Multiple Bonding Between Group†3 Metals and Fe(CO)3.

Heteronuclear Group 3 metal/iron carbonyl anion complexes ScFe(CO)3 - , YFe(CO)3 - , and LaFe(CO)3 - are prepared in the gas phase and studied by mass-selective infrared (IR) photodissociation spectroscopy as well as quantum-chemical calculations. All three anion complexes are characterized to have a metal-metal-bonded C3v equilibrium geometry with all three carbonyl ligands bonded to the iron center and a closed-shell singlet electronic ground state. Bonding analyses reveal that there are multiple bonding interactions between the bare group-3 elements and the Fe(CO)3 - fragment. Besides one covalent electron-sharing metal-metal σ bond and two dative π bonds from Fe to the Group 3 metal, there is additional multicenter covalent bonding with the Group 3 atom bonded to Fe and the carbon atoms.

Quadruple bonding between iron and boron in the BFe(CO)3- complex.

While main group elements have four valence orbitals accessible for bonding, quadruple bonding to main group elements is extremely rare. Here we report that main group element boron is able to form quadruple bonding interactions with iron in the BFe(CO)3- anion complex, which has been revealed by quantum chemical investigation and identified by mass-selected infrared photodissociation spectroscopy in the gas phase. The complex is characterized to have a B-Fe(CO)3- structure of C3v symmetry and features a B-Fe bond distance that is much shorter than that expected for a triple bond. Various chemical bonding analyses indicate that the complex involves unprecedented B≣Fe quadruple bonding interactions. Besides the common one electron-sharing σ bond and two Fe→B dative π bonds, there is an additional weak B→Fe dative σ bonding interaction. This finding of the new quadruple bonding indicates that there might exist a wide range of boron-metal complexes that contain such high multiplicity of chemical bonds.

Octacarbonyl Ion Complexes of Actinides [An(CO)8 ]+/- (An=Th, U) and the Role of f Orbitals in Metal-Ligand Bonding.

The octacarbonyl cation and anion complexes of actinide metals [An(CO)8 ]+/- (An=Th, U) are prepared in the gas phase and are studied by mass-selected infrared photodissociation spectroscopy. Both the octacarbonyl cations and anions have been characterized to be saturated coordinated complexes. Quantum chemical calculations by using density functional theory show that the [Th(CO)8 ]+ and [Th(CO)8 ]- complexes have a distorted octahedral (D4h ) equilibrium geometry and a doublet electronic ground state. Both the [U(CO)8 ]+ cation and the [U(CO)8 ]- anion exhibit cubic structures (Oh ) with a 6 A1g ground state for the cation and a 4 A1g ground state for the anion. The neutral species [Th(CO)8 ] (Oh ; 1 A1g ) and [U(CO)8 ] (D4h ; 5 B1u ) have also been calculated. Analysis of their electronic structures with the help on an energy decomposition method reveals that, along with the dominating 6d valence orbitals, there are significant 5f orbital participation in both the [An]←CO σ donation and [An]→CO π back donation interactions in the cations and anions, for which the electronic reference state of An has both occupied and vacant 5f AOs. The trend of the valence orbital contribution to the metal-CO bonds has the order of 6d≫5f>7s≈7p, with the 5f orbitals of uranium being more important than the 5f orbitals of thorium.

Triple bonds between iron and heavier group-14 elements in the AFe(CO)3- complexes (A = Ge, Sn, and Pb).

Heteronuclear transition-metal-main-group element carbonyl anion complexes of AFe(CO)3- (A = Ge, Sn, and Pb) are prepared using a laser vaporization supersonic ion source in the gas phase, which were studied by mass-selected infrared (IR) photodissociation spectroscopy. The geometric and electronic structures of the experimentally observed species are identified by a comparison of the measured and calculated IR spectra. These anion complexes have a 2A1 doublet electronic ground state and feature an A[triple bond, length as m-dash]Fe triply bonded C3v structure with all of the carbonyl ligands bonded at the iron center. Bonding analyses of AFe(CO)3- (A = C, Si, Ge, Sn, Pb, and Fl) indicate that the complexes are triply bonded between the valence np atomic orbitals of bare group-14 atoms and the hybridized 3d and 4p atomic orbitals of iron.

Alkali Metal Covalent Bonding in Nickel Carbonyl Complexes ENi(CO)3.

The alkali metal-nickel carbonyl anions ENi(CO)3 - with E=Li, Na, K, Rb, Cs have been produced and characterized by mass-selected infrared photodissociation spectroscopy in the gas phase. The molecules are the first examples of 18-electron transition metal complexes with alkali atoms as covalently bonded ligands. The calculated equilibrium structures possess C3v geometry, where the alkali atom is located above a nearly planar Ni(CO)3 - fragment. The analysis of the electronic structure reveals a peculiar bonding situation where the alkali atom is covalently bonded not only to Ni but also to the carbon atoms.

Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3- (A=As, Sb, Bi) Complexes.

Heteronuclear transition-metal-main-group-element carbonyl complexes of AsFe(CO)3- , SbFe(CO)3- , and BiFe(CO)3- were produced by a laser vaporization supersonic ion source in the gas phase, and were studied by mass-selected IR photodissociation spectroscopy and advanced quantum chemistry methods. These complexes have C3v structures with all of the carbonyl ligands bonded on the iron center, and feature covalent triple bonds between bare Group 15 elements and Fe(CO)3- . Chemical bonding analyses on the whole series of AFe(CO)3- (A=N, P, As, Sb, Bi, Mc) complexes indicate that the valence orbitals involved in the triple bonds are hybridized 3d and 4p atomic orbitals of iron, leading to an unusual (dp-p) type of transition-metal-main-group-element multiple bonding. The σ-type three-orbital interaction between Fe 3d/4p and Group 15 np valence orbitals plays an important role in the bonding and stability of the heavier AFe(CO)3- (A=As, Sb, Bi) complexes.

CO Oxidation by Group 3 Metal Monoxide Cations Supported on [Fe(CO)4 ]2.

Infrared photodissociation spectroscopy of mass-selected heteronuclear cluster anions in the form of OMFe(CO)5- (M=Sc, Y, La) indicates that all these anions involve an 18-electron [Fe(CO)4 ]2- building block that is bonded with the M center through two bridged carbonyl ligands. The OLaFe(CO)5- anion is determined to be a CO-tagged complex involving a [Fe(CO)4 ]2- [LaO]+ anion core. In contrast, the OYFe(CO)5- anion is characterized to have a [Fe(CO)4 ]2- [Y(η2 -CO2 )]+ structure involving a side-on bonded CO2 ligand. The CO-tagged complex and the [Fe(CO)4 ]2- [Sc(η2 -CO2 )]+ isomer co-exist for the OScFe(CO)5- anion. These observations indicate that both the ScO+ and YO+ cations supported on [Fe(CO)4 ]2- are able to oxidize CO to CO2 . Theoretical analyses show that [Fe(CO)4 ]2- coordination significantly weakens the MO+ bond and decreases the energy gap of the interacting valence orbitals between MO+ and CO, leading to the CO oxidation reactions being both thermodynamically exothermic and kinetically facile.

Preparation and Characterization of Uranium-Iron Triple-Bonded UFe(CO)3- and OUFe(CO)3- Complexes.

We report the preparation of UFe(CO)3- and OUFe(CO)3- complexes using a laser-vaporization supersonic ion source in the gas phase. These compounds were mass-selected and characterized by infrared photodissociation spectroscopy and state-of-the-art quantum chemical studies. There are unprecedented triple bonds between U 6d/5f and Fe 3d orbitals, featuring one covalent σ bond and two Fe-to-U dative π bonds in both complexes. The uranium and iron elements are found to exist in unique formal U(I or III) and Fe(-II) oxidation states, respectively. These findings suggest that there may exist a whole family of stable df-d multiple-bonded f-element-transition-metal compounds that have not been fully recognized to date.

Observation of Spontaneous C=C Bond Breaking in the Reaction between Atomic Boron and Ethylene in Solid Neon.

A ground-state boron atom inserts into the C=C bond of ethylene to spontaneously form the allene-like compound H2 CBCH2 on annealing in solid neon. This compound can further isomerize to the propyne-like HCBCH3 isomer under UV light excitation. The observation of this unique spontaneous C=C bond insertion reaction is consistent with theoretical predictions that the reaction is thermodynamically exothermic and kinetically facile. This work demonstrates that the stronger C=C bond, rather than the less inert C-H bond, can be broken to form organoboron species from the reaction of a boron atom with ethylene even at cryogenic temperatures.

UTSA-74: A MOF-74 Isomer with Two Accessible Binding Sites per Metal Center for Highly Selective Gas Separation.

A new metal-organic framework Zn2(H2O)(dobdc)·0.5(H2O) (UTSA-74, H4dobdc = 2,5-dioxido-1,4-benzenedicarboxylic acid), Zn-MOF-74/CPO-27-Zn isomer, has been synthesized and structurally characterized. It has a novel four coordinated fgl topology with one-dimensional channels of about 8.0 Å. Unlike metal sites in the well-established MOF-74 with a rod-packing structure in which each of them is in a five coordinate square pyramidal coordination geometry, there are two different Zn(2+) sites within the binuclear secondary building units in UTSA-74 in which one of them (Zn1) is in a tetrahedral while another (Zn2) in an octahedral coordination geometry. After activation, the two axial water molecules on Zn2 sites can be removed, generating UTSA-74a with two accessible gas binding sites per Zn2 ion. Accordingly, UTSA-74a takes up a moderately high and comparable amount of acetylene (145 cm(3)/cm(3)) to Zn-MOF-74. Interestingly, the accessible Zn(2+) sites in UTSA-74a are bridged by carbon dioxide molecules instead of being terminally bound in Zn-MOF-74, so UTSA-74a adsorbs a much smaller amount of carbon dioxide (90 cm(3)/cm(3)) than Zn-MOF-74 (146 cm(3)/cm(3)) at room temperature and 1 bar, leading to a superior MOF material for highly selective C2H2/CO2 separation. X-ray crystal structures, gas sorption isotherms, molecular modeling, and simulated and experimental breakthroughs comprehensively support this result.

Infrared photodissociation spectroscopy of mass-selected heteronuclear iron-copper carbonyl cluster anions in the gas phase.

Mass-selected heteronuclear iron-copper carbonyl cluster anions CuFe(CO)n(-) (n = 4-7) are studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region in the gas phase. The cluster anions are produced via a laser vaporization supersonic cluster ion source. Their geometric structures are determined by comparison of the experimental spectra with those calculated by density functional theory. The experimentally observed CuFe(CO)n(-) (n = 4-7) cluster anions are characterized to have (OC)4Fe-Cu(CO)n-4 structures, each involving a C3v symmetry Fe(CO)4(-) building block. Bonding analysis indicates that the Fe-Cu bond in the CuFe(CO)n(-) (n = 4-7) cluster anions is a σ type single bond with the iron center possessing the most favored 18-electron configuration. The results provide important new insight into the structure and bonding of hetronuclear transition metal carbonyl cluster anions.

Exceptional temperature-dependent coordination sites from acylamide groups.

Herein, through altering the reaction temperature, the coordination mode of the acylamide ligand is well controlled with or without the oxygen coordination site. The resulting two new coordination polymers have the formulas Cd3(L)2(bdc)3·4(H2O) (1) and Cd(L)(bdc)·2(H2O) (2) (L = N(1),N(4)-bis(pyridin-3-ylmethyl)terephthalamide, H2bdc = terephthalic acid).

Extractive electrospray ionization mass spectrometry for uranium chemistry studies.

Uranium chemistry is of sustainable interest. Breakthroughs in uranium studies make serious impacts in many fields including chemistry, physics, energy and biology, because uranium plays fundamentally important roles in these fields. Substantial progress in uranium studies normally requires development of novel analytical tools. Extractive electrospray ionization mass spectrometry (EESI-MS) is a sensitive technique for trace detection of various analytes in complex matrices without sample pretreatment. EESI-MS shows excellent performance for monitoring uranium species in various samples at trace levels since it tolerates extremely complex matrices. Therefore, EESI-MS is an alternative choice for studying uranium chemistry, especially when it combines ion trap mass spectrometry. In this presentation, three examples of EESI-MS for uranium chemistry studies will be given, illustrating the potential applications of EESI-MS in synthesis chemistry, physical chemistry, and analytical chemistry of uranium. More specifically, case studies on EESI-MS for synthesis and characterization of novel uranium species, and for rapid detection of uranium and its isotope ratios in various samples will be presented. Novel methods based on EESI-MS for screening uranium ores and radioactive iodine-129 will be presented.

Optimization of reaction conditions towards multiple types of framework isomers and periodic-increased porosity: luminescence properties and selective CO2 adsorption over N2.

Three new metal-organic frameworks (MOFs) were prepared by solvo(hydro)thermolysis and further characterized as framework isomers. The structural transformation from non-porous to porous MOFs and the purity of these products can be modulated by controlling the reaction temperature. The periodic-increased porosity observed was further confirmed by CO2 adsorption isotherms. Owing to the presence of acylamide groups in the pore walls and the flexible nature of the skeleton of these MOFs, highly selective CO2 adsorption over N2 was observed, as well as structure-dependent periodic varieties in luminescence properties.

Framework isomers controlled by the speed of crystallization: different aggregation fashions of Zn(II) and 1,2,4-triazol-3-amine, distinct (3,4)-connected self-penetrating nets, and various pore shapes.

In this work, we report two exceptional framework isomers, Zn(L)(bdc)(0.5)·0.25H2O (1, HL = 1,2,4-triazol-3-amine, H2bdc = terephthalic acid) and Zn(L)(bdc)(0.5)·0.17H2O (2), where their formation is controlled by different speeds of crystallization. Further structural studies reveal that this operation of controlling the speed of crystallization may play a profound role in determining the aggregation fashions of Zn(II) ions and L(-) ligands, resulting in the various layers, viz. a 4·8(2) net vs. a 4·6·12 net. Importantly, this work also presents two previously unobserved (3,4)-connected self-penetrating matrixes.

Solvent-induced reversible single-crystal-to-single-crystal transformations observed in lanthanide complexes.

In this work, a rare 0D→0D single-crystal-to-single-crystal transformation (SCSC) is observed in lanthanide compounds, which is triggered by the removal or retake of solvent molecules. This advantage prompted us to explore the magnetic property of them, and some interesting magnetic properties are obtained.

A microporous metal-organic framework containing an exceptional four-connecting 4(2)6(4) topology and a combined effect for highly selective adsorption of CO2 over N2.

Reported here is a new microporous metal-organic framework, namely [Zn(2)(L)(btc)(Hbtc)] [NH(2)(CH(3))(2)]·(DMF)(2)(H(2)O)(4) (1), which is synthesized solvo(hydro)thermally by the self-assembly of Zn(NO(3))(2), N(4),N(4)-di(pyridin-3-yl)-[1,1'-biphenyl]-4,4'-dicarboxamide (L) and 1,3,5-benzenetricarboxylate acid (H(3)btc). Its topology can be described as a four-connecting 4(2)6(4) matrix containing both tetrahedral metal and ligand nodes. Interestingly, such a matrix has the same topology symbol as that observed in the well known sodalite (SOD) net, but the td10 of 434 is different from the td10 of 791 for the SOD net, indicative of an exceptional four-connecting 4(2)6(4) net. Another outstanding point is the highly selective adsorption of CO(2) over N(2), possibly contributed by a combined effect from the charged skeleton, the existence of functional groups of -CONH- and -COOH in 1.

Solvent-induced supramolecular isomers, structural diversity, and unprecedented in situ formation of both inorganic and organic ions in inorganic-organic mercury(II) complexes.

Reported here is, for the first time, an important study of solvent effect on structural diversity in inorganic-organic mercury(II) complexes. As a result, the first supramolecular isomer in mercury(II) complexes is obtained. Importantly, a previously unobserved in situ generation of both inorganic (Cl(-)) and organic ([CH(3)-L1-CH(3)](2+)) ions was also observed.

A self-catenated network containing unprecedented 0D + 2D → 2D polycatenation array.

Herein, we report a new acylamide ligand and its application in the construction of a metal-organic framework. The resultant acylamide metal-organic framework, namely [Zn(2)(L)(OH)(btc)](n) (1, L = N(1),N(4)-bis(pyridin-3-ylmethyl) naphthalene-1,4-dicarboxamide, H(3)btc = benzene-1,3,5-tricarboxylic acid), was obtained by hydrothermal synthesis. The outstanding structural feature of it is the 0D + 2D → 2D polycatenation array containing a self-catenated feature which has never previously been observed. To the best of our knowledge, the coexistence of self-catenation and polycatenation phenomena is highly exceptional.

Functionalizing the pore wall of chiral porous metal-organic frameworks by distinct -H, -OH, -NH2, -NO2, -COOH shutters showing selective adsorption of CO2, tunable photoluminescence, and direct white-light emission.

This work presents a prototype of chiral porous metal-organic framework with the porous wall decorated by different functional groups. The special structure in conjunction with the gas adsorption results reveals some relationship between CO2 adsorption and functional points. Moreover, outstanding tunable photoluminescence and direct white-light emission is observed.