Coordination Compounds Flashcards
1
Q
Coordination compounds find use in many qualitative and quantitative chemical analysis
Examples of such reagents include EDTA, DMG (dimethylglyoxime), α–nitroso–β–naphthol, coupon, etc.
A
Both are correct
2
Q
Hardness of water is estimated by simple titration with…….
A
Na2EDTA
3
Q
The Ca2+ and Mg2+ ions form stable complexes with EDTA.
The selective estimation of these ions can be done due to the difference in the stability constants of calcium and magnesium complexes.
A
Both are correct
4
Q
Some important extraction processes of metals, like those of silver and gold, make use of complex formation. Gold, for example, combines with cyanide in the presence of……….. and ………… to form the coordination entity [Au(CN)2]– in aqueous solution. Gold can be separated in metallic form from this solution by the addition of………..
A
oxygen and water
zinc
5
Q
Statement 1: Similarly, purification of metals can be achieved through formation and subsequent decomposition of their coordination compounds.
Statement 2: For example, impure nickel is converted to [Ni(CO)4], which is decomposed to yield pure nickel.
A
Both are true
6
Q
……………… cyanocobalamin, the anti–pernicious anaemia factor, is a coordination compound of cobalt.
A
Vitamin B12
7
Q
rhodium complex……………
a Wilkinson catalyst, is used for the hydrogenation of alkenes.
A
[(Ph3P)3RhCl]
8
Q
Articles can be electroplated with silver and gold much more smoothly and evenly from solutions of the complexes…………………than from a solution of simple metal ions.
A
[Ag(CN)2]– and [Au(CN)2]–
9
Q
In black and white photography, the developed film is fixed by washing with hypo solution which dissolves the undecomposed………….to form a complex ion…………….
A
AgBr
[Ag(S2O3)2]3–.
10
Q
Statement 1: There is growing interest in the use of chelate therapy in medicinal chemistry.
Statement 2: excess of copper and iron are removed by the chelating ligands D–penicillamine and desferrioxamine B via the formation of coordination compounds
A
Both are correct
11
Q
Statement 1: EDTA is used in the treatment of lead poisoning.
Statement 2: Some coordination compounds of platinum effectively inhibit the growth of tumours. Examples are cisplatin and related compounds.
A
Both are correct
12
Q
Chlorophyll, haemoglobin and vitamin B12 are coordination compounds with what metals
A
Magnesium
Iron
Cobalt
13
Q
……………. (1866-1919), a Swiss chemist was the first to formulate his ideas about the structures of coordination compounds.
A
Alfred Werner
14
Q
Werner in 1898, propounded his theory of coordination compounds. The main postulates are:
(4) in NCERT text
A
- In coordination compounds metals show two types of linkages (valences)-primary and secondary.
- The primary valences are normally ionisable and are satisfied by negative ions.
- The secondary valences are non ionisable. These are satisfied by neutral molecules or negative ions. The secondary valence is equal to the coordination number and is fixed for a metal.
- The ions/groups bound by the secondary linkages to the metal have characteristic spatial arrangements corresponding to different coordination numbers.
15
Q
Werner further postulated that…../…../…… geometrical shapes are more common in coordination compounds of transition metals.
A
Octahedral
Tetrahedral
Square planar
16
Q
Some Cobalt(III) Chloride-Ammonia Complexes
A
CoCl3_5NH3. [CoCl(NH3)5]+2_2Cl- Purple
CoCl3_4NH3. [CoCl2(NH3)4]+2_Cl- Green
CoCl3_4NH3. [CoCl2(NH3)4]+2_Cl- Violet
[Co(NH3)6]+3_3Cl- Yellow
17
Q
Carnallite
A
KCl.MgCl2.6H2O
18
Q
Mohr’s salt
A
FeSO4.(NH4)2SO4.6H2O
19
Q
Potash alum
A
KAl(SO4)2_12H2O
20
Q
A…………… constitutes a central metal atom or ion bonded to a fixed number of ions or molecules
A
coordination entity
21
Q
In a coordination entity, the atom/ion to which a fixed number of ions/groups are bound in a definite geometrical arrangement around it, is called the…….
A
central atom or ion
22
Q
The ions or molecules bound to the central atom/ion in the coordination entity are called…….
A
ligands
23
Q
The………. of a metal ion in a complex can be defined as the number of ligand donor atoms to which the metal is directly bonded
A
coordination number (CN)
24
Q
The coordination number of the central atom/ion is determined only by the number of…….. bonds formed by the ligand with the central atom/ion.
………… bonds, if formed between the ligand and the central atom/ion, are not counted for this purpose.
A
sigma
Pie
25
The central atom/ion and the ligands attached to it are enclosed in square bracket and is collectively termed as the……….
coordination sphere
26
The spatial arrangement of the ligand atoms which are directly attached to the central atom/ion defines a………… about the central atom
coordination polyhedron
27
While writing formulas …………. is listed first
central atom is listed first.
28
Statement 1: The ligands are then listed in alphabetical order.
Statement 2: The placement of a ligand in the list depend on its charge.
One is true two is false
The placement of a ligand in the list does not depend on its charge.
29
In case of abbreviated ligand, the first letter of the………. is used to determine the position of the ligand in the alphabetical order.
abbreviation
30
Statement 1: The formula for the entire coordination entity, whether charged or not, is enclosed in square brackets
Statement 2: When ligands are polyatomic, their formulas are enclosed in parentheses. Ligand abbreviations are also enclosed in parentheses.
Both are correct
31
Statement 1: There should be some space between the ligands and the metal within a coordination sphere.
Statement 2: When the formula of a charged coordination entity is to be written without that of the counter ion, the charge is indicated outside the square brackets as a right superscript with the number before the sign. For example, [Co(CN)6]3–, [Cr(H2O)6]3+
1 is incorrect
There should be NO space between the ligands and the metal within a coordination sphere
32
The 2004 IUPAC draft recommends that ligands will be sorted alphabetically, irrespective of……..
charge
33
The magnetic moment of coordination compounds can be measured by the………. experiments
magnetic susceptibility
34
The Valance Bond theory, to a larger extent, explains the …../…../…..of coordination compounds
Formation
Structures
Magnetic behaviour
35
Limitations of VBT
(6) in NCERT
(i) It involves a number of assumptions.
(ii) It does not give quantitative interpretation of magnetic data.
(iii) It does not explain the colour exhibited by coordination compounds.
(iv) It does not give a quantitative interpretation of the thermodynamic or kinetic stabilities of coordination compounds.
(v) It does not make exact predictions regarding the tetrahedral and square planar structures of 4-coordinate complexes.
(vi) It does not distinguish between weak and strong ligands.
36
Statement 1: The crystal field theory (CFT) is an electrostatic model which considers the metal-ligand bond to be ionic arising purely from electrostatic interactions between the metal ion and the ligand.
Statement 2: Ligands are treated as point charges in case of anions or point dipoles in case of neutral molecules.
Both are correct statements
37
Statement 1: The five d orbitals in an isolated gaseous metal atom/ion have same energy, i.e., they are degenerate.
Statement 2: This degeneracy is maintained if a spherically symmetrical field of negative charges surrounds the metal atom/ion.
Both are correct
38
Statement 1: The negative field is due to ligands (either anions or the negative ends of dipolar molecules like NH3 and H2O) in a complex is asymmetrical and causes the degeneracy of the d orbitals to be lifted
Statement 2: It results in splitting of the d orbitals.
Both are correct
39
In an octahedral coordination entity with six ligands surrounding the metal atom/ion, there will be repulsion between the electrons in metal d orbitals and the electrons (or negative charges) of the ligands
True
40
The repulsion is more when the metal d orbital is directed away from the ligand than when it is towards the ligand.
False
The repulsion is more when the metal d orbital is directed towards the ligand than when it is away from the ligand.
41
Statement 1: The dx2-y2 and dz2 orbitals which point towards the axes along the direction of the ligand will experience more repulsion and will be raised in energy
Statement 2: The dxy, dyz and dxz orbitals which are directed between the axes will be lowered in energy relative to the average energy in the spherical crystal field.
Both are correct
Explained by "repulsion is more when the metal d orbital is directed towards the ligand than when it is away from the ligand"
42
This splitting of the degenerate levels due to the presence of ligands in a definite geometry is termed as……….and the energy separation is denoted by ∆o
crystal field splitting
43
Assertion: In tetrahedral coordination entities low spin configurations are rarely observed.
Reason: In tetrahedral CFS orbital splitting energies are not sufficiently large for forcing pairing and, therefore,
Both are correct and correct explanation
44
Assertion: The tetrahedral energy levels there is no use of ‘g’ subscript
Reason: The tetrahedral complexes lack symmetry
Both are correct and correct explanation
45
Ruby is aluminium oxide (Al2O3) containing about 0.5-1%………ions (d3), which are randomly distributed in positions normally occupied by Al3+
Cr3+
46
In emerald Cr3+ ions occupy octahedral sites in the mineral beryl …………… The absorption bands seen in the ruby shift to longer wavelength, namely yellow-red and blue, causing emerald to transmit light in the green region.
Be3Al2Si6O18
47
The crystal field model is successful in explaining the …../…../…../…..of
coordination compounds to a large extent
Formation
Structures
Colour
Magnetic properties
48
Statement 1: As per CFT from the assumptions that the ligands are point charges, it follows that anionic ligands should exert the greatest splitting effect.
Statement 2: The anionic ligands actually are found at the low end of the spectrochemical series.
Both are correct
49
CFT doesn’t take into account………… character of bonding between the ligand and the central atom
covalent
50
Some of the weaknesses of CFT are explained by……../…….
ligand field theory (LFT) and molecular orbital theory
51
The familiar colour reactions given by metal ions with a number of ligands (especially chelating ligands), as a result of the formation of coordination entities, form the basis for their detection and estimation by classical and instrumental methods of analysis
True
Examples of such reagents include EDTA, DMG (dimethylglyoxime), α–nitroso–β–naphthol, coupon
52
Aqueous copper sulphate solution (blue in colour) gives:
(i) a green precipitate with aqueous potassium fluoride
(ii) a bright green solution with aqueous potassium chloride.
Explain these experimental results.
Aqueous copper sulphate solution is blue due to the formation of [Cu(H2O)4]SO4
[Cu(H2O)4]SO4(aq) ⇌ [Cu(H2O)4]2+ + SO2−4
Cu(H2O)4]2+ is a labile complex in which ligands H2O get easily replaced by F− ion of KF and by Cl− ion of KCl
[Cu(H2O)4]2+(aq) +4F−(aq)→[CuF4]2− Green ppt. + 4H2O
[Cu(H2O)4]2+(aq) +4Cl−(aq)→[CuCl4]2−(aq) (Bright green solution) + 4H2O
53
What is the coordination entity formed when excess of aqueous KCN is added to an aqueous solution of copper sulphate?
Why is it that no precipitate of copper sulphide is obtained when H2S(g) is passed through this solution?
K2[Cu(CN)4]
CuSO4(aq) + 4KCN(aq) → K2[Cu(CN)4](aq) + K2SO4
i.e. [Cu(H2O)4]2+ + 4CN- → [Cu(CN)4]2- + 4H2O
K2[Cu(CN)4] is a very stable complex that does not ionize to give Cu2+ ions when added to water. Hence Cu2+ ions are not precipitated when H2S(g) is passed through the solution.
54
Assertion: [Fe(CN)6]4– and [Fe(H2O)6]2+ are of different colours in dilute solutions.
Reason: There is difference in CFSE (crystal field splitting energy)
Both are correct and correct explanation
CN- is a strong field ligand having a higher CFSE value as compared to the CFSE value of water. This means that the absorption of energy for the intra d-d transition also differs. Hence, the transmitted colour also differs.
55
What is meant by the chelate effect
When a ligand attaches to the metal ion in a manner that forms a ring, then the metal ligand association is found to be more stable. In other words, we can say that complexes containing chelate rings are more stable than complexes without rings. This is known as the chelate effect.
56
Amongst the following, the most stable complex is
(i) [Fe(H2O)6]3+ (ii) [Fe(NH3)6]3+
(iii) [Fe(C2O4)3]3– (iv) [FeCl6]3–
[Fe(C2O4)3]3–
The complex which contains chelating ligands are more stable than nonchelated compounds of comparable composition.
In each of the given complexes, Fe is in a +3 oxidation state. As C2O42− is a bidentate chelating ligand, it forms rings and hence
[Fe(C2O4)3]3− is the most stable complex.
57
What will be the correct order for the wavelengths of absorption in the visible region for the following:
[Ni(NO2)6]4–, [Ni(NH3)6]2+, [Ni(H2O)6]2+
Wavelengths of absorption in the visible region depend on the metal oxidation state and ligand. If metal is the same in the given complexes then wavelengths of absorption totally depend on the strength of the ligand.
The wavelength is inversely proportional to energy, here energy is CFSE values.
Stronger the ligand higher is the CFSE thus higher is energy and since wavelength is inversely proportional to energy lesser is the wavelength
[Ni(H2O)6]2+ > [Ni(NH3)6]2+ > [Ni(NO2)6]4-
58
Strength rules MDJ
Oxygen donor ligand will act as STRONG Field Ligand with Co+3 ion
In 4d and 5d series metals or elements generally all ligands will act as STRONG Field Ligand
Metal ion with +4 OS (M+4) generally all ligands act as STRONG Field Ligand
Ammonia (NH3) with Cr+2 Mn+2 Fe+2 Co+2 acts as a WEAK Field Ligand
59
In presence of a strong ligand one electron from inner d orbital can be transferred to outer d orbital if required.
In case example configuration is d7 and on pairing only one electron can be paired and only one orbital becomes free so to get two free inner d orbitals we transfer that one unpaired electron to outer d orbital
As in [Co(CN)6]-2 required two orbitals one electron paired and one electron transferred
[Cu(NH3)4]SO4 one inner orbital required and thus that one electron transferred to outer orbital
60
Assertion: In tetrahedral CFT we do not pairing until all the orbitals t2 and e are singly occupied
Reason: The pairing energy is always greater than the CFSE
Both are correct and correct explanation
61
Statement 1: Because of STRONG FIELD LIGAND the CFSE becomes greater than pairing energy thus it is always feasible to pair electrons in lower orbitals (t2g) first filled completely and then higher start filling
Statement 2: In case of WEAK FIELD LIGANDS the CFSE is not greater than the pairing energy thus it’s feasible to first filled lower orbitals singly and then without pairing next electron goes into higher orbital.
Both statement are correct
SFL: t2g —>t2g —> eg —> eg
WFL: t2g —> eg —> t2g —>eg
62
KMnO4 and K2Cr2O7 are coloured due to
LMCT Ligand to Metal Charge Transfer
63
Metal to Metal Ligand Transfer is responsible for colour in:
Fe4[Fe(CN)6]3 Prussian blue
Hg2I2. Scarlet Red
64
Number of linkage isomers possible is equivalent to
2^n where n is the total number of ambidentate ligands
65
In case of coordination isomers the number of coordination isomers possible
For both central ion and the ligands are different= n
For the central atom to be same but the ligands different= n/2
Where n stands for the no. of ligands
66
In case of coordination number 4
For tetrahedral geometry optical isomers seen but no geometrical isomers
For square planer geometry geometrical isomers are seen but no optical isomers
67
dsp2 hybridisation gives geometry……….. with ………. d orbital used
Square planer
dx2–y2
68
For dsp3 or sp3d hybridisation the geometry is……….. and orbital used is……..
Trigonal bipyrimidal
dz2
69
d2sp3 and sp3d2 show………….. geometry and d orbitals used are
Octahedral
dz2 and dx2–y2
70
Donation strength of donor atoms
C > N > O > X
71
Fkexidentate ligands
SO4*-2
EDTA
CO3*-2
72
Stretching vibrational frequency (U*) of CO is directly proportional to………… and inversely proportional to……../……
Bond strength of CO
Bond strength of MC or extent of synergic bonding
Synergic bonding (inc) CO bond strength (dec) U* (dec)
73
Why C-C bond length Is more in Zeise salt
The ligand is C2H4 (alkene)
It donates its pie bond so BL(inc) as Bond order (dec)
Also it accepts the electron pair in its ANTIBONDING orbital
74
If PF3 a better pi acceptor is present with CO then more preference is given to ………. and thus extent of synergic bonding in …….. is reduced
PF3 being better acceptor
CO is reduced thus increase in bond length of CO is less in presence of PF3
Also P(CH3)3 is week acceptor than PF3 (with respect to Inductive effect)
75
NO acts as…… e- donor while NO+ acts as …… e- donor
3
2
76
During synergic bonding the increase in bond length of CO is
2 to 5% not very high or drastic
77
Brown ring complex
[Fe(H2O)5NO]SO4
Pentaaquanitrosonium ferrate(I) sulphate
78
Sodium pentacyanidonitrosyl ferrate (II) or Sodium nitro pruside is used in test for
Sulphide S-2 ion
Na2[Fe(CN)5NO] ()with sulphide ion gives purple colour as Na4[Fe(CN)5NOS] formed
79
Zeise salt
K[PtCl3(C2H4)]
Potassium trichlorido (n*2-ethylene) platinate (II)
80
Wilkinsons catalyst used in hydrogenation of alkenes
[RhCl(pph3)3]
Chloride tris-triphenyl phosphine rhodium (I)
81
Assertion: If electrons are present in ns subshell they can be transferred to (n-1)d subshell before mixing
Reason: Hybridisation may take place without P or d but strictly requires s for angular character
Both are correct and correct explanation
This is observed in two complexes
Ni(CO)4
Fe(CO)5
82
Stability of compound as per CFSE can be determined by what factors
Stability is high
Chelation occurs (more number of rings more is stability)
High splitting energy (square planer > octahedral > tetrahedral)
Strong field ligands
Oxidation state of central atom be high
High Zeff of central ion or atoms ( down group Z inc so for 4d and 5d series almost all ligands work as strong field ligands)
83
Frankland reagent
R2Zn
84
According to Sedgwick theory of effective atomic number the elements tend to achieve Nobel gas configuration
Formula for EAN IS
EAN= Atomic no. — Oxidation no. + (2 x Coordination no.)
85
The following rules are used when naming coordination compounds:
(i) The cation is named first in both positively and negatively charged coordination entities.
(ii) The ligands are named in an alphabetical order before the name of the central atom/ion. (This procedure is reversed from writing formula).
(iii) Prefixes mono, di, tri, etc., are used to indicate the number of the individual ligands in the coordination entity. When the names of the ligands include a numerical prefix, then the terms, bis, tris, tetrakis are used, the ligand to which they refer being placed in parentheses. For example, [NiCl2(PPh3)2] is named as dichloridobis(triphenylphosphine)nickel(II).
(iv ) Oxidation state of the metal in cation, anion or neutral coordination entity is indicated by Roman numeral in parenthesis.
(v) If the complex ion is a cation or neutral the metal is named same as the element. If the complex ion is an anion, the name of the metal ends with the suffix – ate
