Mechtild Dartmann

Coordination fluxionality of copper(II) with a sterically constrained Pyrazole-containing chelating ligand. crystal and molecular structure at 298 K and 140 K of=1,6-Bis(3,5-dimethylpyrazol-1-yl)-2,5-dimethyl-2,5-diazahexane-bis(thiocyanato-N)copper(II), [C18H28CuN8S2]

The X-ray structure determinations of the compound Cu(debd)(NCS) 2 at 140 K and at 298 K showed at both temperatures a tetragonal crystal system with space group P 4 1 2 1 2 ( Z =4) and a molecular C 2 symmetry. Cell dimensions are: a = 9.577, c =24.422 A and V =2240 A 3 at 140 K, and a =9.614, c =24.854 A and V =2297 A 3 at 298 K. 1218 (140 K) and 1057 (298 K) reflections with I > 1.96 σ( I ) were used for the solution to a final R w value of 0.036 (140 K) and 0.032 (298 K). The copper(II) environment is roughly octahedral. The copper to nitrogen bonds vary with temperature: Cu-N(amine)=2.242 A (140 K) and 2.191 A (298 K), Cu-N(pyrazole)=2.099 A (140 K) and 2.193 A (298 K), and Cu-NCS=2.060 A (140 K) and 2.034 A (298 K). The ESR spectra of the Cu(II)- doped isomorphous Zn(II) and Cd(II) compounds, which have been measured at ambient temperature, at 77 K, and at 3 K, clearly reflect the temperature dependence of the structure.

Silaethene: XIII. Erzeugung von SiC-Doppelbindungen in der Koordinationssphäre von Eisencarbonylkomplexen

Abstract The suitability of the vinylsilyliron complexes [Cp(CO) 2 Fe]RSi(Cl)CHCH 2 [R = Me ( 1 ), Ph ( 2 ), Bu t ( 3 ), Fe(CO) 2 Cp ( 4 )] and of [Cp(CO) 2 Fe]MeSi(Cl)CMeCH 2 ( 14 ) as precursors for the generation of silaethene derivatives has been investigated. The starting compounds 1 to 4 and 14 can be obtained from Me(Vi)SiCl 2 , Ph(Vi)SiCl 2 , HSiCl 3 and MeSiCl 3 , respectively, by judicious combination of published procedures. They have been characterized by analytical and spectroscopic studies as well as by comparison with known data. The generation of the SiC intermediates was attempted by treating the vinylsilyl iron complexes wit LiBu t at low temperatures (−10°C). Only with 1 was a smooth reaction observed with formation of the Z Z dimer 1,3-bis(cyclopentadienyl-dicarbonyliron)-1,3-dimethyl-2,4-dineopentyl-1,3-disilacyclobutane ( 16 ) of the expected silaethene [Cp(CO) 2 Fe]-MeSiCHCH 2 Bu t . This intermediate also seems plausible on the basis of trapping experiments, using 2,3-dimethyl-1,3-butadiene, isoprene or 1,3-cyclohexadiene. However, since 16 is formed as the main product even in the presence of an excess of these dienes, the cyclization of the lithiated precursor ClSiMe[Fe(CO) 2 Cp]-CH(CH 2 Bu t )SiMe[Fe(CO) 2 Cp]CH(Li)CH 2 Bu t must be regarded as an alternative route to 16 . The crystal and molecular structure of 16 indicate a Z Z configuration of the bulky ring substituents. The disilacyclobutane skeleton is nonplanar with a dihedral angle of 18.7°. Similar to other 1,3-disilacyclobutane derivatives, 16 shows a fairly short transannular Si(1)⋯Si(2) distance of 2.641(1) A. Due to the −I effect of the phenyl substituent reaction of 2 with LiBu t yields oligomeric coupling products, whereas in 3 , 4 or 14 for steric reasons LiBu t clearly attacks the carbonyl ligand instead of the CC double bond to give black, pyrophoric solids of low solubility.

Copper(I) and copper(II) compounds of a dinucleating, octadentate tetrakisbenzimidazole ligand. Crystal and molecular structures of three dihalogeno{1,8-bis[bis(1′-methylbenzimidazol-2′-ylmethyl)amino]-3,6-dioxaoctane}dicopper(II) bis(anion) compounds (halogen = F, Cl, or Br; anion = BF4, CF3SO3, or Cl)

Synthesis, spectroscopic characterisation, and single-crystal structure analyses are described for a number of CuI and CuII co-ordination compounds with the ligand 1,8-bis[bis(1′-methyl-benzimidazol-2′-ylmethyl)amino]-3,6-dioxaoctane (L). The compounds have the general formulae Cu2(L)X2Y2·xS, Cu(L)Y, Cu2(L)(CO)2Y2, Cu2(L)(Z)Y3, and Cu2(L)X2, where X = F, Cl, Br, or I; Y = ClO4, BF4, CF3SO3, Cl, or Br; Z = bridging anion like benzotriazolate; and S = solvent. Single-crystal structures of three CuII compounds, [Cu2(L)F2][BF4]2·2H2O·H2OBF3(1), [Cu2(L)Cl2]Cl2·6H2O (2), and [Cu2(L)Br2][CF3SO3]2·EtOH (3) have been determined using diffractometer data. All three compounds contain the dinuclear unit [XCu(L)CuX]2+ in which the ligand L bridges the two Cu–X fragments. However, the intramolecular Cu ⋯ Cu distances are very large (i.e. larger than 575 pm). The intermolecular Cu ⋯ Cu contacts are much shorter, being 481, 388–488, and 398–405 pm, for (1), (2), and (3), respectively. Ligand-field, e.s.r., n.m.r., and i.r. spectra have been used to characterise all the compounds. The ligand-field maxima all agree with square-pyramidal CuII with a CuN3XO chromophore in which X = F, Cl, or Br, respectively. The e.s.r. spectra indicate that exchange effects (intermolecularly) are important, resulting even in exchange-narrowed signals. Only the compounds Cu2(L)(Z)Y3 exhibit e.s.r. spectra typical for dinuclear CuII systems. The observed νCO bands at ca. 2 100 cm–1 for the CuI–CO adducts agree with end-on CO co-ordination.

Reaktive EC (pp) π-Systeme: XVII. Diels—Alder-Addukte des Perfluor-2-phosphapropens als Liganden in Chrom- und Wolframpentacarbonylkomplexen

Abstract The reactions of the Diels—Alder adducts 2–9 of F3CPCF2 (1) [adduct with isoprene (2), with 2,3-dimethylbutadiene (3), with 2,3-diphenylbutadiene (4), with cyclopentadiene (5), with pentamethylcyclopentadiene (6), with furan (7), with 1,3-cyclohexadiene (8), with 9,10-dimethylanthracene (9)] with the photochemically produced complexes M(CO)5THF lead to the pentacarbonyl metal compounds 2a–9a (M = Cr) and 2b–9b (M = W), respectively, in moderate to good yields (40–72%). Spectroscopic investigations of the new complexes show that with respect to ligand properties, the cyclic phosphanes 2–9 correspond to the compounds (CH3)2PCF3 and H3CP(CF3)2, which indicates that steric effects are of minor importance for the MP bond. The determination of the crystal and molecular strucutre of 5a supports the arrangement of substituents on the PC bond of the cycloadduct 5 as deduced from NMR data. The main product of the [2+4]-cycloaddition of 1 to cyclopentadiene is the endo isomer. New compounds have been identified by elemental analysis (C, H) and by mass, NMR and IR spectroscopy.

Preparation and crystal structure of a sulphinylnitrilo complex of rhodium(I): trans-[Rh(CO)(NSO)(PPh3)2]

The reaction of CsNSO2 with [RhH(CO)(PPh3)3] in acetonitrile yields trans-[Rh(CO)(NSO)(PPh3)2](1) and PPh3O. Complex (1) has been characterised by elemental analyses, i.r. spectra, and a single-crystal X-ray structure investigation. Crystals of (1) are triclinic, space group P, with a= 9.248(2), b= 9.502(2), c= 10.567(2)A, α= 71.52(2), β= 89.71 (2), γ= 69.80(2)°, and Z= 1. In the square-planar molecular complex the carbonyl group [Rh–C 1.843(6)A] is in the trans position relative to the NSO ligand [Rh–N 1.989(9), N–S 1.48(1), S–O 1.51(1)A; N–S–O 122.5(5)°]. The Rh–P bond lengths to the trans-Co-ordinated phosphine ligands are 2.330(1)A. The arrangement of the molecules in the crystal is disordered, with a superposition of two half-occupied CO and NSO ligand sites in the electron-density map, simulating the crystallographic inversion centre at the Rh site.

Reaktionen und Strukturen von [(C2H5)4N][OsCl6] und [(n-C4H9)4N]2[Os2Cl10] / Reactions and Structures of [(C2H5)4N][OsCl6] and [(n-C4H9)4N]2[Os2Cl10]

On heating of [(C2H5)4N][OsCl6] for a short time at 240 °C , Cl2 is lost and [(C2H5)4N]2[Os2Cl10] is formed quantitatively. Both complexes are connected by a temperature dependent redox equilibrium so that by treatment at 120 °C with Cl2 gas the hexachloroosmate(V) is recovered from the decachlorodiosmate(IV). The crystal structures of salts of both an ions were determined from single crystal X -ray diffraction analyses. [(C2H5)4N][OsCl6] is monoclinic, space group P2 1 with a = 7 .020 (1), b = 10 .163 (2), c = 11.609 (2) Å , β = 103.91(1)° (at - 133 °C ). The strongly pseudocentrosymmetric structure shows a reversible phase transition at ca. 85 °C. The Os -Cl bond length (mean value 2.303 Å) in the regular [OsCl6]-octahedra is significantly smaller than in [OsCl6]2− , in accordance with vibrational spectra. [(n -C4H9)4N]2 [Os2Cl10] crystallizes in the orthorhombic space group Pbca with a = 15 .496 (2), b = 15 .965 (3), c = 19 .431(3) Å and contains centrosymmetric [Os2Cl10]2− ions with approximate D2h symmetry. Within the edge-sharing [OsCl6] octahedra the mean terminal and bridging Os -Cl bond lengths are 2.307 and 2.411 Å , respectively.

Amino(keto)carbene und Amino(phenyl)carbene als 1.4-dipolare Brückenliganden in einer Fe2(CO)6-Matrix / Amino(keto)carbenes and Amino(phenyl)carbenes as 1,4-Dipolar Bridging Ligands in a Fe2(CO)6 Matrix

Abstract Cyclohexylamino(keto)carbene complexes of group VI B metals which contain a terminally bound carbene ligand, on reaction with Fe2(C0)9 give binuclear oxallyl iron complexes 5, in which the carbene carbon and the keto function form a bridge consisting of three atoms bound to two iron atoms. From a single crystal structure analysis of the phenyl derivative 5b, the Fe-Fe distance was found to be 2.508 Å. The two C atoms are bridging the Fe2 group in a somewhat distorted manner (C(l)-Fe(l) 2.461, C(l)-Fe(2) 1.912, C(2)-Fe(l) 2.024, C(2)-Fe(2) 2.478 Å), whereas the bridging keto oxygen is symmetrically bound to both Fe (1.927 and 2.004 Å). Alkylamino(phenyl)carbene complexes like 11 react with Fe2(C0)9 to give a four atom bridging ligand by migration of a hydrogen atom from nitrogen and an ortho hydrogen from the phenyl group to the carbene carbon. Free or complexed alkylimines may be intermediates in this reaction.