Binuclear Precursors Research Articles

Selective Construction and Structural Transformation of Homogeneous Linear Metalla[4]catenane and Metalla[2]catenane Assemblies.

Although the synthesis of mechanically interlocked molecules has been extensively researched, selectively constructing homogeneous linear [4]catenanes remains a formidable challenge. Here, we selectively constructed a homogeneous linear metalla[4]catenane in a one-step process through the coordination-driven self-assembly of a bidentate benzothiadiazole derivative ligand and a binuclear half-sandwich rhodium precursor. The formation of metalla[4]catenanes was facilitated by cooperative interactions between strong sandwich-type π-π stacking and non-classical hydrogen bonds between the components. Moreover, by modulating the aromatic substituents on the binuclear precursor, two homogeneous metalla[2]catenanes were obtained. The molecular structures of these metallacatenanes were unambiguously characterized by single-crystal X-ray diffraction analysis. Additionally, reversible structural transformation between metal-catenanes and the corresponding metallarectangles could be achieved by altering their concentration, as confirmed by mass spectrometry and NMR spectroscopy studies.

Selective Construction and Structural Transformation of Homogeneous Linear Metalla[4]catenane and Metalla[2]catenane Assemblies

AbstractAlthough the synthesis of mechanically interlocked molecules has been extensively researched, selectively constructing homogeneous linear [4]catenanes remains a formidable challenge. Here, we selectively constructed a homogeneous linear metalla[4]catenane in a one‐step process through the coordination‐driven self‐assembly of a bidentate benzothiadiazole derivative ligand and a binuclear half‐sandwich rhodium precursor. The formation of metalla[4]catenanes was facilitated by cooperative interactions between strong sandwich‐type π‐π stacking and non‐classical hydrogen bonds between the components. Moreover, by modulating the aromatic substituents on the binuclear precursor, two homogeneous metalla[2]catenanes were obtained. The molecular structures of these metallacatenanes were unambiguously characterized by single‐crystal X‐ray diffraction analysis. Additionally, reversible structural transformation between metal‐catenanes and the corresponding metallarectangles could be achieved by altering their concentration, as confirmed by mass spectrometry and NMR spectroscopy studies.

Microwave-Accelerated C,N-Cyclometalation as a Route to Chloro-Bridged Iridium(III) Binuclear Precursors of Phosphorescent Materials: Optimization, Synthesis, and Studies of the Iridium(III) Dimer Behavior in Coordinating Solvents.

We present the results of our research on the use of microwaves as an unconventional heat source for the acceleration of iridium(III) chloro-bridged dimer preparation. The results enabled us to revise and improve known guidelines for the very quick and highly efficient synthesis of iridium(III) dimeric complexes in a very simple isolation manner. According to the developed methodology, the already known dimers containing ligands based on the 2-phenylpyridinato motif, as well as new ones stabilized with functionalized benzo[h]quinolinato and 2-phenoxypyridinato-based ligands, were efficiently synthesized. The scope of the incorporated ligands included compounds equipped with electron-donating (-Me, -OMe, -OPh, -NMe2), electron-withdrawing (-F, -Br, -CF3, -C6F5), and hole-transporting (-NPh2, -C6H4NPh2) groups. The obtained complexes were characterized by NMR, X-ray diffraction, and electrospray ionization mass spectrometry methods, and their behavior was examined in the presence of coordinating solvents such as dimethyl sulfoxide and acetonitrile. Investigation of the interactions between the above-mentioned solvents and dimers enabled us to confirm the ability of the former to cleave μ-chloride bridges, which enriches the knowledge in the field of organometallic chemistry. This knowledge can be particularly useful for the scientists working in the field of iridium-based materials, helping to avoid misinterpretation of the spectroscopic data.

Half-sandwich rhodium and iridium fragments and carboxylate ligands as building blocks for the formation of metallamacrocycles

A series of half-sandwich rhodium and iridium complexes containing carboxylate ligands were synthesized and characterized. Reactions between [Cp∗MCl2]2 (M = Ir or Rh) and 1,3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (L1) gave binuclear complexes 1 and 2 under different conditions. The half-sandwich iridium and rhodium metallamacrocycles complexes 3–5 were constructed in a stepwise manner by the addition of carboxylate ligands (sodium acetate or the conjugate bases of pyrazine-2,3-dicarboxylic acid or 3-(2-pyridyl)acrylic acid) to the solution of the binuclear precursors prepared from the reactions of [Cp∗MCl2]2 (M = Rh or Ir) with linear N,N′-donor ligands (4,4′-bipyridine or trans-1,2-bis(4-pyridyl)ethylene), respectively. The structures of binuclear complexes and tetranuclear macrocycles were confirmed by elemental analysis, IR, 1H NMR spectroscopy and single-crystal X-ray diffraction.

One-dimensional coordination polymers constructed from binuclear 3d–4f nodes and isonicotinato spacer

Three new 1-D coordination polymers, [Co(valpn)Gd(hfac)2(IN)]n (1), [Ni(valpn)Gd(hfac)2(IN)]n (2), and [Ni(valpn)Dy(hfac)2(IN)]n (3), were constructed by connecting {MII(valpn)LnIII(hfac)2} nodes through isonicotinato spacers (IN−), with hexafluoroacetylacetonato being hfac and 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol) (H2valpn) being the Schiff base obtained from the condensation reaction between o-vanillin and 1,3-diaminopropane. The synthetic approach relied on the substitution of the acetate ligands from the binuclear precursors [MII(CH3OH)(valpn)LnIII(hfac)2(CH3COO)] with the isonicotinato ligand. The investigation of the magnetic properties of all compounds showed a ferromagnetic interaction attributed to the intranode exchange interaction between the 3d and 4f metal ions. For compound 3, the AC magnetic measurements indicated a field-induced slow relaxation of the magnetization of the [NiIIDyIII] nodes.

Synthesis of a mononuclear oxidovanadium(V) complex by bridge-splitting of the corresponding binuclear precursor

The mononuclear oxidovanadium(V) complex VO(OEt)L (2), where L2− is the dianion of a diprotic tridentate ONO donor ligand, 2-hydroxyacetophenone-2-aminobenzoylhydrazone (H2L), has been synthesized by oxido-bridge splitting of the corresponding binuclear complex V2O3L2 (1) and structurally characterized by single crystal X-ray diffraction analysis, together with electrochemical and spectral studies. Splitting of the oxido-bridge was effected by refluxing 1 with excess triphenylphosphine in ethanol medium. The crystal structure of 2 is compared with that of the precursor binuclear complex 1.

New heterometallic coordination polymers constructed from 3d–3d′ binuclear nodes

Heterobinuclear [CuIIMnII] and [CuIICoII] cationic complexes can efficiently act as nodes for designing coordination polymers. The crystal structures of two binuclear precursors, [LCuCo(NO3)2] (1) and [LCuMn(NO3)2] (2), have been solved (L2− is the dianion of the Schiff base resulting from the 2 : 1 condensation of 3-methoxysalicyladehyde with 1,3-propanediamine). The nitrato ligands, coordinated to CoII and, respectively, the MnII ions from the precursors, are easily replaced by exo-dentate ligands, resulting in 1-D coordination polymers: 1∞[L(H2O)CuCo(oxy-bbz)]·CH3CN·C2H5OH (3), 1∞[L(H2O)CuCo(2,5-dhtp)]·CH3CN (5) and ∞[L(H2O)CuMn(ox)]·3H2O (6) (oxy-bbz2− = the dianion of 4,4′-oxy-bis(benzoic) acid; 2,5-dhtp2− = the dianion of 2,5-dihydroxy-terephthalic acid; ox2− = the dianion of the oxalic acid). In the case of the [CuMn] node, the interaction with oxy-bbz2− affords a binuclear complex, [LCuMn(oxy-bbz)(H2O)2] (4).

Luminescent Au 3Ag 6 heterononanuclear complex of 1-ethynylcyclopentanol

Reaction of polymeric species (AgC CC 5H 8OH) n (HC CC 5H 8OH = 1-ethynylcyclopentanol) with binuclear precursor [Au 2(μ-dppm) 2](PF 6) 2 (dppm = bis(diphenylphospnino)methane) caused isolation of Au 3Ag 6 heterononanuclear complex [Au 3Ag 6(μ-dppm) 3(μ 3– η 1-C CC 5H 8OH) 6](PF 6) 3. The Au 3Ag 6 (μ 3-C CC 5H 8OH) 6 skeleton exhibits a hexagonal prismatic structure formed by μ 3–η 1-C CC 5H 8OH bound to the Au 3Ag 6 cluster core. The compound is luminescent in both solid state and dichloromethane at both 298 and 77 K with the room temperature lifetimes in microsecond ranges, suggesting an emissive triplet parentage.

The Monomerization of a Binuclear Molybdenum(VI) Dioxo Complex by an Unusual Silylation Reaction

AbstractThe formation of a mononuclear molybdenum(VI) complex [MoO2{O(CH2)2S(CH2)2OH}(OSiButPh2)] (2) derived from its binuclear precursor [MoO2{O(CH2)2S(CH2)2O}]2 (1) by a silylation reaction accompanied by the conversion of methanol to chloromethane is reported.

Supported Re and Mo oxides prepared using binuclear precursors: synthesis and characterization

Rhenium and molybdenum oxomethoxide complexes Re2O3(OMe)6, ReMoO2(MeO)7, and Mo2O2(OMe)8 were used as precursors to prepare highly dispersed mono and bimetallic oxide species supported on the microporous NaY zeolite and mesoporous SiO2 and Al2O3. The prepared materials were characterized by the use of FTIR, NH3-TPD, and H2-TPR techniques. It was shown that, upon loading into microporous zeolite, oxomethoxide complexes loose their ligands so that just metal suboxide cores remains in the intracrystalline voids as the nanosized oxide clusters. The obtained clusters reveals both acidic and redox properties. The maximum amount of NH3 adsorbed per bimetallic species could be used as a characteristic of both availability of acid sites and oxide dispersion. Reducibility of these species depends strongly on both their location in the matrix and the size. The matrix texture also affects the transitions between different valent states of Re and Mo as well as the metal reduction extent.

Design, synthesis, and application of new Ti precursors compatible with Ba and Sr precursors for BST thin film by MOCVD

Design, synthesis, and application of the new Ti precursors [Ti(MPD)(MDOP) 2 and the binuclear precursor D (designated as D due to patent pending) derived from thereof] for MOCVD of TiO 2 thin film are reported. The new Ti precursors are stable in the air and moisture and thermally stable at vaporizing temperature. The deposition rate of TiO 2 films with the new Ti precursor D was much higher than that with Ti(MPD)(tmhd) 2 or with Ti(Opr i ) 2 (tmhd) 2 at 375∼475°C. Therefore, the new Ti precursors are expected to yield BST thin films with constant composition in Ba, Sr, and Ti utilizing the prevalent Ba and Sr precursors and current MOCVD technology It is believed that the high deposition rate of TiO 2 thin film is caused by the weaker bond strength of Ti-MDOP than Ti-tmhd.

A strategy for synthesis of large gold rings

26- and 34-membered rings containing four gold(I) centres are prepared by using a synthetic strategy based on the orienting effects of intramolecular gold⋯gold attractions in binuclear precursors.

The reduction of pentaammine(phenanthroline-2-carboxamido- N)cobalt(III) by titanium(III) and vanadium(II)

Pentaammine(phenanthroline-2-carboxamido- N)cobalt(III) ( I) reacts with Ti 3+(aq.) in two separable steps. The first step involves rapid formation of a binuclear intermediate with Ti 3+ forming a chelate with the carboxamido oxygen and the adjacent ring nitrogen. The rate law is k obs= k 1[Ti 3+]+ k r[H +] where k 1=240±10 and k r=6.7±0.4 M −1 s −1 at 25 °C and I=1.0 M (LiCl). The second reaction involves electron transfer and follows the rate law k obs= a[H +] −1[Ti 3+]+ b[H +] −1 where a=0.0046±0.0005 s −1 and b=(1.3±0.1)x10 −4 M −1 s −1. The first term in the rate law of the second step is assigned to outer-sphere reduction by Ti(OH) 2+ of the binuclear precursor formed in the first reaction. The second term involves intramolecular electron transfer within the conjugate base of the binuclear precursor with k et, estimated as 0.13 s −1. The factors affecting intramolecular electron transfer within Co(III)- and Ru(III)-Ti(III) intermediates are discussed. The reaction of I with V 2+(aq.) also occurs in two distinct reactions. The first reaction follows the same rate law as the analogous Ti 3+ reaction with k 1=2010±100 and k r=600±50 M −1 s −1 at 25 °C, I=1.0 M (LiClO 4). The second reaction is first-order in [V 2+] and independent of [H +] with a second-order rate constant of 0.36 ±0.02 M t̄1 s −1. The latter redox reaction is thought to involve outer-sphere reduction of the binuclear precursor formed in the first step.

Polydecker sandwich complexes

The synthesis of the first polydecker sandwich complex [( η 5, μ-2,3-dihydro-1,3-diborolyl)nickel] n is reported. It is achieved by a polycondensation reaction from a binuclear precursor. EXAFS investigations confirm a Peierls distorted polydecker structure. The conductivity of the material without any doping lies in the range of highly doped polyacetylene.

Synthesis of mixed metal clusters from binuclear precursors: X-ray structure of (η 5-C 5H 5) 2(CO) 5(μ-PPh 72)(μ 4-η 2-CCPh a molecule with a μ 4-acetylide on a spiked triangular metal framework

The tetranuclear mixed metal cluster (η 5 -C 5H 5) 2Ni 2Fe 2(CO) 5(μ-PPh 2)(μ 4-η 2-CCPh) ( 1) has been synthesised in high yield via condensation of Fe 2(CO) 6(μ-PPh 2)(μ 2-η 2-CCPh) and (η 5-C 5H 5) 2Ni 2CO) 2: X-ray analysis has revealed a novel structure for 1 with μ 4 -acetylide coordinated on a spiked triangular metal skeleton.

Recent progress in the study of inner-sphere electron transfer reactions

Abstract