04/21/2011 Organometallics Study Meeting H.Mitsunuma 1. Crystal field theory (CFT) and ligand field theory (LFT)

CFT: interaction between positively charged metal cation and negative charge on the non-bonding electrons of the ligand LFT: molecular orbital theory (back donation...etc) Octahedral (figure 9-1a) d-electrons closer to the ligands will have a higher energy than those further away which results in the d-orbitals splitting in energy.

ligand field splitting parameter ( 0): energy between eg orbital and t2g orbital 1) high oxidation state 2) 3d<4d<5d 3) spectrochemical series I-< Br-< S2-< SCN-< Cl-< N -,F-< (H N) CO, OH-< ox, O2-< H O< NCS-

Low spin: If 0 is large, then the lower energy orbitals(t2g) are completely filled before population of the higher orbitals(eg) High spin: If 0 is small enough then it is easier to put electrons into the higher energy orbitals than it is to put two into the same low-energy orbital, because of the repulsion resulting from matching two electrons in the same orbital 3 n ex) (t2g) (eg) (n= 1,2)

Tetrahedral (figure 9-1b), Square planar (figure 9-1c)

LFT (figure 9-3, 9-4) - - Cl , Br : lower 0 (figure 9-4 a) CO: higher 0 (figure 9-4 b)

2. Ligand metal complex hapticity formal chargeelectron donation metal complex hapticity formal chargeelectron donation MR alkyl 1 -1 2 6-arene 6 0 6 MH hydride 1 -1 2 M MX H 1 -1 2 halogen 1 -1 2 M M -hydride M OR alkoxide 1 -1 2 X 1 -1 4 M M -halogen O R acyl 1 -1 2 O 1 -1 4 M R M M -alkoxide O 1-alkenyl 1 -1 2 C -carbonyl 1 0 2 M M M R2 C -alkylidene 1 -2 4 1-allyl 1 -1 2 M M M O C 3-carbonyl 1 0 2 M R acetylide 1 -1 2 MMM R R C 3-alkylidine 1 -3 6 M carbene 1 0 2 MMM R R M carbene 1 -2 4 R

M carbyne 1 -3 6 M CO carbonyl 1 0 2

M 2-alkene 2 0 2

M 2-alkyne 2 0 2

M 3-allyl 3 -1 4

M 4-diene 4 0 4

5 -cyclo 5 -1 6 M pentadienyl 1 3. d-electron

9 2 (OC) Co Co(CO) Co(0): d = 9e Mo H Mo(IV): d = 2e 4 4 H - 4(CO): 4 x 2e = 8e 2(C5H5) : 2 x 6e = 12e 9 Co-Co: 1 x 2e = 2e 2H-: 2 x 2e = 4e Co(0), d , 18e Mo(IV), d2, 18e M(valency), [d-electron of M(0)] - [formal charge], [d-electron of metal] + [electron of ligand]

Early transition metal: smaller d-electron number (group 4, 5...) Late transition metal: larger d-electron number (group 9, 10...)

4. 18-electron rule Valence shells of transition metal consists of nine valence orbitals (s, p, d), which collectively can accommodate 18 electrons (same electron configuration as noble gas) either as nonbinding electron pairs or as bonding electron pairs. 18-electron complex: coordinatively saturated complex non-18-electron complex: coordinatively unsaturated complex

Violations to the 18-electron rule Octahedral Square planar [Co(H O) ]2+ (19e) V(CO) (17e) 2 2+6 6 [(C6H5)3P]2PdX2 (16e) [Ni(en)3] (20e) W(CH3)6 (12e) [(C6H5)3P]2Ir(CO)X (16e) late transition metal: small 0 early transition metal instability of dx2-y2 occupation of eg

5. -bonding ligand stable alkyl complexes W(CH ) Zr(CH C H ) Ti[CH C(CH ) ] 03 6 2 64 5 4 2 0 3 3 4 5.1 alkyl complex W(VI), d , 12e Zr(IV), d , 8e Ti(IV), d , 8e M-C bond: 130~300 kJmol-1 -hydride elimination

Cr L Pt 4 2 4 Fe Cr(IV), d2, 10e Fe(IV), d4, 12e Pt(II), d8, 16e synthesis of alkyl complexes

1) Metathetical exchange using a carbon nucleophile 3) Oxidative addition Me PR3 PR3 Ph3P CO Ph3P CO Cl Pt Cl 2 n-BuLi Ir + MeCl Ir + n-Bu Pt n-Bu Br PPh3 Br PPh3 PR Cl 3 PR3 8 Ir(I), d , 16e Ir(III), d8, 18e Pt(II), d8, 16e Pt(II), d8, 16e

2) Metal centered nucleophile 4) Insertion

PR3 PR3 Cl Pt H + CH =CH Cl Pt Et OC Fe- + Br OC Fe- 2 2 OC + OC Na PR3 PR3 8 8 Fe(0), d8, 18e Fe(II), d6, 18e Pt(II), d , 16e Pt(II), d , 16e

5.2 hydride complex M-H bond: 240~350 kJmol-1 synthesis of hydride complexes 1) Metal halide + reductant 3) Oxidative addition RuCl (PPh ) RuH (PPh ) 2 3 3 + NaBH4 + PPh3 2 3 4 IrCl(CO)(PPh3)2 + H2 IrH2Cl(CO)(PPh3)2 6 6 Ru(II), d , 16e Ru(II), d , 18e Ir(I), d8, 16e Ir(III), d6, 18e

2) Protonation RhCl(PPh3)3 + H2 RhH2Cl(PPh3)3 8 6 + + Rh(I), d , 16e Rh(III), d , 18e Cp2WH2 + H [Cp2WH3] W(IV), d2, 18e W(VI), d0, 18e - + [Co(CO4)] + H HCo(CO4) Co(-I), d10, 18e Co(I), d8, 18e 2 4) Ortho metallation, cyclo metallation 5) -hydride elimination

PMe2 RuCl (PPh ) + 2KOCH(CH ) RuH2(PPh3)4 + 2KCl+ 2 acetone PMe 2 3 4 3 2 W[P(CH ) ] W 3 6 6 3 3 6 H PMe Ru(II), d , 18e Ru(II), d , 18e 6 3 W(0), d , 18e PMe3 W(II), d4, 16e

Reactivity of hydride complex - . 1) H O 2) H 3- 3- R R OCHR2 2[HCo(CN5)] + 2[Co(CN5)] + H Cp2Zr Cp2Zr Cl Cl 7 0 Co(II), d6, 18e Co(II), d , 17e 0 Zr(IV), d , 16e Zr(IV), d , 16e O OCH CH Cp Zr 2 3 2 Cl Zr(IV), d0, 16e 3) H+ 4) insertion to alkene and alkyne 5) H elimination - + 2 [Co(CO4)] + H HCo(CO4) Co(-I), d10, 18e Co(I), d8, 18e

5.3 molecular hydrogen complex

H H H H H H Cy3P CO R3P PR3 OC CO W Ru Cr OC PCy3 R3P H OC CO CO H CO weak back donation to hydrogen 6 W(0), d , 18e Ru(II), d6, 18e Cr(0), d6, 18e

5.4 agostic interaction agostic interaction: interaction of a coordinately-unsaturated transition metal with a C-H bond (two electrons involved in the C-H bond enter the empty d-orbital of a transition metal, resulting in a two electron three center bond) ex) H Cl Cl P H P H P Ti P Ti H H H Cl Cl Cl Cl -agostic interaction -agostic interaction

6. donation, back-donation 6.1 carbonyl complex ex) O CO C CO M CO M CO OC CO Ni CO Co Co HOMO LUMO OC CO OC CO OC CO ...etc dM n, donation dM n, back-donation

6.2 nitrocyl complex ex) L M O M NO n M NO N - NO Ph3P NO L M NO Ru Ph3P NO n-1 + + Cl PPh3 Ir LnM Cl PPh3 CO equivalent NO

6.3 molecular nitrogen complex 6.4 molecular oxygen complex

5+ PPh2Et (H3N)5Co O OC O Ir N O Co(NH3)5 Cl O N PPh Et Zr 2 N Zr N basic metal N N end-on 6.5 molecular carbon dioxygen complex

O O C M O C O M MC O 1-O O 2-C,O 1-C

high oxidation low oxidation metal metal 3 6.6 phosphine complex

basicity: PR3> PR2Ar> PRAr2> PAr3 acceptor ability: NO> CO> RNC> PF > PCl > PCl R> PBr R> P(OR) > PR > RCN> RNH > NH X 3 3 2 2 3 3 2 3 M P X d - * interaction X d - * interaction a. Structural factor Tolman cone angle: measure of size of ligand bite angle: bidentate ligand

P P P M M Table 9-7 Table 9-8 b. electronic factor

(R3P)Ni(CO)3: there is a strong correlation between CO and electron donating ability of phosphine ligand. Table 9-9

6.7 carbene complex

Schrock carbene: nucleophilic carbene Fisher carbene: electrophilic carbene high oxidation state low oxidation state early transition metal middle and late transition metal -donor ligand -acceptor ligand hydrogen and alkyl substituents on carbenoid carbon -donor substituents on methylene

R R R LnM C LnM C LnM R R R R OMe Me OC CO Ta W H Tebbe complex OC CO CO H W(II), d4, 18e Ta(V), d0, 18e synthesis of carbene complex

OLi + OMe Ph hv PhLi Me3O PhLi W(CO) (OC)5W (OC)5W (OC) W Ta(CH3)3(OAr)2 Ta(=CH2)(CH3)(OAr)2 6 5 Ph Ph Ph

Me CH Cl Cl - 2 EtOH OEt (C5H5)2Ta BF4 + CH =P(CH ) (C5H5)2Ta Cl Pt CNC6H5 Cl Pt Me 2 3 3 Me NHC6H5 PPh3 PPh3

H H 1-C H Me 1-C10H7 Me 10 7 N N (OC) W W(CO)6 + 5 N N H H 1-C H 1-C10H7 Me 10 7 Me

7. -bonding ligand

7.1 alkene complex Dewar-Chatt-Duncanson model

Cl Cl Pt Cl Rh Rh C C Cl M Cl M C C d *, back-donation dM , donation M

C C M M C C

high oxidation state anionic complex electron donating ligand 4 7.2 alkyne complex Dewar-Chatt-Duncanson model can be applied to alkyne complex.

O O R R Ph OC Mn + R R OC (OC)3Co Co(CO)3 (OC)3Co Co(CO)3 Ph

7.3 -allyl complex

HB HB 95~120° HA HA

HA: anti H : syn d dyz M B z2 syn-anti isomerization allylic rotation M M H H B B HB HB HB HA HB HA H H H H A A A A M HA HB HA HB L1 Mo L1 Mo M L2 L2

cf) crotyl complex: racemization, 1,3-disubstituted allylic complex: syn-anti isomerization

7.4 diene complex molecular orbital (figure 9-20)

M M

diene metallacyclopentene back donation Zr, Ta, Nb

R1 R1 R2 R2 Zr Zr Zr Zr R1 R R1 2 R2 racemic

R2 R1 R1 R2 (CO)3Fe (CO)3Fe (CO)3Fe R1 R2 7.5 cyclopentadienyl complex

Cp*= C (CH ) 3-indenyl ex) ferrocene 18e 5 3 5 M M cobaltcene 19e 5 M -C5H5 nickellocene 20e 1-C H 5 5 metallocene (figure 9-22)

synthesis of cyclopentadienyl complex Cl Cl H Ti Ta Cl Mo 1) metal salt + cyclopentadienyl anion Cl Cl H FeCl2 + 2C5H5Na (C5H5)2Fe+ 2NaCl Ti(IV), d0, 16e Ta(V), d0, 18e Mo(IV), d2, 18e 2) redutive condition electrophilic nucleophilic RuCl + 3 3C5H6 + 1.5Zn(C5H5)2Ru + C5H8 + 1.5ZnCl2

5 7.5 benzene complex

Cr CO Cr Fe OC CO Cr(0), d6, 18e Cr(0), d6, 18e figure 9-24 F(II), d6, 18e synthesis of arene complex 1) arene + metal salt Na2S2O4 CrCl + - 3 2C6H6 +1/3AlCl3 + 2/3Al Cr AlCl4 Cr

Cr(I), d5, 17e Cr(0), d6, 18e

2) ligand exchange

Mo(CO) 6 + Mo CO OC CO Mo(0), d6, 18e

3) hydrogen extraction from cyclohexadiene

Cl L RuCl + Ru Cl Ru 3 Cl Mo Cl Cl L Cl 6 Ru(II), d6, 18e Ru(II), d , 18e

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