LECTURE 3
Chelatometry.
Introduction of biogenic
elements chemistry
ass. prof. Ye. B. Dmukhalska
MINERALS
• Basic functions performed by the minerals
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are:
1. As structural components of body
tissues.
2. In the maintenance of acid-base balance.
3. In the regulation of body fluids.
4. In transport of gases.
5. In muscle contractions.
• In the human body and animals are
near 70 chemical elements, but 47
are called biogenic elements
• Six elements: carbon, hydrogen,
oxygen, nitrogen, phosphorus, sulfur;
are on amino acid, basic components
of albumen, and they are named
organogenic.
• 94 % of all living tissues contain only
4 elements: carbon, hydrogen,
oxygen, nitrogen.
• Depending on quantitative maintenance all
elements classified into macro-, micro- and
ultramicroelements.
• The macroelements are elements which more
then 0,01 % of body mass are on organism. It is
sodium, potassium, calcium, phosphorus,
chlorine, sulfur, magnesium.
• The microelements – 10-3–10-5 %. It is an
iodine, bromine, fluorine, iron, copper,
aluminium, magnesium, cobalt, zinc, strontium,
lithium, selenium, molybdenum.
• The ultramicroelements are elements which lest
then 10-5 %. It is a mercury, gold, chrome,
silicon, nickel.
Complex compounds
А) Structure
CuSO4 + 4 NH3 = [Cu (NH3)4] SO4
[Cu (NH3)4] SO4
Complex compound
• Cu2+ - central atom
•NH3 – ligand
• [Cu (NH3)4]2+ - complex ion
• SO42- -anion
• Coordination compounds are the
compounds in which the central metal
atom is linked to а number of ions or
neutral molecules by coordinate bonds
i.е. by donation of lone pairs of
electrons by these ions or neutral
molecules to the central metal atom.
• nickel tetracarbonyl, [Ni(CO)4]
• the species formed by linking of а number
of ions or molecules by co-ordinate bonds
to the central metal atom (or ion) carries
positive or negative charge, it is called a
complex ion. [Fe(СN)6]4-, [Cu(NH3)4]2+,
[Ag(CN)2]-
• The donor atoms, molecules or anions,
which donate а pair of electrons to the
metal atom and form co-ordinate bond
with it are called ligands.
• If only one donor atom is present in its
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molecule, which can coordinate, then it is called
as unidentate (monodentate). : NH3, Н2О
and CN-.
The ligand may contain two donor atoms
(coordinating groups) positioned in such а way
then it is called bidentate chelating ligand
The ring is called chelate ring and the resulting
complex is called а metal chelate.
• The complexes formed by Cu (II) and Pt
(II) ions with ethylenediamine are metal
chelates represented as follows:
• Some
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important
characteristics
of
chelates.
(i) Chelating ligands form more stable complexes
than the monodentate analogs. This is called
chelating effect.
(ii) Chelating ligands, which do not contain
double bonds e.g. ethylenediamine form five
membered stable rings. The chelating ligands
such as acetylacetone form six membered stable
ring complexes.
(iii) Ligands with large groups form unstable
rings than the ligands with smaller groups due
to steric hindrance.
• Coordination number. The total number
of monodentate ligands (plus double the
number of bi dentate ligands if any)
attached to the central metal ion through
coordinate bonds is called the
coordination number of the metal
ion.
• [Ag(СN)2]-, [Cu(NН3)4]2+ and [Cr(Н2О)6]3
Coordination sphere.
• The central atom and the ligands which
are directly attached to it are enclosed in
square brackets and are collectively
termed as the coordination sphere.
Oxidation number or oxidation state.
• It is а number that represents an electric charge
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which an atom or ion actually has or appears to
have when combined with other atoms,
oxidation number of copper in [Cu(NH3)4]2+ is
+2 but coordination number is 4.
oxidation number of Fe in [Fe(СN)6]3- is + 3 but
the coordination number is 6.
(i) [Cu (NНЗ)4]SO4.
(ii) Fe in [Fe (СN)6]3(iii)К3[Fe(С2О4)3].
(iv) [Ni(CO)4].
Charge on the complex ion.
• The charge carried by а complex ion is the
algebraic sum of the charges carried by
central metal ion and the ligands
coordinated to the central metal ion.
• [Ag (CN)2]• [Cu (NH3)4]2+
Co-ordination Werner’s theory
Charge
+1
+2
+3
+4
coordination number
example
of the metal ion
2
Ag+, Cu+
4, 6
Cu2+, Zn2+, Pd2+, Pt2+
6, 4
Pt4+, Cr3+, Co3+, Fe3+
8
Sn4+
• [Co(NН3)6] Cl3, hexaamminecobalt
(III) chloride.
• K2[PtCl6],
potassium
hexachloroplatinate (IV).
• [Co(NO2)(NH3)3],
triamminetrinitrocobalt (III)
• [PtCl4(NH3)2],
diamminetetrachloroplatinum (IV).
• (i) Negative ligands end in – o:
• CN- (cyano), Cl- (chloro), Br- (bromo), F-
(fluorо), NO2- (nitro), ОН- (hydroxo), О2(охо), SO42-(sulphato), С2О22- (oxalato), NН2(amido ), NH2- (imido), ONO- (nitrito), NO3(nitrato),
SCN(thiocyanato),
NCS(isothiocyanato),
СН2(NН2)COО(glycinato)etc.
• (ii) Neutral ligands have no special ending:
NН3 (ammine), Н2О (aqua), CO (carbonyl),
CS (thiocarbonyl) and NO (nitrosyl)
• (iii) Positive ligands (which are very few)
end in -ium, е.g., NН3+ (hydrazinium),
NO+ (nitrosonium), NО2+ (nitronium).
• (iv) Organic ligunds. Organic free radicals
are given their own names. For example,
СН3 (methyl), С2Н5 (ethyl), С6Н5 (phenyl),
С5Н5 (cyclopentadienyl).
• For organic neutral molecules, their names
are used. For example, Р(С6Н5)3,
triphenylphosphine;
• (v) Unidentate ligands with more than one
co-ordinating atoms. It is essential to
designate the point of attachment of а
ligand by placing the symbol of the donor
atom attached after that; name of the
groups separated by hyphen. These
ligands are called ambidentate ligands
е.g., in thiocyanate and nitrite ions, we
have two options each.
• — SCN, thiocyanate
- NО2- nitro
• — NCS, isothiocyanate - ONO, nitrite
Types of complexes.
• (i) А complex in which the complex ion carries а
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net positive charge is called cationic complex:
[Co(NН3)]3+, [Ni(NH3)6]2+
(ii) А complex in which the complex ion carries а
net negative charge is called anionic complex:
[Ag(CN)2]-, [Fe (CN)6]4(iii) А complex carrying no net charge is called а
neutral complex or simply а complex:
[Ni(CO)4], [CoCl3 (NН3)3]
Main types of complex compounds
1. With one central atom
• Ammonia complex [Cu(NH3)4]SO4
• Aqua complex[Al(H2O)6]Cl3
• acidic complex K2[PtCl4]
• complex with difference ligands K[Pt(NH3)Cl3]
• cyclic (chelates)
Me
NH2 CH2
NH2 CH2
Me
O
O
C
C
O
O
HOOC H2C
CH2
N
N
Me
H2C
Polycentral compoynds
Chain
[Cr(NH3)5 – OH – (NH3)Cr]Cl3
chelaes
(CO)5Mn – Mn(Co)5
CH2
O
O
CH2
CH2
C
C
O
O
COOH
Thank you for attention