Bromido Ligands Research Articles

Crystal structures of two polymorphs for fac-bromidotricarbonyl[4-(4-methoxyphenyl)-2-(pyridin-2-yl)thiazole-κ2 N,N′]rhenium(I)

Crystallization of the title compound, fac-[ReBr(ppt-OMe)(CO)3] (ppt-OMe = C15H12N2OS), from CH2Cl2/n-pentane (1:5 v/v) at room temperature gave two polymorphs, which crystallize in monoclinic (P21/c; α form) and orthorhombic (Pna21; β form) space groups. The ReI complex molecules in either polymorph adopt a six-coordinate octahedral geometry with three facially-oriented carbonyl ligands, one bromido ligand, and two nitrogen atoms from one chelating ligand ppt-OMe. In the crystal, both polymorph α and β form di-periodic sheet-like architectures supported by multiple hydrogen bonds. In polymorph α, two types of hydrogen bonds (C—H...O) are found while, in polymorph β, four types of hydrogen bonds (C—H...O and C—H...Br) exist.

Accessing Homo- and Heterobimetallic Complexes with a Dianionic Pentadentate Ligand.

The tetrapyrazolylpyridyl diborate (B2Pz4Py) ligand provides a suitable platform for the isolation of heterobimetallic main-group element compounds as well as homotetrametallic copper complexes. The heterobimetallic tin(II)-lithium(I) (1) and tin(II)-thallium(I) (2) complexes have been synthesized, isolated, and fully characterized including single-crystal X-ray diffraction analysis. When reacted with copper(I) sources, complex 2 grants access to a homotetrametallic copper(I) complex (4). Upon subsequent oxidation, 4 gives rise to the bimetallic copper(II) complex 5, in which the two copper(II) centers are connected via a bridging bromido ligand (CuII-μ-Br-CuII).

Selective Supramolecular Recognition of Nitroaromatics by a Fluorescent Metal–Organic Cage Based on a Pyridine-Decorated Dibenzodiaza-Crown Macrocyclic Co(II) Complex

Two isomorphous fluorescent (FL) lantern-shaped metal-organic cages 1 and 2 were prepared by coordination-directed self-assembly of Co(II) centers with a new aza-crown macrocyclic ligand bearing pyridine pendant arms (Lpy). The cage structures were determined using single-crystal X-ray diffraction analysis, thermogravimetric, elemental microanalysis, FT-IR spectroscopy, and powder X-ray diffraction. The crystal structures of 1 and 2 show that anions (Cl- in 1 and Br- in 2) are encapsulated within the cage cavity. 1 and 2 bear two coordinated water molecules that are directed inside the cages, surrounded by the eight pyridine rings at the "bottom" and the "roof" of the cage. These hydrogen bond donors, π systems, and the cationic nature of the cages enable 1 and 2 to encapsulate the anions. FL experiments revealed that 1 could detect nitroaromatic compounds by exhibiting selective and sensitive fluorescence quenching toward p-nitroaniline (PNA), recommending a limit of detection of 4.24 ppm. Moreover, the addition of 50 μL of PNA and o-nitrophenol to the ethanolic suspension of 1 led to a significant large FL red shift, namely, 87 and 24 nm, respectively, which were significantly higher than the corresponding values observed in the presence of other nitroaromatic compounds. The titration of the ethanolic suspension of 1, with various concentrations of PNA (>12 μM) demonstrated a concentration-dependent emission red shift. Hence, the efficient FL quenching of 1 was capable of distinguishing the dinitrobenzene isomers. Meanwhile, the observed red shift (10 nm) and quenching of this emission band under the influence of a trace amount of o- and p-nitrophenol isomers also showed that 1 could discriminate between o- and p-nitrophenol. Replacement of the chlorido with a bromido ligand in 1 generated cage 2 which was a more electron-donating cage than 1. The FL experiments showed that 2 was partially more sensitive and less selective toward NACs than 1.

Crystal structure of (7-{[bis-(pyridin-2-ylmeth-yl)amino-κ3 N,N',N'']meth-yl}-5-chloro-quinolin-8-ol)di-bromidozinc(II).

In the title compound, [ZnBr2(C22H19ClN4O)], the ZnII atom adopts a distorted square-pyramidal coordination geometry, formed by two bromido ligands and three N atoms of the bis-(pyridin-2-ylmeth-yl)amine moiety in the penta-dentate ligand containing quinolinol. The ZnII atom is located well above the mean basal plane of the square-based pyramid. The apical position is occupied by a Br atom. The O and N atoms of the quinolinol moiety in the ligand are not coordinated to the ZnII atom. An intra-molecular O-H⋯N hydrogen bond, generating an S(5) ring motif, stabilizes the mol-ecular structure. In the crystal, the mol-ecules are linked by inter-molecular C-H⋯Br hydrogen bonds, generating ribbon structures containing alternating R 2 2(22) and R 2 2(14) rings. These ribbons are linked through an inter-molecular C-H⋯Br hydrogen bond, forming a two-dimensional network sheet.

Synthesis and crystal structure of tri-ethyl-ammonium hexa-bromido-uranate(IV) di-chloro-methane monosolvate.

Tri-ethyl-ammonium hexa-bromido-uranate(IV) di-chloro-methane monosolvate, [(C2H5)3NH]2[UBr6]·CH2Cl2, was obtained in the form of dark-brown crystals from the reaction of uranium penta-bromide with NEt3 and ethyl-ene glycol in di-chloro-methane at low temperature. During the progress of the reaction, the reduction of uranium(V) to uranium(IV) was observed, whose associated oxidation product could not be identified. The uranium atom of the [UBr6]2- anion is coordinated by six bromido ligands in the shape of an octa-hedron. Between cations, anion and solvent mol-ecules of crystallization, numerous C-H⋯Hal hydrogen-bond-like inter-actions are present, leading to a three-dimensional network structure.

Selective synthesis and crystal structures of manganese(I) complexes with a bi- or tridentate terpyridine ligand.

The crystal structures of two manganese(I) complexes with a different coordination mode of the supporting ligand are reported: fac-bromido-tricarbon-yl(4'-phenyl-2,2':6',2''-terpyridine-κ2 N,N')manganese(I), [MnBr(C21H15N3)(CO)3], I, and cis-bromido-dicarbon-yl(4'-phenyl-2,2':6',2''-terpyridine-κ3 N,N',N'')manganese(I), [MnBr(C21H15N3)(CO)2], II. In both complexes, the manganese(I) atom is coordinated by terminal carbonyl ligands, a bromide ion, and a 4'-phenyl-2,2':6',2''-terpyridine ligand within a distorted octa-hedral environment. In I, the metal ion is facially coordinated by three carbonyl ligands and the terpyridine ligand binds in a bidentate fashion. The non-coordinating nitro-gen atom in the terpyridine ligand is positioned on the side opposite to the bromido ligand. In II, the metal ion is coordinated by two carbonyl ligands in a cis configuration and the terpyridine ligand binds in a tridentate fashion; notably, one carbonyl and the trans bromido ligand are mutually disordered over two positions. In I, the complex mol-ecules are linked by C-H⋯Br hydrogen bonds. In II, aromatic π-π contacts are present, as well as pairs of C-H⋯Br and C-H⋯O hydrogen bonds.

Novel and efficient bridged bis(N‐heterocyclic carbene)palladium(II) catalysts for selective carbonylative Suzuki–Miyaura coupling reactions to biaryl ketones and biaryl diketones

Bridged N,N′‐substituted bisbenzimidazolium bromide salts (L1, L2, and L3) were synthesized and fully characterized. Reactions of palladium acetate with L1, L2, and L3 afforded corresponding new bridged bis(N‐heterocyclic carbene)palladium(II) complexes (C1, C2, and C3) in high yields. The X‐ray structure of complex C1 showed that the Pd(II) ion is bonded to the two carbon atoms of the bis(N‐heterocyclic carbene) and two bromido ligands are in the cis position, resulting in a distorted square planar geometry. The three Pd(NHC)2Br2 complexes C1, C2, and C3 were evaluated in carbonylative Suzuki–Miyaura coupling reactions of aryl boronic acids with aryl halides and displayed high catalytic activity with low catalyst loading. The coupling reactions of aryl bromides were selective towards the carbonylation product at higher carbon monoxide pressure.

Resurgence of Organomanganese(I) Chemistry. Bidentate Manganese(I) Phosphine-Phenol(ate) Complexes.

As part of the United Nations 2019 celebration of the periodic table of elements, we are privileged to present our studies with the element manganese in this Forum Article series. Catalysis with organomanganese(I) complexes has recently emerged as an important area with the discovery that pincer manganese(I) complexes that can activate substrates through metal-ligand cooperative mechanisms are active (de)hydrogenation catalysts. However, this rapidly growing field faces several challenges, and we identify these in this Forum Article. Some of our efforts in addressing these challenges include using alternative precursors to Mn(CO)5Br to prepare manganese(I) dicarbonyl complexes, the latter of which is usually a component of active catalysts. Specifically, the synthesis of a new bidentate phosphine-phenol ligand along with its corresponding coordination chemistry of five new manganese(I) complexes is described. The complexes having two phenol-phenolate moieties interact with the secondary coordination sphere to enable facile loss of the bromido ligand and even one of the CO ligands to afford manganese(I) dicarbonyl centers.

Bioinspired Tungsten Complexes Employing a Thioether Scorpionate Ligand.

The synthesis and characterization of a series of novel tungsten complexes employing the bioinspired, sulfur-rich scorpionate ligand [PhTt] (phenyltris((methylthio)methyl)borate) are reported. Starting from the previously published tungsten precursor [WBr2(CO)3(NCMe)2], a salt metathesis reaction with 1 equiv of Cs[PhTt] led to the desired complex [WBr(CO)3(PhTt)] (1), making it the first tungsten complex employing a poly(thioether)borate ligand. Surprisingly, the reaction of [WBr2(CO)3(NCMe)2] with an excess of the ligand gave complex [W(CO)2(η2-CH2SMe)(PhTt)] (2) with a bidentate (methylthio)methanide ligand as the major product. Thereby, phenyldi((methylthio)methyl)borane is formed, which was isolated and characterized by NMR spectroscopy. The bromido ligand in [WBr(CO)3(PhTt)] was further substituted by the S,N-bidentate methimazole in order to make the first coordination sphere more sulfur-rich forming [W(CO)2(mt)(PhTt)] (3). Alkyne tungsten complexes employing the sulfur-rich scorpionate ligand were accessible by reaction of [WBr2(CO)(C2R2)2(NCMe)] (R = Me, Ph) with Cs[PhTt] forming [WBr(CO)(C2R2)2(PhTt- S, S')] (R = Me 4, Ph 5), with the potentially tridentate ligand coordinated only via two sulfur atoms. In the case of 4, the higher flexibility of the bidentate coordination leads to the formation of two isomers with respect to the six-membered ring formed by the tungsten center and the two coordinated sulfur atoms of the ligand. All complexes 1-5 were characterized by single-crystal X-ray diffraction analysis.

Synthesis, structure and DFT conformation analysis of CpNiX(NHC) and NiX2(NHC)2 (X = SPh or Br) complexes

The synthesis, density functional theory (DFT) conformational study and structure analysis of novel two-legged piano stool Ni N-heterocyclic carbene (NHC) complexes and square planar Ni bis-N-heterocyclic carbene complexes, all containing either bromido- or thiophenolato ligands, are described. [CpNi(SPh)(NHC)] complexes were obtained from the neutral 18-electron [CpNiBr(NHC)] complexes by substitution of a bromido ligand with SPh, using NEt3 as a base to abstract the proton of HSPh. The 16-electron biscarbene complexes [Ni(SPh)2{NHC}2] were isolated when an excess of HSPh was added to the reaction mixture. Biscarbene complexes of the type [NiBr2(NHC)2] were obtained in the reaction of NiCp2 with a slight excess of the specific imidazolium bromide salt. The molecular and electronic structures of the mono- and bis-N-heterocyclic carbene complexes have been analysed using single crystal diffraction and density functional theory (DFT) calculations, to give insight into their structural properties.

Novel Co(III)/Co(II) mixed valence compound [Co(bapen)Br2]2[CoBr4] (bapen = N,N′-bis(3-aminopropyl)ethane-1,2-diamine): Synthesis, crystal structure and magnetic properties

Green crystals of Co(III)/Co(II) mixed valence compound [Co(bapen)Br2]2[CoBr4] (bapen = N,N′-bis(3-aminopropyl)ethane-1,2-diamine) were isolated from the aqueous system CoBr2 – bapen – HBr, crystallographically studied and characterized by elemental analysis and IR spectroscopy. Its ionic crystal structure is built up of [Co(bapen)Br2]+ cations and [CoBr4]2− anions. The Co(III) central atoms within the complex cations are hexacoordinated (donor set trans-N4Br2) with bromido ligands placed in the axial positions. The Co(II) atoms exhibit distorted tetrahedral coordination. Beside ionic forces weak NH⋯Br intermolecular hydrogen bonding interactions contribute to the stability of the structure. Temperature variable magnetic measurements confirm the S = 3/2 behavior with the zero-field splitting of an intermediate strength: D/hc = 8.7 cm−1.

Part XXIII. Synthesis and characterization of platinum(IV) complexes with O,O′-dialkyl esters of (S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoic acid and bromido ligands. Antimicrobial, antibiofilm and antioxidant screening

Four new platinum(IV) complexes C1–C4 of general formula [PtBr4(R2-S,S-eddv)], (R=ethyl, propyl, butyl and pentyl; S,S-eddv=(S,S)--ethylenediamine-N,N′-di-2-(3-methyl)butanoate) have been synthesized and characterized by microanalysis, infrared, 1H and 13C NMR spectroscopy. In vitro antimicrobial activity for these and [PtBr4(R2-S,S-eddp)] complexes (S,S-eddp=(S,S)-ethylenediamine-N,N′-di-2-propanoate) has been investigated. The antibacterial activity was tested against 16 strains of bacteria determining the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) using microdilution method. In general, platinum(IV) complexes manifested moderate activity against the Gram positive bacteria and low activity against the Gram negative bacteria. The complexes showed weak antioxidative properties tested by two methods (DPPH and reducing power assay).

Crystal structure of catena-poly[[cadmium(II)-di-μ2-bromido-μ2-l-proline-κ(2) O:O'] monohydrate

In the title coordination polymer, {[CdBr2(C5H9NO2)]·H2O} n , the Cd(II) ion is coordinated by four bromido ligands and two carboxyl-ate oxygen atoms of two symmetry-related proline ligands, which exist in a zwitterionic form, in a distorted octa-hedral geometry. There is an intra-molecular N-H⋯O hydrogen bond between the amino group and the carboxyl-ate fragment. Each coordinating ligand bridges two Cd(II) atoms, thus forming polymeric chains running along the c-axis direction. The water mol-ecules of crystallization serve as donors for the weak inter-molecular O-H⋯O and O-H⋯Br hydrogen bonds that link adjacent polymeric chains, thus forming a three-dimensional structure. N-H⋯O and N-H⋯Br hydrogen bonds also occur.

Synthesis and Crystal Structure of Alkynylplatinum(IV) Complex Containing the Terpyridine Ligand

Reaction of square planar [PtII(C≡CPh)(tpy)]+ (tpy = 2,2′:6′,2′′-terpyridine) with bromine at low temperature provides a general route for the synthesis of octahedral alkynyl(terpyridine)platinum(IV) complex. In this first example of alkynyl(terpyridine)platinum(IV) complex, the alkynyl group is situated in trans position relative to the central nitrogen atom of the terpyridine ligand, and the two bromido ligands are situated in trans positions; an X-ray structural analysis has been completed for trans(Br)-[PtIVBr2(C≡CPh)(tpy)]+.

Bis(functionalized NHC) Palladium(II) Complexes via a Postmodification Approach

A series of 20 bis(functionalized NHC) Pd(II) complexes have been conveniently synthesized through postmodification reactions of the common parent NHC complexes trans-[PdBr2(C3Br-bimy)2] (1a) and trans-[PdBr2(C3Br-imy)2] (1b) (C3Br-bimy = 1-benzyl-3-(3-bromopropyl)benzimidazolin-2-ylidene and C3Br-imy = 1-benzyl-3-(3-bromopropyl)imidazolin-2-ylidene) with an N-C3Br tether. Depending on the nature of the nucleophiles added, competing bromido ligand displacements also occurred. In comparison to the conventional access to functionalized NHC complexes, which involves metalation of individually prefunctionalized azolium salts, this highly modular method proves more effective in cost and time savings. The tetraalkylammonium-functionalized complex trans-[PdBr2(C3NEt3-bimy)2]Br2 (14) as a product of the second-generation postmodification of complex 1a was also tested for its catalytic activity in Mizoroki–Heck coupling reactions to study and model the effect of a catalytic amount of ammonium salt additive in Pd-c...

Stereospecific ligands and their complexes. Part XVII. Synthesis and characterization of ethylenediamine-N,N′-di-S,S-2-(3-methyl)butanoic acid and its platinum(IV) complex with bromido ligands. Crystal structure of s-cis-[PtBr2(S,S-eddv)]·H2O

The synthesis of novel platinum(IV) complex of formula [PtBr2(S,S-eddv)]·H2O (S,S-eddv=ethylenediamine-N,N′-di-S,S-2-(3-methyl)butanoate ion) is reported. The complex has been obtained by direct reaction of potassium-hexabromidoplatinate(IV) with neutralized ethylenediamine-N,N′-di-S,S-2-(3-methyl)butanoic acid (H2-S,S-eddv). The ligand and complex were characterized by elemental analysis, infrared, 1H and 13C NMR spectroscopy. The spectroscopically predicted geometrical configuration of the obtained complex was confirmed by X-ray analyses of the crystal structure of the s-cis-[PtBr2(S,S-eddv)]·H2O. The asymmetric unit of the complex contains three crystallographically independent s-cis-[PtBr2(S,S-eddv)] and water molecules. The Pt(IV) atom in each complex molecule exhibits a distorted octahedral coordination geometry, built up by two cis-coordinated bromido ligands and one cis-N,N′ and trans-O,O′ coordinated S,S-eddv ligand (configuration index: OC-6-33). In the crystal structure, intermolecular N–H⋯O hydrogen bonds are found between the complex and water molecules.

Catena-Poly[[(N,N-di-methyl-cyanamide-κN)lithium]-μ3-bromido

The title complex, [LiBr(C3H6N2)]n, is the unexpected product of a reaction beteween (Dipp)N(Li)SiMe3 (Dipp = 2,6-diiso­propyl­phen­yl), Me2NCN and CuBr. The compound is a one-dimensional polymer with a step structure derived from the association of inversion dimers, formed by bromido ligands bridging two Li+ cations, each of which carries a di­methyl­cyanamide ligand. The planar (LiBr)2 unit of the polymer core has a regular rhombic shape [Li—Br—Li 77.55 (16)° and Br—Li—Br 102.45 (16)°]. These (LiBr·NCNMe2)2 dimers represent the repeat unit of a polymer system propagated by additional Br—Li and Li—Br bonds generating an infinite step structure along the a-axis direction.

Structure and properties of a rare-topology [MnII4]-core complex with terminal bromido ligands

A rare-topology [Mn II 4 ]-core complex [Mn 4 Br 4 (ppko) 4 (CH 3 OH) 4 ] ( 1 ; ppkoH = phenyl 2-pyridyl ketoxime) was synthesized via a solvothermal route and characterized by X-ray diffraction, IR, EPR, ESI-MS and magnetic properties measurements. In 1 Mn 2+ ions are bridged with phenyl 2-pyridyl ketoxime ligands. Bromine atoms and methanol molecules are terminal ligands. A comparison is made to the reported analogues with different terminal ligands pattern.

Condensed Double‐Chain Cluster Complexes with Seven‐Coordinate Endohedral Iridium Atoms in {Ir2Gd5}Br5

AbstractAbstract. The new condensed double‐chain cluster complex compound {Ir2Gd5}Br5 was obtained from a reaction of GdBr3 with metallic gadolinium and iridium at elevated temperatures. The thin black needles crystallize with the orthorhombic crystal system, space group Pnma(no. 62); a = 1255.4(1) pm, b = 414.05(3) pm, c = 2633.8(3) pm,Z = 4, R1/wR2 = 0.0504/0.0346 for all data. Monocapped trigonal prisms of gadolinium atoms with endohedral iridium atoms are connected by common rectangular faces to chains and further by edges to double chains, which form a herringbone arrangement. The double chains are coordinated by bromido ligands and are connected in accord with the formulation {Ir2Gd5}Br4/2iBr2/3i(e)Br1/3i(f)Br2/2i–i(e/f)Br1/2i–aBr1/2a–i.

Crystal Structure and Spectroscopic Properties of trans‐Dibromidobis(propane‐1, 3‐diamine)chromium(III) Perchlorate

AbstractThe structure of trans‐[Cr(tn)2Br2]ClO4 (tn = propane‐1, 3‐diamine) has been determined by a single‐crystal X‐ray diffraction study at 100 K. The complex crystallizes in the space group P$\bar{1}$ of the triclinic system with two mononuclear formula units in a cell of dimensions a = 6.8220(4), b = 8.86199(9), c = 12.6644(8) Å and α = 77.859(7)°, β = 81.765(6)°, and γ = 77.764(7)°. The chromium atom is in a slightly distorted octahedral environment coordinated by four nitrogen atoms of two tn ligands and two bromine atoms in trans positions. The two six‐membered chelate rings in the complex cations are oriented in an anti chair‐chair conformation with respect to each other. The mean Cr–N(tn) and Cr–Br bonds are 2.093(3) and 2.4681(4) Å, respectively. The crystal packing is stabilized by hydrogen bonds. The infrared and electronic absorption spectral properties are consistent with the result of X‐ray crystallography. It is confirmed that the nitrogen atoms of the tn ligand are strong σ‐donors, but the bromido ligands have weak σ‐ and π‐donor properties toward the chromium(III) ion.