Transition Metal Bis Research Articles

Nature of metal–bis(β-diketonate) bonds in TM(acac’)2 (acac’ = acetylacetonate, hexafluoroacetylacetonate, hexamethylacetylacetonate; TM = Ni(II), Pd(II), Pt(II)) complexes: A density functional theory investigation

This computational study investigates the structural and bonding aspects of transition metal bis(β-diketonate) complexes, TM(acac’)2 (acac’ = acetylacetonate, hexafluoroacetylacetonate, hexamethylacetylacetonate; TM = Ni(II), Pd(II), Pt(II)), at BP86/def2-TZVP and M06/def2-TZVP levels of theory. Patterns observed in both computed interaction and stabilisation energies demonstrate an increasing in the order of hexafluoroacetylacetonate < hexamethylacetylacetonate < acetylacetonate. A comprehensive energy decomposition analysis (EDA) was performed to thoroughly examine the attributes of the bonds between the metal and ligands within complexes. According to the EDA results, it is evident that electrostatic interactions exert a greater influence on shaping the overall attractive interactions compared to orbital interactions. However, the significance of the b1g orbitals cannot be overstated, as they contribute more than 41% across all complexes. Additionally, the backdonation processes TM→Lσ and TM→Lπ exhibit notable weaknesses.

Bis(Dicarbollide) Complexes of Transition Metals: How Substituents in Dicarbollide Ligands Affect the Geometry and Properties of the Complexes.

The interaction between different types of substituents in dicarbollide ligands and their influence on the stabilization of various rotational conformers (rotamers) of transition metal bis(dicarbollide) complexes [3,3'-M(1,2-C2B9H11)2]- are considered. It has been shown that the formation of intramolecular CH···X hydrogen bonds between dicarbollide ligands is determined by the size of the proton acceptor atom X rather than its electronegativity. Due to the stabilization of rotamers with different dipole moments, intramolecular hydrogen bonds between ligands in transition metal bis(dicarbollide) complexes can have a significant impact on the biological properties of their derivatives. In the presence of external complexing metals, weak intramolecular CH···X hydrogen bonds can be broken to form stronger X->M donor-acceptor bonds. This process is accompanied by the mutual rotation of dicarbollide ligands and can be used in sensors and molecular switches based on transition metal bis(dicarbollide) complexes.

Copper (II) and cobalt (II) bis(hexafluoroacetylacetonate) coordination complexes with N-styrylbenzimidazole

The study considers metal complexes based on N-styrylbenzimidazole as compounds having significant pharmacological properties The work is aimed at examining the crystal structure and electronic structure of transition metal bis(hexafluoroacetylacetonate) complexes (copper (II) (complex A) and cobalt (II) (complex B)) with N-styrylbenzimidazole using X-ray diffraction analysis and ultraviolet spectroscopy. The X-ray diffraction analysis was used to prove bipyramidal coordination in copper (II) and cobalt (II) bis(hexafluoroacetylacetonate) complexes with N-styrylbenzimidazole. The atoms of copper (II) and cobalt (II) in the complexes exhibit an unusual for β-diketonate complexes distorted square-planar coordination, while the chelate cycles in M(hfacac)2L are characterized by anomalously large kink angles. Thus, for the copper (II) bis(hexafluoroacetylacetonate) complex, the kink angle of the O3∙∙∙O4 interaction for the equatorially positioned ligand is 29.47°, while for the axially positioned ligand, the kink angle of the O1∙∙∙O2 interaction is 19.13°. For the cobalt (II) bis(hexafluoroacetylacetonate) complex, these angles are 22.10 and 19.50°, respectively. Electron spectroscopy was used to examine the electronic structure of the specified complexes. The following types of electronic transitions were identified: π→π*-transitions primarily localized on ligands, as well as transitions caused by electron transfer from the p-orbital of the hetero nitrogen atom of the styrylbenzimidazole cycle to the d-orbital of metal ions, and n→π transition localized on the imidazole ring. For each of the complexes, d-d* transitions between the molecular orbitals of the corresponding metal ion were localized in the long wavelength part of the spectrum.

CdS nanorods decorated with non-precious metal Bi spheres for photocatalytic hydrogen production

It is well known that precious metals decoration strategies can effectively improve the charge separation efficiency. Unfortunately, the high price limits their large-scale application. Nevertheless, the cheap transition metal Bi has a similar effect as precious metals. Therefore, we take a simple solvothermal method to reduce and aggregate Bi3+ into bismuth nano-spheres (Bi0). CdS nanorods were modified with Bi spheres to create a hybrid material called x% Bi–CdS, which combines a metal and a semiconductor for photocatalytic hydrogen production. The results of the experiment indicate that the hydrogen evolution rate of the 5% Bi–CdS sample is 1501.52 μmol g−1 h−1, which is 4.2 times greater than that of pure CdS nanorods. This significant enhancement in photocatalytic activity can be attributed to the presence of Bi spheres, which induce a surface plasmon resonance (SPR) effect. This effect boosts the absorption of visible light and enhances the separation efficiency of charge carriers. The study not only provides a solution for the preparation of low-cost CdS-based materials, but also confirms the feasibility of inexpensive Bi metals to replace precious metals as co-catalysts to improve the photocatalytic efficiency.

Synthesis, electrical conductivity and NIR absorption of some metal dithiolene complexes: some recent developments

Square planar transition metal bis(dithiolene) complexes are of upsurge interest throughout the last few decades due to its varied interesting physical as well as physicochemical properties. Random studies on design and synthesis of semiconducting materials based on metal dithiolene complexes are going on. Moreover, shift at intense Near Infrared (NIR) region, high electrical conductivity, non-linear optical (NLO) activity, electrochemical behaviors etc. are some of its interesting activities. It is important to note that a minute tailoring in its ligand backbone (which results change in its electron delocalization) results in appreciable amount of variation in its physicochemical behavior. In this present endeavor, research works on synthesis, solid-state electrical conductivity and Near Infrared (NIR) absorption studies of square planar transition metal dithiolene complexes from near past to present days have been discussed with survey of recent work and its futuristic applications so far.

Calcium-stabilised transition metal bis(formyl) complexes: structure and bonding.

Reaction of a molecular calcium hydride with a series of group 9 dicarbonyl complexes [M(η5-C5Me5)(CO)2] (M = Co, Rh, Ir) led to the formation of both mono(formyl) and bis(formyl) complexes. The bis(formyl) complexes are unique. They have been characterised by multinuclear NMR spectroscopy and examples have been crystallographically characterised for the first time.

Ditelluride, Terminal Tellurido, and Bis(tellurido) Motifs of Titanium.

Highly modular and rational syntheses of titanium compounds containing ditelluride, terminal telluride, and bis(telluride) structural motifs are disclosed in this study. Titanate anions bearing two cis and terminal telluride functionalities bound to the same metal center represent a unique example of a group 4 transition metal bis(chalcogenide) ion and are accessed in a simple, single-step procedure from Ti(III) bis(alkyl) complexes in the presence of an outer-sphere reductant and at least 3 equiv of Te0 powder. These compounds have been characterized crystallographically and spectroscopically with some preliminary reactivity reported for the anionic Ti(═Te)2 motif. We also report solution 125Te NMR spectral data in addition to theoretical studies addressing the bonding and structure for these titanate bis(tellurido) systems.

Synthesis, characterization, and alkoxide transfer reactivity of dimeric Tl2(OR)2 complexes.

Reaction of LiOCtBu2Ph with TlPF6 forms the dimeric Tl2(OCtBu2Ph)2 complex, a rare example of a homoleptic thallium alkoxide complex demonstrating formally two-coordinate metal centers. Characterization of Tl2(OCtBu2Ph)2 by 1H and 13C NMR spectroscopy and X-ray crystallography reveals the presence of two isomers differing by the mutual conformation of the alkoxide ligands, and by the planarity of the central Tl-O-Tl-O plane. Tl2(OCtBu2Ph)2 serves as a convenient precursor to the formation of old and new [M(OCtBu2Ph)n] complexes (M = Cr, Fe, Cu, Zn), including a rare example of T-shaped Zn(OCtBu2Ph)2(THF) complex, which could not be previously synthesized using more conventional LiOR/HOR precursors. The reaction of [Ru(cymene)Cl2]2 with Tl2(OCtBu2Ph)2 results in the formation of a ruthenium(ii) alkoxide complex. For ruthenium, the initial coordination of the alkoxide triggers C-H activation at the ortho-H of [OCtBu2Ph] which results in its bidentate coordination. In addition to Tl2(OCtBu2Ph)2, related Tl2(OCtBu2(3,5-Me2C6H3))2 was also synthesized, characterized, and shown to exhibit similar reactivity with iron and ruthenium precursors. Synthetic, structural, and spectroscopic characterizations are presented.

Computationally Directed Discovery of MoBi2.

Incorporating bismuth, the heaviest element stable to radioactive decay, into new materials enables the creation of emergent properties such as permanent magnetism, superconductivity, and nontrivial topology. Understanding the factors that drive Bi reactivity is critical for the realization of these properties. Using pressure as a tunable synthetic vector, we can access unexplored regions of phase space to foster reactivity between elements that do not react under ambient conditions. Furthermore, combining computational and experimental methods for materials discovery at high-pressures provides broader insight into the thermodynamic landscape than can be achieved through experiment alone, informing our understanding of the dominant chemical factors governing structure formation. Herein, we report our combined computational and experimental exploration of the Mo-Bi system, for which no binary intermetallic structures were previously known. Using the ab initio random structure searching (AIRSS) approach, we identified multiple synthetic targets between 0-50 GPa. High-pressure in situ powder X-ray diffraction experiments performed in diamond anvil cells confirmed that Mo-Bi mixtures exhibit rich chemistry upon the application of pressure, including experimental realization of the computationally predicted CuAl2-type MoBi2 structure at 35.8(5) GPa. Electronic structure and phonon dispersion calculations on MoBi2 revealed a correlation between valence electron count and bonding in high-pressure transition metal-Bi structures as well as identified two dynamically stable ambient pressure polymorphs. Our study demonstrates the power of the combined computational-experimental approach in capturing high-pressure reactivity for efficient materials discovery.

Bis(dicarbollide) Complexes of Transition Metals as a Platform for Molecular Switches. Study of Complexation of 8,8'-Bis(methylsulfanyl) Derivatives of Cobalt and Iron Bis(dicarbollides).

Complexation of the 8,8′-bis(methylsulfanyl) derivatives of cobalt and iron bis(dicarbollides) [8,8′-(MeS)2-3,3′-M(1,2-C2B9H10)2]− (M = Co, Fe) with copper, silver, palladium and rhodium leads to the formation of the corresponding chelate complexes, which is accompanied by a transition from the transoid to the cisoid conformation of the bis(dicarbollide) complex. This transition is reversible and can be used in design of coordination-driven molecular switches based on transition metal bis(dicarbollide) complexes. The solid-state structures of {(Ph3P)ClPd[8,8′- (MeS)2-3,3′-Co(1,2-C2B9H10)2-κ2-S,S′]} and {(COD)Rh[8,8′-(MeS)2-3,3′-Co(1,2-C2B9H10)2-κ2-S,S′]} were determined by single crystal X-ray diffraction.

First radical cation salts based on dibenzotetrathiafulvalene (DBTTF) with metallacarborane anions: Synthesis, structure, properties

The new radical cation salts based on transition metal bis(dicarbollides) with dibenzotetrathiafulvalene (DBTTF) donors (DBTTF)[3,3′-Fe(1,2-C2B9H11)2] (1) and (DBTTF)2[3,3′-Cr(1,2-C2B9H11)2] (2) were synthesized and their crystal structures were determined by single crystal X-ray diffractions. The electric conductivity measurements revealed that these compounds are semiconductors at room temperature and the conductivity of (DBTTF)2[3,3′-Cr(1,2-C2B9H11)2] is ~500 times higher than that of its BEDT-TTF analogue.

One-Pot, One-Step Precatalysts through Mechanochemistry

The development and implementation of transition-metal-based precatalysts have played crucial roles in modern organic synthesis. However, while the use of such species greatly improves sustainability, their preparative routes often rely on multiple time-, energy-, and solvent-intensive steps. By leveraging solvent-free mechanochemical synthesis through vibratory ball milling, we report the one-pot, one-step synthesis of a range of first-row transition-metal bis(imino)pyridine complexes, where both the ligand and coordination complex are assembled in situ. Bis(imino)pyridine complexes of the first-row transition metals have an extensive history of application as precatalysts for numerous bond-forming transformations. The method reported herein facilitates access to such species in a time-, solvent-, and space-saving manner which can easily be adapted to any laboratory setting regardless of prior experience with coordination complex synthesis.

Design of molecular switches based on transition metal bis(dicarbollide) complexes

The paper presents a review of the state of the art and prospects for the development of rotary molecular switches based on transition metal bis(dicarbollide) complexes.

First molecular conductors of BPDT-TTF with metallacarborane anions: (BPDT-TTF)[3,3′-Сr(1,2-C2B9H11)2] and (BPDT-TTF)[3,3′-Сo(1,2-C2B9H11)2] – Synthesis, structure, properties

The first molecular conductors based on bis(1,3-propylenedithio)tetrathiafulvalene and transition metal bis(dicarbollides) (BPDT-TTF)[3,3′-Сr(1,2-C2B9H11)2] (1) and (BPDT-TTF)[3,3′-Сo(1,2-C2B9H11)2] (2) were synthesized and their crystal structures were determined by X-ray analysis. The electric conductivity measurements revealed that these compounds are semiconductors at room temperature.

Ferrocene and Transition Metal Bis(Dicarbollides) as Platform for Design of Rotatory Molecular Switches.

Design of rotatory molecular switches based on extremely stable sandwich organometallic complexes ferrocene and bis(dicarbollide) complexes of transition metals is reviewed. The “on”–“off” switching in these systems can be controlled by various external stimuli such as change of the solution pH, interactions with coordinating species or redox reactions involving the central atom or substituents in the ligands.

Novel sulfur containing derivatives of carboranes and metallacarboranes

Abstract A series of new closo- and nido-carborane based functional derivatives 1-X(CH2)nS-1,2-C2B10H11 (X=COOH, N3, CH(NH2)COOH) and [7-X(CH2)nS-7,8-C2B9H11]− (X=COOH, N3, NH2, CH(NH2)COOH) was prepared by alkylation of 1-mercapto-ortho-carborane. Dialkylsulfonium derivatives of nido-carborane 9-R(Me)S-7,8-C2B9H11 and 10-R(Me)S-7,8-C2B9H11 with boron-sulfur bond were prepared by alkylation of the corresponding methyl-carboranyl thioether. New types of intramolecular B–H···X and B–H···π(C≡C) interactions were found in nido-carborane alkylmethyl sulfonium derivatives 9-XCH2S(Me)S-7,8-C2B9H11 and 10-RC≡CCH2S(Me)S-7,8-C2B9H11, respectively. Isomeric methylsulfide derivatives of transition metal bis(dicarbollide) complexes [X,Y-(MeS)2-3,3′-M(1,2-C2B9H10)2]− (M=Co, Fe) were prepared starting from the corresponding methylcarboranyl thioethers. The intramolecular CHcarb···S(Me)S hydrogen bonding between the dicarbollide ligands in cobalt bis(dicarbollide) complexes results in stabilization of definite rotational isomers – transoid in the case of the 8,8′-isomer and gauche in the case of the 4,4′- and 4,7′-isomers.

Transition metal bis iminium complexes: Synthesis, characterization, and electrochemistry. Homogeneous epoxidation of cyclohexene with H2O2 using the oxovanadium complex as catalyst

Transition metal bis iminium complexes: Synthesis, characterization, and electrochemistry. Homogeneous epoxidation of cyclohexene with H2O2 using the oxovanadium complex as catalyst

Tetrathiafulvalene-based radical cation salts with transition metal bis(dicarbollide) anions

Radical cation salts based on derivatives of tetrathiafulvalene and sandwiched transition metal bis(dicarbollide) anions are of great interest in the development of new molecular conducting materials.

High-Resolution Electron Spectroscopy and Rotational Conformers of Group 6 Metal (Cr, Mo, and W) Bis(mesitylene) Sandwich Complexes

Group 6 metal-bis(mesitylene) sandwich complexes are produced by interactions between the laser-vaporized metal atoms and mesitylene vapor in a pulsed molecular beam source, identified by photoionization time-of-flight mass spectrometry, and studied by pulsed-field ionization zero-electron kinetic energy spectroscopy and density functional theory calculations. Although transition metal-bis(arene) sandwich complexes may adopt eclipsed and staggered conformations, the group 6 metal-bis(mesitylene) complexes are determined to be in the eclipsed form. In this form, rotational conformers with methyl group dihedral angles of 0 and 60° are identified for the Cr complex, whereas the 0° rotamer is observed for the Mo and W species. The 0° rotamer is in a C(2v) symmetry with the neutral ground state of (1)A1 and the singly positive charged ion state of (2)A1. The 60° rotamer is in a C(i) symmetry with the neutral ground state of (1)A(g) and the ion state of (2)A(g). Partial conversion of the 60 to 0° rotamer is observed from He to He/Ar supersonic expansion for Cr-bis(mesitylene). The unsuccessful observation of the 60° rotamer for the Mo and W complexes is the result of its complete conversion to the 0° rotamer in both He and He/Ar expansions. The adiabatic ionization energies of the 0° rotamers of the three complexes are in the order of Cr-bis(mesitylene) < W-bis(mesitylene) < Mo-bis(mesitylene), which is different from that of the metal atoms. These metal-bis(mesitylene) complexes have lower ionization energies than the corresponding metal-bis(benzene) and -bis(toluene) species.

ChemInform Abstract: From Coordination Polymers to Hierarchical Self‐Assembled Structures

AbstractReview: 82 refs.