Complex compounds

Summary of the lesson-lecture

Goals. Form an idea of ​​the composition, structure, properties and nomenclature of complex compounds; develop skills for determining the oxidation state of a complexing agent, drawing up equations for the dissociation of complex compounds.
New concepts: complex compound, complexing agent, ligand, coordination number, external and internal spheres of the complex.
Equipment and reagents. A rack with test tubes, concentrated ammonia solution, solutions of copper (II) sulfate, silver nitrate, sodium hydroxide.

DURING THE CLASSES

Laboratory experience. Add ammonia solution to the copper (II) sulfate solution. The liquid will turn intense blue.

What happened? Chemical reaction? Until now, we did not know that ammonia can react with salt. What substance was formed? What is its formula, structure, name? To what class of compounds can it be attributed? Can ammonia react with other salts? Are there any connections similar to this? We have to answer these questions today.

To better study the properties of some compounds of iron, copper, silver, aluminum, we need knowledge about complex compounds.

Let's continue our experience. Divide the resulting solution into two parts. Add alkali to one part. The precipitation of copper (II) hydroxide Cu (OH) 2 is not observed, therefore, there are no doubly charged copper ions in the solution or there are too few of them. Hence, we can conclude that copper ions interact with the added ammonia and form some new ions that do not give an insoluble compound with OH - ions.

At the same time, the ions remain unchanged. This can be verified by adding a solution of barium chloride to the ammonia solution. A white precipitate of BaSO 4 will precipitate immediately.

Studies have established that the dark blue color of the ammonia solution is due to the presence of complex 2+ ions in it, formed by the addition of four ammonia molecules to the copper ion. When water evaporates, ions 2+ bind with ions, and dark blue crystals are released from the solution, the composition of which is expressed by the formula SO 4 H 2 O.

Complex compounds are those containing complex ions and molecules capable of existing both in crystalline form and in solutions.

Formulas of molecules or ions of complex compounds are usually enclosed in square brackets. Complex compounds are obtained from conventional (non-complex) compounds.

Examples of obtaining complex compounds

The structure of complex compounds is considered on the basis of the coordination theory proposed in 1893 by the Swiss chemist Alfred Werner, a Nobel Prize winner. His scientific activities took place at the University of Zurich. The scientist synthesized many new complex compounds, systematized previously known and newly obtained complex compounds and developed experimental methods for proving their structure.

A. Werner (1866–1919)

In accordance with this theory, complex compounds are distinguished complexing agent, external and inner sphere... The complexing agent is usually a cation or neutral atom. The inner sphere is made up of a certain number of ions or neutral molecules, which are firmly bound to the complexing agent. They are called ligands... The number of ligands determines coordination number(CN) complexing agent.

Complex compound example

The compound SO 4 H 2 O or CuSO 4 5H 2 O considered in the example is a crystalline hydrate of copper (II) sulfate.

Let us determine the constituent parts of other complex compounds, for example, K 4.
(Reference. The substance with the formula HCN is hydrocyanic acid. Hydrocyanic acid salts are called cyanides.)

Complexing agent - iron ion Fe 2+, ligands - cyanide ions СN -, coordination number is equal to six. Everything in square brackets is an inner sphere. Potassium ions form the outer sphere of the complex compound.

The nature of the bond between the central ion (atom) and ligands can be twofold. On the one hand, the bond is due to the forces of electrostatic attraction. On the other hand, between the central atom and ligands a bond can be formed by the donor-acceptor mechanism by analogy with the ammonium ion. In many complex compounds, the bond between the central ion (atom) and the ligands is due to both the forces of electrostatic attraction and the bond formed due to the lone electron pairs of the complexing agent and free orbitals of the ligands.

Complex compounds with an outer sphere are strong electrolytes and in aqueous solutions dissociate almost entirely into a complex ion and ions outer sphere. For example:

SO 4 2+ +.

In exchange reactions, complex ions pass from one compound to another without changing their composition:

SO 4 + BaCl 2 = Cl 2 + BaSO 4.

The inner sphere can have a positive, negative, or zero charge.

If the charge of the ligands compensates for the charge of the complexing agent, then such complex compounds are called neutral or non-electrolyte complexes: they consist only of the complexing agent and ligands of the inner sphere.

Such a neutral complex is, for example,.

The most typical complexing agents are cations d-elements.

Ligands can be:

a) polar molecules - NH 3, H 2 O, CO, NO;
b) simple ions - F -, Cl -, Br -, I -, H -, H +;
c) complex ions - CN -, SCN -, NO 2 -, OH -.

Consider the table showing the coordination numbers of some complexing agents.

Nomenclature of complex compounds. In a compound, the anion is first named and then the cation. When specifying the composition of the inner sphere, anions are first of all called, adding the suffix - O-, for example: Cl - - chloro, CN - - cyano, OH - - hydroxo, etc. Hereinafter, neutral ligands are called and primarily ammonia and its derivatives. In this case, they use the terms: for coordinated ammonia - ammin, for water - aqua... The number of ligands is indicated in Greek words: 1 - mono, 2 - di, 3 - three, 4 - tetra, 5 - penta, 6 - hexa. Then they move on to the name of the central atom. If the central atom is part of the cations, then the Russian name of the corresponding element is used and its oxidation state (in Roman numerals) is indicated in brackets. If the central atom is contained in the anion, then use the Latin name of the element, and at the end add the ending - at... In the case of non-electrolytes, the oxidation state of the central atom is not given, since it is unambiguously determined from the condition that the complex is electrically neutral.

Examples. To name the complex Сl 2, the oxidation state is determined (S.O.)
NS complexing agent - Cu ion NS+ :

1 x + 2 (–1) = 0,x = +2, C.O. (Cu) = +2.

The oxidation state of the cobalt ion is found in a similar way:

y + 2 (–1) + (–1) = 0,y = +3, S.O. (Co) = +3.

What is the coordination number of cobalt in this compound? How many molecules and ions are there around the central ion? The coordination number of cobalt is six.

The name of the complex ion is written in one word. The oxidation state of the central atom is indicated by a Roman numeral in parentheses. For example:

Cl 2 - tetraammine copper (II) chloride,
NO 3 – dichloroaquatriamminecobalt (III) nitrate,
K 3 - hexacyanoferrate (III) potassium,
K 2 - tetrachloroplatinate (II) potassium,
- dichlorotetraamminezinc,
H 2 - hexachloro tin acid.

Using the example of several complex compounds, we will determine the structure of molecules (ion-complexing agent, its SO, coordination number, ligands, inner and outer spheres), give a name to the complex, write down the equations of electrolytic dissociation.

K 4 - potassium hexacyanoferrate (II),

K 4 4K + + 4–.

H - tetrachloroauric acid (formed by dissolving gold in aqua regia),

H H + + -.

OH - diammine silver (I) hydroxide (this substance participates in the "silver mirror" reaction),

OH + + OH -.

Na - tetrahydroxoaluminate sodium,

Na Na + + -.

Complex compounds also include many organic substances, in particular, the products of the interaction of amines with water and acids known to you. For example, methyl ammonium chloride salts and phenylammonium chloride are complex compounds. According to the coordination theory, they have the following structure:

Here, the nitrogen atom is a complexing agent, hydrogen atoms at nitrogen, methyl and phenyl radicals are ligands. Together they form the inner sphere. The outer sphere contains chloride ions.

Many organic substances, which are of great importance in the life of organisms, are complex compounds. These include hemoglobin, chlorophyll, enzymes and dr.

Complex compounds are widely used:

1) in analytical chemistry for the determination of many ions;
2) to separate some metals and obtain metals of high purity;
3) as dyes;
4) to eliminate water hardness;
5) as catalysts for important biochemical processes.

The nomenclature of complex compounds is an integral part of the nomenclature of inorganic substances. The rules for composing the names of complex compounds are systematic (unambiguous). In accordance with the IUPAC recommendations, these rules are universal, since, if necessary, they can be applied to simple inorganic compounds, if there are no traditional and special names for the latter. The names, built according to systematic rules, are adequate to chemical formulas. The formula of a complex compound is drawn up according to the general rules: first, the cation is written - complex or ordinary, then the anion - complex or ordinary. In the inner sphere of the complex compound, the central atom-complexing agent is first written, then uncharged ligands (molecules), then negatively charged ligand-anions.

Single-core complexes

In the names of cationic, neutral and most anionic complexes, the central atoms have the Russian names of the corresponding elements. In some cases, the roots of the Latin names of the elements of the central complexing atom are used for anionic complexes. For example, - dichlorodiammineplatinum, 2- - tetrachloroplatinate (II) –ion, + - cation of diammine silver (I), - - dicyanoargenate (I) -ion.

The name of a complex ion begins with an indication of the composition of the inner sphere. First of all, the anions located in the inner sphere are listed in alphabetical order, adding the ending "o" to their Latin name. For example, OH - - hydroxo, Cl - - chloro, CN - - cyano, CH 3 COO - - acetate, CO 3 2- - carbonato, C 2 O 4 2- -oxalato, NCS - -thiocyanato, NO 2 - -nitro , O 2 2- - oxo, S 2- - thio, SO 3 2- - sulfito, SO 3 S 2- - thiosulfato, C 5 H 5 - cyclopentadienyl, etc. Then, in alphabetical order, the inner-sphere neutral molecules are indicated. For neutral ligands, one-word names of substances are used without changes, for example, N 2 -diazot, N 2 H 4 -hydrazine, C 2 H 4 - ethylene. In-sphere NH 3 is called ammino, H 2 O - aqua, CO - carbonyl, NO - nitrosyl. The number of ligands is indicated by Greek numerals: di, three, tetra, penta, hexa, etc. If the names of the ligands are more complex, for example, ethylenediamine, they are prefixed with the prefixes "bis", "tris", "tetrakis", etc.

The names of complex compounds with the outer sphere consist of two words (in general, "cation anion"). The name of the complex anion ends with the suffix –at. The oxidation state of the complexing agent is indicated in Roman numerals in brackets after the name of the anion. For example:

K 2 - potassium tetrachloroplatinate (II),

Na 3 [Fe (NH 3) (CN) 5] - sodium pentacyanomonoamminferrate (II),

H 3 O - oxonium tetrachloroaurate (III),

K - potassium diiodoiodate (I),

Na 2 - sodium hexahydroxostannate (IV).

In compounds with a complex cation, the oxidation state of the complexing agent is indicated after its name in Roman numerals in brackets. For example:

Cl - diamminesilver (I) chloride,

Br - trichlorotriammineplatinum (IV) bromide,

NO 3 -

Chloronitrotetraamminecobalt (III) nitrate.

The names of complex compounds - non-electrolytes without an external sphere - consist of one word; the oxidation state of the complexing agent is not indicated. For example:

- trifluorotriaquocobalt,

- tetrachlorodiammine platinum,

- bis (cyclopentadienyl) iron.

The name of compounds with a complex cation and anion consists of the names of the cation and anion, for example:

hexanitrocobaltate (III) hexaamminecobalt (III),

trichloroammine platinum (II) chlorotriammine platinum (II).

For complexes with ambidentate ligands, the name indicates the symbol of the atom with which this ligand is bound to the central complexing atom:

2- - tetrakis (titianato-N) cobaltate (II) -ion,

2- - tetrakis (thiocyanato-S) mercurate (II) - ion.

Traditionally, an ambidentate ligand NO 2 is called a nitro ligand if the donor atom is nitrogen, and a nitrite ligand if the donor atom is oxygen (–ONO -):

3- - hexanitrocobaltate (III) -ion,

3- - hexanitrite-cobaltate (III) -ion.

Classification of complex compounds

Complex ions can be part of molecules of various classes of chemical compounds: acids, bases, salts, etc. Depending on the charge of the complex ion, they are distinguished cationic, anionic and neutral complexes.

Cationic complexes

In cationic complexes, the central complexing atom is cations or positively polarized atoms of the complexing agent, and the ligands are neutral molecules, most often water and ammonia. Complex compounds in which water acts as a ligand are called aqua complexes. These compounds include crystalline hydrates. For example: MgCl 2 × 6H 2 O

or Cl 2,

CuSO 4 × 5H 2 O or ∙ SO 4 ∙ H 2 O, FeSO 4 × 7H 2 O or SO 4 × H 2 O

In the crystalline state, some aqua complexes (for example, copper sulfate) also retain crystallization water, which is not part of the inner sphere, which is less firmly bound and is easily split off when heated.

One of the most numerous classes of complex compounds are ammino complexes (ammoniaates) and aminates. The ligands in these complexes are ammonia or amine molecules. For example: SO 4, Cl 4,

Cl 2.

Anionic complexes

Ligands in such compounds are anions or negatively polarized atoms and their groups.

Anionic complexes include:

a) complex acids H, H 2, H.

b) double and complex salts of PtCl 4 × 2KCl or K 2,

HgI 2 × 2KI or K 2.

c) oxygen-containing acids and their salts H 2 SO 4, K 2 SO 4, H 5 IO 6, K 2 CrO 4.

d) hydroxosalts K, Na 2.

e) polyhalides: K, Cs.

Neutral complexes

Such compounds include complex compounds that do not have an external sphere and do not give complex ions in aqueous solutions: ,, carbonyl complexes,.

Cationic-anionic complexes

The compounds simultaneously contain both a complex cation and a complex anion:

, .

Cyclic complexes (chelates)

Coordination compounds in which the central atom (or ion) is simultaneously bonded to two or more donor atoms of the ligand, as a result of which one or more heterocycles are closed, are called chelates ... Ligands that form chelating rings are called chelating (chelating) reagents. Closure of the chelate cycle by such ligands is called chelation(by chelation). The most extensive and important class of chelates is metal chelate complexes. The ability to coordinate ligands is inherent in metals of all oxidation states. In the elements of the main subgroups, the central complexing atom is usually in the highest oxidation state.

Chelating reagents contain two main types of electron donor centers: a) groups containing a mobile proton, for example, —COOH, —OH, —SO 3 H; when they are coordinated to the central ion, proton substitution is possible and b) neutral electron-donating groups, for example, R 2 CO, R 3 N. Bidentate ligands occupy two places in the internal coordination sphere of the chelate, such as ethylenediamine (Fig. 3).

According to the Chugaev rule of cycles, the most stable chelate complexes are formed when the cycle contains five or six atoms. For example, among the diamines of the composition H 2 N- (CH 2) n-NH 2, the most stable complexes are formed for n = 2 (five-membered ring) and n = 3 (six-membered ring).

Fig. 3. Copper (II) bisethylenediamine cation.

Chelates in which, when the chelate ring closes, the ligand uses proton-containing and neutral electron-donor groups and is formally bound to the central atom by a covalent and donor-acceptor bond, called are intracomplex connections. Thus, polydentate ligands with acidic functional groups can form intracomplex compounds. Intracomplex compounds are a chelate in which the ring closure is accompanied by the displacement of one or more protons from the acid functional groups by a metal ion, in particular, the intracomplex compound is copper (II) glycinate:

Fig. 4. Intra-complex compound of 8-hydroxyquinoline with zinc.

Hemoglobin and chlorophyll are also intracomplex compounds.

The most important feature of chelates is their increased stability in comparison with similarly constructed non-cyclic complexes.

Examples of problem solving

In reactions Co Cl 3 + 6 N H 3 = Cl 3 and 2KCI + PtCI 2 = K 2 complex compounds Cl 3 and K 2 are called complex compounds.

Such compounds are formed if the original molecules can exhibit "additional" valence due to the formation of a covalent bond in the donor-acceptor type. To do this, one of the molecules must contain an atom with free orbitals, and the other molecule must have an atom with a lone pair of valence electrons.

Composition of complex compounds. According to the coordination theory of A. Verner, complex compounds are distinguished internal and external spheres... The inner sphere (complex ion or complex), as a rule, is enclosed in square brackets, and consists of complexing agent(atom or ion) and surrounding ligands:

ligand complexing agent

[Co (NH 3) 6] CI 3

inner sphere outer sphere

Atoms or ions with vacant valence orbitals serve as complexing agents. The most common complexing agents are atoms or ions of d - elements.

Ligands can be molecules or ions providing lone pairs of valence electrons for coordination with a complexing agent.

The number of coordinated ligands is determined coordination number complexing agent and denticity of ligands. Coordination number is equal to the total number of σ-bonds between the complexing agent and ligands, it is is determined by the number of free (vacant) atomic orbitals of the complexing agent, which it provides for donor electron pairs of ligands.

the coordination number of the complexing agent is equal to its doubled oxidation state.

Dentistry ligand Is the number of all σ-bonds that the ligand can form with the complexing agent; this value is defined as the number of donor pairs of electrons, which the ligand can provide to interact with the central atom. According to this characteristic, mono-, di- and poly-dentate ligands are distinguished. For example, ethylenediamine H 2 N-CH 2 -CH 2 -NH 2, ions SO 4 2-, CO 3 2- are bidentate ligands. It should be borne in mind that ligands do not always show their maximum dentition.

In the case of monodentate ligands (as in the examples under consideration, ammonia : NH 3 and chloride ions CI -) the index indicating the number of ligands coincides with the coordination number of the complexing agent. Examples of other ligands and their names are given in the table below.

Determination of the charge of a complex ion (inner sphere). Complex ion charge is equal to the algebraic sum of the charges of the complexing agent and ligands, or is equal to the charge of the outer sphere, taken with the opposite sign(the rule of electroneutrality). In the Cl 3 compound, the outer sphere is formed by three chlorine ions (CI -) with a total charge of the outer sphere 3-, then, according to the rule of electroneutrality, the inner sphere has a charge of 3+: 3+.

In the complex compound K 2, the outer sphere is formed by two potassium ions (K +), the total charge of which is 2+, then the charge of the inner sphere will be 2-: 2-.

Determination of the charge of the complexing agent.

The terms "charge of the complexing agent" and "oxidation state of the complexing agent" are the same here.

In the complex 3+, the ligands are electrically neutral molecules; therefore, the charge of the complex (3+) is determined by the charge of the complexing agent, Co 3+.

In complex 2- the charge of the inner sphere (2-) is equal to the algebraic sum of the charges of the complexing agent and ligands: -2 = x + 4 × (-1); the charge of the complexing agent (oxidation state) x = +2, i.e. the coordination center in this complex is Pt 2+.

Cations or anions outside the inner sphere, associated with it by electrostatic forces of ion - ion interaction, form external sphere complex compound.

Nomenclature of complex compounds.

The name of the compounds is determined by the type of complex compound depending on the charge of the inner sphere: for example:

Cl 3 - refers to cationic complex compounds, because the inner sphere (complex) 3+ is a cation;

K 2 - anionic complex compound, inner sphere 2- is an anion;

0 and 0 refer to electrically neutral complex compounds, they do not contain an outer sphere, since the inner sphere has zero charge.

General rules and features in the name of complex compounds.

General rules:

1) in all types of complex compounds, they first call the anionic, then the cationic part of the compound;

2) in the domestic sphere for all types of complexes, the number of ligands is indicated using Greek numerals: di, three, tetra, penta, hexa etc.;

2a) if different ligands are located in the inner sphere of the complex (these are mixed or mixed-ligand complexes), the numbers and names of negatively charged ligands are indicated first, with the addition of the ending -O(Cl ˉ - chloro, OH ˉ - hydroxo, SO 4 2 ˉ - sulfato etc. (see table), then indicate the numbers and names of neutral ligands, and water is called aqua, and ammonia - amine;

2b) the last in the inner sphere called a complexing agent.

Feature: The name of the complexing agent is determined by whether it is included in a complex cation (1), a complex anion (2) or a neutral complex (3).

(1). Complexing agent - in the complex cation.

After the names of all ligands in the inner sphere of the complex, the Russian name of the complexing element in the genitive case is given. If an element exhibits a different oxidation state, it is indicated after its name in brackets with numbers. A nomenclature is also used, indicating not the oxidation state for the complexing agent, but its valence (in Roman numerals).

Example. Name the complex compound Cl.

a). Let's define the charge of the inner sphere according to the rule: the charge of the inner sphere is equal in magnitude, but opposite in sign to the charge of the outer sphere; the charge of the outer sphere (it is determined by the chlorine ion Cl -) is equal to -1, therefore, the inner sphere has a charge of +1 (+) and this is - complex cation.

b). Let us calculate the oxidation state of the complexing agent (this is platinum), since the name of the compound must indicate its oxidation state. Let us denote it by x and calculate it from the electroneutrality equation (the algebraic sum of the oxidation states of all atoms of the elements in the molecule is equal to zero): x × 1 + 0 × 3 + (-1) × 2 = 0; x = +2, i.e. Pt (2+).

v). We begin the name of the compound with the anion - chloride .

G). Further, we call the cation + - this is a complex cation that contains different ligands - both molecules (NH 3) and ions (Cl -), therefore we first of all call charged ligands, adding the ending - O-, i.e. - chloro , then we call the ligand molecules (this is ammonia NH 3), there are 3 of them, for this we use the Greek numeral and the name of the ligand - triammin , then we call in Russian in the genitive case the complexing agent with an indication of its oxidation state - platinum (2+) ;

e). By successively combining the names (given in bold italics), we get the name of the complex compound Cl - chlorotriammineplatinum chloride (2+).

Examples of compounds with complex cations and their names:

1) Br 2 - nitrite bromide Openta amminvanadium (3+);

2) CI - chloride carbonate Otetra amminchrome (3+);

3) (ClO 4) 2 - perchlorate tetra amminmedi (2+);

4) SO 4 - bromine sulfate Openta amminruthenia (3+);

5) ClO 4 - perchlorate di bromine Otetra aquacobalt (3+).

Table. Formulas and names of negatively charged ligands

(2). Complexing agent - in the complex anion.

After the name of the ligands, the complexing agent is called; the Latin name of the element is used, to it is added suffix –At ) and the valence or oxidation state of the complexing agent is indicated in brackets. Then the cation of the outer sphere is called in the genitive case. The index indicating the number of cations in the compound is determined by the valence of the complex anion and is not displayed in the name.

Example. Name the complex compound (NH 4) 2.

a). Let's define the charge of the inner sphere, it is equal in magnitude, but opposite in sign to the charge of the outer sphere; the charge of the outer sphere (it is determined by the ammonium ions NH 4 +) is +2, therefore, the inner sphere has a charge of -2 and this is a complex anion 2-.

b). The oxidation state of the complexing agent (this is platinum) (denoted by x) is calculated from the electroneutrality equation: (+1) × 2 + x × 1 + (- 1) × 2 + (-1) × 4 = 0; x = +4, i.e. Pt (4+).

v). We start the name of the compound with the anion - (2- (complex anion), which contains different ligand ions: (OH -) and (Cl -), therefore we add the ending to the name of the ligands - O-, and their number is denoted by numerals: - tetrachlorodihydroxo - , then we call the complexing agent, using the Latin name of the element, to it we add suffix –At(a distinctive feature of the anionic type complex) and indicate in parentheses the valence or oxidation state of the complexing agent - platinum (4+).

G). The latter is called the cation in the genitive case - ammonium.

e). By successively combining the names (given in bold italics), we get the name of the complex compound (NH 4) 2 - ammonium tetrachlorodihydroxoplatinate (4+).

Examples of compounds with complex anions and their names:

1) Mg 2 - three fluorine O hydroxoalumin at (3+) magnesium;

2) K 2 - di thiosulfate Odi ammincupr at (2+) potassium;

3) K 2 - tetra iodine O merkur at (2+) potassium.

(3). Complexing agent - in a neutral complex.

After the name of all ligands, the latter is called the complexing agent in the nominative case, and the degree of its oxidation is not indicated, since it is determined by the electroneutrality of the complex.

Examples of neutral complexes and their names:

1) – di chlorine O aquaammineplatinum;

2) – three bromine Othree ammincobalt;

3) - trichlorotriamminecobalt.

Thus, the complex part of the name of all types of complex compounds always corresponds to the inner sphere of the complex.

The behavior of complex compounds in solutions. Equilibria in solutions of complex compounds. Let us consider the behavior of a complex compound of diammine silver chloride Cl in solution.

The ions of the outer sphere (CI -) are associated with the complex ion mainly by the forces of electrostatic interaction ( ionic bond), therefore, in a solution, like ions of strong electrolytes, almost complete the disintegration of a complex compound into a complex and an outer sphere is an outer sphere or primary dissociation complex salts:

Cl ® + + Cl - - primary dissociation.

Ligands in the inner sphere of the complex are bound to the complexing agent by donor-acceptor covalent bonds; their cleavage (detachment) from the complexing agent proceeds in most cases to an insignificant extent, as in weak electrolytes, therefore it is reversible. Reversible disintegration of the inner sphere is the secondary dissociation of the complex compound:

+ «Ag + + 2NH 3 - secondary dissociation.

As a result of this process, an equilibrium is established between the complex particle, the central ion, and the ligands. It proceeds stepwise with sequential cleavage of ligands.

The equilibrium constant of the secondary dissociation process is called the complex ion instability constant:

To nest. = × 2 / = 6.8 × 10 - 8.

It serves as a measure of the stability of the inner sphere: the more stable the complex ion, the lower its instability constant, the lower the concentration of ions formed during the dissociation of the complex. The values ​​of the instability constants of the complexes are tabular values.

Instability constants, expressed in terms of the concentration of ions and molecules, are called concentration constants. Instability constants, expressed through the activities of ions and molecules, do not depend on the composition and ionic strength of the solution. For example, for a complex in general form МеХ n (dissociation equation МеХ n «Ме + nХ) the instability constant has the form:

To nest. = a Me × a n X / a MeX n.

When solving problems in the case of sufficiently dilute solutions, it is allowed to use concentration constants, assuming that the activity coefficients of the components of the system are practically equal to unity.

The given equation of secondary dissociation is the total reaction of the stepwise process of dissociation of the complex with the sequential elimination of ligands:

+ «+ + NH 3, K nest. 1 = × /

+ "Ag + + NH 3, K nest. 2 = × /

+ «Ag + + 2NH 3, K nest. = × 2 / = K station 1 × K station 2,

where K nest 1 and K nest 2 are the stepwise instability constants of the complex.

The general instability constant of the complex is equal to the product of the stepwise instability constants.

It follows from the above equations of the stepwise dissociation of the complex that intermediate dissociation products may be present in the solution; with an excessive concentration of ligand due to the reversibility of these processes, the equilibrium of the reactions shifts towards the initial substances and, in the main, there is an undissociated complex in the solution.

To characterize the strength of the complex, in addition to the constant of instability of the complex, the inverse value is used - the constant of stability of the complex b st. = 1 / K nest. ... b set is also a reference value.

Control tasks

181. For the given complex compound, indicate the name, oxidation state (charge) of the complexing ion, coordination number. Write the equations for the electrolytic dissociation of this compound and the expression for the instability constant of the Cl 2, Cl complex.

182 *. SO 4, (NO3) 2.

183 *. K 2 (NO 3) 2, SO4.

184 *. Na, Cl3.

185 *. Ba, Cl.

186 *. (NH 4), Br2.

187 *. Na 3, NO3.

188 *. SO 4, KCl 2, K3.

190 *. , Cl.

Chemistry test - complex compounds - URGENT! and got the best answer

Answer from Nick [guru]
Some questions were asked incorrectly, for example 7,12,27. Therefore, the answers contain caveats.
1. What is the coordination number of the complexing agent in the complex ion +2?
AT 6
2. What is the coordination number of the complexing agent in the complex ion 2+?
B) 6
3. What is the coordination number of the complexing agent in the complex ion 2+
B) 4
4. What is the coordination number of Cu² + in the complex ion +?
B) 4
5. What is the coordination number of the complexing agent in the complex ion: +4?
B) 6
6. Determine the charge of the central ion in the complex compound K4
B) +2
7. What is the charge of a complex ion?
B) +2 - if we assume that the complexing agent is Cu (II)
8. Among the iron salts, define the complex salt:
A) K3
9. What is the coordination number of Pt4 + in the complex ion 2+?
A) 4
10. Determine the charge of the complex ion K2?
B) +2
11. Which molecule corresponds to the name of copper (II) tetraammine dichloride?
B) Cl2
12. What is the charge of a complex ion?
D) +3 - if we assume that the complexing agent is Cr (III)
13. Among the salts of copper (II), determine the complex salt:
B) K2
14. What is the coordination number of Co3 + in the complex ion +?
B) 6
15. Determine the charge of the complexing agent in the complex compound K3?
D) +3
16. Which molecule corresponds to the name of potassium tetraiodohydrate (II)?
A) K2
17. What is the charge of a complex ion?
IN 2
18. Among the nickel (II) salts, define the complex salt:
B) SO4
19. What is the coordination number of Fe3 + in the complex ion -3?
AT 6
20. Determine the charge of the complexing agent in the complex compound K3?
B) +3
21. Which molecule corresponds to the name silver (I) chloride diamine?
B) Cl
22. What is the charge of the complex ion K4?
B) -4
23. Among zinc salts, define a complex salt
B) Na2
24. What is the coordination number of Pd4 + in the 4+ complex ion?
D) 6
25. Determine the charge of the complexing agent in the complex compound H2?
B) +2
26. Which molecule corresponds to the name of potassium hexacyanoferrate (II)?
D) K4
27. What is the charge of a complex ion?
D) -2 - if we assume that the complexing agent is Сo (II)
27. Among the chromium (III) compounds, define the complex compound
B) [Cr (H2O) 2 (NH3) 4] Cl3
28. What is the coordination number of cobalt (III) in the complex ion NO3?
B) 6
29. Determine the charge of the complexing agent in the complex compound Cl2
A) +3
30. What molecule does the name sodium tetraiodopalladate (II) correspond to?
D) Na2

Answer from James bond[newbie]
Oh my God

Answer from Kitten ...[guru]
# 30 last

Today I worked on this review. If someone comes in handy, I will be glad. If someone does not understand - that's okay.

Ammoniases are complex compounds in which ammonia NH 3 molecules act as ligands. A more accurate name for complexes containing ammonia in the inner sphere is ammonia; however, NH 3 molecules can be found not only in the inner, but also in the outer sphere of the compound - ammonia.

Ammonium salts and ammoniaates are usually considered as two types of complex compounds, similar in composition and in many properties, the first - ammonia with acids, the second - ammonia with salts of mainly heavy metals.

Ammonia complexes are usually obtained by reacting metal salts or hydroxides with ammonia in aqueous or non-aqueous solutions, or by processing the same salts in the crystalline state gaseous ammonia: For example, a copper ammonia complex is formed by the reaction:

Cu 2+ + 4NH 3 → 2+

The chemical bond of ammonia molecules with a complexing agent is established through nitrogen atom who serves as a donor lone pair of electrons.

The formation of ammono complexes in aqueous solutions occurs by sequential substitution of water molecules in the internal sphere of aquacomplexes for ammonia molecules:

2+ + NH 3. H 2 O2+ + 2 H 2 O;

2+ + NH 3. H 2 O2+ + 2H 2 O

Do not forget about the interaction of ammonia with the salt anion. The reaction of the formation of copper tetraammoniumate from copper sulfate and an aqueous solution of ammonia is as follows:

CuSO 4 + 2NH 3 + 2H 2 O = Cu (OH) 2 + (NH 4) 2 SO 4

Cu (OH) 2 + 4NH 3 = (OH) 2

Another name for the resulting compound is Schweitzer's reagent, in its pure form it is an explosive compound, often used as a solvent for cellulose and in the production of copper-ammonia fibers.

The most stable among ammonia complexes:

3+ (b 6 = 1.6. 10 35),

-[Cu (NH 3) 4] 2+ (b 4 = 7.9. 10 12),

2+ (b 4 = 4.2. 10 9) and some others.

Ammoniases are destroyed by any action that removes (when heated) or destroys (by the action of an oxidizing agent) the molecule ammonia, convert ammonia in an acidic environment into an ammonium cation (the ammonium cation does not contain lone pairs of electrons and therefore cannot act as a ligand), or bind the central atom complex, for example, in the form of a poorly soluble precipitate:

Cl 2 = NiCl 2 + 6 NH 3 ( G)

SO 4 + 6 Br 2 = CuSO 4 + 12 HBr + 2 N 2 ( G)

SO 4 + 3 H 2 SO 4 = NiSO 4 + 3 (NH 4) 2 SO 4

(OH) 2 + Na 2 S + 4 H 2 O = CuS¯ + 2 NaOH + 4 NH 3. H 2 O (4)

Ammoniates differ both in composition +, 2+, and in stability in aqueous solutions, are used in analytical chemistry for the detection and separation of metal ions.

When heated (depending on the pressure - from 80 to 140 ºС) and reduced pressure, copper ammoniaates can lose ammonia and pass from the form of tetraamiacate to diamiakate, which is shown by the example of copper nitrate ammoniaates in the experimental work (2).

With more intense chemical decomposition, copper nitrate can decompose to water, nitrogen and copper. Table 1 shows the comparative characteristics of copper nitrate tetraamicate and ammonium nitrate.

Table 1: Comparative characteristics of copper nitrate tetraammoniumate and ammonium nitrate (3)

Substance	Formula	Density (g / cm e)	Heat of Formation (cal / mol)	Decomposition reaction equation	Heat of reaction of decomposition		Gas volume (l / kg)
					kcal / mol	kcal / kg
Ammonium nitrate	NH 4 NO 3	1,73	87.3	2H 2 O steam + N 2 + 1 / 2O 2
Copper nitrate tetraammoniumate	[Cu (NH3) 4] (NO 3) 2			6H2O + 3N 2 + Cu l

The significantly higher (1.6–1.7 times, per unit weight) heat of thermal decomposition of copper nitrate tetraammonate in comparison with NH 4 N0 3 suggests that combustion or explosion reactions can be relatively easily initiated in them. In 1964, Preller (4) studied the sensitivity and some explosive properties of copper (II, cobalt (III) and nickel (II) ammoniaates.) It turned out that these compounds have significant explosive properties and their detonation rate is 2400 -3500 m / sec.

The researchers also conducted a study of combustion tetraammonium nitrate of copper. The flash point of this compound was 288 ° C at a heating rate of 20 deg / min. The ability of copper ammoniaate to burn at elevated pressure (at least 60 atm.) Has been experimentally established. This fact once again confirms the position put forward, according to which any chemical system in which an exothermic chemical reaction can take place, when appropriate conditions are selected, should be capable of propagating a combustion reaction in it.

Copper (II) found in tetrammiakate can be reduced to (I) to obtain monovalent copper diammineacate. An example of such a reaction is the interaction of blue copper tetraammoniumate with copper shavings at room temperature, slight stirring and no interaction with air. During the reaction, the blue color disappears.

(OH) 2 + Cu = 2 (OH)

Monovalent copper diammonate is readily oxidized to tetramineate by interaction with atmospheric oxygen.

4 (OH) + 2H 2 O + O 2 + 8NH 3 = 4 (OH) 2

Conclusion: such work should have been done long ago. A huge layer of knowledge on heavy metal ammonates, in particular copper, will be touched upon, which, perhaps, should be studied further in addition to our developments and research.

A striking example of this is the dissertation of SERGEEVAALEXANDER ALEXANDROVNA on the topic: « INFLUENCE OF AMMIAKATOVNA PHOTOSYNTHESIS, PRODUCTIVITY OF AGRICULTURAL CROPS AND EFFICIENCY OF USE OF FERTILIZERS "where the use of heavy metal ammonia as a fertilizer for improving the productivity and photosynthesis of plants is thoroughly proved.

List of used literature:

1. Materials from the site http://ru.wikipedia.org
2. Copper (II) nitrate ammoniaates Cu (NH3) 4 (NO3) 2 and Cu (NH3) 2 (NO3) 2. Thermolysis under reduced pressure. S.S. Dyukarev, I.V. Morozov, L.N. Reshetova, O.V. Guz, I.V. Arkhangelsky, Yu.M. Korenev, F.M. Spiridonov. Inorg.Khim journal. 1999
3. Ж 9, 1968 UDC 542.4: 541.49 STUDY OF THE ABILITY TO COMBUSTION OF AMMONIA NITRATES OF COPPER AND COBALT A. A. Shidlovsky and V. V. Gorbunov
4. N. R e 11 e g, Explosivsto "f., 12, 8, 173 (1964)
5. Materials from the site http://www.alhimik.ru. Methodological guide for students (MITHT)
6. Masters from the site http://chemistry-chemists.com