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.

Using matrix-isolation infrared spectroscopy and DFT calculations, the reactions between 532 nm pulsed laser-ablated Ta and CO2 in argon gas ambient have been investigated. The major reaction products trapped in solid argon were found to be neutral OTaCO and O2Ta(CO)2 the anions OTaCO- and O2Ta(CO)2 -. The observed absorption bands of the reaction products were identified by isotopic substitution and reproduced well by DFT calculations of vibrational fundamentals. Upon irradiation with a pulsed laser at 355 nm, the neutral OTaCO and O2Ta(CO)2 were enhanced while O2Ta(CO)2 - and C2O4 - anions disappeared in the measured IR spectra. The potential energy surfaces of the interactions of Ta with CO2 and CO2 - were calculated, and the insertion of Ta into CO2 was suggested to proceed via electron transfer from Ta to CO2, in which CO2 - formation plays an important role in the activation of inert CO2 molecules.

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...

Reactions of titanium monoxides with methane have been investigated using matrix isolation infrared spectroscopy and theoretical calculations. Titanium derivatives of several simple oxyhydrocarbons have been prepared and identified. The titanium monoxide molecules prepared by laser evaporation of bulk TiO2 target reacted with methane to form the TiO(CH4) complex in solid argon, which was predicted to have C3v symmetry with the oxygen atom coordinated to one hydrogen atom of the methane molecule. The complex rearranged to the CH3Ti(O)H titano-acetaldehyde molecule upon visible (lambda > 500 nm) irradiation. The titano-acetaldehyde molecule sustained further photochemical rearrangement to the CH2Ti(H)OH titano-vinyl alcohol molecule, which was characterized to be a simple carbene complex involving agostic bonding. The CH2Ti(H)OH molecule reacted with a second methane to form the (CH3)2Ti(H)OH titano-isopropyl alcohol molecule spontaneously on annealing. The (CH3)2Ti(H)OH molecule also can be produced via UV photon-induced rearrangement of the CH3Ti(O)H(CH4) complex.

Reactions of laser-ablated Nb atoms with CO 2 give insertion products ONbCO and O 2 Nb(CO) 2 and the negative species O 2 Nb(CO) 2 -, which have been identified by matrix isolation FTIR method and DFT calculations. Two ONbCO structural products (I and II) were observed with infrared absorptions at 1902.6/960.1 and 1821.3/915.6 cm -1 , respectively. UV light irradiation destroyed the O 2 Nb(CO) 2anion completely, while the intensities of ONbCO(II) and O 2 NbCO were enhanced markedly. Sample annealing led to the obvious increase of ONbCO(II), while the ONbCO(I) can further combine with CO 2 to form O 2 Nb(CO) 2 .

The matrix isolation infrared spectroscopic and quantum chemical calculation results indicate that vanadium oxides, VO2 and VO4, coordinate noble gas atoms in forming noble gas complexes. The results showed that VO2 coordinates two Ar or Xe atoms and that VO4 coordinates one Ar or Xe atom in solid noble gas matrixes. Hence, the VO2 and VO4 molecules trapped in solid noble gas matrixes should be regarded as the VO2(Ng)2 and VO4(Ng) (Ng = Ar or Xe) complexes. The total V-Ng binding energies were predicted to be 12.8, 18.2, 5.0, and 7.3 kcal/mol, respectively, for the VO2(Ar)2, VO2(Xe)2, VO4(Ar), and VO4(Xe) complexes at the CCSD(T)//B3LYP level of theory.

The reactions of manganese and iron monoxides (MnO and FeO) with methane molecules have been investigated using matrix isolation infrared absorption spectroscopy. The metal monoxide molecules were prepared by laser ablation of MnO2 or Fe2O3 targets. The reaction products were identified on the basis of isotopic substitution experiments with 13CH4 and CD4, as well as density functional theoretical calculations. In solid argon, manganese and iron monoxides reacted with methane spontaneously on annealing to form the OMn(CH4) and OFe(CH4) complexes, which were predicted to have C 2 v symmetry with the metal atom coordinated to two hydrogen atoms of the methane molecule. The OMn(CH4) and OFe(CH4) complexes underwent photochemical rearrangement to the CH3MnOH and CH3FeOH molecules upon ultraviolet irradiation.