Solution-reaction Calorimetry Research Articles

Enthalpy of solvation of alkali metal salts in a protic ionic liquid: Effect of cation charge and size

• Experimental and theoretical study of solution and solvation of mono- and divalent alkaline metal cations. • MD simulations provided coordination numbers, which showed an interesting similarity in IL and water environments. • Solvation of alkali and alkaline earth nitrate metal salts ((LiNO 3 , KNO 3 , RbNO 3 , CsNO 3 , Mg(NO 3 ) 2 and Ca(NO 3 ) 2 ) in EAN. • Analysis of the energetics and structure of solvation confirms the well-known water-like solvation properties of EAN. An experimental and theoretical study of solution and solvation of mono- and divalent alkali metal cations in the protic ionic liquid (IL) ethylammonium nitrate (EAN) is reported. High precision solution-reaction calorimetry was used to obtain the heat of solvation, which was used for the analysis of the thermodynamics. A close relation between the structure of the salts in the crystalline phase and its enthalpy of solvation in the IL is reported. A detailed picture of the molecular environments in the solvation shells around the metal cations is provided by means of molecular dynamics simulations. The analysis of the energetics and structure of solvation confirms the well-known water-like solvation properties of EAN, with the solvation shell around the metal cations in both media being very similar. On the other hand, the results show that it is energetically more favourable to solvate smaller cations with higher valence. Indeed, the simulations show that the long-range electrostatic interactions are the main contribution to solvation interaction, with the electric field at the surface of the alkali metal cations as the basic magnitude controlling it.

Metal–ligand binding energies in copper (II) and nickel (II) complexes with tetradentate N2O2 Schiff base ligands

This work constitutes a new contribution for understanding the relationship between the metal–ligand bonding and, indirectly, the inherent reactivity of metallic complexes with tetradentate N2O2 Schiff base ligands, being reported the energetic characterization of two transition metal complexes – (N,N'́-bis(salicylaldehydo)tetramethylenediiminate)nickel(II) and (N,N'-bis(salicylaldehydo)propylenediiminate)copper(II). The standard molar enthalpies of formation of these complexes were determined by solution-reaction calorimetry measurements. Their standard molar enthalpies of sublimation, at T = 298.15 K, were obtained by an effusion method. From these studies, the gas-phase enthalpies of formation of Ni(II) and Cu(II) complexes, at T = 298.15 K, were derived. Differences between the metal–ligand and mean hydrogen-ligand bond dissociation enthalpies were derived and discussed in structural terms, in comparison with identical parameters for complexes of the same metals with analogous tetradentate Schiff bases. High-level quantum chemical calculations have also been conducted, complementing the results obtained experimentally.

Synthesis and energetics of Na, K, Rb and Cs salts by reaction with 1,2-ethanediol and 1,4-butanediol

The study of direct reactions of Na, K, Rb and Cs with 1,2-ethanediol and with 1,4-butanediol was undertaken as well as the reactions of Na and K with 1,2-ethanediol by an ammoniacal route. All compounds were characterized by standard elemental analysis techniques, thermogravimetric analysis (TGA) and infrared (IR) spectroscopy. The results show that only one hydroxyl group reacts with the metal leading to the formation of compounds of the type M(OC2H4OH) or M(OC4H8OH), where M stands for the alkaline metal, except for the reaction of Cs with 1,2-ethanodiol that points to the formation of an adduct, Cs(OC2H4OH).HOC2H4OH. The standard enthalpies of formation of the alkaline metal diolates in the crystalline state were determined by reaction-solution calorimetry. The obtained results at 298.15K were as follows: ΔfHmo (MOCxH2xOH, cr)/kJ⋅mol−1=−589.46.0 (NaOC2H4OH), −654.28.3 (NaO-n-C4H8OH), −615.17.4 (KOC2H4OH), −679.97.7 (KO-n-C4H8OH), -609.83.1 (RbOC2H4OH), and −1091.4±6.3 (CsOC2H4OH·HOC2H4OH). These results were compared with the literature values for other alkoxides and together with auxiliary values were used to derive a consistent set of lattice energies for MOCxH2xOH compounds based on the Kapustinskii equation. This allows the estimation of the enthalpy of formation for some non-measured diolates.

Thermodynamic properties of chlorite and berthierine derived from calorimetric measurements

In the context of the deep waste disposal, we have investigated the respective stabilities of two iron-bearing clay minerals: berthierine ISGS from Illinois [USA; (Al0.975FeIII0.182FeII1.422Mg0.157Li0.035Mn0.002)(Si1.332Al0.668)O5(OH)4] and chlorite CCa-2 from Flagstaff Hill, California [USA; (Si2.633Al1.367)(Al1.116FeIII0.215Mg2.952FeII1.712Mn0.012Ca0.011)O10(OH)8]. For berthierine, the complete thermodynamic dataset was determined at 1 bar and from 2 to 310 K, using calorimetric methods. The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K, and the heat capacities were measured by heat-pulse calorimetry. For chlorite, the standard enthalpy of formation is measured by solution-reaction calorimetry at 298.15 K. This is completing the entropy and heat capacity obtained previously by Gailhanou et al. (Geochim Cosmochim Acta 73:4738–4749, 2009) between 2 and 520 K, by using low-temperature adiabatic calorimetry and differential scanning calorimetry. For both minerals, the standard entropies and the Gibbs free energies of formation at 298.15 K were then calculated. An assessment of the measured properties could be carried out with respect to literature data. Eventually, the thermodynamic dataset allowed realizing theoretical calculations concerning the berthierine to chlorite transition. The latter showed that, from a thermodynamic viewpoint, the main factor controlling this transition is probably the composition of the berthierine and chlorite minerals and the nature of the secondary minerals rather than temperature.

Enthalpies of formation of europium alkoxides: What lessons can be drawn from them

The synthesis and characterization of two europium alkoxides, Eu(OCH3)2 and Eu(OC2H5)2, were described. For the first time the enthalpies of formation of divalent lanthanide alkoxides were determined by using reaction-solution calorimetry. The values obtained are ΔfH0 [Eu(OCH3)2,cr]=−850.5±5.0kJ/mol and ΔfH0 [Eu(OC2H5)2,cr]=−902.5±5.5kJ/mol, respectively. Since these compounds have a large use as catalysts or catalysts precursors, the first step of the reaction of them with CO2 was addressed, which permits to have an idea of the kind of bond involved in those compounds. Moreover, insertion of CO2 in the europium oxygen bond and formation of metal carboxylate complexes, is in both cases presumably bidentate.

Thermodynamic properties of saponite, nontronite, and vermiculite derived from calorimetric measurements

The stability of clay minerals is an important factor in assessing the durability of containment barriers for deep waste storage. In that context, the complete thermodynamic data set of three 2:1 ferro-magnesian clay minerals have been determined at 1 bar and from 2 to 520 K, using calorimetric methods. The studied clay samples were, respectively, the Na-saturated saponite Sap-Ca-1, Na 0.394 K 0.021 Ca 0.038 (Si 3.569 Al 0.397 Fe 3+ 0.034 )(Mg 2.948 Fe 2+ 0.021 Mn 0.001 )O 10 (OH) 2 , the Ca-saturated nontronite NAu-1, Ca 0.247 K 0.020 (Si 3.458 Al 0.542 )(Mg 0.066 Fe 3+ 1.688 Al 0.268 Ti 0.007 )O 10 (OH) 2 , and the Ca-saturated Santa Olalla vermiculite, Ca 0.445 (Si 2.778 Al 1.222 )(Al 0.192 Mg 2.468 Fe 3+ 0.226 Fe 2+ 0.028 Ti 0.018 Mn 0.007 )O 10 (OH) 2 . The standard enthalpies of formation were obtained by solution-reaction calorimetry at 298.15 K. The heat capacities were measured between 2 and 520 K, using low-temperature adiabatic calorimetry, heat-pulse calorimetry, and differential scanning calorimetry. The standard entropies and the Gibbs free energies of formation at 298.15 K have been calculated from these values. Finally, the equilibrium constants at 298.15 K have been determined. A comparison between these experimental data and estimated values obtained from prediction models available in the literature enabled the most usual calculation methods available to date to be assessed for each thermodynamic property.

Thermodynamic properties of illite, smectite and beidellite by calorimetric methods: Enthalpies of formation, heat capacities, entropies and Gibbs free energies of formation

The thermodynamic properties of three aluminous 2:1 clay minerals were acquired at 1.013 bars and at temperatures between 5 and 500K using various calorimetric methods. Calorimetric measurements were performed on hydrated and dehydrated <2μm clay fractions of smectite MX-80 (Wyoming), illite IMt-2 (Silver Hill) and beidellite SBId-1 (Black Jack Mine). After purification, the mineralogical analyses gave the following structural formulae:Na0.409K0.024Ca0.009(Si3.738Al0.262)(Al1.598Mg0.214Fe0.1733+Fe0.0352+)O10(OH)2,K0.762Na0.044(Si3.387Al0.613)(Al1.427Mg0.241Fe0.2923+Fe0.0842+)O10(OH)2 and Ca0.185K0.104(Si3.574Al0.426)(Al1.812Mg0.09Fe0.1123+)O10(OH)2 for smectite MX-80, illite IMt-2 and beidellite SBId-1, respectively. Heat capacities were measured by low temperature adiabatic calorimetry and differential scanning calorimetry, from 5 to 500K. Standard enthalpies of formation were obtained from solution–reaction calorimetry at 298.15K. The standard Gibbs free energies of formation of the clay minerals were also calculated, together with the equilibrium constants at 25°C, for anhydrous and hydrated minerals. A comparison between these experimental data and estimated values obtained from prediction models available in the literature, enabled the calculation method that appears to be the most relevant to be selected, at least for aluminous 2:1 clay minerals.

Thermochemical Parameters of Mercury(II) Chelates Involving Dimethyl and Di-isopropyl Dithiocarbamates

The standard molar enthalpies of formation of crystalline dialkyldithiocarbamate chelates of mercury(II) were determined by using reaction-solution calorimetry. Two different complexes were studied: Hg(S2CNR2)2 with R = CH3 (Me) and i-C3H7 (Pri). The enthalpies of formation for the mercury complexes were determined in 1,2-dichloroethane at 298 K. The hemolytic and heterolytic mean enthalpies of dissociation of the Hg–S bonds were calculated by using the standard molar enthalpy of the gaseous chelates.

Standard enthalpies of formation of Li, Na, K, and Cs thiolates

The standard enthalpies of formation of alkaline metals thiolates in the crystalline state were determined by reaction-solution calorimetry. The obtained results at 298.15 K were as follows: \( \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} ({\text{MSR,}}\;{\text{cr}}) \)/kJ mol−1 = −259.0 ± 1.6 (LiSC2H5), −199.9 ± 1.8 (NaSC2H5), −254.9 ± 2.4 (NaSC4H9), −240.6 ± 1.9 (KSC2H5), −235.8 ± 2.0 (CsSC2H5). These results where compared with the literature values for the corresponding alkoxides and together with values for \( \Updelta_{\text{f}} H_{\text{m}}^{\text{o}} \left( {{\text{MSH}},\;{\text{cr}}}\right)\) were used to derive a consistent set of lattice energies for MSR compounds based on the Kapustinskii equation. This allows the estimation of the enthalpy of formation for some non-measured thiolates.

Standard molar enthalpies of formation of zinc(II) β-diketonates and monothio-β-diketonates

The standard ( p ∘ = 0.1 MPa) molar enthalpies of formation of crystalline bis(dibenzoylmethanate)zinc(II), Zn(DBM) 2, diaquobis(thenoyltrifluoroacetonate)zinc(II), Zn(TTFA) 2(H 2O) 2, bis(monothiodibenzoylmethanate)zinc(II), Zn(HDBMS) 2, and bis(monothio-thenoyltrifluoroacetonate)zinc(II), Zn(HTTFAS) 2, were determined, at T = 298.15 K, by high precision solution-reaction calorimetry. The standard molar enthalpy of dehydration of the diaquobis(thenoyltrifluoroacetonate)zinc(II), Zn(TTFA) 2(H 2O) 2, complex was measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean molar dissociation enthalpies zinc(II)-ligand, 〈 D m〉(Zn-L), were derived. Zinc(II)-β-diketonate Δ f H m ∘ ( cr ) kJ · mol - 1 Bis(dibenzoylmethanate)zinc(II), Zn(DBM) 2 −546.9 ± 4.0 Diaquobis(thenoyltrifluoroacetonate)zinc(II), Zn(TTFA) 2(H 2O) 2 −2556.2 ± 8.4 Bis(monothiodibenzoylmethanate)zinc(II), Zn(DBMS) 2 −107.0 ± 5.9 Bis(monothiothenoyltrifluoroacetonate)zinc(II), Zn(TTFAS) 2 −1563.6 ± 8.0

Thermochemistry of Cu(II) and Ni(II) complexes with N,N-di-n-butyl-N′-thenoylthiourea and N,N-di-iso-butyl-N′-thenoylthiourea

Two substituted N-acylthioureas and the respective Ni(II) and Cu(II) complexes were synthesized, namely: N,N-di-n-butyl-N′-thenoylthiourea (Hnbtu); N,N-di-iso-butyl-N′-thenoylthiourea (Hibtu); bis[N,N-di-n-butyl-N′-thenoylthioureato]nickel(II), [Ni(nbtu)2]; bis[N,N-di-n-butyl-N′-thenoylthioureato]copper(II), [Cu(nbtu)2]; bis[N,N-di-iso-butyl-N′-thenoylthioureato]nickel(II), [Ni(ibtu)2]; bis[N,N-di-iso-butyl-N′-thenoylthioureato]copper(II), [Cu(ibtu)2]. The standard (p∘=0.1MPa) molar enthalpies of formation and sublimation of the two N-acylthioureas were measured, at T=298.15K, by rotating-bomb combustion calorimetry and Calvet microcalorimetry, respectively. The standard (p∘=0.1MPa) molar enthalpies of formation of the Ni(II) and Cu(II) complexes were determined, at T=298.15K, by high precision solution–reaction calorimetry. From the results obtained, the enthalpies of hypothetical metal–ligand and metal–metal exchange reactions, in the gaseous phase, were derived, thus allowing a discussion of the gaseous phase energetic difference between the complexation of Ni(II) and Cu(II) to 1,3-ligand systems with (S,O) ligator atoms.

Thermodynamic properties of caesium–magnesium monophosphate

The heat capacity measurements of the crystalline phosphate CsMgPO4 of a tridymite structure were performed between T=(7 and 650)K. The thermodynamic functions Cp,m∘/R, Δ0THm∘/RT, Δ0TSm∘/R, and Φm∘/R were calculated and the fractal dimension Dfr evaluated. From the solution reaction calorimetry, the standard enthalpy of CsMgPO4 formation at T=298.15K was found. Thermochemical parameters of formation ΔfGm∘ and lgKf,m∘ were determined by combining the data obtained by these techniques.

Synthesis, characterization and standard molar enthalpy of formation of Sm(C 7H 5O 3) 2·(C 9H 6NO)

The complex of bis(salicylato)hydroxyquinolinosamarium(III), Sm(C 7H 5O 3) 2·(C 9H 6NO), was synthesized and characterized by IR, elemental analysis, molar conductance and thermogravimetric analysis. The standard molar enthalpies of solution of [SmCl 3·6H 2O(s)], [2C 7H 6O 3(s)], [C 9H 7NO(s)] and [Sm(C 7H 5O 3) 2·(C 9H 6NO)(s)] in the calorimetric solvent (a mixed solution consisting of absolute ethyl alcohol, dimethyl formamide (DMF) and perchloric acid were determined by solution-reaction calorimetry at 298.15 K, respectively. The enthalpy of the reaction (1) SmC l 3 ⋅ 6 H 2 O ( s ) + 2 C 7 H 6 O 3 ( s ) + C 9 H 7 NO ( s ) = Sm ( C 7 H 5 O 3 ) 2 ⋅ ( C 9 H 6 NO ) ( s ) + 3 HCl ( g ) + 6 H 2 O ( l ) was determined to be Δ r H m ° = 89.59 ± 0.18 kJ mo l − 1 . According to the above results and the data given in literature, through Hess’ law, the standard molar enthalpy of formation of Sm(C 7H 5O 3) 2·(C 9H 7NO)(s) was estimated to be Δ f H m ° [Sm(C 7H 5O 3) 2·(C 9H 6NO)(s), 298.15 K] = −2055.9 ± 3.03 kJ mol −1.

Enthalpies of formation of adducts of antimony(III) iodide with pyridine and methyl-pyridines

Solid adducts of formula SbI 3·L (L = pyridine or 2-, 3- or 4-methylpyridine abbreviated as Py, 2MPy, 3MPy or 4MPy) were synthesized and characterized by elemental analysis, IR spectroscopy and thermal analysis. IR data showed that coordination to antimony is through nitrogen. Thermal degradation of adducts starts at 431, 423, 413 and 411 K for Py, 2MPy, 3MPy and 4MPy, respectively. Reaction-solution calorimetry was used to evaluate the enthalpy change of reaction: SbI 3(cr) + L(l) = SbI 3·L(cr), 61.13 ± 1.75, −82.60 ± 1.55, −67.50 ± 0.97 and −74.10 ± 1.19 kJ mol −1, respectively. Enthalpy change values for decomposition of adducts, lattice enthalpies and enthalpies of the Lewis acid–base reaction in the gas phase were calculated through appropriate thermochemical cycles. Mean Sb N bond enthalpies were estimated as 134 ± 3, 154 ± 3, 140 ± 3 and 147 ± 4 kJ mol −1, for Py, 2MPy, 3MPy and 4MPy, respectively.

Thermochemical studies of five crystalline bis( O-alkyl- N-thenoylthiocarbamato)nickel(II) complexes

The standard ( p ∘ = 0.1 MPa) molar enthalpies of the crystalline complexes of five N-thenoylthiocarbamic- O-alkylesters, C 4H 3SCONHCSOR, R = Et, n-Pr, n-Bu, n-Pen, n-Hex, with Ni(II), were determined, at T = 298.15 K, by high precision solution-reaction calorimetry. Nickel(II) complex - Δ f H m ∘ ( cr ) / ( kJ · mol - 1 ) Bis( O-ethyl- N-thenoylthiocarbamato)nickel(II) Ni(C 4H 3SCONCSOEt) 2 629.7 ± 7.0 Bis( O- n-propyl- N-thenoylthiocarbamato)nickel(II) Ni(C 4H 3SCONCSO- n-Pr) 2 636.8 ± 6.0 Bis( O- n-butyl- N-thenoylthiocarbamato)nickel(II) Ni(C 4H 3SCONCSO- n-Bu) 2 681.1 ± 6.1 Bis( O- n-pentyl- N-thenoylthiocarbamato)nickel(II) Ni(C 4H 3SCONCSO- n-Pen) 2 750.2 ± 8.5 Bis( O- n-hexyl- N-thenoylthiocarbamato)nickel(II) Ni(C 4H 3SCONCSO- n-Hex) 2 804.8 ± 8.6 The results are analyzed in terms of structural contribution to the standard molar enthalpies of formation. The metal–ligand exchange enthalpies in the crystalline phase show that the increase of the ester-alkyl chain length does not significantly affect the difference between the metal to ligand and the hydrogen to ligand binding enthalpies, [ D(M–L) − D(H–L)].

Crystalline-hydrated barium phenylphosphonate as a host for n-alkyldiamine intercalation

A series of n-alkyldiamines with the general formula H 2 N(CH 2 ) n NH 2 (n = 2–6) has been intercalated into crystalline lamellar-hydrated barium phenylphosphonate from ethanolic solutions. The amount intercalated was followed batchwise and the variation in interlayer distance (d) for the original host and the respective intercalated compounds was followed by x-ray diffraction patterns. Linear correlation with good fits were obtained for (d) or for the number of moles intercalated (n f ) as a function of the number of carbon atoms in the aliphatic chains (n c ): d = (1436 ± 65) + (108 ± 14)n c and n f = (2.24 ± 0.15) – (0.31 ± 0.03)n c . The energetic effect caused by amine intercalation was determined through reaction-solution calorimetry at the solid-liquid interface from ethanolic solutions. The resulting exothermic enthalpies for intercalation give rise to a monomolecular layer guest molecule arrangement with a longitudinal axis inclined by 58° to the inorganic sheets. The thermodynamic data showed that the system is favored by exothermic enthalpy, negative Gibbs free energy, and positive entropic values.

Standard molar enthalpies of formation of nickel(II) β-diketonates and monothio-β-diketonates

The standard ( p ∘ = 0.1 MPa) molar enthalpies of formation of the crystalline diaquobis(dibenzoylmethanate)nickel(II), Ni( dbm) 2(H 2O) 2, diaquobis(thenoyltrifluoroacetonate)nickel(II), Ni( ttfa) 2(H 2O) 2 bis(monothiodibenzoylmethanate)nickel(II), Ni( dbmS) 2 and bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni(H ttfaS) 2 were determined, at T = 298.15 K, by high precision solution-reaction calorimetry. The standard molar enthalpy of sublimation of the monothiothenoyltrifluoroacetone (H ttfaS) complex was measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean nickel(II)-ligand molar dissociation enthalpies, 〈 D m〉(Ni–L), were derived. Δ f H m ∘ (cr) / ( kJ · mol - 1 ) Diaquobis(dibenzoylmethanate)nickel(II), Ni( dbm) 2(H 2O) 2 −993.3 ± 3.8 Diaquobis(thenoyltrifluoroacetonate)nickel(II), Ni( ttfa) 2(H 2O) 2 −2452.0 ± 8.3 Bis(monothiodibenzoylmethanate)nickel(II), Ni( dbmS) 2 −42.1 ± 5.9 Bis(monothiothenoyltrifluoroacetonate)nickel(II), Ni( ttfaS) 2 −1473.5 ± 8.1

Thermochemical study of two anhydrous polymorphs of caffeine

The mean values of the standard massic energy of combustion of caffeine in phase I (or alpha) and in phase II (or beta) measured by static-bomb combustion calorimetry in oxygen, at T = 298.15 K, are Δ c u ∘ (C 8H 10O 2N 4, I) = −(21823.27 ± 0.68) J · g −1 and Δ c u ∘ (C 8H 10O 2N 4, II) = −(21799.96 ± 1.08) J · g −1, respectively. The standard ( p ∘ = 0.1 MPa) molar enthalpy of formation in condensed phase for each form was derived from the corresponding standard molar enthalpies of combustion as, Δ f H m ∘ ( C 8 H 10 O 2 N 4 , cr, I ) = - ( 340.6 ± 2.3 ) kJ · mol - 1 and Δ f H m ∘ ( C 8 H 10 O 2 N 4 , cr, II ) = - ( 345.1 ± 2.3 ) kJ · mol - 1 . The difference between the standard enthalpy of formation of the two polymorphs in condensed phase was also evaluated by using reaction-solution calorimetry. The obtained result, 2.04 ± 0.25 kJ · mol −1, is in agreement, within the uncertainty, with the difference between the molar enthalpies of formation obtained from combustion experiments (4.5 ± 3.2) kJ · mol −1, which can be considered as an internal test for consistency of the results. A value for the standard enthalpy of formation of caffeine in the gaseous state was proposed: Δ f H m ∘ ( C 8 H 10 O 2 N 4 , g ) = - ( 229.7 ± 6.1 ) kJ · mol - 1 , estimated from the values of the standard enthalpies of formation of both crystalline forms obtained in this work, and the data on standard enthalpies of sublimation collected from the literature.

Standard molar enthalpies of formation of copper(II) β-diketonates and monothio-β-diketonates

The standard ( p ∘ = 0.1 MPa) molar enthalpies of formation of the crystalline complexes of dibenzoylmethane (H dbm), thenoyltrifluoroacetone (H ttfa), monothiodibenzoylmethane (H dbmS), and monothiothenoyltrifluoroacetone (H ttfaS) of copper(II) were determined, at T = 298.15 K, by high precision solution-reaction calorimetry. The standard molar enthalpies of sublimation of the copper(II) β-diketonate complexes were measured by high-temperature Calvet microcalorimetry. From the standard molar enthalpies of formation of the complexes in the gaseous state, the mean molar dissociation enthalpies copper(II)–ligand, 〈 D m〉(Cu–L), were derived. Δ f H m ∘ ( cr ) Δ cr g H m ∘ kJ · mol −1 kJ · mol −1 Bis(dibenzoylmethanate)copper(II), Cu( dbm) 2 −364.0 ± 3.9 230.7 ± 8.2 Bis(thenoyltrifluoroacetonate)copper(II), Cu( ttfa) 2 −1824.3 ± 8.3 167.9 ± 7.4 Bis(monothiodibenzoylmethanate)copper(II), Cu( dbmS) 2 35.6 ± 7.7 [241 ± 15] Bis(monothiothenoyltrifluoroacetonate)copper(II), Cu( ttfaS) 2 −1405.7 ± 8.3 [177 ± 15]

Adducts of antimony triiodide and 2-aminomethylpyridines: Synthesis, characterization and thermochemistry

Solid adducts of formula SbI 3·L [L = 2-amino-3-methylpyridine (2A3P), 2-amino-4-methylpyridine (2A4P), 2-amino-5-methylpyridine (2A5P), 2-amino-6-methylpyridine (2A6P)] were synthesized and characterized by elemental analysis, IR spectroscopy, thermogravimetry and DSC. Thermochemical parameters of the adducts were determined through solution-reaction calorimetry. The ratio metal–ligand was 1:1 for all adducts based on elemental analysis. Infrared results showed that the ligands coordinate to antimony through the nitrogen atom of the aromatic ring. Thermal degradation of adducts starts at 112, 122, 188, and 137 °C for SbI 32A xP (where x = 3, 4, 5 and 6, respectively). Decomposition temperatures correlate with metal–ligand bond strength. The enthalpy of reaction: SbI 3(c) + nL(c,l) = SbI 3· nL (solid) Δ r H m ° ( solid ) is −97.45, −56.43, −73.56 and −81.45 kJ mol −1, respectively, for 2A3P, 2A4P, 2A5P and 2A6P adducts. The standard enthalpies of decomposition, as well as the lattice enthalpies and the enthalpies of the Lewis acid–base reaction in the gas phase were calculated through thermochemical cycles. The standard mean antimony-nitrogen bond enthalpies in SbI 3·2A3P, SbI 3·2A4P, SbI 3·2A5P, and SbI 3·2A6P were estimated as 175, 135, 154, and 164 kJ mol −1, respectively.