The complexes OCBeCO3 and COBeCO3 have been isolated in a low-temperature neon matrix. The more stable isomer OCBeCO3 has a very high CO stretching mode of 2263 cm(-1) , which is blue-shifted by 122 cm(-1) with respect to free CO and 79 cm(-1) higher than in OCBeO. Bonding analysis of the complexes shows that OCBeO has a stronger OCBeY bond than OCBeCO3 because it encounters stronger π backdonation. The isomers COBeCO3 and COBeO exhibit red-shifted CO stretching modes with respect to free CO. The inverse change of CO stretching frequency in OCBeY and COBeY is explained with the reversed polarization of the σ and π bonds in CO.

We report the synthesis and spectroscopic characterization of the boron dicarbonyl complex [B(CO)2 ](-) . The bonding situation is analyzed and compared with the aluminum homologue [Al(CO)2 ](-) using state-of-the-art quantum chemical methods.

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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The novel neon complex NeBeCO3 has been prepared in a low-temperature neon matrix via codeposition of laser-evaporated beryllium atoms with O2 + CO/Ne. Doping by the heavier noble gas atoms argon, krypton and xenon yielded the associated adducts NgBeCO3 (Ng = Ar, Kr, Xe). The noble gas complexes have been identified via infrared spectroscopy. Quantum chemical calculations of NgBeCO3 and NgBeO (Ng = He, Ne, Ar, Kr, Xe) using ab initio methods and density functional theory show that the Ng-BeCO3 bonds are slightly longer and weaker than the Ng-BeO bonds. The energy decomposition analysis of the Ng-Be bonds suggests that the attractive interactions come mainly from the Ng → BeCO3 and Ng → BeO σ donation.

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Short interatomic distances below standard values for a single bond are usually identified with double or triple bonds. The synthesis and spectroscopic characterization of a molecule is reported where the distance between two beryllium atoms is shorter than a standard double bond but there is no bond. The cyclic diberyllium dioxide Be O molecule, which is coordinated by two noble gas atoms in Ng-Be O -Ng' (Ng, Ng'=Ne, Ar, Kr, Xe) was isolated and spectroscopically identified in low-temperature matrices. The complexes possess very short Be-Be distances, but the analysis of the electronic structure reveals that there is no chemical bond.

Through reaction of beryllium dimers with carbon monoxide, a carbonyl complex BeBeCO is formed in solid neon. Upon visible light excitation, the BeBeCO complex rearranges to a BeCOBe isomer, which further isomerizes to a low‐energy BeOBeC species under UV‐visible light excitation. These species are identified on the basis of infrared absorption spectroscopy with isotopic substitutions and quantum chemical studies. The BeOBeC molecule is characterized to be a multiple radical species having an electronic quintet ground state featuring an unusual quartet carbyne unit with three unpaired electrons on the carbon center. Bonding analysis indicates that the strong Pauli repulsion between carbon 2s lone pair electrons and the σ electrons of the BeOBe fragment significantly weakens the Be−C bonding and destabilizes the triplet state of the BeOBeC radical with a doublet carbyne unit. The three‐center π‐bonding of BeOBe is also found to play a role in stabilizing the quartet carbyne.