Cu nh3 4 no3 2 name. Nomenclature of complex compounds. Examples of obtaining complex compounds
Task 723.
Name the complex salts: Cl, (NO 3) 2, CNBr, NO 3, Cl, K 4, (NH 4) 3, Na 2, K 2, K 2. K 2.
Solution:
C is chlorotriamminacquapalladium (II) chloride;
(NO 3) 2 - tetraamine copper (I) nitrate;
CNB - tetraaminediaquacobalt (II) cyanobromide;
NO 3 - sulfatopentaamminecobalt (III) nitrate;
Cl is palladium (II) chlorotetraammine chloride;
K 4 - potassium hexacyanoferrate (II);
(NH 4) 3 - ammonium hexachlororodinate (II);
Na 2 - sodium tetraiodopalladinate (II);
K 2 - potassium tetranitratodiammine cobaltate (II);
K 2 - potassium chloropentahydroxoplatinate (IV);
K 2 - potassium tetracyanocupriate (II).
Task 724.
Write the coordination formulas of the following complex compounds: a) potassium dicyanoargentate; b) potassium hexanitrocobaltate (III); c) chloride hexaamminenickel (II); d) sodium hexacyanochromate (III); e) bromide of hexaamminecobalt (III); f) tetraammine carbonate chromium sulfate (III) g) diaquatetraammine nickel nitrate (II); h) magnesium trifluorohydroxoberyllate.
Solution:
a) K - potassium dicyanoargentate;
b) K 3 - potassium hexanitrocobaltate (III);
c) Cl - hexaamminenickel (II) chloride;
d) Na 3 - sodium hexacyanochromate (III);
e) Cl 3 - bromide of hexaamminecobalt (III);
f) SO 4 2 - - tetraammine carbonate chromium (III) sulfate;
g) (NO 3) 2 - diaquatetraamminickel nitrate (II);
h) Mg magnesium trifluorohydroxoberyllate.
Task 725.
Name the following electrically neutral complex compounds:,,,,.
Solution:
, - tetraaquaphosphate chromium;
- dirodanodiammine copper;
- palladium dichlorodihydroxylamine;
- trinitrotriaminrodium;
- tetrachlorodiammineplatinum.
Task 726.
Write the formulas for the listed complex non-electrolytes: a) tetraammine phosphatochrome; b) diamminedichloroplatinum; c) triammine trichlorocobalt; d) diammintetrachloroplatin. In each of the complexes, indicate the degree of oxidation of the complexing agent.
Solution:
a) - tetraammine phosphatochrome. The charge of Cr is (x), NH 3 - (0), PO 4 - (-3). Hence, taking into account that the sum of the charges of the particles is equal to (o), we find the charge of chromium: x + 4 (0) + (-3) = 0; x = +3. Oxidation state chromium is +3.
b) - diamminedichloroplatinum. The charge of Pt is (x), NH 3 - (0), Cl - (-1). Hence, taking into account that the sum of the charges of the particles is equal to (0), we find the charge of platinum: x +4 (0) + 2 (-1) = 0; x = +2. Oxidation state platinum is +2.
c) - triammine trichlorocobalt. The charge of Co is (x), NH 3 - (0), Cl - (-1). Hence, taking into account that the sum of the particle charges is equal to (o), we find the cobalt charge: x + 3 (0) + 3 (-1) = 0; x = +3. Oxidation state cobalt is +3.
d) - diammintetrachloroplatin. The charge of Pt is (x), NH 3 - (0), Cl - (-1). Hence, taking into account that the sum of the charges of the particles is equal to (0), we find the charge of platinum: x +4 (0) + 4 (-1) = 0; x = +4. Oxidation state platinum is +2.
Task 727.
The chemical names of yellow and red blood salt are potassium hexacyanoferrate (II) and potassium hexacyanoferrate (III). Write the formulas for these salts.
Solution:
K 4 - potassium hexacyanoferrate (II) (yellow blood salt);
K 3 - potassium hexacyanoferrate (III) (red blood salt).
Task 728.
Brick Red Crystals roseosalts have a composition expressed by the formula Cl 3, purpureosol- crimson-red crystals of composition Cl 2. Lead chemical names these salts.
Solution:
a) Roseosol Cl 3 is called aquapentaamminecobalt (III) chloride.
b) Purpureosol Cl 2 is called aquapentaamminecobalt (II) chloride.
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 ligands-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. Intraspheric NH 3 is called ammino, H 2 O - aqua, CO - carbonyl, NO - nitrosyl. The number of ligands is indicated by Greek numbers: 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 platinate (II) chlorotriammine platinum (II).
For complexes with ambidentate ligands, the name indicates the symbol of the atom with which this ligand is bonded 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(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, for example, ethylenediamine (Fig. 3).
According to Chugaev's 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.
All inorganic compounds are divided into two groups:
1. connections of the first order, i.e. compounds obeying the theory of valence;
2. higher order compounds, i.e. compounds that do not obey the concepts of valence theory. Higher-order compounds include hydrates, ammonia, etc.
CoCl 3 + 6 NH 3 = Co (NH 3) 6 Cl 3
Werner (Switzerland) introduced the concept of higher-order compounds into chemistry and gave them a name complex compounds... He attributed all the most stable higher-order compounds to CS, which in an aqueous solution either do not disintegrate into their constituent parts at all, or disintegrate to an insignificant extent. In 1893, Werner suggested that any element after saturation is capable of exhibiting additional valence as well - coordination... According to Werner's coordination theory, each COP is distinguished:
Cl 3: complexing agent (KO = Co), ligands (NH 3), coordination number (CN = 6), inner sphere, external environment (Cl 3), coordination capacity.
The central atom of the inner sphere, around which ions or molecules are grouped, is called complexing agent. The role of complexing agents is most often performed by metal ions, less often by neutral atoms or anions. Ions or molecules coordinating around a central atom in the inner sphere are called ligands... Ligands can be anions: Г -, ОН-, СN-, CNS-, NO 2 -, CO 3 2-, C 2 O 4 2-, neutral molecules: Н 2 О, СО, Г 2, NH 3, N 2 H 4. Coordination number - the number of places in the inner sphere of the complex that can be occupied by ligands. CN is usually higher than the oxidation state. CN = 1, 2, 3, 4, 5, 6, 7, 8, 9, 12. The most common CN = 4, 6, 2. These numbers correspond to the most symmetric configuration of the complex - octahedral (6), tetrahedral (4) and linear (2). KCH depending on the nature of the complexing agent and ligands, as well as on the size of KO and ligands. Coordination capacity of ligands- the number of sites in the inner sphere of the complex occupied by each ligand. For most ligands, the coordination capacity is unity ( monodentate ligands), less often two ( bidentate ligands), there are ligands with a higher capacity (3, 4, 6) - polydental ligands... The charge of the complex must be numerically equal to the total of the outer sphere and opposite in sign. 3+ Cl 3 -.
Nomenclature of complex compounds. Many complex compounds have retained their historical names associated with color or with the name of the scientist synthesizing them. The IUPAC nomenclature is currently used.
Order of enumeration of ions... The first is the anion, then the cation, while the root of the Latin name KO is used in the name of the anion, and in the name of the cation - its Russian name in the genitive case.
Cl is diammine silver chloride; K 2 - potassium trichlorocuprate.
Ligand enumeration order... The ligands in the complex are listed in the following order: anionic, neutral, cationic - without hyphenation. Anions are listed in the order H -, O 2-, OH -, simple anions, complex anions, polyatomic anions, organic anions.
SO 4 - chloronitrsulfate (+4)
End of coordination groups. Neutral groups are named the same as molecules. Exceptions are aqua (H 2 O), amine (NH 3). The vowel "O" is added to the negatively charged anions
- hexocyanoferrate (+3) hexaaminocobalt (+3)
Prefixes indicating the number of ligands.
1 - mono, 2 - di, 3 - three, 4 - tetra, 5 - penta, 6 - hexa, 7 - hepta, 8 - octa, 9 - nona, 10 - deca, 11 - indica, 12 - dodeca, many - poly.
Prefixes bis-, tris- are used before ligands with complex names, where there are already prefixes mono-, di-, etc.
Cl 3 - tris (ethylenediamine) iron chloride (+3)
In the names of complex compounds, the anionic part is indicated first in the nominative case and with the suffix -at, and then the cationic part in the genitive case. However, before the name of the central atom in both the anionic and cationic parts of the compound, all ligands coordinated around it are listed with an indication of their number in Greek numerals (1 - mono (usually omitted), 2 - di, 3 - three, 4 - tetra, 5 - penta, 6 - hexa, 7 - hepta, 8 - octa). The suffix -o is added to the names of the ligands, and at first the anions are called, and then the neutral molecules: Cl- - chloro, CN- - cyano, OH- - hydroxo, C2O42- - oxalato, S2O32- - thiosulfato, (CH3) 2NH - dimethylamino and etc. Exceptions: The names of H2O and NH3 as ligands are “aqua” and “ammine”. If the central atom is part of the cation, then the Russian name of the element is used, after which its oxidation state is indicated in brackets in Roman numerals. For the central atom in the anion, the Latin name of the element is used and the oxidation state is indicated in front of this name. For elements with a constant oxidation state, it can be omitted. In the case of non-electrolytes, the oxidation state of the central atom is also not indicated, since it is determined based on the electroneutrality of the complex. Examples of titles:
Cl2 - dichloro-tetrammine-platinum (IV) chloride,
OH - diammine-silver hydroxide (I).
Classification of complex compounds. Several different classifications of COPs are used.
1. by belonging to a certain class of compounds:
complex acids - H 2
complex bases -
complex salts - K 2
2. By the nature of ligands: aqua complexes, ammonia. Cyanide, halide, etc.
Aquacomplexes are complexes in which water molecules serve as ligands, for example, Cl 2 - hexaaquacalcium chloride. Ammonia and amine - complexes in which ligands are molecules of ammonia and organic amines, for example: SO 4 - tetrammine copper (II) sulfate. Hydroxocomplexes. OH- ions serve as ligands in them. Especially typical for amphoteric metals. Example: Na 2 - sodium tetrahydroxozincate (II). Acidocomplexes. In these complexes, the ligands are acid anions, for example K 4 - potassium hexacyanoferrate (II).
3. by the sign of the charge of the complex: cationic, anionic, neutral
4.on the internal structure of the COP: by the number of nuclei making up the complex:
mononuclear - H 2, dual - Cl 5, etc.,
5. for the absence or presence of cycles: simple and cyclic CS.
Cyclic or chelate (chelate) complexes. They contain a bi- or polydentate ligand, which, as it were, captures the central M atom like the claws of a cancer: Examples: Na 3 - sodium trioxalato (III) ferrate, (NO 3) 4 - triethylenediamino platinum (IV) nitrate.
The group of chelate complexes also includes intracomplex compounds in which the central atom is part of the cycle, forming bonds with ligands different ways: on exchange and donor-acceptor mechanisms. Such complexes are very typical for aminocarboxylic acids, for example, glycine forms chelates with Cu 2+, Pt 2+ ions:
Chelated compounds are particularly strong, since the central atom in them is, as it were, blocked by a cyclic ligand. The most stable are chelates with five- and six-membered rings. Complexones bind metal cations so strongly that when they are added, such poorly soluble substances as CaSO 4, BaSO 4, CaC 2 O 4, CaCO 3 dissolve. Therefore, they are used for softening water, for binding metal ions during dyeing, processing photographic materials, in analytical chemistry. Many complexes of the chelate type have a specific color and therefore the corresponding ligand compounds are very sensitive reagents for transition metal cations. For example, dimethylglyoxime [C (CH 3) NOH] 2 serves as an excellent reagent for cations Ni2 +, Pd2 +, Pt2 +, Fe2 +, etc.
Stability of complex compounds. Instability constant. Upon dissolution of the CW in water, decomposition occurs, and the inner sphere behaves as a single whole.
K = K + + -
Along with this process, dissociation of the inner sphere of the complex occurs to an insignificant extent:
Ag + + 2CN -
To characterize the stability of the CS, we introduce instability constant equal to:
The instability constant is a measure of the strength of the CS. The less K nest, the more durable the COP.
Isomerism of complex compounds. For complex compounds, isomerism is very common and is distinguished:
1.solvate isomerism is found in isomers when the distribution of water molecules between the inner and outer spheres is unequal.
Cl 3 Cl 2 H 2 O Cl (H 2 O) 2
Purple light green dark green
2.Ionization isomerism associated with the different ease of dissociation of ions from the inner and outer spheres of the complex.
4 Cl 2] Br 2 4 Br 2] Cl 2
SO 4 and Br - sulfate bromo-pentammine-cobalt (III) and bromide sulfato-pentammine-cobalt (III).
Cl and NO 2 - chloride-nitro-chloro-diethylenediamino-cobalt (III) and nitrite dichloro-diethylenediamino-cobalt (III).
3. Coordination isomerism found only in bicomplex compounds
[Co (NH 3) 6] [Co (CN) 6]
Coordination isomerism occurs in those complex compounds where both the cation and the anion are complex.
For example, - tetrachloro- (II) platinate of tetrammine-chromium (II) and - tetrachloro- (II) chromate of tetrammine-platinum (II) are coordination isomers
4. Communication isomerism arises only when monodentate ligands can coordinate through two different atoms.
5. Spatial isomerism due to the fact that the same ligands are located around the KO or near (cis), or on the contrary ( trance).
Cis isomer (orange crystals) trans isomer (yellow crystals)
Dichloro-diammine-platinum isomers
With a tetrahedral arrangement, cis-trans ligand isomerism is impossible.
6. Mirror (optical) isomerism, for example, in the dichloro-diethylenediamino-chromium (III) + cation:
As in the case of organic substances, mirror isomers have the same physical and chemical properties and differ in the asymmetry of crystals, the direction of rotation of the plane of polarization of light.
7. Ligand isomerism , for example, for (NH 2) 2 (CH 2) 4 the following isomers are possible: (NH 2) - (CH 2) 4 -NH 2, CH 3 -NH-CH 2 -CH 2 -NH-CH 3, NH 2 -CH (CH 3) -CH 2 -CH 2 -NH 2
Communication problem in complex compounds. The nature of the bond in the CS is different and three approaches are currently used for explanation: the VS method, the MO method, and the crystal field theory method.
Sun method introduced Pauling. The main provisions of the method:
1. The bond in the CC is formed as a result of donor-acceptor interaction. The ligands provide electron pairs, and the complexing agent provides free orbitals. A measure of bond strength is the degree of overlapping of the orbitals.
2. KO orbitals undergo hybridization, the type of hybridization is determined by the number, nature, and electronic structure of the ligands. KO hybridization is determined by the geometry of the complex.
3. Additional strengthening of the complex occurs due to the fact that, along with the s-bond, p-bond is formed.
4. The magnetic properties of the complex are determined by the number of unpaired electrons.
5. During the formation of a complex, the distribution of electrons in the orbitals can remain both for neutral atoms and undergo changes. It depends on the nature of the ligands, its electrostatic field. The spectrochemical range of ligands has been developed. If the ligands have a strong field, then they displace the electrons, causing them to pair and form a new bond.
Spectrochemical range of ligands:
CN -> NO 2 -> NH 3> CNS -> H 2 O> F -> OH -> Cl -> Br -
6. The VS method makes it possible to explain the formation of bonds even in neutral and cluster complexes
K 3 K 3
1. In the first CS, the ligands create a strong field, in the second, a weak
2. Draw the valence orbitals of iron:
3. Consider donor properties of ligands: CN - have free electron orbitals and can be donors of electron pairs. CN - has a strong field, acts on 3d orbitals, densifying them.
As a result, 6 bonds are formed, while internal 3D orbitals are involved in the bond, i.e. an intraorbital complex is formed. The complex is paramagnetic and low-spin, because there is one unpaired electron. The complex is stable, because the inner orbitals are occupied.
Ions F - have free electron orbitals and can be donors of electron pairs, have a weak field, so they cannot condense electrons at the 3d level.
As a result, a paramagnetic, high-spin, external orbital complex is formed. Unstable and reactive.
Advantages of the VS method: informativeness
Disadvantages of the VS method: the method is suitable for a certain range of substances, the method does not explain the optical properties (color), does not make an energy assessment, because in some cases, a quadratic complex is formed instead of the more energetically favorable tetrahedral one.
Complex compounds are classified according to the charge of the complexes: cationic - 2+, anionic - 3-, neutral - 0;
by composition and chemical properties: acids - H, bases - OH, salts - SO4;
by the type of ligands: hydroxo complexes - K2, aqua complexes - Cl3, acido complexes (ligands - acid anions) - K4, mixed-type complexes - K, Cl4.
The names of the complexes are built according to the general IUPAC rules: read and write from right to left, ligands - with the ending - o, anions - with the ending - at. Some ligands may have specific names. For example, the molecules - ligands H2O and NH3 are called aquo and ammine, respectively.
Complex cations. Initially, the negatively charged ligands of the inner sphere with the ending "o" (chloro-, bromo-, nitro-, rhodano-, etc.) are called. If their number is more than one, then the numerals di-, tri-, tetra-, penta-, hexa-, etc. are added before the names of the ligands. Then they call neutral ligands, and the water molecule is called "aquo", the ammonia molecule is called "ammine". If the number of neutral ligands is more than one, then add the numerals di-, tri-, tetra-, etc.
Nomenclature of complex compounds
When composing the name of a complex compound, its formula is read from right to left. Let's consider specific examples:
Anionic complexes
Cationic complexes
K3 potassium hexacyanoferrate (III)
Na sodium tetrahydroxoaluminate
Na3 sodium hexanitrocobaltate (III)
SO4 tetraamminecopper (II) sulfate
Cl3 hexaaquachromium (III) chloride
OH hydroxide of diammine silver (I)
In the names of complex compounds, the number of identical ligands is indicated by numeric prefixes, which are written together with the names of the ligands: 2 - di, 3 - three, 4 - tetra, 5 - penta, 6 - hexa, 7 - hepta, 8 - octa.
The names of negatively charged ligands, anions of various acids, consist of the full name (or root of the name) of the anion and the ending with a vowel -o. For example:
I- iodo-
H- hydrido-
CO32- carbonate
Some anions that act as ligands have special names:
OH-hydroxo
S2- thio-
CN- cyano-
NO- nitroso-
NO2- nitro-
In the names of neutral ligands, special prefixes are usually not used, for example: N2H4 - hydrazine, C2H4 - ethylene, C5H5N - pyridine.
By tradition, special names have been left for a small number of ligands: H2O - aqua, NH3 - amine, CO - carbonyl, NO - nitrosyl.
The names of positively charged ligands end in -th: NO + - nitrosilium, NO2 + - nitroilium, etc.
If an element that is a complexing agent is part of a complex anion, then the suffix -at is added to the root of the name of the element (Russian or Latin) and the oxidation state of the element-complexing agent is indicated in brackets. (Examples are shown in the table above). If an element, which is a complexing agent, is part of a complex Katina or a neutral complex without an external sphere, then the Russian name of the element with an indication of its oxidation state remains in the name. For example: - tetracarbonyl nickel (0).
Many organic ligands have a complex composition, therefore, when drawing up the formulas of complexes with their participation, for convenience, their letter designations are used:
C2O42-oxalato-ox
C5H5N pyridine py
(NH2) 2CO urea ur
NH2CH2CH2NH2 ethylenediamine en
C5H5- cyclopentadienyl- cp
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 parent 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 that provide 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 electron pairs, 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 the 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 complex 3+, the ligands are electrically neutral molecules; therefore, the charge of 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, first they 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 -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 begin 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 decomposition 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. The 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, К 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.
From the above equations of the stepwise dissociation of the complex, it follows that intermediate dissociation products may be present in the solution; at an excessive concentration of the ligand due to the reversibility of these processes, the equilibrium of the reactions shifts towards the starting substances and, in the main, an undissociated complex is present in the solution.
To characterize the strength of the complex, in addition to the constant of instability of the complex, the reciprocal of it is used - the constant of stability of the complex b set. = 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.
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