Unit 3 | Coordination Chemistry Flashcards
exceptions to electron stability for electron configuration
group 6 and 11 have a stability exception
half-shell is more stable than not
don’t apply to ion
what is the first in first out rule for electron configuration
3d subshell is significantly lower in energy than 4s meaning the 4s e-s before the 3d e-s
to form an ion, 4s electrons are lost first
coordination compounds
metal ion (electropositive and lewis acid) surrounded by molecules and/or anions with lone pairs (lewis bases) called ligands
what do the counter ions do for the complex ion
they are not bonded to the metal ion, they dissolve in aqueous solution and maintain the charge neutrality and are used for calculating the charge of the complex ion
geometries of complex ions
CN 2: Linear (least common)
4: Square planar
4: tetrahedral
6: octahedral (most common)
What is coordination number?
number of bonds b/w the metal ion and the ligands
When to choose a square planar or tetrahedral
square planar: most nd8 e- configuration
tetrahedral: for (most) all other metal ions with CN=4
what is a ligand
a neutral molecule or an ion with a lone pair of e- that can be used to form a bond to the metal ion
bond is often called a coordinate covalent bond
Monodentate ligands
attached to the metal by one bond
Bi/Poly- dentate ligands
attached to the metal by more than one bond or pair of electrons
bi specifically - 2 pairs e-, takes two neighbouring spots on the metal, each ligan counts as two towards coordination #
names of anionic: F-, Cl-, Br-, I-, CN-, OH-
names of neutral: H2O, NH3, CO, NO
fluoro, chloro, bromo, iodo, cyano, hydroxo
aqua, ammine, carbonyl, nitrosyl
how much bonds in : (en), (ox), (dien), (EDTA)
ethylenediamine, 2
oxalate (oxalato), 2
diethylenetriamine, 3
ethylenediaminetetraacetate, 6
metal exceptions for naming: Fe, Cu, Pb, Ag, Au, Sn
ferrate, cuprate, plumbate, argentate, aurate, stannate
naming rules
name ligands before metal
neutral ligands, anionic ligands replace -ide with o
indicate number of ligands using prefixes; di,tri,tetra,penta,hexa
for ligands whose name already have the di-tri, use bis,tris,tetrakis
prefixes do NOT affect alphabetical order.
Isomers
chemical composition (molecular formula) but are difference due to differences in bonding (structural isomers) or orientation (steroisomers) which can strongly influence compound properties such as colour, interaction with light, reactivity
coordination isomers
a ligand and a counter- ion exchange position (or ligands and counter-ions)
linkage isomers
ligand rearranges and bind through another atom (ambidentate ligands)
NO2-, SCN- OCN-
geometric isomers (cis-trans and fac-mer)
cis - ligands are 90 apart
trans - ligands are 180 apart
fac -the same ligands are 90/90/90
mer - ligands are 180/90/90
optical isomers (enantiomers)
molecules that rotate the plane of light are said to be optically active or chiral (asymmetry so that the mirror image and the original are non-superimposable)
can happen in tetrahedral - with 4 different ligands
octahedral - cis with at least one bidentate
square planar are not chiral! - meaning that it is symmetrical
why doesn’t the valence bond theory work for explaining bonding in complex ions
bonds do NOT involve the orbitals containing d-electrons, no info is given about the energies of d-orbitals
doesn’t explain the magnetic properties
colours
crystal field theory
focuses on the energies of d-orbitals
the ligands are approximated as negative point charges and the metal-ligan bond is ionic
electrostatic interactions b/w lone pair e- and the dorbitals e-s result in coordination
eg set
dz2 amd dz2-y2
t2g
dxy, dxz, dyz
small delta - P (pairing energy) > delta
pairing is not favorable, small gap so will make the jump, filled the t2g and eg sets before pairing up
forms high- spin complexes
large delta - P (pairing energy) < delta
pairing is favourable, large gaps so no jump, e- will first fill the t2g set and pair before jumping to eg set
from low spin complexes
influence on delta(energy splitting crystal field splitting)’s magnitude
dependant on ligands, increases towards a more positive metal ion
diamagnetic
all e-s are paired, not attracted by a magnetic field
paramagnetic
has unpaired electrons, attracted by a magnetic field
