Patricia Delgado-Martínez

The synthesis, characterization and structural determination of four complexes with formula (PPh4)n[Rh2(µ–O2CPh)4Au(CN)2]n (1) and Kn[Rh2(µ–O2CR)4M(CN)2]n (M = Au, R = OEt (2), OMe (3); M = Ag, R = OMe (4)) are described. In all cases, the [CN-M-CN]– (M = Au, Ag) group is bridging the axial positions of the dirhodium units giving one-dimensional chains. The packing of the chains in the solid state depends on the nature of the carboxylate group of the dimetallic unit, the counterion present in the complex and the metal itself. The most striking change is observed in the Kn[Rh2(μ-O2CCH2OMe)4Au(CN)2]n complex (3) where the chains are positioned perpendicular to each other with an Au···Au interchain distance of 2.963 Å. The emission studies of this complex upon excitation at 350 nm show a clear broad emission band centered at 430 nm, while no luminescence is observed for the other compounds. The appearance of emission properties only in the case of complex 3 can be explained by its short aurophilic inter-actions.

Conventional heating and solvothermal synthetic methods (with or without microwave activation) have been used to study the reaction of o-, m- and p-methoxybenzoic acid with [Ru₂Cl(μ-O₂CMe)₄]. The tetrasubstituted series [Ru₂Cl(µ-O₂CC₆H₄-R)₄], with R = o-OMe, m-OMe and p-OMe, has been prepared by the three procedures. Depending on the synthetic method and the experimental conditions, three compounds have been isolated (1a, 1b, 1c) with the o-methoxybenzoate ligand. However, with the m- and p-methoxybenzoate ligands, only the complexes 2 and 3 have been obtained, respectively. Compound 1a, with stoichiometry [Ru₂Cl(µ-O₂CC₆H₄-o-OMe)₄]_n, shows a polymeric structure with the chloride ions bridging the diruthenium units to form linear chains. Compounds 2 and 3, with the same stoichiometry, predictably form zig-zag chains in accordance with their insolubility and their magnetic measurements. Compound 1b, [Ru₂Cl(µ-O₂CC₆H₄-o-OMe)₄(EtOH)], is a discrete molecular species with a chloride ion and one ethanol molecule occupying the axial positions of the dimetallic unit. Compound 1c is a cation-anion complex, [Ru₂(µ-O₂CC₆H₄-o-OMe)₄(MeOH)₂][Ru₂Cl₂(µ-O₂CC₆H₄-o-OMe)₄]. The cationic complex has two solvent molecules at the axial positions whereas the anionic complex has two chloride ligands at these positions. Complexes have been characterized by elemental analyses, mass spectrometry and IR and UV-vis-NIR spectroscopies. A magnetic study of complexes 1a, 1b, 2 and 3 have also been carried out. The crystal structure of compounds 1b and 1c have been solved by single X-ray crystal methods.

In this article, we report on the synthesis and characterization of the tetracarboxylatodirhodium(II) complexes [Rh₂(μ–O₂CCH₂OMe)₄(THF)₂] (1) and [Rh₂(μ–O₂CC₆H₄–p–CMe₃)₄(OH₂)₂] (2) by metathesis reaction of [Rh₂(μ–O₂CMe)₄] with the corresponding ligand acting also as the reaction solvent. The reaction of the corresponding tetracarboxylato precursor, [Rh₂(μ–O₂CR)₄], with PPh₄[Au(CN)₂] at room temperature, yielded the one-dimensional polymers (PPh₄)_n[Rh₂(μ–O₂CR)₄Au(CN)₂]_n (R = Me (3), CH₂OMe (4), CH₂OEt (5)) and the non-polymeric compounds (PPh₄)₂{Rh₂(μ–O₂CR)₄[Au(CN)₂]₂} (R = CMe₃ (6), C₆H₄–p–CMe₃ (7)). The structural characterization of 1, 3·2CH₂Cl₂, 4·3CH₂Cl₂, 5, 6, and 7·2OCMe₂ is also provided with a detailed description of their crystal structures and intermolecular interactions. The polymeric compounds 3·2CH₂Cl₂, 4·3CH₂Cl₂, and 5 show wavy chains with Rh–Au–Rh and Rh–N–C angles in the ranges 177.18°–178.69° and 163.0°–170.4°, respectively. A comparative study with related rhodium-silver complexes previously reported indicates no significant influence of the gold or silver atoms in the solid-state arrangement of these kinds of complexes.

We report herein on three zigzag one-dimensional coordination polymers of {[Ru₂(μ-NHOCR)₄](μ-SCN)}_n (R = o-Me-C₆H₄ (2), m-Me-C₆H₄ (3), p-Me-C₆H₄ (4)) formula. These new compounds have been obtained by reaction of the corresponding [Ru₂(μ-NHOR)₄(THF)₂](BF₄) complex with (NBu₄)(SCN) under different synthetic conditions. The crystal structure of [Ru₂(μ-NHOCC₆H₄-o-Me)₄(THF)₂](BF₄) (1), 2 and 3 are presented. A cis-(2,2) arrangement of the amidate ligands of the [Ru₂(μ-NHOCR)₄]⁺ units is observed in all cases. Interestingly, the structures of 2 and 3 show linkage isomerism in alternated tetraamidatodiruthenium units whose axial positions are occupied by the same type of donor atom of the SCN ligands. This results in zigzag chains with a Ru-S-C angle of 98.97° and Ru-N-C angle of 169.36° in the case of 2 and 97.99° and 159.26°, respectively, in the case of 3. The magnetic data obtained for 2–4 are indicative of a σ²π⁴δ²(π*δ*)³ ground state (S = 3/2) and a large zero-field splitting (ZFS) in all cases (D = 54.57, 62.72 and 43.00 cm⁻¹ for 2–4, respectively). Similar small antiferromagnetic interactions between diruthenium units (zJ = −0.93, −0.79 and −1.11 cm⁻¹ for 2–4, respectively) are estimated for all the polymers, suggesting an analogous zigzag arrangement of the chains for 4.

The geometry-dependent self-assembling features of two PAHs, 1 and 2, are reported. The more planar 1 forms H-type supramolecular polymers, in a highly cooperative fashion, by a combination of H-bonding and π-stacking, with rod-like morphology. However, the highly distorted 2 interacts only by means of H-bonding with no contact between the aromatic units, yielding lamellar supramolecular structures.

Two-dimensional coordination polymers of [Pr(DMSO)₂(OH₂)₃][Ru₂(CO₃)₄(DMSO)(OH₂)]·5H₂O (Prα) and [Ln(OH₂)₅][Ru₂(CO₃)₄(DMSO)]·xH₂O (Ln = Sm (Smβ), Gd (Gdβ)) formulae have been obtained by reaction of the corresponding Ln(NO₃)₃·6H₂O dissolved in dimethyl sulphoxide (DMSO) and K₃[Ru₂(CO₃)₄]·4H₂O dissolved in water. Some DMSO molecules are coordinated to the metal atoms reducing the possibilities of connection between the [Ru₂(CO₃)₄]³⁻ and Ln³⁺ building blocks giving rise to the formation of two-dimensional networks. The size of the Ln³⁺ ion and the synthetic method seem to have an important influence in the type of two-dimensional structure obtained. Slow diffusion of the reagents gives rise to Prα that forms a 2D net that is built by Ln³⁺ ions as triconnected nodes and two types of Ru₂⁵⁺ units as bi- and tetraconnected nodes with (2-c)(3-c)₂(4-c) stoichiometry (α structure). An analogous synthetic procedure gives Smβ and Gdβ that display a grid-like structure, (2-c)₂(4-c)₂, formed by biconnected Ln³⁺ ions and two types of tetraconnected Ru₂⁵⁺ fragments (β structure). The magnetic properties of these compounds are basically explained as the sum of the individual contributions of diruthenium and lanthanide species, although canted ferrimagnetism or weak ferromagnetism are observed at low temperature.

Herein, we describe the preparation of heteronuclear dirhodium-silver complexes by reaction between molecular Rh(II)-Rh(II) compounds [Rh₂(μ-O₂CR)₄L₂] (R = Me, Ph (1), CH₂OEt (2); L = solvent molecules) with paddlewheel structure and PPh₄[Ag(CN)₂]. One-dimensional coordination polymers of (PPh₄)_n[Rh₂(μ-O₂CR)₄Ag(CN)₂]_n (R = Me (3), Ph (4), CH₂OEt (5)) formula have been obtained by replacement of the two labile molecules in the axial positions of the paddlewheel structures by a [Ag(CN)₂]⁻ bridging unit. The crystal structures of 3–5 display a similar arrangement, having anionic chains with a wavy structure and bulky (PPh₄)⁺ cations placed between the chains. The presence of the (PPh₄)⁺ cations hinders the existence of intermolecular Ag-Ag interactions although several C-H····π interactions have been observed. A similar reaction between [Rh₂(μ-O₂CCMe₃)₄(HO₂CCMe₃)₂] and PPh₄[Ag(CN)₂] led to the molecular compound (PPh₄)₂{Rh₂(μ-O₂CCMe₃)₄[Ag(CN)₂]₂} (6) by replacement of the axial HO₂CCMe₃ ligands by two [Ag(CN)₂]⁻ units. The trimethylacetate ligand increases the solubility of the complex during the crystallization favouring the formation of discrete heteronuclear species.

Tunable chemoselectivity (O‐ versus C‐attack) in the rhodium‐catalyzed reactions of allenols with 4‐substituted‐1‐sulfonyl‐1,2,3‐triazoles has been achieved through the replacement of the 4‐aryl substituent by a 4‐acetyl moiety. magnified image

Functionalized ynones can be activated by Tf₂C=CH₂, which was generated in situ, to form zwitterionic species. These species were trapped in an intramolecular fashion by several nucleophiles to generate two major types of triflones in a divergent manner. Through fine‐tuning of the reaction temperature, bis(triflyl)‐6‐membered‐ or (triflyl)‐5‐membered‐fused‐heterocycles were achieved in reasonable yields in a totally selective manner. In this way, bis(triflyl)flavones, bis(triflyl)thioflavones, bis(triflyl)selenoflavones, (triflyl)benzothienopyrans, (triflyl)benzoselenophenopyrans, (triflyl)vinyl aurones, and (triflyl)pyranoindoles were constructed. Conceivable mechanistic pathways were suggested on the basis of the isolation of several intermediates and the results from control experiments.

[Ru₂Cl{μ-O₂CC₆H₂-3,4,5-(OMe)₃}₄] _n was prepared by the reaction of [Ru₂Cl(μ-O₂CCH₃] _n with 3,4,5-trimethoxybenzoic acid. The complex shows a paddlewheel structure with pairs of Ru atoms bridged by four carboxylate ligands. The axial positions are occupied by shared chloride ions giving zigzag chains. These chains are disposed parallel to each other to give a three-dimensional arrangement packed only by van der Waals forces. The final refinement shows high values of residual non-modelled electronic density. Therefore, the SQUEEZE utility [Spek (2015). Acta Cryst. C71, 9–18] was used to remove its contribution to the overal intensity data. The electron density modelled by SQUEEZE is consistent with around eight water molecules per unit cell.