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. 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. XIV. Adducts of hetercyclic bases with nickel(II) alkylxanthates

1974 ◽  
Vol 27 (10) ◽  
pp. 2099 ◽  
Author(s):  
DP Graddon ◽  
S Prakash
Keyword(s):  
Free Energy ◽  
Alkyl Group ◽  
Benzene Solution ◽  
Bond Formation ◽  
Adduct Formation ◽  
Steric Effects ◽  
Alkyl Chains ◽  
Inductive Effects ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained for the formation in benzene solution of adducts of nickel(11) O-alkylxanthate complexes with one molecule of 2,2'-bipyridine or two molecules of pyridine or 4-methylpyridine. The results show that changes in the free energy and enthalpy of adduct formation with variation of the alkyl group in the xanthate can be explained wholly by inductive effects; there is no evidence for steric effects even with branched alkyl chains.

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. 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. 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.

Sign in / Sign up

Export Citation Format

Share Document