Chemistry445lecture6complexesofmetalionsandnomenclature

8/19/2019 Chemistry445lecture6complexesofmetalionsandnomenclature

1/22

Complexes of metal ions and

nomenclature for inorganiccompounds

ammonia ligands

blue = nitrogen donor atom

white =hydrogen atom

Cobalt(III) ion

[Co(NH 3)6]3+


2/22

Complexes of metal ions.

Prior to the work of Werner oncoordination complexes,formulated at the time asCoCl !"#$ , for example, therewas no understanding of why

the six ammonia moleculeswere so strongly bound in thiscompound! Werner showedthat the ammonia moleculeswere in fact chemically bound

to the cobalt, and that the threeCl% ions were present only toact as counter%ions to the &charge on the 'Co(#$ )" & cation!

Alfred Werner (1866-1919)

Nobel prize ! 3 for "is #or$

on Coordination compounds


3/22

'Co(#$ )" & 'Co(#$ )) Cl *& 'Co(#$ ) Cl

Werner proposed that Co(III) (tri+alent cobalt) had a coordinationnumber of six, which could be satisfied by six ammonias in a-, fi+e

ammonias and a Cl % in b-, and three ammonias and three Cl % in c-!$is theory explained why conducti+ity showed that in solution a-was a & cation, b- was a *& cation, and c- was neutral! .hemolecules or ions coordinated to the Co(III) are called ligands, fromthe /atin ligare - meaning to 0oin-! .he coordination geometry of the

Co(III) is octahedral, which means that the six ligands are placedaround the Co(III) at the corners of an octahedron!

(a) (b) (c)


4/22

1ome complexes of metal ions2

Cobalt water molecule

*&

nickel

cyanide

ion

*& *%

nickel

ammonia

'Co($ *3) " *& '#i(#$ )" *& '#i(C#) 4 *%

5 complex is written such that e+erything inside the s6uare brackets isa ligand chemically bonded to the metal ion! 7+erything outside the brackets

is a counter%ion or something simply present in the crystal lattice! .hus, wemight ha+e 'Co($ *3) " (#3 )* where the #3 % ions are counter%ions!

$exaa6uacobalt(II) hexamminenickel(II) tetracyanonickelate(II)

C #

% #


5/22

&ormal %xidation 'tate

"e formal oxidation state of metal ionsin t"eir complexes is determined b*ascribing formal c"arges to all ligands#"ic" correspond to t"ose t"e*possess as t"e free molecules or ions

Neutral NH 3 H, % C% -H3 (CH3), 'nionic %H / &/ Cl/ 0r / 1/ CN/ 'CN /

Cationic N% +


6/22

2xamples of oxidation states[Co(NH 3)6]3+ Co(111)"examminecobalt(111)

4 3[&e(CN) 6] &e(111)potassium "exac*anoferrate(111)

[Co(NH 3)5Cl , ]Cl Co(111)tetrammiinedic"lorocobalt(111) c"loride

[&eN%(NH 3) ]Cl 3 &e(11)pentamminenitros*liron(11) c"loride

[Cr(C%) 6] Cr(7)"exacarbon*lc"romium(%)

4[8(C%) 6] 8(/1)potassium "exacarbon*l9anadate(/1)

[:n(N%) 3C%] :n(/111)trinitros*lcarbon*lmanganese(/111)


7/22

1dentif*ing #"ic" are ligands

1n t"e formula for a complex e9er*t"ing inside t"e

s;uare brac$ets ( blue in formula belo#) iscoordinated to t"e metal ion e9er*t"ing outside(red ) is a counterion or a lattice molecule.


8/22

Naming of ligands in complexesNeutral ligands

When naming a complex, the ligands are indicated bynames as follows2

Neutral ligands NH 3 ammineH, % a;uaC% carbon*l

.he number of each type of ligand present is indicated bythe /atin prefixes di%, tri%, tetra%, penta%, hexa%, hepta%,octa%, nona%, and deca%2

[Co(NH 3)6]Cl 3 "examminecobalt(111) c"loride[=a(H , %)! ](N% 3)3 nona/a;ua lant"anum(111)nitrate

4 , [ i(C%) 6] potassium "exacarbon*ltitanate(/11)


9/22

nionic ligands .o indicate that they are anions, ligandsin complexes are gi+en an o- ending2 fluoro, chloro, bromo,iodo, hydroxo, cyano, sulfato, nitro, etc! If the o+erallcharge on the complex is negati+e, the metal ion is gi+enan ate- ending to indicate this2

8 '9e(C#) " = potassium hexacyan oferrate(III)or potassium hexacyan oiron(III)

8 4 '9e(C#) " = potassium hexacyan oferrate(II)#a '5l9 " = sodium hexafluor oaluminate(III)'Co(#$ ) 9 = triamminetrifluor ocobalt(III)

Naming of ligands in complexes anionicligands


10/22

Nomenclature of complexes

Cations including complex cations come first anionsincluding complex anions come second

[Co(NH 3 )6 ]Cl 3 "exammine cobalt(111) c"lorideNa 3 [CrCl 6 ] sodium "exac"loroc"romate(111)[Ni(H , %)6 ]Cl , "exaa;uanic$el(11) c"loride4 3 [>"(CN) 6 ] potassium "exac*anor"odate(111)

[Co(NH 3 )6 ][Co(CN) 6 ] "examminecobalt(111)"exac*anocobaltate(111)


11/22

Naming more complex ligands

:an* ligands are more complex and "a9e more t"an one donoratom suc" as en (et"*lenediamine) bip* (, ,?/bip*rid*l) and acac(acet*acetonate) belo#


12/22

'ome cobalt(111) complexes of morecomplex ligands

NH ,

Co

NH ,

H , NH ,N

H , N NH ,

Co

NN

NN

N

N

Co%

%

%

%

%

%

CH 3

H3C

H3C

CH 3

CH 3

CH 3

.Cl 3 .(N% 3)3

tris(ethylenediamine) tris(*,*-%bipyridyl) tris(acetylacetonato)cobalt(III)chloride cobalt(III) nitrate cobalt(III)


13/22

N%:2NC= @>2. &ormulas of 'imple 1onic substances.

&or ionic compounds t"e cation (moreelectropositi9e element) s"ould al#a*sbe first. (4Cl Na , '). 1f se9eral cationsare present t"e* s"ould be listed inalp"abetical order follo#ed b* anionsin alp"abetical order (=i:gCl& , ). n

exception is t"e proton #"ic" is al#a*slisted last in t"e se;uence of cations(>bH& , ).


14/22

Nomenclature (contd.)

:!*! 'e;uence of atoms in formulas of

pol*atomic ions and molecules 2 &or pol*atomic species #it" a central atom

t"ese are generall* listed first follo#ed b* t"eattac"ed atoms in alp"abetical order ('% 5 ,/

CCl , H , -Cl 3% '% 3 /C&3 /'CN). n exceptionis t"e linear t"ioc*anate group (/'CN)#"ere t"e atoms are placed in t"e order in#"ic" t"e* occur in t"e t"ioc*anate ion/' C N


15/22

&ormulas and Names of Common substances.

cid Name Name of anion

HN%3 Nitric acid nitrate

H3-% 5 -"osp"oric acid p"osp"ate

H , '% 5 'ulfuric acid sulfate

HCl% 5 -erc"loric acid perc"lorate

HCl% 3 C"loric acid c"lorate

HCl% , C"lorous acid c"lorite

HCl% H*poc"lorous acid "*poc"loriteHCl H*droc"loric acid c"loride


16/22

C"emical Names

Names of t"e 2lements "ese originated#it" 0erzelius ( A 3) #"o de9eloped t"es*stem t"at t"e s*mbol for an element #ast"e first letter of its name e.g. & % N C 0. 1ft"ere #as more t"an one element #"osename started #it" t"e same letter t"en asecond lo#er/case letter #as added #"ic"#as usuall* t"e second letter of t"e name oft"e element. e.g. C for carbon but Ca CdCe Cf Cl Cm Co Cr Cs Cu. 0 for 0oronbut 0a 0e 0i 0$ 0r and so on.


17/22

Names of metallic elements *ou s"ould$no# (prett* muc" all of t"em)

H"*drogen

=i 0elit"ium ber*llium

Na :gsodium magnesium

4 Ca 'c i 8potassium calcium scandium titanium 9anadium

>b 'r B r Nbrubidium strontium *ttrium zirconium niobiuim

Cs 0a =a Hf acesium barium lant"anum "afnium tantalum


18/22

Names of metallic elements *ou s"ould$no# (continued)

Cr :n &e Co Ni Cu nc"romium manganese iron cobalt nic$el copper zinc

:o c >u >" -d g Cdmol*bdenum tec"netium rut"enium r"odium palladium sil9er cadmium

< >e %s 1r -t u Hgtungsten r"enium osmium iridium platinum gold mercur*

=ant"anides

=a Ce D. Ed DD. =ulant"anum cerium gadolinium lutetium

ctinides

c " D. @ Np -u mactinium t"orium uranium neptunium plutonium americium


19/22

Eeometrical 1somerism

cis %diamminedichloro trans %diamminedichloro% platinum(II) platinum(II)

c"loride-t

ammonia

-t

;eometrical isomers can exist with two identical ligands placednext to each ( cis ) or at :< > to each other ( trans )! 5gain, Werner-stheory could explain how two different complexes correspondingto '(#$ )*Cl*Pt could exist!


20/22

Cis and trans isomerism of octa"edral complexes

trans %'Co(#$ )4Cl* & cis %'Co(#$ )4Cl* &

(green) (+iolet)

5n important aspect of Werner-s theory was that it could explain howtwo compounds of identical formula, i!e! 'Co(#$ )4Cl* Cl, could existas two entirely different forms, which we now know to be the cis andtrans forms abo+e!

gree n= Cl


21/22

fac (facial ) and mer (meridional ) geometricalisomers of t"e [Co(NH 3)3Cl 3] complex

mer fac

mer- [Co(NH 3)Cl 3] fac /[Co(NH 3)Cl 3]


22/22

%ptical isomerism

Λ (lambda) form Δ (delta) form

.he tris(ethylenediamine)cobalt(III) complex exists as optical isomers!the Δ and Λ forms, which are non%superimposable mirror images of

each other! .his will be discussed further under group theory!

mirror plane

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Chemistry445lecture6complexesofmetalionsandnomenclature

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