Among the biologically active substances contained in the body, metal ions occupy a special place. Thus, biocations are the most sensitive “chemical points” of the body. These biogenic elements of life are found in the body mainly in the form of aqueous solutions of their salts and complex (coordination) compounds.
Complex connections called connections, in nodes crystal lattice which contain complex particles (complex ions), consisting of a central atom or ion and surrounding neutral molecules or ions. Complex ions are not destroyed when they pass into solution or melt.
The structure of complex compounds was explained in the coordination theory of A. Werner (1893). According to Werner's coordination theory, complex compounds are characterized by a special spatial arrangement of the particles that make up their molecules. For example: K + | CN - CN - | K+
| CN - Fe 2+ CN - | K 4
K+ | CN - CN - | K+
From the given coordination formula it is clear that one of the ions occupies central position. Such an atom or ion is called complexing agent. Most often, complexing agents are positively charged metal ions, often metals of secondary subgroups (d- and f-elements), much less often neutral metal atoms (Fe, Ni) and negatively charged non-metal atoms (N -3, O -2, S). Typical complexing agents are metals such as Fe, Cu, Ag, Au, Hg, Co, Cr, Mn, Cd, Ni, Pt, and other d- and f-elements. Near the complexing agent, polar molecules or ions of a different sign are located in a certain order, sometimes both, they are called ligands(addendami), which means “connected.” The most important ligands are:
a) Neutral molecules having a dipole character: H 2 O, NH 3, CO, NO, C 2 H 4.
b) Ions: H - , O -2 , OH - , Cl - , J - , Br - , CN - , HCO 3 - , as well as bioligands in the form of macromolecules of amino acids and their derivatives, peptides, proteins, enzymes, hormones, nucleic acids and their fragments.
The complexing agent and ligands form inner sphere(indicated by square brackets), and ions that are not included in the inner spheres form outer sphere. The inner sphere is often enclosed in square brackets. The charge of a complex ion is equal to the algebraic sum of the charges of the complexing agent and ligands. The number of ligands located in close proximity to the central ion is called coordination number ion (c.n.). Coordination numbers 2, 4, 6 are often found. Usually the coordination number is twice the charge of the complexing agent, with the exception of the Fe 2+ ion, for which the c.n. equals 6, for Pt 4+ - 6.
If ligands are connected to the complexing agent by one bond and occupy one coordination site in the inner sphere of the complex, such ligands are called monodental(OH - , Cl - , J - , Br - , CN) , two -bidentant(CO 3 2-, C 2 O 4 2-) - they occupy 2 coordination sites. Some ligands attach to the central ion with a large number of coordination bonds. So, among the complex organic compounds there are those that can act as three, tetra - and more - they are called polydentant. Polydentate organic ligands, being closed by two or more coordination bonds, can form cyclic complexes.
Molecules of complex compounds differ in a well-defined geometric structure. Thus, two ligands are often located near a metal ion in such a way that the central ion and the two ligands are on the same straight line. Three ligands are placed at the corners of a triangle, four at the corners of a square or tetrahedron (tetrahedron), six at the corners of an octahedron (octahedron), eight at the corners of a cube. If the ligands are not the same, then the geometric shapes may not be entirely correct (distorted), but, nevertheless, the ligands remain fixed at certain points in space around the central ion.
Complex connections classify by the charge of the complex ion and by the type of ligands. Based on the charge of the complex ion, complexes are divided into cationic(complex with a positive charge), anionic(complex with a negative charge), neutral(complex with zero charge).
According to the type of ligands, complexes are: acid complexes, - ligands are acid residues (Cl -, J -, Br -, CN -, HCO 3 -, CO 3 2-, C 2 O 4 2-); hydroxy complexes (OH -); aqua complexes (H 2 O); amino complexes (NH 3); mixed, when the complex includes several types of ligand.
Hence, to correctly write the formula of a complex compound, you need to know: the charge (oxidation state) of the complexing agent; charge of ligands; coordination number of the complexing agent; ions of the outer sphere.
When writing formulas complex ion The symbol of the complexing agent is indicated first, then the neutral ligands are indicated in the order H 2 O, NH 3 . Neutral ligands are followed by anionic ligands. Anionic ligands are listed in order: H -, O -2, OH -, simple anions, complex anions of inorganic acids, anions of organic acids.
Formulas of complex compounds are read strictly from right to left, observing the order of ligands in the formula. In the names of complex compounds, the anion is named first in the nominative case, and then the cation in genitive case.
I. If the connection includes complex cation, then the ligands are first named according to the order of their location in the complex, followed by the name of the complexing agent (Russian name of the element). Roman numerals in parentheses indicate the oxidation state of the complexing agent. Neutral molecules acting as ligands have their usual names, except for ammonia - amine, water - aqua, CO - carbonyl, NO - nitrosyl. Negatively charged ligands are named ending in "o". For example, H - - hydrido, O -2 - oxo, OH - - hydroxo, F - - fluoro, Cl - - chloro, S -2 - thio, CN - - cyano, SO 4 -2 - sulfato, CH 3 COO - - acetato, CNS - - thiocyanato, C 2 O 4 -2 - oxalato. If there are several ligands, then first the outer sphere ion is named, then the ligands are named by Greek numbers: - 2-di, 3-three, etc.
For example: names of complex cations
[Co H 2 O (NH 3) 5 ] Cl 3 - pentaamminaquacobalt (III) chloride
Cl 3 - chloropentaammineplatinum(IV) chloride
NO 3 - hydroxydiamminequaplatinum (II) nitrate
SO 4 - tetraaquacopper (II) sulfate
II. If the connection includes complex anion, then the ligands are named first in the above order. Next, the complexing agent is called using the root of its Latin name with the addition of the syllable “at”, after which the oxidation state of the complexing agent is indicated in parentheses in Roman numerals. Lastly, the cation of the outer sphere in the genitive case is called. For example:
K-potassium dicyanoargentate(I)
K 2 - potassium tetrachlorocuprate (II)
K 3 - potassium hexacyanoferrate (III)
K 2 - potassium dinitrodichloroplatinate (IV)
Name neutral complexes are made up of the name of the ligands and the Russian name of the complexing agent in the nominative case. In this case, the valency of the complexing agent is not indicated. For example: - trichlorotriammine cobalt.
Tetrachlorodiammineplatinum.
The inner and outer spheres in molecules of complex compounds are connected by an ionic bond. The complexing agent and ligands are linked by a covalent bond via a donor-acceptor mechanism: ligands play a role donor electron pair, and the complexing agent is the role acceptor, in the free orbital of which the electron pair of the ligand is located.
The dissociation of complex compounds occurs in two stages. Primary dissociation of complex compounds occurs according to the type of ionization strong electrolytes and proceeds completely: Cl → + + Cl -
Ligands with the complexing agent are bound by a stronger bond and the dissociation of the complex ion occurs to a lesser extent. This type of dissociation is called secondary.
+ → Ag + + 2NH 3
A measure of the stability of a complex ion is its instability constant and is designated Kn.
The lower the instability constant, the more stable the complex.
Complex compounds play huge role in the life processes of plants and animals. In the body of animals and plants, complex compounds perform a wide variety of functions: accumulation and movement various substances and energy; formation and cleavage of chemical bonds; participation in the processes of respiration, photosynthesis, biological oxidation and enzymatic catalysis. Such biologically important substances as hemoglobin, chlorophyll, cyanocobolamin are intracomplex, chelate compounds. In them, four coordination sites are occupied by one particle, called porphin, and the complexing agent in hemoglobin is Fe +2, and in chlorophyll - Mg2, in vitamin B12 - Co +3.
The iron complex with porphyrin has a flat structure, in which the iron ion is connected by 4 coordination bonds to 4 pyrrole rings, 5 communication is in progress to attach the globin protein, but the sixth place in the coordination sphere is free. This place is occupied by the oxygen molecule carried by hemoglobin during respiration.
Recently, it has been established that complex compounds of platinum and palladium have an inhibitory effect on the development of malignant tumors and can be successfully used for therapeutic purposes, the formation of chelates (intra-complex) compounds, are used in dissolving salts in kidney stones and reducing water hardness due to the presence of calcium ions and magnesium. The high bactericidal activity of some complex silver compounds is known. Trilon B (EDTA) is capable of forming complexes with many metals, including Ca +2. This makes it possible to use it for diseases accompanied by excessive deposition of calcium salts in the body.
Nutrients
Studying the abundance of individual elements and their isotopes allows us to note the following patterns.
1. Elements with even serial numbers are characterized by increased prevalence. On Earth, the content of even elements is 97.21% of the mass of all elements.
2. The most common elements are those whose isotopes have a mass number that is a multiple of 4. Examples of such elements are He, O, Ne, Si, S, Ar, Fe, Ni, etc.
On Earth there are continuous nuclear processes, leading ultimately to a change in their isotopic composition. However, all these processes are going slowly. The results of the analysis of the substance of the earth's crust show that the isotopic composition of elements on Earth is practically constant. The first studies on the relationship between the earth's crust and the chemical composition of living organisms were made by the Russian scientist V.I. Vernadsky. He believed that earth's crust and living organisms make up unified system. The unity of living and nonliving lies, first of all, in the commonality of their elemental composition. Substances of living and inanimate nature consist of the same chemical elements connected by covalent, ionic, hydrogen bonds.
As a result of long-term continuous exposure to the body of a certain chemical composition As the flow of atoms occurs, organisms are selected and distributed among different zones of the Earth, and along with this comes variability in organisms. For example, iodine deficiency in mountainous areas and river valleys causes an enlarged thyroid gland and goiter in animals and humans. With the growth of civilization, more and more biologically active unnecessary substances enter the human body, such as: mercury (from dental fillings), lead, antimony, arsenic (from newspapers), metal ions (from kitchen utensils).
Research by US scientists has indicated a lack of chromium in the body tissues of the inhabitants, in comparison with the inhabitants of Africa and Asia. It is caused by excess refined sugar and other refined foods in the human diet. Chromium deficiency explains the rise in heart disease.
Elements that play an important role in physiological and pathological processes in the human body are called
less than 10 -5
| Li, Be, Pb, Mo, W, Cd, Ni, Ag | Se |
Depending on the structure ( electronic configuration) atom, biogenic elements are divided into s, p, d -bioelements.
s-elements ns 2: H, Na, Mg, Ca, Sr, Ba (6)
p-elements ns 2 np 1-6: Al, C, Si, Sn, Pb, N, P, O, S, Se, F, Cl, I, Br, B (15)
d-elements (n-1)d 1-10 ns 2: Cu, Zn, Cr, Mn, Fe, Co, Ni (7)
Class: 11
Key words: connections, complex ions
Modular lesson
Module structure
UE-0. Integrating didactic goals.
UE-1. Repetition. Chemical bond, scheme of its formation.
UE-2. Alfred Werner's coordination theory.
UE-3. Classification of complex compounds.
UE-4. Preparation of complex compounds.
UE-5. Application, meaning of complexes.
UE-6. Properties of complex compounds.
UE-7. Resume.
UE-8. Control.
Equipment for the lesson. On the demo table:
- concentrated solutions hydrochloric acid and ammonia;
- solutions of aluminum sulfate and sodium hydroxide, copper (II) sulfate, iron (III) chloride, potassium thiocyanate; crystalline potassium iron sulfide (red blood salt);
- demonstration tubes or cylinders, backlit screen;
- magnetic board with a set of applications;
- poster with image structural formulas molecules of chlorophyll and hemoglobin;
- table "Composition of complex compounds";
- chlorophyll extract in ethanol.
UE-0. Integrating didactic goals
- Repeat the mechanism of covalent bond formation .
- Get acquainted with the new class of compounds, classification.
- Study the content of the theory of complex compounds.
- Using chemical experiment, achieve mastery of the preparation, physical and chemical properties of complex compounds.
- Complex compounds in redox reactions.
- Get acquainted with the use of substances of this class.
UE-1. Education mechanism covalent bond
Private didactic goals:
- Repeat the mechanism of covalent bond formation.
- Formation of covalent bonds in molecules of water, hydronium, ammonium ion.
Management. Write down the scheme for the formation of molecules: water, hydronium ion and ammonium. Explain the mechanism of formation of ammonium ion.
Donor-acceptor bond in ammonium ion. What is a donor and what is an acceptor?
UE-2. Alfred Werner's coordination theory
Private didactic goals:
- Motivation, problem statement.
- Introducing a new class of connections.
- Study of the structure of complex compounds (complexing agent, ligands, inner sphere, outer sphere).
- Dissociation of complexes into outer and inner spheres.
- Be able to determine the coordination number of a complexing agent.
- Determine the type chemical bond between the complexing agent and the ligands, the outer and inner sphere.
- Be able to name complex compounds.
1. Guide
In 1597, the German alchemist and physician Libavius conducted experiments with copper sulfate in search of a medicine to treat wounds and skin diseases. Repeat the ancient experience, which turned 410 years old in 2007.
Pour a solution of copper(II) sulfate into a beaker 1/4 full and add ammonia solution in small portions.
Write down the equation of the chemical reaction. What are your observations?
CuSO4 + NH3*H2O= ? + ?
Do your observations match the expected reaction product? Explain your observations, indicate the color and physical state the resulting substance.
What lies behind the kaleidoscope of colors?
Libavius did not find an explanation for what happened, and all his contemporaries were powerless. This is how Libavius obtained the first complex compound, the nature of which was discovered by chemists only at the end of the 19th century. The classical doctrine of valency, developed by A. Kekule and E. Frankland, could not explain how valence-saturated molecules are combined.
Can you explain the experiments performed?
2. Familiarize yourself with the theoretical material, write down the basic concepts in a notebook, answer self-control questions
Supporting notes
IN late XIX century Swiss chemist A. Werner in 1893 he developed a coordination theory, which is based on the theory of the spatial structure of substances and the theory of electrolytic dissociation.
The following concepts were introduced: 1) complex compounds; 2) complexing atom (or central atom); 3) ligands (atoms, ions, polar molecules or non-polar molecules bound to a central atom);
4) coordination number of the central atom (number of ligands).
A complex ion is an ion consisting of a complexing agent and ligands (inner sphere).
A complexing agent (central atom or ion) is an atom (or ion) to which a certain number of molecules or ions are attached.
Ligand is a molecule or ion that is part of a complex ion, connected to the central atom (ion) by a donor-acceptor bond. "Ligand" translates to "bound."
A vacancy is a free electron cell of a d-metal that can be used to form donor-acceptor bonds with ligands.
A complex compound is a complex substance that contains a complex ion.
1. Compounds that contain complex ions are classified as complex compounds.
Coordination number(K.N.) - a number indicating the number of ligands that the complexing agent is capable of attaching to itself. Can have values 2, 4, 6, 8, 10 and others.
The total charge of the resulting complex ion is equal to the algebraic sum of the charges of the central atom (ion) and the ligands.
Names of complex compounds: Na - sodium tetrahydroxoaluminate,
SO 4 - tetraammine copper (II) sulfate.
Conclusion. The bonds between the complexing agent and the ligands are carried out using electron pairs. Both electrons of each bond are provided by one atom, that is, bonds are formed by a donor-acceptor mechanism. The electron donor is the ligands (ammonia molecules), and the acceptor is the central atom (ion - complexing agent Zn 2+).
Spatial structure of complex compounds.
Complexing ions (acceptors) provide their free orbitals, and ligands (donors) both electrons. The spatial structure of the complex ion is determined by the type of orbital hybridization.
- , +
linear molecule - sp-hybridization, tetrahedron sp-hybridization.
Test your knowledge
Self-control (UE-2)
I level
K 2 , Na 4 , (N0 3) 2 . (1 point)
Example answer: K 2 = 2K + + 2- .
2. Create a formula for a complex compound if it is known that its molecule contains ions Ni2+, 3C1, as well as three molecules NH3. (2 points A)
3. Determine the internal and external spheres of a complex compound, the coordination number (CN) of the metal, the charge of the central metal ion, the charge of the complex ion for compounds:
H4, S04, K4, Cl3. (2 points)
Example answer: H 4 +, number = 6. external, internal sphere
Level II
1. Write the equations of dissociation of substances:
K4,
Na 2;
Cl2;
[A1(H 2 O) 6 ] C1 3 (1 point)
2. Write the formula of a complex ion in which the complexing agent is an ion Fe3+ with c.n. equal to 6, and ligands - F ions What is the charge of the complex ion? ( 2 points)
3. Determine the coordination number of the central atom in the complexes, the inner and outer sphere, the charge of the complex ion: C1; K4; [Co(NH 3) 3 ]C1 3. Write down the dissociation of these substances. ( 2 points)
If you score 4-5 points, proceed to the next learning element.
If you scored less than 4 points, then go back and read TRAINING ELEMENT-1 (UE-1) again, work with the supporting notes.
Familiarize yourself with the theoretical material UE-3, test your knowledge with self-control.
UE-3. Classification of complex compounds
Private didactic goals:
1. Get acquainted with the classification of complex compounds according to the composition of the internal and external spheres;
Depending on the nature of the ligand, there are:
1)aqua complexes (H 2 O): [Cr (H 2 O) 6 ]C1 3;
2)ammonia (NH 3): SO 4, Cl;
3)hydroxo complexes (OH~): K 2, Na2;
4)acid complexes (acid residues): K 4, K 2;
5) mixed type complexes: Cl, C1 4, C1O 4.
The central atom can be both metal and non-metal ions.
The central atom is a non-metal: K - potassium tetrafluoroborate(III).
The central atom is metal: Na-sodium tetrahydroxoaluminate.
Composition of complex compounds
| Compound | |||||
| Inner Sphere | (complex ion) | outer sphere | K.ch. central atom (ion) | ||
| complex compounds | names of complex compounds | central atom | ligands | ||
| NH 4 C1 | Ammonium chloride | H+ | NH 3 | Cl | 1 |
| Na | Sodium tetrahydroxyaluminate | A1 3+ | 4OH | Na+ | 4 |
| S0 4 | Tetraammine copper(II) sulfate | C 2+ | 4NH 3 | S0 | 4 |
| K 3 | Potassium hexacyanoferrate(III) | Fe | 6CN | ZK + | 6 |
| Fe 3 2 | Iron(II) hexacyanoferrate(III) | Fe | 6CN | 3Fe2+ | 6 |
Test your knowledge
Self-control (UE-3)
I level
1. From the answers given below, choose the one that characterizes the complexing ion and its charge in the compound Na4:
a) Fe 3+; b) CN; c) Fe 2 +; d) Na + ; e) Na.
2. Which of the following formulas corresponds to sodium hexahydroxoaluminate :
a) [A1(H 2 O) 6 ] C1 3 ; b) Na; c) Na [A1(OH) 4 (H 2 0) 2 ]; d) NaAlO 2; e) Na 3?
3.What ions does tetraammine copper chloride form during electrolytic dissociation in water? (II) : C1 2: a) Cu 2+, Cl; b) 2+ , Cl; c) Cu 2+, NH 3, Cl; d) Cl; e) +, Cl?
Level II
1. From the answers given below, choose the one that characterizes the central ion and its charge in the compound Cl 2: a) Zn 2+; b) NH 3; c) 2+; d) Cl; e) N -3.
2. Which of the formulas below corresponds to tetraammine copper sulfate (II ):
a) SO 4 -H 2 O;
b) K;
c) Cl 2;
d) SO 4;
e) SO 4?
3. What ions does sodium diaquatetrahydroxoaluminate form during electrolytic dissociation in water? Na:
a) Na+; b) Al, OH", Na + ;
c) Na +, -;
d) Na +, OH";
e) Na + , - ?
For each correct answer (1 point)
UE-4. Preparation of complex compounds
Private didactic goals:
1. In practice, obtain complex compounds and study their properties.
2. Record chemical reactions in molecular and ionic form.
3. Be able to compose chemical formulas of complex compounds and name complexes.
Experience No. 1. Dissolution of amphoteric hydroxides in excess alkali.
Add alkali drop by drop to the aluminum sulfate solution, obtain a precipitate, then dissolve it in excess alkali.
1. Explain the results of the experiments.
2. Write down the equations of the reactions performed.
3. What is the spatial structure of the complex ion?
Add potassium hydroxide drop by drop to the zinc chloride solution until a white gelatinous precipitate of zinc hydroxide appears. Divide into two test tubes: add excess KOH to one, and ammonia solution to the other. What are you observing?
1. Write down equations for all the reactions carried out.
2. Determine the coordination number of the ion Zn 2+, charge of the complex ion, outer sphere.
To a solution of potassium rhodanite ( KCNS) add iron(III) chloride, get red blood salt, write down its formula, name the resulting complex.
KCNS + FeCl 3 = ? + KCl potassium rhodanite
1. Complete the equation of the reaction.
2. Write a short ionic equation.
3. What is the spatial structure of the complex ion?
For each correctly completed experiment you receive 2 points.
Exercise. Equalize the redox reactions using the electronic balance method or the half-reaction method, each equation (3 points).
Currently, gold is extracted from ores using the cyanide method proposed by Prince Pyotr Romanovich Bagration, the nephew of the hero of the war of 1812.
Example 1: Au + NaCN + H 2 O + O 2 -> Na + NaOH
Example 2: Dissolving gold in aqua regia.
Au + HNO 3 + HCl -> H + NO + H 2 O
UE-5. Practical application, significance of complex compounds
Private didactic goals:
1. Familiarize yourself with the use of complex compounds.
2.Qualitative reactions to metal ions.
3. Natural complexes(chlorophyll and hemoglobin).
Management. Explore the use of complex compounds.
The great Goethe said: “Just knowing is not everything; you need to be able to use knowledge.”
A number of complex compounds are used to recognize certain ions.
Yellow blood salt ( K 4) serves as a reagent for iron cations Fe, and red blood salt ( K 3) reagent for iron cations Fe.
Experience No. 4. Qualitative reaction on Fe ions.
Add 2-3 drops of yellow blood salt solution to the ferric chloride solution K 4 4K + + 4--
4Fe 3+ +3 4- -> Fe 4 3+ 3 4--
Prussian blue(dark blue precipitate)
A dark blue precipitate of Prussian blue, or iron(I) hexacyanoferrate(II), is formed. Prussian blue was accidentally obtained in 1704 by the German master Diesbach, who was preparing paints for artists. In Russia it was used for coloring fabrics, paper, in icon painting and in the creation of frescoes.
Yellow blood salt (hydrocyanate potash, blue-kali) is a poisonous substance. This compound was obtained from animal waste (blood, hooves, skins, dry fish, leather, meat, wool, etc.), which is why it has this name. It could only be purchased in Russia with the permission of the police.
Experience No. 5. Qualitative reaction to Fe 2+ ions.
Add a few drops of red blood salt solution to the iron(II) sulfate solution. K 3. In solution, this salt dissociates into ions.
K 3 3K + z-
3Fe +2 = Fe 3 2
Turnbull blue
A dark blue precipitate of Turnboule blue, or iron(I) hexacyanoferrate(III), is formed. Turnbull blue is named after Turnbull (grandfather of the English physicist and chemist W. Ramsay), who owned a factory that produced substances used for dyeing fabrics.
So the connections K 4 are important analytical reagents for Fe 3+ and Fe 2+ cations, respectively.
Conclusion: complex compounds are extremely diverse in composition and structure, since there can be many different combinations not only of different, but also of the same components.
UE-6.Properties of complex compounds
Objectives: to consider the influence of the structure of complexes on their properties.
1) Study of the influence of the structure of the metal ion on the color of the complexes
Different numbers of d-electrons, different coordination numbers, hence different colors.
2) Comparison of color intensity of copper complex compounds.
The color depends on the strength of the influence of the particles, i.e. ligands in the inner sphere, the color changes.
3) The color of the complexes depends on the nature and number of ligands surrounding the central atom (cation).
Several cobalt complex compounds have been obtained and are widely used in practice, which have the same high-quality composition, but differ in the number and nature of the connection of the components. These substances are part of dyes (cobalt paints). They are colored differently:
The color of the complexes depends on the nature and number of ligands surrounding the central atom (cation).
UE-7. Resume. Summing up the lesson.
1.Read the lesson objectives (UE-0).
2. Have you achieved the objectives of the lesson?
3. What did you achieve as a result of mastering the topic?
UE-8. Control
I level
1. Determine the outer and inner sphere, the charge of the complex ion, the dissociation of the complex:
3.* Equalize using the half-reaction method:
Zn + NaOH + H 2 O -> Na 2 + H 2
Be + KOH + H 2 O -> K 2 + H 2
Task. What volume of hydrogen will be released if you “dissolve”: 140 g of zinc with 10% impurities? 36 g of beryllium, with a hydrogen yield of 70% (n.o.)
Level II
1. Write down the dissociation, determine the oxidation state of the central ion, coordination number, name the compounds:
3*.Equalize using the half-reaction method:
Option I
a) Si + HNO 3 + HF -> H 2 + NO + H 2 O
Task. What mass of silicon with 20% impurities will dissolve if 67.5 liters of nitrogen(II) oxide (n.s.) are released?
Option II
a) Cu + KCN + H 2 O -> K + KOH + H 2
b) What volume of hydrogen will be released at a yield of 60% if 69 g of copper is dissolved with 10% impurities?
Structure of complex compounds
Attractive forces act not only between atoms, but also between molecules. The interaction of molecules often leads to the formation of other, more complex molecules. For example, under appropriate conditions, gaseous substances pass into a liquid and solid state of aggregation; any substance is to some extent soluble in another substance. In all these cases, mutual coordination of interacting particles is observed, which can be defined as complexation. The reason for complex formation can be both electrostatic and donor-acceptor interactions carried out between ions and molecules, between molecules.
Basics modern ideas the structure of complex compounds was laid down by the Swiss chemist Alfred Werner in 1893.
Complex connections - these are compounds characterized by the presence of at least one covalent bond, which arose according to the donor-acceptor mechanism.
At the center of each complex there is an atom called the central or complexing agent. Atoms or ions directly bonded to the central atom are called ligands. The number indicating how many ligands the complexing agent holds is called coordination number. The complexing agent and ligands form inner sphere . The inner sphere is separated from the outer sphere by square brackets. Outside the complex there are ions that have a charge opposite in sign compared to the charge of the complex itself - these ions make up outer sphere.
For example: K3
external internal
sphere
Fe 3+ - complexing agent; CN - ligand; 6 - coordination number;
3- - complex ion.
Nomenclature of complex compounds
To name complex compounds use complex system nomenclature rules.
1. The names of complex compounds consist of two words denoting the internal and external sphere.
2. For the internal sphere, indicate:
Number of ligands;
Ligand name;
Central atom with valency.
3. According to international nomenclature, the cation is called first, then the anion.
4. If the connection includes complex cation, then it is given Russian name for a complexing element.
5. If the connection includes complex anion, then the complexing agent the Latin name of the element is given with the ending "-at".
6. In neutral complexes, the oxidation state of the central atom is not indicated.
7. The names of ligands in most cases coincide with the usual names of substances. The suffix “-o” is added to anionic ligands.
For example: CN - - cyano, NO2 - - nitro, CI - - chloro, OH - - hydroxo, H + -hydro, O 2- - oxo, S 2- - thio, CNS - - rhodano or titianato, C2O4 2- - oxalato, etc.
8. Ligands - neutral molecules have specific names:
Water is aqua, ammonia is amine, carbon monoxide (II) is carbonyl.
9. The number of ligands is indicated by Latin or Greek numerals:
| Mono | |
| Di | |
| Three | |
| Tetra | |
| Penta | |
| Hexa | |
| Hepta | |
| Okta |
10. In mixed-ligand complexes Anionic ligands are listed first, followed by molecular ligands. If there are several different anionic or molecular ligands, they are listed alphabetically.
Examples
CI - diammine silver(I) chloride
K - potassium dicyanoargenate (I)
CI3 - chloropentaammineplatinum(IV) chloride or chloropentaammineplatinum trichloride
K - potassium pentachloroammine platinate (IV)
SO4 - chloronitrotriammineplatinum(II) sulfate.
K3-potassium hexacyanoferrate (III),
- trinitrotriammine cobalt.
3. Classification of complexes.
By character electric charge There are cationic, anionic and neutral complexes. The charge of a complex is the algebraic sum of the charges of the particles that form it.
Cationic the complex is formed as a result of coordination around the positive ion of neutral molecules (H2O, NH3, etc.)
Compounds containing amino complexes (NH3) are called ammonia, containing aqua complexes (H2O) - hydrates.
As a complexing agent in anionic in the complex there is an atom with a positive oxidation state (positive ion), and the ligands are atoms with a negative oxidation state (anions). For example: K2 - potassium tetrafluoroberyllate (II).
Neutral complexes are formed by coordination around an atom of molecules, as well as by simultaneous coordination around a positive complexing ion of negative ions and molecules. For example: - dichlorodiammineplatinum (II). Electroneutral complexes are complex compounds without an outer sphere.
Any element can play the role of a complexing agent periodic table. Nonmetallic elements usually form anionic complexes. Metal elements form cationic complexes.
Ligands. Various complexing agents can coordinate three types of ligands around themselves:
1. Anionic type ligands - elementary and complex negatively charged ions, for example hylide, oxide, hydroxide, nitrate, carbonate ions, etc.
2. Neutral ligands can be polar molecules of water, ammonia, etc.
3. Cationic type ligands are rare and coordinate only around negatively polarized atoms. Example: positively polarized hydrogen atom.
Ligands that form one bond with the central atom are called bidentate. Ligands capable of forming three or more bonds with the central atom are called polydentate. Complex compounds with bi- and polydentate ligands are called chelate complexes.
Common ligands that form a single bond with a metal are called monodentate.
4. Dissociation of complex compounds. Instability constant.
Complex compounds - electrolytes, upon dissociation in aqueous solutions form complex ions, for example:
CI = + + CI -
This dissociation occurs completely. Complex ions, in turn, undergo secondary dissociation.
Complex connections These are molecular or ionic compounds formed by the addition of a metal or nonmetal, neutral molecules or other ions to an atom or ion. They can exist both in crystal and in solution.
Basic provisions and concepts of coordination theory.
To explain the structure and properties of complex compounds, in 1893 the Swiss chemist A. Werner proposed a coordination theory into which he introduced two concepts: coordination and secondary valency.
According to Werner main valency is called valency by which atoms are combined to form simple compounds that obey the theory
valence. But, having exhausted the main valency, the atom is, as a rule, capable of further addition due to secondary valency, as a result of the manifestation of which a complex compound is formed.
Under the influence of the forces of primary and secondary valence, atoms tend to evenly surround themselves with ions or molecules and thus act as a center of attraction. Such atoms are called central or complexing agents. Ions or molecules directly bound to the complexing agent are called ligands.
Ligands and ions are attached through the main valence, and ions and molecules are added through the secondary valence.
The attraction of a ligand to a complexing agent is called coordination, and the number of ligands is called the coordination number of the complexing agent.
We can say that complex compounds are compounds whose molecules consist of a central atom (or ion) directly associated with a certain number of other molecules or ions, called ligands.
Metal cations (Co +3, Pt +4, Cr +3, Cu +2 Au +3, etc.) most often act as complexing agents.
Cl -, CN -, NCS -, NO 2 -, OH -, SO 4 2- ions and neutral molecules NH 3, H 2 O, amines, amino acids, alcohols, thioalcohols, PH 3, ethers can act as ligands.
The number of coordination sites occupied by a ligand near a complexing agent is called its coordination capacity or dentacy.
Ligands attached to the complexing agent by one bond occupy one coordination site and are called monodentate (Cl -, CN -, NCS -). If the ligand is attached to the complexing agent through several bonds, then it is polydentate. For example: SO 4 2-, CO 3 2- are bidentate.
The complexing agent and ligands make up inner sphere compounds or complex (in formulas, the complex is enclosed in square brackets). Ions not directly associated with the complexing agent constitute external coordination sphere.
The outer sphere ions are bound less tightly than the ligands and are spatially distant from the complexing agent. They are easily replaced by other ions in aqueous solutions.
For example, in compound K 3 the complexing agent is Fe +2, the ligands are CN -. Two ligands are attached due to the main valence, and 4 - due to the secondary valence, therefore the coordination number is 6.
The Fe +2 ion with ligands CN - constitute inner sphere or complex, and K ions + outer coordination sphere:
As a rule, the coordination number is equal to twice the charge of the metal cation, for example: singly charged cations have a coordination number equal to 2, 2-charged - 4, and 3-charged - 6. If an element exhibits a variable oxidation state, then with an increase in its coordination number increases. For some complexing agents, the coordination number is constant, for example: Co +3, Pt +4, Cr +3 have a coordination number equal to 6, for the B +3, Be +2, Cu +2, Au +3 ions the coordination number is 4. for For most ions, the coordination number is variable and depends on the nature of the ions in the outer sphere and on the conditions for the formation of complexes.
