Formation,Dynamic Behavior,and Chemical Transformation of Pt Complexes with a Rotaxane‐like Structure

The reaction of [Pt(CH₂COMe)(Ph)(cod)] (cod=1,5‐cyclooctadiene) with (ArCH₂NH₂CH₂‐C₆H₄COOH)⁺(PF₆)^? (Ar=4‐tBuC₆H₄ or 9‐anthryl) in the presence of cyclic oligoethers such as dibenzo[24]crown‐8 (DB24C8) and dicyclohexano[24]crown‐8 (DC24C8) produces {(ce)[ArCH₂NH₂CH₂C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? (ce=DB24C8 or DC24C8, Ar=4‐tBuC₆H₄ or 9‐anthryl) with interlocked structures. FABMS and NMR spectra of a solution of these compounds indicate that the Pt complexes with a secondary ammonium group and DB24C8 (or DC24C8) make up the axis and cyclic components, respectively. Temperature‐dependent ¹H NMR spectra of a solution of {(DB24C8)[4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? ({(DB24C8)[ 4 ‐H]}⁺(PF₆)^?) show equilibration with free DB24C8 and the axis component. The addition of DB24C8 to a solution of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^? causes partial exchange of the macrocyclic component of the interlocked molecules, giving a mixture of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^?, {(DB24C8)[ 4 ‐H]}⁺(PF₆)^?, and free macrocyclic compounds. The reaction of 3,5‐Me₂C₆H₃COCl with {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? affords the organic rotaxane {(DB24C8)(4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOCOC₆H₃Me₂‐3,5)}⁺(PF₆)^? through C? O bond formation between the aroyl group and the carboxylate ligand of the axis component. The addition of 2,2′‐bipyridine (bpy) to a solution of {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? induces the degradation of the interlocked structure to form a complex with trigonal bipyramidal coordination, [Pt(Ph)(bpy)(cod)]⁺(PF₆)^?, whereas the reaction of bpy with [Pt(OCOC₆H₄Me‐4)(Ph)(cod)] produces the square‐planar complex [Pt(OCOC₆H₄Me‐4)(Ph)(bpy)].     

Achieving strictly linear polyethylenes by the NNN-Fe precatalysts finely tuned with different sizes of ortho-cycloalkyl substituents

Six examples of newly synthesized α,α’-bis (aryl)-2,3:5,6-bis (pentame thylene)pyridyliron complexes [2,3:5,6-{C₄H₈C(NAr)}₂C₅HN]FeCl₂ (Ar = 2-(c-C₅H₉)-6-MeC₆H₃ Fe1 , 2-(c-C₆H₁₁)-6-MeC₆H₃ Fe2 , 2-(c-C₈H₁₅)-6-MeC₆H₃ Fe3 , 2-(c-C₅H₉)-4,6-Me₂C₆H₂ Fe4 , 2-(c-C₆H₁₁)-4,6-Me₂C₆H₂ Fe5 , 2-(c-C₈H₁₅)-4,6-Me₂C₆H₂ Fe6 ; c refers as cyclic), on activation with methylalumoxane (MAO) or modified MAO (MMAO), exhibit high activities towards ethylene polymerization, producing strictly linear polyethylenes with terminal vinyl groups. The catalytic performances are systematically investigated along with various polymerization parameters as well as the microstructures of resultant polyethylenes. The steric hindrances of ortho-cycloalkyl substituents of N_imino-aryl groups significantly affect the activities of the corresponding iron precatalysts as well as the microstructures of resultant polyethylenes: higher steric hindrance the ortho-cycloalkyl substituents, higher activity the iron precatalyst, lower molecular weight the resultant polyethylenes. Experimental observations are additionally supported by the computational study. The resultant polyethylenes exhibited excellent hydrophobicity.     

Mechanisms of addition of primary aromatic amines and cyclohexylamine to tricarbonyl(cycloheptatrienyl)tungsten cation

X-substituted anilines (X = H, 2-Me, 4-Me or 2-Cl) and cyclohexylamine are shown to add to the tropylium ring of cation [(η)-C₇H₇)W(CO)₃]⁺ to give the corresponding ring adducts of tricarbonyl(cyclohepta-1,3,5-triene)tungsten. Kinetic studies have demonstrated that the anilines form the triene ring adducts via the rapid pre-equilibrium formation of a π-complex, which rearranges in a rate-determining fashion to form a cationic triene intermediate [(1–6-η-C₆H₇.NH₂R)-W(CO)₃]⁺ (R = C₆H₅, 2-MeC₆H₄, 4-MeC₆H₄ or 2-ClC₆H₄); from this the final product is rapidly formed via amine- or solvent-assisted proton loss. With the aliphatic cyclohexylamine, the cationic triene intermediate is formed directly, followed by competing rate-determining solvent- and amine-assisted proton removal.     

Stoichiometric and Catalytic Aryl−Cl Activation and Borylation using NHC-stabilized Nickel(0) Complexes

NHC-nickel (NHC=N-heterocyclic carbene) complexes are efficient catalysts for the C−Cl bond borylation of aryl chlorides using NaOAc as a base and B₂pin₂ (pin=pinacolato) as the boron source. The catalysts [Ni₂(ICy)₄(μ-(η²:η²)-COD)] ( 1 , ICy=1,3-dicyclohexylimidazolin-2-ylidene; COD=1,5-cyclooctadiene), [Ni(ICy)₂(η²-C₂H₄)] ( 2 ), and [Ni(ICy)₂(η²-COE)] ( 3 , COE=cyclooctene) compare well with other nickel catalysts reported previously for aryl-chloride borylation with the advantage that no further ligands had to be added to the reaction. Borylation also proceeded with B₂neop₂ (neop=neopentylglycolato) as the boron source. Stoichiometric oxidative addition of different aryl chlorides to complex 1 was highly selective affording trans-[Ni(ICy)₂(Cl)(Ar)] (Ar=4-(F₃C)C₆H₄, 11 ; 4-(MeO)C₆H₄, 12 ; C₆H₅, 13 ; 3,5-F₂C₆H₃, 14 ).     

Synthesis, Characterization, Luminescence, and Electrochemistry of New Tetranuclear Gold(I) Amidinate Clusters: Au4[PhNC(Ph)NPh]4, Au4[PhNC(CH3)NPh]4, and Au4[ArNC(H)NAr]4

The syntheses and the X-ray structures of the tetranuclear gold(I) benzamidinate, Au₄[PhNC(Ph)NPh]₄, and the tetranuclear gold(I) acetamidinate, Au₄[PhNC(CH₃)NPh]₄, clusters are reported. The clusters are produced by the reaction of the sodium salt of an amidine ligand with the gold precursor Au(THT)Cl in a (1:1) stoichiometry. The average Au...Au distance between adjacent Au(I) atoms is ∼2.9 ?, typical of compounds having an aurophilic interaction. The four gold atoms are arranged in a square (Au...Au...Au... = 88–91°) in the acetamidinate and in a distorted square (Au...Au...Au... = 82–97°) in the benzamidinate derivative. Electrochemical oxidation of the tetranuclear complex Au₄[PhNC(Ph)NPh]₄ show three reversible waves at 0.87, 1.19, 1.42 V vs. Ag/AgCl at a scan rate of 100 mV/s in CH₂Cl₂ similar to the three reversible waves seen before from the tetranuclear complexes Au₄[ArNC(H)NAr]₄, Ar = C₆H₄-4-OMe, Ar = C₆H₄-4-Me, and Ar = C₆H₃-3,5-Cl. A summary of the chemistry of the tetranuclear Au(I) amidinate complexes Au₄[ArNC(H)NAr]₄, Ar = C₆H₄-4-OMe, C₆H₃-3,5-Cl, C₆H₄-4-Me, C₆H₄-3-CF₃, C₆F₅, C₁₀H₇ also is presented. The tetranuclear clusters Au₄[ArNC(H)NAr]₄, Ar = C₆H₄-4-OMe, Ar = C₆H₄-3-CF₃, Ar = C₆H₄-4-Me and Ar = C₆H₄-3,5-Cl are the first tetranuclear gold(I) cluster species from group 11 elements to show fluorescence at room temperature. The lifetimes of the naphthyl and trifluoromethylphenyl complexes are in the millisecond range indicating phosphorescent processes. Recently it has been shown that Au₄[ArNC(H)NAr]₄ are very effective catalysts upon calcination for room temperature CO oxidation. Congratulations to Dieter Fenske, a superb synthetic chemist with exceptional talents in cluster chemistry, on the occasion of his 65th birthday.     

Preparation of linear α‐olefins to high‐molecular weight polyethylenes using cationic α‐diimine nickel(II) complexes containing chloro‐substituted ligands

A series of α‐diimine nickel(II) complexes containing chloro‐substituted ligands, [(Ar)N?C(C₁₀H₆)C?N(Ar)]NiBr₂ ( 4a , Ar = 2,3‐C₆H₃Cl₂; 4b , Ar = 2,4‐C₆H₃Cl₂; 4c , Ar = 2,5‐C₆H₃Cl₂; 4d , Ar = 2,6‐C₆H₃Cl₂; 4e , Ar = 2,4,6‐C₆H₂Cl₃) and [(Ar)N?C(C₁₀H₆)C?N(Ar)]₂NiBr₂ ( 5a , Ar = 2,3‐C₆H₃Cl₂; 5b , Ar = 2,4‐C₆H₃Cl₂; 5c , Ar = 2,5‐C₆H₃Cl₂), have been synthesized and investigated as precatalysts for ethylene polymerization. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, these complexes are highly effective catalysts for the oligomerization or polymerization of ethylene under mild conditions. The catalyst activity and the properties of the products were strongly affected by the aryl‐substituents of the ligands used. Depending on the catalyst structure, it is possible to obtain the products ranging from linear α‐olefins to high‐molecular weight polyethylenes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1964–1974, 2006     

Facile synthesis of new polyolefinic ruthenium(0) complexes from ruthenium(II) precursors

The new ruthenium(II) complex [(C₈H₁₀)RuCl₂]_n (1) (C₈H₁₀ = 1,3,5-cyclooctatriene; n ⩾ 2) has been obtained from the reaction of RuCl₃·xH₂O with 1,3,5,7-cyclooctatetraene in refluxing ethanol. Reduction of [(C₈H₁₀)RuCl₂]_n and [(C₇H₈)RuCl₂]₂ (2) (C₇H₈ = 1,3,5-cyclooctatriene) by Na/Hg amalgam in the presence of isoprene (C₅H₈) gives the novel ruthenium(O) complexes [(η⁶-C₈H₁₀)Ru(η⁴-C₅H₈)] (3) and [(η⁶-C₇H₈)Ru(η⁴-C₅H₈)] (4). [(η⁶-C₇H₈Ru(η⁴-C₅H₈)] reacts with CO and HBF₄ to give [(η⁶-C₇H₈)Ru(η³-C₅H₉)(CO)][BF₄] (C₅H₉ = trans-1,2-dimethylallyl (5a); 1,1-dimethylallyl (5b)).     

Induced Self‐Assembly of Platinum(II) Alkynyl Complexes through Specific Interactions between Citrate and Guanidinium for Proof‐of‐Principle Detection of Citrate and an Assay of Citrate Lyase

Water‐soluble alkynylplatinum(II) terpyridine complexes appended with guanidinium moieties, [Pt(tpy)(C?C?Ar)][OTf]₂ (tpy=terpyridine; OTf=trifluoromethanesulfonate; Ar=C₆H₄‐{NHC(?NH₂⁺)(NH₂)}‐4 ( 1 ), C₆H₄‐{CH₂NHC(?NH₂⁺)(NH₂)}‐4 ( 2 )), and [Pt(tBu₃tpy)(C?CC₆H₄‐{NHC(?NH₂⁺)(NH₂)}‐4)][OTf]₂ ( 3 ; tBu₃tpy=4,4′,4′′‐tri‐tert‐butyl‐2,2′:6′,2′′‐terpyridine), have been synthesized and characterized. The photophysical properties of the complexes have been studied. Based on the results of UV/Vis absorption, resonance light scattering, and dynamic light scattering experiments, in aqueous buffer solutions complexes 1 and 2 undergo aggregation in the presence of citrate through strong and specific electrostatic and hydrogen‐bonding interactions with citrate. The emergence of a triplet metal–metal‐to‐ligand charge transfer (³MMLCT) emission in the near‐infrared (NIR) region brought on by the induced self‐assembly of complex 1 has been demonstrated for proof‐of‐principle detection of citrate with good sensitivity and selectivity over other mono‐ and dicarboxylate substrates in the tricarboxylic acid (TCA) cycle as well as phosphate and lactate anions. Such a good selectivity toward citrate has been rationalized by the high charge density of citrate under physiological conditions and specific interactions between the guanidinium moiety on complex 1 and citrate. Extension of the work to citrate detection in fetal bovine serum and real‐time monitoring of the activity of citrate lyase by the NIR emission of complex 1 have also been demonstrated.     

Reactions of [Cp*Ru(H<Subscript>2</Subscript>O)(NBD)]<Superscript>+</Superscript> with diynes

Abstract  Formal [2 + 2 + 2] addition reaction of [Cp*Ru(H₂O)(NBD)][BF₄] (NBD = norbornadiene) with 4,4′-Diethynylbiphenyl generates [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂. The reaction of [Cp*Ru(H₂O)(NBD)][BF₄] with 1,4-diphenylbutadiyne generates the unusual [2 + 2 + 2] additional organic compound Ph–C≡C–C₉H₈–Ph in addition to the organometallic compound [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄]. [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BPh₄]₂ is generated after the reaction of compound [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂ with Na[BPh₄]. The structure of this compound was confirmed by X-ray diffraction. A possible approach to form Ph–C≡C–C₉H₈–Ph and [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄] is suggested. Graphical Abstract  Formal [2 + 2 + 2] addition reaction of [Cp*Ru(H₂O)(NBD)]BF₄ (NBD = norbornadiene) with 4,4′-Diethynylbiphenyl generates [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂. The reaction of [Cp*Ru(H₂O)(NBD)][BF₄] with 1,4-diphenylbutadiyne simply generates unusual [2 + 2 + 2] additional organic compound Ph–C≡C–C₉H₈–Ph in addition to the organometallic compound [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄]. [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BPh₄]₂ is generated after the reaction of compound [C₉H₉-η⁶-C₆H₄(RuCp*)–C₆H₄(RuCp*)-η⁶-C₉H₉][BF₄]₂ with Na[BPh₄]. The structure of this compound was confirmed by X-ray diffraction. And the possible approach to form Ph–C≡C–C₉H₈–Ph and [Cp*Ru(η⁶-C₆H₅–C≡C–C≡C–Ph)][BF₄] was suggested. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Aminomethyl Transfer (Mannich) Reactions Between an O-Triethylsilylated Hemiaminal and Anilines,RnC6H5−nNH2 Leading to New Diamines,Triamines, Imines,or 1,3,5-Triazines Dependent upon Substituent R

The reactions of the Mannich reagent Et₃SiOCH₂NMe₂ ( 1 ) with a variety of anilines (mono-substituted RC₆H₄NH₂, R=H, 4-CN, 4-NO₂, 4-Ph, 4-Me, 4-MeO, 4-Me₂N; di-substituted R₂C₆H₃NH₂, R₂=3,5-(CH₃)₂, 3,5-(CF₃)₂; tri-substituted R₃C₆H₂NH₂, R₃=3,5-Me₂-4-Br and a “super bulky” aniline (Ar*NH₂) [Ar*=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC₆H₄NH(CH₂NMe₂) [R=CN ( 2 a ), NO₂ ( 2 b )] and R₂C₆H₃NH(CH₂NMe₂) [R₂=3,5-(CF₃)₂ ( 2 c) ] were formed. Further reaction of 2 a , b , c with 1 yielded the corresponding triamines RC₆H₄N(CH₂NMe₂)₂ (R=CN ( 3 a ), NO₂ ( 3 b ) and R₂C₆H₃N(CH₂NMe₂)₂, R₂=3,5-(CF₃)₂ ( 3 c ). The new polyamines were characterized by NMR spectroscopy, and for 2 a , 2 c _, and 3 c , by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe₂, 4-Me, 3,5-Me₂, 3,5-Me₂-4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO ( 5 a ), 4-Me₂N ( 5 b ), 4-Me ( 5 c ), 3,5-Me₂ ( 5 d ), 3,5-Me₂-4-Br ( 5 e ), 4-Ph ( 5 f ), 4-Cl ( 5 g ). The “super bulky” aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH₂ ( 4 ) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of “Silick” chemistry.     

The Effect of Electron-Donating and Electron-Withdrawing Substituents on 1H-and 13C-NMR chemical shifts of novel 7′-aryl-substituted 7′-apo-β-carotenes

The synthesis of 7′-aryl-7′-apo-β-carotenes, where aryl (Ar) is Ph, 4-NO₂C₆H₄, 4-MeOC₆H₄, 4-(MeO₂C)C₆H₄, C₆F₅, and 2,4,6-Me₃C₆H₂, is described. NMR Chemical shifts of all H- and C-atoms are presented, together with specific examples of the spectra. In contrast to ¹H chemical shifts which, except for H? C(8′) and H? C(7′), did not differ greatly from those of β,β-carotene, considerable variations in ¹³C chemical shifts were observed. Signals of the C(α) atoms of the polyene chain [C(β)? C(α)] +_n Ar were shielded, those of the C(β) atoms were deshielded, with some exceptions when n = 1; the effects decreased with increasing n.     

Micron‐granula polyolefin with self‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups

Self‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArN?C]₂(C₁₀H₆)NiBr₂ [Ar = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₂] ( 1 ), [ArN?C(Me)][Ar′N? C(Me)]C₅H₃NFeCl₂ [Ar = Ar′ = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₃, Ar = 2,6‐(i‐Pr)₂C₆H₃, and Ar′ = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₃] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArN?C]₂C₁₀H₆NiBr₂ (Ar = 2,6‐(i‐Pr)₂C₆H₂)], but also greatly improved the morphology of polymer particles to afford micron‐granula polyolefin. The self‐immobilization of catalysts, the formation mechanism of microspherical polymer, and the influence on the size of the particles are discussed. The molecular structure of self‐immobilized nickel catalyst 1 was also characterized by crystallographic analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1018–1024, 2004     

Reactions of transition metal acetylides: VI. Some addition reactions of substituted styrenes with Ru(C2R)(L)2(η-C5H5) (R = Me OR Ph; L2 = (CO,PPh3), (PPh3)2 OR (dppe)). X-ray crystal structure of Ru{C[C(CN)2]CPhCH(C6H4NO2-4)}(dppe)(η-C5H5) · 0.5CH2Cl2

Further studies of the reactions between ruthenium σ-acetylide complexes and electrophilic olefins CHArC(CN)(X) (Ar = C₆H₄NO₂-4, Ph; X = CN; Ar = C₆H₄NO₂-4, X = CO₂Et) have shown the formation of allylic, butadienyl, and in one case, cyclobutenyl complexes. The direction of addition is such that the =C(CN)(X) group becomes attached to the α-carbon of the acetylide. This is confirmed by the X-ray structure of Ru{C[C(CN)₂]CPhCH(C₆H₄NO₂-4)}(dppe)(η-C₅H₅) · 0.5CH₂Cl₂, cr with cell dimensions a 28.81(1), b 9.661(2), c 30.782(8) Å, β 95.02 (3)°, and Z = 8. The structure was refined by a least-squares procedure with the use of 4291 statistically significant reflections [I > 2.5σ(I)] to R 0.075 and R_w 0.076.     

Reactions of nucleophilic addition of primary amines to the nitrilium derivative of the <Emphasis Type="Italic">closo</Emphasis>-decaborate anion [2-B<Subscript>10</Subscript>H<Subscript>9</Subscript>(N≡CCH<Subscript>3</Subscript>)]<Superscript>−</Superscript>

Compounds (Bu₄N)[2-B₁₀H₉{NH=C(NHR)CH₃}]⁻ are obtained by reactions of the tetrabutylammonium salt of the [2-B₁₀H₉(N≡CCH₃)]⁻ anion with aliphatic and aromatic primary amines RNH₂ (R = n-C₃H₇, n-C₄H₉, cyclo-C₅H₉, C₆H₅, cyclo-C₆H₁₁, n-C₆H₁₃, C₇H₇, C₈H₈NH₂, C₆H₄NO₂, and C₁₈H₃₇) and identified by IR, ESI/MS, and NMR (¹H, ¹¹B, and ¹³C) spectroscopy. The structures of the amidine-type derivatives [2-B₁₀H₉{Z-NH=C(NH-cyclo-C₅H₉)CH₃}]⁻ and [2-B₁₀H₉{Z-NH=C(NH-C₇H₇)CH₃}]⁻ are determined by X-ray diffraction.     

N-aryl-and N-vinyldiaza-18-crown-6: Synthesis and complexing ability

The nucleophilic aromatic and vinyl substitution using diaza-18-crown-6 as nucleophile afforded a number of its N,N’-diaryl-[aryl = 2,4-(NO₂)₂C₆H₃, 4-C₅F₄N, 4-CF₃C₆F₄] and N,N’-dialkenyl-substituted derivatives [alkenyl = PhC(O)CH=CH, MeOCOCH=CH, (EtO₂C)₂C=C(Ph), etc.]. Arylation of diaza-18-crown-6 with nonactivated aryl bromides, such as 4-Me₂NC₆H₄Br, 4-MeOC₆H₄Br, C₆H₅Br, and 4-CF₃C₆H₄Br, was effected under catalysis by palladium complexes. N,N’-Diaryldiaza-18-crowns-6 having electron-acceptor substituents in the aromatic rings turned out to be incapable of forming complexes with metal cations, while their analogs containing electron-donor para-methoxy and para-dimethylamino groups gave complexes with barium perchlorate.     

The solid state structure of arene-mercury(II) complexes from magic-angle spinning carbon-13 NMR and the solution carbon-13 NMR of some complexes of mercury(II) with arenes having bulky aliphatic substituents

The cross-polarization magic angle spinning ¹³C NMR spectra of Hg(SbF₆)₂ - 2 Arene (Arene = C₆HMe₅, 1,2,4,5-C₆H₂Me₄, 1,2,3,4-C₆H₂Me₄, or C₆H₆) have been measured. The spectra of the complexes of C₆HMe₅ and 1,2,4,5-C₆H₂Me₄ are consistent with static η¹-bonding of the mercury to the arene at an unsubstituted carbon atom, while the spectra of the 1,2,3,4-C₆H₂Me₄ and C₆H₆ complexes show the arene to have time-averaged C_s or C₂, and C₆ symmetry respectively, at the temperature of measurement (300 K).The reduced temperature ¹³C NMR spectra of Hg(Arene)_n²⁺ (n = 1 or 2; Arene = 1,3,5-C₆H₃R₃ (R = Me, i-Pr, or t-Bu)) in SO₂ solution are also reported and affirm that in these intramolecularly mobile species the mercury bonds in an η¹-manner, with unsubstituted aryl carbon atoms being the strongly preferred point of mercury attachment. This site preference is further demonstrated by the solution ¹³C NMR spectra of Hg(Arene)_n²⁺ (Arene = 1,2,3,4-C₆H₂-Me₄, n = 1 or 2; Arene = 1,4-C₆H₄R₂, R = Me or t-Bu, n = 1). The spectra of the 1,4-C₆H₄R₂ complexes and Hg(p-C₆H₄-t-BuMe)²⁺ provide clear evidence for steric influence of the binding site.Like Hg(C₆Me₆)₂²⁺, but unlike most of the complexes of substituted benzenes which have been studied, Hg(1,3,5-C₆H₃-i-Pr₃)₂²⁺ exchanges only slowly with excess free ligand.     

The Synthesis of Functionalised Diaryltetraynes and Their Transport Properties in Single‐Molecule Junctions

The synthesis and characterisation is described of six diaryltetrayne derivatives [Ar‐(C?C)₄‐Ar] with Ar=4‐NO₂‐C₆H₄‐ ( NO₂4 ), 4‐NH(Me)C₆H₄‐ ( NHMe4 ), 4‐NMe₂C₆H₄‐ ( NMe₂4 ), 4‐NH₂‐(2,6‐dimethyl)C₆H₄‐ ( DMeNH₂4 ), 5‐indolyl ( IN4 ) and 5‐benzothienyl ( BTh4 ). X‐ray molecular structures are reported for NO₂4 , NHMe4 , DMeNH₂4 , IN4 and BTh4 . The stability of the tetraynes has been assessed under ambient laboratory conditions (20 °C, daylight and in air): NO₂4 and BTh4 are stable for at least six months without observable decomposition, whereas NHMe4 , NMe₂4 , DMeNH₂4 and IN4 decompose within a few hours or days. The derivative DMeNH₂4 , with ortho‐methyl groups partially shielding the tetrayne backbone, is considerably more stable than the parent compound with Ar=4‐NH₂C₆H₄ ( NH₂4 ). The ability of the stable tetraynes to anchor in Au|molecule|Au junctions is reported. Scanning‐tunnelling‐microscopy break junction (STM‐BJ) and mechanically controllable break junction (MCBJ) techniques are employed to investigate single‐molecule conductance characteristics.     

Lipase-catalyzed dynamic kinetic resolution giving optically active cyanohydrins: use of silica-supported ammonium hydroxide and porous ceramic-immobilized lipase

Synthetically useful cyanohydrin acetates, ArCH(OAc)CN (Ar=C₆H₅, 3,4-methylenedioxyphenyl, 4-Me-C₆H₄, 4-Cl-C₆H₄, 4-F-C₆H₄, 4-CF₃-C₆H₄), were successfully synthesized in high enantiomeric purities (79-93% ee) via the lipase-catalyzed dynamic kinetic resolution (DKR) of cyanohydrins synthesized in situ from the corresponding aldehydes and acetone cyanohydrin. The combined use of silica-supported BTAH (benzyltrimethylammonium hydroxide) and porous ceramic-immobilized lipase under the optimized reaction conditions enabled the remarkable acceleration of the enantioselective DKR reactions.     

Microwave-assisted Stille and Hiyama cross-coupling reactions catalyzed by ortho-palladated complexes of homoveratrylamine

The activity of dimeric [Pd{C₆H₂(CH₂CH₂NH₂)-(OMe)₂-3,4}(μ-Br)]₂ and monomeric [Pd{C₆H₂(CH₂CH₂NH₂)-(OMe)₂-3,4}Br(PPh₃)] complexes as efficient, air, and moisture tolerant catalysts was investigated in Stille and Hiyama cross-coupling reactions of various aryl halides. Substituted biaryls were produced in excellent yields in short reaction times using these complexes. The monomeric complex had been demonstrated to be more active than the corresponding dimeric catalyst for the cross-coupling of some of aryl bromides and unreactive aryl chlorides. The combination of homogenous metal catalyst, microwave irradiation, and microwave-active polar solvents gave high yields of products in short reaction times.     

Tunable Fluorophores Based on 2‐(N‐Arylimino)pyrrolyl Chelates of Diphenylboron: Synthesis,Structure, Photophysical Characterization,and Application in OLEDs

Reactions of 2‐(N‐arylimino)pyrroles (HNC₄H₃C(H)?N‐Ar) with triphenylboron (BPh₃) in boiling toluene afford the respective highly emissive N,N′‐boron chelate complexes, [BPh₂{κ²N,N′‐NC₄H₃C(H)?N‐Ar}] (Ar=C₆H₅ ( 12 ), 2,6‐Me₂‐C₆H₃ ( 13 ), 2,6‐iPr₂‐C₆H₃ ( 14 ), 4‐OMe‐C₆H₄ ( 15 ), 3,4‐Me₂‐C₆H₃ ( 16 ), 4‐F‐C₆H₄ ( 17 ), 4‐NO₂‐C₆H₄ ( 18 ), 4‐CN‐C₆H₄ ( 19 ), 3,4,5‐F₃‐C₆H₂ ( 20 ), and C₆F₅ ( 21 )) in moderate to high yields. The photophysical properties of these new boron complexes largely depend on the substituents present on the aryl rings of their N‐arylimino moieties. The complexes bearing electron‐withdrawing aniline substituents 17 – 20 show more intense (e.g., ?_f=0.71 for Ar=4‐CN‐C₆H₄ ( 19 ) in THF), higher‐energy (blue) fluorescent emission compared to those bearing electron‐donating substituents, for which the emission is redshifted at the expense of lower quantum yields (?_f=0.13 and 0.14 for Ar=4‐OMe‐C₆H₄ ( 15 ) and 3,4‐Me₂‐C₆H₃ ( 16 ), respectively, in THF). The presence of substituents bulkier than a hydrogen atom at the 2,6‐positions of the aryl groups strongly restricts rotation of this moiety towards coplanarity with the iminopyrrolyl ligand framework, inducing a shift in the emission to the violet region (λ_max=410–465 nm) and a significant decrease in quantum yield (?_f=0.005, 0.023, and 0.20 for Ar=2,6‐Me₂‐C₆H₃ ( 13 ), 2,6‐iPr₂‐C₆H₃ ( 14 ), and C₆F₅ ( 21 ), respectively, in THF), even when electron‐withdrawing groups are also present. Density functional theory (DFT) and time‐dependent DFT (TD‐DFT) calculations have indicated that the excited singlet state has a planar aryliminopyrrolyl ligand, except when prevented by steric hindrance (ortho substituents). Calculated absorption maxima reproduce the experimental values, but the error is higher for the emission wavelengths. Organic light‐emitting diodes (OLEDs) have been fabricated with the new boron complexes, with luminances of the order of 3000 cd m^?2 being achieved for a green‐emitting device.