On the reactivity of less common halopseudohalogens towards metalcarbon- and metalmetal-bonded compounds

Freshly generated solutions of iodine azide (IN₃) and iodine isocyanate (INCO) in acetonitrile or carbon tetrachloride add oxidatively to tertiaryaryl derivatives of group VB elements, Ar₃M (Ar = Ph, p-tolyl, p-ClC₆H₄ or p-FC₆H₄, and M = As, Sb or Bi) and diaryltellurium(II), Ar₂Te (Ar = Ph or p-CH₃OC₆H₄) at −10°C to −5°C to give stable covalent monomeric products, Ar₃MIX and Ar₂TeIX, respectively (where X = N₃ or NCO). The mode of bonding of the pseudohalide group to M has been established by solid-state IR spectra. Ar₃MI(N₃) failed to react with CS₂ but reaction with PhNCY (Y = O or S) gave cyclic tetrazole derivatives. Contrasting behaviour was also observed in the metathetic reaction of Ar₂MIX and Ar₂TeIX with silver pseudohalides [AgX′ (X′ = NCO or NCS)]. The tetraorgano compounds, R₄M (M = Sn or Pb, and R = Ph or p-tolyl), and Bu₃SnPh failed to react with IN₃ and Bu₃SnPhINCO but IN₃ cleaved one tin-aryl bond from Ar₄Sn in the presence of AlCl₃. Addition of IN₃ and INCO across the olefinic bond of Ph₃SnCH₂CHCH₂ is preferred to tin-allyl bond cleavage. Reactions of hexaaryldileads with IN₃ and INCO under appropriate conditions proceeded with the cleavage of a PbPb bond. Parallel reactions of cyanogen halides (CNI and CNBr) resulted in the formation of corresponding triaryllead halides and pseudohalide derivatives.     

Synthesis,Structure and Nickel Carbonyl Complexes of Dialkylterphenyl Phosphines

The experimental and computational characterization of a series of dialkylterphenyl phosphines, PR₂Ar′ is described. The new P-donors comprise five compounds of general formula PR₂Ar (R=Me, Et, iPr, c-C₅H₉ and c-C₆H₁₁); Ar = 2,6-C₆H₃-(3,5-C₆H₃-(CMe₃)₂)₂), and another five PR₂Ar′ phosphines containing the bulky alkyl groups iPr, c-C₅H₉ or c-C₆H₁₁, in combination with Ar′=Ar , Ar , or Ar ( L1 – L10 ). Steric and electronic parameters have been determined computationally and from IR and X-ray data obtained for the phosphines and for some derivatives, including tricarbonyl and dicarbonyl nickel complexes, Ni(CO)₃(PR₂Ar′) and Ni(CO)₂(PR₂Ar′). In the solid state, the free phosphines PR₂Ar′ adopt one of the three possible structures formally related by rotation around the C_ipso−P bond. Details on their relative energies and on the influence of the free phosphine structure on its coordination chemistry towards Ni(CO)_n (n = 2, 3) fragments has been obtained by experimental and computational methods.     

Mono- and bisphenoxy derivatives of bis(indenyl) titanium(IV)

A series of (C₉H₇)₂Ti(OAr)Cl and (C₉H₇)₂Ti(OAr)₂ complexes whereAr=C₆H₅,p-ClC₆H₄, α-C₁₀H₇ or β-C₁₀H₇, have been synthesised by the reaction of bis(indenyl) titanium(IV) dichloride with an appropriate phenol in a 1:1 and 1:2 molar ratio in refluxing benzene in the presence of triethylamine. The new derivatives have been characterized on the basis of their elemental analyses, conductance measurements and spectral (IR,¹H-NMR and electronic) studies.     

Die Umsetzung von Diphenylphosphinigsäurechlorid mit Natriumsalzen von aromatischen Sulfinsäuren zu Diphenylphosphinsäure-S-arylestern

Zusammenfassung Die Umsetzung von Diphenylphosphinigsäurechlorid mit Alkalisalzen aromatischer Sulfinsäuren führt unter Reduktion am Schwefel, Oxydation am Phosphor und Ausbildung einer Bindung zwischen Phosphor und Schwefel, zu Diphenylthiophosphinsäure-S-arylestern: (C₆H₅)₂P(O)–S–Ar (Ar=C₆H₅, 4-CH₃C₆H₄, 4-ClC₆H₄, 2-Cl-5-CH₃-C₆H₃, 2-C₁₀H₇). Die besten Ausbeuten (40–85%) wurden mitDMF als Lösungsmittel erhalten. Aliphatische Phosphinigsäurechloride geben keine Bindung zwischen P und S. Ebenso tritt keine Umsetzung ein, wenn im Säurechlorid eine P–O-Struktur vorliegt. Auch die Umsetzung von (C₆H₅)₂PCl und (C₆H₅)₂P(O)Cl mit Sulfonsäuren anstelle der Sulfinsäuren führt zu keiner P–S-Verknüpfung. Diese Phosphor-Schwefel-Bindung in den Thiophosphinsäure-S-estern stellt die schwächste Stelle im Molekül dar, da ein hydrolytischer, oxydativer oder reduktiver Angriff diese Bindung wieder löst.

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Reaction of diphenylchlorophosphine with alkali salts of aromatic sulfinic acids leads to diphenylthiophosphinates; reduction occurs at the sulfur atom, oxidation at the phosphorus atom and a bond between phosphorus and sulfur is formed: (C₆H₅)₂P(O)–S–Ar, Ar=C₆H₅, 4-CH₃C₆H₄, 2-ClC₆H₄, 2-Cl-5-CH₃-C₆H₃, 2-C₁₀H₇. The best yields were obtained in dimethyl formamide as solvent. With aliphatic chlorophosphines no bond formation beetween sulfur and phosphorus occurred. Similarly no reaction was observed, when a phosphorus atom in a higher state of oxidation was present, as for example in diphenylphosphonylchloride. Also, no reaction took place when sulfonic instead of sulfinic acids were used. The weakest bond found to exist in the diphenylthiophosphinates was the P–S-linkage, which readily undergoes hydrolytic, oxidative or reductive cleavage.

     

Synthesis of Zwitter-Ionic Conjugate of Nido-Carborane with Cholesterol

9-HC≡CCH₂Me₂N-nido-7,8-C₂B₉H₁₁, a previously described carboranyl terminal alkyne, was used for the copper(I)-catalyzed azide-alkyne cycloaddition with azido-3β-cholesterol to form a novel zwitter-ionic conjugate of nido-carborane with cholesterol, bearing a 1,2,3-triazol fragment. The conjugate of nido-carborane with cholesterol, containing a charge-compensated group in the linker, can be used as a precursor for the preparation of liposomes for BNCT (Boron Neutron Capture Therapy). The solid-state molecular structure of a nido-carborane derivative with the 9-Me₂N(CH₂)₂Me₂N-nido-7,8-C₂B₉H₁₁ terminal dimethylamino group was determined by single-crystal X-ray diffraction.     

Synthesis of homoleptic tris(organo-chelate)iridium(III) complexes by spontaneous ortho-metallation of electronrich olefin-derived N,N′-diarylcarbene ligands and the X-ray structures of fac-[Ir{CN(C6H4Me-p) (CH2)2NC6H3Me-p}3] and mer-Ir{CN(C6H4Me-p)(CH2)2NC6H3Me-p}2 {CN(C6H4Me-p)(CH2)2NC6H4Me-p}Cl (a product of HCl cleavage)

Treatment of [{Ir(COD)(μ-Cl)}₂] with excess of the electron-rich olefin [$\text{CN(Ar)(CH}{}_2\text{)}{}_2\text{N}$Ar]₂ (abbreviated as (L^Ar)₂, Ar = C₆H₄Me-p or C₆H₄OMe-p) affords the ortho-metallated tricycle [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₃], which for Ar = C₆H₄Me-p (Ia) with HCL yields [$\text{Ir(L}{}^{\mathrm{A}}\text{r}$)₂(L^Ar)]Cl (IV); X-ray data show that in IV there is an unexpectedly close Ir?C(o-aryl) contact (2;52(1) Å) involving the “free” L^Ar which compares with an IrC(o-aryl) distance of 2.09(3) Å in Ia or 2.07(3) Å in the ortho-metallated L^Ar ligand of complex IV.     

Insertion of isocyanides into the palladium-(2-pyridyl) bond

The reaction of the pyridyl-bridged binuclear complex [PdBr(μ-2-C₅H₄N)(PPh₃)]₂ with isocyynides CNR (R  p-C₆H₄OMe, Me, C₆H₁₁) yields the complex $\text{PdBr}${(&2.dbnd;NR)C(&2.dbnd;NR) (2-C₅H₄N)}(PPh₃)] containing a C,N-chelated 1,2-bis(imino)-2-(2-pyridyl)ethyl group, which results from successive insertions of two isocyanides molecules into the palladium2-pyridyl bond. The mononuclear compound trans-[PdBr(2-C₅H₄N)(PMePh₂)₂] readily reacts with various CNR ligands (R  p-C₆H₄OMe, Me, C₆H₁₁, CMe₃) to give the imino(2-pyridyl)methylpalladium(II) derivatives, trans-[Pdbr{C(=NR)(2-C₅H₄N)} (PMePh₂)₂].     

Fluorescent Orthopalladated Complexes of 4-Aryliden-5(4H)-oxazolones from the Kaede Protein: Synthesis and Characterization

The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4H)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the ortho carbon of the arylidene ring. Two different 4-((Z)-arylidene)-2-((E)-styryl)-5(4H)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring (1a OMe; 1b F), were used as starting materials. Oxazolones 1a and 1b were reacted with Pd(OAc)₂ to give the corresponding dinuclear orthometalated palladium derivates 2a and 2b by regioselective C–H activation of the ortho-position of the arylidene ring. Reaction of 2a (2b) with LiCl promoted the metathesis of the bridging carboxylate by chloride ligands to afford dinuclear 3a (3b). Mononuclear complexes containing the orthopalladated oxazolone and a variety of ancillary ligands (acetylacetonate (4a, 4b), hydroxyquinolinate (5a), aminoquinoline (6a), bipyridine (7a), phenanthroline (8a)) were prepared from 3a or 3b through metathesis of anionic ligands or substitution of neutral weakly bonded ligands. All species were fully characterized and the X-ray determination of the molecular structure of 7a was carried out. This structure has strongly distorted ligands due to intramolecular interactions. Fluorescence measurements showed an increase in the quantum yield (QY) by up to one order of magnitude on comparing the free oxazolone (QY < 1%) with the palladated oxazolone (QY = 12% for 6a). This fact shows that the coordination of the oxazolone to the palladium efficiently suppresses the hula-twist deactivation pathway.     

Synthesis and polycondensation of some new organic tellurium compounds containing mono- and di-amino groups

Several new and known organic tellurium compounds containing amino groups (i.e. ArTeBr₃, Ar₂Te₂ and Ar₂Te, where Ar= 4-NH₂C₆H₄, 2-NH₂C₆H₄, 4-CH₃CONHC₆H₄ or 2-NH₂-5-NO₂-C₆H₃) were prepared by reacting aminoarylmercury chlorides with tellurium tetrabromide in glacial acetic acid. Bis(4-aminophenyl) telluride and bis(2-amino-5-nitrophenyl) telluride were polymerized with aromatic and aliphatic diacid chlorides (i.e. terephthaloyl chloride and sebacoyl chloride), as well as with toluene di-isocyanate, leading to new organic tellurium polyamides and polyurea. All organic tellurium compounds and their condensation polymers were characterized by elemental analyses, IR, ¹H and ¹³C NMR, and mass spectroscopy. The thermal stabilities of the resulting polymers were determined by thermogravimetric and derivative thermogravimetric techniques. © 1998 John Wiley & Sons, Ltd.     

Synthesis of a Hexameric Magnesium 4-pyridyl Complex with Cyclohexane-like Ring Structure via Reductive C-N Activation

The reaction of [{(^Arnacnac)Mg}₂] (^Arnacnac = HC{MeC(NAr)}₂, Ar = 2,6-diisopropylphenyl, Dip, or 2,6-diethylphenyl, Dep) with 4-dimethylaminopyridine (DMAP) at elevated temperatures afforded the hexameric magnesium 4-pyridyl complex [{(^Arnacnac)Mg(4-C₅H₄N)}₆] via reductive cleavage of the DMAP C-N bond. The title compound contains a large s-block organometallic cyclohexane-like ring structure comprising tetrahedral (^Arnacnac)Mg nodes and linked by linear 4-pyridyl bridging ligands, and the structure is compared with other ring systems. [(^Dipnacnac)Mg(DMAP)(NMe₂)] was structurally characterised as a by-product.     

Zwitterionic metal carboxylate complexes: In solid state

A flexible dicarboxylic acid having composition [(CH(o-C₅H₄N)(p-C₆H₄OCH₂CO₂H)₂] derived from corresponding bis-phenol reacts with various metal(II) acetates such as manganese(II), cobalt(II) and nickel(II) acetate leads to zwtterionic complexes with compositions [CH(o-C₅H₄N)(p-C₆H₄OCH₂CO₂){p-C₆H₄OCH₂CO₂M(H₂O)₅}].6H₂O (where M = Mn, Co, Ni). The complexes are characterised by X-ray crystallography. These complexes have chiral center due to unsymmetric structure conferred to the ligand through coordination at only one carboxylate group of the ligand. In solid state these complexes are racemic.     

Solvent-Controlled Self-Assembled Oligopyrrolic Receptor

We report a fully organic pyridine-tetrapyrrolic U-shaped acyclic receptor 10, which prefers a supramolecular pseudo-macrocyclic dimeric structure (10)₂ in a less polar, non-coordinating solvent (e.g., CHCl₃). Conversely, when it is crystalized from a polar, coordinating solvent (e.g., N,N-dimethylformamide, DMF), it exhibited an infinite supramolecular one-dimensional (1D) “zig-zag” polymeric chain, as inferred from the single-crystal X-ray structures. This supramolecular system acts as a potential receptor for strong acids, e.g., p-toluenesulfonic acid (PTSA), methane sulfonic acid (MSA), H₂SO₄, HNO₃, and HCl, with a prominent colorimetric response from pale yellow to deep red. The receptor can easily be recovered from the organic solution of the host–guest complex by simple aqueous washing. It was observed that relatively stronger acids with pK_a < −1.92 in water were able to interact with the receptor, as inferred from ¹H NMR titration in tetrahydrofuran-d₈ (THF-d₈) and ultraviolet–visible (UV–vis) spectroscopic titrations in anhydrous THF at 298 K. Therefore, this new dynamic supramolecular receptor system may have potentiality in materials science research.     

A Comparative 19F NMR study of electronic effects in some fluoroaryl compounds of antimony and bismuth and in their carbon and nitrogen analogues

A number of m- and p-fluorophenyl compounds of type Ar₂QC₆H₄F (Q = Sb, Bi, N and CH; Ar = C₆H₅, C₆H₄F) have been prepared. The ^l0F chemical shifts relative to fluorobenzene have been measured in cyclohexane, chloroform and pyridine for all these compounds. On the basis of the data obtained, the electronic nature of the Ar₂Sb and Ar₂Bi substituents has been studied and compared with that of the corresponding (C₆H₅)₂N and (C₆H₅)₂CH groups. The electronic effect of the Ar₂Sb and Ar₂Bi substituents has been shown to be mainly inductive, its solvent susceptibility being in most cases close to zero relative to both electron- and proton- donating solvents.     

Ferrocene-Containing Pseudorotaxanes in Crystals: Aromatic Interactions with Hammett Correlation

Single crystals of pseudorotaxanes, [(FcCH₂NH₂CH₂Ar)(DB24C8)][PF₆] (DB24C8 = dibenzo[24]crown-8, Fc = Fe(C₅H₄)(C₅H₅), Ar = -C₆H₃-3,4-Cl₂, -C₆H₃-3,4-F₂, -C₆H₄-4-F, -C₆H₄-4-Cl, -C₆H₄-4-Br, -C₆H₃-3-F-4-Me, -C₆H₄-4-I) and [(FcCH₂NH₂CH₂C₆H₄-4-Me)(DB24C8)][Ni(dmit)₂] (dmit = 1,3-dithiole-2,4,5-dithiolate), were obtained from solutions containing DB24C8 and ferrocenylmethyl(arylmethyl)ammonium. X-ray crystallographic analyses of the pseudorotaxanes revealed that the aryl ring of the axle moiety and the catechol ring of the macrocyclic component were at close centroid distances and parallel or tilted orientation. The structures with parallel aromatic rings showed correlation of the distances between the centroids to Hammett substituent constants of the aryl groups.     

Synthetic and spectroscopic studies of some mono-hydrido-bridged complexes of platinum(II)

The mono-hydrido-bridged complexes (PEt₃)₂(Ar)Pt(μ₂-H)Pt(Ar)(PEt₃)₂]-[BPh₄] (Ar = Ph, 4-MeC₆H₄ and 2,4-Me₂C₆H₃) have been obtained by treating trans-[Pt(Ar)(MeOH)(PEt₃)₂][BF₄] with sodium formate and Na[BPH₄]. The cations [PEt₃)₂(Ar)Pt(μ₂-H)Pt(Ar^b')(PEt₃)₂]^b+ (Ar = Ph and Ar^b' - 2,4-Me₂C₆H₃ and 2,4,6-Me₃C₆H₂ have bee identified in solution. Their ^b1H- and ^b31P-NMR data are reported. The X-ray crystal structure of [(PEt₃)₂(Ph)Pt(μ₂-H)Pt(Ph)(PEt₃)₂][BPh₄] is reported.     

Synthesis, characterization and the crystal structure of 1-[(N-methyl-N-aryl)amino]ethylferrocenes

The reactions of ferrocenylketimines [(η⁵-C₅H₄CCH₃NAr)Fe(η⁵-C₅H₅)] (Ar=a variety of substituted phenyls) with methyl-iodide in refluxed dichloromethane followed by reduction with sodium borohydride in absolute ethanol led to [(η⁵-C₅H₄CH(CH₃)N(CH₃)Ar)Fe(η⁵-C₅H₅)]. Compound [(η⁵-C₅H₄CH(CH₃)N(CH₃)C₆H₄Cl-p)Fe(η⁵-C₅H₅)] (3d) has been characterized structurally. Compound 3d is monoclinic, space group P2₁/n, with a=8.908(2) Å, b=13.63(1) Å, c=14.510(3) Å and β=107.03°.     

Electron capture by tetra- and di-chlorobenzene molecules. Comparative studies by position annihilation and ODESR methods

Experiments on inhibition and anti-inhibition of Ps formation and also on optical detection of ESR spectra in squalene solutions with 1,2,4,5-C₆H₂Cl₄ and p-C₆H₄Cl₂ have demonstrated the presence of short-lived molecular radical-anions (products of the spur electron capture by additives), their lifetimes being longer than roughly 10 ps and shorter than 10–30 ns. The cross section of electron capture by p-C₆H₄Cl₂ in squalane is nearly one-tenth of that by 1,2,4,5-C₆H₂Cl₄ and CCl₄ at concentration ? 0.02 M, while 10% of the electrons cannot be trapped even at 0.25 M p-C₆H₄Cl₂. Probably the electrons in the high-electric-field (0.3–3 MV/cm) regions of the spurs cannot be effectively captured by p-C₆H₄Cl₂, which is a shallow electron trap. Similar effects of the high electric fields of the charged spur series seem to influence the Ps formation appreciably, along with the other effects discussed in previous papers. Several new results can be predicted, by use of this interpretation. Both methods employed are emphasized to be selective with respect to geminate spur particles.     

The thiolate anion as a nucleophile Part III. Reactions with various fluorobenzenes

The reactions of the fluorobenzenes, C₆F₅H, o-C₆H₂F₄, m-C₆H₂F₄, p-C₆H₂F₄, 1,3,5-C₆F₃H₃, 1,2,4-C₆F₃H₃, o-C₆F₂H₄, m-C₆F₂H₄, p-C₆F₂H₄ and C₆F₅H with thiolate anion nucleophiles RS^? (primarily MeS^?), have been studied in ethylene glycol/pyridine mixtures as a solvent. Multiple replacement of fluorine atoms was observed in the more highly fluorinated compounds, but in all cases two aromatic fluorine atoms were not replaced. Difluorobenzene and fluorobenzene did not react. The product orientations have been deduced from their NMR spectra. The mass spectra of the isomeric products C₆F₂H₃(SMe), C₆F₃H₂(SMe) and C₆F₂H₂(SMe)₂ have been examined.     

Electronegativity and chemical hardness of organoelement groups

The experimental approaches to estimation of comparative electronegativity and chemical hardness of organometallic groups have been proposed. Qualitative data on the electronegativity of L _nM groups were obtained from ¹⁹F NMR study of model systems 4‐FC₆H₄QML_n (Q = CC, N(R), O, C(O)O, S), (4‐FC₆H₄)₃ SnML _n and (4‐FC₆H₄)₃SnQML _n (Q = O, S), containing a great variety of different organometallic groups containing transition or heavy main‐group metals. The data on chemical hardness of L _nM groups were obtained from NMR study of distribution of different L _nM groups between hard and soft anions. The following basic results have been obtained. (1) The relative electronegativity and chemical hardness of L _nM groups can change in parallel or not with the electronegativity and hardness of the central metal atom. (2) The substituents in Ar can substantially modify electronegativity and hardness of Ar _nM groups; the influence of Ar groups has an inductive nature; the increase in electron‐donating ability of aryl ligands enhances the hardness of Ar _nM cations. (3) The relative electronegativity and hardness of L _nM groups in L _nMX are invariant and do not depend on X.     

ortho-, meta- and para-nitrophenylgold(I) complexes

Treatment of [BzPh₃P][AuCl₂] with [Hg(x-C₆H₄NO₂)₂] (x = o, m, or p) gives anionic gold(I) complexes of the type [BzPh₃P][Au(R)Cl](R = o-, m- or p-C₆H₄NO₂, Bz = C₆H₅CH₂). The chloro ligand in [Au(o-C₆H₄NO₂)Cl]^? can be replaced by bromo or iodo ligands by use of NaBr or NaI. The anions [Au(R)Cl]^? react with neutral monodentate ligands, L, to give neutral mononuclear complexes [Au(R)L] (R = o-C₆H₄NO₂, L = PPh₃, AsPh₃; R = m-C₆H₄NO₂, L = PPh₃) and with 1,2-bis(diphenylphosphino)ethane (dpe) to give [Au₂(R)₂(dpe)] (R = o-C₆H₄NO₂). The corresponding [Au(p-C₆H₄NO₂)Cl]^? reacts with PPh₃ or AsPh₃ to give mixtures containing [AuClL]. The anionic ortho-nitrophenylgold(I) complex is much more stable than its meta- or para-nitrophenyl isomers. These are thought to be the first reports of nitrophenylgold(I) complexes.