The Influence of the Solvation on the Bonding of Molecular Complexes of Diatomic Halogens With Nitrogen-Containing Donors and Their Stability With Respect to the Heterolytic Halogen-Halogen Bond Splitting.

In the framework of SMD approach a systematic computational study of structural, electronic and thermodynamic properties of molecular complexes of Cl, ICl and I with series of N-containing Lewis bases in solvents of different polarity was carried out. Results indicate that molecular complexes of Cl with strong and medium-strong LB undergo spontaneous ionization in the acetonitrile solution. The increase of the solvent polarity can change the nature of interaction in X'XLB systems from molecular X'X ← LB donor-acceptor complexes to 3-center 4-electron bound X'→X ← LB in solvents of medium polarity and to the contact ion pairs X'→[XLB] in polar solvents.

Facile heterolytic bond splitting of molecular chlorine upon reactions with Lewis bases: Comparison with ICl and I.

Formation of molecular complexes and subsequent heterolytic halogen-halogen bond splitting upon reactions of molecular Cl with nitrogen-containing Lewis bases (LB) are computationally studied at M06-2X/def2-TZVPD and for selected compounds at CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz levels of theory. Obtained results are compared with data for ICl and I molecules. Reaction pathways indicate, that in case of Cl∙LB complexes the activation energies for the heterolytic Cl-Cl bond splitting are lower than the activation energies of the homolytic splitting of Cl molecule into chlorine radicals.

Structures and stability of I and ICl complexes with pyridine: Ab initio and DFT study.

Theoretical investigation of thermodynamic stability and bonding features of possible isomers of the molecular and ionic complexes of pyridine with molecular iodine and iodine monochloride IX (X = I,Cl) is presented. M06-2X DFT functional is found to provide bond distances and dissociation energies which are close to those obtained at high-level ab initio CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz benchmark computations for the most stable isomers, formed via donation of a lone pair of nitrogen atom of pyridine to the iodine atom. These isomers are by 23-33 kJ mol (in case of I) and by 39-56 kJ mol (in case of ICl) more stable than other molecular complexes.

Lewis acid stabilized group 13-15 element analogs of ethylene.

Stabilization of hydrogen-substituted group 13-15 compounds H EE'H (E = B, Al, Ga; E' = P, As, Sb) by Lewis acids is considered at B3LYP/def2-TZVP, B3LYP-D3/def2-TZVP and M06-2X/def2-TZVP levels of theory. It is shown, that for many Lewis acids additional reactivity beyond the DA complex formation with H EE'H monomer is expected. In case of complexation with E(C F ) , F/H exchange reactions with group 13 bound hydrides are predicted to be exothermic and accompanied by the activation energies which are smaller than dissociation of the complex into components.

Unusual molecular complexes of antimony fluoride dimers with acetonitrile and pyridine: structures and bonding.

The structures of two new molecular complexes of antimony pentafluoride with pyridine (Py) and acetonitrile (AN), SbF·Py and SbF·AN, and a molecular complex of antimony trifluoride SbF·Py and its ionic derivative [HPy][SbF] in the solid state have been determined by single crystal X-ray structural analysis. The complexes SbF·AN and SbF·Py are the first structurally characterized compounds of dimeric antimony fluorides. To reveal the nature of bonding in the complexes and their stability, DFT computations of the electronic structure and thermodynamic characteristics were performed, in particular the analysis of the electrostatic potentials, the orbital interactions and the topology.

Phosphanylalanes and Phosphanylgallanes Stabilized only by a Lewis Base.

The synthesis and characterization of the first parent phosphanylalane and phosphanylgallane stabilized only by a Lewis base (LB) are reported. The corresponding substituted compounds, such as IDipp⋅GaH PCy (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) were obtained by the reaction of LiPCy with IDipp⋅GaH Cl. However, the LB-stabilized parent compounds IDipp⋅GaH PH (3) and IDipp⋅AlH PH (4) were prepared via a salt metathesis of LiPH ⋅DME with IDipp⋅E'H Cl (E'=Ga, Al) or by H -elimination reactions of IDipp⋅E'H (E'=Ga, Al) and PH , respectively.

Complex beryllium amidoboranes: Structures, stability, and evaluation of their potential as hydrogen storage materials.

Complex beryllium amidoboranes M [Be(NH BH ) ] (M = Li-Cs, x = 1,2) have been computationally studied at M06-2X/def2-TZVPPD//B3LYP/def2-TZVPPD level of theory. Compounds are predicted to be stable at room temperature but release H on heating. Agostic Be…HB bonds play an important role in stabilization of oligomeric beryllium imidoboranes.

Initial gas phase reactions between Al(CH3)3/AlH3 and ammonia: theoretical study.

Mechanisms of initial stages of gas phase reactions between trimethylaluminum and ammonia have been explored by DFT studies. Subsequent substitution of CH3 groups in AlMe3 by amido groups and substitution of hydrogen atoms in ammonia by AlMe2 groups have been considered. Structures of Al(CH3)x(NH2)3-x, NHx(Al(CH3)2)3-x (x = 0-3) and related donor-acceptor complexes, dimerization products, and reaction pathways for the methane elimination have been obtained.

Structures and stability of molecular InBr3Py(x) (x = 1-3) complexes: unexpected solid state stabilization of dimeric In2Br6Py4 as compared to valence-isoelectronic group 15 and 17 halogen bridging dimers.

Molecular structures of series of InBr3Py(x) complexes (x = 1-3) in the solid state have been determined by single crystal structure analysis. For x = 2, an unexpected dimeric In2Br6Py4 structure, which features a nearly planar In2Br6 unit, has been established. This structure completes the series of known valence-isoelectronic dimeric molecules of group 17 (I2Cl6) and group 15 elements (As2Cl6·2PMe3).

Structural and thermodynamic properties of molecular complexes of aluminum and gallium trihalides with bifunctional donor pyrazine: decisive role of Lewis acidity in 1D polymer formation.

Solid state structures of group 13 metal halide complexes with pyrazine (pyz) of 2:1 and 1:1 composition have been established by X-ray structural analysis. Complexes of 2:1 composition adopt molecular structures MX3·pyz·MX3 with tetrahedral geometry of group 13 metals. Complexes of AlBr3 and GaCl3 of 1:1 composition are 1D polymers (MX3·pyz)∞ with trigonal bipyramidal geometry of the group 13 metal, while the weaker Lewis acid GaI3 forms the monomeric molecular complex GaI3·pyz, which is isostructural to its pyridine analog GaI3·py.

Do solid-state structures reflect Lewis acidity trends of heavier group 13 trihalides? Experimental and theoretical case study.

Lewis acidity trends of aluminum and gallium halides have been considered on the basis of joint X-ray and density functional theory studies. Structures of complexes of heavier group 13 element trihalides MX(3) (M = Al, Ga; X = Cl, Br, I) with monodentate nitrogen-containing donors Py, pip, and NEt(3) as well as the structure of the AlCl(3)·PPh(3) adduct have been established for the first time by X-ray diffraction studies. Extensive theoretical studies (B3LYP/TZVP level of theory) of structurally characterized complexes between MX(3) and nitrogen-, phosphorus-, arsenic-, and oxygen-containing donor ligands have allowed us to establish the Lewis acidity trends Al > Ga, Cl ≈ Br > I.

Fast H/D exchange of B,B',B''-tribromoborazine in C6D6 in the presence of aluminum tribromide: first evidence for an electrophilic substitution reaction of borazines in solution.

A solution of B,B',B''-tribromoborazine (BrBNH)(3) in excess C(6)D(6) in a sealed NMR tube shows no changes for over 14 months at room temperature but undergoes fast (within minutes) H/D exchange in the presence of AlBr(3) as a Lewis acid, as evidenced by (1)H, (2)H, (11)B, and (27)Al NMR spectroscopy. The proposed electrophilic exchange mechanism is in agreement with the results of DFT computations. To our knowledge, this is the first example of the electrophilic substitution reaction of borazines in solution.

Donor-acceptor complexes of borazines.

Donor-acceptor complexes of borazine (BZ) and its substituted derivatives with Lewis acids (A = MCl(3), MBr(3); M = B, Al, Ga) and Lewis bases (D = NH(3), Py) have been theoretically studied at the B3LYP/TZVP level of theory. The calculations showed that complexes with Lewis bases only are unstable with respect to dissociation into their components, while complexes with Lewis acids only (such as aluminum and gallium trihalides) are stable. It was shown that formation of ternary D→BZ→A complexes may be achieved by subsequent introduction of the Lewis acid (acceptor A) and the Lewis base (donor D) to borazine.