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. 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. 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. 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. 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. IV. Base adducts of Bis(ethylxanthato)nickel(II) and Bis(dialkyldithiophosphato)nickel(II)

1971 ◽  
Vol 24 (12) ◽  
pp. 2509 ◽  
Author(s):  
DR Dakternieks ◽  
DP Graddon
Keyword(s):  
Magnetic Susceptibility ◽  
High Spin ◽  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Spin Configuration ◽  
Thermometric Titration ◽  
Metal Ligand ◽  
Ligand Bond

The reactions of pyridine with bis(ethylxanthato)nickel(~~) and bis(dipropy1- dithiophosphato)nickel(~~) and of pyridine, 4-methylpyridine, bipyridyl, and 2,9-dimethyl-l,l0-phenanthroline with bis(diethyldithiophosphato)nickel(~~) have been studied by thermometric titration in benzene solution a t 30�C. The xanthate adds two molecules of pyridine simultaneously, AHolz = -75 kJ mol-1, ASOlz = -186 J K-1 mol-1. With the dithiophosphates, two molecules of base are added in distinct steps; the enthalpy of addition of bipyridyl is similar to that of two molecules of pyridine, but the enthalpy of addition of 2,9-dimethyl-l,l0- phenanthroline is much smaller. The thermodynamic data obtained for these reactions are as follows (AH" in k J mol-1, AS0 in J K-1 mol-1) : dipropyldithiophosphate with py AHol -71, AS01 -211, AHoz 4-2, AS0$ +34 diethyldithiophosphate PY -73 -218 +4 + 40 diethyldithiophosphate 4-mepy - 83 -248 + 7 + 59 diethyldithiophosphate bipy -76 diethyldithiophosphate Mesphen -47 Determination of the magnetic susceptibility in benzene solution containing varying pyridine concentrations has shown that base adducts of the dithiophosphates of both the types NiLzB and NiLzBz have the metal atom in the high-spin configuration.

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. 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. XV. Adducts of mercury(II) halides with bidentate bases

1974 ◽  
Vol 27 (10) ◽  
pp. 2103 ◽  
Author(s):  
Y Farhangi ◽  
DP Graddon
Keyword(s):  
Thermodynamic Data ◽  
Benzene Solution ◽  
Bond Formation ◽  
Adduct Formation ◽  
Mercury Atom ◽  
Satisfactory Explanation ◽  
Metal Ligand ◽  
Enthalpy Data ◽  
Ligand Bond

Thermodynamic data are reported for the reaction of mercury(11) halides with a range of potentially bidentate bases in benzene solution. The enthalpy data show that in 1 : 1 adducts with tetramethyl-alkanediamines and bis(diphenylphosphino)ethane both donor atoms are coordinated, the mercury being four-coordinate with two Hg-N or Hg-P bonds, each of comparable strength to those in 1 : 1 adducts with unidentate bases. N-Methylmorpholine and dioxan are almost certainly unidentate. 1,10-Phenanthroline, 2,2'-bipyridine and N,N'-dimethylpiperazine gave 1 : 1 adducts of higher stability than those of unidentate bases, but the enthalpies of adduct formation were similar or smaller; the most satisfactory explanation of this seems to be that both nitrogen atoms arecoordinated but that the two Hg-N bonds are unusually weak because of steric misfitting of the bidentate base with the mercury atom.

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.

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