Donor-acceptor complexes MX 3 -D (M ) Al, Ga, In; X ) F, Cl, Br, I; D ) YH 3 , PX 3 , X -; Y ) N, P, As) and their components have been studied using self-consistent field and hybrid Hartree-Fock/density functional (B3LYP) methods with effective core potentials. The theoretical dissociation energies of the MX 3 -D complexes decrease in the orders F > Cl > Br > I, Al > Ga < In, and N . P g As for all investigated complexes. The calculated (B3LYP/LANL2DZP) dissociation energies for ammonia adducts are on average 7 kJ mol -1 higher than those from experiment. There is no correlation between the dissociation energy and the degree of charge transfer. Complexes of ammonia and metal fluorides have mostly ionic metal-donor bonds, while the other donor-acceptor adducts are mostly covalently bonded. In addition, a significant charge redistribution between the terminal atoms leads to further electrostatic stabilization of ammonia adducts. Coulomb interactions destabilize MX 3 -PX 3 complexes, and despite some experimental indications, the existence of these particular complexes in the gas phase is improbable. Distortion of MX 3 from planarity under complex formation leads to decreasing X-M-X angles. These decreasing angles correlate well with increasing M-X bond lengths. For all investigated MX 3 -Xsystems a strong correlation of the MX 3 -Xdissociation energy with the M-X bond length increase is found. Correlations between the pyramidal angle X-M-Y and the length of the adjacent M-Y bond have been found for each donor atom Y. All observed trends in structural and thermodynamic properties are qualitatively explained on the basis of a simple electrostatic model.

Quantum-chemical calculations with gradient-corrected (B3LYP) density functional theory have been carried out for iron bispentazole and ferrocene. The calculations predict that Fe(eta5-N5)2 is a strongly bonded complex which has D5d symmetry. The theoretically predicted total bond energy that yields Fe in the 5D ground state and two pentazole ligands is Do = 109.0 kcal mol(-1), which is only 29 kcal mol(-1) less than the calculated bond energy of ferrocene (Do = 138.0 kcal mol(-1); experimental: 158 +/- 2 kcal mol(-1)). The compound Fe(eta5-N5)2 is 260.5 kcal mol(-1) higher in energy than the experimentally known isomer Fe(N2)5, but the bond energy of the latter (Do = 33.7 kcal mol(-1)) is much less. The energy decomposition analyses of Fe(eta5-N5)2 and ferrocene show that the two compounds have similar bonding situations. The metal-ligand bonds are roughly half ionic and half covalent. The covalent bonding comes mainly from (e1g) eta5-N5- --> Fe2+ pi-donation. The previously suggested MO correlation diagram for ferrocene is nicely recovered by the Kohn-Sham orbitals. The calculated vibrational frequencies and IR intensities are reported.

The gas-phase Lewis acidity of group 13 element aryl and perfluorinated aryl derivatives E(C6H5)3, E(C6H4F)3, and E(C5F5)3 (E = B, Al, Ga) toward different donor molecules (NH3, H2O, PH3, H−, CH3 −, F−) has been theoretically studied at the RI-BP86/def2-TZVPP level of theory. The following order of the acceptor ability has been established: E(C6H5)3 ≈ E(C6H4F)3 < E(C6F5)3 ≈ ECl3. The acceptor strengths of E(C6H5)3 and E(C6H4F)3 are comparable to each other but much weaker compared to E(C6F5)3, which has a similar acceptor strength to those of the corresponding trihalides ECl3. The acceptor ability of ER3 decreases in the order Al > Ga > B. In the gas phase, Al(C6F5)3 is found to be a stronger Lewis acid than B(C6F5)3 toward all electron donors but H−. In contrast to AlCl3, which forms stable dimers, Al(C6F3)3 is monomeric and therefore has a much higher Lewis acid reactivity . The reactivity of perfluorinated derivatives E(C5F5)3 (E = B, Al, Ga) toward ammonolysis and hydrolysis processes and L2ZrMe2 (L = Cl, Cp, Cp*) as cocatalysts in olefin polymerization is also discussed.

An ab initio investigation of the chemical vapor deposition of AlN from the AlCl3NH3 adduct is presented. Geometries, harmonic vibrational frequencies and relative energies for the AlCl3NH3 adduct, its dissociation products AlCl n , NH n (n = 1−3), and ring and cluster compounds [(Cl2AlNH2) n (n = 1, 2), (ClAlNH) n (n = 1, 2, 3, 4, 6)] are discussed. The Al−N bond lengths in the investigated compounds are strongly dependent on the coordination numbers of the aluminum and nitrogen centers, decreasing from 2.0 Å for 4-coordinated Al/N centers to 1.79 and 1.68 Å for 3- and 2-coordinated Al/N centers, respectively. Thermodynamic analysis shows that dissociation of Cl x AlNH x (x = 2, 3) compounds with elimination of HCl and simultaneous formation of oligomeric forms is preferable to the process of dissociation into components or simple HCl detachment. Under standard conditions gaseous 4-coordinated Al/N compounds (ClAlNH)6 and (ClAlNH)4 are more stable than 3-coordinated (ClAlNH)2 and (ClAlNH)3 compounds. In 4-membered rings and clusters, the electrostatic repulsion between nearby Al−Al and N−N atoms makes reorganization to 6-membered rings extremely favorable. The suggested mechanism of AlN deposition involving cluster formation in the gas phase is discussed.

The structures of the parent compounds of phosphanyl- and arsanylboranes, H(2)BPH(2) and H(2)BAsH(2), were calculated by DFT-B3LYP methods. Such compounds have not previously been obtained preparatively. By applying the concept of Lewis acid/base stabilisation, [(CO)(5)W(H(2)EBH(2).NMe(3))] (E=P (3), As (4)) derivatives have been synthesised by the metathesis reactions between Li[(CO)(5)WEH(2)] and ClH(2)BNMe(3) (E=P, As). Comprehensive thermodynamic studies on these systems verify the high stability of the Lewis acid/base stabilised complexes. Unexpected based on the thermodynamic calculations, UV radiation of the phosphanylborane 3 leads to the dinuclear phosphanido-bridged complex [(CO)(8)W(2)(mu-PHBH(2).NMe(3))(2)] (5) by H(2) and CO elimination.