Sodium Salts of the Bipyridine Dianion: Polymer [(bpy)2−{Na+(dme)}2]∞, Cluster [(Na8O)6+Na+6(bpy)62−(tmeda)6], and Monomer [(bpy)2−{Na+(pmdta)}2]

Bipyridine, a workhorse among the ligands of complex chemistry, can be reduced with sodium to its dianion. Depending on the solvent different sodium salts crystallize: from dimethoxyethane/toluene a polymer, from tetramethylethylenediamine/benzene a lipophilically wrapped [Na₁₄O]¹²⁺ cluster, and from pure pentamethyldiethylenetriamine a normal Na₂-bpy salt (see picture) are obtained.     

Ethyl 2‐methoxy‐6‐[(triphenylphosphoranylidene)amino]nicotinate and ethyl 2‐methylsulfanyl‐6‐[(triphenylphosphoranylidene)amino]nicotinate

The molecules of ethyl 2‐methoxy‐6‐[(triphenylphosphoranylidene)amino]nicotinate, C₂₇H₂₅N₂O₃P, (I), and ethyl 2‐methylsulfanyl‐6‐[(triphenylphosphoranylidene)amino]nicotinate, C₂₇H₂₅N₂O₂PS, (II), have almost identical bond lengths and molecular conformations, and both show evidence for polarized electronic structures. However, the crystal structures, as illustrated by the weak hydrogen bonds linking the molecules, are significantly different. The significance of this study lies in the observation that two compounds which are almost identical in constitution, configuration and conformation nonetheless adopt different crystal structures.     

Isolation of Reduced Zirconium Chloride Clusters [(Zr6CCl12)Cl6]4− and [(Zr6BCl12)Cl6]5− from Acidic Aqueous Solution

Crystallizable from concentrated hydrochloric acid : Compounds containing [(Zr₆BCl₁₂)Cl₆]⁵⁻ and [(Zr₆CCl₁₂)Cl₆]⁴⁻ clusters survive dissolution in deoxygenated water, and this enabled the study of reduced zirconium compounds in aqueous solution for the first time. In the solid state, the clusters are surrounded by novel hydrogen-bonded water networks that interact with the terminal chloride ligands (see graphic; black circles: Zr, smaller circle: B, gray circles: Cl, open circles: O of H₂O).     

Darstellung, 19F-NMR-spektroskopischer Nachweis und Untersuchung zur Bildung der metallgemischten Clusteranionen [(Mo6−nWnCl)F]2−, n = 0−6

Preparation, ¹⁹F NMR Spectroscopic Evidence and Study of the Formation of Metal-Mixed Cluster Anions [(Mo_6?nW_nCl )F ]^2?, n = 0?6 The complete system of metal-mixed octahedral cluster ions [(Mo_6?nW_nCl)F]^2?, n = 0?6, is prepared by tempering Mo powder with WCl₆ at 600°C. A mixture containing inclusively the geometric isomers (n = 2, 3, 4) all ten possible species is transferred into the tetra-n-butylammonium salts (TBA)₂[(Mo_6?nW_nCl)F]. In the ¹⁹F nmr spectrum the 24 expected signals are observed, assigned on the basis of their chemical shifts, multiplicities and intensities, and confirmed by a 2D-¹⁹F-¹⁹F COSY spectrum. From the integrated intensities the distribution of the different components is derived revealing a non-statistical formation, in that isomers with Mo…?Mo or W…?W atoms in trans-positions in comparision to those with mixed Mo…?W axes are favoured, and that especially the homoleptic compounds Mo₆ and W₆ are present to an over-average extent. Evaluation of ¹⁹F chemical shifts reveals that F bound to W which is in antipodal position to Mo resonates at higher field compared to F bound to W in a W…?W arrangement, caused by an increased shielding, which is synonymous to a positive antipodal-effect by Mo. Vice versa F bound to Mo with an antipodal W resonates at lower field compared with F bound to Mo in an Mo…?Mo arrangement caused by an increased deshielding and synonymous a negative antipodal-effect by W. The chemical shifts, resulting from antipodal-effects, are different for the compounds within the [(Mo_6?nW_nCl)F]^2? - system. The difference of the antipodal effect of successive substitution products results in characteristic values designated as antipodal shift constants, depending on the kind of substituents, which is valid for other cluster systems, too.     

3,4‐Lutidinium salts with the diiodidoaurate(I) anion: structure of [(3,4‐lut)2H]+·[AuI2]− and of two polymorphs of [(3,4‐lut)2H+]2·[AuI2]−·I−

Reactions between potassium tetraiodidoaurate(III) and pyridine (py, C₅H₅N) or 3,4‐lutidine (3,4‐dimethylpyridine, 3,4‐lut, C₇H₉N) were tested as possible sources of azaaromatic complexes of gold(III) iodide, but all identifiable products contained gold(I). The previously known structure dipyridinegold(I) diiodidoaurate(I), [Au(py)₂]⁺·[AuI₂]⁻, ( 3 ) [Adams et al. (1982). Z. Anorg. Allg. Chem. 485 , 81–91], was redetermined at 100 K. The reactions with 3,4‐lutidine gave three different types of crystal in small quantities. 3,4‐Dimethylpyridine–3,4‐dimethylpyridinium diiodidoaurate(I), [(3,4‐lut)₂H]⁺·[AuI₂]⁻, ( 1 ), consists of an [AuI₂]⁻ anion on a general position and two [(3,4‐lut)₂H]⁺ cations across twofold axes. Bis(3,4‐dimethylpyridine–3,4‐dimethylpyridinium) diiodidoaurate(I) iodide, [(3,4‐lut)₂H⁺]₂·[AuI₂]⁻·I⁻, ( 2 ), crystallizes as two polymorphs, each forming pseudosymmetric inversion twins, in the space groups P2₁ and Pc (but resembling P2₁/m and P2/c), respectively. These are essentially identical layer structures differing only in their stacking patterns and thus might be regarded as polytypes.     

Über die Darstellung der Dichlormethylen-halogensulfenium-Salze Cl2CSCl+ AsF6− und Cl2CSBr+ AsF6− [1]

The Synthesis of the Dichloromethylene-halogenosulfenium Salts Cl₂CSCl⁺ AsF₆^? and Cl₂CSBr⁺ AsF₆^? The sulfenium salts Cl₂CSCl⁺ AsF₆^? and Cl₂CSBr⁺ AsF₆^? are synthesized by oxidative halogenation of thiophosgene, Cl₂CS with X₂/AsF₅ (X = Cl, Br) at 195 K and are characterized by vibrational as well as NMR spectroscopy.     

Hypervalent Pentafluoroethylgermanium Compounds, [(C2F5)nGeX5−n]− and [(C2F5)3GeF3]2− (X=F,Cl; n=2–5)

This paper gives an account on hypervalent fluoro‐ and chloro(pentafluoroethyl)germanium compounds. The selective synthesis of the tris(pentafluoroethyl)dichlorogermanate salt [PNP][(C₂F₅)₃GeCl₂] as well as its X‐ray structural analysis is described. As a representative example for pentafluoroethylfluorogermanates, the synthesis and structure of 2,4,6‐triphenylpyryliumtris(pentafluoroethyl)difluorogermanate [C₂₃H₁₇O][(C₂F₅)₃GeF₂] is reported. Fluoride‐ion affinities for pentafluoroethylgermanes were calculated using quantum chemical methods, disclosing (C₂F₅)₃GeF as a weaker Lewis acid than (C₂F₅)₃SiF or (C₂F₅)₃PF₂. The theoretical results were confirmed by experiments and give the basis of a synthetic protocol for (C₂F₅)₃GeF. Pentakis(pentafluoroethyl)germanate [PPh₄][Ge(C₂F₅)₅] was detected as an intermediate during the synthesis of [PPh₄][(C₂F₅)₄GeF] starting from tris(pentafluoroethyl)difluorogermanate and LiC₂F₅.     

Extraction and isolation of the One-electron Oxidized [(Zr6Be)Cl18]5− and [(Zr6Be)Cl18]4− Clusters from solid state precursors

One-electron oxidized zirconium chloride clusters were obtained from solid state precursors Rb₅Zr₆Cl₁₈B and K₃Zr₆Cl₁₅Be by dissolution in CH₃CN in the presence of Et₄NCl and isolated as the salts (Et₄N)₄Zr₆Cl₁₈B · 2 CH₃CN and (Et₄N)₅Zr₆Cl₁₈Be · 3 CH₃CN. (Et₄N)₄Zr₆Cl₁₈B · 2 CH₃CN crystallizes in the space group P1 (#2) with a = 12.329(5) Å, b = 12.657(6) Å, c = 13.136(8) Å, α = 118.28(4)°, β = 93.45(4)°, γ = 105.54(3)°, V = 1696(2) ų, and Z = 1. (Et₄N)₅Zr₆Cl₁₈Be · 3 CH₃CN was refined in the space group C2/c (# 15) with a = 24.166(11) Å, b = 13.265(6) Å, c = 25.86(2) Å, β = 104.21(4)°, V = 8037(7) ų, and Z = 4; the space group reflects the pseudo-symmetry of the crystal, the true symmetry of the structure is lower. The removal of one electron from the Zr? Zr bonding HOMO of both clusters results in cluster expansion of similar magnitude in both compounds. Moisture from the added Et₄NCl is the likely oxidant, but the possibility that acetonitrile may be reduced by [(Zr₆Be)Cl₁₈]^6? is not ruled out.     

[(NHC)NiIIH]‐Catalyzed Cross‐Hydroalkenylation of Cyclopropenes with Alkynes: Cyclopentadiene Synthesis by [(NHC)NiII]‐Assisted C−C Rearrangement

A cross‐hydroalkenylation/rearrangement cascade (HARC), using a cyclopropene and alkyne as substrate pairs, was achieved for the first time by using new [(NHC)Ni(allyl)]BAr^F catalysts (NHC=N‐heterocyclic carbenes). By controlling the (NHC)Ni^IIH relative insertion reactivity with cyclopropene and alkyne, a broad scope of cyclopentadienes was obtained with highly selectively. The structural features of the new (NHC)Ni^II catalyst were important for the success of the reaction. The mild reaction conditions employed may serve as an entry for exploring (NHC)Ni^II‐assisted vinylcyclopropane rearrangement reactivity.