal-shape base. Gas-phase experiments revealed that both Cu18 H16 and Cu16 H14 cores can spontaneously release H2 upon removal of one bisphosphine capping ligand.

Pharmacogenetic testing among patients with mood and anxiety disorders is associated with decreased utilization and cost: A propensity-score matched study.

BACKGROUND: Naturalistic and small randomized trials have suggested that pharmacogenetic testing may improve treatment outcomes in depression, but its cost-effectiveness is not known. There is growing enthusiasm for personalized medicine, relying on genetic variation as a contributor to heterogeneity of treatment effects. We sought to examine the relationship between a commercial pharmacogenetic test for psychotropic medications and 6-month cost of care and utilization in a large commercial health plan. METHODS: We performed a propensity-score matched case-control analysis of longitudinal health claims data from a large US insurer. Individuals with a mood or anxiety disorder diagnosis (N = 817) who received genetic testing for pharmacokinetic and pharmacodynamic variation were matched to 2,745 individuals who did not receive such testing. Outcomes included number of outpatient visits, inpatient hospitalizations, emergency room visits, and prescriptions, as well as associated costs over 6 months. RESULTS: On average, individuals who underwent testing experienced 40% fewer all-cause emergency room visits (mean difference 0.13 visits; P < 0.0001) and 58% fewer inpatient all-cause hospitalizations (mean difference 0.10 visits; P < 0.0001) than individuals in the control group. The two groups did not differ significantly in number of psychotropic medications prescribed or mood-disorder related hospitalizations. Overall 6-month costs were estimated to be $1,948 (SE 611) lower in the tested group. CONCLUSIONS: Pharmacogenetic testing represents a promising strategy to reduce costs and utilization among patients with mood and anxiety disorders.

Circular dichroism studies of low molecular weight hydrogelators: The use of SRCD and addressing practical issues.

Circular dichroism (CD) spectroscopy has been used extensively for the investigation of the conformation and configuration of chiral molecules, but its use for evaluating the mode of self-assembly in soft materials has been limited. Herein, we report a protocol for the study of such materials by electronic CD spectroscopy using commercial/benchtop instruments and synchrotron radiation (SR) using the B23 beamline available at Diamond Light Source. The use of the B23 beamtime for SRCD was advantageous because of the unique enhanced spatial resolution achieved because of its highly collimated and small beamlight cross section (ca. 250 µm) and higher photon flux in the far UV region (175-250 nm) enhancing the signal-to-noise ratio relative to benchtop CD instruments. A set of low molecular weight (LMW) hydrogelators, comprising two Fmoc-protected enantiomeric monosaccharides and one Fmoc dipeptide (Fmoc-FF), were studied. The research focused on the optimization of sample preparation and handling, which then enabled the characterization of sample conformational homogeneity and thermal stability. CD spectroscopy, in combination with other spectroscopic techniques and microscopy, will allow a better insight into the self-assembly of chiral building blocks into higher order structural architectures.

Effect of a Home-Based Wearable Continuous ECG Monitoring Patch on Detection of Undiagnosed Atrial Fibrillation: The mSToPS Randomized Clinical Trial.

Importance: Opportunistic screening for atrial fibrillation (AF) is recommended, and improved methods of early identification could allow for the initiation of appropriate therapies to prevent the adverse health outcomes associated with AF. Objective: To determine the effect of a self-applied wearable electrocardiogram (ECG) patch in detecting AF and the clinical consequences associated with such a detection strategy. Design, Setting, and Participants: A direct-to-participant randomized clinical trial and prospective matched observational cohort study were conducted among members of a large national health plan. Recruitment began November 17, 2015, and was completed on October 4, 2016, and 1-year claims-based follow-up concluded in January 2018. For the clinical trial, 2659 individuals were randomized to active home-based monitoring to start immediately or delayed by 4 months. For the observational study, 2 deidentified age-, sex- and CHA2DS2-VASc-matched controls were selected for each actively monitored individual. Interventions: The actively monitored cohort wore a self-applied continuous ECG monitoring patch at home during routine activities for up to 4 weeks, initiated either immediately after enrolling (n = 1364) or delayed for 4 months after enrollment (n = 1291). Main Outcomes and Measures: The primary end point was the incidence of a new diagnosis of AF at 4 months among those randomized to immediate monitoring vs delayed monitoring. A secondary end point was new AF diagnosis at 1 year in the combined actively monitored groups vs matched observational controls. Other outcomes included new prescriptions for anticoagulants and health care utilization (outpatient cardiology visits, primary care visits, or AF-related emergency department visits and hospitalizations) at 1 year. Results: The randomized groups included 2659 participants (mean [SD] age, 72.4 [7.3] years; 38.6% women), of whom 1738 (65.4%) completed active monitoring. The observational study comprised 5214 (mean [SD] age, 73.7 [7.0] years; 40.5% women; median CHA2DS2-VASc score, 3.0), including 1738 actively monitored individuals from the randomized trial and 3476 matched controls. In the randomized study, new AF was identified by 4 months in 3.9% (53/1366) of the immediate group vs 0.9% (12/1293) in the delayed group (absolute difference, 3.0% [95% CI, 1.8%-4.1%]). At 1 year, AF was newly diagnosed in 109 monitored (6.7 per 100 person-years) and 81 unmonitored (2.6 per 100 person-years; difference, 4.1 [95% CI, 3.9-4.2]) individuals. Active monitoring was associated with increased initiation of anticoagulants (5.7 vs 3.7 per 100 person-years; difference, 2.0 [95% CI, 1.9-2.2]), outpatient cardiology visits (33.5 vs 26.0 per 100 person-years; difference, 7.5 [95% CI, 7.2-7.9), and primary care visits (83.5 vs 82.6 per 100 person-years; difference, 0.9 [95% CI, 0.4-1.5]). There was no difference in AF-related emergency department visits and hospitalizations (1.3 vs 1.4 per 100 person-years; difference, 0.1 [95% CI, -0.1 to 0]). Conclusions and Relevance: Among individuals at high risk for AF, immediate monitoring with a home-based wearable ECG sensor patch, compared with delayed monitoring, resulted in a higher rate of AF diagnosis after 4 months. Monitored individuals, compared with nonmonitored controls, had higher rates of AF diagnosis, greater initiation of anticoagulants, but also increased health care resource utilization at 1 year. Trial Registration: ClinicalTrials.gov Identifier: NCT02506244.

A Gallium Hydride as an Oxidizing Agent: Direct Synthesis of IrV Complexes via Ga-H Bond Activation.

Reactions of the ß-diketiminate-stabilized gallium dihydride (Nacnac)Dipp GaH2 with chelating IrI bis(phosphine) precursors under an H2 atmosphere are shown to provide a simple route to IrV complexes stabilized by strongly σ-donating hydrides and the carbene-like (Nacnac)Dipp Ga donor. Characterization of these systems as seven-coordinate IrV tetrahydride species is supported by single crystal X-ray and neutron diffraction, and by T1 NMR measurements. By contrast related systems featuring more sterically demanding (non-chelating) ancillary ligands are better described in terms of a bis(hydride) dihydrogen [L3 Ir(H)2 (H2 )]+ formulation and a formal IrIII oxidation state.