Syntheses, structure characterisation and X-ray studies of some mono, di- and tri-substituted cluster complexes of Ru3(CO)12 substituted by bulky fluorinated phosphine ligands

Five trinuclear substituted complexes of the type Ru₃(CO)₁₁L, Ru₃(CO)₁₀L₂ and Ru₃(CO)₉L₃ were synthesised by the reaction of Ru₃(CO)₁₂ with fluorine substituted phosphine ligands, {P(C₆H₄F-m)₃ and P(C₆H₄F-p)₃}, using the radical anion catalysed method. The structures of the resulting clusters were elucidated by means of elemental analyses and spectroscopic methods, which included IR, ¹H, ¹³C and ³¹P NMR spectroscopy. X-ray crystallographic studies of four of the complexes were carried out. In all the complexes, the ligand occupies an equatorial position due to steric reasons, and coordination of the ligand is observed only at the phosphorus atom. In the two monosubstituted complexes, Ru₃(CO)₁₁P(C₆H₄F-m)₃ and Ru₃(CO)₁₁P(C₆H₄F-p)₃, the effect of substitution resulted in an increase in the Ru-Ru distances. Out of the three Ru-Ru bonds, the one which is cis to the ligand is noticeably longer than the other two. The asymmetric unit of the disubstituted complex Ru₃(CO)₁₀{P(C₆H₄F-p)₃}₂ is composed of two molecules, A and B. As expected, the two phosphorus ligands are equatorially bonded to two different ruthenium atoms. The asymmetric unit of the trisubstituted complex is composed of one molecule of Ru₃(CO)₉{P(C₆H₄F-m)₃}₃ and one disordered solvent molecule. The structure consists of one triangular ruthenium complex in which each of the phosphorus ligands is equatorially bonded to three different ruthenium atoms. In the structure, disorder of the fluorine atoms is observed. Bond parameters, especially bond lengths and bond angles, are correlated to the structure and also are compared with the literature data of similar compounds.     

Binuclear and polynuclear transition metal complexes with macrocyclic ligands. 5. Novel complexes of asymmetric polydentate macrocyclic Schiff bases. Step-by-step synthesis

Reactions of 2,6-bis(3-aminopropylaminocarbonyl)pyridine (1) with 4-tert-butyl-2,6-diformylphenol and 2,5-diformylpyrrole in the presence of Ba(ClO₄)₂ in EtOH afford barium complexes with asymmetric macrocyclic Schiff bases as soft and hard ligands. The reaction of compound 1 with Cu(OCOCMe₃)₂ involves closure of a tetrahydropyrimidine ring to give a mononuclear complex, which was structurally characterized by X-ray diffraction analysis.     

A dihydrogen bond between a bridging hydride and the NH proton of a coordinated dimethylamine: solid state, solution and theoretical characterization

The addition of one equivalent of dimethylamine (DMA) to the 44 valence-electron triangular cluster anion [Re₃(μ₃-H)(μ-H)₃(CO)₉]⁻ (1) affords the novel unsaturated derivative [Re₃(μ-H)₄(CO)₉(DMA)]⁻ (2, 46 valence electrons) which contains a dimethylamine molecule terminally coordinated to a cluster vertex. Theoretical calculations (DFT) reveal that in the more stable conformation the dimethylamine NH proton is directed towards the hydride bridging the opposite cluster edge in syn position, the close proximity of the ligands bound to the cluster surface allowing the formation of an unconventional N-H ? (μ-H)Re₂ hydrogen bond. The presence of this conformation in the solid state has been proven by an X-ray structural analysis of crystalline [PPh₄]2. Spectroscopic evidences (IR and NMR) indicate that the dihydrogen bond is maintained also in solution and, by the evaluation of the proton spin-lattice relaxation rates at variable temperature, a good estimate of the H ? H distance in solution has been determined.     

The chemistry of trityl isoselenocyanate revisited: A preparative and structural investigation

The reaction of trityl chloride with KSeCN gives trityl isoselenocyanate which was structurally characterised by X-ray diffraction. Trityl isoselenocyanate reacts with hydrazine to give trityl selenosemicarbazide and with primary amines to give selenourea derivatives. However, with secondary amines mixtures of selenoureas and substitution products are formed. Trityl selenosemicarbazide undergoes a condensation reaction with salicylaldehyde to give the corresponding trityl selenosemicarbazone. In the case of 2-pyridinecarboxaldehyde, the analogous selenosemicarbazone cannot be isolated, instead a small quantity of the diselenide was isolated from the reaction mixture. The compounds prepared here were fully characterised spectroscopically and several also by X-ray diffraction.     

Versatile coordination chemistry of rhodium complexes containing the bis(trimethylsilylmethyl)tellane ligand

When RhCl₃ · 3H₂O was treated with an excess of Te(CH₂SiMe₃)_2, a mononuclear mer-[RhCl₃{Te(CH₂SiMe₃)₂}₃] (1) was observed as the main product. By reducing the metal-to-ligand molar ratio, dinuclear [Rh₂(μ-Cl)₂Cl₄{Te(CH₂SiMe₃)₂}₄] (2) was obtained in addition to 1. Further reduction of the metal-to-ligand ratio resulted in the formation of [Rh₂(μ-Cl)₂Cl₄(OHCH₂CH₃){Te(CH₂SiMe₃)₂}₃] (3). The treatment of mer-[RhCl₃(SMePh)₃] (4) with two equivalents of Te(CH₂SiMe₃)₂ affords a mixture of mer-[RhCl₃{Te(CH₂SiMe₃)₂}₃] (1) and mer-[RhCl₃{Te(CH₂SiMe₃)₂}₂(SMePh)] (5). All complexes 1-4 and 5 · ½EtOH were characterized by X-ray crystallography and ¹²⁵Te NMR spectroscopy, where appropriate. The definite assignment of the ¹²⁵Te chemical shifts enabled a plausible discussion of the assignment of some unknown resonances that were observed in the NMR spectra.     

Synthesis, coordination studies and redox properties of a novel ditertiary phosphine bearing two ferrocenyl groups

The new ferrocenyl substituted ditertiary phosphine {FcCH₂N(CH₂PPh₂)CH₂}₂ [Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅)] (1) was prepared, in 72% yield, by Mannich based condensation of the known bis secondary amine {FcCH₂N(H)CH₂}₂ with 2 equiv. of Ph₂PCH₂OH in CH₃OH. Phosphine 1 readily coordinates to various transition-metal centres including Mo⁰, Ru^II, Rh^I, Pd^II, Pt^II and Au^I to afford the heterometallic complexes {RuCl₂(p-cym)}₂(1) (2), (AuCl)₂(1) (3), cis-PtCl₂(1) (4), cis-PdCl₂(1) (5), cis-Mo(CO)₄(1) (6), trans,trans-{Pd(CH₃)Cl(1)}₂ (7) and trans,trans-{Rh(CO)Cl(1)}₂ (8). In complexes 2, 3, 7 and 8 ligand 1 displays a P,P′-bridging mode whilst for 4-6 a P,P′-chelating mode is observed. All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 1, 2 · 2CH₂Cl₂, 3 · CH₂Cl₂, 4 · CH₂Cl₂, 6 · 0.5CHCl₃ and 8 have been elucidated by single crystal X-ray crystallography. Electrochemical measurements have been undertaken, and their redox chemistry discussed, on both noncomplexed ligand 1 and representative compounds containing this new ditertiary phosphine.     

A Cationic Phosphapyramidane

Pyramidanes C[C₄R₄] constitute a novel class of highly strained and reactive polyhedral clusters that attracted a great deal of attention of both theoreticians and experimentalists. Although well‐studied from the theoretical viewpoint, pyramidanes were synthetically inaccessible, and only very recently their very first isolable representatives have been described. In this Communication, we report on the synthesis and structural studies of the cationic pyramidane with the Group 15 element at the apex, namely, phosphapyramidane, an isoelectronic analogue of the neutral pyramidanes of the Group 14 elements.     

Synthesis and crystal and molecular structures of six-coordinate tin dibromides and diiodides containing lactamomethyl C,O-chelating ligands

New (O−Sn)-bischelate bis(lactamomethyl)dibromo- and-diiodostannanes [L⁽ⁿ⁾]₂SnX₂ (L is the bidentate lactamomethyl C,O-chelating ligand;n is the size of the lactam ring, 5–7; X=Br or I) were prepared both by the direct method from metallic tin and the correspondingN-(halomethyl)lactams and by the reactions of dichlorides [L⁽ⁿ )]₂SnCl₂ with lithium halides. According to the data of X-ray diffraction analysis, the tin atom in [L⁽ⁿ⁾]₂SnBr₂ (n=5–7) and [L⁽ⁿ⁾]₂SnI₂ (n=5 or 6) adopts an octahedral configuration with the carbon atoms intrans positions and the coordinating oxygen and halogen atoms incis-positions with respect to each other. A comparison with the structures of analogous lactamomethyl halide derivatives of five-and six-coordinate Si, Ge, and Sn demonstrates that the spatial structures of the hypervalent fragments containing six-coordinate atoms are less sensitive to the replacement of the halide ligands and the central atom. The covalence of the M−Hal bond increases and the covalence of the M−O bond decreases in the series M=Si, Ge, and Sn. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1988–1998, October, 1999.     

Synthesis and structures of pyrimidinophanes containing a nitrogen atom in the bridge

The reactions of 1,3-bis(5-bromopentyl)-5-methyl-or 1,3-bis(5-bromopentyl)-6-methyl-uracil with benzylamine afforded pyrimidinophanes containing the nitrogen atom in the polymethylene bridge. Single-crystal X-ray diffraction study and NMR and UV spectroscopic study in solution demonstrated that the phenyl and uracil fragments in the macrocycles are in spatial proximity. Unlike the known macrocycles containing the pyrimidine ring, the pyrimidinophanes under study are conformationally rigid. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 539–547, March, 2006.     

Thermomorphic metal scavengers: A synthetic and multinuclear NMR study of highly fluorinated ketones and their application in heavy metal removal

The preparation of a ketone with two long chain perfluoroalkyl groups is reported via the coupling reaction of a perfluorinated alkylzinc reagent and a perfluoro-acid chloride. This ketone has been investigated in the heterogeneous removal of heavy metals M²⁺ (M = Sn, Cd, Pb, Hg) and As⁵⁺ from aqueous solutions and removal of these metals from organic solvents using the unique thermomorphic properties of the fluorous ketone. In addition, a comprehensive ¹³C NMR study of one of the intermediates in the synthesis, 2H,2H,3H,3H-perfluoronanoic acid, has allowed the determination of all ¹J_C-F and ²J_C-F coupling constants. Also reported is the crystal structure of the acid CF₃(CF₂)₅CH₂CH₂CO₂H.     

The Synthesis and Characterization of a New Layered Chlorozincophosphate Zn(HPO4)Cl[C4H10N]

Along a systematic study of open-framework materials aiming at producing new molecular sieves, we characterized a new zincophosphate Zn(HPO₄)Cl[C₄H₁₀N]. It was synthesized under mild conditions (r.t.) in the presence of pyrrolidinium as an organic-structure directing agent. The structure of this compound, determinated by single crystal X-ray diffraction, consists of anionic parallel [Zn(HPO₄)Cl]^? sheets alternating with thick slabs of organic molecules (C₄H₁₀N)⁺. These latters are linked to the anionic sheets through hydrogen bonds. Zn(HPO₄)Cl[C₄H₁₀N] crystallizes in the monoclinic system and the space group C2/c (No. 9) with cell parameters a = 24,83(9), b = 9,258(5), c = 8.778(3), β = 110,45(4), Z = 8, V = 1891.0(14) Åt³, R = 0.045, and R_w = 0.07. Solid state ³¹P and ¹³C MAS NMR spectroscopies are in agreement with the X-ray structure.     

Barium coordination polymers based on fluorinated and fluorine-free benzene-dicarboxylates: Mechanochemical synthesis and spectroscopic characterization

A series of new Ba-based coordination polymers (CPs) were mechanochemically synthesized by milling Ba-hydroxide samples with perfluorinated and fluorine-free benzene-dicarboxylic acids, including tetrafluoroisophthalic acid (H₂mBDC-F₄), tetrafluorophthalic acid (H₂oBDC-F₄), isophthalic acid (H₂mBDC) and phthalic acid (H₂oBDC). The new fluorinated CPs: [Ba(mBDC-F₄)·0.5H₂O] (1) and [Ba(oBDC-F₄)·1.5H₂O] (2) are compared to their nonfluorinated counterparts: [Ba(mBDC)·2.5H₂O] (3), and [Ba(oBDC)·1H₂O] (4). These materials are thoroughly characterized using powder X-ray diffraction. The products obtained by milling are all hydrated but vary in their water contents. Compositions and local structures are investigated by elemental analysis, thermal analysis, MAS NMR and attenuated total reflection-infrared spectroscopy. These materials exhibit high thermal stabilities but small surface areas that remain unchanged even after thermal treatments.     

Plasma and beam facility atomic oxygen erosion of a transition metal complex

Glassy residues of the complex bis(N,N-disalicylidene-1,2-phenylenediamino)zirconium(IV), Zr(dsp)₂, on glass slides were exposed to atomic oxygen in a plasma asher or an atomic beam facility for various amounts of lime in order to study the erosion process, determine the rate of erosion, and learn the chemical identity of the residue. The exposed films were characterized by weight loss, optical photography, profilometry, diffuse reflectance and total transmittance spectroscopy, scanning electron microscopy (SEM) with wavelength dispersive X-ray spectrometry (WDS), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Results indicate that these films erode much more slowly polyimide (Kapton) film under identical conditions, that the erosion is very nonuniform, and that zirconium dioxide is the predominant product after extended exposure. This complex is currently being evaluated as a polymer additive.     

Synthesis,Crystal Structure,and Conductivity Investigation of a New Monophosphate: (2-CH3OC6H4CH2NH 3)H2PO4

Chemical preparation, crystal structure, thermogravimetric and differential analysis, solid state ³¹P MAS NMR characterization, and IR spectroscopic investigations are given for a new organic cation dihydrogenmonophosphate, (2-CH₃OC₆H₄CH₂NH₃)H₂PO₄. This compound is monoclinic C2/c, with unit cell parameters a = 27.740(8), b = 4.827(2), c = 16.435(3) Å, β = 93.79(2)°, V = 2196 (1) ų, Z = 8, and ρ = 1.422 g · cm^?3. The crystal structure has been determined and refined to R = 0.046 (Rw = 0.056), using 1,746 independent reflections with I > 3σ (I). Its atomic arrangement can be described by infinite polyanions [H₂PO₄] _n ^{n ?}, organized in ribbons alternating with organic cations. Strong hydrogen bonds connect the different components. Electrical conductivity measurements show that the [2-CH₃OC₆H₄CH₂NH₃]H₂PO₄ has a low ionic conductivity value at 403 K.     

Out-cage metal ion coordination by novel benzoazacrown bisamides with carboxyl,pyridyl and picolinate pendant arms

A new series of macrocyclic diamides with carboxyl, pyridyl and picolinate pendant arms have been synthesized and the stability constants of their complexes with Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺ in water were determined. Complexes with a stoichiometry of 1 : 1 (M: L) were found for all ligands with the exception of 15-membered crown ethers with one pendant carboxyl or pyridine group. The ligand containing two picolinate backbone groups exhibits the highest values of the stability constants for all studied cations (logβ_ML?=?12.5–15.7). X-ray study of free ligands showed that the introduction of benzene and amide fragments into the macrocyclic moiety provides a flatten open structure of the ligand. The crystallographic analysis of Cu²⁺ and Zn²⁺ complexes revealed the external coordination of the metal atom by amine N atoms of the macrocycle and heteroatoms of the pendant groups.     

NMR spectroscopy in coordination supramolecular chemistry: A unique and powerful methodology

Metal-mediated self-assembly is emerging as a very important strategy for the synthesis of supramolecular species. Still, a major challenge in coordination supramolecular chemistry continues to be the characterization of the self-assembled complexes and the investigation of their dynamic behaviour in solution. In this context, NMR spectroscopy appears as a unique and powerful methodology. This practical-oriented review describes the rich variety of NMR techniques which are applied to the investigation of different aspects of the structure and behaviour of supramolecular complexes. “Classic” 1D NMR spectra reflect characteristic chemical shifts due to metal–ligand interactions or encapsulation phenomena, as well as symmetry and chiral properties of host–guest assemblies. Mainstream ¹H, ¹³C, ¹⁹F and ³¹P spectra are eventually complemented by the use of NMR-active metal nuclides. Homo- and heteronuclear 2D correlation experiments are ubiquitous in the literature, providing through-bond and through-space connectivities. Increasingly, diffusion measurements are also gaining popularity in this field, being used to gain information about molecular size, intermolecular interactions and even association constants of supramolecular complexes. Knowledge about the thermodynamic properties and the dynamic behaviour of coordination supramolecular assemblies is essential for the development of their practical applications. The most frequently used NMR methodologies for the calculation of association constants (simple signal integration, NMR titration and diffusion measurements) and for the investigation of dynamic supramolecular equilibria (lineshape analysis, selective inversion recovery experiments and 2D EXSY spectra) are described, together with the use of variable-temperature investigations for the determination of the thermodynamic and activation parameters of self-assembly and encapsulation processes.     

Estimation of composition,coordination model,and stability constant of some metal/phosphate complexes using spectral and potentiometric measurements

Complexation reactions in a binary metal/phosphate system were studied. Protolytic equilibria of phosphate in the presence of cobalt, nickel, iron, copper, chromium and silver metal ions were investigated by potentiometric titrations in the pH range of 2–11. Stability constants of the metal/phosphate complexes were determined by computer analysis of the potentiometric titration. Potentiometric titrations suggest that the presence of metal phosphate and metal hydrogen phosphate provides the solutions with stability constants logK _c 2.21, 2.11, 2.23, 2.34, 1.96, and 2.14 of Co, Ni, Fe, Ag, Cr, and Cu/phosphate, respectively. The results of infrared spectroscopy, X-ray powder diffraction and equilibrium studies were used to reveal the mode of interaction between the metal ions and phosphate. Metal phosphates with a hydrogen phosphate anion and fully nonprotonated phosphate could be isolated under the reaction conditions.     

A novel energetic nickel coordination compound based on carbohydrazide and dinitramide

Dinitramide was reacted with carbohydrazide to furnish the corresponding mono- and bis-susbtituted salts. The nickel salt of dinitramide when reacted with carbohydrazide produced the coordination compound, tris(carbohydrazide- N,O)nickel(ii) bis-dinitramide, whose crystal structure was characterized by X-ray diffraction.     

X-Ray and NMR Structural Data of Ethynylbenziodoxolones (EBXs) Reagents and Their Analogues

First synthesized in 1991, EthynylBenziodoXolones (EBXs) – cyclic hypervalent iodine reagents derived from 2-iodobenzoic acid – are now among the most versatile electrophilic alkynylation reagents. Due to their cyclic structure, these reagents exhibit enhanced stability compared to previously used alkynyl iodonium salts. Over the last decade, both the iodoheterocycle and the arene ring have been extensively modified to fine-tune the reactivity of the reagents, resulting in new analogues such as Ethynylbenziodoxoles (EBxs) or N-heterocyclic reagents. In this article, we have for the first time compiled the structural data available for EBXs and their analogues, focusing especially on X-Ray and NMR data. For selected compounds, molecular electrostatic potentials (MEP) have also been calculated. When considering the tight relationship between structure and reactivity in hypervalent iodine reagents, the collected data is expected to be highly useful for further developments in the field.     

Binuclear and polynuclear transition metal complexes with macrocyclic ligands. 2. New macrocyclic Schiff"s base in the reaction of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene. Synthesis and structural,spectroscopic, and theoretical study

Condensation of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene in ethanol is accompanied by partial reduction of the azomethine double bonds to form symmetrical macrocyclic Schiff"s base containing the alternating >C=N and >CH—NH fragments. In solution, this compound exists as the only isomer in which two endocyclic hydrogen atoms are bound to the oxygen atoms of the phenol groups and two other endocyclic H atoms are attached to the nitrogen atoms of the CH₂—NH fragments. All endocyclic protons are involved in hydrogen bonding and undergo rapid exchange with each other at room temperature. In the crystal, the planar macrocyclic molecules are arranged in closely packed stacks. The steric hindrances resulting from overlapping of the bulky tert-butyl groups are eliminated through rotation of the molecules with respect to each other in the adjacent layers. Study of the potential energy surface for the Schiff"s base under consideration by the DFT method demonstrated that the structure corresponding to the global minimum is similar to that found in solution. However, the isolated molecule is nonplanar, its macrocycle adopting a ladder conformation. The local minimum on the potential energy surface whose energy is 2.6 kcal mol^–1 higher than that of the global minimum corresponds to the zwitterionic structure in which all four endocyclic hydrogen atoms are attached to the nitrogen atoms and the macrocycle adopts a tub conformation. Flattening of the ring is considered as a consequence of stacking interactions between the molecules in the crystal.