Ligands For Transition Metals Research Articles

ChemInform Abstract: N‐Heterocyclic Carbenes (NHCs) as Organocatalysts and Structural Components in Metal‐Free Polymer Synthesis

AbstractReview: 261 refs.

ChemInform Abstract: Application of 1,2,3‐Triazolylidenes as Versatile NHC‐Type Ligands: Synthesis, Properties, and Application in Catalysis and Beyond

AbstractReview: 69 refs.

Group 5 Imides and Bis(imide)s as Selective Hydrogenation Catalysts

AbstractIn this microreview, we focus on our work on the development of group 5 imido and bis(imido) semihydrogenation catalysts in the context of previous stoichiometric studies on d0 metal–ligand multiple‐bond activations of strong σ bonds and both stoichiometric and catalytic studies on H2 activation and hydrogenation by d2 group 5 complexes. These studies develop electronic structure models and mechanistic analyses necessary for the application of catalytic reactions involving 1,2‐addition reactions of σ‐bonded substrates across early transition metal–ligand multiple bonds. Extension of these studies to the second and third row group 5 imido complexes has led to the development of mechanistically distinct hydrogenation catalysts with product selectivities not readily obtainable with traditional late transition‐metal catalysts that employ H2 as the reductant.

N-Heterocyclic carbenes (NHCs) as organocatalysts and structural components in metal-free polymer synthesis

The chemistry of N-heterocyclic carbenes (NHCs) has witnessed tremendous development in the past two decades: NHCs have not only become versatile ligands for transition metals, but have also emerged as powerful organic catalysts in molecular chemistry and, more recently, in metal-free polymer synthesis. To understand the success of NHCs, this review first presents the electronic properties of NHCs, their main synthetic methods, their handling, and their reactivity. Their ability to activate key functional groups (e.g. aldehydes, esters, heterocycles, silyl ketene acetals, alcohols) is then discussed in the context of molecular chemistry. Focus has been placed on the activation of substrates finding analogies with monomers (e.g. bis-aldehydes, multi-isocyanates, cyclic esters, epoxides, N-carboxyanhydrides, etc.) and/or initiators (e.g. hydroxy- or trimethylsilyl-containing reagents) employed in such "organopolymerisation" reactions utilizing NHCs. A variety of metal-free polymers, including aliphatic polyesters and polyethers, poly(α-peptoid)s, poly(meth)acrylates, polyurethanes, or polysiloxanes can be obtained in this way. The last section covers the use of NHCs as structural components of the polymer chain. Indeed, NHC-based photoinitiators, chain transfer agents or functionalizing agents, as well as bifunctional NHC monomer substrates, can also serve for metal-free polymer synthesis.

Application of 1,2,3-triazolylidenes as versatile NHC-type ligands: synthesis, properties, and application in catalysis and beyond

Triazolylidenes have rapidly emerged as a powerful subclass of N-heterocyclic carbene ligands for transition metals. They are readily available through regioselective [2 + 3] cycloaddition of alkynes and azides and subsequent metallation according to procedures established for related carbenes. Due to their mesoionic character, triazolylidenes are stronger donors than Arduengo-type imidazol-2-ylidenes. Spurred by these attractive attributes and despite their only recent emergence, triazolylidenes have shown major implications in catalysis. This feature article summarises the synthetic accessibility of triazolylidene metal complexes and their electronic and structural characteristics, and it compiles their applications, in particular, as catalyst precursors for various bond forming and redox reactions, as well as first approaches into photophysical and biochemical domains.

Synthesis, Spectroscopic Characterisation, and Biopotential and DNA Cleavage Applications of Mixed Ligand 4‐N,N‐Dimethylaminopyridine Metal Complexes

The mixed ligand transition metal complexes of 4‐N,N‐dimethylaminopyridine (DP) and chloride as primary and secondary ligands with the general formula [M(DP)3Cl3]; M = Cr(III) and Fe(III); [M′(DP)4Cl2]M′ = Co(II), Ni(II), Cu(II), and Cd(II) were synthesized in a microwave oven. The complexes were characterized by FT‐IR and UV, 1HNMR, 13CNMR spectra, TG/DTG, and various physicoanalytical techniques. From the magnetic moment measurements and the electronic spectral data, a distorted octahedral geometry was proposed for the complexes. The complexes express similar trend of thermal behaviour such that they lose water of hydration initially with the subsequent emission of organic and inorganic fragments and leave left the metal oxides as residue. The activation thermodynamic parameters, such as E*, ΔH*, ΔS*, and ΔG* of the metal complexes, illustrate the spontaneous formation of the complexes. The antimicrobial studies against various pathogenic bacterial and fungal serums insist on that the enhanced potential of the complexes over their ligand and their biopotential properties increases with concentration. The DNA interaction of the synthesized complexes on CT‐DNA was investigated by UV‐Vis spectroscopy, viscosity, thermal denaturation, and electroanalytical experiments and their binding constants (Kb) were also calculated.

A Theory for Bioinorganic Chemical Reactivity of Oxometal Complexes and Analogous Oxidants: The Exchange and Orbital-Selection Rules

Over the past decades metalloenzymes and their synthetic models have emerged as an area of increasing research interest. The metalloenzymes and their synthetic models oxidize organic molecules using oxometal complexes (OMCs), especially oxoiron(IV)-based ones. Theoretical studies have helped researchers to characterize the active species and to resolve mechanistic issues. This activity has generated massive amounts of data on the relationship between the reactivity of OMCs and the transition metal's identity, oxidation state, ligand sphere, and spin state. Theoretical studies have also produced information on transition state (TS) structures, reaction intermediates, barriers, and rate-equilibrium relationships. For example, the experimental-theoretical interplay has revealed that nonheme enzymes carry out H-abstraction from strong C-H bonds using high-spin (S = 2) oxoiron(IV) species with four unpaired electrons on the iron center. However, other reagents with higher spin states and more unpaired electrons on the metal are not as reactive. Still other reagents carry out these transformations using lower spin states with fewer unpaired electrons on the metal. The TS structures for these reactions exhibit structural selectivity depending on the reactive spin states. The barriers and thermodynamic driving forces of the reactions also depend on the spin state. H-Abstraction is preferred over the thermodynamically more favorable concerted insertion into C-H bonds. Currently, there is no unified theoretical framework that explains the totality of these fascinating trends. This Account aims to unify this rich chemistry and understand the role of unpaired electrons on chemical reactivity. We show that during an oxidative step the d-orbital block of the transition metal is enriched by one electron through proton-coupled electron transfer (PCET). That single electron elicits variable exchange interactions on the metal, which in turn depend critically on the number of unpaired electrons on the metal center. Thus, we introduce the exchange-enhanced reactivity (EER) principle, which predicts the preferred spin state during oxidation reactions, the dependence of the barrier on the number of unpaired electrons in the TS, and the dependence of the deformation energy of the reactants on the spin state. We complement EER with orbital-selection rules, which predict the structure of the preferred TS and provide a handy theory of bioinorganic oxidative reactions. These rules show how EER provides a Hund's Rule for chemical reactivity: EER controls the reactivity landscape for a great variety of transition-metal complexes and substrates. Among many reactivity patterns explained, EER rationalizes the abundance of high-spin oxoiron(IV) complexes in enzymes that carry out bond activation of the strongest bonds. The concepts used in this Account might also be applicable in other areas such as in f-block chemistry and excited-state reactivity of 4d and 5d OMCs.

Synthesis of new chiral pyrylium salts and their phosphinine and pyridine derivatives

Despite their versatility, chiral pyryliums are almost unknown in the literature. Reported here is the synthesis of several new chiral pyrylium salts and the corresponding pyridines and phosphinines. This work more than doubles the number of reported chiral pyryliums, and also represents the first racemizable/epimerizable pyryliums. The derived phosphinines and pyridines represent rare α-chiral ligands for transition metals.

Photodissociation Dynamics of Gaseous CpCo(CO)2 and Ligand Exchange Reactions of CpCoH2 with C3H4, C3H6, and NH3

The photodissociation dynamics of CpCo(CO)(2) was studied in a molecular beam using photofragment translational energy spectroscopy with 157 nm photoionization detection of the metallic products. At 532 and 355 nm excitation, the dominant one-photon channel involved loss of a single CO ligand producing CpCoCO. The product angular distributions were isotropic, and a large fraction of excess energy appeared as product vibrational excitation. Production of CpCO + 2CO resulted from two-photon absorption processes. The two-photon dissociation of mixtures containing CpCo(CO)(2) and H(2) at the orifice of a pulsed nozzle was used to produce a novel 16-electron unsaturated species, CpCoH(2). Transition metal ligand exchange reactions, CpCoH(2) + L → CpCoL + H(2) (L = propyne, propene, or ammonia), were studied under single-collision conditions for the first time. In all cases, ligand exchange occurred via 18-electron association complexes with lifetimes comparable to their rotational periods. Although ligand exchange reactions were not detected from CpCoH(2) collisions with methane or propane (L = CH(4) or C(3)H(8)), a molecular beam containing CpCoCH(4) was produced by photolysis of mixtures containing CpCo(CO)(2) and CH(4).

Metal Complexes of Uracil Derivatives with Cytotoxicity and Superoxide Scavenging Activity

5-Substituted uracils were reported to be important core structure of diverse therapeutics. Herein, novel mixed ligand transition metal (Mn, Cu, Ni) complexes of 5-iodouracil (5Iu) with 8-hydroxyquinoline or 8HQ (1-3) and 5- nitrouracil (5Nu) with 8HQ (4-6) have been synthesized. The metal complexes 1-6 exert significant cytotoxicity against HepG2, A-549, HuCCA-1 and MOLT-3 cell lines. Particularly, the cytotoxicities of tested complexes against HepG2 cells show their IC50 values lower than the reference drug. Cu complex of 5Nu (5Nu-Cu-8HQ, 5) is the most potent and promising cytotoxic compound. Mn complex of 5Iu (5Iu-Mn-8HQ, 1) is shown to be the most potent antioxidant. This finding reveals the application of using simple and commercially available bioactive ligands like 5Iu, 5Nu and 8HQ for the design and construction of new lead compounds with significant and promising bioactivities.

A Novel Type of Chiral Triangulane‐Based Diphosphane Ligands for Transition Metals

AbstractA new original strategy for the synthesis of axially and helically chiral bidentate diphosphane ligands featuring a rigid triangulanyl backbone has been elaborated and executed for several representative enantiomerically pure ligands. Thus,(1R,3S,4S)‐1,4‐bis[(diphenylphosphanyl)methyl]spiro[2.2]pentane [(1R,3S,4S)‐24·(BH3)2], [(1R,3R,4S)‐4‐(diphenylphosphanyl)methylspiro[2.2]pentan‐1‐yl]diphenylphosphane [(1R,3R,4S)‐27·(BH3)2], [(1R,3R,4S,5R)‐5‐(diphenylphosphanyl)methyldispiro[2.0.2.1]heptan‐1‐yl]diphenylphosphane [(1R,3R,4S,5R)‐30·(BH3)2], (1S,3S,4S)‐1,4‐bis(diphenylphosphanyl)spiropentane [(1R,3S,4S)‐35·(BH3)2], (1S,3S,4S)‐1,4‐bis(diphenylphosphanyl)spiropentane [(1S,3S,4S)‐35·(BH3)2], (1S,3S,4S)‐1,4‐bis(diphenylphosphanyl)spiropentane [(1R,3R,4S)‐35·(BH3)2], and (1R,3R,4R,5R)‐1,5‐bis(diphenylphosphanyl)dispiro[2.0.2.1]heptane [(1R,3R,4R,5R)‐36·(BH3)2] with a spiropentyl and a dispiro[2.0.2.1]heptyl moiety, respectively, have been prepared as bishydroborane complexes applying repetitively the same set of standard synthetic operations, starting from [(1S,3R)‐4‐methylenespiropent‐1‐yl]methyl acetate [(1S,3R)‐7], (4,4‐dibromospiropent‐1‐yl)methanols [(1S,3R)‐8 and (1R,3S)‐8] and (dibromodispiro[2.0.2.1]heptyl)methanols (1R,3S,4R)‐9, (1S,3R,4S)‐9 and (1S,3R,4R)‐9 in 4–7 steps. The relative configurations of all important intermediates as well as the absolute configurations of the key intermediates and most final products were established by X‐ray crystal structure analyses.

A New Class of Transition Metal Pincer Ligand: Tantalum Complexes that Feature a [CCC] X3-Donor Array Derived from a Terphenyl Ligand

A new class of [CCC] X(3)-donor pincer ligand for transition metals has been constructed via cyclometalation of a 2,6-di-p-tolylphenyl ([Ar(Tol(2))]) derivative. Specifically, addition of PMe(3) to [Ar(Tol(2))]TaMe(3)Cl induces elimination of methane and formation of the pincer complex, [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)MeCl (Tol' = C(6)H(3)Me), which may also be obtained by treatment of Ta(PMe(3))(2)Me(3)Cl(2) with [Ar(Tol(2))]Li. Solutions of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)MeCl undergo ligand redistribution with the formation of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)Me(2)and [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)Cl(2), which may also be synthesized by the reactions of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)MeCl with MeMgBr and ZnCl(2), respectively. Reduction of [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)Cl(2) with KC(8) in benzene gives the benzene complex [κ(3)-Ar(Tol'(2))]Ta(PMe(3))(2)(η(6)-C(6)H(6)) that is better described as a 1,4-cyclohexadienediyl derivative. Deuterium labeling employing Ta(PMe(3))(2)(CD(3))(3)Cl(2) demonstrates that the pincer ligand is created by a pair of Ar-H/Ta-Me sigma-bond metathesis transformations, rather than by a mechanism that involves α-H abstraction by a tantalum methyl ligand.

Synthesis, Characterization and Microbial Activity of Chiral Mixed Ligand Transition Metal Complexes

Chiral mixed ligand (CML) metal complexes are synthesized by using isonitrosopropiophenone (HINPP) as a primary ligand and saccharides such as (+)-glucose and/or (-)-fructose as a chiral secondary ligand. The metal complexes have been characterized by elemental analysis and various physico-chemical techniques such as molar conductance, magnetic susceptibility, electronic absorption, infrared spectral studies and thermal analysis. Room temperature magnetic susceptibility measurements of these complexes are indicative of a tetrahedral and/or octahedral geometry. The molar conductance studies of the complexes indicate their non-electrolytic nature. Electronic absorption/reflectance spectra of the complexes show intra- ligand, charge transfer, and the d-d transitions, consistent with their proposed geometry. Thermal studies show the presence of lattice water in the complexes. The specific rotation of the complexes is due to the corresponding chiral saccharide moiety. The Paper Disc Diffusion method has been used to study the antibacterial activity of the compounds against some of the pathogenic bacteria such as C. diphtheriae, E. coli, S. typhi, S. dysenteriae, S. aureus and V. cholerae. The antifungal activity of the complexes against some of the pathogenic fungi such as Candida albicans and Aspergillus niger has been studied by tube dilution method. The results have been compared against those of controls, which were screened simultaneously. The complexes have been screened for acute oral toxicity in albino rats.

Chiral allene-containing phosphines in asymmetric catalysis.

We demonstrate that allenes, chiral 1,2-dienes, appended with basic functionality can serve as ligands for transition metals. We describe an allene-containing bisphosphine that, when coordinated to Rh(I), promotes the asymmetric addition of arylboronic acids to α-keto esters with high enantioselectivity. Solution and solid-state structural analysis reveals that one olefin of the allene can coordinate to transition metals, generating bi- and tridentate ligands.

Theoretical and Experimental Analysis of Oxygen Separation from Air over Ni-Transition Metal Complexes

The separation of O2 from air over nickel-transition metal complexes has been studied using in situ infrared and Raman spectroscopy, thermogravimetric analysis, volumetric gas sorption, and quantum chemical simulation methods. Exposure of O2 to the solid Ni-transition metal complexes produces a reactive oxygen species at ambient temperatures. The infrared transient responses, during the absorption process, indicate that the ligand groups interact with oxygen, producing both weakly bound and strongly bound oxygen species. The results indicate that the reactive oxygen interacts weakly with the cyanide ligand groups, which are easily removed during the pressure swing absorption/desorption process at 298 K and 689.5 kPa. Temperature-programmed desorption revealed that the oxygen absorbed at the Ni center was bound stronger than the ligand-bound oxygen, evidenced by its removal at 393 K and the disappearance of a hydrogen-bonded species. The results obtained for the absorption/desorption process suggest that the persistence of the activated oxygen and reactivity with the transition metal ligands are an important factor for improving the absorption capacity of the organometallic sorbent. The in situ infrared spectroscopy study reveals the chemical structure of the ligand groups acting as adsorption sites for the reversible O2 uptake of the Ni-transition metal complex; the ligand-O2 interaction is an important factor for air separation sorbent development using organometallic complexes.

A Brief Survey of Our Contribution to Stable Carbene Chemistry

This personal account summarizes our work, beginning with the discovery of the first stable carbene in 1988 up until the recent isolation of mesoionic carbenes. It explains why we have moved our focus from acyclic to cyclic carbenes, and shows that these stable species are not limited to the role of ligand for transition metals, but that they are also powerful agents for the activation of small molecules, and for the stabilization of highly reactive diamagnetic and paramagnetic species.

Sodium and Potassium Salts of Mono‐ and Dianionic α‐Iminopyridines

a-Diimine (1,4-diaza-1,3-butadiene) ligands are well established in main-group, transition-metal, and lanthanide chemistry. Beside their application as ligands for latetransition-metal complexes, which can function as active and selective catalysts for a-olefin polymerization, a-diimine and related ligands are of special interest due to their ability to undergo redox chemistry. They have frequently been described as “non-innocent” ligands. For example, in lanthanide chemistry, it has been found that the formal oxidation state of Eu and Yb depends on the nature of the substituents on the a-diimine ligand and on the ligand on the metal center. Thus, in both cases, the a-diimine acts either as neutral ligand or as radical anion. Reduction of adiimines, using either alkali metals or electrochemical methods, leads in each case to the corresponding radical anions and eventually to diamagnetic dianions, albeit at much more negative potentials. In contrast to the well-established chemistry of a-diimines, the related a-iminopyridines are much less investigated. The three different redox states of a-iminopyridines are shown in Scheme 1. The neutral system L has been extensively used as ligand for late transition metals. Only recently, the monoanion LC and the doubly reduced dianion L were investigated as ligands in more detail. Recent reports showed a series of bis(a-iminopyridine)–metal complexes featuring aluminum and the first-row transition ions (Cr, Mn, Fe, Co, Ni, and Zn) with the monoanionic, and thus paramagnetic p-radical form of the ligand in coordination complexes. The a-iminopyridine N-2,6-diisopropylphenylimino-2-pyridine (IPy) has also been introduced in lanthanide chemistry. In this context, a potassium derivative of the monoanionic form of a-iminopyridine was prepared in situ, but not further characterized. The doubly reduced dianion has only been observed in two magnesium complexes so far. In contrast, the reaction of “GaI” with a-iminopyridine leads to reductive coupling of the coordinated ligand to give neutral diamido-digallium complexes. Based on this information, we were interested in a comprehensive study of the properties of the alkali metal salts of the monoanionic p-radical and the doubly reduced dianion of a-iminopyridine in solution and in the solid state. We report here the synthesis, characterization and magnetic properties of sodium and potassium salts of the monoand dianionic a-iminopyridines. N-2,6-Diisopropylphenylimino-2-pyridine (IPy) was prepared according to literature procedures. As a first entry point, we examined the electrochemical properties of IPy using cyclic voltammetry at room temperature in THF. As can be seen from Figure 1, we detected a quasi-reversible one-electron reduction process centered at E1=2= 2.57 V (vs. the ferrocene/ferrocenium couple, Fc/Fc), with a peakto-peak separation of 158 mV and ipa/ipc 1. It is reasonable to assume that this reduction process furnishes the radical anion LC . In addition, we observed two irreversible reduction processes at more negative values of Epc= 3.12 and 3.44 V, respectively. Based on these data we speculated that reactions of IPy with alkali metals should yield the radical anion LC and eventually the dianion L . Indeed, the reaction of IPy with one equivalent of metallic potassium in THF or diethyl ether resulted in the formation of dimeric, p-radical monoanionic potassium salts [{K ACHTUNGTRENNUNG(thf)2IPy}2] (1) and [{KACHTUNGTRENNUNG(Et2O)IPy}2] (2), respectively (Scheme 2). As evidenced by NMR spectroscopy, an excess of potassium surprisingly does [a] Dr. H. P. Nayek, Dipl.-Chem. N. Arleth, Dipl.-Chem. I. Trapp, Dipl.-Chem. M. Lcble, Dr. P. OCa-Burgos, M. Sc. M. Kuzdrowska, Dr. Y. Lan, Prof. Dr. A. K. Powell, Prof. Dr. F. Breher, Prof. Dr. P. W. Roesky Institut f r Anorganische Chemie Karlsruhe Institute of Technology (KIT) Engesserstrasse 15, 76131 Karlsruhe (Germany) Fax: (+49)721-6084-4854 E-mail : breher@kit.edu roesky@kit.edu [b] Dr. H. P. Nayek Present address: Department of Applied Chemistry Indian School of Mines, Dhanbad-826004 (India) [c] M. Sc. M. Kuzdrowska Helmholtz Research School Energy-Related Catalysis Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201101646. Scheme 1. Different redox state of a-iminopyridines.

Nitrenium ions as ligands for transition metals

Unlike N-heterocyclic carbenes (NHCs), which are now used ubiquitously in metal-based chemistry, the nitrogen-derived analogue (in which a carbon is replaced with the isoelectronic nitrogen cation, a nitrenium ion) has remained elusive as a ligand for metals. This is especially intriguing, because several other main-group analogues of NHCs have been prepared, and have been shown to coordinate with transition-metal complexes. Here, we describe the preparation of several N-heterocyclic nitrenium ions that are isoelectronic and isostructural to NHCs, and study their ligand properties. The formation of relatively strong nitrenium-metal bonds is unambiguously confirmed, in solution by selective (15)N-labelling experiments, and in the solid state by X-ray crystallography. Experimental and computational studies of the electronic properties of this novel type of ligand suggest that they are poor σ-donors and good π-acceptors.

Atomic Layer Deposition of Tantalum Nitride Using A Novel Precursor

We use B3LYP hybrid density functional theory to investigate atomistic mechanisms for the atomic layer deposition (ALD) of tantalum nitride (TaN) grown using tert-butylimidotris(diethylamido)tantalum [(tBuN)(NEt2)3Ta, TBTDET], and ammonia (NH3) as precursors. Our calculations examine various possible mechanisms for TaN growth by ALD and metal organic chemical vapor deposition (MOCVD). In particular, we identify low barrier (10.6 and 27.6 kcal/mol) ligand exchange mechanisms with NH3 that lead to incorporation of NH3’s nitrogen into the film. Ligand exchange with NH3 is thermodynamically and kinetically favored over competing mechanisms that incorporate nitrogen from the metal precursor including: β-hydrogen elimination of isobutene or ethene; and NH3 catalyzed β-hydrogen elimination of isobutene or ethene. β-hydrogen elimination of isobutene or ethene is found to proceed through a barrier of 76.0 kcal/mol. However, our results indicate that ammonia or diethylamine produced by precursor reaction with surface amine groups can also catalyze β-hydrogen elimination of isobutene with a predicted barrier of 64.3 kcal/mol, thus making MOCVD reactions kinetically active above ∼600 °C. In addition to providing a fundamental understanding of the chemistry of TaN ALD from (tBuN)(NEt2)3Ta and NH3, the set of mechanisms analyzed provide new insights into the principles governing the ALD processes of other metal nitride films using imido or amido ligand transition metal complexes and ammonia as precursors.

Thermogravimetric evaluation of decomposition kinetics of metal surfactant complexes

Thermal behavior of various synthesized transition metal surfactant complexes of the type [M(CH3COO)4]2−[C12H25NH3 +]2 where M: Cu(II), Ni(II), Co(II) has been investigated using Thermogravimetric Analysis (TGA). It was found that pyrolytic decomposition occurs with melting in metal complexes, and that metal oxides remain as final products. The activation energy order obtained, E Cu > E Ni > E Co, could be explained on the basis of size of transition metal ion and metal ligand bond strength. In the course of our investigation on the decomposition of complexes, we carried out a comparative study of different measurement and calculation procedures for the thermal decomposition. A critical examination was made of the kinetic parameters of non-isothermal thermoanalytic rate measurement by means of several methods such as Coats–Redfern (CR), Horowitz–Metzger (HM), van Krevelen (vK), Madhusudanan–Krishnan–Ninan (MKN), and Wanjun–Yuwen–Hen–Cunxin (WYHC). The most appropriate method among these was determined for each decomposition step according to the least-squares linear regression. It was found that the results obtained using CR method differ considerably from HM method, as the former method involves a lot of approximations and is not much reliable. The application of thermoanalytic techniques to the investigation of rate processes has also been discussed.