transition metals
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91 Terms
transition elements
d-block elements that form one or more stable ions with incompletely filled d-orbitals
properties of transition metals
variable oxidation states
catalytic action
colored compounds
formation of complexes
ligands
particle with lone pair of electrons that bonds to metals by a coordinate (dative) bond
complex
metal ion with coordinately bonded ligands
coordination number
number of coordinate bonds from ligands to metal ion
lewis base
lone pair donor (ligands)
lewis acid
lone pair acceptors
coordintion number linear
2
coordination number 4
square planar, tetrhedral
coordination number octahedral
6
linear bond angle
180
square planar bond angle
90
tetrahedral bond angle
109.5
octahedral bond angle
90
which electrons do transition metals lose first when forming ions
4s
what shape are platinum complexes
square planar
what conditions are needed for a complex ion to display optical isomerism
octahedral molecules with 2 or more bidentate ligands, so the mirror images are non superimposable
what happens in a deprotonation reaction
either ammonia or hydroxide ions remove hydrogen ions from water ligands, and turn them into hydroxide ligands
Which two elements in the periodic table are
exceptions to the rule that the 4s orbital is filled
before the 3p orbital?
Chromium: [Ar]4s1 3d5
Copper: [Ar]4s1 3d10
Why do transition metals form coloured complexes?
When visible light hits a transition metal ion, electrons are excited to higher energy levels.
Some frequencies of visible light are absorbed when electrons jump up to higher orbitals.
The rest of the frequencies of visible light are transmitted or reflected.
These frequencies combine to make the complement of the colour of the absorbed frequencies.
This causes the colour of the complex seen.
[Cr(H2O)6]3+ color (chromium)
green sol
[Cr(H2O)6]3+ + dropwise NaOH color (chromium)
green ppt
[Cr(H2O)6]3+ + excess NaOH (chromium)
green sol
[Cr(H2O)6]3+ + dropwise ammonia (chromium)
green ppt
[Cr(H2O)6]3+ + excess ammonia (chromium)
purple sol
[Mn(H2O)6]2+ (manganese) color
pale pink
[Mn(H2O)6]2+ (manganese) + dropwise NaOH
pale brown ppt (turns darker on exposure to air)
[Mn(H2O)6]2+ (manganese) + excess NaOH
no further reaction
[Mn(H2O)6]2+ (manganese) + dropwise ammonia
pale brown ppt (turns darker on exposure to air)
[Mn(H2O)6]2+ (manganese) + excess ammonia
no further reaction
[Fe(H2O)6]2+ (iron 2+) color
pale green sol
[Fe(H2O)6]2+ (iron 2+) + dropwise NaOH
green ppt (turns brown on exposure to air)
[Fe(H2O)6]2+ (iron 2+) + excess NaOH
no further reaction
[Fe(H2O)6]2+ (iron 2+) + dropwise ammonia
green ppt (turns brown on exposure to air)
[Fe(H2O)6]2+ (iron 2+) + excess ammonia
no further reaction
[Fe(H2O)6]3+ (iron 3+) color
yellow brown sol
[Fe(H2O)6]3+ (iron 3+) + dropwise NaOH
brown ppt
[Fe(H2O)6]3+ (iron 3+) + excess NaOH
no further reaction
[Fe(H2O)6]3+ (iron 3+) + dropwise ammonia
brown ppt
[Fe(H2O)6]3+ (iron 3+) + excess ammonia
no further reaction
[Co(H2O)6]2+ (cobalt) color
pink sol
[Co(H2O)6]2+ (cobalt) + dropwise NaOH
blue ppt (turns pink on exposure to air)
[Co(H2O)6]2+ (cobalt) + excess NaOH
no further reaction
[Co(H2O)6]2+ (cobalt) + dropwise ammonia
blue ppt (turns pink on exposure to air)
[Co(H2O)6]2+ (cobalt) + excess ammonia
pale yellow sol (turns brown on exposure to air)
[Ni(H2O)6]2+ (nickel) color
green sol
[Ni(H2O)6]2+ (nickel) + dropwise NaOH
green ppt
[Ni(H2O)6]2+ (nickel) + excess NaOH
no further reaction
[Ni(H2O)6]2+ (nickel) + dropwise ammonia
green ppt
[Ni(H2O)6]2+ (nickel) + excess ammonia
deep blue sol
[Cu(H2O)6]2+ (copper) color
blue sol
[Cu(H2O)6]2+ (copper) + dropwise NaOH
blue ppt
[Cu(H2O)6]2+ (copper) + excess NaOH
no further reaction
[Cu(H2O)6]2+ (copper) + dropwise ammonia
blue ppt
[Cu(H2O)6]2+ (copper) + excess ammonia
deep blue sol
[Zn(H2O)6]2+ (zinc) color
colorless sol
[Zn(H2O)6]2+ (zinc) + dropwise NaOH
white ppt
[Zn(H2O)6]2+ (zinc) + excess NaOH
colorless sol
[Zn(H2O)6]2+ (zinc) + dropwise ammonia
white ppt
[Zn(H2O)6]2+ (zinc) + excess ammonia
colorless sol
which E-Z isomer is used in the treatment of cancer
cis-platin
describe the structure of cis platin
platinum complex, two ammonia ligands and two chlorine
why does platinum form square planar complexes
it is a period 6 transition element, so behaves differently from period 4 transition elements
describe the anti cancer action of cis platin
its structure enables it to form a bond between two DNA strands, preventing them from replicating and by proxy preventing cancer cells from dividing
why arent all ligands with two lone pairs bidentate ligands
they cannot always bend to the right shape for both lone pairs to form dative bonds
what kind of ligand is EDTA4-
hexadentate
when a monodentate ligand is replaced by a bidentate ligand, what is the effect on ΔSsystem
it increases
why does ΔSsystem increase when monodentate ligands are replaced with bi or multidentate ligands
because the number of species in the system increases
when monodentate ligands are replaced with bi or multidentate ligands, what is the effect on the stability of the complex
it becomes more stable
what is the effect on ΔSsystem when a monodentate ligand is replaced with a multidentate ligand
the increase is greater than when a bidentate ligand replaces a monodentate ligand
describe the basic structure of the haem group in haemoglobin
four nitrogen atoms surrounding a central Fe2+ ion, giving a square planar structure, and a fifth dative bond from the protein to the iron ion
describe the basic structure of oxyhaemoglobin
oxygen forms a sixth dative bond with the Fe2+ ion
what is a common bidentate ligand
NH2-CH2-CH2-NH2 (often shortened to en)
why does carbon monoxide poisoning occur
carbon monoxide has a lone pair on its carbon that enables it to act as a ligand
the dative bond between oxygen and haemoglobin isnt particularly strong (so it can be offloaded to respiring cells)
however, the dative bond between carbon monoxide and haemoglobin is way stronger, so carbon monoxide will perform a ligand exchange with oxyhaemoglobin
define deprotonation
when one or more of the ligands gains or loses a hydrogen ion
define ligand exchange
when one or more ligands around a transition metal ion is replaced by a different ligand
what are the reactions of transition metal ions
redox, deprotonation, ligand exchange, coordination number change
what causes color changes in transition metal ions
changes in the oxidation number of the ion, the ligand, or the coordination number of the complex
what kind of reaction is [Cu(H2O)6]2+ + 2OH- → [Cu(H2O)4(OH2)] + 2H2O
deprotonation
what kind of reaction is [Cu(H2O)6]2+ + 4NH3 + SO42- → [Cu(NH3)4].SO4.H2O + 5H2O (CP14)
ligand exchange
what are the observations when going from [Cu(H2O)6]2+ to [Cu(H2O)4(OH2)] to [Cu(NH3)4(H2O)2]2+
pale blue solution → pale blue ppt → deep blue solution
what is the observation when hydrochloric acid is gradually added to copper (II) sulfate solution
blue → green → yellow
CuCl4 color
yellow
CrO4- color
yellow
Cr2O72- color
orange
Cr3+ color
green
Cr2+ color
blue
V2+ color
purple
V3+ color
green
VO2+ color
blue
VO2+ color
yellow