Norman Goldberg

A Combined Experimental and Theoretical Study of the Neutral, Cationic and Anionic Si3N Cluster Molecule

Collision experiments and high‐level ab initio calculations are used for the first characterization of the neutral, cationic, and anionic Si3N cluster molecules. The experimentally observed fragmentation processes are well described by calculated reaction energies of all dissociation channels. In addition, the geometries and harmonic frequencies of SinN (n=1–3) have been calculated for the cationic, anionic, and neutral species.

Generation and identification of neutral and cationic hydrogensilaisocyanid (“iminosilicon”, HNSi) by neutralization—reionization mass spectrometry and gaussian-1 ab initio molecular orbital calculations

Abstract Mass spectrometric studies demonstrate that electron bombardment of a mixture of N 2 /SiH 3 I results in the formation of HNSi + which can be neutralized to the long-sought-after HNSi. The experimental results are complemented by high level ab initio MO calculations using Poples gaussian-1 approach. Both theory and equipment point to the formation of HNSi + ( 2 ∑ + )/HNSi ( 1 ∑ + ) rather than the isomeric forms NSiH + ( 2 ∑ + )/NSiH ( 1 ∑ + ).

Bonding in the trihalides (X3–), mixed trihalides (X2Y–) and hydrogen bihalides (X2H–). The connection between hypervalent, electron-rich three-center, donor–acceptor and strong hydrogen bonding‡

The nature of the bonding in the trihalides (X3–), mixed trihalides (X2Y–), and hydrogen bihalides (X2H–) has been analysed by applying ideas from qualitative molecular orbital theory to computational results from density-functional calculations. A systematic, unified investigation showed that the bonding in all of these diverse anions can be understood in terms of the Rundle–Pimentel scheme for electron-rich three-center bonding. It also showed the equivalence of the donor–acceptor and hypervalent bonding views of these molecules. Less symmetrical trihalide ions were studied as well, e.g. the reasons why IICl– is favored over IClI– were explored. This site preference is considerably less pronounced in the I––IBr system. The donor–acceptor perspective (X– attack at the two possible sites of X–Y) was found to be useful. Similarly, formation of XHX– from X– and HX is strongly favored over formation of XXH–, and the energy difference between these two geometries increases with increasing electronegativity of X.

Gas-phase characterization of the neutral and cationic Si2O2 molecules. A combined experimental and ab initio study

Abstract Collision experiments are reported for the generation and characterization of the neutral and cationic Si2O2 molecule. In addition to the experimental characterization of Si2O2, high-level ab initio calculations (CCSD(T)/PVTZ/MP2/6-311G(df)) have been performed in order to support the experimental findings. The study reveals that the global minimum on both cationic and neutral surfaces corresponds to a bicyclic rhombohedric structure.

Combined experimental and theoretical study of the C-H bond strength and the gas phase acidity of triacetylene, C6H2, and the electron affinity of the C6H. radical

Abstract The thermochemistry of triacetylene, C 6 H 2 , the corresponding neutral triacetylide radical, C 6 H . , and the triacetylide anion, C 6 H − , has been evaluated by combining mass spectrometric means with high-level ab initio MO calculations at the CCSD(T) level. Experimentally, the ion/molecule bracketing method has been applied to determine the gas phase acidity (Δ G acid ) of C 6 H 2 as 347 ± 3 kcal mol . For this purpose, C 6 H − anions were reacted with various bases for which Δ G acid is known. The computations lead to a dissociation energy of 126.8 ± 1.6 kcal mol for a C-H bond of triacetylene and an electron affinity of 3.69 ± 0.05 eV for the triacetylide radical C 6 H . . Combining the calculated figures in terms of a thermochemical cycle leads to a theoretical prediction of Δ G acid (298 K) = 346.7 ± 2.8 kcal mol ; this is in excellent agreement with the experimental value. The implications of the present results for interstellar chemistry are discussed.

The gas phase nitrogen disulfide radical (SNS)

Abstract Collisional activation and neutralization—reionization mass spectrometric experiments provide evidence for the gas phase existence of the symmetrical nitrogen disulfide radical (S-N-S, 2 A 1 ) as well as the corresponding cation (S-N-S + , 1 Σ g + ). Thiadiazolothiadiazole has been employed as the precursor. Ab initio molecular orbital calculations at the QCISD(T)/6–311 + + G(3df, 2p)/ /MP2/6–311 + + G(d, p) + ZPE level lead to the following thermochemical data: heats of formation at 0 K (Δ H f,0 0 in kcal/mol): S-N-S: 66 ± 3, N-S-S: 85 ± 3, S-N-S + : 240 ± 3, N-S-S + : 311 ± 3 and HS-N-S: 59 ± 3; proton affinity PA(SNS) = 169 ± 3 kcal/mol and ionization energies IE a (SNS) = 7.5 ± 0.2 eV and IE a (HS-N-S) = 8.7 ± 0.2 eV.

Collisional cooling effects on the charge reversal and neutralization—reionization mass spectra of the negative cluster ion of sulfur dioxide (SO2) .−2

Abstract The charge reversal and neutralization—reionization mass spectra of the sulfur dioxide cluster anion (SO2)2.−2 are strongly affected by the ion-source pressure conditions and two possible origins for the collisional cooling effects are discussed.

The gas-phase generation and characterization of butatrienylidene H2CCCC : by neutralization-reionization mass spectrometry

Abstract Experiments are reported on the successful gas-phase generation of butatrienylidene H 2 CCCC: using the technique of neutralization—reionization mass spectrometry.

Charge reversal (CR) and neutralization reionization (−NR+) mass spectrometry of bicarbonate and bisulfite ions

Abstract Bicarbonate (HOCO−2) and bisulfite (HOSO−2) ions, generated by termolecular reactions of OH− with CO2 and SO2, respectively, are subjected to collision experiments, in the course of which corresponding radicals HOXO.2 (X = O on S) and cations HOXO+2 are generated and characterized by means of tandem mass spectrometry.