5.111 Lecture #27 Monday, November 17, 2014
Reading For Today: 16.5-16.7 in 5th and 4th editions
Reading for lecture#28: 16.8-16.11 in 4th and 5th editions
Topic: I. d-Block Metals or Transition Metals
II. Coordination Complexes (Chelate effect, Shapes, Isomers)
III. d-orbital Counting and d-orbitals
I. d-Block Metals or Transition Metals
Elements in groups 3-12 are d-block metal s, often referred to as metals.
d-block metals or transition metals
Periodic Table of the Elements, by DePiep 2013. Wikimedia Commons.
d-block metals naturally occurring in biology – V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, W.
d-block metals used as probes of biological systems and/or pharmaceuticals include: Cr,
Co, Y, Tc, Ag, Cd, Pt, Au, Hg.
Roles of metals in biology include:
global cycling of nitrogen, carbon, hydrogen; biosynthesis of vitamins and
deoxynucleotides; respiration; photosynthesis etc
IN THEIR OWN WORDS
Dr. Sarah Bowman studies a protein from a pathogenic bacterium
that is found in the stomach and is known to cause ulcers. She
explains how the bacterium survives in the low pH environment of
the stomach by using nickel-dependent proteins to buffer the acidity
of its environment.
Image from "Behind the Scenes at MIT”. The
Drennan Education Laboratory. Licensed under
a Creative Commons Attribution-NonCommercial
-ShareAlike License.
1
, II. Coordination Complexes
A key feature of transition metals is their ability to form complexes with small molecules
and ions.
Positive metals ions can attract electron density, usually a lone pair of electrons from
another atom or molecule to form a coordination complex.
Donor atoms are called l igands (Lewis –typically _______________ one l one pair
of electrons)
Examples of ligands: NO2- OCO2-2 CN- SCN- NCS-
2e- 2e- 2e- 2e- 2e-
OH- OH2 NH3 CO NO+
2e- 2e- 2e- 2e- 2e-
Acceptor atoms are transition metal s (Lewis _________– _________________ one lone pair
of electrons)
Examples of transition metals: Ti, Cr, Mn, Fe, Co, Ir, Pt, etc
Coordination complexes are composed of metals that are surrounded by ligands.
Example:
NH3 3+
H3N NH3
Co
H3N
NH3
NH3
Coordination number (CN) is the number of ligands bonded to the metal ion.
Here CN = 6. ligands comprise the primary coordination sphere.
CN numbers typically range from 2-12. Six is the most common.
Coordination Complex Notation
[Co(NH3)6]+3 3Cl-1
↓
[Co(NH3)6]Cl3
NH3 within bracket is bound to Co; Cl outside bracket is a counter ion.
2
Reading For Today: 16.5-16.7 in 5th and 4th editions
Reading for lecture#28: 16.8-16.11 in 4th and 5th editions
Topic: I. d-Block Metals or Transition Metals
II. Coordination Complexes (Chelate effect, Shapes, Isomers)
III. d-orbital Counting and d-orbitals
I. d-Block Metals or Transition Metals
Elements in groups 3-12 are d-block metal s, often referred to as metals.
d-block metals or transition metals
Periodic Table of the Elements, by DePiep 2013. Wikimedia Commons.
d-block metals naturally occurring in biology – V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, W.
d-block metals used as probes of biological systems and/or pharmaceuticals include: Cr,
Co, Y, Tc, Ag, Cd, Pt, Au, Hg.
Roles of metals in biology include:
global cycling of nitrogen, carbon, hydrogen; biosynthesis of vitamins and
deoxynucleotides; respiration; photosynthesis etc
IN THEIR OWN WORDS
Dr. Sarah Bowman studies a protein from a pathogenic bacterium
that is found in the stomach and is known to cause ulcers. She
explains how the bacterium survives in the low pH environment of
the stomach by using nickel-dependent proteins to buffer the acidity
of its environment.
Image from "Behind the Scenes at MIT”. The
Drennan Education Laboratory. Licensed under
a Creative Commons Attribution-NonCommercial
-ShareAlike License.
1
, II. Coordination Complexes
A key feature of transition metals is their ability to form complexes with small molecules
and ions.
Positive metals ions can attract electron density, usually a lone pair of electrons from
another atom or molecule to form a coordination complex.
Donor atoms are called l igands (Lewis –typically _______________ one l one pair
of electrons)
Examples of ligands: NO2- OCO2-2 CN- SCN- NCS-
2e- 2e- 2e- 2e- 2e-
OH- OH2 NH3 CO NO+
2e- 2e- 2e- 2e- 2e-
Acceptor atoms are transition metal s (Lewis _________– _________________ one lone pair
of electrons)
Examples of transition metals: Ti, Cr, Mn, Fe, Co, Ir, Pt, etc
Coordination complexes are composed of metals that are surrounded by ligands.
Example:
NH3 3+
H3N NH3
Co
H3N
NH3
NH3
Coordination number (CN) is the number of ligands bonded to the metal ion.
Here CN = 6. ligands comprise the primary coordination sphere.
CN numbers typically range from 2-12. Six is the most common.
Coordination Complex Notation
[Co(NH3)6]+3 3Cl-1
↓
[Co(NH3)6]Cl3
NH3 within bracket is bound to Co; Cl outside bracket is a counter ion.
2
