Bridging Halogen Research Articles

Ferrocenium Tetrachloroantimonate

The crystal structure of ferrocinium tetrachloroantimonate, [Fe(C5H5)2][SbCl4], has been determined at 173 K. The cyclopentadiene rings in the ferrocinium cation are in an eclipsed conformation. The Sb atom is coordinated by six Cl ions in an irregular octahedral arrangement. Two Cl− ions form halogen bridges with neighbouring Sb atoms, resulting in a polymeric chain of anions {the compound may be named catena-poly[ferrocinium (dichloroantimonate-di-μ-chloro)]}. The ferrocinium cations are stacked between these polymeric chains and form two-dimensional layers parallel to the bc plane.

Ortho-Palladated metallomesogens: the effects of structural modifications on their liquid crystalline behaviour

The influence of structural changes such as the length, nature or number of terminal chains and the nature of the intermetallic bridge, on the liquid crystalline properties of palladium complexes [Pd(µ-X)Lj]2 (X–= CH3COO–, Cl–, Br–) derived from imines is reported. Acetato bridges are unfavourable for liquid crystal behaviour, but both halogen bridges clearly promote mesophase formation; SA and SC where X is Cl, and SA and N where X is Br. As far as the terminal tails are concerned, three main conclusions can be drawn: (i) the longer the terminal chains, the lower the melting points and the more ordered the mesophases, (ii) alkoxy tails increase the melting points but stabilize more ordered phases in comparison with alkyl tails, and (iii) the presence of a terminal substituent in the freely rotating anilinic ring has a more favourable effect on mesophase formation than when it is in the fixed (ortho-palladated) aldehydic ring. X-Ray experiments in the mesophase have revealed that molecular interdigitation is only present for the complexes containing two tails.

Direct Ag−Pt2 Interactions in Pentafluorophenyl A-Frame Complexes Containing Halide or OH- and Bis(diphenylphosphino)methane (dppm) as Bridging Ligands. Crystal Structures of [(C6F5)2Pt(μ-OH)(μ-dppm){Ag(PPh3)}Pt(C6F5)2]·C7H8 and [(C6F5)2Pt(μ-SC4H8)(μ-dppm)Pt(C6F5)2]·1/2C6H14

Complexes [NBu4][(C6F5)2Pt(μ-X)(μ-dppm)Pt(C6F5)2] (X = Cl, Br) react with AgClO4 and [Ag(OClO3)L] (L = PPh3, SC4H8), yielding different compounds depending on the silver reagent used. The reactions with AgClO4 in wet solvents lead to the syntheses of the complexes [(C6F5)2Pt(μ-X)(μ-dppm){Ag(H2O)}Pt(C6F5)2] [X = Cl (1), Br (2)] in which the existence of two Pt−Ag bonds is postulated. The reactions with [Ag(OClO3)(PPh3)] give similar complexes [(C6F5)2Pt(μ-X)(μ-dppm){Ag(PPh3)}Pt(C6F5)2] [X = Cl (3), Br (4)]. The presence of silver coordinated to the platinum atoms activates the substitution of the halogen bridge; thus, 3 reacts with water, yielding the complex [(C6F5)2Pt(μ-OH)(μ-dppm){Ag(PPh3)}Pt(C6F5)2] (5). Complex 5 can be prepared as well by reaction of [NBu4][(C6F5)2Pt(μ-OH)(μ-dppm)Pt(C6F5)2] (6) with [Ag(OClO3)(PPh3)]. Nevertheless, the reaction of [NBu4][(C6F5)2Pt(μ-Cl)(μ-dppm)Pt(C6F5)2] with the complex [Ag(OClO3)(SC4H8)] does not render the analogous complex to 3, but AgCl precipitates and [(C6F5)2...

Electrochemical Synthesis and Crystal Structure of a Novel One-Dimensional Halogen-Bridged Nickel(III) Complex

Abstract A novel halogen-bridged one-dimensional NiIII–X–NiIII compound, {[NiIII(en)2Cl]Cl2}∞ (en = C2H8N2) has been synthesized by electrochemical oxidation. Single crystal X-ray crystallography revealed that a bridging halogen ion is located on the midpoint between two Ni(III) atoms with Ni–Cl 2.438 (1) Å. This is the first example for electrocrystallization of halogen-bridged 1-D metal complexes.

Gold(I) complexes of azoles

(Dimethyl sulphide)AuCl reacts with azoles to give adducts [LAuX]2 [L = N-methylimidazole (N-MeIm), N-ethylimidazole (N-EtIm), N-propylimidazole (N-PrIm), 2-methylbenzoxazole (2-MeBO) and 2,5-dimethylbenzoxazole (2,5-diMeBO); X = Cl or Br] which were characterized analytically and spectroscopically, including 1H-n.m.r. I.r. and Raman studies showed that the compounds were binuclear with bridging halogen atoms. A nitrogen-containing ligand was coordinated to nitrogen N(3) atom of the azole ring in monodentate fashion.

HX · MX 3 molecules: heterodimer vapour ph ase complexes (M = B, Al; X = F, Cl) with halogen bridges : An ab initio molecular orbital study

The equilibrium structures of HX · MX 3 vapour phase complexes are examined at the Hartree-Fock level using the DZP basis set. The complexes are found to be weak electron pair donor-acceptor adducts with long and weak intermolecular halogen bridges and with the hydrogens interacting with one of the halogen atoms of MX 3 in a cyclic arrangement. The energies of complex formation are calculated with and without correction for the basis set superposition error.

Reactions of 1,4,7-trithiacyclononane, [9]aneS3, with early transition metal halides: synthesis and X-ray structure of {Fe([9]aneS3)2}[Sb2Cl8

The reactions of titanium(III) and (IV) chlorides with the crown thioether [9]aneS3 were investigated. [TiCl3- (MeCN)3] gives a purple 1:1 adduct with a proposed octahedral structure involving tridentate fac-attachment of the ligand. With [TiCl4(MeCN)2] the identity of the yellow 1∶1 adduct obtained is discussed in terms of a six-coordinate species with bidentate ligand chelation. The title compound was isolated from the reactions of [9]aneS3 with [TiCl3(MeCN)3] [SbCl6] (by accident) and iron filings/SbCl5 in MeCN solution and characterised crystallographically. The cation has two macrocyclic ligands coordinated facially to a six-coordinate Fe2+ ion; the anion comprises dimeric [(SbCl4)2] units linked together into a polymeric chain by weak halogen bridging.

Structural isomers of [Au(CH2)2PPh2]2Br4. 2. Crystal structures of cis/cis-[Au(CH2)2PPh2]2Br4 and the cationic A-frame [(.mu.-Br)(Au(CH2)2PPh2)2Br2][IBr2

Two new structural forms of Au III dimers, each derived from the oxidation of the parent compound [Au I (CH 2 ) 2 -PPh 2 ] 2 , have been characterized crystallographically. [(μ-Br)(Au(CH 2 ) 2 PPh 2 ) 2 Br 2 ] [IBr 2 ] (1) is an A-frame cationic species with a bridging halogen atom. cis/cis-[Au(CH 2 ) 2 PPh 2 ] 2 Br 4 (2) is an Au III dimer with a cis geometry for both metal centers

Preparation of the new species [W 3(μ 3-O)(μ-Cl) 2(μ-O 2CMe) 4Cl 3] − and [Mo 3(μ 3-O)(μ-Cl) 4(μO 2CMe) 2Cl 2(PMe 3) 2] − that bracket, structurally, the very common M 3(μ 3-O)(μ-X) 3(μ-O 2CR 3) 3L 3 type of cluster compound

Two new monocapped trinuclear molybdenum and tungsten clusters, which also contain different numbers of bridging halogen atoms and carboxylate groups, have been synthesized and characterized by X-ray diffraction, thus completing an entire series of monocapped trinuclear molybdenum and tungsten clusters with 1–6 bridging carboxylate ligands. Compound 1, (Et 4N)[W 3OCl 5(OAc) 4]·3CH 2Cl 2, was obtained as a byproduct in the reaction of (Et 4N) 3[W 2Cl 9] with acetic acid and acetic anhydride. Crystallographic data: space group P2 12 12 1, a=12.795(3), b=15.685(3), c=19.436(3) Å, V=3901(1) Å 3, Z=4, R=0.037. The W-W distances are 2.7280(7), 2.5754(8) and 2.5715(8) Å. The average oxidation state of the tungsten atoms is +3.33. Compound 2, (Et 4N)[Mo 3OCl 6(OAc) 2(PMe 3) 2], was synthesized by the reaction of (Et 4N)[Mo 3OCl 6(OAc) 3] with Me 3SiCl and PMe 3 in THF. Crystallographic data: space group Pna2 1, a=27.459(7), b=13.660(5), c=18.524(5) Å, V=6948 Å 3, Z=8, R=0.052. The Mo-Mo distances are 2.627(4), 2.546(3) and 2.631(6) Å. The entire series of monocapped trinuclear molybdenum and tungsten clusters with 0–6 μ-CH 3CO 2 groups is reviewed.

127I Mössbauer Spectra of Diphenyliodonium Halides

Abstract The 127I Mössbauer spectra have been obtained at 20 K for the diphenyliodonium halides, Ph2IX (X = Cl, Br) and their derivatives, (p-R–C6H4) IPhBr (R = CH3, CH3O, Cl, COOH and NO2). The valence electron populations of iodine are determined by the interactions with carbon atoms but not with bridging halogen atoms. The iodine–carbon bonds, having large p-character, are affected scarcely by the substituents at the para-position of the phenyl group. The large ηvalues for those compounds are explained in terms of a lone pair electrons on iodine(III) atoms.

Dinuclear and tetranuclear copper(II) complexes of the tetradentate ligand 1,4-bis(2-pyridylthio)phthalazine: structural, magnetic, and electrochemical studies

The tetradentate ligand 1,4-bis(2-pyridylthio)phthalazine (PTPH) forms dinuclear copper(II) complexes [Cu 2 (PTPH)Cl 4 ]-2CH 3 OH and [Cu 2 (PTPH)Br 4 ]-1.5H 2 O, involving both diazine and double halogen bridges between the copper centers, an unusual tetranuclear complex [Cu 2 (PTPH)(μ 3 -OH)(NO 3 ) 3 (H 2 O)] 2 , and a dinuclear nitrate complex [Cu 2 (PTPH)μ 2 -OH)(NO 3 ) 2 (H 2 O) 2 ](NO 3 ).

Halogen-bridged one-dimensional Ni II-Ni IV mixed-valence state and Ni III Mott-Hubbard state

The halogen-bridged nickel compounds with linear-chain structure containing hetero-halogens as bridging and counter anions, Ni(chxn) 2Cl 2 459Br 0, 541 (2) and Ni(chxn) 2Cl 1, 28Br 1, 72 (3) (chxn=1R, 2R-diaminocyclohexane), have been synthesized by bromination of Ni(chxn) 2Cl 2 and chlorination of Ni(chxn) 2Br 2 in 2-methoxyethanol, respectively. Their structures have been determined by single-crystal X-ray diffraction method. In both (2) and (3), the Ni(chxn) 2 moieties are bridged by halogens to construct linear-chain structures and hydrogen-bond networks of NH…X…HN which hold the chains are extended over the chains two-dimensionally. The bridging halogens in (2) and (3) are located at the midpoints between two nickel atoms on the chains, that is −N III-X-N III-structure with no Peierls distortion, indicating that these compounds take the Mott-Hubbard state as the same as the compounds containing homo-halogens, Ni(chxn) 2Cl 3 (1) and Ni(chxn) 2Br 3 (4) reported previously. The occupancy factors of Cl and Br in bridging and counter halogen sites in (2) and (3) are determined by X-ray analyses: [Ni(chxn) 2Cl xBr 1−x]Cl yBr 2−y, x=0.976 and y=1.483 in (2) and x=0.68 and y=0.60 in (3). They show intense charge transfer bands in the visible region only with an electric vector parallel to the 1-D chain and their energies are in the order, (1)>(2)>(3)>(4). Substitution of the counter Cl − ions in [Ni(chxn) 2Cl]Cl 2 (1) with more bulky ClO 4 − ions succeeded in producing Ni(chxn) 2Cl(ClO 4) 2 by a heterogeneous reaction. The solid state 13C NMR spectra suggest that Ni(chxn) 2Cl(ClO 4) 2 take not the Mott-Hubbard state but the Ni II-Ni IV mixed-valence state formulated as [Ni(chxn) 2][NiCl 2(chxn) 2](ClO 4) 4. These results indicate that the oxidation states of Ni atoms in these compounds are strongly affected by the kind of counterion through the hydrogen-bond and/or bulkiness.

Optical and Raman Signatures of Polarons in Mixed-Valent Linear Chain Metal Complexes with Halogen Bridges

The vibrational (Raman) and optical properties associated with the ground state and polaronic defects are compared and contrasted for the charge-density-wave PtX materials belonging to two different regimes: the highly valence localized compound PtCl and the more valence delocalized compound PtBr. The model for PtCl explicitly includes nearest-neighbor Coulomb attraction and metal ion-ion electrostatic repulsion: with increasing valence delocalization this reduces to the linear Peierls-Hubbard model used for PtBr. The results agree well with the available experimental data for PtCl and PtBr. Buckling of Cl atoms out of the chain axis is found to be important in order to obtain the observed Raman frequencies for electron polarons and bipolarons in PtCl

Cesium Iodometallates(III), Cs3M2I9, with M = Rare Earth. A Structural Investigation by 127I NQR

Abstract The 127NQR spectra of cesium enneaiododimetallates Cs3M2I9, M = Dy, Ho, Er, Yb, Y and Tb, Sm, Nd, Pr have been studied as a function of temperature. The compounds are characterized by X-ray powder diffraction, too. The first group of compounds, M = Dy • • • Y, belongs to the family of Cs3Cr2Cl9-type enneahalogenodimetallates (III). The crystal structure of the second group, M = Tb ...Pr , is less symmetric, as in the 127I NQR the presence of two crystallographically independent iodines shows up. Nuclear quadrupole coupling constants for the terminal and bridging halogens have been calculated from the NQR frequencies. The dependence of the NQR frequencies and of the crystal structure from the radius of the RE3⊕ -ion is discussed. The NQR spectra reveal phase transitions of the investigated enneaiododimetallates (III), for which Tlr also depends on r(RE3⊕). Positive temperature coefficients of the 127I have been found and the influence of π-bond character is considered.

IR Study of the H-Bond Coupled with the Mixed-Valence State of Halogen-Bridged Metal Complexes

IR spectroscopic measurements were made on the halogen bridged metal complexes of {M(chxn) 2 Br}Br 2 (M=Pt, Pd and Ni) which have interchain N-H···Br bonds strongly coupled with the electronic state of chains. The splitting of the N-H stretching modes for Pt and Pd complexes show a good correlation with the amplitude of the CDW in the chain, i.e. with the displacement of bridging halogen ion. No splitting of the N-H band was observed for the Ni complex, which is an evidence of a transformation from a mixed valence (CDW) state to a mono-valence (the Mott-Hubbard) state by a replacement of M=Pt (or Pd) by Ni. Such IR studies were applied for the estimation of the CDW amplitude under hydrostatic pressure. The results indicated that more detailed information can be derived by the IR study than the X-ray analysis.

Zirconium chloride cluster phases centered by transition metals Mn-Ni. Examples of the Nb6F15 structure

Reactions of Zr, ZrCl{sub 4}, chlorides of Mn-Ni (Z), and LiCl where appropriate in sealed Ta tubing at 750-900C yield the dark purple Li{sub 2}Zr{sub 6}Cl{sub 15}Mn, LiZr{sub 6}Cl{sub 15}Fe, Zr{sub 6}Cl{sub 15}Co, and Zr{sub 6}Cl{sub 15}Ni, all with the basic Nb{sub 6}F{sub 15} structural framework. The structures of all four have been refined by single-crystal x-ray means, and the results are reported. Transition-metal-centered clusters in this structure type are interconnected at all vertices by linear chlorine bridges into three-dimensional ReO{sub 3}-like networks (Zr{sub 6}(Z)Cl{sup i}{sub 12})Cl{sub 6/2}{sup a-a}, and two such networks interpenetrate but are unlinked. The relative sizes of the clusters and bridging halogens are critical for this disposition. The lithium atoms in Li{sub 2}Zr{sub 6}Cl{sub 12}Mn were refined in an internetwork, six-coordinate site of D{sub 2h} symmetry, consistent with the solid-state NMR spectrum observed for {sup 7}Li. The expansions of the networks about Zr-Cl{sup a-a} necessary to accommodate the lithium ions correspond to volume increments of 12-13 {angstrom}{sup 3} for each ion. The effective sizes of the metal interstitials Z increase slightly from Mn to Ni.

Studies of mixed-valence states in three-dimensional halogen-bridged gold compounds, Cs2Au I Au III X6, (X = Cl, Br or I). Part 2. X-Ray photoelectron spectroscopic study

The mixed-valence states in Cs2AuIAuIIIX6(X = Cl, Br or I) were systematically studied by X-ray photoelectron spectroscopy of the Au 4f region for the first time. The gold valence states in halogeno complexes of AuI and AuIII were also studied. In Cs2Au2X6 the difference between the oxidation state of AuI and that of AuIII decreases as the covalency of the –AuI–X–AuIII–X– bonds increases in the order X = Cl < Br < I, because the charge-transfer interaction between AuI and AuIII through the bridging halogen becomes stronger in this order. In the non-stoichiometric CsAu0.6Br2.6 the oxidation state of Au is considered to be almost homogeneous.

Studies of mixed-valence states in three-dimensional halogen-bridged gold compounds, Cs2AuIAuIIIX6(X = Cl, Br or I). Part 3. Gold-197 Mössbauer spectroscopic study

The mixed-valence states in Cs2AuIAuIIIX6(X = Cl, Br or I) were studied by Mossbauer spectroscopy with the 77.34 keV γ-ray resonance of 197Au. The states AuI and AuIII could clearly be distinguished for all compounds. From an analysis of the isomer shifts and the quadrupole splittings the following conclusions were drawn: (1) the signs of the electric field gradient at AuI and AuIII are negative and positive, respectively; (2) the charge-transfer interaction between AuI and AuIII through the bridging halogen increases in the order X = Cl < Br < I and should be stronger in the xy plane (⊥c axis) than in the z direction (∥c axis); (3) for the cubic phase CsAu0.6Br2.6 only a single resonance line having a rather broad half-width was observed.

Synthesis and spectroscopy of linear-chain palladium(II,IV) and platinum(II,IV) complexes involving quadridentate ligands

The effects of the in-plane ligand, the metal atom, the bridging halogen atom and the counter-anion on the electronic structures of a series of linear-chain, halogen-bridged, mixed-valence complexes of platinum and palladium have been investigated. Complexes of the type [ML][MLX2]Y4, where M = Pd or Pt, X = Cl, Br or I, L = 3, 7-diazanonane-1,9-diamine, 4,7-diazadecane-1,10-diamine, 1,4,8,11-tetraazacyclotetradecane or 1,4,8,12-tetraazacyclopentadecane and Y = BF4, ClO4 or PF6, have been examined by means of electronic, Raman and resonance-Raman spectroscopy. The electronic spectra of the complexes each show an intense intervalence charge-transfer band in the visible region, occurring at higher energy, Eg, than it does for analogous bis(ethylenediamine) complexes; this implies greater localisation of valences for the quadridentate than for the bis(ethylenediamine) complexes, in agreement with conclusions drawn from the X-ray structural results. Resonance-Raman spectra of the complexes display long progressions in the symmetric chain stretching mode ν1, νsym(X–MIV–X), corresponding members occurring at higher wavenumbers than for the analogous en complexes. Progressions in ν1 reach at most to v1= 12 for X = Cl, v1= 9 for X = Br and v1= 5 for X = I. Both the trends in Eg and also those in v1(max) vary in the order I < Br < Cl, Pd < Pt and BF4⩽ ClO4 < Pf6, implying increased valence localisation to the right in each series.

Crystal structures of linear-chain halogen-bridged binuclear platinum complexes, dihydrate forms of K 4[Pt 2X(pop) 4] · nH 2O (X=Cl and Br)

Crystal structures of the potassium catena-μ-halogenotetrakis(μ-diphosphonato-P,P)-diplatinum(4−) dihydrate, K 4[Pt 2X(pop) 4]·2H 2O (X=Cl ( 1) and Br ( 2); pop=P 2O 5H 2 2−), have been determined by the single crystal X-ray diffraction method. The complexes are isomorphous to each other and crystallize in orthorhombic, space group Pbnm, Z=4: for 1, a=9.553(2), b=15.440(3), c=17.123(3) Å, V=2525.6(8) Å 3 at room temperature; for 2, a=9.510(1), b=15.338(2), c=17.125(2) Å, V=2497.9(6) Å 3 at 125 K. The structures consist of linear chains with a repeating unit of ··· Pt IIPt II ··· XPt IIIPt IIIX ··· along the c axes. The linear chains are not straight but a little bent to form zigzag chain structures, the bent angles defined by the PtPt bonds and the c axes being 3.34(1)° for 1 and 3.11(1)° for 2, respectively. The PtPt separations, which are bridged by four pyrophosphato ligands (P 2O 5H 2 2−), are 2.835(1) Å for 1 and 2.834(1) Å for 2. The bridging halogen atoms are disordered over two sites in the chains, giving short PtX and long Pt ··· X separations: 2.406(4) and 3.362(4) Å for 1 and 2.539(1) and 3.217(1) Å for 2, respectively. The deviations of the bridging halogen atoms from the midpoints between two Pt dimers are significantly larger than those of the trihydrate modifications.