A New Glimpse into the CO2‐Philicity of Carbonyl Compounds

We report a theoretical study on non‐conventional structures of 1:1 complexes between carbon dioxide and carbonyl compounds. These structures have never been reported before but are relevant for understanding the solubility of carbonyl compounds in supercritical CO₂. The work is based on the results of ab initio calculations at the MP2 and CCSD(T) levels using aug‐cc‐pVDZ and aug‐cc‐pVTZ basis sets. Investigated systems include aldehydes, ketones and esters, together with some fluorinated derivatives. The results are interpreted in terms of natural bond orbital analyses. Harmonic vibrational frequency calculations have also been done in order to compare them with available experimental data. We show for the first time that complexes where CO₂ behaves globally as a Lewis base are stable in the case of ketones and esters, but not in the case of aldehydes, and their stability is similar to that of traditional complexes in which CO₂ behaves as a Lewis acid. This finding considerably modifies the concept of CO₂‐philicity and may have important ramifications in the development of green reactions in supercritical CO₂.     

Expanding the Scope of Enantioselective FerroPHANE‐Promoted [3+2] Annulations with α,β‐Unsaturated Ketones

The planar chiral 2‐phospha[3]ferrocenophane I has been shown to be the first efficient nucleophilic organocatalyst for the enantioselective synthesis of cyclopentenylphosphonates, through [3+2] cyclizations between diethyl allenylphosphonate and α,β‐unsaturated ketones. The same catalyst has also been applied to the highly enantioselective [3+2] cyclizations of allenic esters with dibenzylideneacetone and analogous bis‐enones, leading to functionalised cyclopentenes with either monocyclic or spirocyclic structures (ee 84–95 %). It has been shown that the residual enone functions in the resulting cyclopentenes can be involved in subsequent cyclization steps to afford unprecedented C₂‐symmetric bis‐cyclopentenylketones. In order to provide insight into the behaviour of FerroPHANE I as a chiral catalyst in [3+2] cyclisations, the energetically most favoured isomers of the key phosphine‐allene adduct have been calculated by DFT methods. Factors likely to control the chiral induction process are highlighted.     

Rhodium‐Catalyzed 1,4‐Addition of Lithium 2‐Furyltriolborates to Unsaturated Ketones and Esters for Enantioselective Synthesis of γ‐Oxo‐Carboxylic Acids By Oxidation of the Furyl Ring with Ozone

Rhodium‐catalyzed 1,4‐addition of lithium 5‐methyl‐2‐furyltriolborate ([ArB(OCH₂)₃CCH₃]Li, Ar=5‐methyl‐2‐furyl) to unsaturated ketones to give β‐furyl ketones was followed by ozonolysis of the furyl ring for enantioselective synthesis of γ‐oxo‐carboxylic acids. [Rh(nbd)₂]BF₄ (nbd=2,5‐norbornadiene) chelated with 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (binap) or 2,3‐bis(diphenylphosphino)butane (chiraphos) gave high yields and high selectivities in a range of 91–99 % ee at 30 °C in a basic dioxane/water solution. The corresponding reaction of unsaturated esters, such as methyl crotonate, had strong resistance under analogous conditions, but the 1,4‐adduct was obtained in 70 % yield and with 94 % ee when more electron‐deficient phenyl crotonate was used as the substrate.     

Platin(0)‐Komplexe mit amino‐substituierten Alkinen: Neue Metallorganische Bausteine für supramolekulare Architekturen und „Kristall‐Engineering”︁

Platinum(0) Complexes with Amino‐Substituted Alkynes: Novel Organometallic Building Blocks for Supramolecular Architectures and “Crystal Engineering” Homoleptic Bis(alkyne)platinum(0) compounds containing either NH₂‐ or NH₂‐/OH‐substituents are formed by reaction of Pt(cod)₂ with alkynes as stable compounds. They can be used as variable building blocks for supramolecular networks. The crystal structure analyses of Bis(2‐amino‐2,5dimethyl‐5‐hydroxy‐hex‐3‐yne)platinum(0) ( 1 ) and of Bis(1(3‐amino‐3‐methyl‐but‐1‐inyl)‐cyclohexane‐1‐ol)platinum(0) ( 2 ) exhibit that the low‐valent Pt atom is tetrahedrally surrounded by the four sp‐hybridizated carbonatoms of the alkynes. Despite the fact that the bond lengths and ‐angles of the PtC₄ units are equal, the supramolecular structures are different. While in 1 polymer strands are formed in which the bis(alkyne)‐Pt⁰ units are connected by (OH)₂(NH₂)₂‐ tetrahedrons, 2 yields only a dimer containing a network of four OH‐ and two NH₂‐groups. Platinum(0) complexes with cationic alkynes bearing ammonium substituents can be isolated as thermal stable compounds. The X‐ray structures of [Cl( FH ⁺)Pt(cod)]₄ ( 8 ) reveals that four molecular units form a cube with both four NH₃⁺ groups and Cl^– at the corners connected by hydrogen bridges. In the bis(alkyne)Pt⁰ complex [Cl_1.5( FH ⁺)_1.5( F )_0.5Pt] ( 9 ) only 1,33 of two NH₂ groups are protonated and a hydrogen bridged network connects four bis(alkyne)Pt⁰ units (cod: cycloocta‐1.5‐diene, F : 1‐(trimethylsilylethinyl)‐1‐amino‐cyclohexane).     

μ3‐η2:η2:η2‐Coordination of Primary Silane on a Triruthenium Plane

A μ₃‐η²:η²:η²‐silane complex, [(Cp*Ru)₃(μ₃‐η²:η²:η²‐H₃SitBu)(μ‐H)₃] ( 2 a ; Cp*=η⁵‐C₅Me₅), was synthesized from the reaction of [{Cp*Ru(μ‐H)}₃(μ₃‐H)₂] ( 1 ) with tBuSiH₃. Complex 2 a is the first example of a silane ligand adopting a μ₃‐η²:η²:η² coordination mode. This unprecedented coordination mode was established by NMR and IR spectroscopy as well as X‐ray diffraction analysis and supported by a density functional study. Variable‐temperature NMR analysis implied that 2 a equilibrates with a tautomeric μ₃‐silyl complex ( 3 a ). Although 3 a was not isolated, the corresponding μ₃‐silyl complex, [(Cp*Ru)₃(μ₃‐η²:η²‐H₂SiPh)(H)(μ‐H)₃] ( 3 b ), was obtained from the reaction of 1 with PhSiH₃. Treatment of 2 a with PhSiH₃ resulted in a silane exchange reaction, leading to the formation of 3 b accompanied by the elimination of tBuSiH₃. This result indicates that the μ₃‐silane complex can be regarded as an “arrested” intermediate for the oxidative addition/reductive elimination of a primary silane to a trinuclear site.     

From α‐carbamoyl‐α‐cyano­oxiranes to 3‐halogenopyruv­amides

The crystal structures of the first stable α‐diol from the α‐halogenopyruv­amide series, 3‐chloro‐2,2‐di­hydroxy‐3‐phenyl­propan­amide, C₉H₁₀­ClNO₃, and three products [3‐(4‐chloro­phenyl)‐2‐cyano‐2,3‐epoxy­propan­amide, C₁₀H₇­ClN₂O₂, 3‐bromo‐2‐cyano‐2‐hydroxy‐3‐p‐tolyl­propan­amide, C₁₁H₁₁Br­N₂O₂, 3‐bromo‐2‐oxo‐3‐p‐tolyl­propan­amide, C₁₀H₁₀­BrNO₂] obtained during the systematic synthesis of α‐halogenopyruv­amides are reported. The crystal structures are dominated by hydrogen bonds involving an amide group. The stability of the geminal diol could be ascribed to hydrogen bonds which involve both hydroxyl groups.     

Yb3F4S2: Ein gemischtvalentes Ytterbiumfluoridsulfid gemäß YbF2 · 2 YbFS

Yb₃F₄S₂: A mixed‐valent Ytterbium Fluoride Sulfide according to YbF₂ · 2 YbFS Attempts to synthesize ytterbium(III) fluoride sulfide (YbFS) from 2 : 3 : 1‐molar mixtures of ytterbium metal (Yb), elemental sulfur (S) and ytterbium trifluoride (YbF₃) after seven days at 850 °C in silica‐jacketed gastight‐sealed arc‐welded tantalum capsules result in the formation of the mixed‐valent ytterbium(II,III) fluoride sulfide Yb₃F₄S₂ (tetragonal, I4/mmm; a = 384,61(3), c = 1884,2(4) pm; Z = 2) instead. The almost single‐phase product becomes even single‐crystalline and emerges as black shiny platelets with square cross‐section when equimolar amounts of NaCl are present as fluxing agent. Its crystal structure can be described as a sheethed intergrowth arrangement of one layer of CaF₂‐type YbF₂ followed by two layers of PbFCl‐type YbFS parallel (001). Accordingly there are two chemically and crystallographically different ytterbium cations present. One of them (Yb²⁺) is surrounded by eight fluoride anions in a cubic fashion, the other one (Yb³⁺) exhibits a capped square‐antiprismatic coordination sphere consisting of four F^– and five S^2– anions. In spite of being structurally very plausible, the obvious ordering of the differently charged ytterbium in terms of a localized mixed valency can only be fictive because of the black colour of Yb₃F₄S₂ which rather suggests charge delocalization coupled with polaron activity.     

Highly Efficient Hydrophosphonylation of Aldehydes and Unactivated Ketones Catalyzed by Methylene‐Linked Pyrrolyl Rare Earth Metal Amido Complexes

A series of rare earth metal amido complexes bearing methylene‐linked pyrrolyl‐amido ligands were prepared through silylamine elimination reactions and displayed high catalytic activities in hydrophosphonylations of aldehydes and unactivated ketones under solvent‐free conditions for liquid substrates. Treatment of [(Me₃Si)₂N]₃Ln(μ‐Cl)Li(THF)₃ with 2‐(2,6‐Me₂C₆H₃NHCH₂)C₄H₃NH ( 1 , 1 equiv) in toluene afforded the corresponding trivalent rare earth metal amides of formula {(μ‐η⁵:η¹):η¹‐2‐[(2,6‐Me₂C₆H₃)NCH₂](C₄H₃N)LnN(SiMe₃)₂}₂ [Ln=Y ( 2 ), Nd ( 3 ), Sm ( 4 ), Dy ( 5 ), Yb ( 6 )] in moderate to good yields. All compounds were fully characterized by spectroscopic methods and elemental analyses. The yttrium complex was also characterized by ¹H NMR spectroscopic analyses. The structures of complexes 2 , 3 , 4 , and 6 were determined by single‐crystal X‐ray analyses. Study of the catalytic activities of the complexes showed that these rare earth metal amido complexes were excellent catalysts for hydrophosphonylations of aldehydes and unactivated ketones. The catalyzed reactions between diethyl phosphite and aldehydes in the presence of the rare earth metal amido complexes (0.1 mol %) afforded the products in high yields (up to 99 %) at room temperature in short times of 5 to 10 min. Furthermore, the catalytic addition of diethyl phosphite to unactivated ketones also afforded the products in high yields of up to 99 % with employment of low loadings (0.1 to 0.5 mol %) of the rare earth metal amido complexes at room temperature in short times of 20 min. The system works well for a wide range of unactivated aliphatic, aromatic or heteroaromatic ketones, especially for substituted benzophenones, giving the corresponding α‐hydroxy diaryl phosphonates in moderate to high yields.     

A New Approach to the Design of Neutral 10‐C‐5 Trigonal‐Bipyramidal Carbon Compounds: A “π‐Electron Cap” Effect

DFT (B3LYP, M06‐2X) and MP2 methods are applied to the design of a wide series of the potentially 10‐C‐5 neutral compounds based on 6‐azabicyclotetradecanes: XC¹(YCH₂CH₂CH₂)₃N 1 – 3 , XC¹(YC₆H₄CH₂)₃N 4 – 6 , XC¹[Y(tBuC₆H₃)CH₂]₃N 7 – 9 and carbatranophanes 10 – 25 (X=Me, F, Cl; Y=O, NH, CH₂, SiH₂; Z=O, CH₂, (CH₂)₂, (CH₂)₃). Carbatranophanes 10 – 25 are characterized by a sterical compression of their axial 3c–4e XC¹←N fragment with respect to that in the parent molecules 4 – 6 . A magnitude of the revealed effect depends on a valence surrounding of the central carbon atom C¹, the size and the nature of the side chains (Z) that link the “π‐electron cap” with a tetradecane backbone. This circumstance allowed us to obtain 10‐C‐5 structures with the configuration of the bonds around the C¹ atom, which corresponds to practically an ideal trigonal bipyramid. In these compounds, the values of the covalence ratio χ of approximately 0.6 for the coordination C¹←N contacts with a covalent contribution (atoms in molecules (AIM) and natural bond orbital (NBO)) are record in magnitude. These values lie close to a low limit of the interval of the χ_Si←D change (0.6–0.9) being characteristic of the dative and ionic‐covalent (by nature) Si←D bond (D=N, O) in the known 10‐Si‐5 silicon compounds.     

Tantalum‐Niobium Mixing in Ta3–xNbxTeI7 (0 ≤ x ≤ 3)

A substitutional study of the layered, trinuclear metal cluster system, Ta_3–xNb_xTeI₇ (0 ≤ x ≤ 3), has been performed. Synthetic, crystallographic, and spectroscopic results are presented for starting compositions corresponding to the x values: 1, 1.5, and 2. For the entire composition range studied, Ta(Nb) could readily substitute into the Nb(Ta)₃TeI₇ structure, but with changes in the observed stacking arrangements of the layers as x varies. For tantalum‐rich (x ≤ 1.8) phases, the structure conformed to the Nb₃SeI₇ structure type, also adopted by Ta₃TeI₇ and one polytype of Nb₃TeI₇. Niobium‐rich (i. e. x ≥ 1.7) phases were observed to adopt two structure types according to X‐ray powder diffraction, but crystals could only be obtained for the Nb₃SBr₇ structure type, which is a second modification of Nb₃TeI₇. Extended Hückel calculations are used to discuss the distribution of metal clusters in this system.     

Synthesis of Halogenated α,β‐Unsaturated γ‐Butyrolactone Derivatives by Triphenylphosphine‐Catalyzed Cyclization of α‐Halogeno Ketones with Dialkyl Acetylenedicarboxylates (=Dialkyl But‐2‐ynedioates)

A Ph₃P‐catalyzed cyclization of α‐halogeno ketones 2 with dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates) 3 produced halogenated α,β‐unsaturated γ‐butyrolactone derivatives 4 in good yields (Scheme 1, Table). The presence of electron‐withdrawing groups such as halogen atoms at the α‐position of the ketones was necessary in this reaction. Cyclization of α‐chloro ketones resulted in higher yields than that of the corresponding α‐bromo ketones. Dihalogeno ketones similarly afforded the expected γ‐butyrolactone derivatives in high yields.     

Preparation and Characterization of Antimony and Arsenic Tricyanide and Their 2,2′‐Bipyridine Adducts

The arsenic(III) and antimony(III) cyanides M(CN)₃ (M=As, Sb) have been prepared in quantitative yields from the corresponding trifluorides through fluoride–cyanide exchange with Me₃SiCN in acetonitrile. When the reaction was carried out in the presence of one equivalent of 2,2′‐bipyridine, the adducts [M(CN)₃ ? (2,2′‐bipy)] were obtained. The crystal structures of As(CN)₃, [As(CN)₃ ? (2,2′‐bipy)] and [Sb(CN)₃ ? (2,2′‐bipy)] were determined and are surprisingly different. As(CN)₃ possesses a polymeric three‐dimensional structure, [As(CN)₃ ? (2,2′‐bipy)] exhibits a two‐dimensional sheet structure, and [Sb(CN)₃ ? (2,2′‐bipy)] has a chain structure, and none of the structures resembles those found for the corresponding arsenic and antimony triazides.     

Oxaphospholes and Bisphospholes from Phosphinophosphonates and α,β‐Unsaturated Ketones

The reaction of a {W(CO)₅}‐stabilized phosphinophosphonate 1 , (CO)₅WPH(Ph)? P(O)(OEt)₂, with ethynyl‐ ( 2 a – f ) and diethynylketones ( 7 – 11 , 18 , and 19 ) in the presence of lithium diisopropylamide (LDA) is examined. Lithiated 1 undergoes nucleophilic attack in the Michael position of the acetylenic ketones, as long as this position is not sterically encumbered by bulky (iPr)₃Si substituents. Reaction of all other monoacetylenic ketones with lithiated 1 results in the formation of 2,5‐dihydro‐1,2‐oxaphospholes 3 and 4 . When diacetylenic ketones are employed in the reaction, two very different product types can be isolated. If at least one (Me)₃Si or (Et)₃Si acetylene terminus is present, as in 7 , 8 , and 19 , an anionic oxaphosphole intermediate can react further with a second equivalent of ketone to give cumulene‐decorated oxaphospholes 14 , 15 , 24 , and 25 . Diacetylenic ketones 10 and 11 , with two aromatic acetylene substituents, react with lithitated 1 to form exclusively ethenyl‐bridged bisphospholes 16 and 17 . Mechanisms that rationalize the formation of all heterocycles are presented and are supported by DFT calculations. Computational studies suggest that thermodynamic, as well as kinetic, considerations dictate the observed reactivity. The calculated reaction pathways reveal a number of almost isoenergetic intermediates that follow after ring opening of the initially formed oxadiphosphetane. Bisphosphole formation through a carbene intermediate G is greatly favored in the presence of phenyl substituents, whereas the formation of cumulene‐decorated oxaphospholes is more exothermic for the trimethylsilyl‐containing substrates. The pathway to the latter compounds contains a 1,3‐shift of the group that stems from the acetylene terminus of the ketone substrates. For silyl substituents, the 1,3‐shift proceeds along a smooth potential energy surface through a transition state that is characterized by a pentacoordinated silicon center. In contrast, a high‐lying transition state TS(E′–F′)_R=Ph of 37 kcal mol^?1 is found when the substituent is a phenyl group, thus explaining the experimental observation that aryl‐terminated diethynylketones 10 and 11 exclusively form bisphospholes 16 and 17 .     

Synthesis and Characterization of the First Bisand Tris[1‐(ω‐alken‐1‐yl)indenyl]lanthanide Complexes

1‐Allyl‐2,4,7‐trimethyl‐1 H‐indene ( 1 ) and 1‐(3‐buten‐1‐yl)‐4,7‐dimethyl‐1 H‐indene ( 2 ), which are to prepare from (2,4,7‐trimethylindenyl)lithium and allyl chloride or from (4,7‐dimethylindenyl)lithium and 4‐bromo‐1‐butene, react with n‐butyllithium yielding (1‐allyl‐2,4,7‐trimethylindenyl)lithium [LiL ( 1 a )] or [1‐(3‐buten‐1‐yl)‐4,7‐dimethylindenyl]lithium [LiL′ ( 2 a )], respectively. The reactions of the trichlorides of gadolinium, erbium, yttrium, lutetium, and ytterbium with 1 a or 2 a (mole ratio 1 : 2) in THF produce the bis(indenyl)lanthanide chloride complexes L₂LnCl(THF) [Ln = Gd ( 1 b ), Er ( 1 c )], LLnCl(THF) [Y ( 2 d ), Lu ( 2 e )], or LYb(μ‐Cl)₂Li(THF)₂ ( 2 f ), whereas the trichlorides of the comparatively large samarium and lanthanum ions react with different molar amounts of 2 a in THF exclusively with formation of the tris(indenyl) complexes LSm ( 2 g ) or LLa(μ‐Cl)Li(Et₂O)₃ ( 2 h ), respectively. All new compounds were characterized by elemental analyses, mass spectrometry, and the diamagnetic compounds 2 d , 2 e and 2 h also by ¹H and ¹³C{¹H}‐NMR spectroscopy. The single crystal X‐ray structural analyses of 1 c , 2 f , 2 g and 2 h demonstrate that the alkenyl groups of the indenyl side chains are not coordinated to the lanthanide atoms.     

SBA‐15‐supported N‐coordinate ruthenium(II) materials bearing sulfonamide‐type ligands: Effect of ligand backbones on catalytic transfer hydrogenation of ketones and aldehydes

[RuLCl(p ‐cymene)] (L = N ‐arylsulfonylphenylenediamine) complexes ( 2 _{a – d} ) were synthesized from the reaction between [Ru(p ‐cymene)Cl₂]₂ and ligand. Additionally, SBA‐15–[RuLCl(p ‐cymene)] derived catalysts ( 3 _{a – d} ) were successfully immobilized onto mesoporous silica (SBA‐15) by an easily accessible approach. The structural elucidations of 2 _{a – d} and 3 _{a – d} were carried out with various methods such as ¹H NMR, ¹³C NMR and infrared spectroscopies, elemental analysis, thermogravimetric/differential thermal analysis, nitrogen adsorption–desorption and scanning electron microscopy/energy‐dispersive X‐ray analysis. The Ru(II) complexes and materials were found to be highly active and selective catalysts for the transfer hydrogenation (TH) reaction of aldehydes and ketones. The influence of various 1,2‐phenylenediamines on the reactivity of the catalysts (complexes or materials) was studied and the catalysts ( 2 _d and 3 _d ) with a 4,5‐dichlorophenylenediamine substituent showed the best activity (the maximum turnover frequencies are 2916 and 2154 h⁻¹ for TH of 4‐fluoroacetophenone, and 6000 and 4956 h⁻¹ for TH of 4‐chlorobenzaldehyde).     

Rapid and Slow Generation of 1‐Trifluoromethylvinyllithium: Syntheses and Applications of CF3‐Containing Allylic Alcohols,Allylic Amines,and Vinyl Ketones

1‐(Trifluoromethyl)vinylation is accomplished in two protocols by the in situ generation of thermally unstable 3,3,3‐trifluoroprop‐1‐en‐2‐yllithium ( 1 ): 1) a rapid lithium–halogen‐exchange reaction of 2‐bromo‐3,3,3‐trifluoroprop‐1‐ene ( 2 ) takes effect with sec‐BuLi at ?105 °C to generate vinyllithium 1 , which reacts with more reactive electrophiles, such as aldehydes and N‐tosylimines before its decomposition, to afford 2‐(trifluoromethyl)allyl alcohols and N‐[2‐(trifluoromethyl)allyl] sulfoamides in good yield; 2) treatment of 2 with nBuLi at ?100 °C causes a slow lithium–halogen exchange of 2 , which gives rise to a mixture of 1 and nBuLi. Vinyllithium 1 is preferentially trapped with less reactive electrophiles, such as N,N‐dimethylamides in the presence of BF₃?OEt₂, to afford 1‐(trifluoromethyl)vinyl ketones in good yield. Versatility of the products toward syntheses of CF₃‐containing ring‐fused cyclopentenones is also demonstrated by the Pauson–Khand reaction and the Nazarov cyclization.     

Darstellung,Eigenschaften und Kristallstruktur von RuSn6[(Al1/3–xSi3x/4)O4]2 (0 ≤ x ≤ 1/3) – einem Oxid mit isolierten RuSn6‐Oktaedern

Preparation, Properties, and Crystal Structure of RuSn₆[(Al_1/3–xSi_3x/4)O₄]₂ (0 ≤ x ≤ 1/3) – an Oxide with isolated RuSn₆ Octahedra RuSn₆[(Al_1/3–xSi_3x/4)O₄]₂ is obtained by the solid state reaction of RuO₂, SnO₂, Sn, and Si in an Al₂O₃‐crucible at 1273 to 1373 K. The compound is cubic with the space group Fm 3 m (a = 9.941(1) Å, Z = 4, R₁ = 0.0277, wR₂ = 0.0619), a semiconductor and stable in air. Results of Mößbauer measurements as well as bond length‐bond strength calculations justify the ionic formulation Ru²⁺Sn₆²⁺[(Al_1/3–x³⁺Si_3x/4⁴⁺)O₄^2–]₂. The central motif of the crystal structure are separated RuSn₆‐octahedrea. These are interconnected by oxygen atoms, arranged tetrahedrely above the surfaces of the RuSn₆‐octahedrea and partialy filled with Al and Si, respectively. Because of these features the compound can be considered as a variant of the crystal structure type of pentlandite.     

Phosphorus‐Stabilized Titanium Carbene Complexes: Synthesis,Reactivity and DFT Studies

The synthesis of two novel titanium carbene complexes from the bis(thiophosphinoyl)methanediide geminal dianion 1 (SCS^2?) is described. Dianion 1 reacts cleanly with 0.5 equivalents of [TiCl₄(thf)₂] to afford the bis‐carbene complex [(SCS)₂Ti] ( 2 ) in 86 % yield. The mono‐carbene complex [(SCS)TiCl₂(thf)] ( 3 ) can also be obtained by using an excess of [TiCl₄(thf)₂]. The structures of 2 and 3 are confirmed by X‐ray crystallography. A strong nucleophilic reactivity towards various electrophiles (ketones and aldehydes) is observed. The reaction of 3 with N,N′‐dicyclohexylcarbodiimide (DCC) and phenyl isocyanate leads to the formation of two novel diphosphinoketenimines 8 a and 8 b . The bis‐titanium guanidinate complex 9 is trapped as the by‐product of the reaction with DCC. The X‐ray crystal structures of 8 a and 9 are presented. The mechanism of the reaction between complex 3 and DCC is rationalized by DFT studies.     

Heterokuban‐Cluster‐Verbindungen (NEt4){Y=M[(μ3‐S)Re(CO)3]3(μ3‐E)} (M = W oder Mo,Y = O oder S,E = S oder Se): Strukturen,Spektroskopie und Elektrochemie

Heterocubane Cluster Compounds (NEt₄){Y=M[(μ₃‐S)Re(CO)₃]₃(μ₃‐E)} (M = W or Mo, Y = O or S, E = S or Se): Structures, Spectroscopy, and Electrochemistry Thiometallates [MS₄]^2– (M = Mo, W) or [WOS₃]^2– react with Re(CO)₅(O₃SCF₃) and Li₂E (E = S or Se) to yield the following compounds which were structurally characterized: (NEt₄){S=W[(μ₃‐S)Re(CO)₃]₃(μ₃‐S)}(NEt₄) ( 1 ), (NEt₄){O/S=W[(μ₃‐S)Re(CO)₃](μ₃‐S)}(NEt₄) ( 1 / 2 ), (mixed crystals), (NEt₄){S=W[(μ₃‐S)Re(CO)₃]₃(μ₃‐Se)}(NEt₄) ( 3 ) and (NEt₄){S=Mo[(μ₃‐S)Re(CO)₃]₃(μ₃‐S)}(NEt₄) ( 4 ). The heterocubane anions 1 – 4 contain electron‐rich centers such as rhenium(I) or sulfide whereas molybdenum(VI) or tungsten(VI) act as acceptor sites. Accordingly, the absorption spectra show long‐wavelength metal‐to‐ligand charge transfer transitions, and cyclic voltammetry reveals a quasi‐reversible reduction of the clusters. Although both six‐coordinate rhenium(I) and four‐coordinate metal(VI) centers are present in the clusters there is no evidence for significant metal‐to‐metal charge transfer interaction.     

Small carbon‐carbon couplings in monosubstituted benzenes – their signs and magnitudes determined by HCSE method

Signed values of all intra‐ring ^2,3,4J(C,C) couplings in nine monosubstituted benzenes (C₆H₅‐X where X = F, Cl, Br, CH₃, OCH₃, Si(CH₃)₃, C ≡ N, NO, NO₂) are experimentally determined as well as nine couplings to substituent carbons. It is confirmed that while all the vicinal intra‐ring ³J(C,C) are positive and all geminal ²J(C2,C4) are negative, both signs are found for geminal ²J(C1,C3) couplings. All the determined signs agree with those already predicted by theoretical calculations. Copyright © 2013 John Wiley & Sons, Ltd.