Abderrahim Boutalib

ABSTRACT Octahydrotriborate salts, B3H8 , have been prepared by the reaction of NaBH4 with Lewis ... more ABSTRACT Octahydrotriborate salts, B3H8 , have been prepared by the reaction of NaBH4 with Lewis acids such as BX3·BDMA (BDMA = benzyldimethylamine, × = Cl,Br) or C2H5I in diglyme. The presence of BH3·BDMA as a by-product in the former reaction provides new insight into the reaction mechanism of B11H14 formation. In acetonitrile-water solutions of HCl or CH3CO2H, the B3H8 anion reacted to give B3H7CH3CN or B3H7CH3CO2 characterized by B NMR spectroscopy. Their kinetic hydrolysis study was consistent with NMR analysis. Reaction of Bu4NB3H8 and CuCl2 at 0°C produced pure B3H6Cl2 . An AM1 theoretical study of the substituted derivatives B3H7L (L = Cl, CH3CN, CH3CO2 , OH) and B3H6L2 (L = Cl) is reported.

Comparative G2(MP2) Study of H 3 NBX 3 and H 3 PBX 3 (X = H, F, and Cl) Donor−Acceptor Complexes

The Journal of Physical Chemistry A

... BP S15 Marrakech, Morocco. Ignacio Nebot-Gil and Francisco Tomás §. Departament de Química-... more

Substituent effect on ammonia–borane donor–acceptor complexes: a G2(MP2) molecular orbital study

Journal of Molecular Structure THEOCHEM

H 3 BNH n Me 3−n and Me 3−n H n BNH 3 (n = 0-3) donor-acceptor complexes have been studied with t... more H 3 BNH n Me 3−n and Me 3−n H n BNH 3 (n = 0-3) donor-acceptor complexes have been studied with the G2(MP2) method. Predicted equilibrium structures and dissociation energies have been correlated to the degree of substitution on the donor and the acceptor separately. It is found that successive methyl substitutions on boron reduce the dissociation energies of the complexes, contrary to the successive substitutions on nitrogen. The NBO partitioning scheme suggests that there is no correlation between the charge transfer and the dissociation energies. These results are interpreted in terms of the changes in the HOMO − LUMO gap, the type of acceptor and donor involved, and distortion of the acceptor and donor moieties. ᭧ 1998 Elsevier Science B.V. All rights reserved.

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Theoretical study of Me 2S·B 11H 13 complex and intermediate structures of B 11H 15 derivative

Journal of Molecular Structure THEOCHEM

ABSTRACT In this paper we have theoretically studied different isomers of the Me2S·B11H13 complex... more ABSTRACT In this paper we have theoretically studied different isomers of the Me2S·B11H13 complex using the AM1 semi-empirical SCF-MO calculations. The calculated geometries were in good agreement with those determined by using X-ray diffraction. The comparison of heats of formation for the three isomers showed that the 2-Me2S·B11H13 conformation (−12.47 kcalmol−1) is more stable than 1-Me2S·B11H13 (−7.64 kcalmol−1) and 7-Me2S·B11H13 (−7.20 kcalmol−1). However, the discussion of a suggested mechanism of their formation, using intermediate structures of B11H15 permitted us to conclude that the 7-Me2S·B11H13 conformation is kinetically favoured. The interaction between the H2 molecule and B11H13 is more important at the B1 and B2 centres than at the B7 centre, so the H2 elimination from B11H15 structures to form B11H13 is easier at the last of these.

Theoretical study of the isomerisation of the [B 11H 12O] − oxaborate cluster

Journal of Molecular Structure THEOCHEM

The structural complexity and chemical stability of the oxaborate [B11H12O]− ion made us use a qu... more The structural complexity and chemical stability of the oxaborate [B11H12O]− ion made us use a quantum chemical calculation which is an indispensable tool to complete the experimental data. Therefore, we have optimised the geometries of six possible structures of the anion [B11H12O]− using the semi-empirical method AM1. The latter method gives satisfactory results for the boron clusters. A comparison of the heat of formation and the frontier molecular orbital energies shows that the most stable structure is that where the oxygen atom is bound to three boron atoms in the open face of the cage. This structure is in good agreement with that proposed by analysing NMR spectrum data. We have also calculated the B–B, B–H and B–O bond lengths, the bond index and the charge distribution for this conformation. Finally, we have theoretically studied the isomerisation mechanism of the stablest structure in order to obtain the other structures. The highest activation barrier energy calculated for the first stage explains the stability of this compound. The isomerisation of the stablest isomer of the [B11H12O]− ion is found to occur by the migration of the bridged hydrogen on to the oxygen atom in order to provide the stablest conformation containing the OH function.

G2(MP2) Molecular Orbital Study of [H 3 AlXH 3 ] - (X = C, Si, and Ge) and H 3 AlYH 3 (Y = N, P, and As) Complexes

The Journal of Physical Chemistry A

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G2 Molecular Orbital Study of [H 3 AlXH] - (X = NH, PH, AsH, O, S, and Se) and H 3 AlYH (Y = OH, SH, SeH, F, Cl, and Br) Donor−Acceptor Complexes

The Journal of Physical Chemistry A

... Ball 11 has reported an ab initio (MP2/6-31G(d,p) level) study of X 3 AlOH 2 (X = H ... to th... more

Comparative G2(MP2) molecular orbital study of [H 3AlX(CH 3) 2] − (X=N, P, and As) and H 3AlY(CH 3) 2 (Y=O, S, and Se) donor–acceptor complexes

Journal of Molecular Structure THEOCHEM

H 3 AlX(CH 3 ) 2 ] 2 (X N, P, and As) and H 3 AlY(CH 3 ) 2 (Y O, S, and Se) donor±acceptor comple... more H 3 AlX(CH 3 ) 2 ] 2 (X N, P, and As) and H 3 AlY(CH 3 ) 2 (Y O, S, and Se) donor±acceptor complexes have been studied using G2(MP2) level of theory. The coordination mode, the structural and the methyl substitution effects upon complexation are analyzed. The interaction of the alane with the donor ligand is stronger in the anionic complexes than in the neutral ones and the methylated complexes are more stable than the hydrogenated ones. The coordination is ensured by tow interactions having a reverse character: interaction between a 0 symmetry fragment molecular orbital (stabilizing) and interaction between a 00 symmetry occupied molecular orbital (destabilizing) of the two fragments. A linear correlation has been established and discussed between the energetic and the structural effects upon methylation. The NBO partitioning scheme suggests that there is no correlation between the charge transfer and the G2(MP2) complexation energy. q

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Synthesis, structural characterization, and theoretical calculations of a new copper(I)-octahydrotriborate complex

Inorganic Chemistry

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A G2 study of H3BXHn (X=N, O, F, P, S, and Cl) donor–acceptor complexes

Journal of Molecular Structure THEOCHEM

Complexation energies of H 3 BXH n complexes (X N, O, F, P, S, and Cl; n 1, 2, 3) have been compu... more Complexation energies of H 3 BXH n complexes (X N, O, F, P, S, and Cl; n 1, 2, 3) have been computed at the G2 level of theory. G2 results show that the H 3 BXH 3 (X N, P) complexes are more stable than H 3 BXH 2 (X O, S) and H 3 BXH (X F, Cl) ones. This stability was related completely either to the nature of donor compounds, and to the pyramidalization of the monoborane. Two linear correlations were established. The first one is between experimental proton affinity of the XH n donor compounds, and complexation energies of the H 3 BXH n complexes. The second correlation is between the ЄHBH bond angles and the complexation energies of the H 3 BXH n complexes calculated at the G2 level of theory. ᭧

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A comprehensive computational study of N2H+–XH, N2H+–X2, and N2H+–XY(YX) (X=Y=F, Cl, and Br) proton bound complexes

Journal of Molecular Structure THEOCHEM

The results of theoretical studies on structures and energetics are presented for proton-bound co... more The results of theoretical studies on structures and energetics are presented for proton-bound complexes N2H+–XH, N2H+–X2, and N2H+–XY(YX) (X=Y=F, Cl, and Br). In all the monocations complexes, the halogen atom shares a proton with N2. The calculated energetic results show that the stability decreases when descending in the corresponding periodic table column. The possible proton transfer dissociation processes of N2H++XH,

G2(MP2) molecular orbital study of the substituent effect in the H 3BPH 3− n F n ( n=0–3) donor–acceptor complexes

Chemical Physics Letters

3 yn n 3yn n substitution. The NBO partitioning scheme shows that this stability was related to t... more

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Ab initio study of the formation of B 3H 7 derivative from B 3H 8 − anion protonation

Journal of Molecular Structure THEOCHEM

ABSTRACT Formation of B3H7 species from the protonation of B3H8− has been studied by ab initio ca... more ABSTRACT Formation of B3H7 species from the protonation of B3H8− has been studied by ab initio calculations at the HF and correlated MP2 levels using extended basis set 6-31+G∗∗. Two elementary processes, B3H8−+H+→B3H9 and B3H9→B3H7+H2, have been investigated. The calculated absolute values of B3H8−+H+→B3H9 protonation energy are very high (above 314kcalmol−1). Loss of molecular hydrogen from B3H9 proceeds with an activation barrier above 12kcalmol−1, leading to a B3H7 one-bridged structure. The activation barrier of reverse reaction is found non-negligible when the zero-point energy correction is added. The calculated energy and activation barriers of B3H7 rearrangement are small, confirming the fluxional behaviour for this species. However, a mechanism of B3H7 formation is proposed. The inclusion of a solvent reaction field using water as a solvent (ε=78.54) has a small influence on the energies and molecular properties.