Organometallics Study Meeting

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1 rganometallics Study eeting 04/21/2011.itsunuma 1. rystal field theory(ft) and ligand field theory(lft) FT: interaction between positively charged metal cation and negative charge on the non-bonding electrons of the ligand LFT: molecular orbital theory(back donation...etc) ctahedral(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. ligandfieldsplittingparameter( 0 ):energybetweene g orbitalandt 2g orbital 1) high oxidation state 2) 3d<4d<5d 3) spectrochemical series I - <Br - <S 2- <S - < - < 3 -,F - <( 2 ) 2, - <ox, 2- < 2 <S - < 5 5, 3 < <bpy,phen< 2 - < 3 -, < - < cf) pairing energy: energy cost of placing an electron into an already singly occupied orbital Low spin: If 0islarge,thenthelowerenergyorbitals(t 2g )arecompletelyfilledbeforepopulationofthehigherorbitals(e g ) igh spin: If 0issmallenoughthenitiseasiertoputelectronsintothehigherenergyorbitalsthanitistoputtwointothesamelow-energy orbital, because of the repulsion resulting from matching two electrons in the same orbital ex)(t 2g ) 3 (e g ) n (n=1,2) Tetrahedral(figure 9-1b), Square planar(figure 9-1c) LFT(figure 9-3, 9-4) -,Br - :lower 0(figure9-4a) :higher 0(figure9-4b) 2. Ligand metal complex hapticity formal chargeelectron donation alkyl hydride X halogen alkoxide acyl alkenyl allyl acetylide carbene carbene carbyne carbonyl metal complex hapticity formal chargeelectron donation 6 -arene hydride X -halogen alkoxide carbonyl alkylidene carbonyl alkylidine alkene alkyne allyl diene cyclo pentadienyl

2 3. d-electron o o(iv),d 2,18e o(iv):d 2 =2e 2( 5 5 ) - :2x6e=12e 2 - :2x2e=4e () 4 o o() 4 o(0),d 9,18e o(0):d 9 =9e 4():4x2e=8e o-o:1x2e=2e (valency), [d-electron of (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...) 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 ctahedral [o( 2 ) 6 ] 2+ (19e) [i(en) 3 ] 2+ (20e) V() 6 (17e) W( 3 ) 6 (12e) late transition metal: small 0 occupationofe g earlytransitionmetal Square planar [( 6 5 ) 3 P] 2 PdX 2 (16e) [( 6 5 ) 3 P] 2 Ir()X(16e) instabilityofd x2-y2 5. -bonding ligand 5.1 alkyl complex -bond:130~300kjmol -1 -hydride elimination stable alkyl complexes W( 3 ) 6 W(VI),d 0,12e Zr( ) 4 Zr(IV),d 4,8e Ti[ 2 ( 3 ) 3 ] 4 Ti(IV),d 0,8e synthesis of alkyl complexes r 4 r(iv),d 2,10e Fe 4 Fe(IV),d 4,12e L 2 Pt 1) etathetical exchange using a carbon nucleophile P 3 Pt P 3 P 3 n-bu P 3 + 2n-BuLi n-bu Pt 2) etal centered nucleophile Fe - a + Fe(0),d 8,18e + Br Fe - Fe(II),d 6,18e 3) xidative addition 3 P Ir + Br P e 3 P e Ir 3 Br P 3 Ir(I),d 8,16e Ir(III),d 8,18e 4) Insertion P 3 Pt P 3 P 3 Et P = 2 Pt 5.2 hydride complex -bond:240~350kjmol -1 synthesis of hydride complexes 1) etal halide + reductant 3) xidative addition u 2 (P 3 ) 3 + ab 4 + P 3 u 2 (P 3 ) 4 u(ii),d 6,16e u(ii),d 6,18e Ir()(P 3 ) 2 Ir(I),d 8,16e + 2 Ir 2 ()(P 3 ) 2 Ir(III),d 6,18e 2) Protonation p 2 W [p 2 W 3 ] + W(IV),d 2,18e W(VI),d 0,18e [o( 4 )] o( 4 ) o(-i),d 10,18e o(i),d 8,18e h(p 3 ) 3 h(i),d 8,16e + 2 h 2 (P 3 ) 3 h(iii),d 6,18e 2

3 4) rtho metallation, cyclo metallation 5) -hydride elimination W[P( 3 ) 3 ] 6 W(0),d 6,18e Pe 2 Pe W 3 Pe Pe 3 3 W(II),d 4,16e u 2 (P 3 ) 4 + 2K( 3 ) 2 u 2 (P 3 ) 4 + 2K + 2acetone u(ii),d 6,18e u(ii),d 6,18e eactivity of hydride complex 1) - p 2 Zr Zr(IV),d 0,16e p 2 Zr 2 Zr(IV),d 0,16e p 2 Zr 2 3 Zr(IV),d 0,16e 2). 2[o( 5 )] 3- o(ii),d 6,18e 3) + 4)insertiontoalkeneandalkyne 5) 2 elimination [o( 4 )] o( 4 ) o(-i),d 10,18e o(i),d 8,18e + 2[o( 5 )] 3- o(ii),d 7,17e molecular hydrogen complex y 3 P W Py 3 W(0),d 6,18e 3 P u P 3 3 P u(ii),d 6,18e r r(0),d 6,18e weak back donation to hydrogen 5.4 agostic interaction agostic interaction: interaction of a coordinately-unsaturated transition metal with a - bond (two electrons involved in the - bond enter the empty d-orbital of a transition metal, resulting in a two electron three center bond) ex) P P Ti -agostic interaction P P Ti -agostic interaction 6. donation, back-donation 6.1 carbonyl complex d n, donation d LU n, back-donation ex) i oo...etc 6.2 nitrocyl complex L n-1 - equivalent L n + L n + ex) 3 P u P 3 3 P Ir P molecular nitrogen complex 6.4 molecular oxygen complex Zr Zr basic metal end-on ( 3 ) 5 o o( 3 ) 5 5+ P Ir 2 Et P 2 Et 6.5 molecular carbon dioxygen complex 1-2 -, 1 - high oxidation metal low oxidation metal 3

4 6.6 phosphine complex basicity:p 3 >P 2 Ar>PAr 2 >PAr 3 acceptorability:>>>pf 3 >P 3 >P 2 >PBr 2 >P() 3 >P 3 >> 2 > 3 a. Structural factor d - *interaction Tolman cone angle: measure of size of ligand bite angle: bidentate ligand X P X X d - *interaction P Table 9-7 P P Table 9-8 b. electronic factor ( 3 P)i() 3 :thereisastrongcorrelationbetween andelectrondonatingabilityofphosphineligand. Table carbene complex Schrock carbene: nucleophilic carbene high oxidation state early transition metal -donor ligand hydrogen and alkyl substituents on carbenoid carbon Fisher carbene: electrophilic carbene low oxidation state middle and late transition metal -acceptor ligand -donor substituents on methylene Ta e Ln Ta(V),d 0,18e Tebbe complex Ln Ln e W W(II),d 4,18e synthesis of carbene complex Ta( 3 ) 3 (Ar) 2 hv Ta(= 2 )( 3 )(Ar) 2 W() 6 Li () 5 W Lie 3 + () 5 W e Li () 5 W e ( 5 5 ) 2 Ta e BF ( 5 5 ) 2 Ta 2 2 =P( 3 ) 3 e Et Pt 6 5 P 3 Et Pt P e W() 6 + e e () 5 W e bonding ligand 7.1 alkene complex Dewar-hatt-Duncanson model Pt h h d, donation d *, back-donation high oxidation state anionic complex electron donating ligand 4

5 7.2 alkyne complex Dewar-hatt-Duncanson model can be applied to alkyne complex. n () 3 o o() 3 + () 3 o o() allyl complex B A A B 95~120 A :anti B :syn d z2 d yz syn-anti isomerization B A A B B A A B B A B A B A B A allylic rotation L L 1 2 o L L 1 2 o cf) crotyl complex: racemization, 1,3-disubstituted allylic complex: syn-anti isomerization 7.4 diene complex molecular orbital(figure 9-20) diene metallacyclopentene back donation Zr,Ta,b Zr 1 2 Zr 1 2 Zr 1 2 Zr 1 2 racemic 2 1 () 3 Fe 1 2 () 3 Fe 1 () 3 Fe cyclopentadienyl complex indenyl metallocene (figure 9-22) ex) ferrocene 18e cobaltcene 19e nickellocene 20e p*= 5 ( 3 ) 5 Ti Ta o synthesis of cyclopentadienyl complex 1) metal salt + cyclopentadienyl anion Fe a ( 5 5 ) 2 Fe+ 2a Ti(IV),d 0,16e electrophilic Ta(V),d 0,18e o(iv),d 2,18e nucleophilic 2) redutive condition u Zn ( 5 5 ) 2 u Zn 2 5

6 7.5 benzene complex r r Fe r(0),d 6,18e r(0),d 6,18e F(II),d 6,18e figure 9-24 synthesis of arene complex 1)arene+metalsalt r /3Al 3 + 2/3Al r a 2 S Al 4 r r(i),d 5,17e r(0),d 6,18e 2) ligand exchange o() 6 + o o(0),d 6,18e 3) hydrogen extraction from cyclohexadiene u 3 + u u L o L u(ii),d 6,18e u(ii),d 6,18e 6

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