Isomers of Ge2N2: Production and infrared absorption of GeNNGe in solid N2

Beryllium Atom Mediated Dinitrogen Activation via Coupling with Carbon Monoxide

The reactions of laser-ablated beryllium atoms with dinitrogen and carbon monoxide mixtures form the end-on bonded NNBeCO and side-on bonded (η2 -N2 )BeCO isomers in solid argon, which are predicted by quantum chemical calculations to be almost isoenergetic. The end-on bonded complex has a triplet ground state while the side-on bonded isomer has a singlet electronic ground state. The complexes rearrange to the energetically lowest lying NBeNCO isomer upon visible light excitation, which is characterized to be an isocyanate complex of a nitrene derivative with a triplet electronic ground state. A bonding analysis using a charge- and energy decomposition procedure reveals that the electronic reference state of Be in the NNBeCO isomers has an 2s0 2p2 excited configuration and that the metal-ligand bonds can be described in terms of N2 →Be←CO σ donation and concomitant N2 ←Be→CO π backdonation. The results demonstrate that the activation of N2 with the N-N bond being completely cleaved can be achieved via coupling with carbon monoxide mediated by a main group atom.

Side-On Bonded Beryllium Dinitrogen Complexes

The preparation and spectroscopic identification of the complexes NNBe(η2 -N2 ) and (NN)2 Be(η2 -N2 ) and the energetically higher lying isomers Be(NN)2 and Be(NN)3 are reported. NNBe(η2 -N2 ) and (NN)2 Be(η2 -N2 ) are the first examples of covalently side-on bonded N2 adducts of a main-group element. The analysis of the electronic structure using modern methods of quantum chemistry suggests that NNBe(η2 -N2 ) and (NN)2 Be(η2 -N2 ) should be classified as π complexes rather than metalladiazirines.

Infrared absorption of GeNNO isolated in solid Ar

Codeposition of thermally generated atomic germanium vapor and nitrous oxide (N(2)O) in Ar onto a substrate at 11 K produced infrared absorption lines in several sets. The most prominent comprises intense lines at 1443.7, 1102.4, and 784.0 cm(-1) that become diminished upon irradiation with UV or visible light. These lines are attributed to nu(1) (NO stretching), nu(2) (NN+GeN stretching), and nu(3) (NNO bending+NN stretching) modes of singlet GeNNO. Two additional weak features at 1238.1 and 2859.2 cm(-1) are assigned as nu(3)+nu(4) and 2nu(1) of GeNNO, respectively. Weak doublet features at 1259.3/1255.5 and 1488.9/1486.4 cm(-1) are tentatively assigned to nu(2) of triplet GeONN and nu(1) of singlet cyc-Ge-eta(2) [NN(O)], respectively. Quantum-chemical calculations on the Ge+N(2)O system with density-functional theory (B3LYP /aug-cc-pVTZ) predict five stable structures: GeNNO (singlet and triplet), singlet cyc-Ge-eta(2) [NN(O)], triplet cyc-Ge-eta(2) (NNO), GeONN (singlet and triplet), and singlet GeNON. Vibrational wavenumbers, relative IR intensities, and (15)N-isotopic ratios for observed species are consistent with those computed. Irradiation of singlet GeNNO with lambda=248 or 193 nm or lambda>525 nm yields GeO.

Intrinsic Dinitrogen Activation at Bare Metal Atoms

There is ongoing interest in metal complexes which bind dinitrogen and facilitate either its reduction or oxidation under mild conditions. In nature, the enzyme nitrogenase catalyzes this process, and dinitrogen fixation occurs under mild and ambient conditions at a metal-sulfur cluster in the center of the MoFe protein, but the mechanism of this process remains largely unknown. In the last few years, new important discoveries have been made in this field. In this review are discussed recent findings on the interaction of N(2) with metal atoms and metal-atom dimers from all groups of the periodic table as provided by gas-phase as well as matrix-isolation experiments. Intrinsic dinitrogen activation at such bare metal atoms is then related to corresponding processes at complexes, clusters, and surfaces.

Isomers of GeNO and Ge(NO)2: Production and infrared absorption of GeNO and ONGeNO in solid Ar

Crystalline germanium was ablated with light at 532 nm from a frequency-doubled neodymium: yttrium aluminum garnet laser, and the resultant plume reacted with NO before deposition onto a substrate at 13 K. Lines in group A at 1543.8 and 3059.7 cm(-1) that become enhanced at the initial stage of irradiation at 308 or 193 nm and also after annealing are attributed to nu1 and 2nu1 of GeNO. Lines in group B at 1645.5 and 1482.8 cm(-1) that become diminished after further irradiation of the matrix at 308 or 193 nm but become enhanced after annealing are attributed to symmetric NO stretch (nu1) and antisymmetric NO stretch (nu7) of ONGeNO. The assignments were derived based on wave numbers and isotopic ratios observed in the experiments with 15N- and 18O-isotopic substitutions and predicted with quantum-chemical calculations. Quantum-chemical calculations with density-functional theories (B3LYP and BLYP/aug-cc-pVTZ) predict four stable isomers of GeNO, six isomers of Ge2NO, and four isomers of Ge(NO)2, with linear GeNO, cyc-GeNGeO, and cyc-GeONNO having the least energies, respectively. The formation mechanisms of GeNO and ONGeNO are discussed. In addition, a weak line at 1417.0 cm(-1) and two additional lines associated with minor matrix sites at 1423.0 and 1420.3 cm(-1) are assigned to GeNO-.

Isomers of HSCO: IR absorption spectra of t-HSCO in solid Ar

Irradiation of an Ar matrix sample containing H2S and CO (or OCS) with an ArF excimer laser at 193 nm yields trans-HSCO (denoted t-HSCO). New lines at 1823.3, 931.6, and 553.3 cm(-1) appear after photolysis and their intensity enhances after annealing; secondary photolysis at 248 nm diminishes these lines and produces OCS and CO. These lines are assigned to C-O stretching, HSC-bending, and C-S stretching modes of t-HSCO, respectively, based on results of 13C-isotopic experiments and theoretical calculations. Theoretical calculations using density-functional theories (B3LYP and PW91PW91) predict four stable isomers of HSCO: t-HSCO, c-HSCO, HC(O)S, and c-HOCS, listed in increasing order of energy. According to calculations with B3LYP/aug-cc-pVTZ, t-HSCO is planar, with bond lengths of 1.34 A (H-S), 1.81 A (S-C), and 1.17 A (C-O), and angles angle HSC congruent with 93.4 degrees and angle SCO congruent with 128.3 degrees; it is more stable than c-HSCO and HC(O)S by approximately 9 kJ mol(-1) and more stable than c-HOCS by approximately 65 kJ mol(-1). Calculated vibrational wave numbers, IR intensities, and 13C-isotopic shifts for t-HSCO fit satisfactorily with experimental results. This new spectral identification of t-HSCO provides information for future investigations of its roles in atmospheric chemistry.