Introduction to Transition Metals and Coordination Chemistry (CHMS3205)

BSc, Chemistry - CHMS

Semester: Second Semester

Level: 300

Year: 2016

Answers (200 )
THE UNIVERSITY OF BAMENDA
FACULTY OF SCIENCE
Department of Chemistry
SECOND SEMESTER EXAMINATION 2016
Course Instructor: Prof, Agwara M. Ondoh
Year: 2016
Course Code & Number: CHMS3205
Date: 7
th
July 2016
Course Title: introduction to Transition Metal and
Time: 11.00- 14.00 H
Coordination Chemistry
Credit Value: 6
Duration: 3 hours
INSTRUCTIONS: Answer all questions. Be brief and accurate
QUESTION 1 (12 marks)
a) Write the electronic configuration for each of the following transition metal atoms and
ions. Use [Ar] to represent the argon core configuration: Is
2
, 2s
2
, 2p
6
, 3s
2
, 3p
6
. (4 marks)
Cu
Mn
3+
Nl
2+
Co
b) Indicate the coordination number about the metal and the oxidation number of the
metal in each of the following coordination compounds and complexes: (4 marks)
[MnO
4
]
-
K[CuCI
2
] Na
4
Co(C
2
0
4
)
2
Br
2
]
[Cr(edta)]
-
Coordination
No
Oxidation No.
c) Identify the Lewis acid and the Lewis Base(s) inside the Coordination sphere of each of
the following complexes:
(i) [Cu(CO)6]SO
4
(ii) [Co(N0
2
)[NH
3
)
5
]Cl
2
(iii) [Rh(PPh
3
)
3
l
2
Cl] (iv) [Ni(en)
2
] (4 marks)
QUESTION 2 (16 Marks)
a) Explain the following:
i) [Pt(NH
3
)
2
Cl
2
] does not conduct electricity while [Pt(NH
3
)
6
]Cl
2
does.
ii) The conductivity of Na
3
[Fe(CN)
6
] is lower than that of Na4Fe(CN)
6
]
iii) K
4
[Fe(CN)
6
] is less stable than K
3
[Fe(CN)
6
]. (6 marks)
b) Define the Following terms (giving an example in each case) as used in Coordination
Chemistry (i) Chelate (it) Denticity (iii) Hopticity (iv) Double Salt (4 marks)
c) Using the EAN Rule, Predict the stability of the following complexes
(i) [Cr(CO)
6
] ii) [Fe(en)
3
]
3+
iii) [Fe(EDTA)]
2-
(6 marks)
QUESTION 3 (14 Marks)
a) Name the following complexes: (i) Na
2
[Ni(CN)
4
] (ii) [Mn(en)
2
|
2
]ClO
4
(iii) [V(NH
2
)
2
(NO)
2
]Cl
3
[iv] [C
O
Cl(ONO)(NH
3
](H
2
0)
2
]
(v) [Pt(NH
3
)
4
Cl
2
] [PtCl
6
] (5 marks)
b) Give the formula of the following complexes
i) diammine(ethylenediamine)copper (ii) tetrachloro(ethylenediamine)cobaltafe(ll)
ii) tetraammineoxalQtonickel(ll)
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iii) potassiumamminepentachloroplafinate (IV)
iv) potassium fetranitrodiamminecobaltate (lll) (4 marks)
c) A polladium complex formed from a solution containing bromide ions and pyridine is
found by elemental analyses to contain 37.6% Br, 28.3 % C. 6.6% N and 2.37% H. The
compound is slightly soluble in several organic solvents and its solution in water or alcohol
does not conduct electricity. The compound has zero dipole moment. Write the
chemical formula for the complex and comment on it. (5 marks)
QUESTION 4 (15 Marks)
a) Using the VBT, describe the bonding and Magnetism in [Co(CN)
6
]
3-
end [CoF
6
]
3-
(4 marks)
b) Give the indicated isomers for each of the following coordination compounds and
complexes: (11 marks)
i) Structural formula for the linkage isomer of [Cr[H
2
O)
5
(NO
2
)]and [Cr(H
2
O)
6
SCN]
2+
ii) Structural formula for the coordination-sphere isomer of [Co(en)2(NH3)(SCN)]CI
iii) Draw all possible stereoisomers of the octahedral complex, [Fe(en)(C
2
O
4
)Br
2
]
-
iv) Draw and name cll possible isomers of the square planar complex, [Pt(NH
3
)
2
[SCN)
2
]
QUESTION 5 (19 Marks)
a) What is crystal field splitting energy? [1 pt]
b) Draw a figure to show the splitting of d orbitals in an octahedral crystal field. [2 pts]
c) Which complex in the following pairs has the larger value of ∆
0
? [2 pts]
i) [Co(CN)
6
]
3-
and [C
O
(NH
3
)
6
]
3+
ii) [Co(H20)6l
3+
and |Co(H20)6p
d) Consider the complexes [Fe(en)
3
]
2+
and [FeCl
6
]
4-
. For each of the complexes, using the
Crystal Field Theory,
i) Describe the bonding in the complexes with aid of splitting diagrams;
ii) Calculate the Spin Only magnetic Moment of each central metal ion;
iii) Calculate the CFSE
iv) Compare the wavelengths of the colours of the two complex ions
v) If the ions are excited, write down the ground state and first excited state electronic
configuration of each ion.
e) A solution of [Ni(H
2
0)
6
]
2+
is green but a solution of (Ni(CN)
4
]
2-
is colourless. Explain. [2 marks]
f) [Fe(CN)
6
]
4-
and [Fe(H
2
0)
6
]
2+
are of different colours in dilute solutions. Why? (2 marks]
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