<< Chapter < Page Chapter >> Page >

Transitions metals: synthesis of an inorganic compound (trans-dinitrobis(ethylenediamine)cobalt(iii) nitrate)



  • To synthesize a transition metal complex of cobalt three, Co(III), and ethylenediamine.
  • To characterize the resulting metal complex spectroscopically.
  • To understand concept of limiting reactant.


Your will be determined according to the following:

  • prelab (10%)
  • lab report form (80%)
  • TA points (10%)


The transition metals are the largest“group”(classification) of elements from the periodic table. These can be found in nature as ores or in its elemental form, such as gold. All transition metals have more than one oxidation state. Most transition metals (TMs) can complex with other species (called ligands in“TM Complex”jargon) by giving their electrons to them, forming a complex. These ligands, which are the nearest neighbor atoms to the metal center, constitute the inner (or first) coordination sphere. Complexes may be either neutral or charged and have distinctive properties that may be quite unlike those associated with their constituent molecules and ions, each of which is capable of independent existence. An example of a charged complex is ferricyanide, [ Fe ( CN ) 6 ] 3 size 12{ \[ ital "Fe" \( ital "CN" \) rSub { size 8{6} } \] rSup { size 8{ - 3} } } {} . The Fe + 3 size 12{ ital "Fe" rSup { size 8{+3} } } {} and CN size 12{ ital "CN" rSup { size 8{ - {}} } } {} ions found in the ferricyanide complex ion exist as independent species and in other compounds. The transition metals are well known for forming a large number of complex ions. In this experiment we will synthesize a transition metal complex containing cobalt, Co(III), and ethylenediamine.


The most common coordination numbers (the number of individual ligands bound) are two, four, and six, with geometries illustrated in Fig 1:

Fig 1. Common geometries for complex ions. (A) linear, (B) square planar, (C) tetrahedral, and (D) octahedral


Complexes of Cu(I), Ag(I), Au(I) and some of Hg(II) form linear structures (A) such as Cu ( CN ) 2 size 12{ ital "Cu" \( ital "CN" \) rSub { size 8{2} } rSup { size 8{ - {}} } } {} , Ag ( NH 3 ) 2 + size 12{ ital "Ag" \( ital "NH" rSub { size 8{3} } \) rSub { size 8{2} } rSup { size 8{+{}} } } {} , etc. Four-fold coordination (C) is not too common with transition metals, and the square planar geometry (B) occurs in complexes of Pd(II), Pt(II), Ni(II), Cu(II), and Au(III). Six-fold coordination (D) is the most common and in fact the one we will study in this laboratory exercise.

A ligand that is capable of occupying only one position in the inner coordination sphere by forming only one bond to the central atom is called a monodentate (“one tooth”) ligand. Examples are F size 12{F rSup { size 8{ - {}} } } {} , Cl size 12{ ital "Cl" rSup { size 8{ - {}} } } {} , OH size 12{ ital "OH" rSup { size 8{ - {}} } } {} , H 2 O size 12{H rSub { size 8{2} } O} {} , NH 3 size 12{ ital "NH" rSub { size 8{3} } } {} and CN size 12{ ital "CN" rSup { size 8{ - {}} } } {} . If the ligand has two groups that are capable of bonding to the central atom, it is called a bidentate ("two teeth") ligand, and so forth. An example of a bidentate ligand is ethylenediamine ( CH 2 NH 2 CH 2 NH 2 ) size 12{ \( ital "CH" rSub { size 8{2} } ital "NH" rSub { size 8{2} } ital "CH" rSub { size 8{2} } ital "NH" rSub { size 8{2} } \) } {} , which is commonly abbreviated "en". Both nitrogen atoms in "en" can bond to the central atom in a complex at the same time.

Complex ion salts with the same chemical formulas often behave differently because the same number of atoms can be arranged into different forms called isomers. Hydrate isomerism is illustrated by the following example: There are three distinct compounds with the formula Cr ( H 2 O ) 6 Cl 3 size 12{ ital "Cr" \( H rSub { size 8{2} } O \) rSub { size 8{6} } ital "Cl" rSub { size 8{3} } } {} . One of these, violet in color, reacts immediately with AgNO 3 size 12{ ital "AgNO" rSub { size 8{3} } } {} to precipitate all of the chlorines as AgCl. The second is light green but only⅔of the chlorine is precipitated as AgCl. The third compound is dark green and only⅓of the chlorine is precipitated as AgCl. The last compound has only one reactive Cl, so apparently two chlorines in this compound are bonded tightly to the Cr and are not available for reaction. We might thus write this compound as [ CrCl 2 ( H 2 O ) 4 ] ( H 2 O ) 2 size 12{ \[ ital "CrCl" rSub { size 8{2} } \( H rSub { size 8{2} } O \) rSub { size 8{4} } \] cdot \( H rSub { size 8{2} } O \) rSub { size 8{2} } } {} , where the species within the brackets are regarded as ligands bonded fairly strongly to the central chromium, and this species would behave as a single ion in solution. i.e., in aqueous solution,

Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Honors chemistry lab fall. OpenStax CNX. Nov 15, 2007 Download for free at http://cnx.org/content/col10456/1.16
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Honors chemistry lab fall' conversation and receive update notifications?