Selective Formation and Unusual Reactivity of Tetraarsabicyclo[1.1.0]butane Complexes

The selective formation of the dinuclear butterfly complexes [{Cp′′′Fe(CO)₂}₂(μ,η^1:1‐E₄)] (E=P ( 1 a ), As ( 1 b )) and [{Cp*Cr(CO)₃}₂(μ,η^1:1‐E₄)] (E=P ( 2 a ), As ( 2 b )) as new representatives of this rare class of compounds was found by reaction of E₄ with the corresponding dimeric carbonyl complexes. Complexes 1 b and 2 b are the first As₄ butterfly compounds with a bridging coordination mode. Moreover, first studies regarding the reactivity of 1 b and 2 b are presented, revealing the formation of the unprecedented As₈ cuneane complexes [{Cp′′′Fe(CO)₂}₂{Cp′′′Fe(CO)}₂(μ₄,η^1:1:2:2‐As₈)] ( 3 b ) and [{Cp*Cr(CO)₃}₄(μ₄,η^1:1:1:1‐As₈)] ( 4 ). The compounds are fully characterized by NMR and IR spectroscopy as well as by X‐ray structure analysis. In addition, DFT calculations give insight into the transformation pathway from the E₄ butterfly to the corresponding cuneane structural motif.     

Mixed Ligand Complexes of Palladium (II) with Diethylenetriamine as Primary Ligand and Peptides as Secondary Ligand

Solution equilibria of the system palladium (II)-diethylenetriamine (dien) and peptides have been studied. The pH-metric titration of the reaction mixture containing equimolar solutions of palladium (II), dien and peptide have shown the formation of 1:1:1 mixed ligand complex. The pK_e of the peptides studied and formation constants of the resulting complexes have been determined at 25°C. The mode of chelation has been deduced from the conductivity measurements.     

The anhydride route to Group 15/16 ligands in oligomeric and polymeric environments: from metal complexes to supraionic chemistry

The aim of this paper is to introduce a synthetic concept suitable for the preparation of a broad variety of compounds. The so-called anhydride route (in this article the term anhydride is used for compounds derived from corresponding acids by formal loss of H2O, H2S and H2Se) has so far led to a range of unusual Group 15/16 ligands in oligomeric and polymeric environments. Commonly, reactions of neutral precursor molecules, for example, [{RP(S)(mu-S)}2] (R=4-anisyl) Lawesson's reagent or [{PhP(Se)(mu-Se)}2] Woollins's reagent and metal salts are performed to result in novel coordination compounds in which ligands and metal atoms form coordination oligomers and polymers. An attempt is made to relate the outcome of the investigations to the type of metal used. By relating the strength of ionic interactions, which correspond to metal-donor distances, to phenomena observed in the solid-state structures, an aspect of supraionic chemistry is described. Chemistry of and beyond novel Group 15/16 anions is further discussed using a novel approach in coordination chemistry where the chemical nature of ligands is unknown prior to the experiment despite the use of a range of similar starting materials.     

Functionalization of a cyclo‐P5 Ligand by Main‐Group Element Nucleophiles

Unprecedented functionalized products with an η⁴‐P₅ ring are obtained by the reaction of [Cp*Fe(η⁵‐P₅)] ( 1 ; Cp*=η⁵‐C₅Me₅) with different nucleophiles. With LiCH₂SiMe₃ and LiNMe₂, the monoanionic products [Cp*Fe(η⁴‐P₅CH₂SiMe₃)]^? and [Cp*Fe(η⁴‐P₅NMe₂)]^?, respectively, are formed. The reaction of 1 with NaNH₂ leads to the formation of the trianionic compound [{Cp*Fe(η⁴‐P₅)}₂N]^3?, whereas the reaction with LiPH₂ yields [Cp*Fe(η⁴‐P₅PH₂)]^? as the main product, with {[Cp*Fe(η⁴‐P₅)]₂PH}^2? as a byproduct. The calculated energy profile of the reactions provides a rationale for the formation of the different products.     

Fixation and Release of Intact E4 Tetrahedra (E=P,As)

By the reaction of [NacnacCuCH₃CN] with white phosphorus (P₄) and yellow arsenic (As₄), the stabilization and enclosure of the intact E₄ tetrahedra are realized and the disubstituted complexes [(NacnacCu)₂(μ,η^2:2‐E₄)] ( 1 a : E=P, 1 b : E=As) are formed. The mono‐substituted complex [NacnacCu(η²‐P₄)] ( 2 ), was detected by the exchange reaction of 1 a with P₄ and was only isolated using low‐temperature work‐up. All products were comprehensively spectroscopically and crystallographically characterized. The bonding situation in the products as intact E₄ units (E=P, As) was confirmed by theory and was experimentally proven by the pyridine promoted release of the bridging E₄ tetrahedra in 1 .     

反射光谱法研究稀土乙酰丙酮盐与二苯并18-冠-6新混配配合物

用反射光谱法通过积分球对所合成的14种稀土乙酰丙酮盐与二苯并18-冠-6新的混配配合物的紫外光谱进行研究,并与溶液透射光谱法作比较,结果表明固体反射光谱法比透射法得到更多的有用的信息。新配合物的形成使配体的n→π^*     

Novel Transition‐Metal (M=Cr,Mo, W,Fe) Carbonyl Complexes with Bis(guanidinato)silicon(II) Ligands

The donor‐stabilized silylene 2 (the first bis(guanidinato)silicon(II ) complex) reacts with the transition‐metal carbonyl complexes [M(CO)₆] (M=Cr, Mo, W) to form the respective silylene complexes 7 – 10 . In the reactions with [M(CO)₆] (M=Cr, Mo, W), the bis(guanidinato)silicon(II ) complex 2 behaves totally different compared with the analogous bis(amidinato)silicon(II ) complex 1 , which reacts with [M(CO)₆] as a nucleophile to replace only one of the six carbonyl groups. In contrast, the reaction of 2 leads to the novel spirocyclic compounds 7 – 9 that contain a four‐membered SiN₂C ring and a five‐membered MSiN₂C ring with a M?Si and M?N bond (nucleophilic substitution of two carbonyl groups). Compounds 7 – 10 were characterized by elemental analyses (C, H, N), crystal structure analyses, and NMR spectroscopic studies in the solid state and in solution.     

Complexes of Dichlorogermylene with Phosphine/Sulfoxide-Supported Carbone as Ligand

Due to their remarkable electronic features, recent years have witnessed the emergence of carbones L₂C, which consist in two donating L ligands coordinating a central carbon atom bearing two lone pairs. In this context, the phosphine/sulfoxide-supported carbone 4 exhibits a strong nucleophilic character, and here, we describe its ability to coordinate dichlorogermylene. Two original stable coordination complexes were obtained and fully characterized in solution and in the solid state by NMR spectroscopy and X-ray diffraction analysis, respectively. At 60 °C, in the presence of 4, the Ge(II)-complex 5 undergoes a slow isomerization that transforms the bis-ylide ligand into an yldiide.     

Magnetic Properties of Mixed Ligand NiII2 and NiII4 Complexes Composed of Macrocyclic Hexaamine‐Dithiophenolato and Bridging Tetrazolato Ligands

The magnetic properties of the dinuclear and tetranuclear nickel(II) tetrazolato complexes [Ni₂L(RCN₄)][BPh₄] (R = H ( 4 ), Me ( 5 ), Ph ( 6 )) and [(Ni₂L)₂(1,4‐(CN₄)₂‐C₆H₄)][BPh₄]₂ ( 7 ), where (L)^2– represents a 24‐membered macrocyclic N₆S₂ supporting ligand, are reported. Analysis of temperature‐dependent magnetic susceptibility measurements over the temperature range from 2 to 300 K revealed the presence of weak ferromagnetic exchange interactions between the Ni^II ions in the binuclear [Ni₂L(μ‐L′)]⁺ subunits with magnetic exchange coupling constant values of J₁ = 13.5 cm^–1 for 4 , J₁ = 20.0 cm^–1 for 5 , J₁ = 19.2 cm^–1 for 6 , and J₁ = 15.2 cm^–1 for 7 ( H = –2JS₁S₂). The exchange coupling J₂ across the bistetrazolato bridge in 7 is less than 0.1 cm^–1, which suggests that no significant interdimer coupling occurs in this compound. The synthesis and crystal structure of the new complex 7 ·2MeCN is also reported.     

Cationic Niobium-Sandwich and Piano-Stool Complexes

The syntheses of the homoleptic bis(arene) niobium cations [Nb(arene)₂]⁺ (arene = C₆H₃Me₃, C₆H₅Me) with 16 valence electrons and heteroleptic arene-carbonyl cations [(CO)Nb(arene)₂]⁺ (arene = C₆H₃Me₃, C₆H₅Me) and [(arene)M(CO)₄]⁺ (arene = C₆H₃Me₃, C₆H₆) obeying 18 valence electrons are described. Stabilization of these complexes was achieved by using the weakly coordinating anions [Al(OR^F)₄]⁻ or [F{Al(OR^F)₃}₂]⁻ (R^F = C(CF₃)₃). The limits of two synthesis routes starting from neutral Nb(arene)₂ (arene = C₆H₃Me₃, C₆H₅Me) or [NEt₄][M(CO)₆] (M = Nb, Ta) were investigated. All compounds were analyzed by single crystal X-ray determination, vibrational and NMR spectroscopy. DFT calculations were executed to support the experimental data.     

Prediction of the interaction of metallic moieties with proteins: An update for protein‐ligand docking techniques

In this article, we present a new approach to expand the range of application of protein‐ligand docking methods in the prediction of the interaction of coordination complexes (i.e., metallodrugs, natural and artificial cofactors, etc.) with proteins. To do so, we assume that, from a pure computational point of view, hydrogen bond functions could be an adequate model for the coordination bonds as both share directionality and polarity aspects. In this model, docking of metalloligands can be performed without using any geometrical constraints or energy restraints. The hard work consists in generating the convenient atom types and scoring functions. To test this approach, we applied our model to 39 high‐quality X‐ray structures with transition and main group metal complexes bound via a unique coordination bond to a protein. This concept was implemented in the protein‐ligand docking program GOLD. The results are in very good agreement with the experimental structures: the percentage for which the RMSD of the simulated pose is smaller than the X‐ray spectra resolution is 92.3% and the mean value of RMSD is < 1.0 Å. Such results also show the viability of the method to predict metal complexes–proteins interactions when the X‐ray structure is not available. This work could be the first step for novel applicability of docking techniques in medicinal and bioinorganic chemistry and appears generalizable enough to be implemented in most protein‐ligand docking programs nowadays available. © 2017 Wiley Periodicals, Inc.     

An Effective Approach to Obtain Near‐Infrared Emission from Binuclear Platinum(II) Complexes Involving Thiophenpyridine‐Isoquinoline Bridging Ligand in Solution‐Processed OLEDs

Bimetallic complexes have become an emerging hot topic in field of luminous applications in recent years. Unlike the traditional modification on a cyclometalated ligand, grafting an additional metal ion provides a novel approach to tune molecular conjugation as well as the spin orbital coupling (SOC). Herein, we demonstrate a new kind of binuclear platinum(II) complex Pt‐3 that possesses an asymmetric thiophenpyridine‐isoquinoline bridging ligand. Compared to its mononuclear analogues of Pt‐1 and Pt‐2, an extremely large redshift emission from 576 and 618 nm to 721 nm was observed in solution. Binding of two metal ions helps to enhance molecular planarity, extend conjugation and suppress excited state distortion. However, their quantum yields tend to remarkably decrease with increasing red‐shift emission as following the “energy gap law”. The relatively larger HOMO/LUMO separation that induced by the second platinum ion also decreases the oscillator strength at the lowest singlet state, and goes against the fast radiative decay process. Solution‐processed organic light‐emitting diodes (OLEDs) based on Pt‐1, Pt‐2 and Pt‐3 achieved external quantum efficiencies (EQEs) and luminance/radiant emittance of 13.6% and 13640 cd/m², 3.5% and 3754 cd/m², 0.9% and 7981 mW/Sr/m² with the corresponding electroluminescent (EL) emission peaked at 580 nm, 625 nm and 708 nm, respectively. This work emphasizes the complement argument of the commonly largely reported symmetric binuclear configurations, and provides a new view to photophysical mechanism and design strategies for bimetallic species.     

Highly Dynamic Coordination Behavior of Pn Ligand Complexes towards “Naked” Cu+ Cations

Reactions of Cu⁺ containing the weakly coordinating anion [Al{OC(CF₃)₃}₄]^? with the polyphosphorus complexes [{CpMo(CO)₂}₂(μ,η²:η²‐P₂)] ( A ), [CpM(CO)₂(η³‐P₃)] (M=Cr( B1 ), Mo ( B2 )), and [Cp*Fe(η⁵‐P₅)] ( C ) are presented. The X‐ray structures of the products revealed mononuclear ( 4 ) and dinuclear ( 1 , 2 , 3 ) Cu^I complexes, as well as the one‐dimensional coordination polymer ( 5 a ) containing an unprecedented [Cu₂( C )₃]²⁺ paddle‐wheel building block. All products are readily soluble in CH₂Cl₂ and exhibit fast dynamic coordination behavior in solution indicated by variable temperature ³¹P{¹H} NMR spectroscopy.     

E4 Transfer (E=P,As) to Ni Complexes

The use of [Cp′′₂Zr(η^1:1-E₄)] (E=P ( 1 a ), As ( 1 b ), Cp′′=1,3-di-tert-butyl-cyclopentadienyl) as phosphorus or arsenic source, respectively, gives access to novel stable polypnictogen transition metal complexes at ambient temperatures. The reaction of 1 a/1 b with [Cp^RNiBr]₂ (Cp^R=Cp^Bn (1,2,3,4,5-pentabenzyl-cyclopentadienyl), Cp′′′ (1,2,4-tri-tert-butyl-cyclopentadienyl)) was studied, to yield novel complexes depending on steric effects and stoichiometric ratios. Besides the transfer of the complete E_n unit, a degradation as well as aggregation can be observed. Thus, the prismane derivatives [(Cp′′′Ni)₂(μ,η^3:3-E₄)] ( 2 a (E=P); 2 b (E=As)) or the arsenic containing cubane [(Cp′′′Ni)₃(μ₃-As)(As₄)] ( 5 ) are formed. Furthermore, the bromine bridged cubanes of the type [(Cp^RNi)₃{Ni(μ-Br)}(μ₃-E)₄]₂ (Cp^R=Cp′′′: 6 a (E=P), 6 b (E=As), Cp^R=Cp^Bn: 8 a (E=P), 8 b (E=As)) can be isolated. Here, a stepwise transfer of E_n units is possible, with a cyclo-E₄²⁻ ligand being introduced and unprecedented triple-decker compounds of the type [{(Cp^RNi)₃Ni(μ₃-E)₄}₂(μ,η^4:4-E′₄)] (Cp^R=Cp^Bn, Cp′′′; E/E′=P, As) are obtained.     

Ring Opening and Bidentate Coordination of Amidinate Germylenes and Silylenes on Carbonyl Dicobalt Complexes: The Importance of a Slight Difference in Ligand Volume

The reactions of [Co₂(CO)₈] with one equiv of the benzamidinate (R₂bzam) group‐14 tetrylenes [M(R₂bzam)(HMDS)] (HMDS=N(SiMe₃)₂; 1 : M=Ge, R=iPr; 2 : M=Si, R=tBu; 3 : M=Ge, R=tBu) at 20 °C led to the monosubstituted complexes [Co₂{κ¹M?M(R₂bzam)(HMDS)}(CO)₇] ( 4 : M=Ge, R=iPr; 5 : M=Si, R=tBu; 6 : M=Ge, R=tBu), which contain a terminal κ¹M–tetrylene ligand. Whereas the Co₂Si and Co₂Ge tert‐butyl derivatives 5 and 6 are stable at 20 °C, the Co₂Ge isopropyl derivative 4 evolved to the ligand‐bridged derivative [Co₂{μ‐κ²Ge,N‐Ge(iPr₂bzam)(HMDS)}(μ‐CO)(CO)₅] ( 7 ), in which the Ge atom spans the Co?Co bond and one arm of the amidinate fragment is attached to a Co atom. The mechanism of this reaction has been modeled with the help of DFT calculations, which have also demonstrated that the transformation of amidinate‐tetrylene ligands on the dicobalt framework is negligibly influenced by the nature of the group‐14 metal atom (Si or Ge) but is strongly dependent upon the volume of the amidinate N?R groups. The disubstituted derivatives [Co₂{κ¹M?M(R₂bzam)(HMDS)}₂(CO)₆] ( 8 : M=Ge, R=iPr; 9 : M=Si, R=tBu; 10 : M=Ge, R=tBu), which contain two terminal κ¹M–tetrylene ligands, have been prepared by treating [Co₂(CO)₈] with two equiv of 1 – 3 at 20 °C. The IR spectra of 8 – 10 have shown that the basicity of germylenes 1 and 3 is very high (comparable to that of trialkylphosphanes and 1,3‐diarylimidazol‐2‐ylidenes), whereas that of silylene 2 is even higher.     

Theoretical investigation of clusters of phosphorus and arsenic: fascination and temptation of high symmetries

We present a theoretical study of the energetic and thermodynamic stability of selected phosphorus and arsenic clusters containing 18 to 168 atoms. For this purpose we employ MP2 as well as DFT functionals BP86 and B3LYP with extended basis sets. All procedures predict the family of one-dimensional polymers X18+12n, each with 2n-1 isomers of virtually identical energy, to be more stable than other structures investigated so far. Furthermore, islands of stability result for ring-shaped clusters X24n with Dnd symmetry for n=4 (only for arsenic), 5, 6, and 7. Phosphorus and arsenic show otherwise a very similar behavior. An investigation of basis set effects shows that a doubly polarized triple zeta valence basis (TZVPP) is both necessary and sufficient. In comparison to the reliable spin component scaled MP2 (SCS-MP2) procedure, DFT methods underestimate and MP2 overestimates the stability of larger clusters; the discrepancy increases with the number of atoms. The addition of a long-range dispersion correction to B3LYP energies does not rectify the shortcomings of DFT in comparison with SCS-MP2.