An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Calculations of molecular structures in the electronic ground state S(0) and of excited state and fluorescence energies generally refer to the gas phase. This complicates a comparison with experimental data, which often are only available for molecules in solution. Therefore, experimental absorption and fluorescence spectra in the vapor phase are presented for 1-tert-butyl-6-cyano-1,2,3,4-tetrahydroquinoline (NTC6), 1-methyl-6-cyano-1,2,3,4-tetrahydroquinoline (NMC6), 4-(dimethylamino)benzonitrile (DMABN), and 4-(diisopropylamino)benzonitrile (DIABN). NTC6 and DIABN show a dual fluorescence in the gas phase, with emissions from an intramolecular charge transfer (ICT) and a locally excited (LE) state, whereas with NMC6 and DMABN only LE emission is observed. For a comparison of the experimental molecular structure in S(0) with the results of recent computations, X-ray crystal structures of NTC6, NMC6, and several analogues are presented. For DMABN, NMC6, and NTC6, LE/ICT energy diagrams are constructed, in which the experimental energies of the Franck-Condon singlet excited states S(1) and S(2), and the LE and ICT states together with their emissions, are compared with the calculations. The LE and ICT dipole moments are also discussed. This comparison reveals substantial differences, in particular for the ICT energies, but even for the structure of the S(0) ground states. It is concluded that the computed ICT states of NTC6 and DMABN, in which the full conjugation of the phenyl ring is interrupted, is different from the ICT states measured in the experiments.

New approaches to the protoilludane sesquiterpenes (±)-cerapicol and (±)-sterpurene via rearrangement routes are described. The absolute configuration of (+)-cerapicol has been determined and found in accord with a biosynthesis of the natural product via cyclization of humulene to the so-called protoilludyl cation and a subsequent 1,2-alkyl shift.

WOCl4 reacts with (Me3Si)2O and excess THF to give [WO2Cl2(THF)]4 (1), a new tetrameric tungsten(VI)-oxo complex, which was characterized and crystal structure was determined by X-ray crystallography. Complex 1 has a roughly square planar tetranuclear structure bridged by μ-oxo ligands. Each tungsten atom is coordinated by two bridging oxygens, one terminal oxygen, two “axial” chlorine atoms and one “equatorial” O-bonded THF ligand. One of the two μ-oxo ligands is similar to the terminal oxygen atom and the other one is similar to the coordinated oxygen atom of the THF ligand, respectively, which confirmed a previous proposal. Four WO3Cl2(THF) octahedral are associated by sharing corners. Complex 1 is different from three known tetrameric tungsten analogues in its structural arrangement and properties.

Synthetic routes leading to two series of (eta(8)-cyclooctatetraenyl)lanthanide(III) scorpionate "mixed sandwich" complexes are reported. The early lanthanide derivatives (COT)Ln(Tp) (Ln = Ce (1), Pr (2), Nd (3), Sm (4)) and (COT)Ln(Tp(Me2)) (Ln = Ce (5), Pr (6), Nd (7), Sm (8)) (COT = eta(8)-cyclooctatetraenyl, Tp = hydrotris(pyrazolyl)borate, Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate) were obtained by reacting the dimeric halide precursors [(COT)Ln(mu-Cl)(THF)]2 with K[Tp] or K[Tp(Me2)], respectively For the late lanthanide elements a different synthetic route was developed. The complexes (COT)Ln(Tp) (Ln = Er (9), Lu (10)) were made by the reaction of (Tp)LnCl2(THF)1.5 with equivalent amounts of K2C8H8. All new compounds were isolated as intensely colored crystalline materials and fully characterized by elemental analyses and spectroscopic methods. The molecular structures of 4, 5, and 8 were elucidated by X-ray diffraction. The optical spectra of compounds 2 and 4-8 were run at room and low temperatures. From the spectra obtained, the underlying crystal field splitting patterns of complexes 2, 4, 6, and 7 were derived and simulated by fitting the free parameters of a phenomenological Hamiltonian. The parameters used allow the estimation of the crystal field strengths experienced by the Ln3+ central ions and the insertion of complexes 2, 4, 6, and 7 into empiric nephelauxetic and relativistic nephelauxetic series. Besides, the experimentally oriented non-relativistic and relativistic molecular orbital schemes of compound 6 were set up and compared with the results of previous model calculations on [Ln(COT)2]-, Pa(COT)2, and U(COT)2.

The acid catalyzed rearrangement of two cyclohexanols of spiroannelated four-membered rings has been studied. In accordance with molecular mechanics calculations, far-reaching reorganizations with formation of unsaturated hexacyclic systems, including a fully cycloalkylated cyclohexene with a bispropellane partial structure, were observed. Attempts to convert this bispropellane to a trispropellane failed.

The fluorescence spectra of 2,4,6-tricyano-N,N-dimethylaniline (TCDMA), 2,4,6-tricyano-N-methylaniline (TCMA), and 2,4,6-tricyanoaniline (TCA) consist of a single emission band, even in the polar solvent acetonitrile (MeCN). This indicates that an intramolecular charge transfer (ICT) reaction from the initially prepared locally excited (LE) state does not take place with these molecules, in contrast to 4-(dimethylamino)benzonitrile (DMABN), although the electron accepting capability of the tricyanobenzene moiety in TCDMA, TCMA, and TCA is substantially larger than that of the benzonitrile group in DMABN. In support of this conclusion, the picosecond fluorescence decays of the tricyanoanilines are single-exponential. Only with TCDMA in MeCN at the highest time resolution, double-exponential decays are observed. On the basis of a similar temporal evolution of around 2 ps in the femtosecond excited-state absorption (ESA) spectra of TCDMA in this solvent, the time development is attributed to the presence of two rapidly interconverting S(1) conformers. The same conclusion is reached from CASPT2/CASSCF computations on TCDMA, in which two S(1) minima are identified. The ESA spectra of TCDMA, TCMA, and TCA resemble that of the LE state of DMABN, but are different from its ICT ESA spectrum, likewise showing that an ICT reaction does not occur with the tricyanoanilines. From the luminescence spectrum of TCDMA in n-propyl cyanide at -160 degrees C, it follows that intersystem crossing and not internal conversion is the main S(1) deactivation channel. The radiative rate constant of TCDMA in MeCN is smaller than that of TCMA and TCA, which indicates that the S(1) state of TCDMA has a larger ICT contribution than in the case of TCMA and TCA, in accordance with the results of the calculations, which show that the S(1) state displays ICT valence bond character. Extrapolated gas-phase data for TCDMA and TCA are compared with the results of the computations, revealing a good agreement. The calculations on TCDMA and TCA also lead to the conclusion that the lowest excited singlet state S(1) determines its photophysical behavior, without the occurrence of an LE --> ICT reaction, in the sense that the initially excited LE state has already a strong ICT character and there is no equilibrium between two electronic states with strongly different electronic structures (i.e., LE and ICT with very different dipole moments) leading to dual (LE + ICT) fluorescence.

The fluorescence spectrum of the rigidified 4-cyanofluorazene (FPP4C) in n-hexane consists of a dual emission from a locally excited (LE) and an intramolecular charge-transfer (ICT) state, with an ICT/LE fluorescence quantum yield ratio of Phi'(ICT)/Phi(LE) = 3.3 at 25 degrees C. With the flexible 4-cyano- N-phenylpyrrole (PP4C) in n-hexane, such an ICT reaction also takes place, with Phi'(ICT)/Phi(LE) = 1.5, indicating that for this reaction, a perpendicular twist of the pyrrole and benzonitrile moieties is not required. The ICT emission band of FPP4C and PP4C in n-hexane has vibrational structure, but a structureless band is observed in all other solvents more polar than the alkanes. The enthalpy difference Delta H of the LE --> ICT reaction in n-hexane, -11 kJ/mol for FPP4C and -7 kJ/mol for PP4C, is determined by analyzing the temperature dependence of Phi'(ICT)/Phi(LE). Using these data, the energy E(FC,ICT) of the Franck-Condon ground state populated by the ICT emission is calculated, 41 (FPP4C) and 40 kJ/mol (PP4C). These large values for E(FC,ICT) lead to the conclusion that with FPP4C and PP4C, direct ICT excitation, bypassing LE, does not take place. FPP4C has an ICT dipole moment of 15 D, similar to that of PP4C (16 D). Picosecond fluorescence decays allow the determination of the ICT lifetime, from which the radiative rate constant k'(f)(ICT) is derived, with comparable values for FPP4C and PP4C. This shows that an argument for a twisted ICT state of PP4C cannot come from k'(f)(ICT). After correction for the solvent refractive index and the energy of the emission maximum nu(max)(ICT), it appears that k'(f)(ICT) is solvent-polarity-independent. Femtosecond transient absorption with FPP4C and PP4C in n-hexane reveals that the ICT state is already nearly fully present at 100 fs after excitation, in rapid equilibrium with LE. In MeCN, the ICT state of FPP4C and PP4C is likewise largely developed at this delay time, and the reaction is limited by dielectric solvent relaxation, which shows that the ICT reaction is ultrafast, at the experimental time limit of 50 fs. PP4C and FPP4C have a similar planar ICT structure, without an appreciable twist of the pyrrole and benzonitrile subgroups. Their crystal structure is compared with calculations for the S0 ground state.

Water molecules in association with chloride anions form supramolecular self-assembled tapes made of fused five- and six-membered rings, [(H2O)3Cl(OH)] and [(H2O)4Cl(OH)], serving as a template in the crystal structure of dinuclear {[Cu(dien)(μ-OH)]+Cl−}2 · 3H2O, based upon a Cu2(μ-OH)2 central moiety.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

5,5-Dimethylcyclohexane-1,3-dione (dimedone) and cyclohexane-1,3-dione react with Cl2Si(CMe3)(2) in the presence of triethylamine to give the bis(1-cyclohexene-3-on-l-oxy)di(t) butyl-silanes 2 and 3. Using dimedone and Cl2SiMe2, the analogous dimethylsilane 1 is obtained. A 1,4-Michael-Addition occurs using cyclohexane-1,3-dione in the reaction with Cl2SiMe2 to give a spirocyclic diketone (4). The reaction of cyclohexane-1,3-dione with lithium-diisopropylamide and F3SiCMe3 leads to the formation of a salt [(Pr2NH2)-Pr-i](2)HF[C6H7O2](2), 5. The crystal structures of 2-5 were determined.

A three-component domino Heck-Diels-Alder reaction involving pinacol bicyclopropylideneboronate (8b), iodobenzene (9) and methyl acrylate (12) under Jeffery conditions [Pd(OAc)(2), PPh3, K2CO3, Et4NCl, MeCN] produced a mixture of phenylspiro[2.5]octeneboronates syn/anti-(E)-14b and methyl phenylspirooctenecarboxylate 25 in 25 and 38 % yield, respectively. The major product 25 was most probably formed via the homoallylpalladium complex 23b undergoing deboropalladation rather than dehydropalladation. Similarly, reactions of tributylstannyl- and hydroxydimethylsilyl-substituted bicyclopropylidenes 8c-d with 9 and tert-butyl acrylate gave the tert-butyl phenylspirooctenecarboxylate 26 via the diene 24 formed by demetallopalladation processes. The reaction of methyl 1,1'-bicyclopropylidene-2-carboxylate (8e) with iodobenzene (9) in the presence of tert-butyl acrylate (13) furnished a mixture of regimsomeric and diastereomeric spirooctenes syn/anti-(E)-15e and syn/anti-(Z)-15e in 69 and 6 % yield, respectively. The structures of the major pair of diastereomers syn-(E)-15e and anti-(E)-15e were rigorously proved by X-ray crystal structure analyses.

The first crystallographically characterized molybdenum(VI) selenoether complex [Mo2O4(OC3H6SeC3H6O)(2)] and its thioether analogue [Mo2O4(OC3H6SC3H6O)(2)] were synthesised. Their structural, electrochemical and oxygen atom transfer properties are compared. This is relevant for the molybdenum cofactors of the DMSO reductase family where the coordination of the active site metal occurs through O (serine/aspartate), S (cysteine) or Se (selenocysteine). Both structures are almost identical except for those parameters that are directly derived from the different sizes of the varied ligand atoms (Se and S). No trans influence was observed. The metal centered redox process ((MoMoVI)-Mo-V ($) over left right arrow) is at slightly lower voltage for the sulfur than for the selenium complex. The selenium compound catalyses the oxygen atom transfer from DMSO to PPh3 by a different mechanism and at a higher rate than the sulfur compound, which is an indication that cysteine and selenocysteine might be used for a purpose in the different molybdenum and tungsten cofactors.

The influence of the ligands on the formation and stability of mu-oxo-bridged Ti(IV) complexes has been studied. Reaction of LTiCl3 (1) and LAlMe(OLi) (L = HC(CMeN(2,6-iPr(2)C(6)H(3)))(2), "NacNac") afforded intermediate LTiCl2(mu-O)AlMeL (5) in solution, which was converted to LTiCl(mu-O)(2)TiClL (6) and LAlMeCl within 2 days. The decomposition of 5 was estimated to be thermodynamically favorable. The interaction of LTiMe3 (3) and LAlMe(OH) yielded the intermediate LTiMe2(mu-O)AlMeL ( 7). Complex 7 decomposes in solution giving the titanium oxo complex LTiMe(O) (8) and LAlMe2. The calculated Delta G(298) for this reaction is -128 kJ mol(-1). The degradation of LTiMe2(mu-O)AlMeL is slow and follows first order kinetics with k(2) = 4.09(7) x 10(-7) s(-1). The dimeric complex LTiMe(mu-O)(2)TiMeL-toluene (9a) was isolated from the reaction of 3 with LAlMe(OH) in toluene and LTiMe(mu-O)(2)TiMeL-hexane (9b) from hexane. The dimerization of 8 yielding LTiMe(mu- O)(2)TiMeL (9) is marginally endothermic, with a calculated Delta G(298) of +27 kJ mol(-1). The formation of the solid 9 is due to the lattice stabilization. The solid mu-oxo-bridged complex 9 and Mes(3)Ga were obtained from the reaction of LTiMe3 with [Mes(2)Ga(OH)](2)-THF in toluene, and 9 was also isolated from the reaction of LTiMe3 with 1 equiv. of H2O in toluene. Compounds LTiCl3 (1), LTiCl(mu-O)(2)TiClL (6), 9a and 9b have been characterized by X-ray single crystal structure, NMR, IR, EI- MS and elemental analysis. Complexes 5, 7 and 8 have been characterized by NMR. Compounds 3, 6 and 9 possess moderate catalytic activity in the polymerization of ethylene.

Depending on the reaction conditions, ketones react with n-BuLi, tert-BuLi or lithium diisopropylamide to give enolates or alcoholates. In the reaction of tert-butylmethylketone with n-BuLi followed by fluorosilanes, the fluorosilyl-enolates H2C=C(O-SiFRR′)CMe3 (1 - 4) and fluorosilylethers Me3C(CH3)(n-C4H9)C-O-SiFRR′ (5 - 8) [R,R′ = Me (1, 5); F, CMe3 (2, 6); F, C6H5 (3, 7); F, CHMe2 (4, 8)] are formed. Using tert-butylmethylketone, n-BuLi and (Me3C)2SiF2, isobutene and the fluorosilyl-enolate of acetaldehyde H2C=CH-O-SiF(CMe3)2 (9) are obtained. Diisopropylketone reacts with Me3CLi and fluorosilanes to give the fluorosilyl-enolates Me2C=C(O-SiFRR′)CHMe2 (10, 11) and -ethers,Me3C(Me2HC)2C-O-SiFRR′ (12, 13) [R,R′ = Me (10, 11); F, CMe3 (12, 13)] whereas only the silylethers R(Me)(C6H5)C-O-SiFRR′ [R, R′, R′′ = n-C4H9, Me, Me (14); C6H5, F, Me (15)] are generated in the reaction of H3C(C6H5)C=O with lithium-alkyls and fluorosilanes. 1- Di(tert-butyl)fluorosiloxy-1-cyclohexene (16) is the product of the reaction of lithiated cyclohexanone and (Me3C)2SiF2. A side reaction of the enolate formation is often a condensation releasing water. For that reason, acyclic and cyclic siloxanes may appear as by-products, e. g. disiloxane (17) using (Me3C)2SiF2, cyclotrisiloxane (Me3C(C6H5)Si-O)3 (18) using Me3(C6H5)SiF2, or cyclotetrasiloxane (Me3CSiF-O)4 (19) using Me3CSiF3 in these reactions. Attempts to prepare the enolate of cyclopentanone in the reaction with lithium diisopropylamide lead to the formation of 2,5-dicyclopentylidenepentanone (20). The 3,5,7-triphenyl-3-methyl-4,6-hexadienephenone (21) is an aldol condensate of Me(C6H5)CO. Lithium-tert-butylmethylenolate reacts with fluorosilyl-enolates 1 - 3 or SiF4 to give bis(enolato)silanes, (H2C=C(CMe3)O-)2SiRR′ [R, R′ = Me (22); F, CMe3 (23); F, C6H5 (24);] and the tris(enolato)silanes (H2C=C(CMe3)O-)3SiR [R = C6H5 (25); F (26)]. Aminosilyl-enolates H2C=C(O-SiR′R′′-NHR)CMe3 are obtained in reactions of fluorosilyl-enolates with lithium amide [27: R= CMe3, R′= Me, R′′= Me; 28: R= C6H5, R′= F, R′′= CMe3;]. Results of the crystal structure determinations of 17, the cis-isomer of 18, one trans-isomer of 19, the pentanone 20, and the hexadienephenone 21 are reported.

Two single oxygen-bridged heterobimetallic oxides of Al(III) with group 4 metals (Ti, Hf) have been prepared. The reaction of LAlMeOH (1) [L = CH(N(Ar)(CMe))2, Ar = 2,6-iPr2C6H3] with dimethylmetallocenes of Ti and Hf in toluene (80 degrees C) and ether (room temperature), respectively, resulted in the formation of LAl(Me)(mu-O)M(Me)Cp2 [M = Ti (2), Hf (3)] in moderate to good yield. Compounds 2 and 3 were characterized by elemental analysis, IR, NMR (1H and 13C), EI-MS, and single-crystal X-ray structural analysis. Furthermore, compound 2 showed good catalytic activity in ethylene and styrene homopolymerization, while compound 3 is less active in ethylene polymerization. The styrene polymerization yields atactic polystyrene.

5,5-Dimethylcyclohexane-1,3-dione (dimedone) and cyclohexane-1,3-dione react with Cl2Si(CMe3)2 in the presence of triethylamine to give the bis(1-cyclohexene-3-on-1-oxy)dit butylsilanes 2 and 3. Using dimedone and Cl2SiMe2, the analogous dimethylsilane 1 is obtained. A 1,4-Michael-Addition occurs using cyclohexane-1,3-dione in the reaction with Cl2SiMe2 to give a spirocyclic diketone (4). The reaction of cyclohexane-1,3-dione with lithium-diisopropylamide and F3SiCMe3 leads to the formation of a salt [iPr2NH2]2HF[C6H7O2]2, 5. The crystal structures of 2 - 5 were determined.

C7H16MoN2O5, monoclinic, C12/c1 (no. 15), a = 6.651(1) Å, b = 12.862(3) Å, c = 25.968(5) Å, 1 = 95.82(3)°, V = 2210.1 Å, Z = 8, Rgt(F) = 0.024, wRref(F) = 0.051, T = 103 K. Source of material The synthesis ofMoO2(O(CH2)2NH(CH2)2O) was reported previously by Mozgin et al. by the reaction of molybdic acid and diethanolamine in water under reflux conditions [1]. Herein, we report a novel synthetic route for the preparation of this compound as DMF adduct. A solution of diethanolamine (0.46 g, 1.4 mmol) in DMF (20 mL) was added to a solution of MoO2(acac)2 (0.15 g, 1.4mmol) inDMF (20mL) atRT.Themixture was stirred over night and the resulting yellow solution isolated by filtration. After concentrating the solution in vacuo to half of its volume, it yielded yellow X-ray quality crystals of [MoO2(O(CH2)2NH(CH2)2O)(dmf)] over night (yield 0.16 g, 49 % based onMo). Experimental details Hydrogen atoms were attached at idealized positions on carbon atomswithUiso related to theUeq of the parent atoms andwere refined with the riding model. H100 bound to secondary amine nitrogen N1 was found and refined freely. Discussion Diethanolateamine is a well-known and widely used ligand system and its dioxomolybdenum compound has been studied thoroughly [1]. To our surprise no crystal structure of this complex or any related molybdenum diethanolateamine complex was published so far although several complexes of this ligand with other transition and main group metals are structurally characterized [2-7]. The title complex consists of a discrete mononuclear unit, in which the diethanolateamine is coordinated to the molybdenum atom as a tridentate ligand to form two five-membered rings.Two oxo ligands coordinate to the metal to form a stable cis-dioxomolybdenum(VI) core.ADMFmolecule trans to one oxo group completes the distorted octahedral coordination sphere. Themetrical parameters are as expected for mononuclear cis-dioxo-molybdenum (VI) species. TheMo/O distances are 1.717(2)Å (O4 trans toDMF) and 1.723(2)Å (O3 trans toN).They are common for structures with the cis-[MoO2] unit in the range of 1.66 Å – 1.76 Å [8]. The bond lengths ofMo—Oalkoxy of 1.926(2) Å and 1.922(2)Å, are consistent with molybdenum (VI) alkoxide interactions [9,10]. The Mo—N distance of 2.292(2) Å is long as a consequence of the strong trans influence of an oxo ligand (O3). Again this is in the range of analogous complexes with the MoO2 core (2.28 Å – 2.50 Å) [11]. The length of theMo—O5 bond is 2.438(2) Å which is rather long, implying a very weak bonding interaction between themolybdenum and theDMFmolecule. This coordination nevertheless allows to obtain a stable distorted octahedral environment. TheMo—O(DMF) distance is longer thanMo—O distances formed by other solvent molecules e.g.MeOHwith 2.289Å – 2.385Å [8,12] orH2Owith 2.255Å – 2.293 Å [13]. The comparably weak bonding interaction indicates thatDMF is particularly easy to remove from the molecule. The most evident distortions of the structure from the idealized octahedral environment are defined by theN1–Mo–O1 (75.81(7)°), N1–Mo–O2 (74.97(7)°) and O1–Mo–O2 (146.43(7)°) angles. With the strain of two five-membered chelate rings, two alkoxy groups are bent towards the nitrogen atom. Z. Kristallogr. NCS 222 (2007) 215-216 / DOI 10.1524/ncrs.2007.0089 215 © by OldenbourgWissenschaftsverlag,München Crystal: yellow block, size 0.20 × 0.20 × 0.20 mm Wavelength: Mo K0 radiation (0.71073 Å) %: 11.92 cm−1 Diffractometer, scan mode: Stoe IPDS II, ) 2'max: 52.76° N(hkl)measured, N(hkl)unique: 22638, 2259 Criterion for Iobs, N(hkl)gt: Iobs > 2 ((Iobs), 2193 N(param)refined: 142 Programs: SHELXS-97 [14], SHELXL-97 [15], DIAMOND [16] Table 1. Data collection and handling.