Theoretical study of the stability of species ABH3(ALi…Ne) (original) (raw)
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
The Journal of Physical Chemistry A, 2012
Equilibrium structures and energies of gas-phase molecular complexes SiH 4 ···BH 3 , SiH 4 ···B 2 H 6 , and SiH 4 ···BCl 3 were determined using second-order Møller−Plesset perturbation theory (MP2) and the aug-cc-pVTZ basis set, with and without explicit core electron correlation. Single-point energies were calculated for the MP2-optimized structures using MP2 with the aug-cc-pVQZ basis set and using coupled cluster theory (CCSD(T)) with both the aug-cc-pVTZ and the aug-cc-pVQZ basis sets to extrapolate to the complete basis set (CBS). Partition functions were calculated using the harmonic oscillator/rigid rotor approximation at the MP2/aug-cc-pVTZ level of theory. The explicit core electron correlation is demonstrated to have significant impact on the structures and binding energies and binding enthalpies of these complexes. The binding enthalpies were obtained at various temperatures ranging from 0 K to the dissociation temperatures of the complexes. The potential energy surfaces of the three complexes were explored, and no transition states were found along the pathways from separated species to the complexes.
H⋯σ interactions – an ab initio and `atoms in molecules' study
Chemical Physics Letters, 2004
An ab initio MP2/aug-cc-pVTZ study has been carried out on XH þ 4 Á Á ÁH 2 and [XH þ 4 (H 2 ) 4 ]Á Á ÁH 2 complexes (where X ¼ N, P, As, Sb, Bi). The investigated complexes are energetically stable and characterized by the existence of X-HÁ Á Ár and XÁ Á Ár interactions. The interaction energy decomposition indicates that differences in the nature of interactions for face and vertex isomers are not qualitative. The AIM theory has been also applied to analyze the properties of the bond critical points: their electron densities and their Laplacians.
In this work, the spectroscopic information, stability and aromaticity of the boron-nitrogen azulene and naph-thalene molecules are provided by the use of CC2 (geometry optimization, dipole moment, UV–vis spectrum calculations) and DFT (vibrational spectrum and NMR calculations) meth-odologies. One isomer of the investigated boron-nitrogen naphthalene (boroazanaphthalene) and two isomers of boron-nitrogen azulene, 1,3,4,6,8-pentaaza-2,3a,5,7,8a-pentaboraazulene (BN-azulene) and 2,3a,5,7,8a-pentaaza-1,3,4,6,8-pentaboraazulene (NB-azulene), are stable systems. However, these molecules have different properties, i.e., different stability, dipole moment, and aromaticity based on the NICS approach. BN-naphthalene has a high dipole moment magnitude showing high polar character, while naphthalene is apolar. BN-and NB-azulene are weakly polar, while ordinary azulene is highly polar in character. Also, substitution of C atoms by B and N atoms decreases the aromaticity. In the case of NB-azulene, the seven-membered ring has anti-aromaticity behavior while both rings of BN-azulene exhibit aromaticity. We expect that the new theoretical data provided in this work will be useful in identifying and characterizing experimentally the compounds investigated, and in helping our understanding of the chemistry of boron-nitrogen molecules.
An ab initio reinvestigation of the geometric and electronic structure of boron trioxide
Journal of Molecular Structure: THEOCHEM, 1981
In an attempt to resolve the controversy over the structure of the boron trioxide (B,O,) molecule an ab initio molecular orbital study employing a minimal STO-3G basis set with complete geometry optimization is reported. Our results indicate that B,O, is a planar "w" shaped molecule with a rather small inversion barrier around the central atom and a quite important coupling between BOB and OBO angles. The computed bond distances are consistent with previous electron diffraction results, whereas the apex angle is in better agreement with the most recent IR study. The results obtained by the MNDO method are in good agreement with the ab initio ones. The electronic structure of B,O, is discussed by means of Walsh diagrams and Mulliken population analysis.
The story of the B 4 H 4 molecule told again
Computational and Theoretical Chemistry
Employing ab initio multireference and coupled-cluster methods along with correlation consistent basis sets we have studied three geometrical isomers of the (hydro)borane B 4 H 4 molecule, namely, the highly symmetric geometrical configuration T d (regular tetrahedron) and two isomers of planar C s geometries tagged T d (II), C s (I), and C s (III), respectively. Mostly for reasons of consistency the species BH(X 1 R + , a 3 P), BH 2 (X 2 A 1), and H 2 BBH 2 (D 2h , D 2d) have also been examined at the same level of theory. It was reconfirmed that the global minimum of B 4 H 4 is the planar C s (I) lower by 6 kcal/mol than T d (II), while C s (III) is 13 kcal/mol above Cs(I). With an emphasis on the concept of chemical bond particularly for the three B 4 H 4 isomers I, II, and III, we offer quantitative geometric and energetic results for all species studied.
Equilibrium Structure and Torsional Barrier of BH 3 NH 3
The Journal of Physical Chemistry A, 2008
Born-Oppenheimer equilibrium structures, r e BO , of the electronic ground state of the borazane (BH 3 NH 3 ) molecule of C 3V point-group symmetry are computed ab initio using the CCSD(T) method with basis sets up to quintuple-quality. Inclusion of the counterpoise correction and extrapolation of the structural parameters to the complete basis set limit yield a best estimate of r e BO of BH 3 NH 3 . The anharmonic force field of BH 3 NH 3 , computed at the CCSD(T) level of theory with a basis set of triple-quality, allows the determination of semi-experimental equilibrium rotational constants, which in turn result in a semi-experimental equilibrium structure, r e SE . The r e BO and r e SE structures are in excellent agreement, indicating the validity of the methods used for their determination. The empirical mass-dependent structure, r m (1) , of BH 3 NH 3 is also determined. Although it is inferior in quality to the previous two structures, it is much more accurate than the standard empirical r 0 and r s structures reported earlier for BH 3 NH 3 . The semi-experimental r e SE as well as the empirical r m
The ab initio limit quartic force field of BH 3
Journal of Computational Chemistry, 2005
The complete quartic force field of BH 3 has been converged to the ab initio limit by extrapolation of core-valence correlation-consistent basis set series (cc-pCVXZ, X ϭ T, Q, 5) of all-electron CCSD(T) (coupled-cluster singles and doubles with perturbative triples) energy points. Additional computations including full coupled-cluster treatments through quadruple excitations (CCSDTQ), scalar relativistic effects, and diagonal Born-Oppenheimer corrections (DBOC) were concurrently executed. Within second-order vibrational perturbation theory (VPT2) our quartic force field yields the fundamental frequencies 1 ϭ 2502.3 cm Ϫ1 , 2 ϭ 1147.2 cm Ϫ1 , 3 ϭ 2602.1 cm Ϫ1 , and 4 ϭ 1196.5 cm Ϫ1 , in excellent agreement with observed gas-phase fundamentals, displaying a mean absolute error of only 0.3 cm Ϫ1. Our converged prediction for the equilibrium bond length of BH 3 is r e ϭ 1.1867 Å.
Journal of Molecular Structure: THEOCHEM, 2008
The conformations of boric acid (1), its conjugate basis (2) and borate anion (3) have been investigated with the B3LYP, HF, MP2 and QCISD methods with a variety of basis sets. Transition-state structures connecting the various minima have been computed. Relative energies are reported at the G3(MP2)//B3LYP level of theory. The lowest-energy conformation of boric acid has C 3h symmetry. The C s conformer lies 4.1 kcal/mol higher in energy and the barrier for inter-conversion is 7.8 kcal/mol. The lowest-energy conformation of (HO) 2 BO À has C 2v symmetry. There are two conformations lying higher in energy by 1.7 and 9.1 kcal/mol, with barriers of 7.8 and 10.3 kcal/mol, respectively. For borate anion two distinct S 4-symmetry minima were located which differ in energy by 1.5 kcal/mol. The computed enthalpies of formation for 1, 2 and 3 are À236.3, À242.9 and À320.8 kcal/mol, respectively.
, and B10H1, are interpreted as resonance hybrids of valence bond structures that only contain two-center two electron bonds. Graph-theoretical techniques are used to count the large number of structures incorporated in the hybrids. Calculated bond orders and charges are compared with the results of LCAO-MO-SCF calculations and with three-center valence bond models. The heats of atomization can be correlated with a 4 term linear equation based on the numbers of neighboring boron atom pairs, terminal BH bonds, bridging BH bonds, and estimates of resonance energies. Resonance energies comprise 1 1 to 29% of the atomization energies for these boron hydrides.
The vibrational spectra of the boron halides and their molecular complexes, part 5 An ab initio stud
Theor Chem Acc, 1997
The optimized structures, interaction energies, Mulliken charges and vibrational spectra of three conformers of a 1:1 complex between boron tri¯uoride and carbon dioxide have been determined by means of ab initio calculations at the second-order level of Mùller-Plesset perturbation theory, using the 6-31G* basis set. All three structures feature a BÁ Á ÁO electron donoracceptor interaction. One of the structures, in which the carbon dioxide axis eclipses one of the BF bonds, was found to be a genuine minimum, one (the corresponding staggered form) a ®rst-order saddle point and the third (a linearly bonded BÁ Á ÁOCO species) a second-order transition state. The computed infrared spectrum of the preferred conformer has been used to predict the appearance of the spectrum of boron tri¯uoride and carbon dioxide co-deposited in cryogenic matrices, which will be reported in a forthcoming publication.