D-block Flashcards
What is a transition metal
Elements w/ partially filled d/f-shells
Partially filled d/f-shell in most common compound
How to do you work out the number of d e-
No e- = group no. - metal OS
What are the trends in atomic radius
General contraction across period
∵ increasing Zeff
Increase from row 1 -> row 2
Row 2/3 metal in a triad
very similar radii
∵ lanthanide contraction
& increasing Zeff
w/ little shielding from ‘core’ 4f14 shell
What are the anomalies in atomic radius
Mn
∵ irregular solid state structure
Increase for Cu, Zn
∵ greater e- repulsion
What is the trend in ionic radius
Contraction left to right
Decrease Ti 2+ -> Cr 2+
Increase Cr 2+ -> Mn 2+
Decrease Mn 2+ -> Ni 2+
Increase Ni 2+ -> Zn 2+
Irregular
∵ effect d-orbital occupancy
What is the trend in IE
General rise across period
∵ increasing Zeff
What are the anomalies in IE
Dip for Mn+ -> Mn 2+ & Fe 2+ -> Fe 3+
both d6 -> d5
∴ removing paired e-
∴ experiencing repulsion
What is the trend in electronegativity
All relatively low
∵ metallic behaviour
General increase across period
Decrease down triad
in groups 3 -5
increases groups 6 - 12
What is the trend in atomisation energies
Higher than s-block metals
more valency e-
∴ stronger metallic bonds
Maxima at groups 5/6
most unpaired e-
Dip group 7
eg. Mn free atom is 3d5 4s2 & irregular structure
What is the trend in melting point
Stronger metallic bonding than s-block
Generally increase down group (triad)
larger 4d/5d orbitals
better overlap for bonding
What is an oxophilic metal
Metals that tend to be found as oxides
Left of d-block
What are chalcophilic metals
Metals that tend to be found as sulphides
Right of d-block
How can you determine max possible OS
Max possible OS = group number
High OS less common for Fe - Zn
∵ higher Zeff & IE
How do the OS for row 1 metal halides differ
F giver higher metal OS than Cl
∵ more 𝜒
What is the coordination chemistry of a metal cation in aq
Complex, hydrated ion
[M(OH2)6]n+
Ligand lewis base - metal lewis acid
∴ dative bond
What is the coordination chemistry of metal sulfate
MSO4 –H2O–> [M(OH2)6]n+ + SO4 2-
[M(OH2)6]n+ —> M(OH2)5SO4 crystallise
m(OH2)5SO4 –heat–> MSO4
What is the denticity of a ligand
No. donor atoms coordinated to metal
𝜅
What is the coordination number of a metal complex
CN = no. donor atoms attached to metal
When are CN > 6 more common
3rd row d-block & f-block
What are linkage isomers
Ambidentate
eg. NO2 - ligand coordinate through N or O
convert photochemically
What are ionisation isomers
Distinguished by chemical test
eg. [Co(NH3)5(SO4)]Br –Ag+–> AgBr
[Co(NH3)5(SO4)]SO4 –Ag+–> no reaction
What are hydrate isomers
Coordinated H2O vs. water of crystallisation
eg. [Cr(OH2)6]Cl3 vs.
[Cr(OH2)5]Cl2 . H2O
What are geometrical isomers
cis/trans isomers
facial (fac) - 3x z ligands cis to each other
/meridonal (mer) - 2x z ligands cis & 1x z ligand trans to p
What are optical isomers
Two complexes that are
non-superimposable mirror images
& are enantiomers
Why do some d-orbitals experience more repulsion
dz2 & dx2-y2
have lobes pointing along axes
∴ directly towards ligand
so more repulsion of e-
dxy, dxz & dyz
have lobes pointing between axes
∴ less repulsion of e-
How do d-orbitals feel repulsion in a tetrahedral geometry
dz2 & dx2-y2
feel repulsion from ligands
How does Δt compare to Δo
Δt ≈ 4/9 Δo
How do high spin octahedral d-orbitals fill
All 5 d-orbitals singularly occupied before pairing
If Δo small
e- prefers high spin
How do low spin octahedral d-orbitals fill
eg only occupied orbital
after t2g filled w/ 6e-
If Δo large
e- prefers low spin
How do tetrahedral d-orbitals fill
High & low spin fill in the same ways as octahedral
(3x t2g orbitals at the bottom)
Low spin rare
∵ Δt usually small
∴ favours high spin
What is the crystal field stabilisation energy
CFSE = change in energy resulting from splitting of d-orbitals
CFSE = E (w/ splitting) - E (w/out splitting)
What is P in CFSE
Pairing energy
due to repulsion between paired e-
only count extra pairings due to splitting
How does Δo/Δt compare to P
For d4 - d7
low spin if Δo > p
high spin if Δo < p
For d3 - d6
low spin if Δt > p
high spin if Δt < p
How do octahedral and tetrahedral complexes compare
O strongly favour for
d3, d8, low spin d4 - d7
No CFSE difference for
d0, d5 high spin, d10
Small CFSE difference for
d1, d2, high spin d6, d7
What is the effect of CFSE on hydration enthalpies of M2 ions
ΔhydH generally gets larger
across 3d row
ionic radius gets smaller
clear trend for d0, d5, d10 (0CFSE)
Deviation from smooth curve for other ions
∵ additional stabilisation of [M(OH2)6]2+
hydrated ions by CFSE
What is ferromagnetism
Electron spins only align below curie temp
eg. 1043K for Fe
Above critical temp
material becomes paramagnetic
What affects d-orbital splitting
- Charge (OS) of metal ion
higher +ve change on M n+
increases CFS - Position of metal in d-block
CFS increases down a group
larger 4d/5d orbitals interact
more w/ ligands - Nature of ligand
ligands can be ranked
to spectrochemical seriesv. strong field ligand: CN-, CO strong field ligand: NH3 weak field ligand: H2O, halogens
What is the Jahn-Teller effect
Some octahedral complexes
9th e- could go into either dx2-y2 or dz2
Molecule in degenerate electronic state
undergo distortion to remove degeneracy
Causes further splitting
& lowers overall energy
What are the distortions for octahedral complexes
1/3 e- in eg orbitals
large tetragonal
elongation or compression
1/4 e- t2g orbitals
small tetragonal compression
2/5 2- in t2g orbitals
small tetragonal elongation
d3, d8, d10, high spin d5, low spin d6
no distortion
When is square planar favoured
For d8 complexes
What are the comparisons of 4-coordinate d8 complexes
Square planar gives larger CFSE
especially for 2/3 metals
Rh(I), Ir(I), Pd(II), Pt(II), Au(III)
Tetrahedral minimises repulsion between ligands
eg. Ni(II) complexes w/ bulky ligands or weak field ligands
Tetrahedral = paramagnetic
Square planar = diamagnetic
How can wavelength of complexes be calculated
ΔE = hv = hc/𝜆
What are the selection rules
- Laporte Rule
For transition to be allowed
qn must change by ±1
eg. s -> p or p -> d - Spin selection rule
e- cannot change its spin during transition - Parity selection rule
g -> g or u -> u forbidden
g -> u allowed
Are d -> d transitions allowed
Formally formatted by Laporte in octahedral complexes
Molecule w/ polyatomic ligands
not perfectly octahedral
vibrations mean centre of symmetry
can be temporarily lost
some mixing of orbital character can occur
∴ d -> d transitions can occur but relatively weak
What is the affect of acid reaction of d-block metal ions in aq
Solutions [M(OH2)6]n+ are acidic
e- density pulled towards M n+ cation
M n+ polarises coordinated H2O
O-H polarity increases
depends on charge M n+
Proton transfer to solvent H2O raises acidity
What happens when base is added to coordinated complexes
Deprotonation of coordinated water ligand
(not ligand exchange)
What happens when NH3 is added to coordinated complexes
Deprotonation of coordinated water
(reversible reaction)
In excess NH3 ligand exchange occurs
What are the types of ligand substitution
Anation = neutral replaced by anion
Aquation = any other ligand replaced by water
What are the classifications of kinetics for ligand substitution
Labile = complexes undergo rapid substitution
Inert = complexes undergo slow substitution
row 2/3 [M(OH2)6]n+ generally more inert
What is the K equation for ligand substitution
K = [MX5Yn-][X-] / [MX6][Y-]
What is the stability constant
βn = k1 k2 k3 … kn = [MLn] / [M][L]^n
logβn = log (k1) + log (k2) + … + log (kn)
What is the chelate effect
Enhanced stability of complexes
containing chelate ligands (eg. polydentate)
over one containing similar monodentate ligands
How is ΔG calculated from the stability constant
ΔG = -RT x lnβ
ΔG = -RT x ln10 x logβ
What is the macrocyclic effect
Complexes of macrocyclic ligands
show even greater stability
Donor atoms ‘pre-organised’
What is the effect of chelate ring size on stability
As chelate ring size increase
logK generally decreases
largest k = most stable
What is the Irving-Williams series
Trend of logβ where M is different metal ions
Peaks in -CFSE/Δo for d3 and d8
Trough for d0, d5, d10
∵ decreasing ionic radius left -> right
trend in CFSE for d5 -> d10
larger Δo in product [M(en)3]2+
What are the interactions between hard/soft acids/bases
Hard acid-hard base
interactions more electrostatic in character
dominated by +/- charges
Soft acid-soft base
interactions more covalent in character
dominated by interactions of donor/acceptor orbitals
