On the basis of valence bond theory explain the oxidation state, hybridisation, geometry and magnetic nature of metal in complex CoF 6 3 - .

Oxidation state of cobalt in the complex, X + - 1 × 6 = - 3 X = + 3 Therefore, in the complex CoF 6 3 - cobalt is in + 3 oxidation state. The electronic configuration of cobalt is Co 27 - Ar 3 d 7 4 s 2 The electronic configuration of Co 3 + - Ar 3 d 6 4 s 0 . The one 4 s , three 4 p and two 4 d orbitals of cobalt are hydridised forming six sp 3 d 2 . Six pairs of electrons, each from F - ion are donated to the vacant hybrid orbital forming Co - F bond. Thus, the complex has octahedral geometry. The 3 d orbital has four unpaired electrons. Therefore, it is paramagnetic in nature.

Write IUPAC name of the following complex. K 3 [ Fe ( C 2 O 4 ) 3 ]

The coordination compounds are named in the following way, To name a coordination compound, no matter whether the complex ion is the cation or the anion, always name the cation before the anion. In naming the complex ion: Name the ligands first, in alphabetical order, then the metal atom or ion. Note: The metal atom or ion is written before the ligands in the chemical formula. Greek prefixes are used to designate the number of each type of ligand in the complex ion, e.g. di-, tri- and tetra-. If the ligand already contains a Greek prefix (e.g. ethylenediamine) or if it is polydentate ligands (ie., can attach at more than one binding site) the prefixes bis-, tris-, tetrakis-, pentakis-, are used instead. After naming the ligands, name the central metal. If the complex ion is a cation, the metal is named same as the element. Following the name of the metal, the oxidation state of the metal in the complex is given as a Roman numeral in parentheses. Thus, the IUPAC name of the complex: K 3 [ Fe ( C 2 O 4 ) 3 ] is Potassium trioxalatoferrate(III).

Write the geometry and magnetic nature of the complex ion NiCl 4 2 - , on the basis of valence bond theory.

The atomic number of nickel is 28 . The electronic configuration of nickel is Ar 3 d 8 4 s 2 . The oxidation state of nickel in the complex NiCl 4 2 - is + 2 . The outer electronic configuration of Ni 2 + = Ar 3 d 8 4 s 0 4 p 0 Chlorine is a weak ligand, therefore, the outer electrons of nickel are not paired up. Hence, the hybridisation state of nickel is sp 3 , and the geometry of NiCl 4 2 - is tetrahedral. Due to the presence of two unpaired electrons, it shows paramagnetism behaviour.

Write the IUPAC name of the complex K 3 Fe C 2 O 4 3 .

K 3 Fe C 2 O 4 has three oxalate ions as a ligand and three potassium atoms. Oxalate ion carries - 2 charge, and potassium carries + 1 charge. So, the total charge of oxalate ion and potassium ion are - 6 and + 3 respectively. Hence, the oxidation state of the central metal is + 3 . According to IUPAC rules, IUPAC name of the complex K 3 Fe C 2 O 4 3 is potassium trioxalatoferrate III .

Write oxidation state of Ni in Ni CO 4 .

The oxidation state of CO = 0 The oxidation state of complex = 0 So, it means that CO is a neutral ligand, so the oxidation state of nickel will be 0 .

Give the oxidation state and coordination number of the central metal ion in the following complexes. (ii) K 4 Fe CN 6

The oxidation number of potassium = + 1 The oxidation number of cyanide ligand = - 1 Let the oxidation number of the central metal ion is X , then ⇒ + 1 × 4 + X + - 1 × 6 = 0 ⇒ 4 + X - 6 = 0 ⇒ X = + 2 So, the oxidation state of iron is + 2 . The coordination number is defined as the number of ligands or donor atoms directly attached to the central metal ion. So, the coordination number of the central metal ion in the given complex is 6 .

Give the oxidation state and coordination number of the central metal ion in the following complexes. (I) Co en 3 3 +

Given complex: Co en 3 3 + The oxidation state of complex = + 3 The oxidation state of the ligand = 0 (Neutral ligand) So, the oxidation state of the central metal ion ⇒ X + 3 × 0 = + 3 ⇒ X = + 3 The coordination number can be defined as the number of atoms directly attached to the central metal ion. The ethylene diamine is a bidentate ligand, therefore, the coordination number of the central metal ion in Co en 3 3 + is 6 .

Give any one example of bidentate ligand.

The ligands having two donor atoms, and they form two coordination bonds with central metal or ion are called bidentate ligands. An example of the bidentate ligand is the oxalate ion C 2 O 4 2 - .

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Write the definition of ambidentate ligands.

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