3.2.5 Transition Metals Flashcards
What is a transition metal?
forms one or more stable ions which have partially filled d subshell
Why is Zn not a transition metal?
Zn only forms a Zn2+ ion that has a complete d subshell and so does not meet the criteria of a partially filled d subshell.
Why is Sc not a transition metal?
Sc most stable ion is Sc3+, which has an empty d subshell and therefore is not a transition metal
What are the properties of transition metals?
. Variable oxidation states
. Form complex ions
. Form coloured compounds
. Behave as catalyst
Why do transition metals show variable oxidation numbers in compounds?
the energy to remove electrons from the 4s and 3d orbitals is very similar; hence multiple electrons can be removed
(we use roman numerals to indicate different oxidation states)
What is a complex?
metal atom or ion surrounded by ligands
What is a ligand?
an atom, ion or molecule which can donate a lone electron pair that bonds to metals by a coordinate bond
What is a coordination number?
the number of coordinate bonds (dative covalent) formed by a central metal ion.
What type of catalyst can transition metals act as?
Heterogeneous catalyst - different phase from reactants
Homogeneous catalyst - same phase as reactants
Why can transition metals catalyse reactions?
Most transition metals have multiple stable oxidation states
NCS PP TM L1 Catalysis slide 9 - rest not complete
What is a monodentate ligand?
can form only one dative bond to the central metal ion
Examples of monodentate ligands:
Water H2O
Ammonia NH3
Chloride Cl-
Cyanide CN-
OH-
What is a bidentate ligand?
can donate 2 pairs of lone pairs of electrons and can each form 2 dative bonds to the central metal ion
Examples of bidentate ligands:
. en H2NCH2CH2NH2 (1,2-diaminoethane)
. ox C2O42- (ethanedioate)
What is a multidentate ligand?
can form more than two dative bonds
Examples of multidentate:
EDTA4- hexadentate
How to work out oxidation state of a transition metal?
total charge of complex - sum of all charges of ligands
How do you work out the overall charge of a complex?
sum of the charge on the central on the central metal ion and the charges on each of the ligands
What angle is linear and coordination number?
180
2
What angle is tetrahedral and coordination number?
109.5
4
What is haemoglobin?
A globular protein that contains four Fe2+ centres, each with a porphyria ligand taking up four of the six coordinate bonds. The other two bonds is the rest of the globin and an O2 or H2O
Why does oxygen come off and when?
Not a good ligand
When needed to transfer cells for respiration
What are better ligands than O2?
Cyanide ions (CN-) and carbon monoxide (CO)
Why is CN- and CO toxic?
Prevent the transfer of oxygen
When does cis-trans isomerism occur?
In octahedral and square planar complexes - where there are 2 ligands of one type different to the other ligands
When does optical isomerism occur?
In octahedral complex with 3 bidentate ligands
Explain one risk associated with the use of cisplatin as an anticancer drug.
Kills healthy cells and causes damage (side effect hair loss)
May attach to DNA in normal cells
What is ligand substitution?
Reaction where 1 ligand is replaced by another
