The crystal and molecular structure oftrans-Di(methylsulphito)bis-(triphenylphosphine)platinum(II)

Summary The crystal and molecular structure oftrans-di(methylsulphito)bis(triphenylphosphine)platinum(II), Pt(SO₃Me)₂ (PPh₃)₂, derived from the reaction of Pt(PPh₃)₂ (O₂) with SO₂ in MeOH and in the presence of sodium tetraphenylborate(III), has been determined from diffractometer data. The complex crystallizes in the space group P ¯1- (C_i ¹) with one molecule in a unit cell of dimensionsa = 9.744(2) Å,b = 10.062(3) Å,c = 11.153(2) Å; = 68.59(2)°, = 82.69(2)° and = 62.25(2)°. Leastsquares refinement has led to a value of the conventional R index (on F) of 0.031 for the 3308 reflections having F²>3(F₀ ²). The complex is a typical square-planar platinum(II) complex with the platinum atom lying on a crystallographically imposed centre of symmetry. The important structural parameters are Pt-P 2.369(1) Å, Pt-S 2.308(1) Å, and the oxygen atoms complete an approximate tetrahedron about the sulphur atoms with S-O 1.448(5) Å and S-O(Me) 1.620(5) Å.     

Crystal structure oftrans-ethyl(1,5,6-trimethylbenzimidazole)-bis(dimethylglyoximato)cobalt(III). Relationships between structural and spectroscopic properties in compounds of the general formulae [Co(dmgH)2(R)(1,5,6-Me3Bzm)]

Summary The synthesis and x-ray crystal structure oftrans-[Co(dmgH)₂(Et)(1,5,6-Me₃Bzm)] where dmgH=dimethylglyoximate(–1), and 1,5,6-Me₃Bzm=1,5,6-trimethylbenzimidazole, is reported. The compound C₁₉H₂₆N₆O₄Co is monoclinic, space group P2₁/n;a=11.700(4);b=24.205(6);c=8.500(3) Å and =101.63(3)°. D(calcd) 1.299 g cm^–3; Z=4 and R=0.066 for 2359 independent reflections. Comparison of Co-N(axial ligand) bond lengths for compounds of general formulaetrans-[Co(dmgH)₂(R)(L)], with L=pyridine or 1,5,6-trimethylbenzimidazole and R=CH(CN)Cl, CH₂NO₂, Me, Et,i-Pr, cyclo-hexyl or adamantyl is made. The Co–N(1,5,6-Me₃Bzm) bond lengths of the trimethylbenzimidazole derivatives show a fairly linear relationship with the electronic parameter of the axial R group, derived from the¹³C-n.m.r. spectra of their pyridine analogues. The influence of steric effects on the properties of these Co^III compounds is discussed.     

Interaction between cobaltocenium and decamethylcobaltocenium salts and Ph3ELi (E = Si,Ge, Sn)

Reactions of cobaltocenium salts [(C₅R₅)₂Co]PF₆ (R = H, Me) with Ph3ELi (E = Si, Ge, Sn) and with Ph₂SbLi mainly follow two pathways (nucleophilic addition and one-electron reduction), yielding cobalt cyclopentadiene-cyclope ntadienyl complexes (⁴-Ph₃EC₅R₅)(⁵-C₅R₅)Co (R = H, E = Si, Ge, Sn; R = Me, E = Si) and cobaltocenes (C₅R₅)₂Co (R = H, Me), respectively. The contribution of nucleophilic addition of Ph₃ELi decreases in the order of elements Si > Ge > Sn and when hydrogen atoms are replaced by methyl groups in the initial cobaltocenium salt. Thermal decomposition of cobalt cyclopentadiene-cyclopentadienyl complexes results in substituted cobaltocenes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 10, pp. 2557–2560, October, 1996.     

Synthesis and X-ray crystal structure of tetraethylammonium bis[1,2-di(carbomethoxy)ethane-1,2-dithiolato]oxotechnetate(V)

Summary The (NEt₄)⁺[TcO{SCH(CO₂Me)CH(CO₂Me)}₂]^– compound has been prepared from technetium(V) gluconate and characterized by single crystal x-ray structural analysis (R factor=0.065).The compound crystallizes in the monoclinic space groupP2₁/c witha=12.722(3),b=13.820(4) andc=18.213(5) Å, =107.13(4)° andZ=4. In the complex the technetium atom is close to the center of the base of a square pyramid in which the oxo oxygen is at the apex and the four sulfur atoms form the basal plane. The Tc-S distances average 2.316 Å. The Tc=O distance is 1.672(6) Å. Considerations about the osteotropic behaviour of DMSA labelled with⁹⁹Tc are deduced from the reported results.     

Hydrogen peroxide oxidation of di(hydroxo)platinum(II) species in carboxylic acids

A facile procedure for synthesizing the mono(hydroxo)tris(carboxylato)platinum(IV) species has been achieved. The reaction of [Pt^II(OH)₂(dmpda)] (dmpda=2,2-dimethyl-1,3-propanediamine) with a 30% aqueous solution of H₂O₂ in the presence of a carboxylic acid produces a stable [Pt^IV(OOCR)₃(OH)(dmpda)] (R=Me, Et) complex in high yield. The crystal structures of [Pt^IV(OOCMe)₃(OH)(dmpda)] . H₂O (triclinic P1 bar, a=8.761(2) Å, b=9.245(3) Å, c=10.659(2) Å, =106.25(2)°, =93.90(2)°, =98.92(2)°, V=813.1(3) ų, Z=2, R= 0.0474) and [Pt^IV(OOCEt)₃(OH)(dmpda)] (monoclinic P2₁/c, a=12.777(4) Å, b=10.514(2) Å, c=14.971(3) Å, =107.40(2)°, V=1919.2(8) ų, Z=4, R=0.0611) show that the hydroxyl group has been selectively positioned at an axial site. The intramolecular hydrogen bond between the OH and C=O moiety exists (O(H)...=C, 2.83 Å for [Pt^IV(OOCMe)₃(OH)(dmpda)] · H₂O; 2.72 Å for [Pt^IV(OOCEt)₃(OH)(dmpda)]. Formation of the axial-mono(hydroxo)tris(carboxylato)platinum(IV) species may be ascribed to a combination of `reactive-equatorial effects' with `cis-addition' in the carboxylic acid.     

Molecular structure of the cobalt(ii) chloride complex with triphenyl-N-(2-pyrimidyl)phosphineimine

An X-ray structural study of the cobalt(ii) chloride complex with triphenyl-N-(2-pyrimidyl)phosphineimine has been performed (automatic diffractometer, Mo-–K , 2916 observed reflections, the heavy-atom method, the least squares method in anisotropicisotropic approximation toR=0.043). The crystals are monoclinic,a=15.979(6) Å,b=17.391(6) Å,c=14.976(6) Å, =104.21(2)°,V=4034(5) ų,d _calc=1.384 g cm^–3,Z=4, space groupP2₁/c. The Co atom has a distorted tetrahedral coordination by two Cl atoms (2.268(2) Å and 2.278(3) Å) and two N atoms (2.030(4) Å and 2.025(5) Å) of the two pyrimidine heterocycles. The Cl-Co-Cl and N-Co-N bond angles are equal to 107.7(1)° and 123.4(2)°, respectively. Additional weak coordination of the Co atom by two N atoms of the imine groups [Co...N 2.982(4) Å and 3.045(4) Å] is also observed in the molecule of the complex, and this coordination changes the nearest environment of the Co atom to distorted octahedral coordination. The lengths of the phosphorus-imine P=N bonds are 1.596(6) Å and 1.585(6) Å. The results obtained are compared with previous structural investigations of similar complexes of transition metals with iminophosphoranes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1203–1206, July, 1993.     

The crystal and molecular structure of a dinuclear copper(II) complex of a Robson-type macrocycle, [Cu2(C26H30N4O2)(H2O)2](BF4)2

Summary The crystal structure of the dinuclear complex [Cu₂(C₂₆H₃₀-N₄O₂)(H₂O)₂](BF₄)₂ was determined by x-ray crystallography. The crystals are triclinic, P¯1, witha = 10.945(5),b = 8.703(5),c = 8.495(5) Å, = 103.86(3)°, = 105.73(3)°, = 85.77(3)°, V = 756 ų D_c = 1.65 g cm^–3 for Z = 1. The copper(II) atoms are 5-coordinate and square-pyramidal. Selected bond distances are: Cu-N, 1.91 Å (mean); Cu-O(base) = 1.90(1) and 1.91(1) Å; Cu-O(apical) = 2.47(1) Å; There are O(water)-H ... F interionic hydrogen bonds in the structure. The Cu .. Cu distance is 2.847 Å.     

A novel asymmetrical phosphine tetracobalt complex ofo-Mercaptophenol: Synthesis,structure, and properties of Co4mp4(Hmp)(PBu 3 n )3 (H2mp=o-Mercaptophenol)

Complex Co₄mp₄(Hmp)(PBu ₃ ⁿ )₃ (1) (H₂mp=o-Mercaptophenol) was obtained from the reaction of CoCl₂ and H₂mp in the presence of PBu ⁿ ₃ and NaOMe with restricted oxidation. X-ray crystallographic data: triclinic, space group ,a=15.657(5) Å,b=20.469(8) Å,c=12.383(3) Å,=93.59(3)°, =112.45(2)°, =93.65(3)°,V=3648.7 ų,Z=2,D _c =1.33 g/cm³;R=0.065. The molecule consists of four cobalt atoms unsymmetrically bridged by S or S and O atoms from four of the five mp ligands. The fifth mp is terminally chelated to Co(4) which is in a distorted trigonal bipyramidal geometry, while Co(1)-Co(3) are square pyramidal. Atom Co(2) is bonded to Co(1) and Co(3) (average distance 2.632 Å) with strong interactions while Co(4) is only loosely connected to Co(1) (3.402 Å) and Co(3) (2.956 Å) through oxygen bridges and a hydrogen bond. The different coordination environments O₂S₂P, S₄P, and O₄S of the cobalt atoms make the molecule highly asymmetrical. XPS fitting data confirm the difference of the Co atoms. FABMS data indicate the possible fragmentation routes. The complex is paramagnetic with _eff=5.2 _B.     

Copper(II) Complexes with N-(3-Hydroximino-2-methylbutan-2-yl)methylamine (HL): Synthesis and Properties. Crystal and Molecular Structures of [Cu(HL)Cl2] and [Cu(HL)(H2O)2SO4]n

Paramagnetic copper(II) complexes with N-(3-hydroximino-2-methylbutan-2-yl)methylamine (HL), namely, Cu(HL)Cl₂(I), Cu(HL)(SO₄) · 2H₂O (II), and Cu(HL)(NO₃)₂(III), were obtained. The crystal structures of I and II were determined. The blue crystals of these compounds are monoclinic. For I(C₆H₁₄Cl₂CuN₂O): a = 8.820(1) Å, b = 6.511(1) Å, c = 18.255(2) Å, = 92.86(1)° V = 1047.0(2) ų, space group P2₁/c, _calcd = 1.679 g/cm³, Z = 4 for R ₁ = 0.0250; for II(C₆H₁₈CuN₂O₇S): a = 9.999(2) Å, b = 9.927(2) Å, c = 12.963(3) Å, = 106.37(3)°, V = 1234.5(4) ų, space group P2₁/c, _calcd = 1.753 g/cm³, Z = 4 for R ₁ = 0.0324. Crystals of I have a molecular structure. The Cu coordination polyhedron is a square bipyramid (2N + 2Cl + Cl + Cl) due to additional contacts with two Cl atoms from the neighboring molecules. Structure II is built from polymeric chains. The environment of the Cu atom is a distorted cis-octahedron (2N + 2O(H₂O) + 2O(SO₄)). Complexes I–IIIare characterized by IR and EPR spectroscopy.     

Inclusion complexes of the natural product gossypol. Clathrate type inclusion complexes of gossypol with carbonyl group containing guests

The crystal structures of 2:1 inclusion complexes of gossypol with methyl propionate (GPMEP) and ethyl acetoacetate (GPEAA) have been determined by X-ray structure analysis. The crystals of GPMEP, C₃₀H₃₀O₈l/2 C₄H₈O₂, are monoclinic, space groupC2/c,a=11.079(3),b = 30.724(7), c = 16.515(5) Å, = 90.46(2)°,V = 5621(3) Å,Z = 8,D _x = 1.33 g cm^–3. The structure has been refined to the finalR value of 0.059 for 1899 observed reflections. The crystals of GPEAA, C₃₀H₃₀O₈l/2 C₆H₁₀O₃, are monoclinic, space groupC2/c,a=11.095(2),b=30.604(9),c = 16.955(5) Å, = 88.27(2)°,V = 5754(3) Å,Z = 8,D _x = 1.35 g cm^–3. The structure has been refined to the finalR value of 0.056 for 2502 observed reflections.In contrast to previously investigated inclusion complexes of gossypol the host molecules do not form centrosymmetric dimersvia hydrogen bonds. In the crystal structures the racemic gossypol is separated into enantiomers forming alternating bimolecular layers. Nearly perpendicular to these chiral bilayers run elongated cavities enclosed on each side by layers of opposite chirality. The surface of these layers is hydrophobic, the polar groups are hidden inside the layer. Guest molecules which are hydrogen bonded to the host are included in cylindrically shaped cavities. Possible hydrogen bonds between host and guest are analysed for this isostructural class of complexes.     

Synthesis,spectral and magnetic studies on mixed-ligand complexes M(DIAFO)2(NCS)2 and M(DIAFH)2X2 (M = FeII,CoII, NiII). The crystal structure of Co(DIAFO)2(NCS)2

Summary A series of mixed-ligand complexes of group VIII metals, M(DIAFO)₂(NCS)₂ and M(DIAFH)₂X₂ (M = Fe^II, Co^II, Ni^II, X = NCS^–, Cl^–) with the 3,3-bridged derivative of 2,2-bipyridyl (bipy) (1) were prepared, where DIAFO (2) and DIAFH (3) are 4,5-diazafluoren-9-one and 4,5-diazafluoren-9-hydrazone, respectively. These complexes were investigated by i.r., u.v.-vis-near i.r. spectroscopy and by variable-temperature magnetic susceptibility measurements. The electronic spectra show that the two ligands exert a field strength far removed from the Fe^II cross-over value. All the complexes are paramagnetic, following the Curie-Weiss law in the 77–300 K range. A typical crystal structure of Co(DIAFO)₂(NCS)₂ for these compounds was determined with orthorhombic, space group Pcan, a = 10.377(5) Å, b = 13.289(6) Å, c= 16.629(7) Å, V = 2293(2) ų, D _c = 1.563 g cm^–3, F(000) = 1091.74, Z = 4, R = 0.043, R = 0.047. Steric effects are thought to be operative in both ligands studied, but are weaker than those of the typical bidentate diimine ligand bipy.Author to whom all correspondence should be directed.     

Solid-state structure and conformation of (Z)-2-(phenylbenzylidene)-3-quinuclidinone,an intermediate in the synthesis of quinuclidine derivatives

(Z)-2-(2-phenylbenzylidene)-3-quinuclidinone, C₂₀H₁₉NO,M _r =300.47D crystallizes in the monoclinicP2₁/c space group witha = 6.9809(2) Å,b=19.0523(2) Å,c = 11.7733(1) Å,=100.92(2)°,V=1537.5(3) ų,Z=4,D _c = 1.298 g/cm³,D _x =1.29 g/cm³ (flotation). Diffractometric data, using CuK radiation,=1.54178 Å, were collected on plate-like crystals. The structure, solved by direct methods was refined to a final R value of 0.037 for the 2645 observed reflections withF _o >3.0(F _o ). The molecule shows a trans conformation around the double bond. The quinuclidine and the diphenyl moieties present deformations in their geometric and conformational parameters due to the need of releasing intramolecular strains and/or nonbonded interactions.     

Antimony(III) Chloride Complexes with Benzylpyridines: Synthesis and Luminescence. Crystal Structure of Bis(2-benzylpyridinium) Pentachloroantimonate(III)

The antimony(III) chloride complexes with 2- and 4-benzylpyridine were synthesized and studied using elemental analysis, X-ray diffraction analysis, IR spectroscopy, and luminescence spectroscopy. The crystal structure of bis(2-benzylpyridinium) pentachloroantimonate(III) was determined. The crystals are triclinic: a = 9.628(1) Å, b = 15.284(2) Å, c = 19.174(2) Å, = 99.962(2)°, = 101.233(2)°, = 99. 216(2)°; Z = 4, (calcd) = 1.591 g/cm³, space group P , R = 0.0358. The structure consists of polymeric chains of [Sb₂Cl₁₀]^4n– _n anions and [C₁₂H₁₁NH]⁺ cations combined into a framework by the N–H···Cl hydrogen bonds. The electronic and geometrical factors responsible for a relatively low intensity of the luminescence emitted by the complexes of antimony(III) chloride with 2- and 4-benzylpyridine at 77 K are discussed.     

Complexation with hydroxy host compounds,part 5. Structures and thermal analyses of 1,2,3,4,5-pentaphenylcyclopenta-2,4-dien-1-ol and its inclusion compounds with water and dimethylsulphoxide

The crystal and molecular structures of the title host compound (I), C₃₅H₂₆O, and its inclusion complexes with water (II), C₃₅H₂₆O·H₂O and dimethylsulphoxide (III), C₃₅H₂₆O·C₂H₆OS are reported. (I) is monoclinicC2/c,a = 9.725(1),b = 20.031(3),c = 26.545(3) Å, = 90.60(1)⁰,V = 5170 ų,Z = 8; (II) is triclinic, ,a = 10.206(1),b = 10.324(2),c = 14.425(2) Å, = 101.68(1), = 89.92(2), = 116.34(1)⁰,V = 1327 ų,Z = 2; (III) is monoclinicP2₁/n,a = 17.832(5),b = 10.109(3),c = 17.901(5) Å, = 111.93(2)⁰,V = 2993 ų,Z =4. The structures were solved by direct methods and refined to final residuals of 0.045, 0.048, and 0.071, respectively. Thermal analysis of the complexes corroborates the crystallographic results.     

The crystal structure of tetraphenylarsonium tricyanooxopyridine-2-carboxylatotungstate(IV) dihydrate

Summary The structure of (AsPh₄)₂[WO(CN)₃(Pic)] · 2H₂O has been determined from three dimensional x-ray data. The cell dimensions are:a=17.699(8),b=13.546(6),c= 13.590(6) Å, =117.39(8), = 71.54(7) and = 115.04(8)°, space group P¯1, Z = 2, The structure was solved from 5279 observed reflections. The anisotropic refinement converged to R = 0.060.The [WO(CN)₃(Pic)]^2–-ion is a distorted octahedron. The structure indicates that the aqua group in [WO(CN)₄(H₂O)]^2– was displaced by an oxygen atom of the carboxylate of 2-picolinate, while a cyanide ligand was substituted by the pyridine nitrogen atom. Themer-arrangement of the three cyanide ligands has two normaltrans W-C_av = 2.17(2) Å bond distances and a significant shorter W-C = 2.042(18) Å bond trans to the W-N [2.188(18) Å] bond. The W=O and W-O bond lengths are 1.676(9)Å and 2.171 Å, respectively.     

Synthesis and crystal structure of (2-methoxyethyl)-cyclopentadienyl titanium complexes

Summary New substituted cyclopentadienyl titanium complexes, Cp'TiCl₂ (1), Cp'CpTiCl₂ (2) and Cp'TiCl₃ (3) (Cp'=(2-methoxyethyl)cyclopentadienyl) have been synthesized; complexes (1) and (3) have been studied by x-ray diffraction. Complex (1) forms red-plate crytals which belong to the monoclinic space group p2₁/a with unit cell parameters:a 11.431(1),b 7.116(1),c 21.13514 Å, 99.50(1)°, V=1695.5(4)ų and Z=4. The structure of (1) is refined to the final R of 0.044 for 1833 soserved reflections. The orange octahedral crystals of (3) are monoclinic, space group P2₁/c with unit cell paranreters:a 7.896(2),b 11.015(5),c 25.213(6)Å, 92.13(2)°, V=2192(1) ų and Z=8. Refinement for 1714 observed reflections gives the final R of 0.090. The crystal sinceture of (3) shows that the ethereal oxygen atom in the side chain on the Cp ring coordinates with the ratenum atom to form a chelate ring.     

The structures of 1-(2′-hydroxybenzoyl)piperidine and 4-(2′-hydroxybenzoyl)morpholine

1-(2-hydroxybenzoyl)piperidine, C₁₂H₁₅NO₂, orthorhombic, Pbc2₁-C _2v ⁵ ;a=9.529 (1),b=10.001 (1),c=11.652 (1) Å;Z=4. The structure was determined from 1 510 single crystal X-ray data by direct methods and the refinement of the structure parameters yieldedR=0.040. There is one molecule in the asymmetric unit.4-(2-hydroxybenzoyl)morpholine, C₁₁H₁₃NO₃, orthorhombic, P2₁2₁2₁-D ₂ ⁴ ;a=13.006 (1),b=17.258 (2),c=9.125 (1) Å;Z=8. The structure parameters of the isotypic compound 4-(2-hydroxythiobenzoyl)morpholine were used in a starting set of refinement; finallyR=0.054 was obtained for 1 900 single crystal X-ray data. There are two molecules in the asymmetric unit.In both compounds the hydrogen atoms could be located by means of differenceFourier summations. The intermolecular hydrogen bonds with O ... O distances of 2.649 (2) Å for the piperidine derivate and 2.688 (3) resp. 2.754 (3) Å for the morpholine derivate are typical for intermediate bond strengths.

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Die Strukturen von 1-(2-hydroxybenzoyl)piperidin und 4-(2-hydroxybenzoyl)morpholin

Zusammenfassung 1-(2-hydroxybenzoyl)piperidin, C₁₂H₁₅NO₂, orthorhombisch, Pbc2₁-C _2v ⁵ ;a=9.529 (1),b=10.001 (1),c=11.652 (1) Å;Z=4. Die Struktur wurde aus 1 510 Einkristallröntgendaten mittels direkter Methoden bestimmt; die Strukturverfeinerung ergabR=0.040. Es ist ein Molekül in der asymmetrischen Einheit.4-(2-hydroxybenzoyl)morpholin, C₁₁H₁₃NO₃, orthorhombisch, P2₁2₁2₁-D ₂ ⁴ ;a=13.006 (1),b=17.258 (2),c=9.125 (1) Å;Z=8. Die Strukturparameter der isotypen Verbindung 4-(2-hydroxythiobenzoyl)morpholin wurden als Startsatz für die Strukturverfeinerung benutzt. Es wurdeR=0.054 aus 1 900 Einkristallröntgendaten erreicht. Es befinden sich zwei Moleküle in der asymmetrischen Einheit.In beiden Verbindungen konnten mittels Differenz-Fourier-Summierungen die Wasserstoffatome lokalisiert werden. Die intermolekularen Wasserstoffbrükken mit O ... O-Distanzen von 2.649 (2) Å für das Piperidinderivat und 2.688 (3) bzw. 2.754 (3) Å für das Morpholinderivat sind typisch für mittlere Bindungsstärken.

     

Crystal structure of tris(2-pyridylthio-2-pyridinium)pentaisothiocyanato-dioxouranate(VI)

Summary The crystal structure of [DPSH] ₃ ⁺ [UO₂[NCS)₅]^3– (DPSH = 2 pyridylthio-2-pyridinium) has been determined by standard methods using diffractometer data. Crystals are monoclinic, space groupP2₁/a, witha=33.16 (3),b=16.68(2),c=7.85(1) Å, and=97.3(1); D_c=1.65 g · cm^–3 for Z=4. The structure has been refined to R=5.8% by least squares methods. Five thiocyanate groups are equatorially bonded to the linear uranyl group. The mean of the five U-N, N-C, and C-S bond distances are 2.45, 1.17, and 1.59 Å respectively. The protonated DPS molecules have the N,N-inside conformations.     

One-dimensional magnetism and crystal structure ofcatena-di-bromobis(3,5-dimethylpyridine)copper(II)

Summary Crystals ofcatena-di--bromobis(3,5-dimethylpyridine)copper(II) are monoclinic, space group P2₁/a. The unit cell constants area=13.900(2),b=14.416(2),c=4.097(1) Å,=93.49(2)°, V=819.4 ų and Z=2. The structure was determined from powder data using a Guinier-Johansson focussing powder camera. The structure was solved using a simplex method for function minimization to a conventional R-value of 0.13.The structure consists of infinite linear chains parallel toc in which the copper coordination is distorted elongated octahedral. Cu-Br distances were found to be 2.449(7) and 3.286(7) Å, whereas the Cu-N bond length is 2.02(2) Å. All distances are in the range usually observed for this type of compounds.The antiferromagnetic superexchange interactions between adjacent Cu^II ions (J = –21 cm^–1) has been compared with those observed in structural similar CuBr₂L₂ compounds. The differences in observed J-values are discussed briefly, in relation to the structural variations. It appears that very small changes in structural parameters strongly affect the magnetic exchange.     

Metallocyclic carbene complexes of chromium(0). The crystal and molecular structure of a chronium(0) complex with an aminoarylcarbene chelating ligand

Summary o-Lithiated reagents,o-LiC₆H₄XMe (X=O, S, or NMe), react with [Cr(CO)₆] to yield, after alkylation with [Et₃O][BF₄], the pentacarbonyl carbene complexes [Cr{C(OEt)C₆H₄XR}(CO)₅] and tetracarbonyl metallocyclic carbene complexes. An analogous five-membered chelate is obtainable from the lithiated vinylsulphide PhSCHCH₂. The x-ray structure of was determined by single crystal x-ray diffraction. It crystallizes in the monoclinic space groupP2₁/n witha=7.054(3),b=11.746(1),c=19.443(3) Å, = 95.35(2)^c and Z = 4. The final R-factors were R = 0.099 and R_w=0.044. Bond distances of 1.990(7) Å for Cr–C(carbene) and 2.240(6) Å for Cr–N were found.