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. XXXI. Reaction of Bis(diphenyldithiophosphinato)nickel(II) with heterocyclic bases

1978 ◽  
Vol 31 (11) ◽  
pp. 2417 ◽  
Author(s):  
VTP Anh ◽  
DP Graddon ◽  
VAK Ng
Keyword(s):  
High Spin ◽  
Thermodynamic Data ◽  
Bond Formation ◽  
Adduct Formation ◽  
Spin Configuration ◽  
Planar Complex ◽  
K 13 ◽  
Heterocyclic Bases ◽  
Metal Ligand ◽  
Ligand Bond

The low-spin, planar complex (Ph2PS2),Ni reacts with heterocyclic bases to form (Ph2PS2)2NiB and (Ph2PS2)2NiB2 (B = pyridine or 4-methylpyridine). Average thermodynamic data for adduct formation in chlorobenzene at 30°C are: with pyridine K1 500, K2 251. mol-1, ΔH1� -34, ΔH2� -44 kJ mol-1; with 4-methylpyridine K1 1000, K2 50, ΔH1° -35, ΔH2°-41. With 2- methyl-pyridine only the 1 : 1 adduct is formed, with K 13, ΔH° -34. In these systems the five-coordinate 1 : 1 adducts are unusually stable and are shown to have the high-spin configuration.

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.

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. 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. 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. I. Pyridine adducts of copper(II) complexes of 3-substituted β-diketones

1971 ◽  
Vol 24 (9) ◽  
pp. 1781 ◽  
Author(s):  
DP Graddon ◽  
KB Heng
Keyword(s):  
Benzene Solution ◽  
Bond Formation ◽  
Free Energies ◽  
Thermometric Titration ◽  
Metal Ligand ◽  
Ligand Bond

Free energies, enthalpies, and entropies of formation of adducts of pyridine and some copper(II) complexes of 3-substituted β-diketones have been determined by thermometric titration in benzene solution. The results, which show that adduct stability is determined by the enthalpy, are discussed in terms of the relationships of extrathermodynamics.

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. 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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