Showing papers by "Peter G. Jones published in 2008"

Synthesis and reactivity of copper(I) complexes with an ethylene-bridged bis(imidazolin-2-imine) ligand

Abstract: A series of copper(I) complexes with a sterically hindered, bidentate ligand, BL iPr, derived from an N-heterocyclic carbene precursor have been isolated, characterized and their reactivity studied. The ethylene-bridged bis(imidazolin-2-imine) ligand (BL iPr) provides strongly donating N-donor atoms for the stabilization of a copper(I) metal center, priming it for reactivity. The complexes [(BL iPr)Cu(XyNC)]PF6 (4) and [(BL iPr)CuCl] (5) were characterized by X-ray crystallography and exhibit trigonal coordination at the copper centers. The reactivity of [(BL iPr)Cu]SbF6 toward dioxygen was studied at low temperature, indicating formation of a thermally sensitive intermediate with intense UV/Vis features and an isotope-sensitive vibration at 625 cm(-1) (599 cm(-1) with 18 O2). The intermediate is assigned as containing the bis(mu-oxo)dicopper(III) core, [2](PF6)2, and the related, stable hydroxo form was crystallized as [{(BL iPr)Cu}2(mu-OH)2](PF6)2, [3](PF6)2. The reactivity of 5 as a catalyst for the ATR polymerization of styrene was assessed in terms of reaction kinetics and polymer properties, with low PDI values achieved for polymers with molecular weights up to 30 000 g mol(-1).

Rare Earth and Alkaline Earth Metal Complexes with Me2Si-Bridged Cyclopentadienyl-Imidazolin-2-Imine Ligands and Their Use as Constrained-Geometry Hydroamination Catalysts

Abstract: The imidazolin-2-imino-functionalized tetramethylcyclopentadiene, 3-H, has been prepared by the reaction of two equivalents of 1,3-diisopropyl-4,5-dimethylimidazolin-2-imine (1) with 5-(chlorodimethylsilyl)-1,2,3,4-tetramethyl-1,3-cyclopentadiene (2). The reactions of 3-H with the trimethylsilylmethyl (neosilyl) [Ln(CH2SiMe3)3(THF)2] (Ln = Sc, Y, Lu) complexes afford tetramethylsilane and the constrained-geometry [(η5:η1-3)Ln(CH2SiMe3)2] (Ln = Sc, 4a; Ln = Y, 4b; Ln = Lu, 4c) complexes, whereas the analogousbis(trimethylsilyl)amido (HMDS) calcium complex, [(η5:η1-3)Ca(HMDS)(THF)] (5), can be obtained from 3-H and [Ca(HMDS)2(THF)2] with loss of hexamethyldisilazane, (Me3Si)2NH. The molecular structures of 4a–4c and 5 have been established by X-ray diffraction analyses, which confirm in all cases the formation of complexes with a chelating Me2Si-bridged cyclopentadienyl-imidazolin-2-imine ligand. The presence of short Ln–N and Ca–N bonds is indicative of the strong electron-donating capacity of the imidazolin-2-imino nitrogen atom, which is based on the ability of the imidazolium ring to effectively stabilize a positive charge. The rare earth metal complexes 4a–4c can be used as efficient catalysts for the hydroamination/cyclization reaction of terminal aminoalkenes and aminoalkynes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

MP2 and DFT Calculations on Circulenes and an Attempt to Prepare the Second Lowest Benzolog, [4]Circulene

Abstract: MP2 and DFT calculations have been carried out for [n]circulenes for n=3 to 20 in order to predict the strain energy and topology of these cyclically condensed aromatic systems. To synthesise [4]circulene (2), 1,5,7,8-tetrakis(bromomethyl)biphenylene (14) was prepared from the corresponding tetramethyl derivative (8) and subjected to various dehalogenation reactions; all attempts to obtain [2.2]biphenylenophane (7) as a precursor for 2 by this route failed. Treatment of 14 with sodium sulfide furnished the thiaphanes 16 and 17, thermal and photochemical desulfurization of which also failed to provide 7. In a second approach [2.2]paracyclophane was converted to the pseudo-geminal dithiol 23, which was subsequently bridged to the thiaphanes 22 and 24. On flash vacuum pyrolysis at 800 °C these were converted exclusively into phenanthrene (30). An approach to dehydrochlorinate the commercial product PARYLENE C® to the tetrahydro[4]circulene 7 led only to polymerisation. The X-ray structures of the intermediates 8, 14, 17, 23, 24, 26, and 35 are reported.

Sterically and polarity-controlled reactions of tBuLi with P=CH-NR heterocycles: novel heterocyclic P- and P,O-ligands and preliminary tests in transition-metal catalysis.

Abstract: (1R)-1,3-Benzazaphospholes 1 a-c, P=CH-NR heterocycles of the indole type, react with tBuLi in two ways, depending on the steric demand of the N-substituent and the polarity of the medium. The presence of small N-alkyl groups induces CH-deprotonation in the 2-position to give hetaryllithium reagents 2 a and 2 b, whereas bulky N-substituents and nonpolar solvents change the reactivity towards addition at the P=C bond. The preferred regioselectivity is tert-butylation at phosphorus, occurring with excellent diastereoselectivity for trans-adducts 3 b and 3 c, but the inverse tert-butylation at C2 to 5 b was also observed. N-Neopentyl groups, with intermediate steric demand, give rise to formation of mixtures in ethers but allow switching either to selective CH lithiation in THF/KOtBu or to addition in pentane. Bulkier N-adamantyl groups always cause preferred addition. Protonation, silylation, and carboxylation were used to convert the P=CLi-NR, (E)-tBuP-CHLi-NR, and LiP-CH(tBu)-NR species into the corresponding sigma(2)-P or sigma(3)-P compounds 4 b and 6 a,b, 7 b,c, or 8 b-10 b with additional N and/or O donor sites. Slow diffusion-controlled air oxidation of 10 b led to the meso-diphosphine 11 b. Preferred eta(1)-P coordination was shown for an [Rh(cod)Cl] complex 12 b, and the potential of the new ligands 4 b and 7 b in catalysis was demonstrated by examples of Pd-catalyzed C-N coupling and Ni-catalyzed ethylene oligomerization (TON>6300). Crystal structures of 6 b, 11 b, and 12 b are presented.

Preparation of Ti(IV) fluoride N-heterocyclic carbene complexes.

Abstract: 1,3,4,5-Tetramethylimidazol-2-ylidene (LMe) and 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (LiPr) readily form complexes of trans-TiF4(LMe)2 (1) and of trans-TiF4(LiPr)2 (4) with TiF4 in THF, respectively. Complex 1 has been used as a precursor for preparing the Ti(IV) fluoride carbene complexes [{TiF2(LMe)(NEt2)}2(μ-F)2] (2) and (TiF4(LMe)2)(NacNacLi) (3) (NacNac = HC(CMeN(2,6-iPr2C6H3))2). Complex 2 was prepared from the reaction of 1−3 equiv of 1 and 1 equiv of Ti(NEt2)4 or by reacting TiF4 with Ti(NEt2)4 and LMe in toluene. Complex 3 has been prepared from 1 and NacNacLi in toluene. Reaction of 1 and AlMe3 in toluene results in ligand transfer and formation of AlMe3(LMe). Complex 4 is unstable in solution at room temperature and degrades with formation of [HLiPr][TiF5(LiPr)] (5). Complexes 1, 2·2CH2Cl2, 4, and 5 were characterized by single crystal X-ray structural analysis, elemental analysis, IR and NMR spectroscopy, and mass spectrometry. The relative basicities of LMe, LiPr, and the donor liga...

Soft–Soft Interactions Involving Iodoselenophosphonium Cations: Supramolecular Structures of Iodine Adducts of Bulky Trialkylphosphane Selenides

Abstract: The reactions of trialkylphosphane selenides tBu n iPr 3-n PSe (n = 3: la; n = 2: 1b; n = 1: 1c; n = 0: 1d) with iodine are studied with the help of heteronuclear NMR spectroscopy, vibrational spectroscopy, and X-ray crystal structure determinations. The reaction of la with one equivalent of iodine provides, after crystallization from dichloromethane/pentane, solid 2a, which consists of pairs of molecular adducts tBu 3 PSe-I-I, together with chains of alternating [(tBu 3 PSe) 2 I] + and I 3 - ions. The addition of iodine to 1b, 1c, and 1d in a 1:1 molar ratio furnishes ionic solids with the formulation [(tBu n -iPr 3-n PSe) 2 I] + [I 3 ] - (n = 2: 2b; n = 1: 2c; n = 0: 2d). Compounds 2a-2d exhibit supramolecular structures based on various kinds of weak Se···I and Se···Se interactions. In 2a, the uncharged molecules form dimers through Se···Se contacts, while the anions and cations assemble to form chains through linear P-Se···I anion contacts. The ionic compounds 2b and 2d consist of the same type of chains, although they are not isotypic to each other. The two independent formula units of 2c are topologically different; one forms cation-anion chains analogous to those of 2b and 2d, whereas the other forms cation chains through Se···Se contacts. Se···I contacts between the latter chains and triiodide anions are very long but seem to be structurally significant; for such contacts, at well above the sum of the van der Waals radii, we propose the term tertiary contacts. On using more than one equivalent of I 2 , compounds corresponding to the formulation tBu n -iPr 3-n PSeI x (x = 3, n = 3: 3a; x = 4, n = 1: 4c; x = 7, n = 2 and 0: 5b and 5d) were isolated as single crystals. Ionic 3a contains pairs of cations [(tBu 3 PSe) 2 I] + , connected by Se···Se contacts, located between corrugated layers of polymeric I 5 -anions. Compound 4c consists of two independent formula units tBuiPr 2 PSeI 2 ·I 2 , which could, however, be regarded as tBuiPr 2 PSeI + ·I-·I 2 because of the long I-I distance adjacent to Se. To a fair approximation, the packing of the two units is independent; unit 1 forms dimers (···Se-I-I···I-I···) 2 , whereas the same motif in unit 2 forms chains. The structural subunits are linked through further contacts involving terminal iodine atoms from tBuiPr 2 PSeI···I units, which thereby form μ 3 -bridging units, and by additional I-I···Se contacts. In 5b, iodide-bridged cations [tBu 2 iPrPSeI···I···ISePiPrtBu 2 ] + are anchored to a polyiodide network of formal composition I 11 -[= (I - )(I 2 ) 5 ] through I···I contacts. Except for one I···I contact, the polyiodide is two-dimensional, although highly puckered. In 5d, [iPr 3 PSeI] + cations and I 2 molecules exhibit weak I...I interactions with I- units from puckered square-net-like polyiodide layers.

Synthesis of optically active hydroxyphosphonates

Abstract: The reduction of dimenthyl ketophosphonates with sodium borohydride involves asymmetric induction at the α-carbon atom, resulting in a small excess of the (R)-enantiomer of the α-hydroxyphosphonate formed. A higher ee purity was achieved if the reduction of chiral dimenthyl ketophosphonates was carried out by the chiral complex of NaBH4-L-proline, owing to the double asymmetric induction at the α-carbon atom. The hydroxyphosphonates obtained were isolated in a diastereomerically pure state and were transformed to the optically active, free hydroxyalkylphosphonic acids. The (R)-configuration of one of them was proved by X-ray crystal structure analysis. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:133–139, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20391

Ethyl 4-(3-benzoyl-thio-ureido)benzoate.

Abstract: The title compound, C17H16N2O3S, crystallizes in the thio­amide form with an intra­molecular N—H⋯O hydrogen bond across the thio­urea system. Mol­ecules are connected in chains parallel to [10\overline{1}] by hydrogen bonds from the second thio­urea N—H group to the benzoate C=O function.

Ethyl 4-(3-butyrylthio-ureido)benzoate.

Abstract: The title compound, C14H18N2O3S, crystallizes in the thio­amide form with an intra­molecular N—H⋯O hydrogen bond associated with the thio­urea unit. With the benzoic acid and the butyrylthio­ureido units, the mol­ecule consists of two planar building blocks connected by the common NH function adjacent to the aromatic ring. The inter­planar angle is 33.38 (3)°. Mol­ecules are connected in chains parallel to [110] by classical hydrogen bonds of the N—H⋯O type from the other NH group to the benzoate C=O of a neighboring mol­ecule.

Structural Characterization of Cationic 16-Electron Pentamethylcyclopentadienyl Ruthenium(II) Complexes Containing the Binuclear [Cp*Ru(μ-Cl)3RuCp*]– Anion

Abstract: The reaction of the diimine ligand 1,2-bis(1,3-diisopropyl-4,5-dimethylimidazolin-2-imino)ethane (BLⁱᴾʳ) with tetrameric [Cp*RuCl]₄ in a 1 : 0.75 ratio afforded the complex salt [1][2] containing the 16-electron half-sandwich cation [Cp*Ru(BLⁱᴾʳ)]+ (1) and the dinuclear anion [Cp*Ru(μ- Cl)₃RuCp*]⁻ (2). The X-ray crystal structures of [1][2]·31/2THF (monoclinic, space group P2₁/n, Z = 4) and of [1][2]·THF (monoclinic, space group C2/m, Z = 4) are reported, allowing the structural characterization of the unprecedented anion 2, in which two [(η⁵-C₅Me₅)Ru(II)] moieties are bridged by three μ₂-chlorine atoms.

Metal Complexes with Mono-and Bis{[bis(2-pyridyl)amino]carbonyl}ferrocene Ligands

Abstract: The ligands {[bis(2-pyridyl)amino]carbonyl}ferrocene (L1) and 1,1′-bis{[bis(2-pyridyl)amino]carbonyl}ferrocene (L2) have been prepared by treatment of the mono- or 1,1′-bis(chlorocarbonyl)ferrocene derivatives with dipyridylamine in a 1:1 or 1:2 ratio, respectively. The ligand properties of these compounds towards group 11 and palladium complexes have been studied. Ligand L1 coordinates to these compounds to give four-coordinate [Cu(L1)2]+, [PdCl2(L1)] and [Ag(OTf)(L1)(PR3)] or three-coordinate [Ag(OTf)(L1)] and [Au(C6F5)(L1)] compounds. The ligand coordinates in a chelate fashion in all cases. The reactivity of L2 is somewhat different because coordination to copper or silver atoms can take place through several pyridine units either from different cyclopentadienido rings, as in [Cu(L2)]+, [Ag2(OTf)2(L2)] and [Ag(OTf)(L2)(PPh3)], or from the same cyclopentadienido ring, as in [Ag2(OTf)2(L2)(PPh3)2]. Coordination as a bridging ligand for four gold atoms has also been achieved in [Au4(C6F5)4(L2)] and [Au4(L2)(PPh3)4](OTf)4. The ligands and some complexes have been characterized by X-ray diffraction studies and show the presence of several hydrogen bonds that lead to supramolecular structures.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Coordination Behaviour of Gold and Silver Towards Pyrazole Ligands

Abstract: Treatment of pyrazole ligands HL (HL = pyrazole or 3,5-dimethylpyrazole) with the gold(I) compound [Au(C 6 F 5 )(tht)] (tht = tetrahydrothiophene) gives either the complexes [Au(C 6 F 5 )(HL)] or, if the reaction is carried out in a molar ratio of 1:2 and in the presence of a base, the pyrazolate compound [NBu 4 ][{Au(C6F5)} 2 (μ-L)]. Binuclear derivatives with bridging pyrazolate ligands have been obtained by treatment of the ligands with [O(AuPPh 3 ) 3 ][ClO 4 ] or [Au 2 Cl 2 (μ-dppf)] (dppf = 1,1'-bis(diphenylphosphanyl)ferrocene) and Na 2 CO 3 , to give [(AuPPh 3 ) 2 (μ-L)][ClO 4 ] or [Au 2 (μ-L)(μ-dppf)]Cl. Treatment of [Ag(OTf)(PPh 3 )] with the pyrazole ligands affords the dimeric species [Ag 2 (μ-OTf) 2 (HL) 2 (PPh 3 ) 2 ]. Gold(III) derivatives have been accessed by treatment of the pyrazole ligands with [Au(C6F5)3(OEt 2 )] or [Au(C 6 F 5 )2(OEt2) 2 ]-[ClO 4 ], affording the species [Au(C 6 F 5 ) 3 (HL)] or [Au(C 6 F 5 ) 2 -(HL) 2 ][ClO 4 ]. Gold(III) pyrazolate derivatives of the form trans-[NBu 4 ][Au(C 6 F 5 ) 2 Cl(L)] or [(AU(C 6 F 5 ) 2 } 2 (μ-L) 2 ] have been prepared from [NBu 4 ][Au(C 6 F 5 ) 2 Cl 2 ] or [Au(acac)-(C 6 F 5 ) 2 ]. X-ray structural characterization has been carried out for eight compounds.

Peptides and uses thereof

Abstract: The invention relates to fragments of Chromogranin A (CgA) derived peptide fragments and their use in methods of therapy, for example in the treatment of diabetes etc The peptides, for example AL-11, GV-19 and WE-14, are tropic, ie stimulate release of regulatory substances and may be used in the absence of a stimulatory concentration of glucose

Polysulfonylamine. CLXXXIII. Neues aus der Festkörperchemie der Di(arensulfonyl)amine: Silber(I)‐di(4‐iod‐ benzolsulfonyl)amid, eine Schichtverbindung mit strukturdirigierenden Ag–I–C‐Motiven, und Di(4‐fluorbenzolsulfonyl)amin‐Monohydrat, eine Säulenstruktur mit intracolumnaren Wasserketten und intercolumnaren Wasserstoffbrücken C–H···F–C

Abstract: Polysulfonylamines. CLXXXIII. Novel Solid-State Aspects of Di(arenesulfonyl)amines: Silver(I) Di(4-iodobenzenesulfonyl)amide, a Layer Compound Displaying Structure-Directing Ag–I–C Motifs, and Di(4-fluorobenzenesulfonyl)amine Monohydrate, a Column Structure Exhibiting Intracolumnar Water Chains and Intercolumnar C–H···F–C Hydrogen Bonds Low-temperature X-ray structures are reported for (4-I–C6H4SO2)2NAg (1, triclinic, , Z′ = 1) and (4-F–C6H4SO2)2NH·H2O (2, orthorhombic, Pna21, Z′ = 2). Whereas metal di(arenesulfonyl)amides usually display folded anions (C–S···S′–C′ synperiplanar) and crystallize in lamellar layers, compound 1 has an extended anion (C–S···S′–C′ antiperiplanar) and forms non-lamellar striated layers in which the ions are connected by Ag–N/Ag–O bonds in one dimension and by Ag–I–C interactions, C–I···O halogen bonds and weak π/π ring interactions in the other dimension. The silver ion adopts a trigonal-bipyramidal pentacoordination comprising two long axial Ag–O bonds (259 and 261 pm), one short Ag–N bond (228 pm) and two structure-determining Ag–I bonds (289 and 294 pm, Ag–I–C 107 and 109°). An analysis of Ag···I–C contacts < 340 pm extracted from the Cambridge Structural Database (25 structures, 63 contacts) reveals that the Ag–I–C angles lie between 90 and 110° for contacts < 300 pm, whereas for longer interactions, the directionality rapidly becomes weaker; this result is in keeping with the electrophile/nucleophile model for interactions involving halogen atoms bonded to carbon. In the structure of compound 2, a dimer of two independent water molecules is repeated via glide planes to give a chain in which water 1 acts as a difunctional hydrogen bond donor and water 2 as a difunctional acceptor. The extended disulfonylamine molecules are connected to water 1 by N–H···O(w), to water 2 by O(w)–H···O=S bonds. The resulting supramolecular polymer is a square column that is reinforced by C–H···O=S hydrogen bonds and π/π interactions and bears four one-dimensional sets of fluorine atoms at the vertices. Dense packing of these columns causes all the fluorine atoms to segregate into parallel tunnels and to form short C–H···F–C intercolumnar contacts strongly suggestive of weak hydrogen bonding (H···F 240–250 pm, C···F 328–346 pm, C–H···F 137–148°).

Polysulfonylamine. CLXXXIV. Kristallstrukturen molekularer Triphenylphosphangold(I)‐di(4‐X‐benzolsulfonyl)‐amide: Isomorphie und dichte Packung (X = Me, F, Cl, NO2) vs. struktursteuernde Halogenbrücken C–X···Au/O (X = Br, I)

Abstract: Polysulfonylamines. CLXXXIV. Crystal Structures of Molecular Triphenylphosphanegold(I) Di(4-X-benzenesulfonyl)amides: Isomorphism and Close Packing (X = Me, F, Cl, NO2) vs. Structure-Determining C–X···Au/O Halogen Bonds (X = Br, I) In order to study the structure-determining influence that halogen bonding can exert during the course of crystallization, solid-state structures are compared for two previously reported and four new molecular gold(I) complexes of the type Ph3P–Au–N(SO2–C6H4–4-X)2, each featuring linear P,N coordination at gold and two phenyl rings with varying p-substituents X = Me, F, Cl, NO2, Br or I. The compounds were synthesized by reactions of Ph3PAuX (X = Cl or I) with the corresponding silver di(arenesulfonyl)amides, crystallized from dichloromethane, and characterized by low-temperature X-ray diffraction. The Me, F, Cl and NO2 congeners are isomorphic and crystallize without solvent inclusion in the chiral orthorhombic space group P212121 (Z′ = 1). These structures are governed by isotropic close packing via three-dimensional 21 symmetry, incidentally supported by an invariant set of C–H···O=S hydrogen bonds, CH/π interactions and π/π stackings of aromatic rings; in particular, the hard halogen atoms of the fluoro and the chloro homologues are not involved in X···Au, X···O or X···X interactions. The higher homologues, with soft halogen atoms, were obtained as a dichloromethane hemisolvate for X = Br and a corresponding monosolvate for X = I, each triclinic in the centrosymmetric space group (Z′ = 1). Here, the primary structural effect is implemented by infinite chains in which translation-related molecules are connected for the bromo compound by a bifurcated Au···Br(2)···O=S interaction, for the iodo congener by an equivalent Au···I(2)···O=S interaction and a short halogen bond C–I(1)···O=S. The latter bond is stronger than a similar C–Br···O=S interaction and induces a conformational adjustment of the (CSO2)2N group from the normal twofold symmetry in the bromo compound to an energetically unfavourable asymmetric form in the iodo homologue. In both cases, pairs of antiparallel molecular catemers are associated into strands via sixfold phenyl embraces, the strands are stacked to form layers, the solvent molecules are intercalated between adjacent layers, and the crystal packings are reinforced by a number of C–H···O=S hydrogen bonds and interactions of aromatic rings.