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.

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. XXI. Base adducts of nickel(II) glyoximato complexes

1976 ◽  
Vol 29 (6) ◽  
pp. 1201 ◽  
Author(s):  
DP Graddon ◽  
IA Siddiqi
Keyword(s):  
Thermodynamic Data ◽  
Bond Formation ◽  
Adduct Formation ◽  
Lewis Bases ◽  
Alkyl Groups ◽  
Metal Ligand ◽  
Ligand Bond

Bis(glyoximato)nicke1(11) complexes and their BF2-bridged derivatives react with Lewis bases in non-donor solvents forming low-spin 1 : 1 adducts. Thermodynamic data are reported for formation of adducts of glyoximato complexes with PBu3 and of BF2-bridged complexes with pyridine (py), 4-methylpyridine (mpy), piperidine (pip), tributylphosphine, triphenylphosphine, ethane-1,2-diyi- bis(diphenylphosphine) and tetrahydrothiophen. Adduct stability is increased by BF2-bridging; in the Pbu3 adducts this is due to entropy factors. Variation of alkyl groups in the glyoxinie has only a small effect, but replacement of alkyl by Ph or H increases adduct stability while lowering enthalpy of adduct formation. Average values of ΔH� and K (at 30�C) for adducts of BF2-bridged complexes and for PBu3 adducts of H-bridged complexes (last entry) are: PY mpy pip PPh3 PBu3 Pbu3 -ΔH� (kJ mol-l) 29 31 35 23 43 42 K (1.mol-1) 3 5 80 4 800 60

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. 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. XXV. Addition of bases to Bis[O,O'-diethyl thiomalonato]nickel(II) in various solvents

1977 ◽  
Vol 30 (3) ◽  
pp. 495 ◽  
Author(s):  
L Ang ◽  
DP Graddon ◽  
VAK Ng
Keyword(s):  
Thermodynamic Data ◽  
Driving Force ◽  
Bond Formation ◽  
Adduct Formation ◽  
Calorimetric Measurements ◽  
Carbon Tetra ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained from spectroscopic and calorimetric measurements for the addition of pyridine and 4- methylpyridine to bis(O,O?-diethyl thiomalonato)nickel(II), Ni(etm)2, in solution in cyclohexane, benzene, 1,2-dichloroethane, acetonitrile, butan-2-one and carbon tetra-chloride. In each solvent two base molecules add successively, giving Ni(etm)2B then Ni(etm)2B2. There are only small variations in K1 and K2 in different solvents; typically K1 ≈ 200, K2 ≈ 100 l. mol-1, ΔH�1+2 ≈ -65, ΔH�2 ≈ 0 kJ mol-1 at 30�C, but in benzene and cyclohexane ΔH�2 ≈ -25 and in cyclohexane ΔH�1+2 ≈ -100 kJ mol-1. The main driving force for adduct formation is apparently the formation of the first Ni-N bond, which is accompanied by a spin change.

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.

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