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CHEM 110 LECTURE 2 nov 6th 2009 Amethyst SiO2, purple variety of quartz, but colour is provided by Mn Emerald colour provided by Cr Metal containing compounds play an important role in pigments in gemstones, paint, photography and act as catalysts (Pt, Pd, Mn) LIFE: Fe, Co, Cu iron essential in transport and storage of oxygen Copper and iron have a crucial role in respiration Zinc found in more than 150 biomolecules Cobalt found in vitamin B12 Transition metals are in their ionic form and in a variety of oxidation states Oxidation state: number of electrons lost (LEO THE LION SAYS GER) Remember: electrons are lost from 4s before 3d Electro negativity: power of nucleus to attract electrons It is too difficult to remove d electrons as they become lower in energy as the nuclear charge increases CoCl3 + 6ammonia = a yellow compound But if both are stable compounds why would they form a complex? Also, CoCl3 with 5 ammonia, or 4 ammonia = purple, green or violet compounds Coordination compound: transition metal (lewis acid) with its attached ligands (lewis base) Lewis aid accepts electrons (CoCl3, lewis base donates electrons Metal-ligand bond bond between lewis acid and lewis base Write down electron configurations and see which electrons are fair, then see if metal ligands will create a stable molecule Coordination number = number of coordinate covalent bonds ( or number of ligands DIRECTLY bound to the central transition metal ion) [Co(NH3)6]Cl3 Inside the bracket is ligands bound to central ion (6 in this case) Outside the bracket is the counter ions that do NOT count towards coordination number Coordination number varies from 2 to 8 but depends on a number of factors including electron configuration of the transition metal ion CHEM 110 LECTURE 3 nov 9th 2009 Neutral ligands: H20, NH3, CO, NO (aqua, amine, carbonyl, nitrosyl) For eg. NH3 uses its lone pair of electrons to bind to a transition metal Proper names and terminology – with ligands that end with ide, you must remove the ide and add “o” Flouro, chloro, bromo etc. Bidentate ( two teeth ligand) has two sites (two electron pairs) for attachment and so can form two bonds with the metal ion Bi and poly-dendate ligands surround the metal and act as a clawand form very stable complex ions with most metal ions o Used as a scavenger to remove toxic heavy metals from the body CH 24.3 NOMENCLATURE FOR COORDINATION COMPONDS Most comlex ions are charged o Name cation first, anion second o Name ligands first in alphabetic order, and then metal center last The oxidation state of the metal is given with ROMAN NUMERALS Charge on complex ion – charge on ligands = oxidation state charge NAMING METAL COMPLEXES ON SLIDE LEARN THAT CHEM 110 LECTURE nov 11th 2009 Isomers are molecules with the same composition but different arrangement of atons Stereoisomers differ in arrangement of ligands about metal o Geometric isomers o Optical isomers Structural isomers differ in atoms bonded to metal o Cooridination isomers o Linkage isomers - Coordination isomers: compounds in which the composition within the coordination sphere - Where the metal is placed affects whether it is a coordination isomer - First must determine oxidation state of metal in anion and cation - Name cation first then anion, then starting with ligands within each - Ionization isomers are compounds in which the counter ion is different differences in coordination sphere and in the counter ion (so one has a different anion in the solution) e.g. [CO(NH3)5Cl]Br and [CO(NH3)5Br]Cl - Linkage isomers are compounds in which the donor atom of the ligands is different how the ligands are linked to the transition metal ion e.g. thiocyaniate ion where the ligand can bind to sulfur OR nitrogen - However linkage exists only when there is a choice in the ligands, (if ligand can bond to a metal atom in more than one way) - Geometrical isomers differs in the relative orientation of ligands around the metal (cis ligands beside each other, trans opposite each other) - Cis and trans have different properties e.g. cis-platin is an anti cancer drug, but trans-platin has no cancer fighting properties - Because of different spatial arrangements in ligands, this leads to different physical properties such as colours, melting point, etc. - Optical isomers (relate to light) way they react to light is different, however compounds are same molecular formula, but are nonsuperimposable mirror images CHEM LECTURE NOV 27TH 2009 - Graphite sheets held together by van der waals forces which explains the delocalized electrons free to move anywhere, which means graphite can easily conduct electricity - However in a diamond, all the electrons are tied up which means its an insulator - Sheets of graphite are held together by weak van der waals forces which explains why they can slip and slide on top of each other (explaining its properties and uses as a solid lubricant) - Differences in properties of diamond vs graphite are based on their intramolecular forces - Simulating red giant star conditions in a lab: includes the vaporization of carbon from solid graphite using a mass spectrometer to look at mass of carbon (crucial mass in this experiment was 720) - Discovered that mass came from C60, called a buckyball - Fullerenes are large carbon-cage molecules (buckyball) but others are C70, C76, C84 - Fullerenes exist in interstellar dust (space between stars) - Buckyballs have the ability to block HIV virus from attacking healthy cells under certain conditions - Carbon nanotubes: molecular scale tubes of graphitic carbon o Bonding is sp2 similar with each atom joined to three neighbours as in graphite, which can therefore be considered rolled up grapheme sheets o Stiff and strong fibers and have strong electronic properties o Ideal for reinforced composites, nanoelectromechanical systems - Ionic solids: made up of oppositely charged ions that interact by coulombic forces between them - A crystal is defined as a lattice describing the way ions are repeated in space - A unit cell is a subset of the lattice containing enough information to completely understand lattice -