Transition metal chemistry
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Transcript of Transition metal chemistry
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Transition metal Transition metal chemistrychemistry
Coordination compounds – ligands and thingsCoordination compounds – ligands and thingsCoordinate covalent bonds and ligandsCoordinate covalent bonds and ligandsNomenclatureNomenclatureIsomerismIsomerismSpectroscopySpectroscopyElectronic structureElectronic structure
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Coordinate covalent bondCoordinate covalent bond Lewis acid/base chemistryLewis acid/base chemistry Lone pair on water (base)Lone pair on water (base) Vacancy on FeVacancy on Fe2+2+ (acid) (acid)
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Positive, neutral, negativePositive, neutral, negative The complex can be an The complex can be an
ion that forms part of a ion that forms part of a neutral compound - neutral compound - square brackets square brackets delineate the complexdelineate the complex
Or may exist as a Or may exist as a standalone neutral standalone neutral compound (no square compound (no square brackets)brackets)
223 ClNHPt
263NHNi
36CNFe
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Things to considerThings to consider Coordination number – the number of ligands Coordination number – the number of ligands
around the central ionaround the central ion Geometry – the shape of the complexGeometry – the shape of the complex Much greater variety and complexity Much greater variety and complexity
compared with the geometry of covalent compared with the geometry of covalent molecules of the representative elementsmolecules of the representative elements
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Coordination Coordination numbernumber
ComplexComplex
22 [Ag(NH[Ag(NH33))22]]++, [CuCl, [CuCl22]]--
33 [HgI[HgI33]]--
44 [Zn(NH[Zn(NH33))44]]2+2+, , [Ni(CN)[Ni(CN)44]]2-2-
55 [Ni(CN)[Ni(CN)55]]--, Fe(CO), Fe(CO)55
66 [Cr(H[Cr(H22O)O)66]]3+3+, , [Fe(CN)[Fe(CN)66]]3-3-
77 [ZrF[ZrF77]]3-3-
88 [Mo(CN)[Mo(CN)88]]4-4-
Examples of complexes with Examples of complexes with different coordination numbersdifferent coordination numbers
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Geometry - preludeGeometry - prelude Rules for determining geometry are more involved than the Rules for determining geometry are more involved than the
simple VSEPR approach that works well with covalent simple VSEPR approach that works well with covalent compoundscompounds
Note: Note: samesame composition may adopt composition may adopt differentdifferent geometries geometries Will be dealt with using ligand-field theory Will be dealt with using ligand-field theory
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Things to knowThings to know Writing the correct formulaWriting the correct formula
Determining oxidation state on the central atomDetermining oxidation state on the central atom Complex charge - Sum of anion charges = o.s.Complex charge - Sum of anion charges = o.s.
)()( nMnm XLM
Square bracket
Number of neutral ligands
Number of anion ligands
Overall charge
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Ligands – entities with teethLigands – entities with teeth Must contain a lone electron pairMust contain a lone electron pair Classify the ligands according to the number Classify the ligands according to the number
of available pairsof available pairs Monodentate – one pairMonodentate – one pair Bidentate – two pairsBidentate – two pairs Polydentate – many pairsPolydentate – many pairs
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Anion Anion ligandligand
NameName Neutral Neutral ligandligand
NameName
BromideBromide BromoBromo AmmoniaAmmonia AmmineAmmine
CarbonateCarbonate CarbonatoCarbonato WaterWater AquaAqua
ChlorideChloride ChloroChloro Carbon Carbon monoxidemonoxide
CarbonylCarbonyl
CyanideCyanide CyanoCyano Ethylene Ethylene diaminediamine
Ethylene diamineEthylene diamine
FluorideFluoride FluoroFluoro
HydroxideHydroxide HydroxoHydroxo
OxalateOxalate OxalatoOxalato
ThiocyanateThiocyanate Thiocyanato/Thiocyanato/IsothiocyanatoIsothiocyanato
Common ligands and names in Common ligands and names in complex ionscomplex ions
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Chelating – ligands with clawsChelating – ligands with claws Ligands with greater than one lone pair can form Ligands with greater than one lone pair can form
more than one bond to a single metal ionmore than one bond to a single metal ion Ethylene diamine (Ethylene diamine (enen)– tridentate)– tridentate EDTAEDTA - hexadentate - hexadentate
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Important biological entitiesImportant biological entities (a) The structure of the porphine molecule. Loss of the two NH protons (a) The structure of the porphine molecule. Loss of the two NH protons
gives a planar, tetradentate 2– ligand that can bond to a metal cation. The gives a planar, tetradentate 2– ligand that can bond to a metal cation. The porphyrins are derivatives of porphine in which the peripheral H atoms are porphyrins are derivatives of porphine in which the peripheral H atoms are replaced by various substituent groups. (b) Schematic of the planar heme replaced by various substituent groups. (b) Schematic of the planar heme group, the attached protein chain, and the bound Ogroup, the attached protein chain, and the bound O22 molecule in molecule in oxyhemoglobin and oxymyoglobin. The Fe(II) ion has a six-coordinate, oxyhemoglobin and oxymyoglobin. The Fe(II) ion has a six-coordinate, octahedral environment, and the Ooctahedral environment, and the O22 acts as a monodentate ligand. acts as a monodentate ligand.
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What’s in a nameWhat’s in a name
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Rules, rules, rulesRules, rules, rules
1.1. If the compound is a salt, naming is as for If the compound is a salt, naming is as for common salts: cation first and then anioncommon salts: cation first and then anion
Potassium hexacyanoferrate(III)Potassium hexacyanoferrate(III)
63 CNFeK
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Complex ion or neutral complexComplex ion or neutral complex
2.2. Ligands first then metalLigands first then metal Endings are the thingEndings are the thing
Anionic ligands end in Anionic ligands end in –o–o -ide -ide → -o; -ate → -ato→ -o; -ate → -ato Neutral ligands have normal names except…Neutral ligands have normal names except… HH22O (aqua), NHO (aqua), NH3 3 (ammine), CO (carbonyl)(ammine), CO (carbonyl)
One word: nospacebetweenligandandmetalOne word: nospacebetweenligandandmetalDiamminedichloroplatinum(II)Diamminedichloroplatinum(II)
223 ClNHPt
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More than one ligandMore than one ligand
3.3. Indicate number of ligands by prefixes: Indicate number of ligands by prefixes: di-, di-, tri-, tri-, etc.etc.
Ligands are listed in alphabetical orderLigands are listed in alphabetical orderTetraaquadichlorochromium(III) chlorideTetraaquadichlorochromium(III) chloride
ClClOHCr 242
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It’s all Greek to meIt’s all Greek to me
4.4. If the ligand name contains a Greek prefix If the ligand name contains a Greek prefix (ethylene(ethylenedidiamine), the ligand name is in amine), the ligand name is in parantheses and use an alternative prefix: parantheses and use an alternative prefix: bis-bis-(2), (2), tris-tris-(3), (3), tetrakistetrakis(4)(4)Tris(ethylenediamine)cobalt(III) chlorideTris(ethylenediamine)cobalt(III) chloride
33 ClenCo
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Roman numeralsRoman numerals
5.5. Roman numeral in parantheses to indicate Roman numeral in parantheses to indicate oxidation state of metal in situation where oxidation state of metal in situation where the o.s. is variablethe o.s. is variable
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--ate ate crimescrimes
6.6. --ate ate is the conventional ending for the metal in an is the conventional ending for the metal in an anionic complexanionic complex
Check table for exact wordingCheck table for exact wording
MetalMetal Anion Anion NameName
MetalMetal Anion Anion NameName
AluminiumAluminium AluminateAluminate IronIron FerrateFerrate
ChromiumChromium ChromateChromate ManganeseManganese ManganateManganate
CobaltCobalt CobaltateCobaltate NickelNickel NickelateNickelate
CopperCopper CuprateCuprate PlatinumPlatinum PlatinatePlatinate
GoldGold AurateAurate ZincZinc ZincateZincate