Molecular and Crystal Structures of Pentafluorophenyl‐platinum(II) Complexes with Bis(diphenylphosphino)methane,Bis(diphenylarsino)methane and 1,2‐Bis(diphenylarsino)ethane

The X‐ray crystal structures of [PtCl₂(dppm)], [Pt(C₆F₅)₂L] (L = dppm (bis(diphenylphosphino)methane), dpam (bis(diphenylarsino)methane), dpae (bis(diphenylarsino)ethane)) and [PtCl(C₆F₅)(dpae)] show the complexes to be monomeric with chelating dipnictido ligands, and not alternatives with bridging ligands. In [Pt(C₆F₅)₂(dpam)₂], there are two unidentate diarsine ligands in a cis‐arrangement.     

Cationic Crown Ether Complexes of Germanium(II)

Fit for a king : Cationic complexes of Ge^II can be prepared by using crown ethers to stabilize and protect the germanium center. Three different crown ethers were employed: [12]crown‐4 (see structure, Ge teal, O red, C gray), [15]crown‐5, and [18]crown‐6. The structures of the cationic complexes depend on the cavity size of the crown ether and on the substituent on germanium.

     

Pyrimidino- and Proton-ionizable Pyrimidono-crown Ether Ligands: Synthesis and Preliminary Complexation Studies

Pyrimidino-crown ethers were prepared in 30-50% yields by reactingthe ditosylate derivative of the appropriate oligoethylene glycol with4-methoxy-5-methyl-2,6-pyrimidinedimethanol under basic conditions. A newmacrocyclic ligand containing a proton-ionizable pyrimidone subcyclic unitwas prepared in 88% yield by treating the appropriatepyrimidino-crown ether with 5 M NaOH in 50% (v/v) aqueous methanol.Preliminary complexation properties of some of these new compounds werestudied using various NMR spectral techniques. Good enantiomeric recognitionwas exhibited by a chiral pyrimidino-crown ether for the enantiomers of1-(-naphthyl)ethylammonium perchlorate.     

Delocalization and Valence Tautomerism in Vanadium Tris(iminosemiquinone) Complexes

To survey the noninnocence of bis(arylimino) acenaphthene (BIAN) ligands (L) in complexes with early metals, the homoleptic vanadium complex, [V(L)₃] ( 1 ), and its monocation, [V(L)₃]PF₆ ( 2 ), were synthesized. These complexes were found to have a very rich electronic behavior, whereby 1 displays strong electronic delocalization and 2 can be observed in unprecedented valence tautomeric forms. The oxidation states of the metal and ligand components in these complexes were assigned by using spectroscopic, crystallographic, and magnetic analyses. Complex 1 was identified as [V^IV(L^red)(L^.)₂] (L^red=N,N′‐bis(3,5‐dimethylphenylamido)acenaphthylene; L^.=N,N′‐bis(3,5‐dimethylphenylimino)acenaphthenesemiquinonate). Complex 2 was determined to be [V^V(L^red)(L^.)₂]⁺ at T<150 K and [V^IV(L^.)₃]⁺ at T>150 K. Cyclic voltammetry experiments reveal six quasi‐reversible processes, thus indicating the potential of this metal–ligand combination in catalysis or materials applications.     

Bis(oxofluorenediyl)oxacyclophanes: Synthesis,Crystal Structure and Complexation with Paraquat in the Gas Phase

The first three representatives of the new family of oxacyclophanes incorporating two 2,7‐dioxyfluorenone fragments, connected by [‐CH₂CH₂O‐]_m spacers (m=2–4), have been synthesized. The yield of the smallest oxacyclophane (m=2) is considerably higher with respect to the larger ones (m=3 and m=4), which are formed in comparable yields. Molecular modeling and NMR spectra analysis of the model compounds suggest that an essential difference in oxacyclophanes yields is caused by formation of quasi‐cyclic intermediates, which are preorganized for macrocyclization owing to intramolecular π–π stacking interactions between the fluorenone units. The solid‐state structures of these oxacyclophanes exhibit intra‐ and intermolecular π–π stacking interactions that dictate their rectangular shape in the fluorenone backbone and crystal packing of the molecules with the parallel or T‐shape arrangement. The crystal packing in all cases is also sustained by weak C? H ??? O hydrogen bonds. FAB mass spectral analysis of mixtures of the larger oxacyclophanes (m=3 and m=4) and a paraquat moiety revealed peaks corresponding to the loss of one and two PF₆^? counterions from the 1:1 complexes formed. However, no signals were observed for complexes of the paraquat moiety with the smaller oxacyclophane (m=2). Computer molecular modeling of complexes revealed a pseudorotaxane‐like incorporation of the paraquat unit, sandwiched within a macrocyclic cavity between the almost parallel‐aligned fluorenone rings of the larger oxacyclophanes (m=3 and m=4). In contrast to this, only external complexes of the smallest oxacyclophane (m=2) with a paraquat unit have been found in the energy window of 10 kcal mol^?1.     

Complexation between Methyl Viologen (Paraquat) Bis(Hexafluorophosphate) and Dibenzo[24]Crown‐8 Revisited

Paraquat bis(hexafluorophosphate) undergoes stepwise dissociation in acetone. All three species—the neutral molecule, and the mono‐ and dications—are represented significantly under the experimental conditions typically used in host–guest binding studies. Paraquat forms at least four host–guest complexes with dibenzo[24]crown‐8. They are characterized by both 1:1 and 1:2 stoichiometries, and an overall charge of either zero (neutral molecule) or one (monocation). The monocationic 1:1 host–guest complex is the most abundant species under typical (0.5–20 mM ) experimental conditions. The presence of the dicationic 1:1 host–guest complex cannot be excluded on the basis of our experimental data, but neither is it unambiguously confirmed to be present. The two confirmed forms of paraquat that do undergo complexation—the neutral molecule and the monocation—exhibit approximately identical binding affinities toward dibenzo[24]crown‐8. Thus, the relative abundance of neutral, singly, and doubly charged pseudorotaxanes is identical to the relative abundance of neutral, singly, and doubly charged paraquat unbound with respect to the crown ether in acetone. In the specific case of paraquat/dibenzo[24]crown‐8, ion‐pairing does not contribute to host–guest complex formation, as has been suggested previously in the literature.     

Kristallstrukturelle,Festkörper‐31P‐CP/MAS‐NMR,TOSS, 31P‐COSY‐NMR und mechanistische Beiträge zur Koordinationschemie des Octacarbonyldicobalts mit den Liganden Bis(diphenylphosphanyl)amin,Bis(diphenylphosphanyl)methan und 1,1,1‐Tris(diphenylphosphanyl)ethan

Chemistry of Polyfunctional Molecules. 133. X‐Ray Crystal Structural, Solid‐state ³¹P CP/MAS NMR, TOSS, ³¹P COSY NMR, and Mechanistic Contributions to the Co‐ordination Chemistry of Octacarbonyldicobalt with the Ligands Bis(diphenylphosphanyl)amine, Bis(diphenylphosphanyl)methane, and 1,1,1‐Tris(diphenylphosphanyl)ethane Co₂(CO)₈ reacts with bis(diphenylphosphanyl)amine, HN(PPh₂)₂ (Hdppa, 1 ), in two steps to afford the known compound [Co(CO)(Hdppa‐κ²P)₂][Co(CO)₄] · 2 THF ( 6 a · 2 THF). The intermediate [Co(CO)₂(Hdppa‐κ²P) · (Hdppa‐κP)][Co(CO)₄] · dioxane · n‐pentane ( 5 · dioxane · n‐pentane) was isolated for the first time and was characterized by X‐ray analysis. The cation 5 ⁺ exhibits a slightly distorted trigonal‐bipyramidal geometry. Detailed ³¹P‐NMR investigations (solid‐state CP/MAS NMR, TOSS, ³¹P‐COSY, ³¹P‐EXSY) showed that the additional tautomer [Co(CO)₂(Hdppa‐κ²P)(Ph₂P–N=P(H)Ph₂‐κP)]⁺ ( 5 ′⁺) is present in solution. The tautomer equilibrium is slow in the NMR time scale. In contrast to the solid state only tetragonal pyramidal species of 5 are found in solution. At –90 °C there is slow exchange between the three diastereomeric species 5 a ⁺– 5 c ⁺. Compound 5 forms [Co(CO) · (Hdppa‐κ²P)₂]BPh₄ · THF ( 6 b · THF) in THF with NaBPh₄ under CO‐Elimination. A X‐ray diffraction investigation shows that the cation 6 ⁺ consists of a slightly distorted trigonal‐bipyramidal co‐ordination polyeder. However, a distorted tetragonal‐pyramidal structure has been found for the cation 7 ⁺ of the related compound [Co(CO)(dppm)₂][Co(CO)₄] · 2 THF ( 7 · 2 THF; dppm = bis(diphenylphosphanyl)methane, Ph₂PCH₂PPh₂). A comparison with the known [8] trigonal‐bipyramidal stereoisomer, ascertained for 7 ⁺ of the solvent‐free 7 , is described. In solutions of 6 a · 2 THF and 7 · 2 THF ¹³C{¹H}‐ and ³¹P{¹H}‐NMR spectra indicate an exchange of all CO and organophosphane molecules between cobalt(I) cation and cobalt(–I) anion. A concerted mechanism for the exchange process is discussed. CO elimination leads to discontinuance of the cyclic mechanism by forming binuclear substitution products such as the isolated Co₂(CO)₂ · (μ‐CO)₂(μ‐dppm)₂ · 0.83 THF ( 8 · 0.83 THF), which was characterized by spectroscopy and X‐ray analysis. For the dissolved [Co(CO)₂CH₃C(CH₂PPh₂)₃][Co(CO)₄] · 0.83 n‐pentane ( 9 a · 0.83 n‐pentane) no CO and triphos exchange processes between the cation and the anion are observed. Metathesis of 9 a · 0.83 n‐pentane with NaBPh₄ yields [Co(CO)₂CH₃C(CH₂PPh₂)₃]BPh₄ ( 9 b ) which has been characterized by single‐crystal X‐ray analysis. The cation shows a small distorted tetragonal‐pyramidal structure.     

Synthese,Spektren und Strukturen einfacher Derivate des Tris(bis(trimethylsilyl)methyl)indiums,In(CH(Si(CH3)3)2)3

Syntheses, Spectra, and Structures of Simple Derivatives of Tris(bis(trimethylsilyl)methyl Indium, In(CH(Si(CH₃)₃)₂)₃ Like trimethyl- or triethylindium tris(disyl)indium, In(CH(SiMe₃)₂)₃ (≙ InR₃) also reacts with equimolar amounts of water, D₂O, MeOH, HCl and HCOOH, respectively, in ether solution at room temperature to form the corresponding alkane, here (Me₃Si)₂CH₂, and the simple monosubstitution products R₂InX. With the dibasic oxalic and sulfuric acid the multinuclear derivatives (R₂In)₂C₂O₄ and [RIn(R₂In)₂(SO₄)₂]₂ are formed, respectively. The halogenides R₂InCl, RInCl₂, and RInBr₂ have been prepared by metathesis from InHal₃ and InR₃ (molar ratios 1 : 2 and 2 : 1). The ¹H, ¹³C, and ²⁹Si NMR- as well as the vibrational spectra (IR, Raman) are discussed. According to the X-ray structure elucidations the monosubstitution products R₂InX (with X = OH, OMe, Cl) are dimeric in the solid state and consist of planar, centrosymmetric fourmembered In₂X₂ skeletons. The dibromide RInBr₂ forms a polymeric chain structure with five-fold co-ordinated metal centres and vertex linked, alternately appearing planar as well as slightly folded In₂Br₂-moities. The “sesquisulfate” [R₅In₃(SO₄)₂]₂ has an uncommon, cage-like structure with four as well as five-fold co-ordinated In atoms. The structural data could not be optimally refined due to the highly disordered disyl groups.     

Synthese,Kristallstruktur und spektroskopische Charakterisierung von [Au12(PPh)2(P2Ph2)2(dppm)4Cl2]Cl2

Synthesis, Crystal Structure and Spectroscopic Characterization of [Au₁₂(PPh)₂(P₂Ph₂)₂(dppm)₄Cl₂]Cl₂ The reaction of [(AuCl)₂dppm] (dppm = Ph₂PCH₂PPh₂) with P(Ph)(SiMe₃)₂ in CHCl₃ results in the formation of [Au₁₂(PPh)₂(P₂Ph₂)₂(dppm)₄Cl₂]Cl₂ ( 1 ), the crystal structure of which was determined by single crystal X‐ray analysis (space group P2₁/c, a = 1425.3(3) pm, b = 2803.7(6) pm, c = 2255.0(5) pm, β = 95.00(3)°, V = 8977(3)·10⁶ pm³, Z = 2). The dication in 1 consists of two Au₆P₃ units built by highly distorted Au₃P and Au₂P₂ heterotetrahedra, connected via four bidentate phosphine ligands. Additionally, the compound was characterized by IR‐, UV‐ and NMR spectroscopy. The ³¹P{¹H} NMR spectrum is discussed in detail.     

Chemie polyfunktioneller Moleküle. 124. Silber(I)-Komplexe mit den Liganden Bis(diphenylphosphanyl)amin, -amid und Tris(diphenylphosphanyl)amin

Chemistry of Polyfunctional Molecules. 124. Silver(I) Complexes Containing the Ligands Bis(diphenylphosphanyl)amine, -amide and Tris(diphenylphosphanyl)amine Bis(diphenylphosphanyl)amine HN(PPh₂)₂ ( 1 ) reacts with AgCl to the complex HN(PPh₂AgCl)₂ ( 5 ) for which in the solid state the cluster structure Ag₄Cl₄[HN(PPh₂)₂]₂ is assumed. Reaction of 5 with LiN(PPh₂)₂ ( 2 ) gives the known [N(PPh₂AgPh₂P)₂N] ( 8 ) and the new complex [Ag(μ—Ph₂PNPPh₂)₂(μ—Ph₂PNHPPh₂)Ag] · dioxane ( 7 · dioxane). The compound 7 · dioxane has been characterized by X-ray diffraction. The molecules are found to contain a bicyclo[3.3.3]undecane-type structure with trigonal planar coordinated silver atoms, which are separated by 281,6(1) pm. The dioxane is bound via H-bridge bond to the NH group of the coordinated HN(PPh₂)₂. Treatment of 8 with ClPPh₂ yields N(PPh₂AgCl)₃ ( 12 ), which has also been obtained by the reaction of N(PPh₂)₃ ( 3 ) with silver chloride. All the compounds have been characterized, so far as possible, by IR, Raman, ¹H NMR, ³¹P{¹H} NMR, ¹³C{¹H} NMR and mass spectroscopy.     

Complexation of a Macrocycle Containing Thiopyrimidine and Uracil Moieties with Dicarboxylic and Amino Acids in Various Organic and Aqueous Organic Solutions

The complexation of a macrocycle containing thiopyrimidine and uracil moieties (M) with amino acids and some dicarboxylic acids was studied by pH-metric, UV-VIS, ¹H NMR spectroscopy methods in chloroform, methanol, aqueous 1,4-dioxane, and biphasic water–chloroform media. The complexation of M with acids is too weak to solubilize them from the solid state into chloroform solutions containing M. The ¹H NMR spectra and pH-metric data of aqueous 1,4-dioxane (80 vol.%) reveal the pH-dependent 1:1 binding between M and the acids studied. The protonation of M is not a prerequisite for binding of fumaric, succinic, o-phtalic acids and the series of amino acids, whereas binding of maleic acid requires the protonation of both thiopyrimidine moieties of M. Therefore,M·(H⁺)₂ exhibits strong selectivity towards maleic acid in aqueous 1,4-dioxane and in biphasic water–chloroform media.