LECTURE 3LECTURE 3

Chelatometry. Introduction of Introduction of

biogenic elements biogenic elements chemistrychemistry

ass. prof.ass. prof. Ye. B. DmukhalskaYe. B. Dmukhalska

MINERALSMINERALS• Basic functions performed by the minerals

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• SO4

2- -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 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 The complexes formed by Cu (II) and Pt (II) ions with ethylenediamine are Pt (II) ions with ethylenediamine are metal chelates represented as metal chelates represented as follows:follows:

• Some important characteristics of chelates.Some important characteristics of chelates.• (i) Chelating ligands form more stable complexes (i) Chelating ligands form more stable complexes

than the monodentate analogs. This is called than the monodentate analogs. This is called chelating effectchelating effect..

• (ii) Chelating ligands, which do not contain double (ii) Chelating ligands, which do not contain double bonds e.g. ethylenediamine form five membered bonds e.g. ethylenediamine form five membered stable rings. The chelating ligands such as stable rings. The chelating ligands such as acetylacetone form six membered stable ring acetylacetone form six membered stable ring complexes.complexes.

• (iii) Ligands with large groups form unstable rings (iii) Ligands with large groups form unstable rings than the ligands with smaller groups due to steric than the ligands with smaller groups due to steric hindrance.hindrance.

• Coordination number.Coordination number. The total The total number of monodentate ligands (plus number of monodentate ligands (plus double the number of bi dentate double the number of bi dentate ligands if any) attached to the ligands if any) attached to the central metal ion through coordinate central metal ion through coordinate bonds is called the bonds is called the coordination coordination number of the metal ionnumber of the metal ion..

• [Ag(СN)[Ag(СN)22]]--, [Cu(NН, [Cu(NН33))44]]

2+2+ and and

[Cr(Н[Cr(Н22О)О)66]]33

Coordination sphere.Coordination sphere.

• The central atom and the ligands The central atom and the ligands which are directly attached to it are which are directly attached to it are enclosed in square brackets and are enclosed in square brackets and are collectively termed as the collectively termed as the coordination sphere.coordination sphere.

Oxidation number or oxidation Oxidation number or oxidation statestate..• It is а number that represents an electric charge

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.Charge on the complex ion.

• The charge carried by а complex ion The charge carried by а complex ion is the algebraic sum of the charges is the algebraic sum of the charges carried by central metal ion and the carried by central metal ion and the ligands coordinated to the central ligands coordinated to the central metal ion. metal ion.

• [Ag (CN)[Ag (CN)22]-]-

• [Cu (NH[Cu (NH33))44]]2+2+

Charge coordination number example

of the metal ion +1 2

Ag+, Cu+

+2 4, 6 Cu2+, Zn2+, Pd2+, Pt2+

+3 6, 4 Pt4+, Cr3+, Co3+, Fe3+

+4 8 Sn4+

Co-ordination Werner’s theory

•[Co(NН[Co(NН33))66] Cl] Cl33, hexaamminecobalt , hexaamminecobalt

(III) chloride.(III) chloride.

•KK22[PtCl[PtCl66], potassium ], potassium

hexachloroplatinate (IV).hexachloroplatinate (IV).

•[Co(NO[Co(NO22)(NH)(NH33))33], ],

triamminetrinitrocobalt (III)triamminetrinitrocobalt (III)

•[PtCl[PtCl44(NH(NH33))22], ],

diamminetetrachloroplatinum (IV).diamminetetrachloroplatinum (IV).

• (i) Negative ligands end in – o:• CN- (cyano), Cl- (chloro), Br- (bromo), F-

(fluorо), NO2- (nitro), ОН- (hydroxo), О2-

(охо), SO42-(sulphato), С2О2

2- (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.Types of complexes. • (i) А complex in which the complex ion (i) А complex in which the complex ion

carries а net positive charge is called carries а net positive charge is called cationic complex: [Co(NНcationic complex: [Co(NН33)])]

3+3+, [Ni(NH, [Ni(NH33))66]]2+2+

• (ii) А complex in which the complex ion (ii) А complex in which the complex ion carries а net negative charge is called carries а net negative charge is called anionic complex: [Ag(CN)anionic complex: [Ag(CN)22]]

--, [Fe (CN), [Fe (CN)66]]4-4-

• (iii) А complex carrying no net charge is (iii) А complex carrying no net charge is called а neutral complex or simply а called а neutral complex or simply а complex:complex:

• [Ni(CO)[Ni(CO)44], [CoCl], [CoCl33 (NН (NН33))33]]

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)

Polycentral compoyndsChain [Cr(NH3)5 – OH – (NH3)Cr]Cl3 chelaes (CO)5Mn – Mn(Co)5

Main types of complex compounds

MeO

O

O

O

C

CMe

NH2

NH2

CH2

CH2

CO

CH2 CH2

N NH2CHOOC COOHCH2

MeH2C CH2

CO

O O

Thank you for attention