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. 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. 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. 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. 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. 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.

Sign in / Sign up

Export Citation Format

Share Document