Theoretical study of the stability of species ABH3(ALi…Ne) (original) (raw)
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The boranes B3H7 and B6H14. A theoretical investigation
Chemical Physics Letters, 1988
Results of SCF and CPF calculations are reported for B,H, and its dimer BbH,,. They were performed to determine structure and relative energies. As a check for the methods of calculation employed we report large-scale treatments of BH, and B,H,. For BIHl we confirm previous treatments showing the existence of at least three isomers separated by only a few kJ/mol. Dimerization of B,H7 is computed to be exothermic by 74.3 kJ/mol. The most stable isomer of B,H,, is tris-diborane but various other structures are only 10 to 30 kJ/mol higher in energy, indicating non-rigidity on the time scale of NMR measurements, These results allow for a rationalization of experiments.
Stability and bonding in the borane-H 2 complexes
International Journal of Quantum Chemistry, 2012
The ability of substituted boranes, X n BH 3Àn , to form stable complexes with the hydrogen molecule is analyzed by making use of computational chemistry and local reactivity parameters. In these complexes, the hydrogen molecule acts as a Lewis base while the borane moiety is the Lewis acid. Electronegative groups (X ¼ CF 3 , F, OH) are selected to increase the acidity of the borane and it is found that the energetic stability of the complexes is only increased for the trifluoromethyl-substituted Lewis acids, at the MP2/6-311þþg(3df, 3pd) level. It is also found that the BLYP density functional underestimates the adduct stability of these species. On the other hand, fluoroboranes and hydroxyboranes do not form donor-acceptor adducts with the hydrogen molecule; instead, we find weakly bounded van der Waals complexes. Additional features on the intrinsic reactivity of boranes are analyzed with the molecular electrostatic potential and the acceptor Fukui function. The nature of the interaction among the boranes and the hydrogen molecule is explored by using the topological analysis of the electron density through the Bader's Atoms-in-Molecules theory.
A full configuration interaction study of the low-lying states of the BH molecule
Molecular Physics, 1997
A full con® guration interaction study on the BH molecule is presented. The potential energy curves of 20 di erent electronic states have been calculated correlating the four valence electrons. On the two most important states, i.e. the X 1 R + and A 1 P states, a complete study has been performed. This includes the e ect of core electron correlation, estimated via truncated con® guration interaction techniques. The dissociation energy of the molecule in the two states and the height of the predissociative barrier in the A 1 P state have been determined with basis sets of increasing quality.
A full con� guration interaction study of the low-lying states of the BH molecule
1997
A full con® guration interaction study on the BH molecule is presented. The potential energy curves of 20 di erent electronic states have been calculated correlating the four valence electrons. On the two most important states, i.e. the X 1 R + and A 1 P states, a complete study has been performed. This includes the e ect of core electron correlation, estimated via truncated con® guration interaction techniques. The dissociation energy of the molecule in the two states and the height of the predissociative barrier in the A 1 P state have been determined with basis sets of increasing quality.
Comparison of μ2-scaled Hückel theory and Hartree–Fock theory of boranes and carboranes
The Journal of Chemical Physics, 1994
The h-scaled Hiickel method is used to calculate the electronic energy surfaces of the four boranes B,Hz-(12 =8-l 1) and the carborane C,BsH:, . These electronic energy surfaces and their minimum energy geometries are directly compared to both the single crystal x-ray determined structures and to Hartree-Fock optimized geometries. Bond distances differ on the average by 0.04 A between alternate methods. It is shown that h-scaled Hiickel results may be directly interpreted by analysis of the highest occupied and lowest unoccupied molecular orbitals. Also studied by the h-scaled Hiickel and Hartree-Fock methods are the isomerization pathways of BsHi-, B,,H:;, and C,BsHfR . Reaction barriers and transition state geometries found by the two different calculational methods are in fair agreement with each other and known literature values. Using the h-scaled Hiickel method one can readily deduce that the BsHi-and B,,H:; isomerizations are Woodward-Hoffmann allowed reactions. In the case of B,Hi-this allowed mechanism is contrasted to an alternate Woodward-Hoffmann forbidden pathway. Hartree-Fock calculations on the C,BsHT, confirm earlier h-scaled Hiickel based findings, that a second less stable isomer of C,B,H:, exists which, in contradiction to Wade's rules of electron deficient clusters, has a pair of open square faces in the cluster.
Chemical Physics Letters, 1998
Static and frequency-dependent polarizabilities and first and second hyperpolarizabilities have been calculated for BH Ž . using full configuration interaction FCI and the hierarchy of coupled cluster models CCS, CC2 and CCSD. A systematic basis set investigation has been performed and has been used to estimate basis set limit results. The FCI results are used to calibrate the accuracy of the coupled cluster model hierarchy. No systematic improvements are found in CC2 relative to CCS. The CCSD model appears to be robust and represents a significant improvement relative to CCS and CC2. The CCSD results are in close agreement with the FCI results for a and g , while for b a similar accuracy requires considerations of a higher level in the coupled cluster hierarchy. q
Non-Born–Oppenheimer calculations of the BH molecule
The Journal of Chemical Physics, 2009
Variational calculations employing explicitly correlated Gaussian basis functions have been performed for the ground state of the boron monohydride molecule ͑BH͒ and for the boron atom ͑B͒. Up to 2000 Gaussians were used for each system. The calculations did not assume the Born-Oppenheimer ͑BO͒ approximation. In the optimization of the wave function, we employed the analytical energy gradient with respect to the Gaussian exponential parameters. In addition to the total nonrelativistic energies, we computed scalar relativistic corrections ͑mass-velocity and Darwin͒. With those added to the total energies, we estimated the dissociation energy of BH. The non-BO wave functions were also used to compute some expectation values involving operators dependent on the interparticle distances.
Studying Complex Interaction of B2H4 with HOR(R = H, CH3) and Nhn(CH3)3-N (N = 0-3) Molecules
International Journal of Medical Nano Research
Borane complexes are extensively studied and have even been the subject of Nobel Prize by Brown [1]. Many scientific data exist that have shown that boron is an essential microelement in animal cells. With the knowledge that borate linkages function in cell-to-cell adhesion, it has been hypothesised that boronates target structural glycoproteins located along the cytoskeletonplasma membrane-cell wall assembly. On the other hand, boron-carrier molecules can be used as a therapeutic mean to fight cancers [2,3]. Also, they have been the subject of proton affinity experiments in chemical ionization mass spectrometry. Among non-covalent interactions which have been known in boron chemistry, both dihydrogen and hydrogen bonding patterns are particularly significant [4-9]. B 2 H 4 , designated as diborane (4), is probably the best known electron-deficient analogue of ethylene [10-13]. B 2 H 4 bears 10 valence electrons for chemical bonding. There are two standard two electron terminal B-H bonds, thus accounting for a total of four electrons. This leaves a total of six electrons to share between the two bridging H and the two B atoms. Consequently, there are two 3c-2e curved 'banana' B-H-B bridging bonds. According to the above illustrations, B 2 H 4 has two types of hydrogen atoms: terminal (H t-B) and bridging (B-H b-B) ones, which differ in nature and characteristics. The bridging hydrogens of B 2 H 4 participate in the electron deficient 'three-center,
Inorganic Chemistry
Density functional theory calculations were carried out to optimize all the molecules without any symmetry constraints using the meta-GGA M06 exchange correlational functional in conjunction with Def2-TZVP basis set for main group elements 1,2 and Stuttgart-Dresden relativistic effective core potential (SDD) for the rhodium atom. 3 Frequency calculations were performed at the same level of theory to characterize the nature of the stationary points as minima or saddle points. All the ground state structures were characterized with real vibrational frequencies. To check the reliability of the functional, the singlet-triplet energy separations of all the borylenes were calculated at three different levels of theory (M06-2X, wB97XD and PBE0, zero point correction energy is not included, ). 4-5 Natural bonding analysis was performed with the natural bond orbital (NBO) 6 partitioning scheme as implemented in the Gaussian 09 suite of programs. 7 Dispersion effects were incorporated by using the D3 version of Grimme's dispersion correction coupled with the D3 damping function using the keyword "Empirical Dispersion=GD3" as implemented in Gaussian 09. 8 The natural resonance theory (NRT) was used for a representative molecule to calculate resonance structure weights at the same level of theory. 9