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Abstract: Neutral tridentate O,N,L-type ligands aeimp-H, quimp-H and ppimp-H (aeimp-H = 2-((dimethylamino)ethylimino)methyl)-4,6-di-tert-butyl-phenol; quimp-H = 2-((quinolin-8-ylimino)methyl)-4,6-di-tert-butyl-phenol; ppimp-H = 2-((2-phenoxyphenylimino)methyl)-4,6-di-tert-butylphenol) readily reacted with AlMe2Cl to afford the corresponding methyl-chloro aluminium derivatives (aeimp)AlMeCl (2a) (quimp)AlMeCl (2b) and (ppimp)AlMeCl (2c) with concomitant elimination of methane. DFT calculations suggested that the pendant donor arm in these species is weakly bounded to the metal centre. A fast chloride abstraction by Me2AlCl from the neutral derivatives 2a and 2b produced the tetrahedral cationic species (η3-O,N,L)AlMe+ counterbalanced by the Me2AlCl2 - anion. Analogously direct treatment of bpzmp-H (bpzmp-H = 2,4-di-tert-butyl-6-(bis(3,5-dimethylpyrazol-1yl)methyl)phenol) with two equivalents of Me2AlCl afforded the Al cation [(bpzmp)AlMe][Me2AlCl2] (3d) as determined by single crystal X-ray analysis. [Copyright &y& Elsevier]

Cat power: Judicious backbone substitution of N‐heterocyclic carbenes (NHCs) leads to stable Ru metathesis catalysts with frozen NHC conformations. This finding not only permits the isolation of complexes that are among the most active catalysts in the ring‐closing metathesis of hindered olefins (see graphic; Ts=p‐toluenesulfonyl), but also provides fundamental mechanistic insights on the role of N‐aryl substituent conformations on catalyst activity. [ABSTRACT FROM AUTHOR]

The crystal structures of five β-enaminones are reported: (2 Z)-3-(benzylamino)-1,3-diphenyl-prop-2-en-1-one, (2 Z)-3-(benz­yl­amino)-3-(2-hydroxyphenyl)-1-phenyl-prop-2-en-1-one, (2 Z)-3-(benzylamino)-3-(4-methoxyphenyl)-1-(3-nitrophen­yl)-prop-2-en-1-one, 2-{1-[(4-methoxyphenyl)amino]ethylidene}cyclohexene-1,3-dione and 2-{1-[(3-methoxyphenyl)amino]­ethylidene}cyclohexene-1,3-dione. The structures were analysed and compared with those of similar compounds in order to establish which factors determine the range (2.53–2.72 Å) of N⋯O hydrogen-bond distances in intramolecularly hydrogen-bonded β-enaminones. It has been shown that, beyond electronic resonance-assisted hydrogen-bond effects modulated by substituents, the necessary requirements to produce very short N—H⋯O hydrogen bonding are steric intramolecular repulsions, including the embedding of an enaminonic C—C or C—N bond in an aliphatic six-membered ring. By considering the structural features it is possible to expect the strength of N—H⋯O hydrogen bonds adopted by specific β-enaminones. [ABSTRACT FROM AUTHOR]

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Phenyl-substituted 1 -arylazo-2-naphthols (AAN) display ...HN-N=C-C=O… ⇌ ...N=N-C=C-OH… ketohydrazone-azoenol tautomerism and can form intramolecular resonance-assisted H-bonds from pure N-H…O to pure N…H-O through tautomeric and dynamically disordered N-H…O ⇌ N…H-O bonds according to the electronic properties of their substituents. Three compounds of this series (m-OCH3-AAN = mOM; p-Cl-AAN = pCI; and p-NMe2-AAN = pNM2) have been studied by X-ray crystallography at four temperatures (100-295 K), showing that the remarkably short H-bonds formed (2.53 ⩽ d(N...O) ⩽ 2.55 Å) are a pure N-H…O in mOM, a dynamically disordered mixture in pCI (N-H…O:N…H-O = 69:31 at 100 K), and a statically disordered mixture in pNM2 (N-H…O:N…H-O = 21:79 at 100 K). These compounds, integrated by the p-H-, p-NO2-, p-F-, and p-O--substituted derivatives, have been emulated by OFT methods (B3LYP/6-31 +G(d,p) level) with full geometry optimization of the stationary points along the proton-transfer (PT) pathway: N-H…O and N…H-O ground states and N…H…O transition state. Analysis of DFT-calculated energies and geometries by the methods of the rate- equilibrium Marcus theory shows that all H-bond features (stability and tautomerism, as well as position and height of the PT barrier) can be coherently interpreted in the frame of the transition-state (or activated- complex) theory by considering the bond as a chemical reaction N-H…O ⇌ N…H…O ⇌ N…H-O which is bimolecular in both directions and proceeds via the N…H…O PT transition state (the activated complex). [ABSTRACT FROM AUTHOR]

Reactions of Zeise’s salt (K[Pt(η2-C2H4)Cl3]) with oxidized phenanthroline ligands (1,10-phenanthroline-5,6-dione, phedon, and 2,9-dimethyl-1,10-phenanthroline-5,6-dione, Me2phedon) are reported. Comparison with analogous reactions involving unoxidized phen (1,10-phenanthroline) and Me2phen (2,9-dimethyl-1,10-phenanthroline) ligands indicates that these latter ligands are less capable to stabilize the five-coordinate species [PtCl2(η2-C2H4)(phenanthroline)] in which the phenanthroline and the olefin share the trigonal plane and two chlorines are in the axial positions. The X-ray structure of the four-coordinate species [PtCl2(Me2phedon)] indicates that the major difference between oxidized and unoxidized phenanthrolines is the loss of aromaticity of the central ring of phenanthroline. As a consequence, the oxidized phenanthroline becomes more flexible and can undergo a bow-like distortion so to reduce steric interaction between ortho substituents of phenanthroline and cis chlorine ligands. The increase in stability of the four-coordinate species with Me2phedon is concomitant with an increase in stability of the five-coordinate precursor complex with ethylene. In the latter case the stabilization is not of sterical origin but stems from reduced electron-donor properties of oxidized phenanthrolines. The balance of the two effects is such that the equilibrium between five- and four-coordinate species is more shifted in favour of the former species in the case of Me2phedon than in the case of Me2phen. [Copyright &y& Elsevier]

We have synthesized and fully characterized by NMR, IR and elemental analysis sixteen Pt(0) derivatives stabilized by four different thioquinoline spectator ligands and four different deactivated olefins. Moreover we have studied the reactivity and proposed a mechanism for olefin-olefin, olefin-alkyne exchange and oxidative addition of alkyl halides to this new class of Pt(0) derivatives based on detailed kinetic measurements. The kinetic study was carried out by NMR and UV–Vis techniques and in one case we have determined the activation parameters. Finally, we were able to resolve the solid state structure of a couple of diastereoisomers among the four possible isomers generated by the combination of two stereocenters. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis of gold(I) derivatives with carbene, phosphine and isocyanide as spectator ligands. [•] Transmetalation between gold(I) derivatives and tributyl-phenylethynylstannane. [•] Kinetic study on the transmetalation reaction carried out in CHCl3 and CH3CN. [Copyright &y& Elsevier]

Abstract: The reactions of PTA (1,3,5-triaza 7-phosphaadamantane) and HMTA (1,3,5,7-tetraazaadamantane) with 1,3-propanesultone or 1,4-butanesultone gave the water soluble zwitterionic derivatives PTA+C3H6SO3 − (1), PTA+C4H8SO3 − (2), HMTA+C3H6SO3 − (3) and HMTA+C4H8SO3 − (4). The crystal structure of HMTA+C3H6SO3 is reported. The coordinative ability of 1–4 towards Pt(II) and Ru(II) has been investigated and the antiproliferative activity of ligands and complexes has been tested in two human ovarian cancer cell lines, A2780 and SKOV3. [Copyright &y& Elsevier]

Abstract: The reaction between an equimolecular mixture of isocyanide CNR (CNR=di-methylphenyl isocyanide (DIC), tert-butyl isocyanide (TIC), triphenyl phosphane (PPh3) and a dechlorinated solution of the palladium allyl dimers [Pd(η3-allyl)Cl]2 (allyl=2-Meallyl, 1,1-Me2allyl) in stoichiometric ratio yields the mixed derivative [Pd(η3-allyl)(CNR)(PPh3)] only. Apparently, the mixed derivative represents the most stable species among all the possible ones that might be formed under those experimental conditions. Theoretical calculations are in agreement with the experimental observation and the energy stabilization of the mixed species with respect to the homoleptic derivatives is traced back to an overall push–pull effect exerted by the isocyanide and the phosphane acting synergically. Similar behavior is observed in the case of the synthesis of the palladacyclopentadienyl complexes [Pd(C4(COOMe)4)(CNR)(PPh3)] and of the palladium(0) olefin complexes whose synthesis invariably yields the mixed [Pd(η2-olefin)(CNR)(PPh3)] derivatives. The paper includes studies on the reactivity toward allylamination in the case of the palladium(II) allyl complexes. A diffractometric investigation on the solid state structures of four different palladium isocyanide–phosphane complexes is also included. [Copyright &y& Elsevier]

Abstract: Pt(II) and Pd(II) methyl- and chloro-complexes with the tridentate N-donor ligands ((pyridin-2-yl)methylene)quinolin-8-amine (NNPy), ((pyridin-2-yl)ethylidene)quinolin-8-yl-amine (NNMePy), (phenyl(pyridin-2-yl)methylene)quinolin-8-yl-amine (NNPhPy), ((thiazol-2-yl)methylene)quinolin-8-amine (NNTh) and ((imidazol-4-yl)methylene)quinolin-8-amine (NNImH) were prepared by metal-assisted condensation of 8-aminoquinoline and an ortho-substituted aldehydo- or keto- N-heterocycle. Preliminary reactivity studies involving the coordinated tridentate N-donors, the chloro-ligand and the M-CH3 bond were carried out, leading to the synthesis of several new complexes. During these studies, the formation of a novel five-coordinate Pt(II) carbonyl-complex was observed. [Copyright &y& Elsevier]

[Cu2(μ4-O)Cu2] and [Cu2(μ1,1-N3)4Cu2] geometrical arrangements are found in a new family of tetranuclear copper(II) complexes: [Cu4(μ4-O)(μ-cip)2Cl4] (1), [Cu4(μ4-O)(μ-cip)2(μ1,3-O2CPh)4]·2CH3OH (2·2CH3OH), and [Cu4(μ1,1-N3)4(μ-cip)2(N3)2]·DMF (3·DMF) [Hcip = 2,6-bis(cyclohexyliminomethylene)-4-methylphenol; CH3OH = methanol; DMF = dimethylformamide]. These complexes have been characterized by X-ray crystallography, and their magnetic properties have been studied. 1 and 2 form quasi-tetrahedral [Cu4(μ4-O)] complexes, and 3 is the first example of a rhomboidal [Cu4(μ1,1-N3)] compound. Formation of the [Cu4] compounds is achieved via ligand-exchange reactions. The relative binding strength of the three ancillary ligands as N3- > PhCO2- > Cl- has been demonstrated from the core-conversion and peripheral ligand-exchange reactions. For the three complexes, the magnetic susceptibility measurements in the range of 1.8-300 K have been performed and modeled using two isolated S = 1/2 dimers based on the spin Hamiltonian H = -2J{SCu,1·SCu,2} with J/kB = -513, -340, and -315 K for 1-3, respectively (where J is the exchange constant through the oxido-phenoxido and azido-phenoxido bridges, respectively). [ABSTRACT FROM AUTHOR]

Abstract: The reaction of substituted β-enaminoamides with 4-methylbenzenediazonium tetraphenylborate in dichloromethane produces besides the primary products of azo coupling reaction at the α-carbon atom of β-enaminoamides, also mixtures of heterocyclic compounds of boron: 1,3,2λ4-oxazaborines, 1H-1,3,2λ4-diazaborine-4-ones and 4H-1,2,4,3λ4-triazaborines. Proportions of the products change depending on the reaction conditions, particularly depending on the presence or absence of base (sodium acetate) in the reaction mixture. The heterocyclic compounds were separated chromatographically and identified by means of X-ray, 1H, 11B, 13C and 15N NMR spectra and elemental analyses. [Copyright &y& Elsevier]

Abstract: New complexes LTiCl3(1), LZrCl3(2) and LHfCl3(3) (L=(E)-2-tert-butyl-6[(quinoline-8-ylimino)methyl]phenolate) have been synthesized and fully characterized by multinuclear NMR, mass spectrometry and X-ray diffractometry. The three isostructural complexes show distorted octahedral geometries. Complexes 1–3 were tested as catalysts for ethylene polymerization under a variety of experimental conditions. Reasonable productivities were achieved after activation by methylaluminoxane (MAO) under moderate temperature and pressure conditions (e.g., 50°C and 6atm). Complexes 1–3 were also tested as precatalysts for the polymerization of propene. Interestingly, polymerization by 1-MAO at −20°C afforded an isotactic polypropylene containing 5% isolated regioirregular units in threo configuration. This very unusual microstructure implicates that both primary and secondary monomer insertions occur with the same enantioface selectivity, at variance with what is observed in the case of metallocene catalysts. [Copyright &y& Elsevier]

The synthesis and chemical reactivity of pyridazinedione-based enediynes (1, 2) are described. Both of these enediynes, namely the dihydro compound 1 and its corresponding tetrahydro analogue 2, were prepared by double N,O-alkylation of the corresponding heterocyclic system with the acyclic enediynyl dibromide 8 in good yields. Their single-crystal X-ray structures revealed similar c, d distances (distance between the acetylenic carbons undergoing covalent connection in Bergman cyclization). Interestingly, these molecules undergo Bergman cyclization at different rates, and the reactivity is shown to be dependent upon the state of hybridization of C-4 and C-5 atoms of the parent heterocyclic ring. [ABSTRACT FROM AUTHOR]