Transition metal Transition metal chemistrychemistry

Coordination compounds – ligands and thingsCoordination compounds – ligands and thingsCoordinate covalent bonds and ligandsCoordinate covalent bonds and ligandsNomenclatureNomenclatureIsomerismIsomerismSpectroscopySpectroscopyElectronic structureElectronic structure

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)

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

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

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

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

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

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

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

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

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.

What’s in a nameWhat’s in a name

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

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

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

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

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

--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