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Two new coordination polymers [Cu(btzx)2(MeOH)2](NO3)2 (1) and [Cu(btrcy)2(H2O)2](ClO4)2·btrcy (2) have been synthesized by reacting two bis-triazole/tetrazole-ligands namely m-xylylene-bis(tetrazole) (btzx) and bis(1,2,4-triazole)-trans-cyclohexane (btrcy) with Cu(NO3)2 and Cu(ClO4)2 respectively in a 1:3 metal/ligand ratio. These compounds are shown to form X-ray quality single-crystals under different conditions, and the crystal structures have been determined by single-crystal X-ray diffraction (SXRD). The SXRD data analysis revealed that 1 and 2 are 1D looped chain and 2D-square grid coordination polymers, respectively. More interestingly, the 2D-square grid architecture in 2 acts as an excellent host for the large guest ligand molecule btrcy, which is encapsulated within the voids of the 2D coordination polymer., info:eu-repo/semantics/published

A series of 2,5-bis(arylethynyl)rhodacyclopentadienes has been prepared by a rare example of regiospecific reductive coupling of 1,4-(p-R-phenyl)-1,3-butadiynes (R[DOUBLE BOND]H, Me, OMe, SMe, NMe2, CF3, CO2Me, CN, NO2, −C[TRIPLE BOND]C-(p-C6H4[BOND]NHex2), −C[TRIPLE BOND]C[BOND](p-C6H4[BOND]CO2Oct)) at [RhX(PMe3)4] (1) (X=−C[TRIPLE BOND]C[BOND]SiMe3 (a), −C[TRIPLE BOND]C-(p-C6H4[BOND]NMe2) (b), −C[TRIPLE BOND]C[BOND]C[TRIPLE BOND]C[BOND](p-C6H4[BOND]NPh2) (c) or [BOND]C[TRIPLE BOND]C[BOND]{p-C6H4-C[TRIPLE BOND]C[BOND](p-C6H4-N(C6H13)2)} (d) or Me (e)), giving the 2,5-bis(arylethynyl) isomer exclusively. The rhodacyclopentadienes bearing a methyl ligand in the equatorial plane (compound 1 e) have been converted into their chloro analogues by reaction with HCl etherate. The rhodacycles thus obtained are stable to air and moisture in the solid state and the acceptor-substituted compounds are even stable to air and moisture in solution. The photophysical properties of the rhodacyclopentadienes are highly unusual in that they exhibit, exclusively, fluorescence between 500–800 nm from the S1 state, with quantum yields of Φ=0.01–0.18 and short lifetimes (τ=0.45–8.20 ns). The triplet state formation (ΦISC=0.57 for 2 a) is exceptionally slow, occurring on the nanosecond timescale. This is unexpected, because the Rh atom should normally facilitate intersystem crossing within femto- to picoseconds, leading to phosphorescence from the T1 state. This work therefore highlights that in some transition-metal complexes, the heavy atom can play a more subtle role in controlling the photophysical behavior than is commonly appreciated.

A series of novel, low-valent germanium compounds 2a–2j based on four diethylenetriamines 1a–1d, (methyl)bis(pyrrol-2-ylmethyl)amine (1e), N,N′-(sulfanediyldibenzene-2,1-diyl)bis(pentafluoroaniline) (1f), N,N′-(oxydibenzene-2,1-diyl)bis(pentafluoroaniline) (1g), and (pentafluorophenyl)amines 1i and 1j have been obtained either by the reaction of Ge[N(SiMe3)2]2 with various diamines (1a–1e) or by the metathesis reaction of [GeCl2·dioxane] with lithium amides. The oxidative insertion (with halogenation reagents, MeI, disulfides), [1+4] cycloaddition, and oxidation reactions of the synthesized germylenes were investigated. The compositions and structures of the novel compounds were established by elemental analysis, 1H and 13C NMR spectroscopy, and X-ray diffraction analysis (germylenes 2b, 2i, 2j, Ge4+ compounds 5b, 7a, 7b, 8, 10, 11). All the synthesized germylenes are monomeric.

Upon cooling the monohydrate of the anti-inflammatory drug piroxicam shows reversible splitting (see picture). The cell also shows an irregular contraction over temperature and has a memory effect of its thermal history. This is due to strongly hydrogen bonded chains present in the monohydrate, which allow the crystal domains to contract separately from each other.

An efficient synthetic route to 2- and 2,7-substituted pyrenes is described. The regiospecific direct C-H borylation of pyrene with an iridium-based catalyst, prepared in situ by the reaction of [{Ir(μ-OMe)cod}(2)] (cod = 1,5-cyclooctadiene) with 4,4'-di-tert-butyl-2,2'-bipyridine, gives 2,7-bis(Bpin)pyrene (1) and 2-(Bpin)pyrene (2, pin = OCMe(2)CMe(2)O). From 1, by simple derivatization strategies, we synthesized 2,7-bis(R)-pyrenes with R = BF(3)K (3), Br (4), OH (5), B(OH)(2) (6), and OTf (7). Using these nominally nucleophilic and electrophilic derivatives as coupling partners in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions, we obtained 2,7-bis(R)-pyrenes with R = (4-CO(2)C(8)H(17))C(6)H(4) (8), Ph (9), C≡CPh (10), C≡C[{4-B(Mes)(2)}C(6)H(4)] (11), C≡CTMS (12), C≡C[(4-NMe(2))C(6)H(4)] (14), C≡CH (15), N(Ph)[(4-OMe)C(6)H(4)] (16), and R = OTf, R' = C≡CTMS (13). Lithiation of 4, followed by reaction with CO(2), yielded pyrene-2,7-dicarboxylic acid (17), whilst borylation of 2-tBu-pyrene gave 2-tBu-7-Bpin-pyrene (18) selectively. By similar routes (including Negishi cross-coupling reactions), monosubstituted 2-R-pyrenes with R = BF(3)K (19), Br (20), OH (21), B(OH)(2) (22), [4-B(Mes)(2)]C(6)H(4) (23), B(Mes)(2) (24), OTf (25), C≡CPh (26), C≡CTMS (27), (4-CO(2)Me)C(6)H(4) (28), C≡CH (29), C(3)H(6)CO(2)Me (30), OC(3)H(6)CO(2)Me (31), C(3)H(6)CO(2)H (32), OC(3)H(6)CO(2)H (33), and O(CH(2))(12)Br (34) were obtained from 2. These derivatives are of synthetic and photophysical interest because they contain donor, acceptor, and conjugated substituents. The crystal structures of compounds 4, 5, 7, 12, 18, 19, 21, 23, 26, and 28-31 have also been obtained from single-crystal X-ray diffraction data, revealing a diversity of packing modes, which are described in the Supporting Information. A detailed discussion of the structures of 1 and 2, their polymorphs, solvates, and co-crystals is reported separately.

Tetrasodium p-sulfonatocalix[4]arene exists as a hydrate with approximately 14 water molecules and has three polymorphic modifications, all of which contain a water molecule in the molecular cavity that is engaged in OH···π interactions. Single-crystal neutron structures are reported for two of these three forms and reveal a "compressed" water molecule with short OH bonds. Partial atomic charges and hardness analysis (PACHA) calculations based on the neutron coordinates give an OH···π interaction energy of 6.9-7.5 kJ mol(-1). The PACHA analysis also reveals the dominance of the charge-assisted hydrogen bonds from the Na(+)-coordinated water molecules. The instability of the crystal towards dehydration can be traced to an uncoordinated lattice water site. The remarkable calixarene-Na(+)-hydrate motif is conserved almost unchanged across all three polymorphs. A single-crystal neutron structure is also reported for pentasodium p-sulfonatocalix[4]arene·12H(2)O, which exhibits an intracavity water molecule that is engaged in both OH···π and OH···O hydrogen bonding. The shorter covalent bond to the hydrogen atom that forms the interaction with the aromatic ring is again apparent.

International audience; Reaction of [PdMe2(tmeda)] with pyridyl-N-di(tert-butyl)phosphinoimine spontaneously affords an unusual bimetallic palladium(I) ligand-based biradical complex, which behaves as a "masked" form of Pd0 in its reactions with neutral ligands and chlorobenzene.

Three styryl dyes of the 4-pyridine series that form syn-head-to-tail dimeric pairs in polycrystalline films were synthesised. NMR and UV/Vis spectroscopic studies showed that this promotes stereospecific [2+2]-autophotocycloaddition (PCA) in the dimeric pairs to give rctt-isomers of cyclobutane derivatives. For the dye with an N-ammoniopropyl substituent, this transformation was accomplished according to the single-crystal-to-single-crystal pattern. In aqueous solutions, the dyes and cucurbit[n]urils (CB[n], n = 7, 8) form complexes with a pseudorotaxane structure. CB[7] tends to form 1:1 complexes, and CB[8] forms 1:1 and 2:1 complexes. The structure of the termolecular complex formed by the betaine of the N-sulfonatopropyl styryl dye and CB[8] was determined by X-ray diffraction. The stability of the complexes was measured by 1 H NMR titration in a D 2 O/[D 3 ]MeCN (10:1) mixture (log K 1:1 ≥ 3.2, log K 2:1 ≥ 2.6). Free dyes and their complexes with CB[7] in water undergo only (E)/(Z) photoisomerisation. Termolecular complexes of all dyes with CB[8] were found to undergo effective stereospecific PCA reactions to give rctt isomers of cyclobutane derivatives. The 1:1 complexes of the obtained cyclobutanes with CB[8] (log K cb = 3.2-4.8) are less stable than those of the starting dyes with the same stoichiometry. Thus, CB[8] can play the role of a photocontrolled molecular assembler, i.e., even in the presence of 5 mol-% of CB[8], complete conversion of styryl dyes into the corresponding cyclobutane derivatives takes place upon irradiation in solution.

Photophysikalische Untersuchungen ergaben fur eine Reihe von Rhodiumkomplexen unerwartet hohe Fluoreszenzquantenausbeuten (Φf bis 69 %, τf≈1–3 ns) und ein unerwartet langsames Intersystem-Crossing. Diese neue Verbindungsklasse hinterfragt das gangige Modell zum Verhalten angeregter elektronischer Zustande und zur Rolle von Schweratomen in Intersystem-Crossing-Prozessen. THF=Tetrahydrofuran, Tol=Toluol.

Syntheses, characterization and crystal structures of four designed host-guest compounds of the compositions [{Cu II L 1 } 2 ⊂(H 3 N(ethylene)NH 3 )](NO 3 ) 2 (1), [{Cu II L 1 } 2 ⊂(H 3 N-(propylene)NH 3 )](NO 3 ) 2 (2), [{Cu II L 1 } 2 ⊂(H 3 N(butylene)-NH 3 )](NO 3 ) 2 (3) and [{Cu II L 2 } 2 ⊂(H 3 N(ethylene)NH 3 )](NO 3 ) 2 (4) are described in this investigation [H 2 L 1 = N,N'-ethylenebis(3-methoxysalicylaldimine); H 2 L 2 = N,N'-ethylenebis(3-ethoxysalicylaldimine); ethylene = (CH 2 ) 2 ; propylene = (CH 2 ) 3 ; butylene = (CH 2 ) 4 ]. Compounds 2 and 3 crystallize in the orthorhombic Pcab and monoclinic C2/c systems, respectively, while the space group of compounds 1 and 4 is triclinic Pi. In all of these four compounds 1-4, the two + NH 3 sites of the [H 3 N(CH 2 ) n NH 3 ] 2+ dication (n = 2-4) behave as guests in the 0 4 compartment of two [Cu II L 1 /L 2 ] moieties through bifurcated N-H···O(phenoxo) and NH···O(methoxy/ethoxy) hydrogen-bonding interactions. Evidently, two mononuclear copper(II) moieties are interlinked by bridging supramolecular synthons, resulting in the formation of a supramolecular dimer in the title compounds. From the extent of displacement of the N atoms of [H 3 N(CH 2 ) n- NH 3 ] 2+ from the least-squares O(phenoxo) 2 O(methoxy/ ethoxy) 2 plane, it is clear that [Cu II L 1 ] is a better host than [Cu II L 2 ] for the diprotonated diamine guests. Comparison of the inclusion of water and diprotonated diamines in [Cu II L 1 / L 2 ] is also described in the present investigation. Interestingly, of the two guest species, water and diprotonated diamines, [Cu II L 2 ] prefers the former and [Cu II L 1 ] prefers the latter.

Refluxing of the red compound [CuIIL1blabla(H2O)] (1) in acetone forms two new species: green [CuIIL1(H2O)] (2) and brown [CuIIL1] (3) [H2L1 = N,N′-ethylenebis(3-ethoxysalicylaldimine)]. Whereas both 1 and 2 are converted into 3 upon heating, 3 is converted back into 1 when exposed to air. The structures of all three compounds were determined crystallographically, from which the interesting hydrate isomerism of 1 and 2 are identified; in 1 a water molecule is encapsulated into the O4 section of the ligand through bifurcated hydrogen bonding, whereas in 2 a water molecule coordinates directly to the metal centre. Despite the metal ion binding to the ligand in the same manner in all three cases, the formation of different mononuclear complexes resulting from the presence or absence of water and its coordination or encapsulation is an interesting observation. Thermogravimetric analyses of compounds 1 and 2 showed that the encapsulated water in the former compound is removed at slightly lower temperature than that of the coordinated water molecule, as expected. Although three crystals 1, 2 and 3 were isolated, the composition of species in solution is probably the same as evidenced by 1H NMR spectroscopy. Therefore, the formation of three crystals and the hydrate isomerism described in this investigation are solid-state phenomena.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

An improved method for the synthesis of formyl derivatives of N-methylbenzoazacrown ethers is proposed. They are prepared in up to 68% yields over fewer steps and with a much shorter time required for the last step. The stability constants of complexes formed by N-methylbenzoazacrown ethers and their structural analogs with alkali metal, alkaline-earth metal and ammonium cations were determined by 1H NMR titration in CD3CN. High stability of complexes of N-methyl derivatives of benzoazacrown ethers is demonstrated, comparable with or even exceeding the stability of benzocrown-ether complexes and markedly exceeding the stability of complexes of phenylazacrown ethers with the same macrocycle size. The structures of azacrown ethers and their complexes with Ba(ClO4)2 were studied by X-ray diffraction. A high degree of pre-organization of N-methylbenzoazacrown ethers toward the formation of complexes with metal and ammonium cations was noted, which is due to the clear-cut pyramidal geometry of the nitrogen atom and the orientation of the lone electron pairs (LEPs) of most heteroatoms towards the centre of the macroheterocycle. Copyright © 2009 John Wiley & Sons, Ltd.

The kinetics of the reductive elimination step of a C(sp(3))-C(sp(2)) Negishi cross-coupling catalyzed by a 1:1 complex 2 of palladium and the phosphine/electron-deficient olefin ligand (E)-3-(2-diphenylphosphanylphenyl)-1-phenyl-propenone (1) was studied. Complex 2 is an exceptionally efficient and highly selective catalyst for Negishi cross-coupling reactions involving primary and secondary alkylzinc reagents bearing beta-hydrogen atoms. Turnover numbers (TONs) as high as 10(5) and turnover frequencies (TOFs) as high as 1000 s(-1) were observed. The reactions occurred rapidly and selectively even at 0 degrees C. The fact that the reaction was first order in [Pd] is consistent with homogeneous catalysis by Pd complexes rather than by Pd nanoparticles (NPs). Through systematic kinetic investigations of the Negishi coupling of ethyl 2-iodobenzoate with alkylzinc chlorides, the rate constants for reductive elimination of [Ar-Pd-C(sp(3))] were determined to be >0.3 s(-1), which is about 4 or 5 orders of magnitude greater than the values previously reported for [Pd(dppbz)] and [Pd(PPh(3))(2)] systems (dppbz = 1,2-bis(diphenylphosphino)benzene). The use of a 2:1 ratio of 1:Pd resulted in reduced catalytic activity and selectivity, presumably because the olefin moiety could no longer assist in the reductive elimination step. Importantly, hydrogenation of the C=C double bond in ligand 1 generated a saturated ligand (1H(2)), which was not only less effective than 1, but also gave rise to substantial amount of ethylbenzoate formed by competing beta-hydride elimination. Thus, the pi-accepting olefin moiety in 1 must enhance reductive elimination rates, and, consequently, inhibit formation of byproducts resulting from beta-hydride elimination.

Six new complexes of tin(IV) halides with phosphorus-containing ligands have been fully characterized by single-crystal X-ray diffraction at low temperature. Three of the compounds, derived from the diphosphanes bis-(diphenylphosphino)methane or bis-(dicyclohexylphosphino)methane, have a novel zwitterionic structure, with five Cl ligands and one unidentate phosphorus-containing ligand on tin, together with a proton on the second phosphorus atom of the potentially bidentate ligand; these are Cl5Sn−P(Ph2)CH2PPh2H+ (1), Cl5Sn−OP(Ph2)CH2-PPh2H+ (2), and Cl5Sn−OP(cy2)CH2Pcy2H+ (3). The other three complexes have a bidentate donor attached to the SnX4 moiety; they comprise Cl4SnOP(Ph2)-(CH2)2PPh2O (4), a derivative of bis-(diphenylphosphino)ethane dioxide, I4SnOP(Ph2)CH2PPh2O (5), a similar derivative of bis-(diphenylphosphino)-methane dioxide, and the very unusual Br4SnAs-(Ph2)(CH2)2PPh2O (6), with coordination to tin by As and O. Since the starting material for the last compound was Ph2As(CH2)2PPh2, this result illustrates well the more facile oxidation of P(III) than As(III). © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:136–143, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20525

Two compounds of a novel-type azagermatrane, N(CH2CH2NC6F5)3Ge-Hal: HalCl (1), Br (2), were prepared via a metathetical reaction of trilithium salt of tetramine, N[CH2CH2N(Li)C6F5]3, with corresponding GeHal4. A single crystal structure of 1 was determined by the X-ray diffraction study: The compound shows the strongest transannular Nax Ge interaction (2.148(7) A) among other studied azagermatranes. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:738–741, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20476

cited By 6; International audience; (Chemical Equation Presented) Three in one: The anellated σ4-1λ5-[1,3,2]diazaphosphole 2 exists in tautomeric equilibrium with isomer 1 (see scheme) and undergoes three completely different types of reaction: trimethyl aluminum binds at the N terminus of the P=N bond with ring retention, the dihydropyridine fragment reacts with an activated acetylene in a pseudo-[2+2] cycloaddition, and P-N bond cleavage is possible with RhI. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

New insights into the mechanism for the transition metal-mediated oxidation of hydroxamic acids to give intermediate acyl nitroso species, with subsequent hetero-Diels-Alder trapping are presented. The activation of triphenylphosphine-ligated ruthenium-salen complexes is examined, and evidence is presented for the ruthenium-oxo species which are involved in the oxidative process of the hydroxamic acid. The observation of the lack of asymmetric induction involved in the intermolecular cycloaddition process involving the intermediate acyl nitrsoso species is explained, with the aid of comparing the ruthenium-salen-based systems with nitrosotoluene, and copper(I)/copper(II) BINAP-based catalysis of nitrosopyridine complexes. This study demonstrates the importance of secondary coordination to achieve asymmetric induction in nitroso-Diels-Alder reactions.

The study of the complex formation of 3,3-diphenyl-3H-benzo[f]chromenes containing aza-18-crown-6-ether, diaza-18-crown-6-ether or morpholine units with alkali, alkaline earth, heavy and transition metal cations in acetonitrile is reported. The spectroscopic and kinetic behavior of the photomerocyanine isomers of these chromenes is strongly affected by complexation with a metal cation. In order to interpret some of experimental data, an ab initio theoretical analysis of photochromic-crown ether and its cation complexes was conducted. The different site of coordination of mono- and divalent cations to determine the minimum-energy structure of benzochromene complexes in gas phase as well as in acetonitrile as solvent was explored. The coordination of both carbonyl oxygen and crown-ether macrocyle with divalent cations in carbonyl-capped structure is found to be the most stable isomer in gas as well as in condensed media. The crown-containing benzochromenes were studied in liquid-liquid extraction experiments toward there capacity to transfer metallic salts from water into an organic phase.The high selectivity to extraction of Ag+ was found. Copyright © 2007 John Wiley & Sons, Ltd.

Pyrido[3,2-b][1,4]oxazine and pyrido[2,3-b][1,4]benzoxazine systems were synthesised by annelation reactions involving highly fluorinated pyridine derivatives and nitrogen and oxygen centred difunctional nucleophiles by sequential regioselective nucleophilic aromatic substitution processes.

(P)-(+)-Hexaspiro[2.0.0.0. 0.0.2.1.1.1.1.1]pentadecane [(P)-17] as well as (M)-(-)- and (P)-(+)-octaspiro[2.0.0.0.0.0.0.0.2.1.1.1.1.1.1.1]nonadecanes [(M)- and (P)-25]-enantiomerically pure unbranched [7]- and [9]triangulanes-have been prepared starting from racemic THP-protected (methylenecyclopropyl)methanol 6. The relative configurations of all important intermediates as well as the absolute configurations of the key intermediates were established by X-ray crystal structure analyses. This new convergent approach to enantiomerically pure linear [n]triangulanes for n=7, 9 was also tested in two variants towards [15]triangulane. Some of the most prominent and unexpected features of the newly prepared compounds are the remarkable modes of self-assembly of the diols (P)-14, (E)-(3S,3'S,4S,4'S,5R,5'R)-21, (P)-(+)-22, and (E)-31 in the solid state through frameworks of intermolecular hydrogen bonds leading to, depending on the respective structure, nanotube- [(P)-14, (P)-(+)-22, and (E)-31], honeycomb-like structures [(E)-(3S,3'S,4S,4'S,5R,5'R)-21] or a supramolecular double helix [(P)-(+)- and (M)-(-)-22]. Liquid crystalline properties of the esters and ethers of the diols (P)-14, (P)-, and (M)-22 have also been tested. Although all of these [n]triangulanes have no chromophore which would lead to significant absorptions above 200 nm, they exhibit surprisingly high specific rotations even at 589 nm with [alpha](20)(D)=+672.9 (c=0.814 in CHCl(3)) for (P)-(+)-17, +909.9 (c=0.96 in CHCl(3)) for (P)-(+)-25, -890.5 (c=1.01 in CHCl(3)) for (M)-(-)-25, and -1302.5 (c=0.36 in CHCl(3)) for (M)-(-)-39, and the specific rotations increase drastically on going to shorter wavelengths. This outstanding rotatory power is in line with their rather rigid helical arrangement of sigma bonds, and accordingly these helically shaped unbranched [n]triangulanes may be termed "sigma-[n]helicenes", as they represent the sigma-bond analogues of the aromatic pi-[n]helicenes. Density functional theory (DFT) computations at the B3 LYP/6-31+G(d,p) level of theory for the geometry optimization and time-dependent DFT for determining optical rotations with a triplet-zeta basis set (B3 LYP/TZVP) reproduce the optical rotatory dispersions (ORD) very well for the lower members (n=4, 5) of the sigma-[n]helicenes. For the higher ones (n=7, 9, 15) the computed specific rotations turn out increasingly larger than the experimental values. The remarkable increase of the specific rotation with an increasing number of three-membered rings is proportional neither to the molecular weight nor to the number of cyclopropane rings in these sigma-[n]helicenes.

Epoxidation of barrelene (3) with a neutralized solution of Oxone® gave the barrelene trisepoxide 6 in 82 % isolated yield, while lead tetraacetate promoted aziridination of 3 with two equiv. of N-aminophthalimide gave a mixture of mono-7 and bis(aziridine) endo,exo-8, which were isolated in 67 and 8 % yield, respectively. Fourfold repetition of this aziridination gave the bis(aziridines) exo,exo- and endo,exo-8 along with the trisaziridine 9 in 21, 8 and 19 % yield, respectively. Epoxidation of 7 and endo,exo-8 with buffered m-chloroperbenzoic acid furnished the dioxaazatrishomobarrelene 10 and oxadiazatrishomobarrelene 11 in 36 and 62 % yield, respectively. The structures of triheteratrishomobarrelenes 6 and 9 were established by X-ray crystallography. Upon treatment with BF3·Et2O at –20 °C (for 6) or with the strongly acidic ion exchange resin Amberlyst 15 at ambient or elevated temperatures (for 9–11), these triheteratrishomobarrelenes rearrange to give the triheteratrishomocubanes rac-12 to rac-15, as proved by X-ray crystal structure analysis of rac-13, in 75–100 % yield. The enantiomeric pairs of trioxa- 12 and triazatrishomocubane 13 were separated by preparative HPLC on a chiral column. 12 exhibited specific rotationsof [α]D25 = +196 and [α]36525 = +652 (c = 0.497, CHCl3) for the firstly eluted and [α]D25 = –173 and [α]36525 = –608 (c = 0.503, CHCl3) for the secondly eluted enantiomer; 13 had [α]D25 = +30 and [α]43525 = +501 (c = 0.490, CHCl3) for the firstly as well as [α]D25 = –28 and [α]43525 = –475 (c = 0.501, CHCl3) for the secondly eluted enantiomer. The geometry of rac-13 and the absolute configurations of (–)-12 and (+)-13 were determined by X-ray crystal structure analyses. According to this, (–)-12 and (+)-13 possess the same (1R,3R,5R,6R,8R,10R)-configuration. Theabsolute configuration of the former was also confirmed byDFT computations at the TD-B3LYP/6-31+G(d,p)//B3LYP/6-31+G(d) level of theory; the computed specific rotation for (–)-12 was –178. Computations for the elusive (all-R)-triazatrishomocubane (all-R)-13-H without phthalimidyl substituents on the nitrogen atoms disclosed that the sign of rotation is the same for the parent (all-R)-13-H and (all-R)-trioxatrishomocubane (all-R)-12 with the same absolute configuration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The novel cationic complex [Ag14(C2tBu)12]2+ has been synthesized by four reactions: reaction of [Ag(C2tBu)]n and AgBF4 in acetone in a 6:1 mole ratio, that of HC≡CtBu and AgBF4 in water in the absence of a base, treatment of [AgC2tBu]n with HBF4 in acetone or that of {[Ag3(C2tBu)2][BF4]}n with [Ag(C2tBu)]n in a 1:4 mole ratio. Single-crystal X-ray studies showed it to be a hexacapped cube of silver(I) atoms, with twelve η1, μ3-C2tBu ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis of the title compounds, viz. [RN(CH 2 CH 2 O)-(CHR 1 CR 2 R 3 O)]Ti(OiPr) 2 (13-15) and [RN(CH 2 CH 2 O)-(CHR 1 CR 2 R 3 O)] 2 Ti (18-28), by the reaction of one or two equivalents of the corresponding dialkanolamines RN(CH 2 CH 2 OH)(CHR 1 CR 2 R 3 OH) (1-12) with Ti(OiPr) 4 is reported. Other routes to [RN(CH 2 CH 2 O)(CHR 1 CR 2 R 3 O)] 2 Ti, such as the reaction of Ti(CH 2 Ph) 4 with dialkanolamine and the reaction of TiCl 4 (THF) 2 with dialkanolamine/Et 3 N were also tested. Dimeric titanocane 16, [PhCH 2 N(CH 2 CH 2 O) 2 Ti-(OMe) 2 ] 2 , was obtained from the reaction of one equivalent of dialkanolamine 3 with CpTi(OMe) 3 , PhCH 2 N(CH 2 CH 2 O) 2 -Ti(OMenth) 2 (17) was prepared from the transalkoxylation reaction of 15 with two equivalents of menthol. The composition and structures of all novel compounds were established by 1 H and 13 C NMR spectroscopy as well as elemental analysis data. The possible solution structure features of 13-28 are discussed. The single-crystal X-ray diffraction study of titanocane 16 clearly indicates a dimeric structure for this compound in the solid state. According to X-ray data, compounds [PhCH2N(CH2CH20)2]2Ti (19), [MeN(CH 2 CH 2 O)-(CH 2 CHPhO)] 2 Ti (20), [MeN(CH 2 CH 2 O)(CH 2 CPh 2 O)] 2 Ti (23), erythro-[MeN(CH 2 CH 2 O)(CHPhCHPhO)]2Ti (24), threo-[MeN(CH 2 CH 2 O)(CHPhCHPhO)]2Ti (25), and {MeN(CH 2 -CH 2 O)[CH(CH 2 ) 4 CHO]} 2 Ti (27) possess a monomeric structure with a hexacoordinate titanium atom in the solid state. Among them complexes 19, 20, 23, 25, and 27 are characterized by a cis disposition of the nitrogen atoms in the coordination environment of the Ti atom, while nitrogen atoms in 24 occupy trans positions.

Rate constants are reported for reaction of 4-substituted 1-chloro-2,6-dinitrobenzenes 1, 6-substituted 1-chloro-2,4-dinitrobenzenes 2, and some of the corresponding 1-phenoxy derivatives, 3 and 4, with n-butylamine, pyrrolidine and piperidine in acetonitrile as solvent. Values of k1, the rate constant for nucleophilic attack at the 1-position, increase with increasing ring-activation but may be reduced by steric repulsion at the reaction centre which increases in the order Cl pyrrolidine > piperidine.

A novel class of charge-transfer complexes based on iodine chloride and substituted pyridines, which possess a number of interesting and unique structural features, can be employed to bring about a stereocontrolled chloro-deboronation of certain vinyl boronates to generate the (1Z)-alkenyl chlorides in good yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The acceptor capabilities of "organic" halogen, CX (X=F, Cl, Br, I), with respect to hydrogen bonding are controversial, and unactivated organic chlorine is generally deemed to be a poor acceptor. Hydrogen bridges of the type O--H...Cl--C are uncommon and occur mainly in an intramolecular situation when the donor group is sterically hindered, so that the formation of intermolecular interactions is difficult. In this paper, intramolecular O--H...Cl--C interactions in a series of chloro-substituted gem-alkynols are studied. We describe various features of this interaction using crystallographic, spectroscopic and computational methods. The O--H...Cl--C interaction occurs in five of the six compounds under consideration here (CDDA, 14DDDA, 15DDDA, 18DDDA, 15MKA). Solution (1)H NMR spectroscopy shows that the interaction is intramolecular and that it is a true hydrogen bond. DFT calculations give a stabilisation energy around 4.0 kcal mol(-1). In the crystal structures of the compounds studied, the intramolecular O--H...Cl--C interactions fit into the overall scheme of cooperative interactions. These structures may be derived from that of the unsubstituted compound DDA by means of synthon exchange and the O--H...Cl--C interaction fares surprisingly well in the presence of competing stronger acceptors. The crystal structures show an unusual degree of modularity for compounds that generally form interactions that are weak and variable. It is noteworthy that the so-called "weak" acceptor, organic chlorine, is able to sustain a good intramolecular hydrogen bridge that is of an attractive and stabilizing nature and which is of potential importance in crystal engineering and supramolecular chemistry.

Niobocene trihydride reacts directly with the chlorosilanes SiCl2R′R′′ (R′, R′′ = Me, Ph) and SiCl3Me to give the dihydridomonosilyl derivatives [Cp2Nb(H)2(SiClnR3−n)] (n = 1, 2), whereas the analogous reaction with SiCl4 affords [Cp2Nb(H)2(SiCl3)] and the bis(silyl) complex [Cp2NbH(SiCl3)2], whose X-ray structure was determined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Additions of ethyl or tert-butyl diazoacetates to 4-substituted cyclopentenes 6 and 17 under dirhodium tetraacetate/tetraoctanoate catalysis led to mixtures of tert-butyl endo,exo- and exo,exo-3-carboxyl(aryl)bicyclo[3.1.0]hexane-6-carboxylates 7 and 18 in yields of 54−90% from which exo,exo-diastereomers were isolated in yields of 39−63%. Diester exo,exo-7 was saponified and converted into diaryl diesters exo,exo-9a,b in overall yields of 42 and 46%, respectively. The esters exo,exo-18 were reduced to the corresponding hydroxymethyl derivatives, these were transformed to the iodomethyl compounds which in turn were coupled with various alkylmagnesium halides, via Li2CuCl4 catalysis, to give 3-aryl-6-alkylbicyclo[3.1.0]hexyl derivatives exo,exo-21 in overall yields of 72−83%. Fluorinated 3-(2-arylethyl)-6-pentylbicyclo[3.1.0]hexane exo,exo-32 could be prepared in five steps from 4-ethoxy-2,3-difluorobenzaldehyde 26a adopting essentially the same synthetic strategy, but in an overall yield of only 8%, and 6-(4-cyanophenyl)-3-pentylbicyclo[3.1.0]hexane exo,exo-38b was obtained by Pd(OAc)2 catalyzed cyclopropanation of 4-pentylcyclopentene 34b with (4-cyanophenyl)diazomethane 36b in 29% yield. A comparison of the liquid crystalline properties of these newly prepared compounds containing a bicyclo[3.1.0]hexane core with those of the known analogous compounds with a cyclohexane fragment shows that as a rule, a bicyclo[3.1.0]hexane moiety decreases the transition temperature, while the dielectric (Δϵ) and optical (Δn) anisotropies are comparable. However, the bicyclo[3.1.0]hexane unit has a poorer mesogenic potential. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Kinetic studies are reported for the reactions with aniline in acetonitrile of a series of X-phenyl 2,4,6-trinitrophenyl ethers [X=H, 2-, 3-, 4-CH3, 2,4-, 2,6-(CH3)2, 2-, 3-, 4-NO2, 2,4-, 2,6-(NO2)2]. X-ray crystal structures for X=H, 2,6-(CH3)2 and 2,6-(NO2)2 are reported and provide evidence for steric crowding around the 1-position of these molecules. Nevertheless, the kinetic data show that increasing substitution does not sterically inhibit nucleophilic attack by aniline and an ‘early’ transition state is likely. In general, the reactions are base catalysed; interpreted as rate-limiting deprotonation of the zwitterionic intermediates. Only with the dinitro derivatives is an uncatalysed reaction involving intramolecular proton transfer observed and when X=2,6-(NO2)2 this pathway takes all the reaction flux. Copyright © 2003 John Wiley & Sons, Ltd. Additional material for this paper is available in Wiley Intersciene

Reactions of element-substituted alkynes R3MCCPh (R3M = Me3Si, Et3Si, Ph3Si, Et3Ge, n-Bu3Sn, N(CH2CH2O)3Si, N(CH2CH2O)3Ge, N(CH2-CHMeO)3Ge, and N(CH2CH2O)2(CH2CHPhO)Ge) with bromine, tetra-n-butylammonium tribromide (TBAT), and N-bromosuccinimide (NBS)/DMSO were investigated. The Z,E-ratio of isomeric dibromoalkenes formed in bromination reaction with Br2 and TBAT are discussed. The crystal structures of N(CH2CH2O)3SiCCPh and N(CH2CHMeO)3GeX (X = C CPh, C(Br)C(Br)Ph, C(Br2)C(O)Ph), and Ph3SiC(Br)C(Br)Ph are reported. © 2003 Wiley Periodicals, Inc. 15:43–56, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10211

A series of promising benzoazacrown ethers with the nitrogen atom conjugated with the benzene ring were synthesized using a novel synthetic procedure based on stepwise transformation of the macroheterocycle. The structures and spectral properties of the resulting benzoazacrown ethers and their complexes with Ca2+ were studied by X-ray diffraction and 1H, 13C, and 15N NMR spectroscopy including the 2D NOESY technique. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The compound trans-1,5-dichloro-9,10-diethynyl-9,10-dihydroanthracene-9,10-diol (DDDA) has an inversion center as the only molecular symmetry element and yet does not occupy an inversion center in the centrosymmetric space group that it adopts in the crystal structure. The reason for this very unusual occurrence is the crowded environment of the H-bond donors and acceptors that leads to less than optimal H-bonding. A centrosymmetric supramolecular synthon constituted with four Cl-atoms in a planar array occupies an i site in the crystal, and this appears to provide a satisfactory alternative packing. Based on the hypothesis that H-bonding is less than optimal in the crystal structure of DDDA, pseudopolymorphs were prepared with strongly H-bond-accepting solvents. The crystal structures of five of these solvates are described, wherein the DDDA molecule is able to occupy an i site and form strong and linear OH ⋅⋅⋅O H-bonds with the solvent molecules. Competition experiments show that a smaller solvent molecule with a greater H-bond-accepting ability is included more readily and that the H-bonds formed are correspondingly better.

Symmetry-modified principal-component analysis has been used to visualise the geometrical distortions of three-coordinate metal centres observed in crystal structures retrieved from the Cambridge Structural Database. It is shown that compounds of Cu, Ag, Hg, Zn, and Au dominate the dataset, and exhibit distortions away from the trigonal planar archetype towards a) T-shaped and b) Y-shaped geometries. A small number of compounds, principally of Cu and Ag, also show distortions towards trigonal pyramidal geometries. The interconversions from Y-shaped geometries, through the trigonal planar form to T-shaped geometries are clearly mapped by the PC analysis. For HgII complexes, it is possible to interpret the transition from T-shaped geometries to the trigonal planar form in terms of a reaction pathway for ligand addition to linear L1HgIIL2 species.

All four diastereomers of 3-(trans-2-nitrocyclopropyl)alanine (3) were prepared by asymmetrically induced α-C alkylation of the glycine moiety in the [(S)- or (R)-Schiff base]NiII complex 7, employing racemic trans-1-(iodomethyl)-2-nitrocyclopropane (8) as the alkylating agent. A notable difference in solubility between the two diastereomeric products 9a/9b [when (S)-7 was used as starting material] or 9d/9e [when (R)-7 was employed] allowed for their separation from the same reaction mixture. All the diastereomers of 3-(trans-2-nitrocyclopropyl)alanine (3) were produced upon brief exposure of the alkylation products 9 to dilute hydrochloric acid, with subsequent purification by ion-exchange chromatography and crystallization. The absolute configurations of the nickel complexes 9a−e were established by X-ray crystallographic analyses. In addition, the X-ray crystal structure of (2S,1′S,2′R)-3 was determined to confirm the convergence of the configurations of the parent nickel complexes 9 with those of the amino acids 3 derived from them. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

The synthesis and crystal and molecular structure are described of (C 2 B 10 H 11 )C 6 H 4 (C 2 B 10 H 10 )C 6 H 4 (C 2 B 10 H 11 ) (4), an acyclic assembly of three ortho-carborane units connected through their carbon atoms by two para-phenylene units. For this compound, and published structures of other aryl-ortho-carboranes, correlations are noted between the orientations of aryl substituents and cage carbon-carbon distances (C1-C2). Ab initio RHF/6-31G* and MP2/6-31G* studies on 1-phenyl-ortho-carborane, PhC 2 B 10 H 11 , and other model systems have been used to explore the variations in their energies, C1-C2 bond lengths, and C2-C1-C aryl bond angles with the orientation of their aryl groups, variations believed to reflect weak interactions between the aryl substituents' π systems and the carborane cages. The synthesis of a pentafluorophenyl derivative of 4, (C 2 B 10 H 11 )C 6 H 4 (C 2 B 10 H 10 )C 6 H 4 (C 2 B 10 H 10 )C 6 F 5 , is also described.

(M)-(-)- and (P)-(+)-Trispiro[2.0.0.2.1.1]nonanes [(M)- and (P)-3] as well as (M)-(-)- and (P)-(+)-tetraspiro[2.0.0.0.2.1.1.1]undecanes [(M)- and (P)-4]-enantiomerically pure unbranched [4]- and [5]triangulanes-have been prepared starting from racemic bicyclopropylidenecarboxylic [(1RS)-12] and exo-dispiro[2.0.2.1]heptane-1-carboxylic [(1RS,3SR)-13] acids. The optical resolutions of rac-12 and rac-13 furnished enantiomerically pure acids (S)-(+)-12, (R)-(-)-12, (1R,3S)-(-)-13, and (1S,3R)-(+)-13. The ethyl ester (R)-25 of the acid (R)-(-)-12 was cyclopropanated to give carboxylates (1R,3R)-26 and (1R,3S)-26. The ester (1R,3S)-26 and acids (1R,3S)-13 and (1S,3R)-13 were converted into enantiomerically pure methylene[3]triangulanes (S)-(-)- and (R)-(+)-28. An alternative approach consisted of an enzymatic deracemization of endo-[(1SR,3SR)-dispiro[2.0.2.1]heptyl]methanol (rac-20) or anti-[(1SR,3RS)-4-methylenespiropentyl]methanol (rac-18). This afforded (S)-(-)- and (R)-(+)-28 (starting from rac-20), as well as enantiomerically pure (M)-(-)- and (P)-(+)-1,4-dimethylenespiropentanes [(M)- and (P)-23] starting from rac-18. The methylenetriangulanes (S)-(-)- and (R)-(+)-28 were cyclopropanated furnishing (M)- and (P)-3. The rhodium-catalyzed cycloaddition of ethyl diazoacetate onto (S)-(-)- and (R)-(+)-28 yielded four diastereomeric ethyl trispiro[2.0.0.2.1.1]nonane-1-carboxylates in approximately equal proportions. The enantiomerically pure esters (1R,3S,4S)- and (1S,3R,4R)-30 were isolated by careful distillation and then transformed into [5]triangulanes (M)- and (P)-4 using the same sequence of reactions as applied for (M)- and (P)-3. The structures of the key intermediates (R)-12 and rac-31 were confirmed by X-ray analyses. Although [4]- and [5]triangulanes have no chromophore which would lead to any significant absorption above 200 nm, they have remarkably high specific rotations even at 589 nm with [alpha](20)D=-192.7 [(M)-3, c=1.18, CHCl(3))] or +373.0 [(P)-4, c=1.18, CHCl(3))]. This remarkable optical rotatation is in line with their helical arrangement of sigma bonds, as confirmed by a full valence space single excitation configuration interaction treatment (SCI) in conjunction with DFT computations at the B3LYP/TZVP//B3LYP/6-31+G(d,p) level of theory which reproduce the ORD very well. Thus, it is appropriate to call the helically shaped unbranched [n]triangulanes the "sigma-[n]helicenes", representing the sigma-bond analogues of the aromatic [n]helicenes.

Butadienyl dyes of the benzothiazole series with various fragments of benzocrown ethers 1a-c were synthesized for the first time. The structures and spectral properties of crown-containing butadien ...