Chemistry 112 Exam Review Notes Chapter 4 PDF

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Chemistry review for chapter 4 for the exam,...

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Chemistry 1301 Chapter 4 Bonding Metals

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D block metals and transitions metals are used synonymously The first row of the d block is referred to the first transition series, the second row is the second transition series, etc.

Electron Configurations - The electron configurations for metals modify themselves based on the electron count of the metal (filled or half filled shell) - For example, copper is energetically more favourable to completely fill the d orbital and leave the s shell half filled (it’s more energetically stable)

Bonds and Oxidation States - Elements in the 1st transition series can utilize BOTH 4s and 3d electrons in bonding. - Metals don’t necessarily need to use ALL of the electrons for bonding. - Metals having a wide variety of oxidation states, which are are formalisms that allow one to track how many electrons are owned by a metal center - If a metal has ALL of the electrons we expect, then the oxidation state is 0 ( no charge) - If a metal has 1 MORE electron than expected, then the oxidation state is -1, two more, -2 and so on - If a metal has 1 LESS electron than expected, then the oxidation state is +1, two less +2, etc - If Fe is [Ar]4s23d6, then this is an overall neutral iron centre, then oxidation state is 0, written Fe(0) or Fe0 (If [Ar]3d, then Fe2+  or [Ar]3d then Fe3+ 

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Importance of Oxidation States - Oxidation states of a metal can have a profound impact on the physical, chemical, electronic and spectroscopic properties of a material. - In oxidative addition, a chemical entity is added to a metal center with a corresponding increase in oxidation state. - In reductive elimination, the metal center ejects a chemical entity and lowers its oxidation state by 2 electrons. Ligands - Compounds containing transition metals are normally referred to as “complexes”. - The atoms or molecules bound to the transition metal centre are referred to as “ligands”.

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The blue row are molecules that are overall neutral themselves and the green are anionic ligands which are good for transition metals because they are electropositive The bonding of ligands to a metal is a Lewis acid-Lewis base interaction A Lewis acid is an electron pair acceptor, and a Lewis base is an electron pair donor A lone pair donates itself to an electropositive transition metal centre

Denticity Bidentate - “Denticity” refers to how many “teeth” the ligand has in order to “bite” into the metal centre. - If a ligand has one “tooth” it is referred to as being “monod entate”. - There are also many examples of“polydentate” ligands spanning from “bidentate” to “octa dentate”. Chelate Ring - Polydentate ligands usually make a ring - When multidentate ligands make a ring and bind a central metal from more than one point on the ligand, this is known as a “chelate” ring. - Chelate means “claw” and thus two or more donor points on a dentate ligand are acting like a claw on the metal (this makes exceptionally stable structures) - Polydentate ligands do not always need to make a chelate ring. - Ethylene diamine can be a chelating ligands, each nitrogen could separately bind to individual metals, which is called bridging, or you could also have terminal Isomers

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Isomers are compounds with the same formula but a different arrangement of atoms in the molecule and different properties They will have different properties because different atoms are bonded to each other Linkage isomers are also known as structural isomers and constitutional isomers.

Naming a Complex

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Hexa indicates how many of which type of ligand is around the central metal The ligand is then indicated followed by the metal The oxidation state is then indicated, in this case it is three Now consider the formula Complexes are enclosed in square brackets Metal comes first, then an alphabetical arrangement of the ligands (enclosed in circle brackets), then the number of ligands, then the oxidation state/charge outside the square brackets Counter ion(s) balance out the complex ion charge

Looking at the formula, the oxidation state is implied, it has a 3+ charge because it has 3 counter anions of Cl

Charge of a Complex - The charge on a complex is the sum of the charge of the metal atom and the ligands. - This gives you the overall charge of the complex. Coordination Isomer - Coordination isomers have the same chemical formula, different structural formulas - There is charge balance in these complexes - For example, you can switch central atoms giving you the hexamine chromium complex, and the tris oxalato cobalt complex Ionization Isomers - Transition metal complexes have a charge, and with that charge they need counter ions to balance out and be neutral - If your counter ions are bromide, the bromides could change places with the chlorides - Same chemical formula, different atoms

Coordination Number and Stereochemistry

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Coordination Number is simply how many ligating atoms are bound to the central metal. Stereochemistry tells us how the atoms around the metal are arranged in space. Coordination Number 1 has linear geometry and can be cationic, anionic, or neutral Coordination number 2 and 3 are not too common, they have trigonal planar geometry Coordination number 4 can be tetrahedral (109 deg. bond angles) or square planar, this can be neutral or anionic, as well as cis or trans Coordination Number 5 can be trigonal bipyramidal and square based pyramidal (can be chiral) Coordination Number 6 usually has octahedral geometry

Fac/Mer - If there is an arc shape, there is a meridional complex - If you put the chlorines to fill a face, there is a facial complex Metal Carbonyl Complex - These have a carbon monoxide bound to a metal centre (4 5 and 6 coordinate metal centres) - They are called organometallic, because they have a direct carbon metal bond Mond Process - He discovered that by making a nickel carbonyl complex and subject it to high temperatures, you get highly concentrated nickel, and 4 carbon monoxides that can be recycled - The nickel carbonyl complex is extremely poisonous Hemoglobin - Hemoglobin’s a coordination complex w/ iron as the central metal, and the ligand porophine - When the iron doesn't have an oxygen, it’s a square based pyramidal geometry - When oxygen is included, there’s an octahedral iron porphyrin complex w/ oxygen as a ligand - The process of taking oxygen on requires electron transfer and iron is oxidized fr 2+ to 3+ Why is CO Poisonous - CO binds much, much more strongly to a metal than O2. - The binding of CO to your hemoglobin is irreversible under physiological conditions, which is why CO is so poisonous - The bond is so strong because transition metals have a lot of valence electrons - There is a metal carbon double bond which is very strong (referred to metal ligand back bonding) Colours - The origin of the colors are dependent on several things: - (1) the metal itself; (2)the oxidation state of the metal; (3) the number of ligands bound to the metal (coordination #); (4) the types of ligands (i.e.stronger or weaker electron donors) - These all have a profound impact on the observed color....