Two structurally related bis(imidoylamidine or 1,3,5‐triazapentadiene)nickel(II) compounds {Ni[HN=C(3‐py)NC(3‐py)=NH]2}·H2O·MeOH (1) and [Ni{HN=C(3‐py)N(H)C(3‐py)=NH}2]Cl2 (2) with symmetrical 3‐pyridyl (3‐py) substituents have been prepared by direct 2‐butanone oxime mediated transformation of 3‐cyanopyridine in the presence of Ni(MeCO2)2·4H2O or NiCl2·2H2O, respectively. Compounds 1 and 2 have been characterized by elemental analyses, IR, 1H and 13C{1H} NMR spectroscopy, and FAB+ mass spectrometry, while their slow recrystallization in air from organic solvents revealed a high affinity for water and resulted in the formation of the derived compounds [Ni{HN=C(3‐py)NC(3‐py)=NH}2]·6H2O (1′) and [Ni{HN=C(3‐py)N(H)0.5C(3‐py)=NH}2]Cl·2H2O (2′). Single‐crystal X‐ray diffraction analyses allowed the identification of discrete hexameric water or hybrid water–chloride clusters hosted by the crystal matrixes of 1′ and 2′, respectively. Both the (H2O)6 and [(H2O)4(Cl)2]2– clusters possess similar geometries and consist of cyclic planar tetranuclear (H2O)4 or [(H2O)2(Cl)2]2– cores with two dangling water molecules. These water associates occupy voids in the crystal cells and display extensive H‐bonding interactions with monomeric nickel–organic units, thus playing a key role in the formation of 3D hydrogen‐bonded supramolecular assemblies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A series of cationic (2+) [Ni{HN=C(R)NHC(R)=NH}2](X)2 {R = 4‐(Cl)C6H4 (1), 3‐(NC)C6H4 (3), 4‐(NC)C6H4 (4) and Me (7); X = Cl– (1, 3, 4) or MeCOO–·H2O (7)} and neutral [Ni{HN=C(R)NC(R)=NH}2](solvate) {R = 3‐(Cl)‐4‐py (2), 3‐py (5) and 4‐py (6); solvate = MeOH and/or H2O; py = pyridyl} N,N‐chelating bis(1,3,5‐triazapentadiene/ato)nickel(II) [Ni(tap)2]2+/0 complexes has been easily generated by a ketoxime‐mediated single‐pot reaction of a nickel(II) salt [NiCl2·2H2O or Ni(MeCOO)2·4H2O] with 4‐chlorobenzonitrile, isophthalonitrile, terephthalonitrile, acetonitrile, 2‐chloro‐4‐cyanopyridine, 3‐cyanopyridine or 4‐cyanopyridine, respectively. The obtained compounds have been characterized by IR, 1H and 13C{1H} NMR spectroscopy, FAB‐MS(+) or ESI‐MS(+), elemental analyses and single‐crystal X‐ray diffraction [for 7 and solvated mono‐ {1a·(Me2CO)0.33·(MeOH)0.67} and bis‐deprotonated (2b·2Me2CO, 4b·CHCl3, 5b·Me2CO and 6b·MeOH) products, formed upon recrystallization of 1, 2, 4, 5 and 6, respectively]. The crystal structures of all compounds bear similar monomeric Ni(tap)2 units with a nearly square‐planar geometry. In addition, the structure of 7 features the formation of infinite 1D zig‐zag water–acetate chains {[(H2O)2(MeCOO)2]2–}n, which multiply interact with the [Ni(tap)2]2+ cations to generate a 2D hydrogen‐bonded supramolecular assembly.

2 ], which were isolated in 70-80% yields and characterized by elemental analysis, mass spectrom etry, IR spectroscopy, and 1 H and 13 C{ 1 H} NMR spectroscopy. The structures of the com plexes with R 1 = R 2 = H (1), R 1 = H, R 2 = Me (2), and R 1 = H, R 2 = Ph (4) were established by X ray diffraction analysis.

Some molecular aspects of protective action and specific behavior of hydrocarbon-soluble amides and salts of certain amines and morpholine with carboxylic acids in aqueousorganic environments are considered. The electron densities on those heteroatoms which are presumably responsible for adsorption and inhibition, as well as the Hansch -constants have been calculated. Hypothetical adsorption models have been suggested for tridecanoic acid amides with hexylamine, cyclohexylamine, piperidine, piperazine, morpholine and the cyclohexylamine quaternary salt. Hypothetical adsorption schemes and the probable inhibitor efficiency of the products have been analyzed with consideration for data on the electronic charges and hydrophobicity of the molecules.

The relationship between the physicochemical and electronic characteristics of inhibitors that allows one to forecast the efficiency of metal corrosion inhibitors in waterhydrocarbon media is discussed. It has been shown that the main molecular characteristics of aliphatic acid amides obtained from nitrogen-containing compounds with one amino group and an N-methylolcaprolactam ester make it possible to forecast that they should have high efficiency as corrosion inhibitors in hydrocarbon media.