Chapter 23: Transition Metals and Coordination Compounds

Question 1

Properties of Transition Metals

• Size
• Ionization energy
• Electronegativity
• Oxidation states

Answer 1

• All have orbitals that can be involved with metallic bonding
• Little variation in size across a row
• 3rd transition row not larger
• Ionization energy: First ionization E of transition elements increases across; move down a group, third transition row has higher ionization energy
• Electronegativity: Increase across a row; increase down from first row (no further increase in 3rd or 4th)
• Exhibit variety of oxidation states

Question 2

Lanthanide contraction

Answer 2

• Outer electron are held more tightly by nucleus and offset typical increase in size between periods

Question 3

Transition Metal Electron Configurations

Answer 3

• Ground state e- for first two rows: ns^2(n-d)d^x

- 3/4 rows: ns^2(n-2)f^14(n-1)d^x

Question 4

Complex ion

Answer 4

• Contains central metal ion bound to one or more ligans

Question 5

Ligand

Answer 5

Lewis base (e- donor that forms bond with metal)

Question 6

Coordination compound

Answer 6

Complex ion combines with one or more counter ions

Question 7

Primary Valence

Answer 7

Oxidation state on central metal atom

Question 8

Secondary valence

Answer 8

Number of molecules or ions bound to metal ions (this is the coordination number)

Question 9

Coordinate covalent bond

Answer 9

• Bond formed by donation of pair of e- from ligand to empty orbital in metal

Question 10

Monodenate

Answer 10

Ligand that only donates one e- pair to central metal

Question 11

Bidenate

Answer 11

• Ligands that donate two pair of e-

Question 12

Polydenate

Answer 12

• Ligand that donates more than two pairs of e-

Question 13

Chelate

Answer 13

• Complex ion with bidenate or polydenate ligand; coordinating ligand is chelating agent

Question 14

Common Ligand

Answer 14

• Water (H2O)
• Ammonia (NH3)
• Chloride ion
• Carbon monoxide
• Thiocyanite (SCN-)
• Oxalate ion
• Ethylenediamine (en)
• Ethylenediaminetetradacetate (Edia)

Question 15

Coordination Numbers + Geometrics

Answer 15

• 2: Linear
• 4: Square planar or Tetrahedral
• 6: Octahedral

Question 16

Structural Isomers

Answer 16

• Atoms connected to each other in different ways

Question 17

Steroisomers

Answer 17

Atoms connected in same way; ligands have different spatial arrangement around metal atom

Question 18

Coordination Isomer

Answer 18

• Structural

- Occur when coordinated ligands exchange places with uncoordinated counterion

Question 19

Linkage isomers

Answer 19

• Structural

- Have ligands that coordinate to the metal in different orientations

Question 20

• Geometric isomers

Answer 20

• Stereoisomerism

- Ligands bonding to the metal have different spatial arrangements

Question 21

Cis-Trans Isomers

Answer 21

• Stereo/Geometric
• Compelx ions occur in square plans complexes of general formula MA2B2; or MA4B2
• Cis (same side), trans (opposite sides)

Question 22

Fac-Mer

Answer 22

• Stereo/Geometric
• Octahedral complexes (MA3B3)
• Fac: Ligands on one side
• Mer: Ligands form an arc

Question 23

Optical Isomers

Answer 23

• Nonsuperimposable mirror images of one another
• Chiral: Molecules ions that exhibit this quality
  Enantiomers: Isomers that exhibit property of optical activity

Question 24

Identifying and Drawing

Answer 24

1) Decide whether ligands are mono, bi, or polydenate.
2) Determine coordination number and geometry.
3) Draw
4) Rotate one 180˚, if it is non superimposable then it exhibits optical activity

Question 25

Coordinate valence bond

Answer 25

• Overlap between completely filled atomic orbital and empty atomic orbital

Question 26

Common Hybridization Schemes

Answer 26

• Linear (sp)
• Tetrahedral (sp3)
• Square planar (dsp2)
• Octahedral (d2sp3)

Question 27

Crystal Field Theory (general definition)

Answer 27

• Bonding model for transition metal complexes that accounts for color and magnetism

Question 28

Octahedral Complexes

Answer 28

• Form because attractions between e- on ligands/positive change on metal ion; e- on ligands also repel unhybridized metal d orbital

Question 29

Strong-field complexes

Answer 29

• Splitting is large

Question 30

Weak-field complexes

Answer 30

• Splitting is small

Question 31

Crystal Field Splitting E (∆)

Answer 31

• Difference in E between the split d-orbitals
• day, dyz, and dxz are lower
• dz^2 and dx^2-y^2 are higher

Question 32

Substance appears to be a color if:

Answer 32

1) Absorbs some of visible light but also transmits wavelengths associated with color
2) Transmits most wavelengths but absorbs complementary color on color wheel

Question 33

Calculate crystal field splitting energy

Answer 33

Photon = hv = hc/lambda

Question 34

Spectrochemical series (list?)

Answer 34

• Arranged from ligands that result in largest ∆ to smallest ∆
  CN- > NO2 > en > NH3 > H2O > OH- > F- > Cl- > Br- > I-
• CN- strongest; cutoff at NH3; remainder are small ∆

Question 35

Electron filling for crystal field shit

Answer 35

• When energy of a d-orbital is split, lower electron orbit fills first
• Once half-filled, either:
  1) Pairs with electrons in lower orbital (or)
  2) Goes into empty orbital of higher energy by overcoming ∆

Question 36

Low-spin complex

Answer 36

• Stronger-field ligands have fewer unpaired electrons (relative to free metal ion)

Question 37

High-spin complexes

Answer 37

• Complexes with weak field ligands

- Have same number of unpaired e- as free metal ion

Question 38

“d” possibilities

Answer 38

• d1-d3: Metal ions always have unpaired e-
• d4-d7: Metal ions have low and high spin possibilities
• d8-d10: metal ions always have lower 3 electron orbitals filled (remaining e- fill two higher orbitals)

Question 39

Tetrahedral and Square Planar Complexes

Answer 39

• Patterns (opposite octahedral formation):
• High E: dxy, dxz, dyz
• Low E: dx^2-y^2, dz^2