Structural, energetic, electronic, bonding, and vibrational properties of Ga3O, Ga3O2, Ga3O3, Ga2O3, and GaO3 clusters

The results of density functional theory based calculations on Ga3O, Ga3O2, Ga3O3, Ga2O3, and GaO3 clusters are reported here. A preference for planar arrangement of the constituent atoms maximizing the ionic interactions is found in the ground state of the clusters considered. The sequential oxidation of the metal-excess clusters increases the binding energy, but the sequential removal of a metal atom from the oxygen-excess clusters decreases the binding energy. The increase in the oxygen to metal ratio in these clusters is accompanied by increase in both electron affinity and ionization potential. The ionization induced structural distortions in the neutral clusters are relatively small, except those for Ga3O2. In anionic (cationic) clusters, the added (ionized) electron is shared by the Ga atoms, except in the case of GaO3. The vibrational frequencies and charge density analysis reveal the importance of the ionic Ga-O bond in stabilizing the gallium oxide clusters considered in this study.     

Theoretical assessing on the coordination mode and bonding in heteronuclear group‐13 dimetallocene

In this article, the coordination mode, the nature of metal–ligand interaction and dimetallic bonding in heteronuclear group‐13 dimetallocene (CpMM′CpI₂; Cp = C₅H₅, M/M′=B, Al, Ga, In, and Tl) have been investigated within the framework of the atoms in molecules theory, electron localization function, and energy decomposition analysis. The calculated results show that the symmetries of the title compounds, the coordination modes between the metal and ligand, the strength and nature of M‐ligand interaction and M M′ bond are well correlated with the periodicity changing of group‐13 metal atom going from the lighter to the heavier (B, Al, Ga, In, and Tl). The heavier group 13 metal atom is corresponding to the higher symmetry, stronger metal–ligand interaction, and weaker dimetallic bond. The covalent characters of both metal–ligand interaction and dimetallic bond are decreasing in the sequence of M′=Al, Ga, In, and Tl, for the same M atom.     

Photoelectron spectroscopy and density functional theory of puckered ring structures of Group 13 metal-ethylenediamine

The ethylenediamine (en) complexes of Al, Ga, and In atoms were prepared in laser-vaporization supersonic molecular beams and studied with pulsed field ionization zero electron kinetic energy photoelectron spectroscopy and density functional theory. Several conformers of each metal complex are obtained by B3LYP calculations, and a five-membered cyclic structure is identified by combining the experimental measurements and theoretical calculations. Adiabatic ionization potentials, vibrational frequencies, and bond dissociation energies are determined for the ring structure. The ionization potentials of the Al, Ga, and In species are measured to be 32 784 (5), 33 324 (5), and 33 637 (7) cm(-1), respectively, and metal-ligand dissociation energies of the ionic and neutral complexes are calculated to be 60.2/16.2 (Al(+)/Al), 55.5/13.0 (Ga(+)/Ga), and 50.0/11.4 (In(+)/In) kcal mol(-1). Metal-ligand stretch and bend as well as a number of ligand-based vibrations are measured. Harmonic frequencies and anharmonicities of the M(+)-N (M=Al,Ga,In) stretch are determined for all three M(+)-en ions and the C-C-N bend of Ga(+)-en and In(+)-en. In comparison to monodentate methylamine, the bidentate binding of ethylenediamine leads to a significantly lower ionization potential and higher metal-ligand bond strength of the metal complexes.     

Aluminum, gallium, and indium hydrazides and the generation of oligonuclear element-nitrogen cages: molecular intermediates on the way to element nitrides

Organoelement aluminum, gallium, and indium hydrazides, [R(2)ENHN(H)R'](2) (E = Al, Ga, In), are easily available from the corresponding trialkylelement compounds, ER(3), and hydrazines, H(2)NN(H)R', via elimination of the respective hydrocarbons. Their diverse molecular structures are derived from four-, five-, or six-membered element-nitrogen heterocycles. Their stepwise thermolysis under carefully controlled conditions was shown to proceed along one of several different well-defined routes. Cleavage of the N-N bonds afforded aluminum or gallium imides, [REN(H)](n), with up to eight metal atoms in a single molecule, while preservation of the N-N bonds led to interesting cages in which intact N-N bonds of formally dianionic hydrazinediides bridge the metal atoms via their two adjacent donor atoms. Further thermolysis yielded the amorphous element nitrides via the gradual degradation of the hydrazinediide groups. Several intermediates have been isolated and provided insight in the course of these reactions. A particularly interesting compound was one that features a hydrazinetetraide unit, [N-N](4-), that is stabilized by coordination to six gallium atoms.     

Facile Modulation of FLP Properties: A Phosphinylvinyl Grignard Reagent and Ga/P‐ and In/P2‐Based Frustrated Lewis Pairs

An Al/P‐based frustrated Lewis pair (FLP) reacted with PhMgCl by an unexpected transmetalation and formation of a phosphinylvinyl Grignard reagent. This compound is well suited for the transfer of the basic FLP component to other Lewis acidic metal atoms and allowed the generation of a Ga/P and an In/P₂ FLP. The Ga FLP showed a behavior different to that of the corresponding Al FLP, the In FLP allowed the chelating coordination of an Au atom by Au−Cl bond activation.     

Structural variation in transition-metal bispidine compounds

The experimentally determined molecular structures of 40 transition metal complexes with the tetradentate bispyridine-substituted bispidone ligand, 2,4-bis(2-pyridine)-3,7-diazabicyclo[3.3.1]nonane-9-one [M(bisp)XYZ]n+; M = CrIII, MnII, FeII, CoII, CuII, CuI, ZnII; X, Y, Z = mono- or bidentate co-ligands; penta-, hexa- or heptacoordinate complexes) are characterized in detail, supported by force-field and DFT calculations. While the bispidine ligand is very rigid (N3...N7 distance = 2.933 +/- 0.025 A), it tolerates a large range of metal-donor bond lengths (2.07 A < sigma(M-N)/4 < 2.35 A). Of particular interest is the ratio of the bond lengths between the metal center and the two tertiary amine donors (0.84 A < M-N3/M-N7 < 1.05 A) and the fact that, in terms of this ratio there seem to be two clusters with M-N3 < M-N7 and M-N3 > or = M-N7. Calculations indicate that the two structural types are close to degenerate, and the structural form therefore depends on the metal ion, the number and type of co-ligands, as well as structural variations of the bispidine ligand backbone. Tuning of the structures is of importance since the structurally differing complexes have very different stabilities and reactivities.     

Metastable Aluminum(I) Compounds: Experimental and Quantum Chemical Investigations on Aluminum(I) Phosphanides—An Alternative Channel to the Disproportionation Reaction?

The well known thermodynamic instability of Al and Ga monohalides is caused by the favored disproportionation process to the bulk metal and the trihalides. During this highly complex process, a number of metalloid clusters that are intermediates on the way to the metal have been trapped. Therefore, all observations in the field of metalloid Al/Ga clusters have been traced to this favored disproportionation process. The failure to form phosphanide‐substituted Al clusters, in contrast to the generation of similar Ga clusters and analogous Al amide clusters, was the starting point of this contribution. For aluminum(I) phosphanides, there exists a different decomposition route in which the salt‐like bulk material AlP and not Al metal is the final product. The synthesis of two molecular “AlP” intermediate species, together with supporting DFT calculations, provide plausible arguments for this decomposition route, which is thermodynamically favored for many AlR/GaR species and which, surprisingly, has not been discussed before.     

Complex formation of trimethylaluminum and trimethylgallium with ammonia: evidence for a hydrogen-bonded adduct

We have investigated the formation of gas-phase adducts of trimethylaluminum and trimethylgallium with ammonia using room-temperature Fourier transform infrared experiments and density functional theory calculations. Our results indicate for the first time that, at higher partial pressures, a product distinct from the well-known (CH3)3M:NH3 adduct grows in for both M = Al and M = Ga. Comparison of the experimental and calculated IR spectra, along with calculations of the energetics, indicates that this second product is the result of hydrogen bonding of a second NH3 molecule to the (CH3)3M:NH3 adduct and can be written as (CH3)3M:NH3...NH3. The binding energy of this hydrogen-bonded adduct is calculated to be 26.8 kcal/mol for M = Al and 18.4 kcal/mol for M = Ga and is lower in energy (more stable) relative to the 1:1 (CH3)3M:NH3 adduct by 7.2 kcal/mol for M = Al and 6.6 kcal/mol for M = Ga. In contrast, an alternative complex involving the formation of two separate M-N donor-acceptor bonds, which is written as H3N:(CH3)3M:NH3, is calculated to be lower in energy relative to (CH3)3M:NH3 by only 0.1 kcal/mol for M = Al and 0.2 kcal/mol for M = Ga and is not observed experimentally. These results show that hydrogen bonding plays an important role in the interaction of ammonia with metal organic precursors involving Al, Ga, and In, under typical metal organic chemical vapor deposition AlGaInN growth conditions.     

Metalloid Al- and Ga-clusters: a novel dimension in organometallic chemistry linking the molecular and the solid-state areas?

Formation and fragmentation of metal-metal bonds on the way between stable metal compounds in which the metal atoms are oxidised (e.g. isolated species in solution or metal salts in bulk) and the bulk metal are the fundamental steps to understand this process in which formation and chemical behaviour of metalloid Al and Ga clusters as intermediates are essential. Many examples of metalloid Al and Ga clusters show that their formation reflects a high degree of complexity like that of the simple seeming formation of the bulk metal itself: starting from metastable Al(i) and Ga(i) solutions containing small molecular entities, metalloid clusters grow during many self-organization steps including aggregation as well as irreversible redox cascades. This novel class of clusters seems to open a new dimension in chemistry between the molecular and the solid-state area, because, for the first time, it is shown that under well selected conditions definite molecular species, i.e. metalloid clusters, grow via the formation of additional metal-metal bonds and that the solid metal represents the final step.     

固氮酶底物配位活化的量子化学模拟

用EHMO法就Roussin红盐, MoFeS4(NO)2^2^-, Roussin黑盐及网兜状模型对C2H2,N2, NNH^+和NCH等固氮酶底物的配位活化进行了量子化学模拟. 综合考虑体系总能量与底物多重键的Mulliken键级的变化, 得知乙炔与二核簇相距1.2埃时为最佳活化构型;在Roussin黑盐及网兜状模型以“架炮"方式与乙炔组成的配位体系中, C≡C键呈5度仰角时为最佳活化构型. 铁比钼更有利于削弱C≡C键. 在N2, NNH^+NCH以“投网"方式与网兜模型组成的配位体系中, 底物的多重键受到较大的削弱. “投网"配位方式使兜口外氮原子上的电荷密度增加, 容易受亲电子试剂的进攻, H^+沿N-N轴线方向攻击N2对活化N≡N键最有利.     

Spectroscopic studies of aluminum and gallium complexes with oxalate and malonate in aqueous solution

The local structures of Ga(III) in aqueous oxalate and malonate complexes were studied by means of Ga K-edge EXAFS spectroscopy. Irrespective of the number and type of coordinated ligands, the EXAFS results showed very regular first coordination shells consisting of six oxygen atoms. Scattering paths from more distant atoms revealed that both oxalate and malonate form mononuclear chelate structures where one oxygen from each carboxylate group binds to Ga(III). Again, very little variation in bond distances and no changes in coordination modes were detected as the number of ligands coordinated to Ga(III) was varied. Based on the very close resemblance of IR spectra of oxalate and malonate complexes of Al(III), and the corresponding complexes of Ga(III), it is believed that the local structures of the Al(III) complexes are similar to those of the Ga(III) complexes in terms of ligand coordination modes and distortions. This conclusion was corroborated by results from theoretical frequency calculations.     

Optimizing small molecule activation and cleavage in three-coordinate M[N(R)Ar]3 complexes

The sterically hindered, three-coordinate metal systems M[N(R)Ar]3 (R = tBu, iPr; Ar = 3,5-C6H3Me2) are known to bind and activate a number of fundamental diatomic molecules via a [Ar(R)N]3M-L-L-M[N(R)Ar]3 dimer intermediate. To predict which metals are most suitable for activating and cleaving small molecules such as N(2), NO, CO, and CN(-), the M-L bond energies in the L-M(NH2)3 (L = O, N, C) model complexes were calculated for a wide range of metals, oxidation states, and dn (n = 2-6) configurations. The strongest M-O, M-N, and M-C bonds occurred for the d2, d3, and d4 metals, respectively, and for these d(n) configurations, the M-C and M-O bonds were calculated to be stronger than the M-N bonds. For isoelectronic metals, the bond strengths were found to increase both down a group and to the left of a period. Both the calculated N-N bond lengths and activation barriers for N2 bond cleavage in the (H2N)3M-N-N-M(NH2)3 intermediate dimers were shown to follow the trends in the M-N bond energies. The three-coordinate complexes of Ta(II), W(III), and Nb(II) are predicted to deliver more favorable N2 cleavage reactions than the experimentally known Mo(III) system and the Re(III)Ta(III) dimer, [Ar(R)N]3Re-CO-Ta[N(R)Ar]3, is thermodynamically best suited for cleaving CO.     

IR spectroscopy and density functional theory of small V+(N2)n complexes

V+(N2)n clusters are generated in a pulsed nozzle laser vaporization source. Clusters in the size range of n = 3-7 are mass selected and investigated via infrared photodissociation spectroscopy in the N-N stretch region. The IR forbidden N-N stretch of free nitrogen becomes strongly IR active when the molecule is bound to the metal ion. Photodissociation proceeds through the elimination of intact N2 molecules for all cluster sizes, and the fragmentation patterns reveal the coordination number of V+ to be six. The dissociation process is enhanced on vibrational resonances and the IR spectrum is obtained by monitoring the fragmentation yield as a function of wavelength. Vibrational bands are red-shifted with respect to the free nitrogen N-N stretch, in the same way seen for the C-O stretch in transition metal carbonyls. Comparisons between the measured IR spectra and the predictions of density functional theory provide new insight into the structure and bonding of these metal ion complexes.     

Formation, structure and bonding of metalloid Al and Ga clusters. A challenge for chemical efforts in nanosciences

The renaissance of Al and Ga cluster chemistry is presented in three steps: on the grounds of boron hydride chemistry and the Wade concept, the first step starts in the early nineties of the last century with the formation of single Al-Al and Ga-Ga bonds in molecular entities, obtained by different synthetic approaches. The special method via reaction of high-temperature molecules like AlCl and its disproportionation to Al metal and AlX(3) leads to the second step which started about 10 years ago: the formation of nanoscaled metalloid Al and Ga clusters as intermediates on the way to the metal. Based on the structure of several recent examples, bonding is discussed with respect to the structure of the elements and the generation of naked metal atom clusters. After discussion of the individual metalloid clusters including experiments of the gaseous species and discussion about the jellium model, the third step and main part of this review starts only a few years ago. This latest period hardly can be called a renaissance period as, so far, interactions of nanoscaled metal atom clusters in a perfect 1-, 2- or 3-dimensional arrangement of a crystal have never been investigated before. The most remarkable result in this perspective is the superconducting behaviour of a Ga(84) cluster compound in the crystalline state which had never been observed in metal atom clusters before. However, these experiments show that superconductivity is only observed if the clusters in the crystal are perfectly orientated: as a cluster arrangement of this type can hardly be fabricated by physical methods, these results, which have been predicted by theory, may be called a disillusionment for nanosciences; for chemistry, however, these conclusions pose a challenge.     

Cluster-assembled materials based on M12N12 (M = Al, Ga) fullerene-like clusters

We report the results of density functional theory calculations on cluster-assembled materials based on M(12)N(12) (M = Al, Ga) fullerene-like clusters. Our results show that the M(12)N(12) fullerene-like structure with six isolated four-membered rings (4NRs) and eight six-membered rings (6NRs) has a T(h) symmetry and a large HOMO-LUMO gap, indicating that the M(12)N(12) cluster would be ideal building blocks for the synthesis of cluster-assembled materials. Via the coalescence of M(12)N(12) building blocks, we find that the M(12)N(12) clusters can bind into stable assemblies by either 6NR or 4NR face coalescence, which enables the construction of rhombohedral or cubic nanoporous framework of varying porosity. The rhombohedral-MN phase is energetically more favorable than the cubic-MN phase. The M(12)N(12) fullerene-like structures in both phases are maintained and the M-N bond lengths between M(12)N(12) monomers are slightly larger than that in isolated M(12)N(12) clusters and the bulk wurtzite phases. The band analysis of both phases reveals that they are all wide-gap semiconductors. Because of the nanoporous character of these phases, they could be used for gas storage, heterogeneous catalysis, filtration and so on.     

维生素B1—金属配合物的制备及其分子结构

制得了M(th)Cl_3 (M=Zn(Ⅱ)、Cd(Ⅱ)、Mn(Ⅱ)、Co(Ⅱ))、Cu(thH)Cl_4和Hg_3(C_(12)H_(16)N_4OS)Cl_8三种类型的维生素B_1-金属配合物。结构表征表明,Zn、Cd、Mn、Co配合物属M—N配位型,Cu配合物属离子型,Hg配合物既有M—O键合,又有离子键存在。     

Group 13 Precursor Structures and Their Effect on Oxide Nanocrystal Formation

Precursor structures (PSs) in solution are expected to influence both nanocrystal formation mechanisms, as well as crystallization of specific polymorphs. Herein, Group 13 PS structures determined by pair distribution function and extended X-ray absorption fine structure analysis are reported. Corner-sharing octahedral dimers form from the metal nitrates dissolved in either water, isopropanol, or ethanol at room temperature contradicting previous studies that suggested monomers or larger Keggin clusters. Because all crystalline indium oxides have octahedral coordination, crystals can easily nucleate from the observed PSs. Similarly, MOOH (M=Al and Ga) with octahedral M coordination is expected to form readily from the PSs, whereas formation of γ-M₂O₃ requires a partial conversion to tetrahedral M coordination. This explains the long-standing observation of initial AlOOH formation as a bottleneck for γ-Al₂O₃ synthesis. Different indium polymorphs crystallize from the various solvents, and thus there is no obvious link between the PSs and observed polymorphism.     

Metal ion complexing properties of dipyridoacridine, a highly preorganized tridentate homologue of 1,10-phenanthroline

DPA (dipyrido[4,3-b;5,6-b]acridine) may be considered as a tridentate homologue of phen (1,10-phenanthroline). In this paper some of the metal ion complexing properties of DPA in aqueous solution are reported. Using UV-visible spectroscopy to follow the intense π-π* transitions of DPA as a function of pH gave protonation constants at ionic strength (μ) = 0 and 25 °C of pK(1) = 4.57(3) and pK(2) = 2.90(3). Titration of 10(-5) M solutions of DPA with a variety of metal ions gave log K(1) values as follows: Zn(II), 7.9(1); Cd(II), 8.1(1); Pb(II), 8.3(1); La(III), 5.23(7); Gd(III), 5.7(1); Ca(II), 3.68; all at 25 °C and μ = 0. Log K(1) values at μ = 0.1 were obtained for Mg(II), 0.7(1); Sr(II), 2.20(1); Ba(II), 1.5(1). The log K(1) values show that the high level of preorganization of DPA leads to complexes 3 log units more stable than the corresponding terpyridyl complexes for large metal ions such as La(III) or Ca(II), but that for small metal ions such as Mg(II) and Zn(II) such stabilization is minimal. Molecular mechanics calculations (MM) are used to show that the best-fit M-N length for coordination with DPA is 2.60 ?, accounting for the high stability of Ca(II) or La(III) complexes of DPA, which are found to have close to this M-N bond length in their phen complexes.     

Melting of alloy clusters: effects of aluminum doping on gallium cluster melting

Calorimetry measurements have been performed as a function of temperature for size-selected Ga(n-1)Al+ clusters with n = 17, 19, 20, 30-33, 43, 46, and 47. Heat capacities determined from these measurements are compared with previous results for pure Ga(n)+ clusters. Melting transitions are identified from peaks in the heat capacities. Substituting an aluminum atom appears to have only a small effect on the melting behavior. For clusters that show melting transitions, the melting temperatures and latent heats for the Ga(n-1)Al+ clusters are similar to those for the Ga(n)+ analogs. For Ga(n)+ clusters that do not show first-order melting transitions (n = 17, 19, and 30) the Ga(n-1)Al+ analogs also lack peaks in their heat capacities. The results suggest that the aluminum atom is not localized to a specific site in the solid-like Ga(n-1)Al+ clusters.     

Structural and thermodynamic properties of group 13 imidometallanes and their heavier analogues

Systematic theoretical studies of the [XMYH](n) inorganic rings and clusters (M = Al, Ga, In; Y = N, P, As; X = H, F, Cl, Br, I; n = 1-6) have been carried out using hybrid Hartree-Fock density functional theory. A consistent set of the structural and thermodynamic properties has been obtained. The stability of the MY bond decreases in the order Al > Ga >or= In; N > P > As. Terminal groups X have a minor influence on the subsequent elimination enthalpies of the clusters. In the case of X = H, hydrogen elimination makes formation of the [HMYH](6) oligomers from MH(3) and YH(3) thermodynamically favorable; while in the case of halide substituents, formation of [XMYH](6) is thermodynamically unfavorable, except for the system with the strongest MY bond (AlN). Substitution of the acidic hydrogen by X is favorable energetically for all [HMYH](6) clusters, but is complicated by the processes of cluster destruction to form the [X(2)MYH(2)](2) dimers. The high stability of the [HMNH](6) clusters makes them attractive single-source precursors for the production of 13-15 composites.