Thermodynamics of metal-ligand bond formation. XI. Adducts of heterocyclic bases with copper(II) complexes of fluorinated β-diketones

1974 ◽  
Vol 27 (4) ◽  
pp. 741 ◽  
Author(s):  
DP Graddon ◽  
WK Ong
Keyword(s):  
Enthalpy Of Formation ◽  
Benzene Solution ◽  
Bidentate Ligand ◽  
Molecular Structures ◽  
Enthalpies Of Formation ◽  
Complex Forms ◽  
Heterocyclic Bases ◽  
The Enthalpy Of Formation ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained for the reaction in benzene solution of copper(11) complexes of hexafluoropentanedione and three trifluorinated α-diketones with several unidentate and bidentate heterocyclic bases and terpyridine. With pyridine the hexafluoro� complex forms very stable 1 : 1 and 1 : 2 adducts. The enthalpy of adduct formation (-ΔH) is about 39 kJ mol-1 for the addition of each molecule of pyridine, about 10 kJ mol-1 more than for the formation of the 1 : 1 adduct with the acetylacetone complex. The trifluoro complexes form only 1 : 1 adducts with enthalpy of formation about 31 kJ mol-1 ; these are much more stable than Cu(acac)2(py), but the extra stability is mainly due to entropy factors. With bipyridine and phenanthroline all four fluoro complexes form very stable 1 : 1 adducts with enthalpies of formation about twice those for addition of one molecule of pyridine; this shows that two Cu-N bonds are formed. 2,9-Dimethyl-1,l0-phenanthroline forms a similar adduct, but the enthalpy of formation is much less, due to steric interference. Terpyridine forms a 1 : 1 adduct of much lower stability, probably behaving as an ortho-substituted bidentate ligand. Infrared spectra of the adducts of Cu(tfaa)2 and Cu(hfaa)2 support molecular structures in which one of the Cu-O bonds linking each β-diketone is lengthened to allow the formation of a strong pair of Cu-N bonds.

Thermodynamics of metal-ligand bond formation. VI. Trimerization and base addition of nickel(II) β-diketonates

1973 ◽  
Vol 26 (9) ◽  
pp. 1901 ◽  
Author(s):  
LT Ang ◽  
DP Graddon
Keyword(s):  
Enthalpy Of Formation ◽  
Benzene Solution ◽  
Bond Formation ◽  
Steric Effects ◽  
Calorimetric Titration ◽  
Relative Stabilities ◽  
The Enthalpy Of Formation ◽  
Metal Ligand ◽  
Ligand Bond

Five nickel(II) complexes of β-diketones (LH) have been studied by calorimetric titration with pyridine in benzene solution. Trimerization of the complexes NiL2 is endothermic and entropy-driven, probably as a result of desolvation of the low-spin monomers. Reaction with pyridine occurs in two steps, forming successively Ni2L4(py) and NiL2(py)2. The enthalpy of formation of NiL2(py)2 from the intermediate adduct is about -40 kJ mol-1 and shows no evidence for bulkiness of the ligand leading to steric instability in Ni2L4(py). Variations in the relative stabilities of the monomeric and trimeric forms of NiL2 seem more likely to be due to electronic than steric effects.

Thermodynamics of Metal-Ligand Bond Formation. XVIII Addition of Heterocyclic Bases to Copper(II) and Cobalt(II) Schiff Base Complexes

1976 ◽  
Vol 29 (3) ◽  
pp. 565 ◽  
Author(s):  
L Ang ◽  
DP Graddon
Keyword(s):  
Schiff Base ◽  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Schiff Base Complexes ◽  
Complex Forms ◽  
Heterocyclic Bases ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data are reported for reaction of heterocyclic bases in benzene solution with four-coordinate copper(11) and cobalt(11) Schiff base complexes and also with a five-coordinate nickel(11) complex. The cogper(11) complexes form adducts of low stability with pyridine or 4-methylpyridine, K ≈ 21. mol-1, ΔH� ≈ -20 kJmol-l. The cobalt(11) complexes add two molar proportions of base successively 1 < K1 ≤ K2 < 101.mol-1 ΔH1� ≈ ΔH2� ≈ -20 kJ mol-1 They also form adducts with 2,2'-bipyridine 30 < K < 600 ΔH� ≈ -40kJ mol-1 The nickel(11) complex forms more stable adducts with unidentate bases, K ≈ 1001. mol-l, ΔH� ≈ 70 kJ mol-1. Comparison of the three metals indicates that differences between the stabilities of their base adducts can be attributed mainly to entropy factors.

Thermodynamics of metal-ligand bond formation. XII. Adducts of Monothio-β-diketone complexes with pyridine and bipyridine

1974 ◽  
Vol 27 (6) ◽  
pp. 1351 ◽  
Author(s):  
DR Dakternieks ◽  
DP Graddon
Keyword(s):  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Enthalpies Of Formation ◽  
Calorimetric Titration ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data are reported for the addition of pyridine and bipyridine in benzene solution to monothio-β-diketone complexes, ML2, of nickel(11), copper(11), zinc(11) and mercury(11). NiL2 gives NiL2(py)2 and NiL(bpy); ZnL2 gives ZnL2(py) and ZnL2(bpy); in both cases the data show that bipyridine is bidentate. CuL2 gives CuL2 (py) and CuL2 (bpy), with almost equal enthalpies of formation, but the higher stability of CuL2(bpy) shows bipyridine is probably bidentate. HgL2 gives HgL2(py) and a reaction with bipyridine which shows that an extremely unstable adduct is formed. All data were obtained by calorimetric titration.

scholarly journals Thermodynamics of metal-ligand bond formation. VIII. Pyridine adducts of zinc(II) β-diketonates

1973 ◽  
Vol 26 (11) ◽  
pp. 2537 ◽  
Author(s):  
DR Dakternieks ◽  
DP Graddon
Keyword(s):  
Benzene Solution ◽  
Equilibrium Constants ◽  
Bond Formation ◽  
Formation Constants ◽  
Adduct Formation ◽  
Enthalpies Of Formation ◽  
Calorimetric Titration ◽  
Experimental Conditions ◽  
Metal Ligand ◽  
Ligand Bond

Equilibrium constants and enthalpies in benzene solution are reported for the formation of 1 : 1-adducts of pyridine with four zinc(II) complexes of β-diketones, determined by calorimetric titration. Adduct formation constants at 30�C fall in the range 300-2000 and enthalpies of formation lie between -15 and - 34 kJ mol-1. Though the enthalpies of formation differ little from those of corresponding copper(II) complexes, the adducts are about a hundred times more stable. The pyridine adduct of bis(2,2,6,6-tetramethylheptane-3,5-dionato)zinc(II) is entropy-stabilized relative to those of other complexes. No evidence was obtained for the addition of a second molecule of pyridine under the experimental conditions used.

Thermodynamics of metal-ligand bond formation. VII. Pyridine adducts of nickel(II) salicylideneiminato complexes

1973 ◽  
Vol 26 (11) ◽  
pp. 2379 ◽  
Author(s):  
DR Dakternieks ◽  
DP Graddon
Keyword(s):  
Inductive Effect ◽  
Benzene Solution ◽  
Bond Formation ◽  
Enthalpies Of Formation ◽  
Calorimetric Titration ◽  
Alkyl Complexes ◽  
Aryl Complexes ◽  
Entropy Effects ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained by calorimetric titration in benzene solution at 30�C for the reaction: NiL2+2py = NiL2(py)2 for 16 different nickel(II) complexes of Schiff bases of salicylaldehyde, 5- chlorosalicylaldehyde, and 5-chloro-2-hydroxybenzophenone. It has also been possible to obtain data for the trimerization of bis(N-phenyl-5- chlorosalicylideneiminato)nickel(II), and for two of the complexes estimates have been obtained for the addition of base in two successive steps. ��� Pyridine adducts, NiL2(py)2, of N-aryl complexes have enthalpies of formation about -40 kJ mol-1, those of N-alkyl complexes about -60 kJ mol-1 and a small inductive effect can be observed due to chloro substitution, but variations in stabilities of the adducts arise mainly from entropy effects. In the two systems studied most of the enthalpy of adduct formation is associated with addition of the second molecule of base.

Thermodynamics of metal-ligand bond formation. XXII. Zinc(II) and cadmium(II) dialkyldithiocarbamates

1976 ◽  
Vol 29 (7) ◽  
pp. 1429 ◽  
Author(s):  
L Ang ◽  
DP Graddon
Keyword(s):  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Adduct Formation ◽  
Heterocyclic Bases ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data are reported for dimerization of dialkyldithiocarbamates, (R2NCS2)2Cd, and for addition of heterocyclic bases to (R2NCS2)2Cd and (R2NCS2)2Zn in benzene solution. Enthalpies of reaction are comparable to those of corresponding dithiophosphates, but adduct formation and dimerization constants are smaller and the dithiocarbamates add only one molecule of base. Though probably bidentate, 2,2'-bipyridine forms less stable adducts with (R2NCS2)2Zn than does pyridine.

Thermodynamics of metal-ligand bond formation. III. Adducts of heterocyclic bases with Bis(N-nitroso-N-phenylhydroxylaminato)copper(II)

1971 ◽  
Vol 24 (11) ◽  
pp. 2267 ◽  
Author(s):  
DP Graddon ◽  
CY Hsu
Keyword(s):  
Steric Hindrance ◽  
Benzene Solution ◽  
Bond Formation ◽  
Adduct Formation ◽  
Thermometric Titration ◽  
Sterically Hindered ◽  
Heterocyclic Bases ◽  
Metal Ligand ◽  
Ligand Bond

The copper(II) complex of N-nitroso-N-phenylhydroxylamine (copper cupferrate) reacts with heterocyclic bases in benzene solution to form 1 : 1-adducts. Enthalpies and entropies of adduct formation with a range of bases have been determined by thermometric titration. The results, which are similar to those obtained with copper(II) complexes of β-diketones, reveal two isoequilibrium series for sterically hindered and unhindered bases, and indicate that the effect of the steric hindrance is probably to restrict rotation of the base molecule about the newly formed metal-ligand bond.

Thermodynamics of metal-ligand bond formation. XX. Reaction of tertiary phosphines with mercury(II) halides

1976 ◽  
Vol 29 (4) ◽  
pp. 759 ◽  
Author(s):  
MJ Gallagher ◽  
DP Graddon ◽  
AR Sheikh
Keyword(s):  
Linear Relationship ◽  
Benzene Solution ◽  
Bond Formation ◽  
Enthalpies Of Formation ◽  
Bridging Ligand ◽  
Tertiary Phosphines ◽  
Inductive Effects ◽  
Metal Ligand ◽  
Enthalpy Data ◽  
Ligand Bond

Tertiary phosphines form highly stable 1 : 1 and 2 : 1 adducts with mercury(11) halides in benzene solution. In the series of phosphines (alkyl),PPh3-n enthalpies of formation are determined by inductive effects and give a linear relationship with Taft constants, ∑σ*. The cyclic phosphine 1,2,5-triphenylphosphole is a much weaker base towards the mercury(11) halides. While ethane-1,2- diylbis(dipheny1phosphine) behaves only as a chelate, methylenebis(dipheny1phosphine) can behave both as a chelate and as a bridging ligand and propane-1,3-diylbis(dipheny1phosphine) only as a bridging ligand. The unsaturated diphosphines (2)- and (E)-ethene-l,2-diylbis(dipheny1phosphine) both form 1 : 1 adducts with mercury(11) halides in benzene solution in which the phosphines are unidentate. Enthalpy data are reported for the formation of all these adducts.

Thermodynamics of metal-ligand bond formation. V. Adducts of mercury(II) halides with Lewis bases

1973 ◽  
Vol 26 (5) ◽  
pp. 983 ◽  
Author(s):  
Y Farhangi ◽  
DP Graddon
Keyword(s):  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Enthalpies Of Formation ◽  
Lewis Bases ◽  
Entropy Effects ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained for the reactions of mercury(II) halides with Lewis bases in benzene solution at 30�C. With tributyl- and triphenyl-phosphines 1 : 1 and 2 : 1 adducts were observed in solution, the 1 : 1 adduct with tributylphosphine being associated. With tetrahydrofuran, tributylamine, pyridine, 2-methylpyridine, 4- methylpyridine, tetrahydrothiophen, and triphenylarsine only 1 : 1 adducts were observed in solution, monomeric and three-coordinate, except for HgI2AsPh3, which probably associates to some extent. In most cases the enthalpies of formation of 1 : 1 adducts in solution are about -70 kJ mol-1; lower enthalpies of formation of the tributylamine adducts, about -40 kJ mol-1, are attributed to the absence of π-bonding and much lower enthalpies of formation of tetrahydrofuran adducts to the ?B character? of mercury. Wide variations in the stabilities of the adducts are mainly due to entropy effects, probably arising from differences in the solvation of the adducts.

A Solvent-Dependent and Electrochemically Controlled Self-Assembling/Disassembling System

2003 ◽  
Vol 68 (9) ◽  
pp. 1647-1662 ◽  
Author(s):  
Valeria Amendola ◽  
Massimo Boiocchi ◽  
Yuri Diaz Fernandez ◽  
Carlo Mangano ◽  
Piersandro Pallavicini
Keyword(s):  
Equilibrium Mixture ◽  
Bidentate Ligand ◽  
Molecular Structures ◽  
The Self ◽  
Molar Ratio ◽  
Crystal And Molecular Structures ◽  
Self Assembling ◽  
Irreversible Oxidation ◽  
Irreversible Reduction ◽  
Metal Ligand

The bis-bidentate ligand R,S-1,2-diphenyl-N,N'-bis(2-quinolinemethylidene)ethane-1,2-diamine (ligand 4), containing two (iminomethyl)quinoline moieties separated by a cis-1,2-diphenylethylene spacer, forms stable complexes with both CuI and CuII. With CuII, the monomeric 1:1 complex [CuII(4)]2+ is obtained both in CH3CN and CH2Cl2. With CuI and overall 1:1 metal/ligand molar ratio, an equilibrium mixture is obtained in CH3CN, consisting of [CuI(4)2]+, [CuI2(4)2]2+ and [CuI2(4)(CH3CN)4]2+. The preponderant species is the two-metal one-ligand "open" complex [CuI2(4)(CH3CN)4]2+, in which each Cu+ cation is coordinated in a tetrahedral fashion by one (iminomethyl)quinoline unit and by two CH3CN molecules. Precipitation from the equilibrium mixture yields only crystals of [CuI2(4)(CH3CN)4](ClO4)2·2CH3CN, whose crystal and molecular structures have been determined. On the other hand, in the poorly coordinating CH2Cl2 solvent, only the dimeric helical [CuI2(4)2]2+ complex is obtained, when the overall metal/ligand 1:1 molar ratio is chosen. Addition of large quantities of acetonitrile to solutions of [CuI2(4)2]2+ in dichlorometane results in the formation of [CuI2(4)(CH3CN)4]2+, i.e. in the solvent-driven disassembling of the CuI helicate. While electrochemistry in CH3CN is poorly defined due to the presence of more than one CuI species, cyclic voltammetry experiments carried out in CH2Cl2 revealed a well defined behavior, with irreversible oxidation of [CuI2(4)2]2+ and irreversible reduction of [CuII(4)]2+ taking place at separate potentials (∆E ≈ 700 mV). Irreversibility and separation of the redox events are due to the self-assembling and disassembling processes following the reduction and oxidation, respectively.

Sign in / Sign up

Export Citation Format

Share Document