N. S. Kurnakov’s contribution to coordination chemistry

ISSN 0036�0236, Russian Journal of Inorganic Chemistry, 2010, Vol. 55, No. 11, pp. 1680–1685. © Pleiades Publishing, Ltd., 2010.Original Russian Text © N.T. Kuznetsov, 2010, published in Zhurnal Neorganicheskoi Khimii, 2010, Vol. 55, No. 11, pp. 1777–1783.

1680

The works by N.S. Kurnakov cover nearly all fieldsof general and inorganic chemistry. However, Kurna�kov’s name is most often associated with his latest fun�damental research that gave birth to the discipline thathe called physicochemical analysis [1–4]. As the orig�inator of physicochemical analysis, he laid the scien�tific foundations for the preparation and characteriza�tion of metal alloys and for the study of natural saltdeposits of the Soviet Union. Kurnakov’s earlierworks, which dealt with the chemistry of the platinumgroup and other transition metals, are known to amuch lesser extent, even though they have played agreat role in the development of coordination chemis�try by providing a large amount of experimental dataand by making a significant contribution to the generaltheory of coordination chemistry. Kurnakov is actuallythe originator of systematic research in platinum metalchemistry in Russia and the founder of the domesticplatinum production technology and platinum indus�try. However, this area of inorganic chemistry andtechnology did not occupy a significant place amonghis later scientific interests, even after he succeededL.A. Chugaev as Director of the Institute for Platinumand Other Noble Metals. Nevertheless, AcademicianI.I. Chernyaev noted that “Even if N.S. Kurnakov haddone nothing else but his early studies in coordinationchemistry, his name would not have been forgotten.These studies have played a paramount role in thedevelopment of coordination chemistry” [2, 5]. Thesestudies by Kurnakov concurred with the origination ofA. Werner’s theory of coordination compounds [6, 7].

Kurnakov’s interest in the chemistry of coordina�tion compounds, which were then called molecularcompounds, is likely due to the influence D.I. Men�deleev, who always advised researchers, especiallyyoung ones, to develop this area of inorganic chemis�try. In his classical work The Principles of Chemistry, hewrote that “ignoring this class of compounds, whichare called molecular compounds, would mean deny�ing the basic properties of the atoms constituting these

compounds” [7]. In the 1890s, these compoundsattracted special attention not only from D.I. Men�deleev, but also from other prominent chemists both inRussian and abroad.

Kurnakov, a talented researcher, had broad scientificinterests and could address coordination compoundshimself even at the start of his scientific career, the moreso as these compounds were a new, actively developingsubject of inorganic chemistry.

In 1881, as a student of the Mining Institute, Kur�nakov carried out his first research work on alum crys�tallization and on sodium thioantimonate crystalhydrates [9], which are aqua complexes.

So it was not surprising that, after he accomplishedhis master’s dissertation on evaporation systems ofsalt�making plants in 1885 and took a long businesstrip inside Russia and to European countries to furtherinvestigate this problem, he returned to coordinationcompounds. As an applicant for the position of Profes�sor at the Department of Inorganic Chemistry of theMining Institute, he carried out a fundamental workentitled “On Complex Metal Bases” [10] and pre�sented it as a dissertation to the scientific council ofthis institution in 1893. This wok consists of the fol�lowing three chapters: (1) Views of the nature of com�plex metal bases. Some general properties of salts ofcomplex bases. Review of the present�day conceptionsof the structure of complex metal bases. (2) Complexmetal–thiocarbamide compounds. Platinum salts. (3)Structure of metal salts of thioamides.

Of course, these chemical names are outdated, butit should be remembered that Werner’s classical work“Beitrage zur Konstitution der anonarganischerVerbindungen” also appeared in 1893.

Kurnakov’s interest in platinum metal chemistry isquite natural. Platinum attracted attention from Kur�nakov because it was (and is now) among the greatestnatural treasures of our country. Throughout all hislifetime, Kurnakov was interested in the platinummetals and put great effort into study of these metals

N. S. Kurnakov’s Contribution to Coordination ChemistryN. T. Kuznetsov

Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia

Abstract—N.S. Kurnakov’s most important works in coordination chemistry are overviewed. Special atten�tion is given to Kurnakov’s dissertation “On Complex Metal Bases,” to his understanding of the structure ofcoordination compounds, to the mutual effects of ligands, and to the key ideas in coordination chemistrydeveloped by Chugaev and Chernyaev’s school. Kurnakov’s role in the foundation of the Soviet platinumindustry is pointed out.

DOI: 10.1134/S0036023610110033

RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 11 2010

N. S. KURNAKOV’S CONTRIBUTION TO COORDINATION CHEMISTRY 1681

and into the development of the national platinumproduction technology and platinum industry. Studiesin platinum group chemistry and technology in Russiawere at a fairly high scientific level at that time, prima�rily due to works by P.G. Sobolevskii, G.I. Gess,F.V. Vil’m, and, particularly, K.K. Klaus.

Kurnakov’s dissertation contained an analysis ofthe nature of platinum coordination compounds, acritical review of the existing structural theories ofthese compounds, and experimental data for platinumcomplexes with thiourea and thioacetamide. Themain distinctive feature of this work is its wide scopeand a comprehensive study of the objects of examina�tion. Kurnakov thoroughly studied the crystal struc�ture of the new compounds he synthesized and theirphysical and chemical properties: solubility, refrac�tion, acid–base properties, and reactivity toward vari�ous chemicals. Note that the structural theory of coor�dination compounds at that time was dominated bythe chain theory of Blomstrand–Jorgensen and thenew theory of Werner was just gaining recognition inscience. Kurnakov did not accept the old theory, buthe did not fully agree with Werner’s theory either. Hefound a grain of truth in both theories; at the sametime, he thought of them as being incapable ofexplaining the totality of data available on the subject.

His studies of platinum metal complexes lead Kur�nakov to the conclusion that “the assumption that theammonium and water species in complex salts arelinked in a chainlike fashion is inconsistent with theobserved facts” [10]. As for Werner’s theory [6, 7],Kurnakov recognized its significance, particularly itsstereochemical conceptions, which provided explana�tion for the isomerism of coordination compounds. Atthe same time, he pointed out this coordination theoryis formal to a certain extent because it ignores themutual effect of the inner�sphere species and theeffects of these species on the central atom. Kurna�kov’s fundamental study generated a variety of newideas, which later evolved into prominent studies byother researchers. For example, the idea of analogybetween complex and simple ions was developed byL.A. Chugaev in his works on platinum pentamminecomplexes. Kurnakov’s studies of the acid–base prop�erties of complexes were successfully continued byA.A. Grinberg and his pupils. Kurnakov’s ideas con�cerning the mutual effect of all species in the coordi�nation sphere were brilliantly corroborated byI.I. Chernyaev, who discovered the trans effect ofligands. An important topic of Kurnakov’s dissertationwas the structure of “complex bases” (coordinationcompounds). Kurnakov discovered that, in platinum–thiourea (SC(NH2)2) complexes, thiourea coordinatesto the central atom only through the sulfur atom.Investigating Pt(II) thiourea complexes, Kurnakovestablished the rule that made it possible to identify thecis and trans isomers of platinum diammine anddiamine complexes, [PtA2X2]. Later, this rule receivedthe name of Kurnakov’s rule. The earliest results of

this study were reported in 1889 at a meeting of theDepartment of Chemistry of the Russian Physical andChemical Society in the presence of D.I. Mendeleevand other prominent Russian chemists.

Kurnakov demonstrated that thiourea (L) reacts dif�ferently with cis and trans isomers of [PtA2Cl2] (A = NH3or amine):

Thus, the cis isomers exchange all their inner�sphere ligands for thiourea, while the trans isomersexchange only the acid residues. These reactionsclearly illustrate the mutual effect of ligands in thecoordination sphere.

Different geometric isomers also result from thereactions of potassium tetrachloroplatinate(II) withthiourea and ammonia:

By heating concentrated solutions of trans�[PtL2Cl2] with thiourea, it is possible to replace theother two chlorine atoms:

Kurnakov demonstrated that a similar reaction canbe carried out for pyridine (Py):

For various thiourea derivatives with the generalformulas SC(NH2)(NHR) and SC(NHR)(NHR) (R =CH3, C2H5, C6H5, etc.), Kurnakov demonstrated thatthese ligands show the same behavior in the substitu�tion reactions as thiourea. He proved that, in all plati�num complexes with thiourea and its derivatives, theligands are coordinated to the platinum atom throughthe sulfur atom rather than the nitrogen atom. Just thesame was suggested by the data available on the stabil�ity of the Pt–N bond.

These studies led Kurnakov to the conclusion thatthe ligands of thiourea and its derivatives, NH3,amines, Н2О, etc. in the inner coordination sphere ofthe complexes change the chemical functions of thecentral atom and those of the groups bonded to it.

Kurnakov’s works on platinum–thiourea com�plexes demonstrate that the scientist attached greatsignificance to the isomerism of coordination com�pounds. He wrote the following [11]: “The study ofisomers is among the most potent means to determinethe structure of chemical compounds. It is the study ofisomers that shaped present�day organic chemistry, andnumerous data suggest that investigation of the internalstructure of mineral compounds will go the same way.”This statement of Kurnakov was convincingly corrob�orated by researchers of Chugaev and Chernyaev’sschool. Investigating the reactions of platinum com�plexes with thiourea, Kurnakov put forward the inter�

[ ] [ ]+ = +� PtA Cl L PtL Cl A2 2 4 24 2 ,cis

[ ] [ ]+ =� PtA Cl L PtA L Cl2 2 2 2 22 .trans

[ ] [ ]+ = 2 2K PtCl L � PtL Cl + 2KCl,2 4 2 trans

[ ] ( )[ ]+ = +K PtCl NH � Pt NH Cl KCl2 4 3 3 222 2 .cis

[ ] [ ]+ =� PtL Cl L PtL Cl2 2 4 22 .trans

[ ] [ ]+ =� PtL Cl Py � PtL Py Cl2 2 2 2 22 .trans trans

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KUZNETSOV

esting idea that the chemical behavior of thiourea andits derivatives in the substitution reactions is explainedby the presence of the group S=C–N and this why the

thioamides , and the thio�

urethanes possess the same properties

[12]. The fact that thiourea, its derivatives (thioure�thanes and thioamides), ammonia, amines, and waterare coordinatively equivalent, discovered by Kurna�kov, played a significant role in the establishment ofthe rule of rings by Chugaev. These Kurnakov’s workson the reactions of platinum complexes with function�alized organic compounds were later developed byChugaev into a separate area of synthetic coordinationchemistry. Some other conclusions made by Kurnakovin his classical work also deserve attention. For exam�ple, he correlated the solubility of complexes and thechemical lability of their acid residues with theirhydration and dehydration. In most cases, the libera�tion of constitutional water makes the substance lesssoluble. The release of water of crystallization exertsthe opposite effect.

Kurnakov’s work “On Complex Metal Bases” is aclassic for coordination chemists and has won widerespect. Knowledge of this work seems to be desirablefor any researcher carrying out in�depth studies incoordination chemistry. Kurnakov’s conclusion thatthiourea and ammonia can replace each other inter�ested Mendeleev so greatly that he included Kurna�kov’s data into his book The Principles of Chemistry[12] (chapter dealing with platinum–ammonia com�pounds). Four years after the appearance of this work,Kurnakov published a very interesting work entitled“On the Correlation between the Color and Structureof Double Halide Salts” [13]. It was devoted to the“increase” in color (passage from the red to the violetpart of the spectrum) caused by the introduction ofammonia and other ligands into the coordinationsphere. Kurnakov considered two series of isomericcompounds, namely, [Pt(NH3)4][MCl4] (M = Cu, Zn,Cd, Co, Hg, Pb) and [M(NH3)4][PtCl4] (M = Cu,Zn, Cd, Ni). The latter series of complexes is domi�nated by red color, which is typical of chloroplatinates.The color of the salts in the first series is determinedby the color of the respective anhydrous transitionmetal halide. Kurnakov synthesized an intermediateseries of complexes in which ammonia is differentlydistributed between the two coordination spheres:[Pt(NH3)4 – xClx][M(NH3)xCl4 – x]. Here, the color ofthe resulting complexes was explicable in terms of theadditivity of the colors of the components. Systemati�cally varying the ammonia distribution, it is possible topredict the color of the resulting complex, and viceversa. Kurnakov extended his principle of “decreas�ing” and “increasing” color to other types of coordi�

S CR

NH2

S CNHR

NHR

COR

NH2

S

nation compounds, including complex halides andaqua complexes. He demonstrated that the complexesexist in solution in undecomposed form and, veryimportantly, pass into the solid state in the same from.This result was later confirmed by X�ray diffractiondata for crystals of coordination compounds.

Based on these studies, Kurnakov suggested thatisomers can be identified as the color of their crystals.Note that, at that time, there was no X�ray crystallog�raphy and spectroscopic methods of determining thestructure of coordination compounds. In addition tosystematically investigating the color of complexes,Kurnakov calculated the atomic refraction for plati�num compounds to verify his idea. These calculationsdemonstrated that this quantity varies from one plati�num compound to another and thus proved that thestates of platinum in solution vary widely, dependingon the composition of the complex. For example, theintroduction of ammonia into a complex changes theatomic refraction of platinum to a significant extent.Examining the stability of coordination compounds,Kurnakov established that the energy of a complexbase decreases as the relative energy and the number ofbasic groups in the complex decrease. Studying themutual solubility of platinum diammines and tetram�mines, Kurnakov discovered the formation of solidsolutions [11]. For example, the cocrystallization of[Pt(NH3)2Cl2] and [Pt(NH3)4]Cl2 yields the double salt[Pt(NH3)2Cl2] ⋅ 4[Pt(NH3)4]Cl2. The crystallization ofthe complex [Pt(NH3)4]Cl2 under conditions of slowwater evaporation yields both the initial tetrammine�platinum(II) chloride and crystals of the solid solution[Pt(NH3)2Cl2] ⋅ 4[Pt(NH3)4]Cl2 in [Pt(NH3)4]Cl2. Asdistinct from tetrammineplatinum(II) chloride, whichis colorless, the solid solution is brownish yellow orreddish brown. The similarity of the chemical compo�sitions and crystallographic properties of these com�pounds makes possible their cocrystallization. Crys�tallization in an ammonia atmosphere yields colorlesscrystals of [Pt(NH3)4]Cl2. These works on platinumtetrammines were interesting to Kurnakov from thestandpoint of the formation of different nonstoichio�metric phases—the area of chemistry on which hisscientific activity was focused in later years.

Kurnakov and his colleagues performed interestingstudies into complexes of palladium, which in theiropinion “provided a link between the platinum groupand the family of Cu, Ni, and Ag” [14]. They synthe�sized new ethylenediamine complexes of palladium:

The latter compound, unlike its platinum counterpart,releases one En molecule when exposed to dilutehydrochloric acid and is converted to a sparingly solu�ble neutral complex:

[ ][ ]K PdCl En PdEn PdCl2 4 2 42 ,+ =

[ ][ ] [ ]PdEn PdCl En PdEn Cl2 4 2 22 2 .+ =

[ ] [ ]PdEn Cl HCl PdEnCl En HCl2 2 2 .+ = + ⋅



The reaction with concentrated HCl occurs in a dif�ferent way:

For this compound, there is temperature�dependentdynamic equilibrium:

The geometry of complexes was established in theirreaction with thiourea (L). For example,

This reaction verifies the cis configuration of[PdEnCl2] by analogy with cis�[PtA2Cl2], where Astands for various amines.

Studying ethylenediamine complexes of palla�dium, Kurnakov inferred that ethylenediaminebehaves in these substitutions like ammonia, pyridine,aniline, and other weak organic bases.

In his work entitled “The Reactivity of NickelChloride toward Ethylenediamine,” [15], Kurnakovdemonstrated that ethylenediamine complexes ofnickel in their stability are similar to the correspondingpalladium complexes and are considerably inferior toplatinum complexes, in which even ammonia is boundso strongly that it is not replaced not only by water, butalso by an acid. In other words, there is dynamic equi�librium in solutions of ethylenediamine complexesdetermined by the reactant concentrations:

Several Kurnakov’s works deal with complexes ofother non�platinum metals. Reacting AgNO3 withthiourea, Kurnakov isolated the complex[AgSC(NH2)2]NO3. In an excess of thiourea, thecoordination sphere of silver can contain a still greaternumber of thiourea molecules. By reacting hydrochlo�ric acid with [Ag(SC(NH2)2)3]NO3, the complex[Ag(SC(NH2)2)2]Cl was obtained [16].

When bromine was reacted with solutions of potas�sium and sodium molybdates containing smallamounts of cobalt(II), two series of salts wereobtained: light green crystals of composition 3К2О ·Со2О3 · 12МоО3 · 20Н2О and dark green crystals of3К2О · Со2О3 · 10МоО3 · 10Н2О [17]; CuBr2 and HgBr2in concentrated lithium bromide solutions yield lith�ium bromocuprite Li2[HgBr4] · 6H2O and lithium bro�momercurate Li2[CuBr4] · 6H2O, respectively [18]; thecrystallization of cobalt and manganese thiocyanatesalts from aqueous solution yielded black rhombiccrystals of Co(CNS)2 · 3H2O [19] and a number ofmanganese thiocyanate hydrates of compositionMn(CNS)2 · nH2O, where n = 2–4 [20].

Investigating hydration processes, Kurnakov withcolleagues established a correlation between hydrationand solubility in aqua complexes. Analyzing datareported by Le�Chatelier [21] and van’t Hoff [22],who established that compounds containing a smallernumber of crystal water molecules and anhydrous salts

[ ] [ ]PdEn Cl HCl EnH PdCl2 2 2 42 .+ =

[ ] [ ]EnH PdCl PdEnCl HCl2 4 2 2 .↔ +

[ ] [ ]PdEnCl L PdL Cl En2 4 24 .+ = +

[ ] ( )[ ]NiEn Cl H O NiEn H O Cl En.3 2 2 2 2 222+ ↔ +

must have higher solubilities than the higher hydrates,Kurnakov found that many hydrates do not obey thisrule. For example, Co, Cr, Ir, and Rh pentamminehalides and pentammine nitrates of composition[M(NH3)5H2O]X3 are always far more soluble than therespective anhydrous salts [M(NH3)5Х]X2, where X =halide ion. A similar situation was observed in compar�ing tetrammine halide salts of compositions[Co(NH3)4(H2O)X]X2 and [Co(NH3)4(H2O)2]X3.

In the salts under consideration, addition of waterincreases, while its elimination decreases, the solubil�ity of compounds, contrary to what was mentionedabove as regards hydrates containing crystal water. Thesame regularity was also observed by Kurnakov instudying other classes of complexes.

Solubility was studied as a function of temperaturefor various classes of complexes, and solubility curveswere found to be nearly rectilinear [23].

Kurnakov’s important contribution to coordina�tion chemistry was use of physicochemical analysis inthis field, further developed in the works of his disci�ples. In the work entitled “Equilibrium in the Na2Cl2–PtCl4–H2O System” [24], for example, it was foundthat the 25°С solubility isotherm has three branches,in accordance with the formation of three solid phases:Na2[PtCl6] ⋅ 6H2O,PtCl4 · 5H2O, and NaCl. The solubil�ity curve for sodium chloroplatinate does not feature asingular point, and the segment of the curve betweenthe double points of existence of solid phases (NaCl +Na2[PtCl6] ⋅ 6H2O and Na2[PtCl6] ⋅ 6H2O + PtCl4 ⋅

5H2O is a concave line. The ice field of this system istypical of neutralization�type systems. The isothermsare almost rectilinear, but at the point where the sys�tem’s composition is Na2[PtCl6] ⋅ 6H2O, they feature asharp kink to form an anticlinal�type singular fold. Atthe 2NaCl : PtCl4 = 1 : 1 point, there is a kink with atemperature peak of –7.6°С. Thus, the singular pat�tern of the ice field indicates the formation of the sta�ble complex Na2[PtCl6] ⋅ 6H2O. The studies of the sol�ubility diagram of this system at 40–98°С led to datavery different from those obtained for 25°С. There arethe same three branches; at the same time, theNa2[PtCl6] · 6H2O solubility curve features a sharppeak corresponding to Na2[PtCl6].

Kurnakov used physicochemical analysis in thework entitled “Ice Field in the FeCl3–HCl–H2O Sys�tem” [25]. The ice field in this system was studied by apolythermal technique. The polytherms are near rec�tilinear; isotherms for the ice field are also rectilinear.No stable compounds were observed in this system.The hydrochloride like HFeCl4 is an unstable com�pound. There is no evidence of the formation of newions in solution either. These facts are likely responsi�ble for the linearity of the ice field isotherms in theFeCl3–HCl–H2O system. A comparison betweenthese data and those obtained for the ice field in theNa2Cl2–PtCl4–H2O system showed that, in the case ofthe formation of sodium chloroplatinate (a stablecomplex), the ice field is characterized by an anticlinal

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KUZNETSOV

singular fold; when low�stability iron hydrochloridesare formed, there are no singular elements in the icefield. Kurnakov also studied the K2O–CrO3–H2O sys�tem [26]. An essential feature of this system is thatthere is no formation of tri� and tetrachromates in theice field. The solubility isotherms clearly indicate theformation of all these compounds. The absence of sin�gularities in the ice field is attributed the decomposi�tion of these compounds in aqueous solution. Forcomplex bases, Kurnakov showed that the strength ofa base and the solubilities of its compounds are inter�related; that is, they can be represented by diagramsresembling composition–property diagrams. TheseKurnakov’s views already contain the idea of correla�tion between all properties of a chemical compoundand the desire to reveal the nature of this correlation,later developed into the method of constructing achemical diagram via comprehensive studies of allproperties of the system.

Electrolyte�type aqueous systems with pronouncedchemical interactions supplement and expand thedoctrine of singular elements of chemical diagrams.Natural salt equilibria apart, the studies by Kurnakovand his disciples on water–salt equilibria may be clas�sified as follows: (a) studies in the field of double saltsthat form solid phases like carnallite, astrakhanite,schoenite, and other minerals; (b) studies in the fieldof the structure of three�dimensional folds and theirsingular elements, namely, neutral systems and sys�tems where strongly bonded complexes are formed;and (c) studies in the field of physicochemical sub�stantiation of the production of industrially importantcompounds and materials.

Kurnakov and his disciples studied many systemsof these three types. Examples are NH4Cl–MIICl2–H2O systems, where MII = Co(II), Ni(II), or Mn(II),and Na2SO4–MIISO4–H2O, where MII = Fe(II),Co(II), Ni(II), Mn(II), Cu(II), or Zn(II). In all cases,complexes were found to form, having various degreesof stability (they are frequently referred to as doublesalts) [27].

Kurnakov’s disciples widely used physicochemicalanalysis in their studies of complexation processes,especially Tananaev and his scientific school (specifi�cally, I.V. Tananaev’s residual concentrationsmethod). Many relevant data are recited inV.I. Mikheeva’s monograph entitled “Physicochemi�cal Analysis in Inorganic Chemistry” [28].

Certainly, Kurnakov recognized the importanceand prospects of coordination chemistry; however,later, even when he succeeded Chugaev as the head ofthe Institute for Platinum and Other Noble Metals,Kurnakov focused on metallic systems and salt equi�libria. Perhaps, he thought that physicochemical anal�ysis, his main scientific achievement, would be mostfruitful in these fields. Kurnakov apparently kept inmind that rational use of natural resources and the cre�ation of metallic construction materials is of para�mount importance for the USSR. At the same time,

even in studying metallic systems, he considered themas “the field of chemical compounds containing com�plexes (Mm) formed by coupling metals” [29]. Fromthis viewpoint, we can say that Kurnakov stood at theorigins of cluster chemistry.

Kurnakov was the first to view the chemistry ofplatinum metals from the standpoint of the chemistryof complexes, thus laying the foundation for laterworks by Chugaev and his school. These works eventu�ally made the Russian national school of coordinationchemistry the world’s leader in chemical science.

Kurnakov always held interest in the chemistry ofplatinum metals as regards both fundamental scienceand extensive use of the results of fundamental studies.It must be mentioned that Russia, having the richestresources of the platinum�group metals, was sellingalmost all of the produced platinum or was sending itabroad for refining as the crude metal for a song. Thiscertainly stirred Kurnakov, a patriot of his country. In1910, a commission for organizing the refining of Rus�sian platinum was created at the Mining Departmentand was headed by Kurnakov. In 1913–1914, a tech�nology was elaborated for processing crude platinumand obtaining the pure metal in Kurnakov’s laboratoryat the Mining Institute. This technology provided thebasis for building refineries. N.N. Baraboshkin, one ofthe closest Kurnakov’s colleagues, built a refinery inSverdlovsk and then was its technical director. Therebyit became possible to refine the platinum�group metalswithin the USSR and avoid exporting crude platinumand importing back refined metals [30]. In the early1920s, the Institute for Platinum and Other NobleMetals, especially while headed by Kurnakov, startedextensive research in the refining and analysis of theplatinum�group metals on the basis of the fundamen�tal research of their complexes. Kurnakov’s organiza�tional talent manifested itself in all its splendor. Atechnology was created for producing all pure plati�num�group metals, and their production facilitieswere organized. Thus, helped by Kurnakov’s organi�zational talent and wise leadership, the national plati�num group industry was created in Russia. All tech�nologies leaned upon the strong basis of the coordina�tion chemistry of the platinum�group metals, whosefoundations in Russia were laid by Kurnakov and hisfollowers.

REFERENCES

1. N. S. Kurnakov, The Introduction to PhysicochemicalAnalysis, 4th ed. (Akad. Nauk SSSR, Moscow, 1940)[in Russian].

2. Izv. Sekt. Fiz.�Khim. Anal. 14 (1941).3. Yu. I. Solov’ev and O. E. Zvyagintsev, Nikolai Semenovich

Kurnakov (Akad. Nauk SSSR, Moscow, 1960)[in Russian].

4. Yu. I. Solov’ev, Nikolai Semenovich Kurnakov (Nauka,Moscow, 1986) [in Russian].

5. I. I. Chernyaev, Izv. Sekt. Platiny, No. 21, 7 (1948).



6. A. Werner, Z. Anorg. Chem. 3, 267 (1893).7. A. Verner, New Views in Inorganic Chemistry (ONTI�

Khimteoret., Leningrad, 1936) [in Russian].8. D. I. Mendeleev, The Fundamentals of Chemistry

(St. Petersburg, 1871), p. 842 (1871) [in Russian].9. N. S. Kurnakov, Zap. St�Pb. Mineral. O�va,

Ser. P. 4.16, p. 310, 331 (1881).10. N. S. Kurnakov, On Complex Metallic Bases, (a) Zh.

Russ. Fiz.�Khim. O�va, No. 25, 565, 693 (1893); (b)Collection of Selected Works (ONTI�Khimteoret., Len�ingrad, 1938), p. 7, Vol. 1; (c) Works on the Chemistry ofCoordination Componds (Akad. Nauk SSSR, Moscow,1963) [in Russian].

11. (a) N. S. Kurnakov and I. A. Andreevskii, Izv. Inst.Platiny, No. 7, 161 (1929); (b) N. S. Kurnakov, Workson the Chemistry of Complex Compounds (Akad. NaukSSSR, Moscow, 1963), p. 99 [in Russian].

12. D. I. Mendeleev, The Fundamentals of Chemistry(St. Petersburg, 1889), p. 781 [in Russian].

13. (a) N. S. Kurnakov, Zh. Russ. Fiz.�Khim. O�va,No. 29, 706 (1897); (b) N. S. Kurnakov, Z. Anorg.Shem. 17, 207 (1898); (c) N. S. Kurnakov, Works on theChemistry of Complex Compounds (Akad. Nauk SSSR,Moscow, 1963), p. 99 [in Russian].

14. (a) N. S. Kurnakov and N. I. Gvozdarev, Zh. Russ.Fiz.�Khim. O�va, No. 29, 706 (1897); (b) N.S. Kurna�kov, Works on the Chemistry of Complex Compounds(Akad. Nauk SSSR, Moscow, 1963), p. 126 [in Rus�sian].

15. (a) N. S. Kurnakov, Zh. Russ. Fiz.�Khim. O�va,No. 31, 688 (1899); (b) N.S. Kurnakov, Z. Anorg.Shem. 22, 466 (1900); (c) N. S. Kurnakov, Works on theChemistry of Complex Compounds (Akad. Nauk SSSR,Moscow, 1963), p. 123 [in Russian].

16. (a) N. S. Kurnakov, Zh. Russ. Fiz.�Khim. O�va,No. 23, 559 (1891); (b) N. S. Kurnakov, Works on theChemistry of Complex Compounds (Akad. Nauk SSSR,Moscow, 1963), p. 9 [in Russian].


18. (a) N. S. Kurnakov and V. Ya. Budakov, Zh. Russ.Fiz.�Khim. O�va, No. 30, 324 (1898); (b) N. S. Kurna�kov, Works on the Chemistry of Complex Compounds(Akad. Nauk SSSR, Moscow, 1963), p. 119 [in Rus�sian].


20. (a) N. S. Kurnakov and P. P. Veimarn, Zh. Russ.Fiz.�Khim. O�va, No. 34, 518 (1902; (b) N. S. Kurna�kov, Works on the Chemistry of Complex Compounds(Akad. Nauk SSSR, Moscow, 1963), p. 130 [in Rus�sian].

21. Le Chatelier, Recherches experimentales et theoriquessur les equilibres chimiques (Paris, 1888).

22. I. H. Van’t�Hoff, Arch. Neerland, No. 20, 63 (1886).


24. N. S. Kurnakov and E. A. Nikitina, Zh. Obshch.Khim., No. 10, 577 (1940); (b) N. S. Kurnakov, Workson the Chemistry of Complex Compounds (Akad. NaukSSSR, Moscow, 1963), p. 142 [in Russian].

25. (a) N. S. Kurnakov and E. A. Nikitina, Izv. Akad. NaukSSSR, Ser. Khim., No. 2, 433 (1938); (b) N. S. Kurna�kov, Works on the Chemistry of Complex Compounds(Akad. Nauk SSSR, Moscow, 1963), p. 138 [in Rus�sian].

26. N. S. Kurnakov and M. I. Ravich, Izv. Sekt. Fiz.�Khim.Anal. 10, 211 (1935).

27. M. I. Ravich, Izv. Sekt. Fiz.�Khim. Anal. 14, 113(1941).

28. V. I. Mikheeva, The Method of Physicochemical Analysisin Inorganic Synthesis (Nauka, Moscow, 1975) [in Rus�sian].

29. N. S. Kurnakov, Collection of Selected Works (ONTI�Khimteoret, Leningrad, 1938), Vol. 1 [in Russian].

30. O. E. Zvyagintsev, Izv. Sekt. Platiny, No. 28, 133 (1954).

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N. S. Kurnakov’s contribution to coordination chemistry