   Chapter 21, Problem 3RQ

Chapter
Section
Textbook Problem

# When a metal ion has a coordination number of 2, 4, or 6, what are the observed geometries and associated bond angles? For each of the following, give the correct formulas for the complex ions.a. linear Ag+ complex ions having CN− ligandsb. tetrahedral Cu+ complex ions having H2O ligandsc. tetrahedral Mn2+ complex ions having oxalate ligandsd. square planar Pt2+ complex ions having NH3 ligandse. octahedral Fe3+ complex ions having EDTA ligandsf. octahedral Co2+ complex ions having Cl− ligandsg. octahedral Cr3+ complex ions having ethylene-diamine ligandsWhat is the electron configuration for the metal ion in each of the complex ions in a−g?

Interpretation Introduction

Interpretation: The geometries and bond angle for the metal ion having coordination number 2 , 4 or 6 ; the correct formulas for given complex ions and their electronic configuration are to be stated.

Concept introduction: Coordination number is the number of nearest neighbors of the given metal ion. The geometry of a coordination complex depends on the number of ligands that are surrounding a metal ion.

Explanation

(I)

To determine: The geometry and associated bond angles when a metal ion has a coordination number of 2 , 4 or 6 .

When a metal ion has a coordination number of 2 , it means it is linear in geometry and has a bond angle of 180°. But, when the metal ion has coordination number of 4 it means it is surrounded by four neighbors and therefore the geometry is tetrahedral and the angle is 109.5° or it can be square planar where the bond angle is 90°. When a metal ion has a coordination number of 6 , it means it is surrounded by six neighbours and has geometry as octahedral and bond angle equal to 90°.

(II)

(a)

To determine: The correct formula for the linear Ag+ complex having CN ligands.

Linear geometry shows that Ag+ is surrounded by two ligands and therefore it has a coordination number of 2 . The formula of the complex is [Ag(CN)2] and bond angle is 180°.

(b)

To determine: The correct formula for tetrahedral Cu+ complex having H2O ligands.

Tetrahedral geometry shows that Cu+ is surrounded by four ligands and therefore it has a coordination number of 4. The formula of the complex is [Cu(H2O)4]+ and bond angle is 109.5°.

(c)

To determine: The correct formula for tetrahedral Mn2+ complex having Oxalate ligands.

Tetrahedral geometry shows that Mn2+ is surrounded by four ligands and therefore it has a coordination number of 4. The formula of the complex is [Mn(C2O4)2]2 and bond angle is 90°.

(d)

To determine: The correct formula for square planar Pt2+ complex having NH3 ligands.

Square planar geometry shows that Pt2+ is surrounded by four ligands and therefore it has a coordination number of 4. The formula of the complex is [Pt(NH3)4]2+ and bond angle is 90°.

(e)

To determine: The correct formula for octahedral Fe3+ complex ions having EDTA ligands.

An octahedral geometry shows that Fe3+ is surrounded by six ligands and therefore it has a coordination number of 6 . The formula of the complex is [Fe(EDTA)] and bond angle is 90°.

(f)

To determine: The correct formula for octahedral Co2+ complex ions having Cl ligands.

An octahedral geometry shows that Co2+ is surrounded by six ligands and therefore it has a coordination number of 6 . The formula of the complex is [CoCl6]2+ and bond angle is 90°.

(g)

To determine: The correct formula for octahedral Cr3+ complex ions having ethylene-diamine ligands.

Step: 7

An octahedral geometry shows that Cr3+ is surrounded by six ligands and therefore it has a coordination number of 6 . The formula of the complex is [Cr(en)3]3+ and bond angle is 90°

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