Molecular structure of ethynylbenzene from electron diffraction and ab initio molecular orbital calculations

The molecular structure and benzene ring distortions of ethynylbenzene have been investigated by gas-phase electron diffraction and ab initio MO calculations at the HF/6-31G^* and 6-3G^** levels. Least-squares refinement of a model withC _2v, symmetry, with constraints from the MO calculations, yielded the following important bond distances and angles:r _g(C _i -C _o )=1.407±0.003 Å,r _g(C _o -C _m )=1.397±0.003 Å,r _g(C _m -C _p )=1.400±0.003 Å,r _g(Cr _i -CCH)=1.436 ±0.004 Å,r _g(C=C)=1.205±0.005 Å, C _o -C _i -C _o =119.8±0.4°. The deformation of the benzene ring of ethynylbenzene given by the MO calculations, including o-C_i-C_o=119.4°, is insensitive to the basis set used and agrees with that obtained by low-temperature X-ray crystallography for the phenylethynyl fragment, C₆H₅-CC-, in two different crystal environments. The partial substitution structure of ethynylbenzene from microwave spectroscopy is shown to be inaccurate in the ipso region of the benzene ring.     

Thiokomplexe des Molybdäns Kristallstruktur eines Mischkristalls (PPh3Me)2[Mo2Br6(NO)4]/(PPh3Me)2[Mo2Br6S2(NO)2]

Thiocomplexes of Molybdenum. Crystal Structure of a Mixed Single Crystal (PPh₃Me)₂[Mo₂Br₆(NO)₄]/(PPh₃Me)₂[Mo₂Br₆S₂(NO)₂] The reactions of (PPh₄)₂MoS₄ with MoBr₄ and MoBr₂(NO)₂ resp. lead to the binuclear complexes (PPh₄)₂[S₂MoS₂MoBr₃(SMe₂)] and (PPh₄)[S₂MoS₂MoBr₂(NO)₂], in which the molybdenum atoms are linked by sulfido bridges. The preparation of (PPh₃Me)₂S₆ and (AsPh₄)₂S₇ from Na₂S₄ and PPh₃MeBr, and AsPh₄Cl, respectively, in ethanol solution is described. Disulfido briges are a feature of (AsPh₄)₂[Mo₂Br₆(S₂)₂(SMe₂)₂], which is obtained from MoBr₄(SMe₂)₂ and (AsPh₄)₂S₇. Mixed single crystals containing 2/3 (PPh₃Me)₂[Mo₂Br₆(NO)₄] and 1/3 (PPh₃Me)₂[Mo₂Br₆S₂(NO)₂] are formed in the reaction of MoBr₂(NO)₂ with (PPh₃Me)₂S₆, as shown by X-ray single crystal structure determination. The compound crystallizes monoclinic in the space group C2/c (Internat. Tab. Nr. 15) with four formula units per unit cell (2351 independent observed reflexions, R_w = 0.037). The cell parameters are a = 1603 pm, b = 1549 pm, c = 1863 pm; β = 92.2°. The complexes consist of PPh₃Me^⊕ cations and the dimeric anions [Mo₂Br₆(NO)₄]^2? and [Mo₂Br₆S₂(NO)₂]^2? which occur in the ratio 2:1. In these the molybdenum atoms are connected via MoBr₂Mo bridges of slightly different lengths (Mo? Br 265 pm and 267 pm) forming a controsymmetric double octahedron. All molybdenum atoms have two terminal bromo ligands with Mo? Br bond lengths of 258 pm and 260 pm; in the [Mo₂Br₆(NO)₄]^2? ion each molybdenum has two covalently bonded nitrosyl groups on cis-position with Mo? N bond lengths of 183 pm. In the [Mo₂Br₆S₂(NO)₂]^2? ion one of the two nitrosyl groups at each metal atom is substituted by a terminal sulfido ligand with a Mo? S bond length of 240 pm. The i.r. spectra are reported.     

Palladium(II) iminophosphine complexes

New complexes of general formula [PdCl₂(NP)] (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr, ^t Bu, NH-Me) and [Pd(NP)₂](ClO₄)₂ (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr) have been prepared by directly reacting the precursor PdCl₂(PhCN)₂ with iminophosphines (NP) in 1:1 and 1:2 molar ratios respectively. When the chloro-complex [PdCl₂(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)] was treated with CF₃SO₃Ag in MeCN, the labile complex [Pd(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)(MeCN)₂](CF₃SO₃)₂ was obtained in good yield. The reactivity of the new precursor towards a variety of neutral N- and P-donor ligands (py, PMe₂Ph, PMePh₂, PEt₃, bipy, dppe, 2-thpy) has been studied. The new complexes were characterized by partial elemental analyses and by spectroscopy (i.r., ¹H- and ³¹P-n.m.r.). The molecular structure of the aquo-complex [Pd(NP)(2-thpy)(H₂O)](CF₃SO₃)₂ has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as a chelating ligand with coordination around the palladium atom slightly distorted from square-planar geometry.     

Tetramethylammonium-calcium-triazid. Darstellung und Kristallstruktur

[N(CH₃)₄]Ca(N₃)₃,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, (x)=1.31Mgm^–3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-K-reflections, =0.469 mm^–1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.

     

Synthese und Kristallstruktur von SMe3 ⊕[MoBr4(SMe2)2]−

Synthesis and Crystal Structure of SMe₃^⊕ [MoBr₄(SMe₂)₂]^? . The title compound is obtained from MoBr₄ and excess dimethyl sulfide, forming red crystals which are only slightly sensitive to moisture. Whereas the intermediately formed adduct of MoBr₄ and SMe₂ is unstable, the stable adduct [Mo(NO)₂Br₂(SMe₂)₂] can be prepared from Mo(NO)₂Br₂ and SMe₂. According to the structural analysis by X-ray methods, SMe₃ ^⊕[MoBr₄(SMe₂)₂]^? crystallizes orthorhombic in the space group Imma with eight formula units per unit cell, the cell dimensions being a = 1578, b = 2820, c = 856 pm (1303 observed, independent reflexions). The compound consists of S(CH₃)₃^⊕ cations with S? C bond lengths of 180 pm and C? S? C bond angles of 102° and 103° resp., and anions [MoBr₄(SMe₂)₂]^?. The molybdenum atom is coordinated octahedral by four bromine atoms in equatorial positions and the two S atomes of the SMe₂ donor molecules in axial sites with Mo? S bond lengths of 254 pm.     

Estimated ionicB-coefficients from NMR measurements in aqueous electrolyte solutions

¹⁷O-NMR spin-lattice relaxation timesT ₁ of D₂O molecules were measured at 5–85°C in D₂O solutions of alkali metal halides (LiClCsCl, KBr, and KI), DCl, KOD, Ph₄PCl, NaPh₄B, and tetraalkylammonium bromides (Me₄NBrAm₄NBr) in the concentration range 0.1–1.4 mol-kg^–1 TheB-coefficients of the electrolytes obtained from the concentration dependence of relaxation ratesR ₁=1/T₁ were divided into the ionicB-coefficients by three methods: (i) the assumption ofB (K⁺)=B(Cl^–), (ii) the assumption ofB(Ph₄P⁺)=B(Ph₄B^–), and (iii) the use ofB(Br^–) obtained from a series ofB(R₄NBr). It was found that Methods (ii) and (iii) resulted in an abnormal temperature dependence of theB-coefficients of alkali metal ions and a negative values of rotational correlation times _c at lower temperatures for hydroxide and halide ions. These results suggest that the methods based on the van der Waals volume are not adequate for the ionic separation of NMRB-coefficients. From the analysis using the assumption ofB(K⁺)=B(Cl^–), it was found that D₃O⁺, OD^–, and Me₄N⁺ ions are the intermediates between structure makers and breakers, and that the hydrophobicity of phenyl groups is weaker than that of alkyl groups due to the interactions between water molecules and -electrons in phenyl groups.     

Magnitudes of the inductive effects of the nitro and nitrate groups

Conclusions The value of the induction constant for the nitrate group has been calculated (^*(–CH₂ONO₂)=1.34) and the value of the induction constant of the nitro group has been refined (^*(–CH₂NO₂)=1.73).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1488–1490, August, 1966.     

Rhenium(V) complexes with vinyl amides

Summary The reactions oftrans-ReOCl₃(PPh₃)₂ with vinyl amides such as RCOCH=C(R)NH₂, where R = CH₂CH₂CO₂H and R = Ph and C₆H₁₃; or R = Me, CH₂CH₂CO₂Me and R = Ph, give complexes of the type ReOCl₂-[RC(O^–)=CHC(R)=NH]PPh₃, the coordination geometry of which have been deduced from i.r. and¹H n.m.r. spectroscopic data.     

The dissociation of phosphoric acid in NaCl and NaMgCl solutions at 25°C

The pK ₁ ^* , pK ₁ ^* and pK ₃ ^* for the dissociation of H₃PO₄ have been measured in NaCl solutions from 0.5 to 6m at 25°C. The results have been used to evaluate Pitzer interaction parameters (NaClH₂PO₄)=–0.028±0.005, (NaH₃PO₄)=–0.075±0.025, (HPO₄Cl)=0.105±0.009, (PO₄Cl)=–0.59±0.02 and (NaClHPO₄)=–0.003±0.004, (PO₄NaClH)=0.110±0.008. These parameters yield values of pK ₁ ^* , pK ₂ ^* and pK ₃ ^* in NaCl that agree with the measured values with average deviations of ±0.04, ±0.03 and ±0.05 in pK ₁ ^* . Measurements of pK ₁ ^* and pK ₂ ^* were also made in NaMgCl solutions. These results have been used to evaluate ^(O)(MgH ₂ PO ₄)=–3.55±0.07,⁽¹⁾(MgH ₂ PO ₄=–16.9±0.03, ^(O)(MgH ₂ PO ₄=–17.5±0.03 and ⁽¹⁾(MgH ₂ PO ₄)=27.4±0.8 at 25°C. The results for pK ₂ ^* in NaMg–Cl solutions were also used to calculate log K _MX ^* =3.2±0.1 for the formation of the ion pair MgHPO ₄ ^o .     

Die Bromokomplexe von Molybdän(IV) [MoBr6]2⊖ und [Mo2Br10]2⊖. Die Kristallstruktur von (PPh3Me)2[MoBr6] · 2 CH2Br2

Bromo Complexes of Molybdenum(IV) [MoBr₆]^2? and [Mo₂Br₁₀]^2?. Crystal Structure of (PPh₃Me)₂[MoBr₆] · 2 CH₂Br₂ The bromomolybdates(IV) (PPh₃Me)₂[MoBr₆] · 2 CH₂Br₂ and (PPh₄)₂[Mo₂Br₁₀] are obtained by reactions of molybdenum tetrabromide with PPh₃MeBr and PPh₄Br, respectively. They form black-brown, hydrolysis sensitive crystal powders. The crystal structure of (PPh₃Me)₂[MoBr₆] · 2 CH₂Br₂ was determined by X-ray diffraction (2376 independent observed reflexions, R = 0.082). Crystal data: a = 1024, b = 1131, c = 1179 pm, α = 108.2°, β = 106.8°, γ = 99.0°, space group P1 , Z = 1. The compound consists of PPh₃Me⁺ ions, CH₂Br₂ molecules and nearly octahedral [MoBr₆]^2? ions with MoBr bond lengths between 252.7 and 254.0 pm.     

Synthesis, crystal structure, spectroscopic and thermal properties of [Et4N][Ta6Br12(H2O)6]Br4·4H2O (Et=ethyl)—A new compound with the paramagnetic [Ta6Br12] cluster core

A new hexanuclear cluster compound, [Et₄N][Ta₆Br₁₂(H₂O)₆]Br₄·4H₂O (Et=ethyl) (1), with the paramagnetic [Ta₆Br₁₂]³⁺ cluster entity, was synthesized and characterized by elemental and TG/DTA analyses, IR and UV/Vis spectroscopy and by a single-crystal X-ray diffraction study. The presence of the paramagnetic [Ta₆Br₁₂]³⁺ unit was confirmed also by the room-temperature magnetic and EPR measurements. The compound crystallizes in the tetragonal I4₁/a space group, with a=14.299(5), c=21.241(5) Å, Z=4, R₁(F)/wR₂(F²)=0.0296/0.0811. The structure contains discrete [Ta₆Br₁₂(H₂O)₆]³⁺ cations with an octahedron of metal atoms edge-bridged by bromine atoms and with water molecules occupying all six terminal positions. The cluster units are positioned in the vertices of the three-dimensional (pseudo)diamond lattice. The structure shows similarities with literature reported structures of cluster compounds crystallizing in the diamond space group.     

Molecular Structure of Samarium Dibromide

The molecular structure of samarium dibromide has been studied by electron diffraction at T _exp = 1250(50) K. The molecule has C_2v symmetry; the internuclear distance R_g(Sm–Br) = 274.5(5) pm; _g =131(6)°. The vibration frequencies were estimated from the experimental values of the mean square vibration amplitudes.     

Molecular Structure of Neodymium Diiodide

The molecular structure of neodymium diiodide was investigated in an electron diffraction study at T _exp = 795(10) K. The molecule has C_2v symmetry; the internuclear distance R_g(Nd–I) is 297.3(3) pm and _g = 132(3)°. The vibration frequencies were estimated from the experimental values of the root-mean-square vibration amplitudes.     

π-Complex of Cu(I) Chloride with 1-Allyloxybenzotriazole CuCl · C<Subscript>6</Subscript>H<Subscript>4</Subscript>N<Subscript>3</Subscript>(OC<Subscript>3</Subscript>H<Subscript>5</Subscript>)

Single crystals of CuCl · C₆H₄N₃(OC₃H₅)(I) are synthesized by ac electrochemical method from Cu(II) chloride and 1-allyloxybenzotriazole in ethanol solution and their unit cell parameters are determined: space group P2₁/a a=11.583(4) , b=11.443(7) , c=8.620(4) , =108.77(3)°, V=1082(2) ³, R(F)=0.0366, R _w (F)=0.0396 for 1095 reflections. In the structure of -complex I, inorganic fragment Cu₂Cl₂ forms centrocymmetric parallelogram. A molecule of 1-allyloxybenzotriazole acts as a bridge, which is bonded to the Cu atoms of two inorganic dimers through the C=C bond of the allyl group and to the N atom of a triazole ring. Owing to this bridging function, the ligand molecules form zigzag organometallic layers. The trigonal-pyramidal coordination sphere of a metal atom includes two Cl atoms and the C=C group. The structural motif of complex I significantly differs from that of the previously studied 2CuCl · C₆H₄N₃(OC₃H₅) and resembles the motif of a bromide analog Cu₂Br₂ · [C₆H₄N₃(OC₃H₅)]₂.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 364–369.Original Russian Text Copyright © 2005 by Goreshnik, Myskiv.     

Complexes of tris(o-phenanthroline)nickel(II) and copper(II) bromide with dithiocarbamates derived from α-amino acids

Complexes of 1,10-o-phenanthroline (o-phen)-Ni^II and Cu^II with dithiocarbamates derived from -amino acids (glycine, phenylalanine, alanine, methionine and tryptophan) were synthesized and characterized by chemical analysis, spectral and thermal studies and by biological screening; the complexes are non-electrolytes. The empirical formula are [Ni(o-phen)₂(aadtc)] and [Cu₂(o-phen)₂(phaladtc)(H₂O)₂Br₂] where, aadtc = glycinyl-, phenylalaninyl-, alaninyl-, methioninyl- and tryptophanyldithiocarbamate and phaladtc = phenylalaninyldithiocarbamate. The structure of these complexes is probably octahedral. Molecular association through hydrogen bonding between the —NH and the carboxylate groups is proposed for the Ni^II complexes. The Cu^II complex is dimeric with the phenylalaninyldithiocarbamate acting as a bridge.     

Reactions of the Dirhenium(II) Complexes Re2X4(μ-dppm)2 (X=Cl, Br; dppm=Ph2PCH2PPh2) with Isocyanides. XXII. A Comparison of Mixed Carbonyl–Isocyanide Complexes with Those Formed by Re2Cl4(μ-dcpm)2 (dcpm=Cy2PCH2PCy2)

The reactions of the electron-rich triply bonded dirhenium(II) complex Re₂Cl₄(-dcpm)₂ (dcpm=Cy₂PCH₂PCy₂) with the isocyanide ligands XylNC (Xyl=2,6-dimethylphenyl) and t-BuNC afford the complexes Re₂Cl₄(-dcpm)₂(CNXyl) and Re₂Cl₄(-dcpm)₂(CN-t-Bu)₂ which in turn react with CO to give salts of the [Re₂Cl₃(-dcpm)₂(CO)₂(CNXyl)]⁺ and [Re₂Cl₃(-dcpm)₂(CN-t-Bu)₂(CO)]⁺ cations which exist in different isomeric forms. This chemistry is compared with that developed previously for the analogous complexes derived from Re₂Cl₄(-dppm)₂.     

Accurate lifetime measurements of the 2p 3d 1 D 0 and 2p 3d 3 P 2 0 levels in N II with the beam-foil-laser method

We have obtained accurate values for the radiative lifetimes of the 2p 3d ¹ D ⁰ and 2p 3d ³ P ₂ ^o levels in NII by the cascade-free beam-foil-laser spectroscopy method. Our results are (2p 3d ¹ D ⁰)=0.346±0.012 ns and (2p 3d ³ P ₂ ^o )=0.457±0.020 ns. Comparison of these results with experimental and recent theoretical lifetimes reported previously is also made.Senior Research Associate of the Belgian FNRS     

Thermodynamics of bolaform electrolytes. I. Heat capacities and enthalpies in H2O and D2O

The partial molal heats of solution at infinite dilution, H _s ^o , of bolaform salts [Et₃N(CH₂)_nNEt₃]Br₂ and [allyl₃N(CH₂)_nNallyl₃]Br₂, have been measured in H₂O and D₂O at 25°C using a solution calorimeter. The values of H _s ^o were endothermic for almost all of the compounds studied. Values of H _s ^o were obtained as a function of temperature for several homologs in H₂O and D₂O. Positive C _p ^o values obtained from least-squares analyses of the H _s ^o vs T data show an almost linear dependence on the number of methylene groups between the nitrogen centers. Whereas the enthalpy of transfer from H₂O to D₂O is small and endothermic, relatively large positive heat capacity of transfer data, increasing with increased hydrocarbon content of the salts, were observed. The ability of the bolaform cation to act as a model for cation-cation pairing in R₄NX systems is discussed.     

Zur Polymorphie von In5Br7

On the Polymorphism of In₅Br₇ The existence of two polymorphs of In₅Br₇ has been proved by single crystal structure determinations. In₅Br₇ (tP192) crystallizes with the tetragonal space group P4₁2₁2 and lattice parameters a_t = 1318.9(5) pm and c_t = 3723.8(9) pm (293 K). Concerning monoclinic In₅Br₇ (mC192), the centrosymmetric space group C2/c with lattice parameters a_m = 1867.3(4) pm, b_m=1867.0(5) pm, c_m = 1918.0(7) pm, and β_m = 103.96(2)° (293 K) has been confirmed. Both modifications of In₅Br₇ are built up from layers of the same type. These layers with a thickness of about 930 pm consist of structure fragments [InBr₂]⁴⁺ and [InBr₁₂]^4–. The anion is composed of two ethan‐like [InBr₆]^2– units, which contain In–In bonds. The stacking sequence of the layers with symmetry C 1 2 (1) differs for the two modifications of In₅Br₇. The tetragonal form is generated by applying a 4₁ screw axis; the monoclinic polymorph is formed by introducing inversion centers between the layers. The adequate name of In₅Br₇ = In[InBr₆]Br is triindium(I)‐hexabromodiindate(II)(In–In)‐bromide.     

Coordination chemistry of alkali and alkaline earth cations: Crystal structure of rubidium (benzo-15-crown-5)2NO3·H2O

The complex Rb(B15C5)₂NO₃·H₂O is monoclinic,P2_1/c,a=12.695(3),b=19.471(3),c=12.991(2)Å, =99.60(2)^o,V=3166 ų,D _c =1.473 g/cm³ (163 K),D _c =1.434 g/cm³ (298 K),D _o =1.44 g/cm³ (298 K),T=163K,Z=4, MoK=0.71069 Å, 2(4^o–53^o), =16.43 cm^–1,F(000)=1424. FinalR for the 4588 observed reflections (F>3) is 0.062. All ten oxygens of the two benzo-crowns are shown to coordinate to the rubidium ion (Rb...O,2.92 to 3.07 Å) forming a charge-separated sandwich. The nearest nitrate oxygen is displaced 6.51 Å from the rubidium ion and is hydrogen bonded to a water molecule. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82028 (28 pages)