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Transition and Coordination Compounds P a g e | 1

Transition Metals and Coordination:

Homework: Read Chapter 24 Bonus Ch 24: 19, 23, 25, 43, 47, 51, 59 Check for the MasteringChemistry.com assignment and complete before due date For Fun: How are transition reactions similar to Reality TV?

Gemstones: The colors of rubies and emeralds are both due to the presence of Cr3+ . The difference lies in the crystal hosting the …

Transition Metals: Many colorful compounds have transition metals. Both ionic and [complex coordination] compounds can be formed The properties of the transition metals are similar to each other and very different to the properties of the main group metals high mp, high densities, moderate to very hard, very good electrical conductors Transition metals have configurations that fill the d orbitals last, yet when losing the valence s electrons are generally lost first. When the loses two electrons to become Zn+2 it is the 4s2 electrons that are lost… Zn [Ar] 4s23d10 Zn+2 [Ar] 3d10 Similarities in properties come from similarities in valence electron configuration

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Electron Configurations: The difference in energy between ns and (n-1)d orbitals is not very large. This causes some transition metal to have irregular electron configuration patterns like those below… Cr = [Ar]4s13d5 Cu = [Ar]4s13d10 Mo = [Kr]5s14d5 Ru = [Kr]5s14d7 Pd = [Kr]5s04d10 Ag = [Kr]5s14d10 Electron configurations are experimentally determined. Ni, Tc+2, and W behave predictably…

Ni

Tc2+

W

Atomic size: The atomic radii of all the transition metals are very similar, with a small increase in size down a column and a dip in size in the middle.

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Ionization Energy: The 1st IE of the transition metals slowly increases across a series.

Electronegativity: The of the transition metals slowly increases across a series, except for last element in the series

Oxidation States: Unlike main group metals, transition metals often exhibit multiple oxidation states Highest oxidation state is the same as the group number for Groups 3B to 7B

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Complex Ions: Complex ion formation is a type of Lewis acid–base reaction. A bond forms when a pair of electrons is donated by one atom creating a coordinate When a transition metal cation combines with multiple anions or neutral molecules it makes a complex ion The attached anions or neutral molecules are called The overall charge on the complex ion can be positive or negative, depending on the numbers and types of ligands attached

Names of Common Metals in Complex Ions: Name in Cationic Complex, follow Name in Anionic Complex, follow with Roman numeral ( -- ) with Roman numeral ( -- ) chromium (-?-), Cr+? chromate(-?-) Cobalt (-?-), Co+? cobaltate(-?-) Copper (-?-), Cu+? cuprate(-?-) Gold (-?-), Au+? aurate(-?-) Iron (-?-), Fe+? ferrate(-?-) Lead (-?-), Pb+? plumbate(-?-) Manganese (-?-), Mn+? manganate(-?-) Molybdenum (-?-), Mo+? molybdate(-?-) Nickel (-?-), Ni+? nickelate(-?-) Platinum (-?-), Pt+? platinate(-?-) Silver, Ag+ argentate Tin (-?-), Sn+? stannate(-?-) Zinc, Zn+2 zincate

Examples: COMPLEX CATIONS: +3 [Cr(NH3)6] hexaamminechromium(III) +3 [Fe(CO)6] hexacarbonyliron(III) +2 [Pt(H2O)4] tetraaquaplatinum(II) COMPLEX ANIONS: -3 [Cr(CN)6] hexacyanochromate(III) -3 [Fe(Br)6] hexabromoferrate(III) -2 [Pt(OH)4] tetrahydroxoplatinate(II) Transition Metals and Coordination Compounds P a g e | 5

Ligands: Ligands must have a pair of nonbonding electrons that can be shared to form the coordinate covalent bond with the transition metal cation. Some ligands form more than one coordinate covalent bond if they have lone pairs on different atoms that are separated enough so that both can bond to the metal A chelate is a complex ion containing a multidentate and the ligand is called the chelating agent (from Greek word chela = claw): Example ligands:

Monodentate: H2O or NH3 (one atom in ligand has nonbonding electrons)

Bidentate: Polydentate: Ethylenediamine (en) Ethylenediaminetetraacetate (EDTA)

Names and Formulas of Common Ligands: Ligand (anions) Name in complex ion Bromide, Br-1 bromo Chloride, Cl-1 chloro Hydroxide, OH-1 hydroxo Cyanide, CN-1 cyano Cyanate, OCN-1 cyanato (O to metal) isocyanato(N to metal) -1 Nitrite, NO2 nitro (N attaches to metal), nitrito(O attaches to metal) -2 Oxalate, C2O4 (ox) oxalato Ethylenediaminetetraacetate ethylenediaminetetraaceto (EDTA)-4 Ligand (neutral molecules) Name in complex ion

Water, H2O aqua

Ammonia, NH3 ammine , CO carbonyl Ethylenediamine (en) ethylenediamine Transition Metals and Coordination Compounds P a g e | 6

Geometries in Complex Ions:

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Coordination Compounds: When a complex ion combines with counter-ions to make a neutral compound it is called a coordination compound The primary valence is the oxidation number of the metal Coordination number (also called secondary valence) is the number of bonds (not ligands) to the metal. Coordination numbers range from 2 to 12, with the most common being 6 and 4

Example: [Co(NH3)6]Cl3

Naming Coordination Compounds: 1. Determine the name of the counter ions 2. Determine the ligand names and list them in alphabetical order 3. Determine the name of the metal cation 4. Name the complex ion: a) naming each ligand alphabetically, adding a prefix in front of each ligand to indicate the number found in the complex ion... prefixes: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca, dodeca (12) b) following with the name of the metal cation 5. Write the name of the cation followed by the name of the anion Name the coordination compound: [Co(NH3)6]Cl3 3 counter ions Cl-1 name______

NH3 is neutral name______So the charge of cobalt must be +3 +3 Co (in a cationic complex) name______Name the cation then the anion Name of the coordination compound ______Transition Metals and Coordination Compounds P a g e | 8

Follow the naming rules Name [Cr(H2O)5Cl]Cl2 Name K3[Fe(CN)6]

[Cr(H O) Cl]+2 is a K+1 is potassium, Identify the cation and anion, and 2 5 complex cation, [Fe(CN) ]-3 is a complex the name of the simple ion 6 Cl-1 is chloride ion Give each ligand a name and list H O is aqua 2 CN-1 is cyano them in alphabetical order Cl-1 is chloro Cr+3 is chromium(III) Fe+3 is ferrate(III) Name the metal ion complex ion is a cation complex ion is anionic Name the complex ion by adding prefixes to indicate the number of [Cr(H O) Cl] +2 is 2 5 [Fe(CN) ]-3 is each ligand followed by the name pentaquachloro- 6 hexacyanoferrate(III) of each ligand followed by the chromium(III) name of the metal ion Name the compound by writing [Cr(H O) Cl]Cl is the name of the cation before the 2 5 2 K [Fe(CN) ] is potassium pentaquachloro- 3 6 anion. The only space is between hexacyanoferrate(III) chromium(III) chloride ion names.

Try naming:

Na2CuBr4 and [Co(NH3)2(CO)4](NO3)3

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Isomers: Structural isomers are molecules that have the same number and type of atoms, but they are attached in a different order Coordination isomers: ligand and counter ions exchange places Linkage isomers: ligands attached to the central cation through different ends of the ligand structure

+2 [Co(NH3)5NO2] , pentaamminonitrocobalt (III) and pentaamminonitritocobalt (III) Transition Metals and Coordination Compounds P a g e | 10

Stereoisomers are molecules that have the same number and type of atoms, and that are attached in the same order, but the atoms or groups of atoms point in a different spatial direction Geometric isomers: different special arrangements Two identical ligands: tetrahedral or octahedral complex; cis- adjacent , trans-opposite Three identical ligand: octahedral complex; fac-all three ligands adjacent, mer- the three ligands form an arc around the center

Optical isomers: nonsuperimposable mirror images +1 [Co(en)2Cl2]

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Bonding in Complex ions: Valence Bond theory: Bonding takes place when the filled atomic orbital on the ligand overlaps an empty atomic orbital on the metal ion. Explains geometries well, but doesn’t explain color or magnetic properties. Crystal Field theory: Bonds form due to the attraction of the electrons on the ligand for the charge on the metal cation. Electrons on ligands repel electrons in unhybridized d orbitals of metal ion d orbitals are split The difference in energy depends on complex formed and kinds of ligands crystal field splitting energy strong field splitting and weak field splitting

Octahedral Complex: Higher energy for positions with greater orbital overlap, ligands

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Size of the crystal field splitting energy, , Depends on the kinds of ligands and their relative positions on the complex ion, as well as the kind of metal ion and its oxidation state Large Small Strong field ligands weak field ligands -1 -1 -1 -1 -1 -1 -1 CN > NO2 > en > NH3 > H2O > OH > F > Cl > Br > I

Depends on the type of cation; increases as charge on metal increases and increases down a group Co3+ > Cr3+ > Fe3+ > Fe2+ > Co2+ > Ni2+ > Mn2+

Color and Complex Ions: Transition metal ions show many intense colors in host crystals or solution The color of light absorbed by the complex ion is related to electronic energy changes in the structure of the complex the electron “leaping” from a lower energy state to a higher energy state The observed color is complementary color of one that is absorbed

Red-Purple: is least absorbed in +3 [Ti(H2O)6] so that is the color +3 seen in a solution of [Ti(H2O)6]

Green and yellow are absorbed the strongest, the complementary colors are “seen” Transition Metals and Coordination Compounds P a g e | 13

Colors of complex ions: Due to electronic transitions between split d sublevel orbitals. The wavelength of maximum absorbance can be used to determine the size of the energy gap between split d sublevel orbitals

Ephoton = h = hc/ = h = 6.6262 x 10-34 J·s c = 3.00 x 108 m/s Try this: -3 [Cr(Cl)6] has a maximum absorption spectrum at 735 nm. Calculate the crystal field spitting energy in J/photon and kJ/mol.

Magnetic Properties and Crystal Field Strength: Octahedral-6 attached The electron configuration of the metal ion with split d orbitals depends on the strength of the crystal field Weak field: 4th and 5th electrons will go into the higher energy if the energy gap is small unpaired electrons = paramagnetic complex Strong field: th th 4 thru 6 electrons will pair the electrons in dxy, dyz, dxz if energy gap is large paired electrons = diamagnetic complex

-3 -1 Try this: The complex ion [AlF6] is paramagnetic. Is the F ligand inducing a strong or weak field? Transition Metals and Coordination Compounds P a g e | 14

Tetrahedral - 4 attached (not on test)

Ligands repel more strongly with the dxy, dyz, dxz orbitals in the tetrahedral geometry Reversing the order of energies compared to the octahedral geometry Almost all tetrahedral complexes are high spin, d orbitals interact with only four ligands, so is generally smaller.

Square Planar (not on test) Occurs in d8 metals; Pt2+, Pd2+, Ir+, Au3+ The most complex splitting pattern Almost all are low-spin complexes

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Applications: Extraction of metals from ores; silver and gold as cyanide complexes Use of chelating agents in heavy metal poisoning; EDTA for Pb poisoning Chemical analysis; qualitative analysis for metal ions blue = [CoSCN]+ red = [FeSCN]2+ Ni2+ and Pd2+ form insoluble colored precipitates with dimethylglyoxime Commercial coloring agents; Prussian blue = mix hexacyanoferrate(II) and (III) Biomolecules porphyrin ring cytochrome C chlorophyll

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Transition Metal and Coordination Compounds Practice Problems:

1. For each of the complexes below, give the coordination number, oxidation state of the metal and the formula for the phosphate salt (if the complex is a cation) or the aluminum salt (if the complex is an anion), and name the compound. +1 a) [Mo(CN)2(en)2] -1 b) [Co(H2O)(OH)2Br] +1 c) [Ag(NH3)2] -2 d) [PtCl2(NO2)2]

2. Write out formulas, given the following names. a) Pentaaquabromochromium(III) bromide b) Sodium Hexacyanocobaltate(II) c) Bis(ethylenediamine)dinitroiron(III) chloride d) Tetraamminediiodoplatinum(IV) tetraiodoplatinate(II)

-2 3. [PdCl4] is found to be diamagnetic. Is this structure tetrahedral or square planar according to crystal field theory? Draw the energy orbital diagram.

+2 4. Draw two linkage isomers of [Mn(NH3)5(NO2)]

5. a) Three complex ions of cobalt (III) absorb light at wavelengths at 290 nm, 440 nm, 770 nm. Match each complex ion to the appropriate wavelength and predict the color you would expect each solution to be. Refer to the color wheel for complements, 400nm to700nm is visible. -3 -3 -3 Choices: [Co(CN)6] , [CoF6] , [Co(NH3)6]

-3 b) Solve for the crystal field splitting energy in kJ/mol for [Co(NH3)6] .

For Fun: How are transition metal reactions similar to Reality TV? When you mix two parties together you are not sure of the outcome. There are a variety of possible reactions that the parties may undergo.