Studies on Nickel(II) Complexes. III. Bis-(N-arylsalicylaldimine) Complexes

Abstract

NICKEL COMPLEXES 599 served for the future. It should be noted that the associations of Ag+ and CN-are the strongest which have been measured in molten salt soh-tions. Values of -AAl for associations of Ag+ with various ions in molten nitrates are in the order CN-It has been found that upon alteration of the R substituent in bis-( R-N-salicyla1dimine)-nickel( 11) complexes from methyl or n-alkyl to certain aryl groups, large increases in the solution paramagnetism in inert solvents are produced. The factors affecting this surprising behavior were investigated in an extensive study of the R = aryl complexes. By variation of substituents and their positions on the aryl portion of the molecules, it was found that the spectral and magnetic properties and the extent of molecular association could be consistently controlled. On the basis of this behavior the complexes fall into three categories: (1) those with o-substituted aryl groups, which are diamagnetic and monomeric; (2) those with phenyl and @-substituted aryl complexes, which are strongly paramagnetic in solution (peff > 2.8 B.M.), associated (1.5 < 8 < 2.0), and are either diamagnetic or paramagnetic solids; (3) those with m-substituted aryl groups, which have in solution paff 2 3.2 B.M., 2 < fi < 3, and are always paramagnetic solids. For complexes of the second category the magnetic and molecular weight data a t 37" were interpreted in terms of a diamagnetic monomer-paramagnetic dimer equilibrium. The results present further substantiation of the relation between solution paramagnetism and molecular association of apparently quadricoordinate Ni(I1) complexes. The nature of the associated forms in no case could be deduced with certainty from the data ; however, the presence of axially perturbed trans-planar coordination units appears likely.

Characterization of WOx/CeO2 catalysts and their reactivity in the isomerization of hexane

“…Another possibility of generating such carbocations was suggested by Fȃrcaşiu et al [5] for the isomerization over sulfated zirconia catalysts. These catalysts, first reported by Holm and Bailey [6], were considered as superacid solids [7], but further studies infirmed this assumption [8,9]. Fȃrcaşiu et al [5] proposed an alternative mechanism consisting of a one-electron transfer from the substrate to the catalyst, followed by the cleavage of the radical cation.…”

Effect of Pt Incorporation into Ni/ZrO2–SO4=/Al2O3 Catalyst for n-Butane Isomerization

“…Incorporation of metallic species such as Pt, Ni, Sn, W or Fe to sulfate zirconia catalyst allows the improvement of the surface acidic properties rather than with the amorphous silica-alumina materials [6]. Metals which usually have hydrogenation/dehydrogenation functions may be used to stabilize the activity of anionmodified zirconia catalysts.…”

Spectral Investigation of the Activities of AminoSubstituted Bases

“…Schiff bases resulted from aromatic aldehydes ortho-substituted with a hydroxyl group have initially arouse the researchers' interest because of their ability to act as bidentate ligands for transitional metal ions [16][17][18][19][20]. Later, in studies concerning quantitative structure-antitumor activity relationship of a series of Schiff bases derived from variously substituted aromatic amines and aldehydes, it has been shown that azomethines from salicylaldehydes gave the best correlation [21,22].…”