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. 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. 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.

Thermodynamics of metal-ligand bond formation. XXIV. Reaction of mercury(II) halides with tertiary arsines and phosphine and arsine sulphides

1976 ◽  
Vol 29 (11) ◽  
pp. 2409 ◽  
Author(s):  
MJ Gallagher ◽  
DP Graddon ◽  
AR Sheikh
Keyword(s):  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Adduct Formation ◽  
Dilute Solution ◽  
Calorimetric Titration ◽  
Factors Affecting ◽  
Tertiary Arsines ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained by calorimetric titration for the formation of 1 : 1 adducts of mercury(11) halides with tertiary arsines in benzene solution. In contrast to phosphines, only one molecule of arsine adds to HgX2 in dilute solution. Enthalpies of adduct formation, in the range - ΔH� = 50-80 kJ mol-1, are not much changed by replacement of phenyl by methyl, but adduct stabilities increase in the order Ph3As < Ph2AsMe < PhAsMe2 < AsMe3 HgI2AsMe3 is dimeric in solution. The diarsines Ph2As(CH2),AsPh2 are unidentate, but Ph2P- (CH2),AsPh2 is bidentate. Data are also reported for addition to HgX2 of Ph3PS,Ph2PSCH2PSPh2 and corresponding arsine sulphides; the disulphides are bidentate. Factors affecting chelation in these compounds are discussed.

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. 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. II. Zinc, cadmium, and mercury(II) complexes of o,o-dialkyldithiophosphates

1971 ◽  
Vol 24 (10) ◽  
pp. 2077 ◽  
Author(s):  
DR Dakternieks ◽  
DP Graddon
Keyword(s):  
Metal Atom ◽  
Alkyl Group ◽  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Free Energies ◽  
Zinc Cadmium ◽  
Metal Ligand ◽  
Ligand Bond

The reactions of 0,O-dialkyldithiophosphato complexes, {(R0)2PSz}zM (M = Zn, Cd, Hg), to form dimers and 1 : 1 and 1 : 2 adducts with pyridine have been studied calorimetrically in benzene solution a t 30�C. While variation of the alkyl group has little effect, variation of the metal atom causes marked changes in both free energies and enthalpies of reaction. Average values of thermodynamic data obtained are as follows (AGOao3 and AH0300 in k J mol-l, AS0a03 in J K-l mol-l) :

Thermodynamics of metal-ligand bond formation. XXIX. Nickel(II) dialkylmonothiocarbamate complexes

1977 ◽  
Vol 30 (10) ◽  
pp. 2133 ◽  
Author(s):  
DP Graddon ◽  
IA Siddiqi
Keyword(s):  
Absorption Spectra ◽  
High Spin ◽  
Benzene Solution ◽  
Bond Formation ◽  
Molecular Weights ◽  
Metal Ligand ◽  
Ligand Bond

In benzene solution at concentrations below 10-2 M, measurements of molecular weights, absorption spectra and the enthalpies of reaction with bases are all consistent with Ni(SOCNR2)2 (R = Pr or Bu) existing as an equilibrium between low-spin monomeric and high-spin dimeric, probably five-coordinate, species. Enthalpies of dimerization are about -55 kJ (g-atom Ni)-1 and dimerization constants increase from 250 l. mol-1 at about 5�C to 1000 l. mol-1 at 30�C, which shows that the entropy of dimerization is not temperature-invariant. Addition of bidentate bases to the monomer is quantitative with ΔH� about -100 kJ mol-1. Addition of pyridine, 4-methylpyridine or piperidine occurs in two steps, giving high-spin adducts, first five-coordinate NiL2B then six-coordinate NiL2B2 with K1 ≈ K2, ΔH1� ≈ -100 and ΔH2� near zero. Comparisons are made with other low-spin nickel(II) complexes which form high-spin polymers or adducts.

Thermodynamics of metal-ligand bond formation. IX. Trimerization and base addition of Bis(2,6-dimethylheptane-3,5-dionato)nickel(II)

1974 ◽  
Vol 27 (2) ◽  
pp. 407 ◽  
Author(s):  
DP Graddon ◽  
TT Nyein
Keyword(s):  
Equilibrium Constant ◽  
Benzene Solution ◽  
Bond Formation ◽  
Addition Reactions ◽  
Dynamic Data ◽  
Metal Ligand ◽  
Ligand Bond

The equilibrium constant for trimerization of bis(2,6-dimethylheptane-3,5-dionato)nicke1(11) in benzene solution at 30�C has been determined spectrophotometrically, K = 2 x 103 I2 mol-1; the heat of trimerization has been determined calorimetrically, ΔH = -7 kJ (g-atom Ni)1. Thermo- dynamic data have also been obtained for the base addition reactions with pyridine leading to first Ni2L4(py) then NiL2(py)2. Results are compared with those previously obtained for other nickel(11) β-diketone complexes.

Thermodynamics of metal-ligand bond formation. XXIII. Lewis acidity of mercury(II) thiocyanate

1976 ◽  
Vol 29 (11) ◽  
pp. 2405 ◽  
Author(s):  
Y Farhangi ◽  
DP Graddon
Keyword(s):  
Bond Formation ◽  
Formation Constants ◽  
Adduct Formation ◽  
Lewis Acidity ◽  
Acetonitrile Solution ◽  
Enthalpies Of Formation ◽  
Dilute Solution ◽  
Lewis Bases ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data are reported for the reaction of Lewis bases with mercury(11) thiocyanate in acetonitrile solution. Pyridine, 4-methylpyridine and tetrahydrothiophen form 1 : 1 adducts with adduct formation constants and enthalpies of formation comparable to those with mercury(11) iodide. 1,l0-Phenanthroline, 2,2'-bipyridine and N,N,N',N?-tetramethylethane-1,2-diamine form chelate 1 : 1 adducts, but with enthalpies of formation little larger than that with pyridine. The phosphines, PPh3 and Pbu3, form 1 : 1 and 1 : 2 adducts of much greater stability, though the enthalpies of formation of these adducts are also similar to that with pyridine; Hg(SCN)2PBu3 is dimeric in dilute solution.

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