CH# 17

1. CH# 17 Coordination Chemistry

3. Transition Metals • Transition metals show similarities within a period and a group, different than representative elements • Differences can be attributed to the fact that when electrons are added across a period the valence electrons are not effected. • Therefore group designations are not important here • Behave as metals, strong metallic character

4. Transition Metals • Some differences • Melting point, Tungsten melts 3400°, while mercury -39°C • Some soft, like sodium that can be cut with a butter knife • Reactivity • Some spontaneously react with oxygen like iron, which flakes off • Others react with oxygen to make a colorless tight fitting oxide, such as chromium, thus protecting the surface • Some metals are inert to oxygen such as gold, silver and platinum

5. Transition Metals Ionic compound formation • More than one oxidation state is often observed • Cations, often are complexes, which we will discuss later in this chapter • Most compounds are colored, since complexes absorb visible light • Many compounds are paramagnetic This chapter will deal specifically the first row transition elements

6. Transition Elements

7. Electron Configurations Exceptions to the AUFBAU principle • Cr prefers a half full d as opposed to a full 4s, thus 4s13d5 • Copper prefers a full 3d as opposed to a full 4s, thus 4s13d10 • This half filled, or filled d orbital, is used most of the time to explain this, but other transition metals do not follow this trend.

8. Electron Configurations Many texts explain AUFBAU exceptions of chromium and copper as a half full sublevel are more stable than a full 4 s sublevel, or for copper that a full d-sublevel is more stable than a half full 4s • Why is this not the case in periods below? • The 4 s and the 3 d orbitals are of about the same energy or nearly degenerate. Perhaps there is a larger repulsive force in the 4s than in 3d orbitals. • I do not think any one knows, but it is good to think and create right?

9. Electron Configurations 4d and 5d Transition Series • See the size relation on next slide • Decrease in size as we go from left to right, stopping when the d is half full • Significant drop in size going from 3d to 4d, but 4d and 5d remain about the same size • Called Lanthanide contraction • Adding f electrons below the d and the valence shell shel electrons (shielding) • Thus the effect of the increasing size by adding another shell of electrons, which is normally in transition and representative elements, is offset by the shielding of the added f electrons

10. Transition Element Sizes

11. Oxidation States and IE • See common oxidation states on Next slide • The maximum oxidation state for each transition element going across the row is what we would get by losing both 4s and 3d electrons, toward the end only 2+ is observed, the explanation is that as the effective charge increases thus holding the d electrons tighter. • Reducing ability, decreases from left to right

12. Transition Metal Oxidations #’s

13. Ionization Energies Red dot- First ionization energy (removing 4s e) Bluedot-third ionization energy removing 3d electron, closer to nucleus, thus more tightly held

14. First-row Transition Metals Scandium • Rare element most always +3 oxidation state, ie ScCl3, Sc2O3 • Chemistry of scandium resembles the lanthanides • Colorless compounds • Diamagnetic • Color and magnetic properties are due to d electron, Sc has no d electrons

15. First-row Transition Metals Titanium • Found in the earths crust (0.6%) • Low density and high strength • Fairly inert, and is used in pipes • TiO2 is a very common white pigment • Common oxidation state is +4

16. First-row Transition Metals Vanadium • Found in the earth’s crust about 0.02% • Common oxidation state is +5 • Since vanadium contains d electrons solutions are colored • VO2+ is yellow with V in the +5 oxidation state • VO2+ is blue with V in the +4 oxidation state • V3+ is blue-green with V in +3 oxidation state • V2+ is violet with V in +2 oxidation state

17. First-row Transition Metals Chromium • Rare, but important industrial chemical • Chromium oxide is colorless, tuff, and holds to the metal strongly, almost invisible • Chromium compounds in solution are also colored since they contain d electrons • Common oxidation states are +2, +3 and +6 • Chromium VI is an excellent oxidizing agent! Why? • Strength increases as acidity increases • Chromerge very good glassware cleaning agent • What would we predict for Cr metal? • Cr6+ in the form of dichromate ion usually reduces to the +3 state

18. First-row Transition Metals • Iron • Is the most abundant heavy metal (4.7%) in earth’s crust, Why? • Common oxidation states +2 and +3 • Iron solutions are colored since they contain d electrons • Cobalt • Relatively rare • Hard bluish-white metal • Common oxidation states are +2 and +3 • Oxidation states +1 and +4 are also known • Typical color is rose color

19. First-row Transition Metals • Nickel • Most always the +2 oxidation state • Sometimes +3 oxidation state • Emerald green colored solutions

20. First-row Transition Metals • Copper • Quite common, as sulfides, arsenides, chlorides and carbonates • Great electrical conductor second only to silver • Widely used in plumbing • Found in bronze and brass • Not highly reactive will not reduce H+ • Slowly oxides in air, producing a green oxide • Common oxidation state +2, +1 is also known • Aqueous solution are bright Royal blue • Quite toxic, used to kill bacteria • Paint often contains copper so algae do not grow on the paint

21. First-row Transition Metals Zinc • Quite common in earths crust, usually as ZnS • Great reducing agent, quite reactive • Oxidation state of +2 • Used to galvanize steel

22. Coordination compounds • Transition metals form coordination compounds • Transition metals contain a complex ion attached to ligands via coordinate covalent bonds • Coordination compounds are usually colored and paramagnetic

23. Coordination compounds • Complex ions, usually inside [ ] • Transition coordinately bonded to Lewis bases, the metal is acting as a Lewis acid • Example [CoCl(NH3)5]2+ this cation can combine with anions to balance the charge, thus forming a salt • Ligands are the groups of atoms bonded with a coordinate covalent bond to a transition metal, or a transition metal ion.

24. Coordinate Covalent Bonding

25. Coordinate Covalent Bonding

26. Coordinate Covalent Bonding

27. Coordinate Covalent Bonding

28. Coordination compounds • Alfred Werner was the father of coordination chemistry • Alfred Werner called the salt formation the primary valence • The secondary valence is the formation of the complex ion itself • The compound above has a secondary valence of 6, since it combines with 6 ligands • The primary valence is +2 since that is what needs to be neutralized with anions. • Now days the secondary valence is called the coordination number and the primary valence is called the oxidation state

29. Aqueous Solutions of Metal Ions

30. Coordination Compounds • The number of coordinate covalent bonds formed by the metal ion and the ligands • Variance of 2-8, with 6 being most common. • Geometrical Shape • Ligands = 2, then linear • Rare for most metals • Common for d-10 systems (Cu+, Ag+, Au+, Hg2+) • Ligands = 3, Trigonal planar • Rare for most metals • Is known for d-10 systems (example HgI3‑)

31. Coordination Compounds • Geometrical Shape • Ligands = 4, then tetrahedral, or square planar • Tetrahedral structure is observed for nontransition metals, BeF42- and d-10 inons such as ZnCl42-, FeCl4-, FeCl42- • Square planar is found with second and third row transition metals with d-8 Rh+, Pd2+ -Ligands = 5 • trigonalbipyramid • square pyramidal

32. Coordination compounds • Geometrical Shape • Ligands = 6, then octahedral and prismatic (rare) • Ligands = 7 Relatively uncommon, pentagonal • Second and third row transition metals, lanthanides , and actinides • Lignads = 8, relatively common for larger metal ions, common geometry antiprism and dodecahedron • Lignads = 9 larger metal ions, geometry tricappedtrigonal prism [Nd(H2O)9]3+

33. The Ligand Arrangements for Coordination Numbers 2, 4, and 6

34. Ligands • Atoms attached to a transition metal via coordinate covalent bonds • They are Lewis bases, since they donate a pair of electrons to the transition metal. • Ligands are classified relative to how many attachments to the metal • Monodentate forms one bond to a transition metal • Lignads forming more than bond are called chelating ligands, or chelates

35. Ligands • Ligands are classified relative to how many attachments to the metal • Bidentate, a chelating agent, forms two bonds, examples: • Oxalate • Ethylenediamine • Polydentate forms more than two bonds. • Diethylenetriamine • Ethylenediaminetetraacetic acid

36. Ligands • EDTA is used to remove lead from animals • More complicated ligands are found in biological compounds • EDTA is used as a preservative to tie up substances that could catalyze decomposition of food products

37. Ethylenediamine

38. Ethylenediamminetetracidic acid

39. Coordination of EDTA with a 2+ Metal Ion

40. Nomenclature • Cationic species named before anionic species • Within a complex, the ligands are named first in alphabetical order followed by the metal atom • the names of anionic lignads end in the suffix -o- • chloride ----->chloro • cyanide ----->cyano • oxide ----->oxo • Hydroxide -->hydroxo • Oxalate------>oxalato • Sulfate ------>Sulfato • Nitrate ------>Nitrato

41. Nomenclature • lignads whose names end in -ite or ate become -ito and ato respectively • carbonate ----> carbonato • oxalate-----> oxalato • thiosulfate ----> thiosulfato • Sulfite -----> sulfito • neutral lignads are given the same names as the neutral molecule • exceptions, ammonia (ammine), water (aqua), carbon monoxide (Carbonyl), and NO (nitrosyl)

42. Nomenclature • When there is more than one of a particular ligand, number is specified by di, tri, tetra, penta, hexa, and so forth. when confusion might result, the prefixes bis, tris and tetrakis are employed e.g. bis(ethylenediaminne) • negative (anionic) complex ions always end in the suffix -ate • aluminum -----> aluminate • chromium -----> chromate • manganese ------> manganate • coblat ------> cobaltate • For some metals the -ate is appended to the Latin stem always appears with

43. Nomenclature • the common English name for the element • iron ----> ferr ------> ferrate • copper ---> cupra -----> cuprate • lead ----> plumb -----> plumbate • silver ---> argent ----> argentate • gold ---> aur ----> aurate • tin ----> stann -----> stannate • the oxidation number of the metal in the complex is written in roman numerals within parentheses following the name of the metal

44. Nomenclature • Formula writing • Metal is first, followed by anions, then neutral molecules • If two or more anions or neutral molecules are present, then use alphabetical order. • Nomenclature Examples • tetracyanonickelate(II) ion • tetramminedichlorocobalt(III) ion • sodium hexanitratochromate(III) • diamminesilver(I) ion

45. Nomenclature • Formula writing • Metal is first, followed by anions, then neutral molecules • If two or more anions or neutral molecules are present, then use alphabetical order. • Nomenclature Examples • tetracyanonickelate(II) ion [Ni(CN)4]2- • tetramminedichlorocobalt(III) ion • sodium hexanitratochromate(III) • diamminesilver(I) ion

46. Nomenclature • Formula writing • Metal is first, followed by anions, then neutral molecules • If two or more anions or neutral molecules are present, then use alphabetical order. • Nomenclature Examples • tetracyanonickelate(II) ion [Ni(CN)4]2- • tetramminedichlorocobalt(III) ion [CoCl2(NH3)4]+ • sodium hexanitratochromate(III) • diamminesilver(I) ion

47. Nomenclature • Formula writing • Metal is first, followed by anions, then neutral molecules • If two or more anions or neutral molecules are present, then use alphabetical order. • Nomenclature Examples • tetracyanonickelate(II) ion [Ni(CN)4]2- • tetramminedichlorocobalt(III) ion [Co(NH3)4Cl2]+ • sodium hexanitratochromate(III) Na3[Cr(NO3)6] • diamminesilver(I) ion

48. Nomenclature • Formula writing • Metal is first, followed by anions, then neutral molecules • If two or more anions or neutral molecules are present, then use alphabetical order. • Nomenclature Examples • tetracyanonickelate(II) ion [Ni(CN)4]2- • tetramminedichlorocobalt(III) ion [CoCl2 NH3)4]+ • sodium hexanitratochromate(III) Na3[Cr(NO3)6] • diamminesilver(I) ion [Ag(NH3)2]+

49. Nomenclature • Formula writing • Metal is first, followed by anions, then neutral molecules • If two or more anions or neutral molecules are present, then use alphabetical order. • Nomenclature Examples • tetracyanonickelate(II) ion [Ni(CN)4]2- • tetramminedichlorocobalt(III) ion [CoCl2(NH3)4]+ • sodium hexanitratochromate(III) Na3[Cr(NO3)6] • diamminesilver(I) ion [Ag(NH3)2]+

50. Nomenclature Name the following: • [Ni(H2O)6]Cl2 hexaaquanickel(II) chloride • [Cr(en)3](ClO3)3 • K4[Mn(CN)6] • K[PtCl5 (NH3)] • [Cu(en)(NH3)2][Co(en)Cl4] • [Pt(en)2Br2](ClO4)2