1. Home
  2. Ut austin - principles of
  3. Inorganic
  4. Coordination chemistry of

13.2 Coordination chemistry of transition metals  (Page 4/25)

<< Chapter < Page
  Ut austin - principles of     Page 4 / 25
Chapter >> Page >

Coordination numbers and oxidation states

Determine the name of the following complexes and give the coordination number of the central metal atom.

(a) Na 2 [PtCl 6 ]

(b) K 3 [Fe(C 2 O 4 ) 3 ]

(c) [Co(NH 3 ) 5 Cl]Cl 2

Solution

(a) There are two Na + ions, so the coordination sphere has a negative two charge: [PtCl 6 ] 2− . There are six anionic chloride ligands, so −2 = −6 + x , and the oxidation state of the platinum is 4+. The name of the complex is sodium hexachloroplatinate(IV), and the coordination number is six. (b) The coordination sphere has a charge of 3− (based on the potassium) and the oxalate ligands each have a charge of 2−, so the metal oxidation state is given by −3 = −6 + x , and this is an iron(III) complex. The name is potassium trisoxalatoferrate(III) (note that tris is used instead of tri because the ligand name starts with a vowel). Because oxalate is a bidentate ligand, this complex has a coordination number of six. (c) In this example, the coordination sphere has a cationic charge of 2+. The NH 3 ligand is neutral, but the chloro ligand has a charge of 1−. The oxidation state is found by +2 = −1 + x and is 3+, so the complex is pentaaminechlorocobalt(III) chloride and the coordination number is six.

Check your learning

The complex potassium dicyanoargenate(I) is used to make antiseptic compounds. Give the formula and coordination number.

Answer:

K[Ag(CN) 2 ]; coordination number two

Got questions? Get instant answers now!

The structures of complexes

The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar (see [link] ). For transition metal complexes, the coordination number determines the geometry around the central metal ion. [link] compares coordination numbers to the molecular geometry:

This figure contains three diagrams in black and white. The first is labeled, “Pentagonal Bipyramid.” It has 10 isosceles triangle faces, five at the top, joined at a vertex, making a point projecting upward at the top of the figure, and five below, joined at a vertex, making a point projecting downward, at the base of the figure. The second is labeled, “Square Antiprism.” It has flat upper and lower square surfaces and sides made up of 8 equilateral triangles. The sides alternate in orientation between pointing up and pointing down. The third diagram is labeled, “Dodecahedron.” It has twelve isosceles triangle faces.
These are geometries of some complexes with coordination numbers of seven and eight.
Coordination Numbers and Molecular Geometry
Coordination Number Molecular Geometry Example
2 linear [Ag(NH 3 ) 2 ] +
3 trigonal planar [Cu(CN) 3 ] 2−
4 tetrahedral( d 0 or d 10 ), low oxidation states for M [Ni(CO) 4 ]
4 square planar ( d 8 ) [NiCl 4 ] 2−
5 trigonal bipyramidal [CoCl 5 ] 2−
5 square pyramidal [VO(CN) 4 ] 2−
6 octahedral [CoCl 6 ] 3−
7 pentagonal bipyramid [ZrF 7 ] 3−
8 square antiprism [ReF 8 ] 2−
8 dodecahedron [Mo(CN) 8 ] 4−
9 and above more complicated structures [ReH 9 ] 2−

Unlike main group atoms in which both the bonding and nonbonding electrons determine the molecular shape, the nonbonding d -electrons do not change the arrangement of the ligands. Octahedral complexes have a coordination number of six, and the six donor atoms are arranged at the corners of an octahedron around the central metal ion. Examples are shown in [link] . The chloride and nitrate anions in [Co(H 2 O) 6 ]Cl 2 and [Cr(en) 3 ](NO 3 ) 3 , and the potassium cations in K 2 [PtCl 6 ], are outside the brackets and are not bonded to the metal ion.

Three structures are shown. In a, a structure is shown with a central C o atom. From the C o atom, line segments indicate bonds to H subscript 2 O molecules above and below the structure. Above and to both the right and left, dashed wedges indicate bonds to two H subscript 2 O molecules. Similarly, solid wedges below to both the right and left indicate bonds to two more H subscript 2 O molecules. Each bond in this structure is directed toward the O atom in each H subscript 2 O structure. This structure is enclosed in brackets. Outside the brackets to the right is the superscript 2 plus. Following this to the right appears 2 C l superscript negative sign. In b, a central C r atom has six N H subscript 2 groups attached with single bonds. These bonds are indicated with line segments extending above and below, dashed wedges extending up and to the left and right, and solid wedges extending below and to the left and right. The bonds to these groups are all directed toward the N atoms. The N H subscript 2 groups are each connected to C atoms of C H subscript 2 groups extending outward from the central C o atom. These C H subscript 2 groups are connected in pairs with bonds indicated by short line segments. This entire structure is enclosed in brackets. Outside the brackets to the right is the superscript 3 plus. Following to the right is 3 N O subscript 3 superscript negative sign. In c, 2 K superscript plus is followed by a structure in brackets. Inside the brackets is a central P t atom. From the P t atom, line segments indicate bonds to C l atoms above and below the structure. Above and to both the right and left, dashed wedges indicate bonds to C l atoms. Similarly, solid wedges below to both the right and left indicate bonds to two more C l atoms. This structure is enclosed in brackets. Outside the brackets to the right is the superscript 2 negative sign.
Many transition metal complexes adopt octahedral geometries, with six donor atoms forming bond angles of 90° about the central atom with adjacent ligands. Note that only ligands within the coordination sphere affect the geometry around the metal center.

For transition metals with a coordination number of four, two different geometries are possible: tetrahedral or square planar. Unlike main group elements, where these geometries can be predicted from VSEPR theory, a more detailed discussion of transition metal orbitals (discussed in the section on Crystal Field Theory) is required to predict which complexes will be tetrahedral and which will be square planar. In tetrahedral complexes such as [Zn(CN) 4 ] 2− ( [link] ), each of the ligand pairs forms an angle of 109.5°. In square planar complexes, such as [Pt(NH 3 ) 2 Cl 2 ], each ligand has two other ligands at 90° angles (called the cis positions) and one additional ligand at an 180° angle, in the trans position.

Questions & Answers

what is defense mechanism
Chinaza Reply
what is defense mechanisms
Chinaza
I'm interested in biological psychology and cognitive psychology
Tanya Reply
what does preconceived mean
sammie Reply
physiological Psychology
Nwosu Reply
How can I develope my cognitive domain
Amanyire Reply
why is communication effective
Dakolo Reply
Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.
it starts up serve and return practice/assessments.it helps find voice talking therapy also assessments through relaxed conversation.
miss
Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
Wekolamo Reply
please i need answer
Wekolamo
because it helps many people around the world to understand how to interact with other people and understand them well, for example at work (job).
Manix Reply
Agreed 👍 There are many parts of our brains and behaviors, we really need to get to know. Blessings for everyone and happy Sunday!
ARC
A child is a member of community not society elucidate ?
JESSY Reply
Isn't practices worldwide, be it psychology, be it science. isn't much just a false belief of control over something the mind cannot truly comprehend?
Simon Reply
compare and contrast skinner's perspective on personality development on freud
namakula Reply
Skinner skipped the whole unconscious phenomenon and rather emphasized on classical conditioning
war
explain how nature and nurture affect the development and later the productivity of an individual.
Amesalu Reply
nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.
Samuel
I am taking this course because I am hoping that I could somehow learn more about my chosen field of interest and due to the fact that being a PsyD really ignites my passion as an individual the more I hope to learn about developing and literally explore the complexity of my critical thinking skills
Zyryn Reply
good👍
Jonathan
and having a good philosophy of the world is like a sandwich and a peanut butter 👍
Jonathan
generally amnesi how long yrs memory loss
Kelu Reply
interpersonal relationships
Abdulfatai Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
<< Chapter < Page Page > Chapter >>
Practice Key Terms 16

Read also:

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Ut austin - principles of chemistry. OpenStax CNX. Mar 31, 2016 Download for free at http://legacy.cnx.org/content/col11830/1.13
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Ut austin - principles of chemistry' conversation and receive update notifications?

Ask