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Highly Coordinated Heteronuclear Calcium-Iron Carbonyl Cation Complexes [CaFe(CO)_n ]⁺ (n=5-12) with d-d Bonding.

ABSTRACT: Heteronuclear calcium-iron carbonyl cation complexes in the form of [CaFe(CO)_n ]⁺ (n=5-12) are produced in the gas phase. Infrared photodissociation spectroscopy in conjunction with quantum chemical calculations confirm that the n=10 complex is the coordination saturated ion where a Fe(CO)₄ fragment is bonded with a Ca(CO)₆ fragment through two side-on bridging carbonyl ligands. Bonding analysis indicates that it is best described by the bonding interactions between a [Ca(CO)₆ ]²⁺ dication and an [Fe(CO)₄ ]^- anion forming a Fe→Ca d-d dative bond in the [(CO)₆ Ca-Fe(CO)₄ ]⁺ structure, which enriches the pool of experimentally observed complexes of calcium that mimic transition metal compounds. The molecule is the first example of a heteronuclear carbonyl complex featuring a d-d bond between calcium and a transition metal.

SUBMITTER: Jin X

PROVIDER: S-EPMC8251804 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Chemical Bonding in Homoleptic Carbonyl Cations [M{Fe(CO)5 }2 ]+ (M=Cu, Ag, Au).

Project description:Syntheses of the copper and gold complexes [Cu{Fe(CO)5 }2 ][SbF6 ] and [Au{Fe(CO)5 }2 ][HOB{3,5-(CF3 )2 C6 H3 }3 ] containing the homoleptic carbonyl cations [M{Fe(CO)5 }2 ]+ (M=Cu, Au) are reported. Structural data of the rare, trimetallic Cu2 Fe, Ag2 Fe and Au2 Fe complexes [Cu{Fe(CO)5 }2 ][SbF6 ], [Ag{Fe(CO)5 }2 ][SbF6 ] and [Au{Fe(CO)5 }2 ][HOB{3,5-(CF3 )2 C6 H3 }3 ] are also given. The silver and gold cations [M{Fe(CO)5 }2 ]+ (M=Ag, Au) possess a nearly linear Fe-M-Fe' moiety but the Fe-Cu-Fe' in [Cu{Fe(CO)5 }2 ][SbF6 ] exhibits a significant bending angle of 147° due to the strong interaction with the [SbF6 ]- anion. The Fe(CO)5 ligands adopt a distorted square-pyramidal geometry in the cations [M{Fe(CO)5 }2 ]+ , with the basal CO groups inclined towards M. The geometry optimization with DFT methods of the cations [M{Fe(CO)5 }2 ]+ (M=Cu, Ag, Au) gives equilibrium structures with linear Fe-M-Fe' fragments and D2 symmetry for the copper and silver cations and D4d symmetry for the gold cation. There is nearly free rotation of the Fe(CO)5 ligands around the Fe-M-Fe' axis. The calculated bond dissociation energies for the loss of both Fe(CO)5 ligands from the cations [M{Fe(CO)5 }2 ]+ show the order M=Au (De =137.2 kcal mol-1 )>Cu (De =109.0 kcal mol-1 )>Ag (De =92.4 kcal mol-1 ). The QTAIM analysis shows bond paths and bond critical points for the M-Fe linkage but not between M and the CO ligands. The EDA-NOCV calculations suggest that the [Fe(CO)5 ]→M+ ←[Fe(CO)5 ] donation is significantly stronger than the [Fe(CO)5 ]←M+ →[Fe(CO)5 ] backdonation. Inspection of the pairwise orbital interactions identifies four contributions for the charge donation of the Fe(CO)5 ligands into the vacant (n)s and (n)p AOs of M+ and five components for the backdonation from the occupied (n-1)d AOs of M+ into vacant ligand orbitals.

| S-EPMC8252735 | biostudies-literature

Formation and Reactivity of a Hexahydridosilicate [SiH6 ]2- Coordinated by a Macrocycle-Supported Strontium Cation.

Project description:The cationic benzyl complex [(Me4 TACD)Sr(CH2 Ph)][A] (Me4 TACD=1,4,7,10-tetramethyltetraazacyclododecane; A=B(C6 H3 -3,5-Me2 )4 ) reacted with two equivalents of phenylsilane to give the bridging hexahydridosilicate complex [(Me4 TACD)2 Sr2 (thf)4 (μ-κ3 : κ3 -SiH6 )][A]2 (3 a). Rapid phenyl exchange between phenylsilane molecules is assumed to generate monosilane SiH4 that is trapped by two strontium hydride cations [(Me4 TACD)SrH(thf)x ]+ . Complex 3 a decomposed in THF at room temperature to give the terminal silanide complex [(Me4 TACD)Sr(SiH3 )(thf)2 ][A], with release of H2 . Upon reaction with a weak Brønsted acid, CO2 , and 1,3,5,7-cyclooctatetraene SiH4 was released. The reaction of a 1 : 2 mixture of cationic benzyl and neutral dibenzyl complex with phenylsilane gave the trinuclear silanide complex [(Me4 TACD)3 Sr3 (μ2 -H)3 (μ3 -SiH3 )2 ][A], while n OctSiH3 led to the trinuclear (n-octyl)pentahydridosilicate complex [(Me4 TACD)3 Sr3 (μ2 -H)3 (μ3 -SiH5 n Oct)][A].

| S-EPMC9303417 | biostudies-literature

The Impact of Cr3+ Doping on Temperature Sensitivity Modulation in Cr3+ Doped and Cr3+, Nd3+ Co-doped Y3Al5O12, Y3Al2Ga3O12, and Y3Ga5O12 Nanothermometers.

Project description:A new approach to enhance the sensitivity of transition metal ion based nanocrystalline luminescent thermometer is presented. It was shown that the increase of Cr3+ concentration in three types of garnet host namely Y3Al5O12, Y3Ga5O12, and Y3Al2Ga3O12 allows for significant enhancement of their performance in non-contact thermometry. This phenomenon is related to the weakening of the crystal field strength due to enlargement of average Cr3+-O2- distance at higher Cr3+ concentrations. By increasing Cr3+ concentration from 0.6 to 30%, the sensitivity increased by over one order of magnitude from S = 0.2%/°C to S = 2.2%/°C at 9°C in Y3Al2Ga3O12 nanocrystals. Moreover, it was found that due to the Cr3+ ? Nd3+ energy transfer in the Cr3+, Nd3+ co-doped system, the usable Cr3+ concentration, for which its emission can be detected, is limited to 10% while the sensitivity at -50°C was doubled (from 1.3%/°C for Y3Al2Ga3O12:10%Cr3+ to 2.2%/°C Y3Al2Ga3O12:10%Cr3+, 1%Nd3+ nanocrystals).

| S-EPMC6157326 | biostudies-literature

Stabilization of hydrated AcIII cation: the role of superatom states in actinium-water bonding.

Project description:225Ac-based radiopharmaceuticals have the potential to become invaluable in designated cancer therapy. However, the limited understanding of the solution chemistry and bonding properties of actinium has hindered the development of existing and emerging targeted radiotherapeutics, which also poses a significant challenge in the discovery of new agents. Herein, we report the geometric and electronic structural properties of hydrated AcIII cations in the [AcIII(H2O) n ]3+ (n = 4-11) complexes in aqueous solution and gas-phase using density functional theory. We found that nine water molecules coordinated to the AcIII cation is the most stable complex due to an enhanced hydration Gibbs free energy. This complex adopts a closed-shell 18-electron configuration (1S 21P 61D 10) of a superatom state, which indicates a non-negligible covalent character and involves H2O → AcIII σ donation interaction between s-/p-/d-type atomic orbitals of the Ac atom and 2p atomic orbitals of the O atoms. Furthermore, potentially existing 10-coordinated complexes need to overcome an energy barrier (>0.10 eV) caused by hydrogen bonding to convert to 9-coordination. These results imply the importance of superatom states in actinide chemistry generally, and specifically in AcIII solution chemistry, and highlight the conversion mechanism between different coordination numbers.

| S-EPMC8179294 | biostudies-literature

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

Project description: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 ? bond and two Fe?B dative ? bonds, there is an additional weak B?Fe dative ? 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.

| S-EPMC6797760 | biostudies-literature

Chemical Bonding and σ-Aromaticity in Charged Molecular Alloys: [Pd2As14]4- and [Au2Sb14]4- Clusters.

Project description:We report a computational study on the structures and bonding of a charged molecular alloy D 2h [Pd2As14]4- (1), as well as a model D 2h [Au2Sb14]4- (2) cluster. Our effort makes use of an array of quantum chemistry tools: canonical molecular orbital analysis, adaptive natural density partitioning, natural bond orbital analysis, orbital composition analysis, and nucleus independent chemical shift calculations. Both clusters consist of two X7 (X = As, Sb) cages, which are interconnected via a M2 (M = Pd, Au) dumbbell, featuring two distorted square-planar MX4 units. Excluding the Pd/As or Au/Sb lone-pairs, clusters 1 and 2 are 50- and 44-electron systems, respectively, of which 32 electrons are for two-center two-electron (2c-2e) As-As or Sb-Sb σ bonds and an additional 16 electrons in 1 for 2c-2e Pd-As σ bonds. No covalent Pd-Pd or Au-Au bond is present in the systems. Cluster 1 is shown to possess two globally delocalized σ electrons, whereas 2 has two σ sextets (each associated with an AuSb4 fragment). Thus, 1 and 2 conform to the (4n + 2) Hückel rule, for n = 0 and 1, respectively, rendering them σ-aromaticity.

| S-EPMC5429782 | biostudies-literature

Chemical Bonding in Transition Metal Nitride Os3N3 + Cluster: 6π Inorganic Benzene and δ2δ*1δ*1 Aromaticity.

Project description:Inorganic benzene-like clusters with a planar hexagonal ring are of interest in chemistry, as are new types of aromaticity, multifold aromaticity, and in particular δ aromaticity beyond carbon-based organic systems. Here we report on a computational study of chemical bonding in a binary Os3N3 + D 3h (7A2″) cluster. This transition metal nitride cluster assumes a perfectly planar, heteroatomic, hexagonal geometry. An array of quantum chemistry tools is exploited to elucidate the electronic, structural, and bonding properties of D 3h Os3N3 + cluster, which include canonical molecular orbitals, adaptive natural density partitioning, natural bond orbital analysis, orbital composition calculations, and nucleus-independent chemical shifts. The computational data collectively support the bonding picture of 2-fold π/δ aromaticity: 6π electrons delocalized over all Os/N centers versus an Os-based 4δ framework in the unique δ2δ*1δ*1 configuration. The π sextet renders this heteroatomic cluster an inorganic analog of benzene. Transition metal-based inorganic benzenes are unknown in the literature, to our knowledge. The triplet 4δ electron-counting is a rare case of d-orbital aromaticity and δ-aromaticity, following the reversed 4n Hückel rule for aromaticity in a triplet system. This bonding picture is concrete, differing fundamentally from a recent study on the relevant system.

| S-EPMC6643571 | biostudies-literature

Rapid one-pot radiosynthesis of [carbonyl-11C]formamides from primary amines and [11C]CO2.

Project description:BackgroundFormamides are common motifs of biologically-active compounds (e.g. formylated peptides) and are frequently employed as intermediates to yield a number of other functional groups. A rapid, simple and reliable route to [carbonyl-11C]formamides would enable access to this important class of compounds as in vivo PET imaging agents.ResultsA novel radiolabelling strategy for the synthesis of carbon-11 radiolabelled formamides ([11C]formamides) is presented. The reaction proceeded with the conversion of a primary amine to the corresponding [11C]isocyanate using cyclotron-produced [11C]CO2, a phosphazene base (2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine, BEMP) and phosphoryl chloride (POCl3). The [11C]isocyanate was subsequently reduced to [11C]formamide using sodium borohydride (NaBH4). [11C]Benzyl formamide was obtained with a radiochemical yield (RCY) of 80% in 15?min from end of cyclotron target bombardment and with an activity yield of 12%. This novel method was applied to the radiolabeling of aromatic and aliphatic formamides and the chemotactic amino acid [11C]formyl methionine (RCY?=?48%).ConclusionsThis study demonstrates the feasibility of 11C-formylation of primary amines with the primary synthon [11C]CO2. The reactivity is proportional to the nucleophilicity of the precursor amine. This novel method can be used for the production of biomolecules containing a radiolabelled formyl group.

| S-EPMC7462944 | biostudies-literature

Electronic Structure and Chemical Bonding of [AmO2(H2O) n ]2+/1.

Project description:Systematic americyl-hydration cations were investigated theoretically to understand the electronic structures and bonding in [(AmO2)(H2O) n ]2+/1+ (n = 1-6). We obtained the binding energy using density functional theory methods with scalar relativistic and spin-orbit coupling effects. The geometric structures of these species have been investigated in aqueous solution via an implicit solvation model. Computational results reveal that the complexes of five equatorial water molecules coordinated to americyl ions are the most stable due to the enhanced ionic interactions between the AmO2 2+/1+ cation and multiple oxygen atoms as electron donors. As expected, Am-Owater bonds in such series are electrostatic in nature and contain a generally decreasing covalent character when hydration number increases.

| S-EPMC6644428 | biostudies-literature

Chemical Bonding in Silicon Carbonyl Complexes.

Project description:Although silylene-carbonyl complexes are known for decades, only recently isolable examples have been accomplished. In this work, the bonding situation is re-evaluated to explain the origins of their remarkable stability within the Kohn-Sham molecular orbital theory framework. It is shown that the chemical bond can be understood as CO interaction with the silylene via a donor-acceptor interaction: a σ-donation from the σCO into the empty p-orbital of silicon, and a π-back donation from the sp2 lone pair of silicon into the π*CO antibonding orbitals. Notably, it was established that the driving force behind the surprisingly stable Si-CO compounds, however, is another π-back donation from a perpendicular bonding R-Si σ-orbital into the π*CO antibonding orbitals. Consequently, the pyramidalization of the central silicon atom cannot be associated with the strength of the π-back donation, in sharp contrast to the established chemical bonding model. Considering this additional bonding interaction not only shed light on the bonding situation, but is also an indispensable key for broadening the scope of silylene-carbonyl chemistry.

| S-EPMC8360033 | biostudies-literature