First examples of neutral and cationic indenyl nickel(II) complexes bearing arsine or stibine ligands: highly active catalysts for the oligomerisation of styrene.

New indenyl nickel(ii) complexes bearing arsine or stibine ligands synthesised by a new methodology exhibit very high catalytic activities for the oligomerisation of styrene.

Molecular docking study of conformational polymorph: building block of crystal chemistry.

Two conformational polymorphs of novel 2-[2-(3-cyano-4,6-dimethyl-2-oxo-2H-pyridin-1-yl)-ethoxy]-4,6-dimethyl nicotinonitrile have been developed. The crystal structure of both polymorphs (1a and 1b) seems to be stabilized by weak interactions. A difference was observed in the packing of both polymorphs. Polymorph 1b has a better binding affinity with the cyclooxygenase (COX-2) receptor than the standard (Nimesulide).

Counteranion and solvent assistance in ruthenium-mediated alkyne to vinylidene isomerizations.

The complex [Cp*RuCl((i)Pr2PNHPy)] (1) reacts with 1-alkynes HC≡CR (R = COOMe, C6H4CF3) in dichloromethane furnishing the corresponding vinylidene complexes [Cp*Ru═C═CHR((i)Pr2PNHPy)]Cl (R = COOMe (2a-Cl), C6H4CF3 (2b-Cl)), whereas reaction of 1 with NaBPh4 in MeOH followed by addition of HC≡CR (R = COOMe, C6H4CF3) yields the metastable π-alkyne complexes [Cp*Ru(η(2)-HC≡CR)((i)Pr2PNHPy)][BPh4] (R = COOMe (3a-BPh4), C6H4CF3 (3b-BPh4)). The transformation of 3a-BPh4/3b-BPh4 into their respective vinylidene isomers in dichloromethane is very slow and requires hours to its completion. However, this process is accelerated by addition of LiCl in methanol solution. Reaction of 1 with HC≡CR (R = COOMe, C6H4CF3) in MeOH goes through the intermediacy of the π-alkyne complexes [Cp*Ru(η(2)-HC≡CR)((i)Pr2PNHPy)]Cl (R = COOMe (3a-Cl), C6H4CF3 (3b-Cl)), which rearrange to vinylidenes in minutes, i.e., much faster than their counterparts containing the [BPh4](-) anion. The kinetics of these isomerizations has been studied in solution by NMR. With the help of DFT studies, these observations have been interpreted in terms of chloride- and methanol-assisted hydrogen migrations. Calculations suggest participation of a hydrido-alkynyl intermediate in the process, in which the hydrogen atom can be transferred from the metal to the ß-carbon by means of species with weak basic character acting as proton shuttles.

Functionalized N-heterocyclic carbene nonspectator ligands upon internal alkyne activation reactions.

When studying the activation of 3-arylpropiolates by [TpRu(picolyl-(R)I)Cl]/NaBAr(F)4 (picolyl-(Me)I = 3-methyl-1-(2-picolyl)imidazol-2-ylidene (1); picolyl-(Me)BI = 3-methyl-1-(2-picolyl)benzoimidazol-2-ylidene (2)) a migratory insertion of the NHC into a ruthenium-carbon bond and an unprecedented C-N bond activation of the chelating picolyl-NHC ligand take place to give the new ruthenium metallacycles [TpRu(κ(3)-C,N,N'-═C(Ph)-C(CH2Py)(CO2Me)((Me)I)][BAr(F)4] 3a and 4a and [TpRu(κ(3)-C,N,N'-═C(4-CF3Ph)-C(CH2Py)(CO2Me)((Me)I)][BAr(F)4] 3b and 4b. X-ray crystal structures of 3a and 3b are reported, and a mechanistic pathway is proposed. In contrast, activation of internal alkynones by a mixture of [TpRu(picolyl-(Me)I)Cl] complex (1) and NaBAr(F)4 led to isolation and characterization of the corresponding disubstituted vinylidene complexes. Also, structures of [TpRu(picolyl-(Me)I)(═CC(COR)(Ph)][BAr(F)4] (R = Me (6a); Ph (6b)) are reported.

Picolyl-NHC hydrotris(pyrazolyl)borate ruthenium(II) complexes: synthesis, characterization, and reactivity with small molecules.

Ruthenium(II) hydrotris(pyrazolyl)borate chloro complexes bearing picolyl-functionalized N-heterocyclic carbenes [TpRu(κ(2)-C,N-picolyl-(R)I)Cl] (picolyl-(Me)I = 3-methyl-1-(2-picolyl)imidazol-2-ylidene) (1a), picolyl-(iPr)I = 3-isopropyl-1-(2-picolyl)imidazol-2-ylidene (1b), picolyl-(Me)45DClI = 3-methyl-1-(2-picolyl)-4,5-dichloroimidazol-2-ylidene (1c), picolyl-(Ph)I = 3-phenyl-1-(2-picolyl)imidazol-2-ylidene (1d), picolyl-(Me)BI = 3-methyl-1-(2-picolyl)benzoimidazol-2-ylidene (1e)) have been synthesized and characterized. Furthermore, cationic carbonyl derivatives 2a-e have been prepared, characterized, and used to study the donor properties of the picolylcarbene ligands (picolyl-(R)I) via infrared spectroscopy. Also, the reactivity of the 16-electron species [TpRu(κ(2)-C,N-picolyl-(R)I)](+), in situ generated using NaBAr(F)4 (Ar(F) = 3,5-bis(trifluoromethyl)phenyl) as a halide scavenger, toward N2, CH3CN, H2, CH2CH2, S8, and O2 was studied indicating a strong influence of the NHC wingtip and backbone substituents in the product distribution. The crystal structures of [TpRu(κ(2)-C,N-picolyl-(iPr)I)Cl] (1b), [TpRu(κ(2)-C,N-picolyl-(Me)I)CO][BAr(F)4] (2a), [TpRu(κ(2)-C,N-picolyl-(Ph)I)CO][BAr(F)4] (2d), [{TpRu(κ(2)-C,N-picolyl-(Me)I}2(µ-N2)][BAr(F)4]2 (3'a), [{TpRu(κ(2)-C,N-picolyl-(Ph)I)}2(µ-N2)][BAr(F)4]2 (3'd), [TpRu(κ(2)-C,N-picolyl-(iPr)I)(η(2)-CH2CH2)][BAr(F)4] (5b), and [{TpRu(κ(2)-C,N-picolyl-(Me)I)}2(µ-S2)][BAr(F)4]2 (6) are reported.

Facile O-H bond activation in alcohols by [Cp*RuCl((I)Pr2PSX)] (X = pyridyl, quinolyl): a route to ruthenium(IV) hydrido(alkoxo) derivatives.

The complexes [Cp*RuCl((i)Pr(2)PSX)] (X = pyridyl, quinolyl) react directly with alcohols ROH (R = Me, Et, (i)Pr, (n)Pr) and NaBPh(4), affording the novel cationic hydrido(alkoxo) derivatives [Cp*RuH(OR)((i)Pr(2)PSX)][BPh(4)]. These ruthenium(IV) compounds result from the formal oxidative addition of the alcohol to the 16-electron fragment {[Cp*Ru((i)Pr(2)PSX)](+)}, generated in situ upon chloride dissociation. The hydrido(alkoxo) complexes are reversibly deprotonated by a strong base such as KOBu(t), yielding the neutral alkoxides [Cp*Ru(OR)((i)Pr(2)PSX)], which are remarkably stable toward ß elimination and do not generate the corresponding hydrides. The hydrido(alkoxo) complexes undergo a slow electron-transfer process, releasing H(2) and generating the dinuclear ruthenium(III) complex [{Cp*Ru(κ(2)-N,S-µ S-SC(5)H(4)N)}(2)][BPh(4)](2). In this species, the Ru-Ru separation is very short and consistent with what is expected for a Ru≡Ru triple bond.

Friedel-Craft acylation of ar-himachalene: synthesis of acyl-ar-himachalene and a new acyl-hydroperoxide.

Friedel-Craft acylation at 100 °C of 2,5,9,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocycloheptene [ar-himachalene], a sesquiterpenic hydrocarbon obtained by catalytic dehydrogenation of α-, ß- and γ-himachalenes, produces a mixture of two compounds: (3,5,5,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocyclohepten-2-yl)-ethanone (2, in 69% yield), with a conserved reactant backbone, and 3, with a different skeleton, in 21% yield. The crystal structure of 3 reveals it to be 1-(8-ethyl-8-hydroperoxy-3,5,5-trimethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-ethanone. In this compound O-H…O bonds form dimers. These hydrogen-bonds, in conjunction with weaker C-H…O interactions, form a more extended supramolecular arrangement in the crystal.

Importance of weak interactions in developing 1,3-bis(4,6-dimethyl-1H-nicotinonitrile-1-yl)1,3-dioxy propane polymorphs.

The structure of 1,3-bis(4,6-dimethyl-1H-nicotinonitrile-1-yl)1,3-dioxy propane polymorphs has been characterized by X-ray diffraction, FT-IR, 1H and 13C NMR spectroscopies. The influence of intra and intermolecular weak interactions is thoroughly studied in solid state using single crystal X-ray diffraction and FT-IR. These polymorphs belong to monoclinic space group 'P2(1/n)' and 'P2(1/c)'. These polymorphs have C-H⋯n (lone pair), hydrogen bonds, C-N⋯π, C-H⋯π and π⋯π intermolecular non-covalent interactions. These polymorphs are the result of weak interactions and solvent used in crystallization. The FT-IR spectra have been recorded in the solid phase and NMR has been recorded in solvent. The optimized geometry has been calculated by B3LYP methods using different basis sets. The FT-IR and NMR spectra of 1st polymorphs has been calculated at B3LYP/6-31G (d) level. The scaled theoretical wave number showed good agreement with the experimental values. These two polymorphs as well as other stereomers are studied by DFT calculations.

Ni(0)-CMC-Na - nickel colloids in sodium carboxymethyl-cellulose: catalytic evaluation in hydrogenation reactions.

A recyclable catalyst, Ni(0)-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na), was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations.

Proton-transfer reactions to half-sandwich ruthenium trihydride complexes bearing hemilabile P,N ligands: experimental and density functional theory studies.

The trihydride complexes [Cp*RuH(3)(kappa(1)-P-(i)Pr(2)PCH(2)X)] [X = pyridine (Py), 2a; quinoline (Quin), 2b] have been prepared by reaction of the corresponding chloro derivatives [Cp*RuCl(kappa(2)-P,N-(i)Pr(2)PCH(2)X)] [X = Py (1a), Quin (1b)] with NaBH(4) in methanol. Both 2a and 2b exhibit quantum-mechanical exchange coupling. The proton-transfer reactions to 2a and 2b using strong as well as weak proton donors have been experimentally and computationally studied. Density functional theory studies have been performed to analyze the stability of the proposed species, the hydrogen exchange, and the protonation pathway. The reactions with weak donors such as PhCOOH, indole, or salicylic acid in benzene or toluene result in the formation of hydrogen-bonded adducts between the proton donor and the pendant pyridine or quinoline group. However, in a more polar solvent such as dichloromethane, there is spectral evidence for the proton transfer to the hydride to yield a dihydrogen complex. The protonation with CF(3)SO(3)H in CD(2)Cl(2) occurs in a stepwise manner. In a first step, the pendant pyridine or quinoline group is protonated to yield [Cp*RuH(3)(kappa(1)-P-(i)Pr(2)PCH(2)XH)](+) [X = Py (4a) or Quin (4b)]. The NH proton is then transferred to the hydride and one molecule of dihydrogen is released, furnishing the cationic mono(dihydrogen) complexes [Cp*Ru(H(2))(kappa(2)-P,N-(i)Pr(2)PCH(2)X)](+) [X = Py (5a) or Quin (5b)]. These species are thermally stable and do not undergo irreversible rearrangement to their dihydride isomers. In the presence of an excess of acid, a second protonation occurs at the hydride site and the dicationic complexes [Cp*RuH(4)(kappa(1)-P,N-(i)Pr(2)PCH(2)XH)](2+) [X = Py (6a) or Quin (6b)] are generated. These species are stable up to 273 K and consist of equilibrium mixtures between bis(dihydrogen) and dihydrido(dihydrogen) tautomeric forms. Above this temperature, 6a and 6b are converted into the corresponding cationic mono(dihydrogen) complexes 5a/5b. The crystal structures of [Cp*RuCl(kappa(2)-P,N-(i)Pr(2)PCH(2)Quin)] (1b), [Cp*RuH(3)(kappa(1)-P-(i)Pr(2)PCH(2)Quin)] (2b), [Cp*RuH(3)(kappa(1)-P-(i)Pr(2)PCH(2)Py...H...OOCC(6)H(4)OH)] (3a), [Cp*Ru(H(2))(kappa(2)-P,N-(i)Pr(2)PCH(2)Quin)][BAr'(4)] (5b), [Cp*Ru(N(2))(kappa(2)-P,N-(i)Pr(2)PCH(2)Quin)][BAr'(4)] (8b), and [Cp*Ru(O(2))(kappa(2)-P,N-(i)Pr(2)PCH(2)Quin)][BAr'(4)] (9b) are reported.

[(1R)-3-Benzoyl-1,7,7-trimethyl-bicyclo-[2.2.1]heptan-2-onato-κO,O']chlorido(η-p-cymene)ruthenium(II).

The asymmetric unit of the title compound, [RuCl(C(10)H(14))(C(17)H(19)O(2))], contains two diastereomers. In both, the Ru(II) ion has a tetra-hedral coordination, formed by two O atoms of the camphor-derived ligand and the p-cymene and Cl ligands. In the crystal structure, weak inter-molecular C-H⋯Cl inter-actions link the mol-ecules into columns propagated along [010].

4-Chloro-N-methyl-2-(1,2,3,4-tetra-hydro-isoquinolin-1-yl)aniline.

The racemic title compound, C(16)H(17)ClN(2), shows a tetra-hydro-isoquinoline skeleton with a 4-chloro-N-methyl-aniline group linked to the C atom at position 1. The dihedral angle between the benzene rings is 85.82 (4)°. An intra-molecular N-H⋯N hydrogen bond occurs. In the crystal, mol-ecules are linked through inter-molecular C-H⋯π inter-actions.

Oligomerization of styrenes mediated by cationic allyl nickel complexes containing triphenylstibine or triphenylarsine.

The cationic complexes [Ni(eta(3)-CH(2)C(R)CH(2))(SbPh(3))(3)][BAr'(4)] (R = CH(3), H ; Ar' = 3,5-C(6)H(3)(CF(3))(2)), [Ni(eta(3)-CH(2)C(R)CH(2))(AsPh(3))(2)][BAr'(4)] (R = CH(3), H ), [Ni(eta(3)-CH(2)CHCH(2))(PPh(3))(L)][BAr'(4)] (L = SbPh(3), AsPh(3)), and the neutral derivatives [Ni(eta(3)-CH(2)C(R)CH(2))Br(L)] (L = SbPh(3), R = CH(3), H ; L = AsPh(3), R = CH(3), H ) have been prepared and characterized. The X-ray crystal structures of , , , and have been determined. These complexes are very active catalyst precursors for the low-molecular weight oligomerization of RC(6)H(4)CH[double bond, length as m-dash]CH(2) to mainly dimers and trimers of styrene (R = H) or 4-methylstyrene (R = CH(3)). They also catalyse the oligomerization of alpha-methylstyrene to dimers and trimers, or to higher oligomers depending upon the reaction conditions (solvent and temperature). The oligomerization reactions were carried out at 25 degrees C in most cases, in dichloromethane, 1,2-dichloroethane or fluorobenzene, using a olefin/catalyst ratio equal to 2000. The oligomerization products were characterised by means of GPC/SEC.

(E)-2-(2-Nitro-ethen-yl)furan.

The title compound, C(6)H(5)NO(3), was synthesized via condensation of furfural with nitro-methane in the presence of isobutyl-amine. The compound crystallizes exclusively as the E isomer. The angle between the mean planes of the furan ring and the nitro-alkenyl group is 1.3 (2)°.

(E)-2-(2-Nitro-prop-1-en-yl)furan.

Crystals of the title compound, C(7)H(7)NO(3), under Mo Kα radiation sublime in less than 1h at room temperature. However, it was possible to collect data at 100K. It crystallized as the E isomer only. A double-bond conjugation in the furan ring is extended to the nitro-alkenyl group. Mol-ecular associations were realized in the crystal through N⋯π [3.545 (2) Å] inter-actions involving the furan ring and C-H⋯O hydrogen bonds.

Formation of a coordinated 2-aminoethylidene ligand and its rearrangement by deprotonation into a phosphinoallyl ligand containing a pyrrolidin-2-yl ring.

The activation of 1,1-diphenyl-2-propyn-1-ol by the metallic fragment [(eta (5)-C 5Me 5)Ru(dippae)] (+) {dippae = 1,2-bis[(diisopropylphosphanyl)amino]ethane}, followed by dehydration, produces a cationic complex that, by deprotonation and rearrangement, leads to a neutral complex with a phosphinoallyl ligand containing a pyrrolidin-2-yl ring.

Synthesis, structure, antimicrobial and antioxidant investigations of dicoumarol and related compounds.

Different substituted 3,3'-arylidenebis-4-hydroxycoumarins (1-7) and tetrakis-4-hydroxycoumarin derivative 8 are the final products when 4-hydroxycoumarin and aromatic aldehydes containing different groups in ortho, meta or para positions condense in boiling ethanol or acetic acid. Upon heating 3,3'-arylidenebis-4-hydroxycoumarins, and tetrakis-4-hydroxycoumarin derivative in anhydride acetic acid, the epoxydicoumarins (9-16) were formed. From a study of nuclear magnetic resonance and infrared spectra, intramolecularly hydrogen-bonded structures are proposed for the dicoumarols (1-8). A possible relationship between such hydrogen-bonded structures and the antimicrobial and the antioxidant activities of compounds 1-8 is suggested.

Oligomerization and regioselective hydrosilylation of styrenes catalyzed by cationic allyl nickel complexes bearing allylphosphine ligands.

The complexes [Ni(eta(3)-CH(2)CHCH(2))Br(kappa(1)P-PR(2)CH(2)CH=CH(2))] (R = Ph 1, (i)Pr2 ) and [Ni(eta(3)-CH(2)C(R')CH(2))(kappa(1)P-PR(2)CH(2)CH=CH(2))(2)][BAr'(4)] (R' = H, R = Ph 4a, R = (i)Pr 4b; R' = CH(3), R = Ph 5a, R = (i)Pr 5b; Ar' = 3,5-C(6)H(3)(CF(3))(2)) have been prepared and characterized. The X-ray crystal structures of 1, 2 and 5b have been determined. 4a-b and 5a-b are catalyst precursors for the oligomerization of RC(6)H(4)CH=CH(2) to oligostyrene (R = H) or oligo(4-methylstyrene) (R = CH(3)) respectively, without the need of a co-catalyst such as methylalumoxane. The catalytic activities range from moderate to high. The oligomerization reactions are carried out in the temperature interval 25-40 degrees C in 1,2-dichloroethane, using an olefin/catalyst ratio equal to 200, yielding oligostyrenes with a high isotactic fraction content P(m), with M(n) in the range 700-1900 Dalton, and polydispersities between 1.22 and 1.64. The cationic complexes 4a-b and 5a-b are also effective catalyst precursors for the hydrosilylation reactions of styrene or 4-methylstyrene with PhSiH(3) in 1,2-dichloroethane at 40 degrees C using an olefin/catalyst ratio equal to 100, leading selectively to RC(6)H(4)CH(SiH(2)Ph)CH(3) (R = H, CH(3)) in 50-79% yield.

Coordinatively unsaturated semisandwich complexes of ruthenium with phosphinoamine ligands and related species: a complex containing (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane in a new coordination form kappa(3)P,P',N-eta(2)-P,N.

The syntheses of the chloro complexes [Ru(eta5-C5R5)Cl(L)] (R = H, Me; L = phosphinoamine ligand) (1a-d) have been carried out by reaction of [(eta5-C5H5)RuCl(PPh3)2] or {(eta5-C5Me5)RuCl}4 with the corresponding phosphinoamine (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane), R,R-dippach, or 1,2-bis(((diisopropylphosphino)amino)ethane), dippae. The chloride abstraction reactions from these compounds lead to different products depending on the starting chlorocomplex and the reaction conditions. Under argon atmosphere, chloride abstraction from [(eta5-C5Me5)RuCl(R,R-dippach)] with NaBAr'4 yields the compound [(eta5-C5Me5)Ru(kappa3P,P'-(R,R)-dippach)][BAr'4] (2b) which exhibits a three-membered ring Ru-N-P by a new coordination form of this phosphinoamine. However, under the same conditions the reaction starting from [(eta5-C5Me5)RuCl(dippae)] yields the unsaturated 16 electron complex [(eta5-C5Me5)Ru(dippae)][BAr'4] (2d). The bonding modes of R,R-dippach and dippae ligands have been analyzed by DFT calculations. The possibility of tridentate P,N,P-coordination of the phosphinoamide ligand to a fragment [(eta5-C5Me5)Ru]+ is always present, but only the presence of a cyclohexane unit in the ligand framework converts this bonding mode in a more favorable option than the usual P,P-coordination. Dinitrogen [(eta5-C5R5)Ru(N2)(L)][BAr'4] (3a-d) and dioxygen complexes [(eta5-C5H5)Ru(O2)(R,R-dippach)][BPh4] (4a) and [(eta5-C5Me5)Ru(O2)(L)][BPh4] (4b,d) have been prepared by chloride abstraction under dinitrogen or dioxygen atmosphere, respectively. The presence of 16 electron [(eta5-C5H5)Ru(R,R-dippach)]+ species in fluorobenzene solutions of the corresponding dinitrogen or dioxygen complexes in conjunction with the presence of [BAr'4]- gave in some cases a small fraction of [Ru(eta5-C5H5)(eta6-C6H5F)][BAr'4] (5a), which has been isolated and characterized by X-ray diffraction.

Half-sandwich hydride complexes of ruthenium with bidentate phosphinoamine ligands: proton-transfer reactions to [(C5R5)RuH(L)] [R = H, Me; L = dippae, (R,R)-dippach].

The complexes [(C5R5)RuH(dippae)] [R = H (1a), Me (2a); dippae = 1,2-bis(diisopropylphosphinoamino)ethane] and [(C5R5)RuH((R,R)-dippach)] [R = H (1b), Me (2b); (R,R)-dippach = (R,R)-1,2-bis(diisopropylphosphinoamino)cyclohexane] have been prepared and characterized. The cationic ruthenium(IV) dihydride derivatives [(C5R5)RuH2(dippae)][BPh4] [R = H (3a), Me (4a)] and [(C5R5)RuH2((R,R)-dippach)][BPh4] [R = H (3b), Me (4b)] are also reported. No significant intramolecular interaction between the amino protons and the hydrogen atoms bound to the metal has been observed in any of these compounds. The X-ray crystal structure of 4a was determined. The proton-transfer processes over the monohydrides 2a and 2b with HBF4.OEt2 have been studied by NMR spectroscopy. Dicationic dihydride complexes [CpRuH2(LH)]2+ [LH = dippaeH+ (5a), (R,R)-dippachH+ (5b)] and [Cp*RuH2(LH)]2+ [LH = dippaeH+ (6a), (R,R)-dippachH+ (6b)] result respectively from the protonation of either the monohydrides 1a,b or 2a,b or the dihydrides 3a,b or 4a,b at one of the NH groups of the phosphinoamine ligands by an excess of HBF4. These dicationic derivatives exhibit fluxional behavior in solution. In the course of the protonation of 1a with HBF4.OEt2, a cationic dihydrogen complex and a dihydrogen-bonded derivative have been identified as intermediates by NMR spectroscopy. Another dihydrogen species, namely, [CpRu(H...HOOCPh)((R,R)-dippach)], was also identified in the course of the reaction of 1b with benzoic acid in toluene-d8. The reaction of 1a with 0.5 equiv of 1,1,1,3,3,3-hexafluoroisopropanol generates a hydride species having a very short (T1)min of 6.5 ms at 400 MHz, an experimental fact for which no satisfactory explanation has yet been found.