Density Functional and MP2 Studies of Germylene Insertion into C−H, Si−H, N−H, P−H, O−H, S−H, F−H, and Cl−H Bonds

Abstract

The potential energy surfaces for the insertion reactions of germylene into XH n molecules have been characterized in detail using ab initio molecular orbital theory and density functional theory. The model system Ge(CH3)2 + XH n (X = C, N, O, F, Si, P, S, and Cl; n = 1−4) has been chosen for the present study. All the interactions involve the initial formation of a donor−acceptor complex, followed by a high-energy transition state, and then an insertion product. The agreement between MP2 and B3LYP results indicates that the latter provides an adequate theoretical level for further investigations of molecular geometries, electronic structures, and kinetic features of the germylene reactions. The following conclusions emerge from this work: (i) the X−H insertion reactions of germylene occur in a concerted manner via a three-membered-ring transition state, and that the stereochemistry at the heteroatom X center is preserved; (ii) the stabilization energies of the germylene−XH n complexes increase in the order NH3 > H2O > PH3 > H2S ∼ HF > HCl ≫ SiH4 ∼ CH4; (iii) the order of reactivity for X−H bonds toward germylene insertion is Cl > F > S > O > P > N ≫ Si > C. In other words, the greater the atomic number of heteroatom (X) in a given row, the easier the insertion reaction of XH n hydrides and the larger the exothermicity. Moreover, the present study demonstrates that both electronic and steric effects play a major role in the course of insertion reactions of germylene into X−H bonds. This work also indicates that the chemical behavior of germylene should be more similar to that of silylene than to that of carbene species.

Destruction of formic acid by soft X-rays in star-forming regions

“…The same is true for O + , O + 2 and CH + 2 fragments. The opposite behavior occurs with HCO + and OH + which seem to be more efficiently produced by UV photons, as has been previously reported (Suto et al 1988;Su et al 2000;Schwel et al 2002).…”

“…The photodissociation of formic acid has been studied experimentally and theoretically in the vacuum ultraviolet (VUV) region (Su et al 2000;Tabayashi et al 1999;Schwell et al 2002). However the results cannot explain the ice/gas ratio, since about 20% of formic acid survives the UV radiation.…”

Silylenes and germylenes: The activation of H–H bond in hydrogen molecule

“…1). DFT, MP2, and CASSCF calculations (Table 1) have been demonstrated to give rather reasonable predictions on S-T gaps in singlet (S) and triplet (T) silylenes and germylenes [68,69,[88][89][90][109][110][111][112]. All those optimized minima and transition states were tested by frequency analysis, and the reported energies were corrected by the zero-point energies (ZPEs).…”

“…Similar to carbenes, most of silylenes and germylenes can function as Lewis acid or Lewis base, in which the vacant p orbital is responsible for electrophilic character (Lewis acid), while the non-bonding electron pair can act as the nucleophilic (Lewis base) attack region [77]. The activation reactions of some small inorganic and organic compounds by Lewis acid-base addition reactions, such as NO [91,98], NH 3 [103,110], CO [93], CO 2 [94,108], O 2 [91,102], Cl 2 [91] H 2 O [95,96,[103][104][105]110], C 2 H 4 [106,112], and C 2 H 2 [107] with silylenes and germylenes have been investigated experimentally. The insertion reactions of silylenes or germylenes into C-H, C-Cl, C-Br, and O-H bonds of small molecules, for example, CH 4 [110,111], CCl 4 [100,101], and CBr 4 [100] etc., have also been studied by the density functional theory (DFT).…”

Multiple Nanowire Channel Poly-Si TFTs with Defect Passivation

“…Due to the steps of strips, the spacers remained along the sidewalls of the strips after etching. It should be noted that the nano-scale dimension of the narrow-wire channels can be defined only by controlling the RIE time without any advanced lithography 6 , each dummy strip produces twin narrow wire channels, as well as the multiple channels can be designed with patterning several dummy strips (n strips x 2 wires/strip = 2n wires). Then, the solid phase crystallization (SPC) was performed at 600 o C for 24 hours to transform the a-Si into poly-Si.…”