Chapter 21. Transition Metals and Coordination Chemistry

Transcription

1 Chapter 21. Transitin Metals and Crdinatin Chemistry

2 The Transitin Metals: A Survey General Prperties Main Grup Elements Main Grup Elements similar prperties changing prperties similar prperties d-blck transtin elecments f-blck transtin elecments Transitin Metals Key reasn: Last electrns added are inner electrns (d s, f s). These electrns d and f electrns cannt participate as easily in bnding as can the valence s and p electrns. But despite their many similarities, the transitin metals d vary cnsiderably in many ways. Ex) mp f W = 3422 C, mp f Hg = C

3 The Transitin Metals: A Survey General Prperties (Transitin Metal Ins) Mre than ne xidatin state is ften fund. Frming cmplex ins, species where the transitin metal in is surrunded by a certain number f ligands (Lewis bases). L 4 L 3 L 1 L 2 Several crdinatin numbers, number f ligands attached t a metal in, and gemetries exist. Sc Ti V Cr Mn Fe C i Cu Zn Ex) Inic cmpunds : FeCl 2, FeCl Cmplex ins: C(H 2 ) 2+ 6 C(H 3 ) H H H 2 H 2 H +5 Cu 3 Cu H 3 H 2 H 2 H 3 +6 : mst cmmn H 2 +7

4 The Transitin Metals: A Survey General Prperties (Transitin Metal Ins) Mst cmpunds cntaining transitin metal ins are clred because the ins can absrb visible light f specific wavelength is ften fund. Wulfenite (PbM 4 ) Rhdchrsite (MnC 3 ) Ruby Pure (Al 2 3 : clrless) Impurity (Cr 3+, < 1%) absrptin : vilet and green emissin : red C(H 2 ) 2+ 6 Cr(H 2 ) 3+ 6 i(h 2 ) 2+ 6 Mn(H 2 ) 2+ 6 Fe(H 2 ) 3+ 6 Many cmpunds cntaining transitin metal ins are paramagnetic (they cntain unpaired electrns) EPR Cu 2+ Mn 2+

5 Electrn Cnfiguratin The Transitin Metals: A Survey [Ar] = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 3d 4s 3d 4s 3d 4s 3d Ti 3+ => [Ar]3d 1 Mn 2+ => [Ar]3d 5 Fe 3+ => [Ar]3d 5 Cu 2+ => [Ar]3d 9 Zn 2+ => [Ar]3d 10

6 xidatin States, Inizatin Energies The Transitin Metals: A Survey xidatin States Sc Ti V Cr Mn Fe C i Cu Zn : mst cmmn Inizatin Energy Remving f d-electrn M 2+ (g) M 3+ (g) + e - Mre rapid decrease f energy level f 3d Remving f s r d-electrn M(g) M + (g) + e - Increase f nuclear charge Decrease f energy level f 3d

7 Reductin Ptentials The Transitin Metals: A Survey E 0 (M n+ + ne - M) E 0 (2H + + 2e - H 2 ) = 0 In acidic slutin, M(s) + 2H + (aq) H 2 (g) + M 2+ (aq) except fr Cu

8 The 4d and 5d Transitin Series The Transitin Metals: A Survey 3d 4d 5d Atmic radii Lanthanide cntractin: 4f shielding effect is nt big. => 5d cntracts. uclear charge

9 Scandium (Sc): In => nly +3 Titanium (Ti): The First-Rw Transitin Metals

10 The First-Rw Transitin Metals

11 Crdinatin Cmpunds Crdinatin cumpunds typically cnsists f a cmplex in and cunter ins (anins r catins as needed t prduce a neutral cmpund). Cmplex ins: species where the transitin metal in is surrunded by a certain number f ligands (Lewis bases). L 4 L 3 L 1 L 2 H 2 [C(H 3 ) 5 Cl]Cl 2 (s) C(H 3 ) 5 Cl 2+ (aq) + 2Cl - (aq) cmplex in cunter in (Cl - ) C 3+, Cl - => [] 2+ Tw characteristics f crdinatin cmpunds (cmplex ins): xidatin number f the transitin metal and crdinatin number (and gemetry)

12 Crdinatin Cmpunds Crdinatin umber: number f ligands attached t a metal (typically 2 ~8)

13 Crdinatin Cmpunds Ligand: A neutral mlecule r in having a lne electrn pair that can be used t frm a bnd t a metal in (Lewis base). crdinate cvalent bnd: metal-ligand bnd mndentate ligand: ne bnd t metal in bidentate ligand: tw bnds t metal in plydentate ligand: can frm mre than tw bnds t a metal in chelate ligand: bidentate, plydentate ligands ambidentate ligand: bnding thrugh different atms f a same ligand

14 Crdinatin Cmpunds menclatures [C(H 3 ) 5 Cl]Cl 2 1. As with any inic cmpund, the catin is named befre the anin. 국어이름에서는반대 [ Chlride ges last.] 2. In naming a cmplex in, the ligands are named befre the metal in. ["H 3, Cl - " named befre cbalt] 3. Fr ligand, an is added t the rt name f an anin (Table 21.14). Fr neutral ligands the name f the mlecule is used, with exceptins f Table ["Cl - = chlr", "H 3 = ammine"] 4. The prefixes di-, tri-, tetra-, penta-, and hexa- are used t dente the number f simple ligands.the prefix bis-, tris-, tetrakis-, and s n are used fr the ligands that already cntain di-, tri-, etc. [pentaammine] 5. The xidatin state f the central metal in is designated by a Rman numeral in parenthesis. [cbalt(iii)] 6. When mre than ne type f ligand is present, they are named alphabetically. [pentaamminechlr] 7. If the cmplex in has a negative charge, the suffix -ate ( 산 ) is added t the name f the metal with exceptins f Table [pentaamminechlrcbalt (III) chlride] Ex) K 3 Fe(C) 6 ptassium hexacyanferrate(iii) [Fe(en) 2 ( 2 ) 2 ] 2 S 4 철산구리산납산은산금산주석산 bis(ethylenediamine)dinitrirn(iii) sulfate triamminebrmplatinum(ii) chlride [Pt(H 3 ) 3 Br]Cl ptassium hexaflurcbaltate(iii) K 3 [CF 6 ]

15 Ismerism When tw r mre species have the same frmula but different prperties, they are said t be ismers. Crdinatin ismerism: The cmpsitin f the cmplex in varies. [Cr(H 3 ) 5 S 4 ]Br and [Cr(H 3 ) 5 Br]S 4 Linkage ismerism: Same cmplex in structure but pint f attachment f at least ne f the ligands differs. [C(H 3 ) 4 ( 2 )Cl]Cl tetraamminechlrnitrcbalt(iii) chlride [C(H 3 ) 4 ()Cl]Cl tetraamminechlrnitritcbalt(iii) chlride Gemetrical ismerism (cis-trans): Atms r grups f atms can assume different psitins arund a rigid ring. cis-pt(h 3 ) 2 Cl 2 trans-pt(h 3 ) 2 Cl 2 trans-c(h 3 ) 4 Cl 2 + cis-c(h 3 ) 4 Cl 2 +

16 Ismerism ptical ismerism: the ismers have ppsite effects n plane-plarized light. early 19C At his age f 26, he first realized that ptical activity is exhibited by mlecules that have nn-superimpsable mirr images. said t be chiral, called enantimers Luis Pateur ( ) ne f the ismers dextrrtatry (d) the ther levrtatry (l) mixture f the tw : racemic mixture, when mixed rati is 1:1, n ptical activity

17 Ismerism ptical ismerism: the ismers have ppsite effects n plane-plarized light. C(H 3 )Br(en) 2 2+ H 3 gemetrical C Br trans C Br H 3 cis C(en) 3 3+ ptical C Br H 3 H 3 C Br C(en) 2 Cl 2 + trans cis

18 Bnding In Cmplex Ins: The Lcalized Electrn Mdel Bnding Theries f Cmplex Ins : Valence bnd thery (Lcalized electrn bnding mdel) Crystal field thery Ligand field thery (Delcalized electrn bnding mdel) Cvalent Bnd Lcalized electrn bnding mdels Lewis dt structure VSEPR (Valence shell electrn pair repulsin) Valence bnd thery (hybridizatin) Delcalized electrn bnding mdel Mlecular rbital (M) thery Review f Chapters 8 amd 9 Central idea: Frmatin f hybride atmic rbitals that are used t share electrn pairs t frm s bnd between atms

19 Bnding In Cmplex Ins: The Lcalized Electrn Mdel Fr cmplex ins Cvalent Bnd Lcalized electrn bnding mdels Lewis dt structure VSEPR (Valence shell electrn pair repulsin) Valence bnd thery (hybridizatin) 1. VSEPR mdel smetimes wrks. But it generally des nt wrk 2. The interactin between a metal in and a ligand can be viewed as a Lewis acid-base reactin with the ligand dnating a lne pair f electrns t an empty rbital f the metal in t frm a crdinate cvalent bnd. M L M L empty metal in hybrid rbital lne pair n the ligand in a hybrid atmic rbital crdinate cvalent bnd C(H 3 ) 6 + d 2 sp 3 sp 3 dsp 2 sp Thugh the lcalized electrn bnding mdel imprved ur understanding f metal-ligand bndings, it des nt explain well many imprtant prperties f metal ins, such as magnetism and clrs. S usually thesedays we d nt use it fr the cmplex ins.

20 The Crystal Field Mdel Crystal field mdel fcuses n the energies f the d rbitals t explain the magnetic prperties and clr f cmplex ins. Assumptin 1. Ligands are negative pint charge. 2. Metal-ligand bnding is entirely inic. ctahedral Cmplexes e g (d z2, d x2-y2 ) T derive the energy splittings f the d-rbital in cmplex ins. E t 2g (d xy, d yz, d xz ) d Free metal in 3d rbital energies 3d rbital energy splittings in ctahedral field 3d rbitals 3d rbitals in ctahedral field

21 ctahedral Cmplexes (magnetic prperties) The Crystal Field Mdel C 3+ (3d 6 ) = ligand field splitting parameter (lw-spin, S = 0, diamagnetic) (high-spin, S = 2, paramagnetic) Spectrchemical Series fr Ligands C > C - > PPh 3 > 2- > phen > bipy > en > H 3 > py > CH 3 C > CS - > H 2 > C > H - > RC 2- > F - > 3- > 3- > Cl - > SC - > S 2- > Br - > I- π acceptr (strng field ligand) π dnr (weak field ligand) Spectrchemical Series fr Metal Ins (x #,ᇫ ), (dwn a grup in peridic table, ᇫ ) Pt 4+ > Ir 3+ > Pd 4+ > Ru 3+ > Rh 3+ > M 3+ > Mn 4+ > C 3+ > Fe 3+ > V 2+ > Fe 2+ > C 2+ > i 2+ > Mn 2+

22 ctahedral Cmplexes (magnetic prperties) The Crystal Field Mdel Ex) Fe(C) 6 3- has ne unpaired electrn. C - is strng-field r weak-field ligand? Fe 3+ (3d 5 ) e g e g t 2g t 2g weak-field (high-spin, S=5/2, paramagnetic) Ex) Hw many unpaired electrns in Cr(C) 6 4-? strng-field (lw-spin, S=1/2, paramagnetic) Cr 2+ (3d 4 ) C - : strng-field ligand e g e g Ex) S f Cu(H 2 ) 6 2+? Cu 2+ (3d 9 ) S = 1/2 t 2g weak-field (high-spin, S=2, paramagnetic) t 2g strng-field (lw-spin, S=1, paramagnetic)

23 ctahedral Cmplexes (clrs) The Crystal Field Mdel

24 ctahedral Cmplexes (clrs) The Crystal Field Mdel E E = hn = hc/l

25 ther Crdinatin Gemetries Tetrahedral cmplexes The Crystal Field Mdel e g (d z2, d x2-y2 ) E t 2 (d xy, d yz, d xz ) t 2g e (d (d xy z2,, d yz x2-y2, d xz )) tet (4/9) ct d Free metal in 3d rbital energies 3d rbital energy splittings in tetrahedral ctahedral field All tetrahedral cmplexes are weak-field cases (high-spin).

26 ther Crdinatin Gemetries The Crystal Field Mdel Square-planar cmplexes Linear cmplexes d x2-y2 b 1g e g d x2-y2 b 1g 1 t 2 e d xy, d yz, d zx t d z2, d x2-y2 d Unifrm Field d z2, d x2-y2 d xy, d yz, d zx d z2 d xy a 1g b 2g d xy 2 d z2 3 b 2g a 1g Tetrahedral (T d ) t 2g e g d ctahedral ( h ) yz, d zx Tetragnal elngatin (D 4h ) e g d yz, d zx Square-planar (D 4h )

27 Bnding In Cmplex Ins: The Lcalized Electrn Mdel Bnding Theries f Cmplex Ins : Valence bnd thery (Lcalized electrn bnding mdel) Crystal field thery Ligand field thery (Delcalized electrn bnding mdel) has nt talked abut bnding frntier rbitals electrns frm d-rbitals same splitting pattern and d-rbital cnfiguratin as in CFT Higher Class electrns frm ligands M ML 6 L 6

28 The Bilgical Imprtance f Crdinatin Cmplexes Rles f metals in bilgy electrn transprt, xygen strage, xygen transprt, xidatin-reductin catalysis, metal in strage and transprt...

29 The Bilgical Imprtance f Crdinatin Cmplexes Hw t get energy in ur bdy? 2 : surce f energy - cmbustin (burning gasline in autmbiles) - xidatin f carbhydrates, prteins, fats thrugh respiratry chain (mammal) Air heme = Fe + prphyrin 2 transprt prtein 2 strage and transprt 2 + nutrients Hemglbin Hb(aq) (g) Hb( 2 ) 4 (aq) Hemglbin xyhemglbin e - transfer (xidatin f nutrients) Myglbin cytchrmes (Heme prteins)

30 The Bilgical Imprtance f Crdinatin Cmplexes thers Chlrphyll itrgenase Cisplatin

31 Metallurgy and Irn and Steel Prductin Metallalurgy 1. Mining 2. Pretreatment f the re 3. Reductin t the free metal 4. Purificatin f the metal (refining) 5. Allying remving C 2 FeC 3 (s) heat Fe(s) +C 2 (g) 4Fe(s) + 2 (g) 2F 2 3 (s) 3Fe 2 3 (s) + C(s) Fe 3 4 (s)+c(g)