Br Bridges Research Articles

Interactions of Pyridine‐Based Organic Cations as Structure‐Determining Factors in Perovskite‐Related Compounds AxPb(II)yBrz

AbstractWe have synthesised and characterised 21 new ternary Pb(II) bromides with 16 different pyridine‐based organic cations by single crystal XRD measurements. The dominating composition is APbBr3 with 10 representatives, but also 6 examples for APb2Br5 were found. The systematic variation of topological aspects of the organic cations allowed conclusions on the influence of N−H⋅⋅⋅Br hydrogen bridges on the connectivity and bonding situation of the Pb−Br polyhedra. Additionally, it turned out, that further weak ionic interactions can have an influence, if the formation of N−H⋅⋅⋅Br hydrogen bridges is hindered by steric effects. In general, the high versatility of the dominating PbBr6 octahedra, and in some cases higher or lower coordination numbers, allows conclusions on the parameters that influence pattern and extent of the N−H⋅⋅⋅Br bridges as the strongest structure‐determining factor. Type and extent of N−H⋅⋅⋅Br bridges have also an impact on the distortion of the PbBr6 octahedra ranging from nearly regular PbBr6 octahedra to 2+2+2 and 1+2+2+1 patterns with significant lone pair activity. Finally, the connectivity mode of the octahedra relates to formation and strength of hydrogen bonds.

Synthesis, Crystal Structures and Urease Inhibition of 4-Bromo-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide and Its Dinuclear Copper(II) Complex.

A new dinuclear copper(II) complex [Cu2(μ-Br)2L2]·0.5MeOH with the benzohydrazone ligand 4-bromo-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide (HL) has been synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopic studies. Single crystal structures of the complex and the benzohydrazone compound were studied. The Cu atoms in the complex are coordinated by two benzohydrazone ligands and two Br bridging groups, forming square pyramidal coordination. The complex has good inhibitory activity on Jack bean urease, with IC50 value of 1.38 μmol·L-1.

Ortho-Palladation of (Z)-2-Aryl-4-Arylidene-5(4H)-Oxazolones. Structure and Functionalization

Ortho-palladated complexes of (Z)-2-aryl-4-arylidene-5(4H)-oxazolones have been prepared through oxidative addition. The reaction of (Z)-2-phenyl-4-(2-bromobenzylidene)-5(4H)-oxazolone (4) with Pd2(dba)3·CHCl3 gives the six-membered cyclopalladated dinuclear complex [Pd(μ-Br)(o-C6H4CH═CNC(O)OCPh)]2 (7). The reaction of 7 with PPh3 gives dinuclear 9, which incorporates one phosphine per Pd atom through cleavage of the Pd−N bond, and preserves the bromide bridging system. However, reaction with PPh2Me gives mononuclear 8, which incorporates two phosphines as a results of the cleavage of the μ-Br system and N displacement. In contrast, the reaction of 7 with pyridine gives complex 12 due to simple cleavage of the Br bridge, leaving the N-bonding intact. Therefore, three different reaction pathways have been characterized. The reactivity of the Pd−C bond in 7 has also been examined, and functionalized oxazolones can be obtained. The reaction of 7 with PhI(OAc)2 in acetic acid gives the starting oxazolone C6H4-2-Br-CH═CNC(O)OCPh (4), through the presumed oxidation of the Pd center and C−Br bond formation by reductive coupling. In contrast, the reaction of the acetate dimer 14 with PhI(OAc)2 in acetic acid gives C6H4-2-OAc-CH═CNC(O)OCPh (20) through C−O coupling. When treatment of 7 with PhI(OAc)2 is performed in MeOH or EtOH, the oxazolones C6H4-2-OR-CH═CNC(O)OCPh (R = Me (18), Et (19)) are obtained. The reaction of 7 with CO in alcohols ROH gives cleanly the oxazolones C6H4-2-CO2R-CH═CNC(O)OCPh (R = Me (21), iPr (22)) through CO migratory insertion into the Pd−C bond and further nucleophilic attack of the RO− fragment.

Monomeric, Dimeric and Polymeric W/Cu/S Clusters Based on [Et4N][Tp*W(μ3-S)3(CuBr)3] and Various Nitrogen Donor Ligands

Assembly of a family of monomeric, dimeric, and polymeric W/Cu/S clusters from a precursor cluster [Et(4)N][Tp*W(mu(3)-S)(3)(CuBr)(3)] (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) (1) and various N-donor ligands was reported. The treatment of 1 with pyridine (py) or aniline (ani) in the presence of NH(4)PF(6) afforded a cationic cluster [Tp*W(mu(3)-S)(3)Cu(3)(py)(3)(mu(3)-Br)](PF(6)) (2) and a neutral cluster [{Tp*W(mu(3)-S)(3)(CuBr)(3)}(mu(6)-Br){Tp*W(mu(3)-S)(3)Cu(3)(ani)(3)}] x 4 ani x 0.5 Et(2)O (3 x 4 ani x 0.5 Et(2)O). On the other hand, the treatment of 1 with excess 4,4'-bipyridine (4,4'-bipy) or 1,2-bis(4-pyridyl)ethylene (bpee) followed by the addition of NH(4)PF(6) led to the formation of a polymeric cluster {[Tp*W(mu(3)-S)(3)Cu(3)(4,4'-bipy)(3)(mu(3)-Br)](PF(6)) x H(2)O}(n) (4) and a neutral cluster [{Tp*W(mu(3)-S)(3)Cu(3)Br(2)}(2)(bpee)] x 0.5 CH(2)Cl(2) (5 x 0.5 CH(2)Cl(2)). Meanwhile, analogous reactions of 1 with excess 1,2-bis(4-pyridyl)ethane (bpe) or 1,3-bis(4-pyridyl)propane (bpp) in DMF under the presence of NH(4)PF(6) resulted in the formation of two polymeric clusters {[{Tp*W(mu(3)-S)(3)Cu(3)(mu(3)-Br)}(2)(bpe)(3)](PF(6))(2) x MeCN}(n) (6) and {[Tp*W(mu(3)-S)(3)Cu(3)Br(mu(3)-Br)(bpp)] x DMF}(n) (7). Compounds 1-7 were characterized by elemental analysis, IR spectra, UV-vis spectra, (1)H NMR, electrospray ionization mass spectra, and X-ray crystallography. The anion of 1 has an incomplete cubanelike [Tp*W(mu(3)-S)(3)(CuBr)(3)] structure, while the cation of 2 has a cubanelike [Tp*W(mu(3)-S)(3)Cu(3)(mu(3)-Br)] structure. Compound 3 may be viewed as having a corner-shared double cubanelike structure that consists of one [Tp*W(mu(3)-S)(3)Cu(3)(ani)(3)](2+) dication and one [Tp*W(mu(3)-S)(3)(CuBr)(3)](-) anion linked by a mu(6)-Br bridge. For 4, each [Tp*W(mu(3)-S)(3)Cu(3)(mu(3)-Br)] unit works as a pyramidal three-connecting node to connect its equivalent ones via three 4,4'-bipy bridges to yield a 2D (6,3) cationic network. Compound 5 has a dimeric structure in which two incomplete cubanelike [Tp*W(mu(3)-S)(3)Cu(3)Br(2)] cores are bridged with one bpee ligand. For 6, each dimeric [{Tp*W(mu(3)-S)(3)Cu(3)(mu(3)-Br)}(2)(bpe)(2)] unit is interconnected via a pair of bpe bridges to form a 1D zigzag cationic chain. Compound 7 has a 1D spiral chain in which each [Tp*W(mu(3)-S)(3)Cu(3)Br(mu(3)-Br)] core is interlinked by a couple of bpp bridges. The formation of 2-7 from the precursor cluster 1 through various N-donor ligands offers a new way to the design and assembly of the W/Cu/S clusters with interesting molecular and supramolecular arrays.

(3RS)-S-[1-(3-Chlorophenyl)-2-oxopyrrolidin-3-yl]thiouronium bromide

In the title molecular salt, C11H13ClN3OS+·Br−, the C—N bond lengths in the –S–C(NH2)2 fragment indicate partial double-bond character of these bonds. The constituent ions are connected by N—H⋯Br bridges into Z-shaped chains. The supra­molecular architecture of the structure can be described by being composed of these chains inter­locked by additional C—H⋯Br short contacts. An intra­molecular N—H⋯O=C bridge, as well as weak C—H⋯O hydrogen bonds, are also present in the structure.

Anion Recognition of Chloride and Bromide by a Rigid Dicobalt(II) Cryptate

The crystal structures of [Co 2L(Cl)](ClO 4) 3 ( 1), [Co 2L(Br)](ClO 4) 3 ( 2), [Co 2L(OH)(OH 2)]I 3 ( 3), and [Co 2L (1)(Cl)](ClO 4) 3 ( 4), the density functional theory calculations, as well as the binding constants of [Co 2L] (4+) toward Cl (-) and Br (-) and of [Co 2L (1)] (4+) toward Cl (-), are reported in this paper (L = N[(CH 2) 2NHCH 2(C 6H 4- p)CH 2NH(CH 2) 2] 3N, L (1) = N[(CH 2) 2NHCH 2(C 6H 4- m)CH 2NH(CH 2) 2] 3N). The rigid dicobalt(II) cryptate [Co 2L] (4+) shows the recognition of Cl (-) and Br (-) but not of F (-) and I (-), because of the size matching to its rigid cavity. We also found that the relative rigid tripodal skeleton of L than that of L (1) results in the higher affinity of [Co 2L] (4+) toward Cl (-). Magnetic susceptibility measurements of 1 and 2 indicate that the two Co(II) atoms in the cryptates are antiferromagnetically coupled through the Cl (-)/Br (-) bridge, with g = 2.19, J = -13.7 cm (-1) for 1, and g = 2.22, J = -17.1 cm (-1) for 2.

The NaDyBr4 complex; its molecular structure and thermodynamic properties

The molecular geometry, vibrational frequencies, relative stabilities, and some thermodynamic properties of different isomers of the NaDyBr4 complex were determined by computation. We investigated, to our knowledge for the first time for such a complex, the possible effect of the partially filled 4f orbitals on the molecular properties of an MLnX4 complex by using a “small core” effective core potential of the Stuttgart group. The tridentate complex, with three Na–Br bridges, was found to be the ground-state structure with the bidentate one only about 4–6 kJ/mol higher in energy. The relative abundance of these isomers changes with temperature and at the high-temperature conditions of a metal halide lamp the bidentate isomer is the more abundant isomer.

Crystal structure of dipotassium dibromo-bis(thiocyanato)mercurate(II), K2[HgBr2(SCN)2

C2Br2HgK2N2S2, hexagonal, P6ilm (no. 176), a = 12.896(1) A, c = 11.293(1) A, V= 1626.5 A, Z= 6, Rgt(F) = 0.037, wRretfF) = 0.064, T= 293 K. Source of material K2HgBr2(SCN>2 was prepared from 1 mmol of Hg(SCN>2 which was dissolved in 50 mL of water with the stoichiometric amount of KBr. The mixture was refluxed during one hour and the resulting clear solution was slowly evaporated at room temperature, * Correspondence author (e-mail: i.gautier-luneau@gren0ble.cnr5.fr) yielding millimeter sized, transparent prisms of K2HgBr2(SCN>2. Crystals were Altered off, washed with a small amount of methanol and dried at room temperature. Discussion The mercury atom is coordinated to two bromine atoms and two sulfur atoms (figure, top). The thiocyanate bonding is coherent with an HSAB explanation (Hard and Soft Acids and Bases). The metal coordination environment can be described as a distorted tetrahedron, with S-Hg-S and Br-Hg-Br angles equal to 127.3(1)° and 97.19(4)°, respectively. Among mercury compounds, the present environment is not unusual. In the thiocyanate chemistry, we already observed it in Hg3CdCl2(SCN)6 [1]. Thus, the structure could be described as a packing of [HgBr2(SCN)2]~ complex anions and potassium cations. However, due to the coordination of the SCN group, a 3D description of the crystal structure taking the potassium coordination into account seems to be a better one. The SCN~ group is coordinated to mercury through the sulphur atom and to three potassium atoms through nitrogen. This scheme is denoted IVc [2]. To our knowledge, the present tetradentate mode had never been observed. The K1 environment is a trigonal prism formed by four nitrogen and two bromine atoms. The K2 environment is an octahedron formed by three nitrogen and three bromine atoms. Finally, the K3 surrounding is an octahedron, elongated along the c axis, formed by six bromine atoms. The figure, bottom, shows the 3D interconnection of the metal cations. The most simple description is as follows. The K2 octahedra are connected through three Br bridges forming dimers. These dimers are linked through three K2-{NCS)Hg(SCN)-K2 bridges, a connection becoming very rigid through Kl-N bonds. This leads to chains parallel to the c axis:K2-[(NCS)Hg(SCN)]3-K2-[Brl]3-K2-[(NCS)Hg(SCN)]3. The linking K3-[Br2]3-K3 unit is also parallel to c. These two parallel chains are connected directly through Hg—Br2 bonds and indirectly through Brl—Hg, K1—Br2 bonds, resulting in a very compact 3D structure. Table 1. Data collection and handling. Crystal: colorless prism, size 0.07 χ 0.08 χ 0.20 mm Wavelength: Ag Ka radiation (0.56085 A) /*• 122.61 cm 1 Difftactometer, scan mode: Nonius KappaCCD, ω/φ 2BBOH'. 42° N(hkl)measured, N(hkl)miqac· 10555,1228 Criterion for /obs. N(hkl)g,: /obs > 2 a(Iobs), 870 N(param)nBiKd· 57 Programs: SIR92 [3], SHELXS-97 [4], SHELXL-97 [5], WinGX [6] Unauthenticated Download Date | 3/9/16 10:35 AM

Molecular dynamics simulation on the short-range structure of molten ZnBr 2–NaBr and ZnBr 2–KBr

The short-range structure of molten ZnBr 2–NaBr and ZnBr 2–KBr has been studied by molecular dynamics simulation. The pair potential employed was a modification of the Born–Mayer–Huggins type with the Busing approximation without the dispersion terms. The calculations were undertaken at different compositions and temperatures. The calculated pair correlation functions, the nearest-neighbor coordination numbers of Br around Zn, the numbers of Br bridging to adjacent Zn and the angular distributions Br–Zn–Br were in good agreement with the experimental results obtained by X-ray diffraction and Raman spectroscopy in which the number of bridging ZnBr 4-type tetrahedra decreased with increasing alkali bromide concentration.

Mercury(II) Compounds with 1,3-Benzothiazole-2-thione. Spectral, Thermal, and Crystal Structure Studies

Mercury(II) halides, HgX_2 (X = Cl, Br, I) react with 1, 3-benzothiazole-2-thione (btztH) in methanol solutions giving the HgX_2(btztH) and HgX_2(btztH)_2 types of compounds. Mercury(II) acetate gives the thiolato compound Hg(btzt)_2 because of the deprotonation of btztH. Hg(btzt)_2 reacts with 2, 2 -bipyridine (bipy) giving a 1:1 complex. IR and 1^H and 13^C NMR spectral studies indicate that btztH acts as a monodenatate ligand through the S thione donor atom in all complexes. The X-ray crystal structure determinations of (HgI_2(btztH))_2, HgBr_2(btztH)_2, Hg(btzt)_2 and Hg(btzt)_2(bipy) have been carried out revealing tetrahedrally coordinated mercury atom in (HgI_2(btztH))_2 and HgBr_2(btztH)_2 while in Hg(btzt)_2(bipy) 2+2 coordination is achieved through strong Hg...N(bipy) contacts. A linear coordination in Hg(btzt)_2 is not affected by the Hg...N contacts, which are longer than in Hg(btzt)_2(bipy), but still shorter than the van der Waals sum of mercury and nitrogen covalent radii. (HgI_2(btztH))_2 exists as centrosymmetrical dimer with a Hg_2I_2 bridging core. The dimeric molecules are linked by the intermolecular hydrogen bonds between the terminal iodine atom and the NH group (3.63(1) A ; ) into infinite chains along the z-axis.There are N-H...Br(bridging) intermolecular hydrogen bonds in HgBr_2(btztH)_2 joining molecules into endless chains along the x-axis. The Br(bridging) atom acts as double proton acceptor and two NH groups as proton donors (NH...Br(bridging) 3.278(9) and 3.338(7) A ; ). The mercury to sulphur and mercury to halogen bond distances in (HgI_2(btztH))_2 and HgBr_2(btztH)_2 are discussed in relation to the analogous compounds revealing strong influence of hydrogen bonds on their relative strengths as well as crystal packing requirements of the ligand. The sulphur and halogen atoms are more tightly bound to mercury implicating severe distortion of the coordination polyhedron in the structures in which they do not take part in hydrogen bonds formation. The influence of steric requirements of the ligands in Hg(btzt)_2 and Hg(btzt) _2(bipy) on the distortion of the mercury coordination polyhedra accompanied with the relative strength of Hg...N contacts is considered.

Preparation and structures of two anionic antimony (III) mixed halides, Hpy [SbBr 2Cl 2] and [Hpy] 8 [Sb 4Br 12Cl 8

Structures are reported for two anionic antimony (III) bromide chlorides, Hpy [SbBr 2Cl 2] and [Hpy] 4 [Sb 4Br 12Cl 8] , both of which are subject to halogen disorder. The first compound has an infinite chain structure in which antimony coordination is raised to six by the formation of double halogen bridges by atoms with high bromine content. The structure of the second compound is based on a distorted square of antimony atoms, again in distorted octahedral coordination. The antimony atoms are linked together by single bromine bridges and chlorine atoms or atoms with high chlorine content occupy the trans positions. The pattern of Sb–Br bridging distances suggests that the structure is derived by interconnection of two singly bridged [Sb 2Br 5Cl 4] 3− units by two bridging Br − ions.

Complexes of heterocyclic thiones and group twelve metals Part 1. Preparation and characterisation of 1:1 complexes of mercury(II) halides with 1-methylimidazoline-2(3H)-thione: the crystal structure of [( μ2-dibromo) bis( trans{(bromo) (1-methyl-imidazoline-2(3H)-thione)}mercury(II))] at 160 K

Stoichiometric (1:1) addition of aqueous alcoholic solutions of 1-methylimidazoline-2(3H)-thione (meimz2SH) to a similar series of mercury(II) halides produced crystalline complexes of empirical formula [HgX 2(meimz2SH)] (X = Cl, Br, l). The chemical formulae of the complexes have been characterised by elemental chemical analysis. IR and 11C NMR spectra indicated the presence of the thione form of the heterocyclic ligands in the complexes, as well as their thione-sulphur ligating character. The crystal structure of [HgBr 2(meinz2SH)] 2] has been determined by single crystal X-ray diffraction methods. The complex crystallises in a monoclinic unit cell with a = 7.7063(13), b = 14.471(3), c = 25.705(4) A ̊ , β = 95.114(9)°, Z = 6 (dimers) and space group P2 1/ n. The asymmetric unit consists of one general dimeric complex and half of a dimeric molecule on an inversion centre. Weak intermolecular secondary contacts occur between terminal bromine and mercury(II) atoms (Hg⋙Br=3.587−3.791 Å). These contacts link the bromo-bridged dimers into weakly associated polymeric sheets, Consequently, the mercury(II) atoms have distorted trigonal-bipyramidal coordination in this complex. The apical sites of the trigonal-bipyramidal polyhedra are occupied by terminal bromine (HgBr terminal = 2.489(2)−2.532(2) Å) and terminal thione-sulphur (HgS = 2.405(4) − 2.419(4) Å) atoms. Equatorial bromine atoms consist of the long intermolecular bromine contacts and the bridging bromine atoms (HgBr bridging = 2.659(2) − 2.859(3) Å). The latter arre also involved in the central, binuclear asymmetric Hg 2(μ-Br) 2 cores. These cores also contain long Hg⋙Hg′ contacts (3.901 and 4.041 Å) and narrow bridgingangles (HgBrHg = 89.90(5)−90.62(5)°). Further intermolecular contacts between the ligand amide (NH) groups and some of the bridging and terminal bromine atoms (NH…Br = 2.555−2.683 Å) generate an extensive H-bonded network.

Synthesis of a Heterobimetallic Ladder Polymer [(η5-C5Me5)WS3Ag2Br]n

An unusual heterobimetallic polymeric cluster [(η5-C5Me5)WS3Ag2Br]n (1), has been isolated from the reaction of [PPh4][(η5-C5Me5)WS3] with AgBr. The X-ray analysis of 1 shows that it has an unprecedented ladder-shaped one-dimensional array in which pseudohexagonal prismatic [(η5-C5Me5)WS3]2Ag4 cluster units are interconnected by two Br bridges.

Metal Complexes of 1-Oxa-4,7-dithiacyclononane.

The ligand 1-oxa-4,7-dithiacyclononane (L) and its complexes [Pd(L)Cl(2)], [Cu(L)(2)][ClO(4)].CH(3)CN, [Cu(L)Br](2), and [Co(L)(2)][ClO(4)](2).2CH(3)NO(2) have been prepared. Crystal data are as follows. For monoclinic [Pd(L)Cl(2)], C(6)H(12)Cl(2)OPdS(2): space group P2(1)/n; a = 8.464(2), b = 12.199(2), c = 10.384(2) Å; beta = 105.09(1) degrees; Z = 4; R = 0.024, R(w) = 0.033 for 1721 reflections. For monoclinic [Cu(L)(2)][ClO(4)].CH(3)CN, C(14)H(27)ClCuNO(6)S(4): space group P2(1)/n; a = 7.743(2), b = 19.515(5), c = 15.017(2) Å; beta = 102.85(2) degrees; Z = 4; R = 0.036, R(w) = 0.038 for 3124 reflections. For triclinic [Cu(L)Br](2), (C(6)H(12)BrCuOS(2))(2): space group P&onemacr;; a = 7.809(5), b = 8.880(3), c = 7.567(2) Å; alpha = 92.44(3), beta = 102.85(2), gamma = 99.30(4) degrees; Z = 2; R = 0.027, R(w) = 0.027 for 1494 reflections. For monoclinic [Co(L)(2)][ClO(4)](2).2CH(3)NO(2), C(14)H(30)Cl(2)CoN(2)O(14)S(4): space group P2(1)/c; a = 10.333(3), b = 14.293(6), c = 9.365(4) Å; beta = 100.89(3) degrees; Z = 2; R = 0.067, R(w) = 0.058 for 1517 reflections. The ligand displays a variety of conformations in these structures. The palladium complex does not undergo 1,4-heteroatom binding site fluxional processes but does dissociate in dimethyl sulfoxide. An apical Pd.O (2.968(3) Å) interaction has been detected by both NMR and X-ray studies. The Cu(I) cation is tetrahedral with a [2+2] mode of ligand coordination. [Cu(L)Br](2) involves two Br bridges between coppers and two thioether sulfurs from a ligand to complete each copper's tetrahedral coordination sphere. Surprisingly, the cyclic voltammetric behavior of the copper complexes is similar to that of 1,4,7-trithiacyclononane complexes. The cation [Co(L)(2)](2+) is pseudooctahedral with nearly regular angles at cobalt but a long (2.235(6) Å) Co-O bond due to Jahn-Teller distortion. The complex [Co(L)(2)][ClO(4)](2) is magnetically dilute and low-spin over the temperature range 5-292 K.

“Potassium Potassates” Based on Dihydrotriazinide Ligands: Syntheses, Crystal Structures, and Comparison with Other Alkali Metal Dihydrotriazinide Compounds

AbstractA series of dihydro‐s‐triazinidopotassium complexes have been synthesised and structurally characterised by X‐ray diffraction. Two of them, the sesqui‐pyridine solvate 2 and the mono‐THF solvate 3, can be classified in formal terms as “potassium potassates” in conforming to the structural pattern established previously for the sesqui‐THF solvate 1, the first reported ate of this type. Formally complex [(R2K)−] anions are linked to K+ cations in polymeric, zig‐zag chain arrangements. Solvate 3 also possesses a unique RK coordination as a direct result of having fewer solvent ligands. DMSO analogue 4 deviates from this uniformity in adopting a centrosymmetric, dimeric (OK)2 ring structure featuring both terminal and bridging DMSO ligands. The dihydro‐s‐triazinidosodium tris(THF) solvate 5 is found to be a monomer. For comparative purposes, the metal‐free, parent triazine molecule 6 has also been subjected to an X‐ray crystallographic study: it displays a 1,2‐dihydro ring setup as opposed to the 1,4‐dihydro alternative existing in the metallo examples. Triazine 6 is also found to form a N–H…Br bridge in the dimeric structure of the lithium bromide bis (THF) solvate 7, a suspected hydrolysis product from the reaction of dihydro‐s‐triazinidolithium 8 and magnesium bromide bis(ether) adduct.

Association of two incomplete cubane WS3Cu3 clusters in the crystal structures of [PPh4]2[{(C5Me5)WS3 }2Cu6(NCS)6] and [PPh4]2[{(C5Me5)WS3 }2Cu6Br6

J. Lang, H. Kawaguchi, S. Ohnishi and K. Tatsumi, Chem. Commun., 1997, 405 DOI: 10.1039/A608131B

Übergangsmetall-silyl-komplexe: XLII. Einfluβ des phosphan-liganden auf bildung, struktur und stabilität der hetero-zweikernkomplexe (CO) 3(R′ 3P)(R 3Si)Fe—ML n (M  Cu, Ag, Au, Hg)

The anionic silyl complexes Na[Fe(CO) 3(PR′ 3)SiR 3] (PR′ 3  PMe 3: SiR 3  SiMePh 2, SiMe 3; PR′ 3  P nBu 3: SiR 3  SiMePh 2; PR′ 3  PPh 2H: SiR 3  SiPh 3, SiMePh 2, SiMe 2Ph) were prepared by deprotonation of the corresponding hydrido silyl complexes. They react with CH 3I or Me 3SnCl to give mer-(CO) 3(R′ 3P)(R 3Si)FeER 3 (PR′ 3  PMe 3 and PPh 2H; ER 3  CH 3, SnMe 3), while with metal complex halides XML n , (ML n ,  AuPR 3, AgPPh 2Tol, CuPR 3 Cudppe, HgPh) the hetero-binuclear complexes mer-(CO) 3(R′ 3P)R 3Si) FeML n are obtained, which contain unbridged metal—metal bonds. Upon reaction of [Fe(CO) 3(PR′ 3)SiR 3] − with HgBr 2 in THF the trinuclear complexes [ fac-(CO) 3(R′ 3P)(R 3Si)Fe] 2Hg are obtained, from which the binuclear complexes mer-(CO) 3(R′ 3P)(R 3Si)FeHgX are formed in toluene with a second equivalent of HgX 2. X-Ray structure analyses of the octahedral complexes mer-(CO) 3(Me 3P)(Ph 2MeSi)(FAuPPh 2Tol (FeAu 252.7(3) pm), mer(CO) 3(Me 3P)(Ph 2MeSi)FeAgPh 2Tol (FeAg 258.1(1) pm) and mer-(CO) 3(Me 3P)-(Ph 2MeSi)FeHgBr) (FeHg 251.5(3) pm) show that the Fe-metal bond is cis to both the PMe 3 and the SiMePh 2 ligand. The comparison of the Fe-Si, Fe-P and Fe-M bond distances indicates that the polarity of the Fe-M bond increases from M  Hg and M  Au to M  Ag. The Fe-Hg compound is loosely dimerized via unsymmetrical Br bridges (Hg-Br 253.5(3) and 306.3(1) pm).

Structure of 6-oxo-1,6-dihydro-3,4'-bipyridine-5-carbonitrile hydrogen bromide

5-Cyano-6-oxo-1,6-dihydro-3,4'-bipyridinium bromide, C11H8N3O+.Br-, Mr = 278.11, triclinic, P1, a = 7.827 (2), b = 9.796 (2), c = 15.548 (4) A, alpha = 76.53 (2), beta = 75.40 (2), gamma = 74.36 (2) degrees, V = 1093.4 (4) A3, Z = 4, Dx = 1.689 Mg m-3, lambda (Mo K alpha) = 0.71073 A, mu = 3.70 mm-1, F(000) = 552, T = 293 K, R = 0.084 for 3989 observed reflections. The bipyridinium ions are planar, the C(2)-C(1)-C(1')-C(2') torsion angles being -3.3 (10) and 2.2 (11) degrees for molecules (1) and (2), respectively. The symmetry-independent bipyridinium ions are assembled in separate chains by hydrogen-bonding Br bridges [respective distances: Br(1)...N(3) 3.227 (6); Br(1)...N(4') 3.374 (6); Br(2)...N(3*) 3.263 (5); Br(2)...N(4'*) 3.540 (7) A] and by forming N...O hydrogen bonds between pyridinium NH groups and keto O atoms, the N(4')...O(4) and N(4'*)...O(4') distances being 2.835 (7) and 2.706 (7) A, respectively. These chains are connected by the series of stacking interactions with an average C...C distance of 3.5 A.

Synthesis and X-ray crystal structure of a mercury(II)-telluroamine complex. Monodentate behaviour by a potentially bidentate hybrid telluride ligand, 1-(NMe 2)-2-(TeC 6H 4-4-OEt)-4-MeC 6H 3

The telluroamines 1-(NMe 2)-2-(TeAr)-4-MeC 6H 3 ( 1) (Ar = 4-MeOC 6H 4 or 4-EtOC 6H 4) react with mercury(II) halides forming adducts of composition HgX 2 · 1 (X = Cl or Br). The IR, far-IR (up to 50 cm −1), 1H and 13C NMR spectra of the mercury(II) complexes indicate that the ligands ( 1) behave as monodentate donors, coordinating through tellurium only. The complexes seem to be dimers of the composition [ 1 · XHg(μ-X) 2HgX · 1]. The crystal structure of the adduct obtained from mercury(II) bromide has been determined. It reveals that the NMe 2 group does not coordinate with mercury(II) and the complex is a dimer in which two somewhat asymmetrical bromine bridges are present between the mercury atoms. The coordination environment of each mercury is almost tetrahedral [91.25(3)–118.40(4)°]. The HgBr bridging bond lengths are 2.755(1) and 2.710(1) Å.

The use of 57Fe Mössbauer spectroscopy in assigning the types of iron carbonyl units present in Fe-containing clusters

Comparison of the 57Fe Mössbauer spectra of series of related M 3, M 4 and M 5 clusters has enabled correlations to be made between the Mössbauer parameters δ (isomer shift) and q (quandrupole splitting), and the type of iron site present, viz. Fe(CO) n t, Fe(CO) m br or Fe(CO) n t(CO) m brH br (t  terminal, br  bridging ligand).