2 GemstonesThe colors of rubies and emeralds are both due to the presence of Cr+3 ions – the difference lies in the crystal hosting the ionIn rubies, some Al+3 ions in the Al2O3 are replaced by Cr+3 ions.In emeralds, some Al+3 ions in the Be3Al2(SiO3)6 are replaced by Cr+3 ions.
3 Electron Configuration For 1st & 2nd transition series = ns2 (n−1)dxFe = [Ar]4s23d6; Zr = [Kr]5s24d2For 3rd transition series = ns2 (n−2)f14 (n−1)dxRe = [Xe] 6s2 4f14 5d5Some individuals deviate from the general pattern by “promoting” one or more s electrons into the underlying d to complete the subshellForm ions by losing the ns electrons first, then the (n – 1)d
4 Lewis Acids & Bases Section 15.11 G.N. Lewis – noticed that acid-base chemistry always involves an electron pair.BH3 + NH3 H3B:NH3Acid = electron pair acceptorBase = electron pair donorGreatly expands what we view as an “acid”LEP #1
5 ComplexesAn ion like [Ag(NH3)2]+1, are called complex ions as well as coordination compounds.The molecules or ions that bond to the metal are known as ligands.The coordination sphere is the metal and the total number of ligands bonded to it.The complex is a neutral charge salt, which may contain additional cations or anions not bonded to the metal.
6 Complexes [Cu(NH3)4] SO4 The complex ion charge is _____. The charge of Copper is _____.Coordination number is the number of lone pairs donated to the metal.Coordination numbers of 2, 4, and 6 are most common.
9 Chelates Ligands are sometimes referred to as chelates (Greek = claw). Most are monodentate (one “toothed”) like NH3, Cl-, CN-, etc.A few are bidentate (two “toothed”) like ethylenediamine and the oxalate ion.A few are polydentate like EDTA.
10 ChelatesThe formation of complexes favors the products as seen in Chapter 17.Ni+2(aq) NH3(aq) Ni(NH3)6+2 ; Kf = 4 E8Ni+2(aq) en(aq) Ni(en)3+2(aq) ; Kf = 2 E18The larger K for the bidentate ligand is known as the chelating effect.Uses of EDTA and the EDTA challenge.
11 Metals in Living Systems Nine metals important to life – V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Mo – owe their roles to their ability to form complexes with ligands.The role of iron in hemeglobin is a perfect example.In hemeglobin, the iron is bonded to four N atoms in a molecule called porphoryn.The fifth site is bonded to the protein (globin).This leaves one position empty in the octahedral geometry.
13 Nomenclature Complexes are named using a systematic method. Rules: Cation named first, then anionName of the complex is always one word, name of ligands come first and in alphabetical orderName of ligands include prefixes if more than one Anionic ligands get an –o suffixName of metal also includes oxidation number in ( ). If complex is an anion, metal name ends in –ate. Ex) Vandium = Vanadate, Ferrum = FerrateNote: Some metals use old Latin names!
15 IsomersIsomers are compounds with the same formula but either atoms are in a different order (structural) or atoms are in a different spatial arrangement (stereoisomers).
16 Structural IsomersA linkage isomer occurs when a ligand can bond through a different atom.NO2- can bond through the N (NO2-) or the O (ONO-).Another one is SCN-.
17 Structural IsomersA coordination sphere isomer occurs when the ligands bonded to the metal are exchanged for ones outside of the coordination sphere.For example, the formula CrCl36H2O has several forms.[Cr(H2O)6] Cl3 is purple[Cr(H2O)5Cl] Cl2H2O is green
18 StereoisomersA geometric isomer occurs when the spatial orientation of a complex can be changed. These are referred to as cis-trans isomers.Example is the square planar geometry of PtCl2(NH3)2.
19 StereoisomersCan also produce cis-trans for octahedral complexes if general formula is: MX4Y2.Example is Co(NH3)4Cl2+.
20 StereoisomersA second type of geometric isomerism can occur if the general formula is MX3Y3 called fac-mer (short for facial and meridian).An example is Co(NH3)3Cl3.
21 StereoisomersAn optical isomer occurs when the mirror image of the complex is non-superimposable.The pair of isomers are called enantiomers.
22 StereoisomersIn complexes, the only way to get optical isomerism is with a 6-coordinate system and two or three bidentate ligands.Most of the chemical and physical properties of any enantiomer pair are identical.However, towards other optically active molecules only one might react.
23 StereoisomersIf the two mirror image complex ions can be separated, then they can be tested with plane polarized light.
24 Color Some ions are highly colored. Some ions are not colored. Cu+2 = blueNi+2 = greenCo+2 = pinkSome ions are not colored.Zn+2Ba+2Al+3
25 Color Color depends on two factors: _______________Compounds must absorb some visible light to have a color.
26 Color A compound’s color can be due to: either it absorbs all wavelengths but that colorOR, it absorbs one color exclusivelyFor the second choice, the color is then the complimentary color.Spectrum for Ti(H2O)6+3
27 Color Wheel The color wheel shows the complimentary colors. Those that are opposite are complimentary.
29 Electron Configurations In period 4, the d orbitals start with Sc.Sc: [Ar] 4s2 3d1Orbital diagram – shows how each of the d orbitals are filled.Example) Fe: [Ar] 4s2 3d6Will see many metal ions, so that means you have to remove some of the electrons.Co+3
31 Crystal Field Theory (CFT) As the ligand donates its electron pair to form the bond, it interacts with the metal’s d orbitals.Not all the d orbitals are affected in the same way.This splits the d orbitals into different levels.
37 High and Low SpinNormally, electrons fill the d orbitals one at a time WITH parallel spins.Octahedral complexesSmall D = fill each level first before pairingLarge D = fill the lower level completely before moving to upper levelonly matters for d4 to d7 configurations
38 High and Low Spin[CoF6]-3[Co(CN)6]-3They are different!
39 Spectrochemical Series Ranks the ligands from weak to strong field.Cl- < F- < H2O < NH3 < en < NO2- < CN- increasing D
40 Tetrahedral and Square Planar D is always small for tetrahedral complexes so these are always high spin.D is always large for square planar complexes so these are always low spin.
41 Tetrahedral and Square Planar Ni+2 can be eitherd8[NiCl4]-2[Ni(CN4)]-2
42 Measuring Delta D = hc / l Remember, though, if a compound is red, then it absorbs green.Use wavelength in green part of the spectrum!