Diego Martínez-Otero

Diprotodecarboxylation Reactions of 3,4-Dialkoxythiophene-2,5-dicarboxylic Acids Mediated by Ag2CO3 and Microwaves

Abstract An efficient and rapid method is reported to obtain 3,4-dialkoxythiophenes from 3,4-dialkoxythiophene-2,5-dicarboxylic acids through a diprotodecarboxylation reaction with Ag2CO3/AcOH as a catalytic system and microwave heating in dimethylsulfoxide (DMSO) as solvent. This methodology lets us obtain for the first time good performance with thiophenes bearing strong electron-donating groups such as alkoxides. This methodology eliminates the usage of harmful quinoline as solvent, as well as the long reaction times typically used (12–18 h) to obtain the 3,4-dialkoxythiophenes. The reaction of 7 diacids showed good yields (60–89%) following 20 min of microwave heating in a temperature range of 120–150 °C. [Supplementary materials are available for this article. Go to the publishers online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.] GRAPHICAL ABSTRACT

Is hexachloro-cyclo-triphosphazene aromatic? Evidence from experimental charge density analysis.

Experimental charge density studies of hexachloro-cyclo-triphosphazene (1) and the boat conformation of octachloro-cyclo-tetraphosphazene (2 a) were performed to unambiguously describe the origin of the electron delocalization in the P3 N3 ring in 1. The obtained results were compared to DFT studies in the solid state and the gas phase. Electron density analysis revealed a highly polarized nature of the P-N bonds and a modular structure of the P3 N3 and P4 N4 rings, which can be separated into independent Cl2 PN units with a perfect transferability between the compounds. Further analysis of the source function experimentally proves the presence of negative hyperconjugation involving both out-of-plane and in-plane nitrogen electrons as well as electrons of the chlorine atoms. Finally, these results discard the presence of pseudoaromatic delocalization in the nearly planar P3 N3 ring.

1D and 3D supramolecular structures exhibiting weak ferromagnetism in three Cu(II) complexes based on malonato and di-alkyl-2,2’-bipyridines

Abstract Three new Cu(II) complexes composed of malonato (mal), methylmalonato (memal), 4,4′-di-tert-butyl-2,2′-bipyridine (tbpy) and 5,5′-dimethyl-2,2′-bipyridine (mebpy) ligands, Cu(H2O)(mal)(tbpy) (1), Cu(H2O)(memal)(tbpy) (2) and Cu4(H2O)4(memal)4(mebpy)4·11H2O (3) were synthesized by simple one-pot solution reactions at ambient conditions. Single-crystal X-ray diffraction analyses reveal that the Cu(II) ions exhibit a distorted five-coordinate square pyramidal geometry. These three complexes display supramolecular arrays due to hydrogen-bonding interactions. Complexes 1 and 2 show 1-D supramolecular structures; 1 forms a double-ion chain, unlike 2, which only generates a single-ion chain. In 3, there are two identical monomers in the asymmetric unit with Z″ = 2; its high number of noncoordinated water molecules, along with hydrogen-bonding interactions between aqua ligand and memal ligand, generate a supramolecular tetramer, which mimics to produce a 3-D supramolecular framework. Besides this fascinating and yet uncommon crystallographic phenomenon in 3, the structural differences found in these complexes arise from the substituted groups in the malonato dianion and in the bipyridine ligands. These compounds exhibit weak ferromagnetic-exchange interactions.

Homo- and heteroalumoxane silicates

Acid–base reactions of LAl(OH)(μ-O)Si(OH)(OtBu)2 (L = HC[CMeNAr]2−, Ar = 2,6-iPr2C6H3) (1) with nBuLi, AlMe3, GaMe3, and ZnMe2 led to the isolation of several homo and heterometallic systems containing either the hydroxo Al–OH–M or alumoxane Al–O–M unit stabilized by a silicate moiety. In reactions with AlMe3, the stepwise deprotonation of 1 could be observed and leads to the first example of a covalent Al2SiO3 alumoxane ring and furthermore the multimetallic compounds LAl(μ-O)(μ-AlMe2)(μ-O)Si[(μ3-O)(AlMe2)](μ-OtBu)(OtBu) and LAl(μ3-O)(AlMe3)(μ-AlMe2)(μ-O)Si[(μ3-O)(AlMe2)](μ-OtBu)(OtBu) are formed in the presence of two or more equivalents of AlMe3. These compounds represent molecular models for a “pure” and “real” MAO and a rare case of a “free” AlMe3 molecule coordinated to an alumoxane moiety. The molecular structures of all compounds have been determined using single crystal X-ray diffraction.

Crystal Structure and Hirshfeld Surface Analysis of 1,2-Bis((2-(Bromomethyl)Phenyl)Thio)Ethane and Two Polymorphs of 1,2-Bis((2-((Pyridin-2-ylthio)Methyl)Phenyl)Thio)Ethane

1,2-Bis((2-(bromomethyl)phenyl)thio)ethane (1) and 1,2-bis((2-((pyridin-2-ylthio)methyl)phenyl)thio)ethane (2) were prepared and characterized by IR and NMR spectroscopy and single-crystal X-ray crystallography. X-ray diffraction studies shown that compound 1 crystallizes in a monoclinic space group P21/n with crystal parameters a=8.3970(3) A, b=12.4566(2) A, c=8.9251(3) A; β=117.911(3)°, V=824.96(5) A3 and z=2, and compound 2 exists in two monoclinic polymorphs (2a and 2b). Polymorph 2a crystals are in space group P21, with unit cell parameters a=5.3702(2) A, b=14.4235(6) A, c=15.4664(7) A, β=119.97(9)°, V=1197.97(9) A3 and z=2, while polymorph 2b crystals are in space group P21/c with unit cell parameters a=7.8312(3) A, b=9.6670(4) A, c=16.2962(5) A, β=121.219(3)°; V=1210.12(7) A3 and z=2. Variations in the crystal packing help to distinguish these two polymorphs via π-π and C−H•••π interactions. The 3D Hirshfeld surfaces and the associated 2D fingerprint plots have been performed to gain insight into the behavior of these interactions in compound 1 and polymorphs 2a and 2b.

Taming the Oxidative Power of SeO3 in 1,4-Dioxane, Isolation of Two New Isomers of Mixed-Valence Selenium Oxides, and Two Unprecedented Cyclic Esters of Selenic Acid

The reaction of (SeO3)4 with 1,4-dioxane (diox, dioxane) with or without diluting solvent led to the isolation of the unprecedented esters of selenic acid-1,2-ethyl selenate (CH2O)2SeO2 and the glyoxal diselenate O2Se[(OCHO)2]SeO2. It was possible to isolate an unknown dimeric form of Se2O5 (Se4O10·(diox)2) and a geometrical isomer of the mixed-valence oxide trans-Se3O7, both stabilized by dioxane. The dioxane adduct of monomeric selenium trioxide SeO3·diox was obtained from the reaction of (SeO3)4 with dioxane in liquid SO2. The reaction mechanism for the formation of these compounds was elucidated, and the molecular structure of the unstable form of the selenium trioxide was determined, consisting in a trimeric arrangement (SeO3)3.

Efficient, mild synthesis of N-unsubstituted 1,2,3-triazoles from methanolysis of 1-sulfonyl-1,2,3-triazoles

Abstract A small library of diverse N-unsubstituted 1,2,3-triazoles was prepared from the corresponding 1-sulfonyl-1,2,3-triazoles, which were treated only with MeOH at reflux temperature. This process was carried out in good yields showing high efficiency and good functional group tolerance. Graphical Abstract

Coordination diversity in tin compounds with bis(benzoxazole)phenol as a polydentate ligand: Synthesis and crystal structure studies

Abstract The reaction of 2,6-bis(benzoxazolyl)-4-tert-butylphenol (HL) with [nBuxSnCl4−x] (x = 0, 1) in 1:1 stoichiometry yielded the tin coordination complexes [(HL)SnnBuxCl4−x] [x = 0 (1); x = 1 (2)]. Deprotonation of HL was performed using reagents having groups with high basicity such as nBuLi or [Sn{N(SiMe3)2}2]. These basic reagents prompted the coordination of the ligand in its anionic form, yielding the complexes [(thf)2Li(L)SnCl4] (3) and [(L)Sn{N(SiMe3)2}] (4), respectively. The molecular structure of HL displayed an intramolecular hydrogen bond OH—N and a planar arrangement of the bis(benzoxazolyl)phenolic system. In the molecular structures of both complexes containing HL an intramolecular hydrogen bond of NH—O type was also present. The coordination of the ligand in either neutral or anionic form is described by a κO,κN chelate mode toward Sn. All complexes displayed bis(benzoxazolyl)phenolic moieties close to planar; the least planar system was observed in 4 that was also studied by DFT methods. Graphical abstract

Syntheses and Crystal Structures of Mn(II), Ni(II) and Cu(II) Coordination Compounds Assembled by Maleato and Dimethyl-2,2′-bipyridines

AbstractThree complexes: {[Mn(H2O)(mal)(5dmb)·H2O}n] (1); [Ni2(H2O)6(mal)2(4dmb)2]·3H2O (2); [Cu2(mal)2(4dmb)2]·3H2O (3); where mal = maleato, 4dmb = 4,4′-dimethyl-2,2′-bipyridine, and 5dmb = 5,5′-dimethyl-2,2′-bipyridine; have been synthesized, using self-assembly solution reactions at ambient conditions. Crystallographic studies show that 1 crystallizes in an orthorhombic system, space group Pna21, with a = 17.4067(4) Å, b = 11.9672(2) Å, c = 8.2075(2) Å; V = 1709.70(6) Å3. Complex 2 has a monoclinic system, space group C2/c, with a = 21.206(8) Å, b = 7.523(3) Å, c = 25.399(10) Å; β = 109.755(8)°; V = 3813(2) Å3. Complex 3 crystallizes in a monoclinic system, space group C2/c, with a = 14.6976(12) Å, b = 11.3849(10) Å, c = 22.1638(18) Å; β = 101.2998(17)°; V = 3636.8(5) Å3. Complex 1 is a one-dimensional (1D) polymer, where the Mn centers are six-coordinated in a distorted octahedral geometry. 2 is a dinuclear complex, generated by supramolecular interactions, where Ni ions are six-coordinated in a distorted octahedral geometry. 3 is a dinuclear complex with five-coordinated Cu ions having a distorted square pyramidal geometry. All three complexes exhibit hydrogen bonding interactions, which generate 2D supramolecular structures in 1 and 2, whereas in complex 3 a 3D supramolecular array is formed. These novel complexes prove that the self-assembly of a dicarboxylate ligand (mal) with three different first-row transition metals, can afford coordination compounds with diverse structural characteristics and dimensionality, which can be attributed to the different ligand coordination modes and the coordination properties of the employed metals.Graphical AbstractDivergent coordination compounds of three different transition metals have been obtained due to the versatility in the coordination modes of maleato ligand.

CCDC 1552675: Experimental Crystal Structure Determination

Related Article: Erandi Bernabe-Pablo, Vojtech Jancik, Diego Martinez-Otero, Joaquin Barroso-Flores, Monica Moya-Cabrera|2017|Inorg.Chem.|56|7890|doi:10.1021/acs.inorgchem.7b00634