Pseudooctahedral cobalt(III), nickel(II), and cadmium(II) complexes of linear, sexadentate, fluorinated Schiff base ligands

Nuclear magnetic resonance studies of configuration and ligand conformation in paramagnetic octahedral complexes of nickel(II). IX. 1,3-Diamine chelates

“…Support for this analysis is available from the observed shifts of the ß protons which show a separation very nearly as large as that observed in Ni(meso-l ,3-Me2tn)2+, where these protons are conformationally frozen. The observed 67 products for the ß protons, f and e in 8, can be formulated (87•); + jr,<8nih," + *c<«<,.», (8) L, = ^ (87%ß," + V«7(?) Subtraction of eq 8 from eq 9 eliminates the last term (in the skew boat the isoclinal ß protons being equivalent) and one obtains eq 10 which is a measure of the inherent popula- tion difference between the chair conformers at equilibrium.…”

“…This unfavorable strain in the boat form can be partially offset by some bonding interaction of the ß substituent with an axially coordinated ligand or by axial coordination of a group attached at the ß position as in the nickel(II) chelate of 1,1,1 -tris(aminomethyl)ethane. 8 The third possible conformer, the twist, 3, is known from other conformational studies to be intermediate in stability between these two structures, engendering some unfavorable interaction by partial bond eclipsing in its stereochemistry.…”

“…membered ring systems where values have been found to range from 3.4 kcal/mol in the 1,3-dithianes to ca. 8 kcal/ mol in the 1, 3-dioxanes.11 In these heterocyclics, the twist form, when found, often (but not always) owes its existence to sizable, enhancing entropy factors.12 The predicted low enthalpy difference between chair and twist forms in octahedral metal chelates raises the likelihood that twist forms may be present in solution (1) if the twist conformation possesses an appreciable entropy advantage or (2) if steric features built into the ligand seriously and selectively destabilize the chair conformer.…”

Fluoroalkyl-containing 2-arylhydrazono-1,3-dicarbonyl compounds in the reactions with ethylenediamine and polyethylenepolyamines

“…In the presence of nickel(II) ion 1,3-diketones react with ethylenediamine to yield nickel chelates of N,N 0 -ethylene-bis(1,3-aminovinylketones) [4,5]. Polydentate N,N 0 -bis (1,3-aminovinylketones) are the products of the reactions of 1,3-diketones with polyethylenepolyamines [6]. Template nickel ion condensation of trifluoroacetylacetone or acetylacetone with triethylenetetramine leads to the formation of (1,4,7,10-tetraazacyclotrideca-10,12-dienato)-nickel(II) iodide [7].…”

The Crystal and Molecular Structure of a Nickel Complex of the Schiff Base, Bis(trifluroacetylacetone)triethylenetetraamine

“…Condensation of triethylenetetraamine (trien) with P-diketones yields a variety of linear and macrocyclic Schiff base ligands which readily coordinate to transition metal ions (1)(2)(3). The linear, potentially hexadentate ligand, bis(trifluoroacety1acetone)triethylenetetraamine (H2L) forms three complexes with nickel: NIL, Ni-'Presented at the Summer Meeting of the American Crystallographic Association, Pennsylvania State University, August, 1974. (HL)C1.3H20, and Ni(H,L)C12.4M20 (2).…”