week 10 Flashcards
isomers of complexes cyrstal filed theory, colour magnet (24 cards)
What is a cis isomer?
a stereoisomer in which two groups lie on the same side of a reference plane
What is a cis-trans isomer?
Stereocenters that differ in the positioning of two groups with respect to a reference plane
What are coordination isomers?
isomers that result when ligands are exchanged between a complex cation and a complex anion of the same coordination compound, e.g. [Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6]
What is crystal field theory?
a theory that considers the effects of the polarities or the charges of the ligands in a complex ion on the energies of the d orbitals in an octahedral or tetrahedral complex ion
What is crystal field splitting energy?
the difference in energy between two sets of d orbitals in an octahedral or tetrahedral complex ion
What does degenerate mean?
describes orbitals with the same energy
What does fac stand for?
Facial
What is a facial isomer?
an isomer of an octahedral complex [ML3X3]+n in which the two sets of ligands occupy the face of an octahedron
they occupy a face of the octahedron defined by the donor atoms around the metal.
What is a hydrate isomer?
isomers of complex ions in which water is either coordinated to the transition metal or acts as water of crystallisation
What is high-spin?
describes a complex ion or coordination complex with the maximum number of unpaired electrons
Optical isomers when occur?
Occur most commonly when there is more than one bidentate ligand in the complex. Just as in organic chemistry, optical isomers are non-superimposable mirror images of each other.
What is an ionisation isomer?
isomers in which a coordinated ligand is exchanged with a counterion, e.g. [Co(NH3)5Br]SO4 and [Co(NH3)5SO4]Br
What is a linkage isomer?
isomers that result from the different ways in which an ambidentate ligand can bind to a metal ion
What is low-spin?
describes a complex ion or coordination compound with the minimum number of unpaired electrons
What does mer stand for?
Meridional
What is a meridional isomer?
an isomer of an octahedral complex [ML3X3]+n in which the donor atoms of each set of identical ligands are coplanar
i.e. two ligands are on opposite sides of the complex, with the third lying adjacent to the other two
What is pairing energy?
the energy required to force two electrons to become paired and occupy the same orbital
What is a stereoisomer?
isomers with the same molecular formula and the same connectivity but different orientations of their atoms in space
What is a structural isomer?
isomers with the same molecular formula, but different orders of attachments of the constituent atoms
What is a trans isomer?
a stereoisomer that contains two groups that project on opposite sides of a reference plane
when Colour seen in Many transition metal compounds?
Electrons in partially filled d-orbitals can absorb visible light and move to d-orbitals with slightly higher energy.
NOT Ti4+ Zn2+ S3+c b/c filled for empty d shells
Magnetism - how common? why?
typically transition metals have a partially filled set of d-orbitals and some of the d-electrons may be unpaired.
These unpaired electrons give rise to the complex being paramagnetic. Paramagnetic compounds are attracted to a magnetic field. These unpaired electrons can be randomly aligned. If they are aligned in the same direction then we observe ferromagnetism.
If all electrons are paired this gives rise to diamagnetism. Diamagnetic compounds are repelled by a magnetic field.
what does cf therory state?
This model explains stability, colour and magnetism but not the nature of metal-ligand bonding.
Important Question: What happens to the energy of the metal d-orbitals when 6 ligands pproach?
Consider that the ligands (balls of negative charge) can approach the metal centre (uniform positive charge) in two ways:
(i) Directly along the x, y, z, axes
or
(ii) Between the axes
If we consider the 6 point charges are directed at the metal along the three axes, we will observe greater ligand – d electron repulsion from those electrons on the x-, y- and z-axes (i.e. in dx2-y2 and dz2 orbitals), rather than those between axes (dxy, dyz, dxz)
