Metal Coordination Complexes Flashcards
Ligands
Lewis bases form coordination complexes with transition metals and ions
Monodentate
Ligands that form a single coordination covalent bond
Chelating ligands
Multidentate ligands that form more than one bond
Meridonal stereoisomers (mer-)
Ligands that bond in coplanar fashion
Facial stereoisomers (fac-)
Ligands that bind in a co facial fashion
Molecular point groups
Nomenclature used to describe the geometry/symmetry of coordination complexes
Crystal field theory
Model explaining how the presence of ligands can affect the electron configuration of the metal atom
18 electron rule
A way of gauging the relative stability of a complex
Identity (E)
All molecules have identity, i.e., they can rotate about 360 degrees and yield the same , indistinguishable configuration
Center of symmetry (i)
A line that divides a molecule into two identical parts, such that every atom through i meets equivalent atoms at a distance equidistant from i
Rotation axis (Cn)
Rotation about 360degrees/n yields the same configuration;
Mirror plane (sigma)
Reflection through s mirror plane yields the same configuration; can have sigma v (vertical) or sigma h (horizontal) mirror planes
Rotation-reflection axis (Sn)
Some molecules exist such that rotation about an acid followed by a reflection through a plane perpendicular to the axis, yields the same configuration
Symmetry operations
When the reflections are applied to a molecule and results in a representation that’s indistinguishable from the starting configuration
Molecular point group
The group of all possible symmetry operations that can be performed on molecules of a given configuration
Crystal field (ligand field)
Field created by charged ligands where the energy cause the d orbitals to be split by the electric field into two or more groups that will have different designation depending on the symmetry
Common point groups for t-metals
Oh (octahedral), Td (tetrahedral), C4v (square planar)
Ways of filling octahedral complexes
High spin (HS) and low spin (LS)
High spin (HS)
A complex caused when the strength of the crystal field interaction energy is less than the energy required to pair up the electrons
Low Spin (LS)
A complex caused when the crystal field interaction energy is greater than the pairing energy
Strong ligands
They interact strongly with the d orbitals and will follow the Aufbau principle; low spin usually
Weak ligands
Interact weakly with the d orbitals and will follow Hund’s rule; high spin usually
Aufbau principle
Electrons will completely fill the lower energy levels first
Hunds rule
Spread the electrons first before pairing the mm up; all orbital take one e- before any of them accepts a second
Effective magnetic moment (Ueff)
Ueff = sqrt(n(n+2)), where n = # of unpaired e-
Jahn-teller effect
The distortion of metal complexes in order to lower electron degeneracy
Irving-Williams series
Keq increase from left to right (stability of complexes);
Ba2+>Sr2+>Ca2+>Mg2+>Mn2+>Fe2+>Co2+>Ni2+>Cu2+
Spectrochemical series
Splitting increases from left to right;
Br-
Ligand substitution
A coordinate ligand is replaced by another one [MLnX] + Y -> [MLnY] +X
Trans effect
Ligand ability to cause additional ligands to add trans to them; effect increases;
H2O
18 electron rule
A rule of thumb that is used to predict reactivity and stability
18 electron rule first step
1) assign metal it’s number of valence s and outermost d electrons
18 electron rule step 4
when organo metallic complex has a charge, consider a positive charge as an e- deficiency and subtract it from the total; consider a (-) charge as an excess of e- and add the corresponding # to the total
18 electron rule step 2
2.) assign electrons to ligands: H, Ch3,CH2CH3, CN, OH, CI, NO = 1 PR3, NH2, NH3, CO, RCN, ROOR = 2 Cyclopentadienyl, indenyl = 5 Benzene = 6 Cyclooctatetraene = 8
18 electron rule step 3
add up both contributions
