The contradictory effect of the methoxy-substituent in palladium-catalyzed ethylene/methyl acrylate cooligomerization.

Two new nonsymmetric bis(aryl-imino)acenaphthene ligands (Ar,Ar'-BIAN) and one symmetric Ar2-BIAN were studied. The three ligands share the presence of at least one methoxy group on one of the two aryl rings. These ligands were used for the synthesis of neutral and monocationic palladium(ii) complexes of general formula [Pd(CH3)Cl(N-N)] and [Pd(CH3)(L)(N-N)][PF6] (N-N = Ar,Ar'-BIAN, Ar2-BIAN; L = CH3CN, dmso). Due to the nonsymmetric nature of the ligands and their coordination to palladium in a nonsymmetric chemical environment, cis and trans isomers are possible for the three series of complexes with Ar,Ar'-BIANs. Both a detailed NMR investigation in solution and the X-ray characterization in the solid state point out that the trans isomer is the preferred species for the neutral derivatives, whereas for the cationic compounds a decrease in the stereoselectivity of the coordination is observed. One of the new Ar,Ar'-BIANs differs from an already reported nonsymmetric α-diimine for the replacement, on one aryl ring, of a methyl group with a methoxy substituent, thus allowing a comparison of the structural features of the relevant complexes. The monocationic complexes were tested as precatalysts for the ethylene/methyl acrylate copolymerization under mild reaction conditions. Despite the structural similarities observed in solution with the already known precatalysts, the present compounds demonstrated a remarkable decrease in the productivity values associated with a higher affinity for the polar monomer.

Crystal structure of S-hexyl (E)-3-(2-hy-droxy-benzyl-idene)di-thio-carbazate.

The title compound, C14H20N2OS2 [systematic name: S-hexyl (E)-2-(2-hy-droxy-benzyl-idene)hydrazine-1-carbodi-thio-ate], crystallizes with four independent mol-ecules (A-D) in the asymmetric unit. All four mol-ecules adopt an E conformation with respect to the C=N bond of the benzyl-idene moiety and have an intra-molecular O-H⋯N hydrogen bond generating an S(6) ring motif. In the crystal, the A and D mol-ecules are connected by a pair N-H⋯S hydrogen bonds, forming a dimer with an R 2 (2)(8) ring motif. In the case of mol-ecules B and C, they are linked to themselves by pairs of N-H⋯S hydrogen bonds, forming B-B and C-C inversion dimers with R 2 (2)(8) ring motifs.

Crystal structure of 1,2-bis-((benzyl-sulfan-yl){2-[1-(2-hy-droxy-phen-yl)ethyl-idene]hydrazin-1-yl-idene}meth-yl)disulfane.

The title compound, C32H30N4O2S4, consists of two Schiff base moieties, namely two S-benzyl-ß-N-(2-hy-droxy-phenyl-ethyl-idene)di-thio-carbazate groups, which are connected through an S-S single bond. These two moieties are twisted with respect to each other, with a dihedral angle of 87.88 (4)° between the S2C=N planes. A bifurcated intra-molecular O-H⋯(N,S) hydrogen bond is observed in each moiety. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds into inversion dimers. The dimers are further stacked in a column along the b axis through weak C-H⋯π inter-actions.

Crystal structure of S-octyl (E)-3-(4-meth-oxy-benzyl-idene)di-thio-carbazate.

As already observed in similar mol-ecules, the di-thio-carbazate group in the title compound, C17H26N2OS2, adopts an EE configuration with respect to the C=N bond of the benzyl-idene moiety. In the crystal, mol-ecules are connected into inversion dimers by pairs of N-H⋯S hydrogen bonds. The dimers are linked by weak π-π inter-actions, with centroid-to-centroid distances of 3.723 (11) Å, forming chains parallel to [110].

Crystal structure of bis-{S-hexyl 3-[4-(di-methyl-amino)-benzyl-idene]di-thio-carbazato-κ(2) N (3),S}copper(II).

In the title complex, [Cu(C16H24N3S2)2], the Cu(II) atom is coordinated by two azomethine N and two thiol-ate S atoms of the chelating Schiff base ligands, resulting in a distorted square-planar coordination environment. The S-Cu-N chelating angle is of 84.41 (5)°. The Cu(II) atom is located on a crystallographic inversion centre, leading to a trans configuration of the N,S-chelating ligands.

Crystal structure of bis-[S-hexyl 3-(4-methyl-benzyl-idene)di-thio-carbazato-κ(2) N (3),S]nickel(II).

In the title complex, [Ni(C15H21N2S2)2], the Ni(II) atom exhibits a square-planar coordination geometry and is located on an inversion centre leading to a trans configuration of the N,S-chelating ligands. In the crystal, the complex mol-ecules stack at a distance of 4.6738 (3) Šalong the a axis, which exclude any significant inter-actions between the aromatic rings.

Crystal structure of S-hexyl (E)-3-(4-methyl-benzyl-idene)di-thio-carbazate.

In the title compound, C15H22N2S2, the di-thio-carbazate group adopts an E conformation with respect to the C=N bond of the benzyl-idene moiety. In the crystal, mol-ecules are linked by pairs of N-H⋯S hydrogen bonds, forming inversion dimers with an R (2) 2(8) ring motif. The dimers are linked via C-H⋯π inter-actions, forming chains propagating along [100].

Crystal structure of S-hexyl (E)-3-(4-methoxy-benzyl-idene)di-thio-carbazate.

In the title compound, C15H22N2OS2, the di-thio-carbazate group adopts an EE conformation with respect to the C=N bond of the benzyl-idene moiety. The hexyl side chain adopts an extended conformation and the C-S-C-C torsion angle is -93.36 (13)°. In the crystal, inversion dimers linked by pairs of N-H⋯S hydrogen bonds generate R 2 (2)(8) loops.

Crystal structure of bis-[µ-S-hexyl 3-(2-oxido-benzyl-idene)di-thio-carbazato-κ(4) O,N (3),S:O]dicopper(II).

The title compound, [Cu2(C14H18N2OS2)2], is a binuclear copper(II) complex of an oxybenzyl-idenedi-thio-carbazate ligand. The ligand coordinates in a tridentate manner through N-, S- and O-donor atoms. Each O atom also bridges to a second Cu(II) ion to form the binuclear species. It has a central Cu2O2 rhomboid moiety and a metal-to-metal separation of 2.9923 (6) Å. In the crystal, the binuclear complexes stack along the a axis with all the hexyl chains located side-by-side, forming a hydro-phobic region. The complexes are linked via C-H⋯N hydrogen bonds, forming chains along the c-axis direction. One Cu(II) atom has the S atom of a symmetry-related complex located approximately in the apical position at 2.9740 (11) Å. This weak inter-action links the chains to form slabs parallel to the ac plane.

Bis[benzyl N'-(3-phenyl-prop-2-enyl-idene)dithio-carbazato-κ(2)N',S]mercury(II).

In the title compound, [Hg(C(17)H(15)N(2)S(2))(2)], the Hg(II) ion lies on a crystallographic twofold rotation axis giving a very distorted tetra-hedral coordination geometry best described as bis-phenoidal, being chelated by two deprotonated N,S Schiff base ligands through the azomethine nitro-gen and the thiol-ate sulfur donors. The dihedral angle between the two chelating ligand moieties is 79.75 (10)°. In the crystal, weak C-H⋯S inter-actions give rise to chains extending along the c axis.

Bis[benzyl 3-(3-phenyl-prop-2-enyl-idene)dithio-carbazato-κ(2)N(3),S]cadmium.

In the title complex, [Cd(C(17)H(15)N(2)S(2))(2)], the Cd(II) ion is located on a twofold rotation axis and exhibits a coordination number of four within a very distorted coordination environment that is best described as bis-phenoidal. The two deprotonated Schiff base ligands chelate the Cd(II) ion through the azomethine N and the thiol-ate S atom. The dihedral angle between the two chelating ligands is 84.01 (9)°. Weak inter-molecular C-H⋯S inter-actions lead to the formation of chains along the c axis.

Bis[S-benzyl-3-(4-n-octyloxybenzylidene)dithiocarbazato-κ(2)N(3),S']palladium(II).

In the title compound, [Pd(C(23)H(29)N(2)OS(2))(2)], the Pd(II) atom displays the expected square-planar coordination geometry. However, the trans configuration, which allows the Pd(II) atom to be located on a crystallographic inversion centre, is unusual with respect to the cis arrangement found in analogous Pd complexes comprising similar N,S-chelating ligands.

2,4-Dimethoxy-benzaldehyde azine.

The title mol-ecule, C(18)H(20)N(2)O(4), is located on a crystallographic centre of symmetry. The meth-oxy groups are coplanar with the benzene ring [interplanar angles of 14.4 (2) and 3.1 (3)°], indicating a conjugation effect.

(E)-4-Octyloxybenzaldehyde thio-semicarbazone.

In the title compound, C(16)H(25)N(3)OS, the thio-semicarbazone group adopts an E configuration with respect to the C=N bond and is almost coplanar with the benzene ring, forming a dihedral angle of 9.3 (1)°. In the crystal packing, the mol-ecules lie along the a axis in an anti-parallel arrangement and are held in place by van der Waals inter-actions. As a consequence, there is relatively low anisotropic thermal motion in the terminal atoms of the n-octyl chain.

Syntheses, crystal structures, and magnetic properties of metal-organic hybrid materials of Cu(II): effect of a long chain dicarboxylate backbone, and counteranion in their structural diversity.

Eight new metal-organic hybrid materials of Cu(II) have been synthesized by using flexible glutarate/adipate as a bridging ligand, 2,2'-bipyridine/1,10-phenanthroline as a chelating ligand, and BF4-/ClO4-/Cl- as a counteranion. These materials are characterized by single-crystal X-ray diffraction analyses and variable temperature magnetic measurements. Out of them, complexes 1, 3, 5, and 8 crystallize in the triclinic system with space group P. Complexes 2, 4, 6, and 7 crystallize in the monoclinic system with space group P21/n (2, 4), P21/c (6), and C2 (7). The structural analysis reveals that bridging glutarate gives rise to dinuclear and tetranuclear species, whereas the adipate dianion leads to octanuclear, one-dimensional and two-dimensional polymeric complexes, although they have been prepared under similar conditions. Supramolecular architectures of higher dimensionality have been achieved through H-bonding and pi-pi interaction. In all the complexes, the bridging and/or counteranions as well as chelating ligand have a vital role in directing the solid-state structure. A variable temperature (2-300 K) magnetic susceptibility study discloses the antiferromagnetic coupling for all of the complexes.

Rare azido-bridged manganese(II) systems: syntheses, crystal structures, and magnetic properties.

Two new polymeric azido-bridged manganese complexes of formulas [Mn(N3)2 (bpee)]n (1) and {[Mn(N3)(dpyo)Cl(H2O)2](H2O)}n (2) [bpee, trans-1,2-bis(4-pyridyl)ethylene; dpyo, 4,4'-dipyridyl N,N'-dioxide] have been synthesized and characterized by single-crystal X-ray diffraction analysis and low-temperature magnetic study. Both the complexes 1 and 2 crystallize in the triclinic system, space group P1, with a = 8.877(3) A, b = 11.036(3) A, c = 11.584(4) A, alpha = 72.62(2) degrees, beta = 71.06(2) degrees, gamma = 87.98(3) degrees, and Z = 1 and a = 7.060(3) A, b = 10.345(3) A, c = 11.697(4) A, alpha = 106.86(2) degrees, beta = 113.33(2) degrees, gamma = 96.39(3) degrees, and Z = 2, respectively. Complex 1 exhibits a 2D structure of [-Mn(N3)2-]n chains, connected by bpee ligands, whose pyridine rings undergo pi-pi and C-H...pi interactions. This facilitates the rare arrangement of doubly bridged azide ligands with one end-on and two end-to-end (EO-EE-EE) sequence. Complex 2 is a neutral 1D polymer built up by [Mn(N3)(dpyo)Cl(H2O)2] units and lattice water molecules. The metals are connected by single EE azide ligands, which are arranged in a cis position to the Mn(II) center. The 1D zipped chains are linked by H-bonds involving lattice water molecules and show pi-pi stacking of dpyo pyridine rings to form a supramolecular 2D layered structure. The magnetic studies were performed in 2-300 K temperature range, and the data were fitted by considering an alternating chain of exchange interactions with S = 5/2 (considered as classical spin) with the spin Hamiltonians H = -Ji sigma(S(3i)S(3i+1) + S(3i+1)S(3i+2)) - J2 sigmaS(3i-1)S(3i) and H = -Ji sigmaS(2i)S(2i+1) - J2 sigmaS(2i+1)S(2i+2) for complexes 1 and 2, respectively. Complex 2 exhibits small antiferromagnetic coupling between the metal centers, whereas 1 exhibits a new case of topological ferromagnetism, which is very unusual.

Novel Unsymmetrical Ru(III) and Mixed-valence Ru(III)/Ru(II) Dinuclear Compounds Related to the Antimetastatic Ru(III) Drug NAMI-A.

In this paper we report the stepwise preparation and the characterization of new unsymmetrical monoanionic Ru(III) dinuclear compounds, [NH(4)][{trans-RuCl(4)(Me(2)SO-S)}(mu-L){mer-RuCl(3)(Me(2)SO-S)(Me(2)SO-O)}] (L = pyz (1), pym (2)). By a similar synthetic approach we also prepared new mixed-valence Ru(III)/Ru(II) dinuclear compounds of formula [NH(4)][{trans-RuCl(4)(Me(2)SO-S)}(mu-pyz){cis,cis,cis-RuCl(2)(Me(2)SO-S)(2)(CO)}] (L = pyrazine (pyz, 3), pyrimidine (pym, 4)). Moreover, we describe the chemical behavior of compounds 1-4 in physiological solution, also after complete reduction (with ascorbic acid) to the corresponding Ru(II)/Ru(II) species. Overall, the chemical behavior of 1 and 2 after reduction resembles that of the corresponding dianionic and neutral dinuclear species, [{trans-RuCl(3)(Me(2)SO-S)}(2)(mu-L)](2-)and [{mer-RuCl(3)(Me(2)SO-S)(Me(2)SO-O)}(2) (mu-L)]. On the other hand, the mixed-valence dinuclear compounds 3 and 4, owing to the great inertness of the cis,cis,cis-RuCl(2)(Me(2)SO-S)(2)(CO)(1/2mu-L) fragment, behave substantially like the mononuclear species [trans-RuCl(4)(Me(2)SO-S)(L)](-) in which the terminally bonded L ligand can be considered as bearing a bulky substituent on the other N atom.

Understanding the orientation and dynamic motion of planar heterocyclic N-donor ligands by exploiting the symmetry properties of mixed-ligand mu-oxorhenium(V) dinuclear complexes.

Factors influencing the orientation and dynamic motions of planar N-donor heterocyclic ligands (L) are of interest since such features have broad relevance in metallobiochemistry [Marzilli, L. G.; Marzilli, P. A.; Alessio, E. Pure Appl. Chem. 1998, 70, 961-968]. We found that mu-oxorhenium(V) dinuclear complexes [ReOCl2LsLt]-O-[ReOCl2LsLt] bearing either symmetrical (L = py = pyridine; 3,5-lut = 3,5-lutidine) or lopsided (L = Me3-Bzm = 1,5,6-trimethylbenzimidazole) cis L ligands are particularly useful for studying these factors. NMR data showed that terminal (Lt) and stacked (Ls) ligands were exchanged by approximately 180 degrees rotation about the Re-O-Re bond system. Such exchange occurred, however, between degenerate chiral conformers. Here we report a combined X-ray structural and solution NMR investigation of the AA + CC (racemic) and AC (meso) forms of two mixed-ligand mu-oxorhenium dimers that bear one lopsided and one symmetrical ligand on each Re atom, namely, Re2O3-Cl4(py)2(Me3Bzm)2 (1rac and 1meso) and Re2O3Cl4(3,5-lut)2(Me3Bzm)2 (2rac and 2meso). The presence of two different cis L ligands in 1 and 2 breaks the local symmetry at each Re atom, so that, in the racemic dimers, the exchange of terminal and stacked ligands leads to nondegenerate conformers. Overall, NMR data showed that the unsymmetrical dimers 1 and 2 undergo two dynamic processes contemporaneously, namely, 180 degrees rotation about the Re-N(py or 3,5-lut) bond and coupled rotation about the Re-O-Re/Re-N bonds. Both processes reach the slow exchange limit below -80 degrees C. Rotation of py in 1 occurs faster than that of 3,5-lut in 2; this difference is attributed to the higher steric demands of 3,5-lut compared to py. For both dimers NMR data provided compelling evidence of the preferred conformers in solution, including ligand orientations. The low-T solution structure of 1meso and 2meso is chiral, the same as that found in the solid state for 2meso, where the Me3Bzm on one Re atom is stacked with the 3,5-lut on the other Re atom. The remaining Me3Bzm and 3,5-lut, one on each Re atom, are both terminal. In solution the coupled Re-O-Re/Re-N rotations interconvert the two halves of each meso dimer to yield the same overall stable chiral conformation. For the racemic dimers, however, this process does not interconvert one enantiomer into the other, but instead interconverts two rotamers, R1 and R2, each of which is chiral. We found that, in the case of both 1rac and 2rac, the conformer with stacking symmetrical ligands (R1) is roughly 1 order of magnitude more stable than that with stacking Me3Bzm ligands (R2). Moreover, the solution conformation of R1 is the same as that found in the solid state of 1rac. Solution- and solid-state data indicate that the key interaction favoring the observed conformations is very likely the electrostatic attraction between the delta+ H2 atoms on the Me3Bzm ligands and the negative O and Cl groups in the core of the dimers. Finally, for both meso and racemic dimers we were also able to elucidate the preferred pathways of the coupled dynamic motions and establish that, very likely, the two halves of the dimers swing back and forth by approximately 130 degrees through the anti eclipsed form.