The Formal Oxidation States of Iridium Now Run from −III to +IX

Pyykkö, Pekka; Xu, Wenhua

doi:10.1002/anie.201410615

Cited by 27 publications

(23 citation statements)

References 19 publications

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“…[2][3][4][5] Recently,t he IrO 4 + cation was successfully formed in the gas phase,a nd was identified to contain the highest reported Ir IX oxidation state. [6,7] Forthe light elements in each row of the main group,t ransition metals,a nd actinides,the highest OS often equals the number of available valence electrons (e.g. + 3to+ 6f or Al-S,Sc-Cr,and Ac-U).However,i nl anthanides (Ln) the 4f orbitals are usually extremely contracted in radial distribution and considerably lower in energy because they penetrate the [Xe] core,t hus hardly participating in bonding.The chemistry of lanthanides is thus generally dominated by the low-valent + 3o r+ 2 oxidation state despite the fact that most lanthanides have available valence 4f electrons.…”

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Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides

Zhang

et al. 2016

Angew Chem Int Ed

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The chemistry of lanthanides (Ln = La-Lu) is dominated by the low-valent + 3or+ 2oxidation state because of the chemical inertness of the valence 4f electrons.T he highest knownoxidation state of the whole lanthanide series is + 4f or Ce,Pr, Nd, Tb,and Dy.W ereport the formation of the lanthanide oxide species PrO 4 and PrO 2 + complexes in the gas phase and in as olid noble-gas matrix. Combined infrared spectroscopic and advanced quantum chemistry studies show that these species have the unprecedented Pr V oxidation state, thus demonstrating that the pentavalent state is viable for lanthanide elements in as uitable coordination environment.Oxidation state (OS) has become ac entral concept of chemistry and astaple of chemistry textbooks.[1] Thequestion of just how high an OS of an element can be reached has long piqued chemists interest.[2] Thed iscovery of novel species with high OS helps to expand chemical understanding of the behavior of elements and their compounds.U ntil fairly recently,t he highest observed OS had been + 8, which occurs only in afew compounds including RuO 4 ,OsO 4 ,IrO 4 , and XeO 4 . [2][3][4][5] Recently,t he IrO 4 + cation was successfully formed in the gas phase,a nd was identified to contain the highest reported Ir IX oxidation state. [6,7] Forthe light elements in each row of the main group,t ransition metals,a nd actinides,the highest OS often equals the number of available valence electrons (e.g. + 3to+ 6f or Al-S,Sc-Cr,and Ac-U).However,i nl anthanides (Ln) the 4f orbitals are usually extremely contracted in radial distribution and considerably lower in energy because they penetrate the [Xe] core,t hus hardly participating in bonding.The chemistry of lanthanides is thus generally dominated by the low-valent + 3o r+ 2 oxidation state despite the fact that most lanthanides have available valence 4f electrons. [8][9][10] Besides the omnipresent oxidation state + 3, the higher oxidation state Ln IV is rather common for Ce,and is encountered in Pr, Nd, Tb,and Dy as well, [10] as these lanthanides have the lowest fourth ionization energies and also the lowest + 4/ + 3r eduction potentials. [11] Thec hemistry of pentavalent lanthanides has not been explored to date.[10] Aprevious study presumed the presence of pentavalent praseodymium in PrO 3 À without bonding analysis.[12] However,recent density functional theory (DFT) and ab initio multiconfigurational wavefunction theory (WFT) calculations show that the Pr center in the PrO 3 À anion is in oxidation state + 4r ather than the anticipated + 5.[13] Herein, we report ac ombined experimental and theoretical study on the lanthanide oxide species PrO 4 in solid noble-gas matrix as well as the PrO 2 + ion in the gas phase and in solid noble-gas matrix. Combined gas-phase infrared photodissociation spectroscopy,m atrix-isolation infrared absorption spectroscopy,a nd high-level quantum chemistry studies reveal that these species have the Pr V oxidation state. Thepraseodymium oxide cation species were generated in the gas phase by usi...

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Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides

Zhang

et al. 2016

Angew Chem Int Ed

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“…As discussed by us before,1 new, well‐established oxidation states in Chemistry are rarer than new elements. It therefore was interesting that the positive oxidation state of +IX was reached by Wang et al 2.…”

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“…Finally, we mention that the metal anions Pt −II and Au −I occur in the experimentally known binary solids Cs 2 Pt and CsAu, respectively, see ref. 1. The next step would be Cs 3 Ir.…”

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On the Extreme Oxidation States of Iridium

Pyykkö

2015

Chemistry A European J

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It has recently been suggested that the oxidation states of Ir run from the putative -III in the synthesized solid Na3 [Ir(CO)3 ] to the well-documented +IX in the species IrO4 (+) . Furthermore, [Ir(CO)3 ](3-) was identified as an 18-electron species. A closer DFT study now finds support for this picture: The orbitals spanned by the 6s,6p,5d orbitals of the iridium are all occupied. Although some have considerable ligand character, the deviations from 18 e leave the orbital symmetries unchanged. The isoelectronic systems from Os(-IV) to Au(-I) behave similarly, suggesting further possible species. To paraphrase Richard P. Feynmann "there is plenty of room at the bottom".

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“…[5] was the first to produce Ir IX by chemical, as opposed to nuclear, means.) Pyykkç and Xu [8] reviewed the formal oxidation states of iridium and noted, "…for many new exotic species, prediction precedes production." Herein, we pose the question: does oxidation state 10 exist?…”

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Oxidation State 10 Exists

Truhlar

2016

Angewandte Chemie

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In a recent paper, Wang et al. found an iridiumcontaining compound with a formal oxidation state of 9. [5] This is the highest oxidation state ever found in a stable compound. To learn if this is the highest chemical oxidation state possible, Kohn-Sham density functional theory was used to study various compounds, including PdO 4 2+ , PtO 4 2+ , PtO 3 F 2 2+ , PtO 4 OH + , PtO 5 , and PtO 4 SH + , in which the metal has an oxidation state of 10. It was found that PtO 4 2+ has a metastable state that is kinetically stable with a barrier height for decomposition of 31 kcal mol À1 and a calculated lifetime of 0.9 years. All other compounds studied would readily decompose to lower oxidation states.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under http://dx.

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The Formal Oxidation States of Iridium Now Run from −III to +IX

Cited by 27 publications

References 19 publications

Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides

Pentavalent Lanthanide Compounds: Formation and Characterization of Praseodymium(V) Oxides

On the Extreme Oxidation States of Iridium

Oxidation State 10 Exists

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