Metal Coordination Complexes

Question 1

Ligands

Answer 1

Lewis bases form coordination complexes with transition metals and ions

Question 2

Monodentate

Answer 2

Ligands that form a single coordination covalent bond

Question 3

Chelating ligands

Answer 3

Multidentate ligands that form more than one bond

Question 4

Meridonal stereoisomers (mer-)

Answer 4

Ligands that bond in coplanar fashion

Question 5

Facial stereoisomers (fac-)

Answer 5

Ligands that bind in a co facial fashion

Question 6

Molecular point groups

Answer 6

Nomenclature used to describe the geometry/symmetry of coordination complexes

Question 7

Crystal field theory

Answer 7

Model explaining how the presence of ligands can affect the electron configuration of the metal atom

Question 8

18 electron rule

Answer 8

A way of gauging the relative stability of a complex

Question 9

Identity (E)

Answer 9

All molecules have identity, i.e., they can rotate about 360 degrees and yield the same , indistinguishable configuration

Question 10

Center of symmetry (i)

Answer 10

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

Question 11

Rotation axis (Cn)

Answer 11

Rotation about 360degrees/n yields the same configuration;

Question 12

Mirror plane (sigma)

Answer 12

Reflection through s mirror plane yields the same configuration; can have sigma v (vertical) or sigma h (horizontal) mirror planes

Question 13

Rotation-reflection axis (Sn)

Answer 13

Some molecules exist such that rotation about an acid followed by a reflection through a plane perpendicular to the axis, yields the same configuration

Question 14

Symmetry operations

Answer 14

When the reflections are applied to a molecule and results in a representation that’s indistinguishable from the starting configuration

Question 15

Molecular point group

Answer 15

The group of all possible symmetry operations that can be performed on molecules of a given configuration

Question 16

Crystal field (ligand field)

Answer 16

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

Question 17

Common point groups for t-metals

Answer 17

Oh (octahedral), Td (tetrahedral), C4v (square planar)

Question 18

Ways of filling octahedral complexes

Answer 18

High spin (HS) and low spin (LS)

Question 19

High spin (HS)

Answer 19

A complex caused when the strength of the crystal field interaction energy is less than the energy required to pair up the electrons

Question 20

Low Spin (LS)

Answer 20

A complex caused when the crystal field interaction energy is greater than the pairing energy

Question 21

Strong ligands

Answer 21

They interact strongly with the d orbitals and will follow the Aufbau principle; low spin usually

Question 22

Weak ligands

Answer 22

Interact weakly with the d orbitals and will follow Hund’s rule; high spin usually

Question 23

Aufbau principle

Answer 23

Electrons will completely fill the lower energy levels first

Question 24

Hunds rule

Answer 24

Spread the electrons first before pairing the mm up; all orbital take one e- before any of them accepts a second

Question 25

Effective magnetic moment (Ueff)

Answer 25

Ueff = sqrt(n(n+2)), where n = # of unpaired e-

Question 26

Jahn-teller effect

Answer 26

The distortion of metal complexes in order to lower electron degeneracy

Question 27

Irving-Williams series

Answer 27

Keq increase from left to right (stability of complexes);

Ba2+>Sr2+>Ca2+>Mg2+>Mn2+>Fe2+>Co2+>Ni2+>Cu2+

Question 28

Spectrochemical series

Answer 28

Splitting increases from left to right;

Br-

Question 29

Ligand substitution

Answer 29

A coordinate ligand is replaced by another one [MLnX] + Y -> [MLnY] +X

Question 30

Trans effect

Answer 30

Ligand ability to cause additional ligands to add trans to them; effect increases;
H2O

Question 31

18 electron rule

Answer 31

A rule of thumb that is used to predict reactivity and stability

Question 32

18 electron rule first step

Answer 32

1) assign metal it’s number of valence s and outermost d electrons

Question 33

18 electron rule step 4

Answer 33

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

Question 34

18 electron rule step 2

Answer 34

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

Question 35

18 electron rule step 3

Answer 35

add up both contributions