PART 2. -BONDED ORGANOMETALLICS

Transcription

1 PART 2. -BODED ORGAOETALLIS

2 V() 6 r() 6 o() 6 W() 6 Fe() 5 Ru() 5 Os() 5 i() 4 Figure 1. Binary, ononuclear etal arbonyls n n O Fe O O Fe O o O o n 2 () 10 Fe 2 () 9 o 2 () 8 Fe Fe Fe Ir() 3 Os Os Os o Fe 3 () 12 () 3 Ir Ir() 3 Os 3 () 12 Ir() 3 Ir 4 () 12 Rh o Rh O Rh o Rh o Rh= Rh() 2 Rh o 4 () 12 Rh 6 () 16 Figure 2. Binary, Polynuclear etal arbonyls Rh 1

3 p s pσ p.. sσ p... pσ.. sσ.. O p s p s pσ p p.... pσ.... sσ sσ.. p s Figure 3. O Diagram for Figure 4. O Diagram for 2 Ο: Ο: σ-donation from -backbonding from Figure 5. Bonding of Terminal to Free Terminal µ 2 - µ ν co cm Figure 6. Effect on Stretching Frequency 2

4 n- σ O δ n σ O n+ σ δ+ O anionic neutral cationic V() 6 - r() 6 n() 6 + ν co cm Figure 7. Effect of harge on entral etal omplex v co cm -1 o(pf 3 ) 3 () , 2090 o(pl 3 ) 3 () , 2040 o(p{oe} 3 ) 3 () , 1977 o(pph 3 ) 3 () , 1934 o(e) 3 () , 1915 o(py) 3 () , 1888 Figure 8. Effect of Ancillary Ligands 3

5 etal + : i + i() 4 Fe + Fe() 5 at atmospheric pressure and room temperature at 100 bar and 150 etal salt + reducing agent + : Til 4 (DE) K[ 10 H 8 ] rown [K(15-crown-5) 2 ] + [Ti() 6 ] 2- Vl 3 + 3a diglyme [a(diglyme) 2 ] + [V() 6 ] - rl 3 + Al + in 6 H 6 r() 6 Wl AlEt 3 + in 6 H 6 W() 6 2 n(oac) AlEt 3 + n 2 () 10 Re 2 O 7 + Re 2 () 10 Ru(acac) H 2 Ru 3 () 12 2 o H 2 o 2 () 8 Figure 9. Synthetic ethods Fe() 5 a/hg THF RD a 2 [Fe() 4 RHO D + RX R(O)l H R O R R'X O R'X Fe RR' Fe O 2 O 2 O R OH X 2 X O 2 R' R 2 H H 2 O RR' 2 X R 2 H Figure 10. ollman s Reagent 4

6 σ-donation from 2 H 4 -backbonding from Figure 11. Dewar-hatt-Duncanson odel for onoolefin-etal Bonding H H H H weak olefin backbonding H H sp 2 sp 3 H metallocyclopropane H strong olefin backbonding Example: Example: Figure 12. Effect on Geometry H 2 H 2 l l Pt H 2 H Rh 2 F 2 l H 2 H2 F 2 Ph 3 P () 2 Pt Ph 3 P () pm 137 pm 140 pm 149 pm Figure 13. Effect on = Bond Length 5

7 totally a-bonding! σ δ Ligand Ψ 1 Ψ 2 Ψ 3 Ψ 4 s p y p x d xy etal p z d yz d xz d z 2 Figure 14. etal-ligand Interactions in Butadiene omplexes ground state excited state Ψ 4 Ψ 3 Ψ 2 Ψ 1 weak diene backbonding e-withdrawing ligands Ψ 4 Ψ 3 Ψ 2 Ψ 1 strong diene backbonding e-donating ligands Fe classify the butadiene ligand in these two compounds! Zr metallocyclopentene sp 3 Figure 15. Effect of Backbonding 6

8 l + 2 Fe() 5 -Fel 2-7 l Fe e(iv) Figure 16. Stabilisation of yclobutadiene on Fe() 3 Fragment RH 2 l Pt l Ph Ph 124 pm () 3 o o() pm Figure 17. 2e Alkyne Ligand Figure 18. 4e Alkyne Ligand : Oe R : Oe R Oe R carbene acts as L ligand sp 2 σ-donation to -backbonding from but, competes with: Figure 19. Bonding in a Fischer arbene omplex O e R 7

9 : : Pd : Figure 20. A Stable -Heterocyclic arbene (H) Figure 21. Palladium H omplex Fischer Schrock L type ligand X 2 type ligand L n : X Y L n X Y + X L n - Y electrophilic X L - n + Y nucleophilic Low oxidation state, e.g. r(0), Fe(0) High oxidation state, e.g. Ta(V) X, Y = R 2, OR L n = (-acceptor) X, Y = R, H L n = 5 H 5, l, R (/σ-donor) Figure 22. omparison of Fischer vs Schrock arbene omplexes 8

10 Pe Wl 6 Li -78 W + 2 Pe 3 -e 4 W t Pe Bu 3 Figure 23. Formation of Schrock's "yl-ene-yne" omplex etal Halide + Allyl Grignard Reagent: ibr H 5 gbr i Insertion of Dienes into -H: e o() 4 H + - o syn e + o anti HX Elimination from Propene omplex: base Pdl 2 + Pdl 2 -Hl l dimer. Pdl Pd Pd l u - or E + Attack on oordinated Alkene Ligand: e + e Ir e H + / e Ir H 3 Figure 24. Synthetic Routes to Allyl omplexes 9

11 syn anti H 3 H 2 H 1 H 2 H 1 H 1 H 3 H 2 H 3 H 1 H 2 H 2 η 3 H 1 η 1 H 1 η 3 H 2 H 3 Predict 1 H R of H 2 H 1 Pd l Pd l Hint: H 1 and H 2 do not couple to each 25 : 5 δ/ppm : 5 4 δ/ppm Figure 25. Fluxionality in η 3 -Allyl omplexes 3 10

12 a 1 e 1 e 2 σ a 1g s d z 2 p z a 2u p y d yz d xz p x e 1g e 1u δ d xy d x 2 -y 2 e 2g e 2g Figure 26. Bonding in etallocenes I 11

13 e 2g e 2u e 1u e 1g a 2u a 1g e 1u * a 2u * e 2g * a 1g * e 2u e 1g *.. σ.... δ a 1g ' e 2g a 1g.. 2u a e 1u e 1g Fe D 5d Fe p, a 2u, e 1u s, a 1g d, a 1g, e 1g, e 2g Figure 27. O Diagram for Ferrocene Frontier Orbital umber of Unpaired Spin Only agnetic Occupancy Electrons oment in µ Β V {e 2g } 2 {a 1g } r {e 2g } 3 {a 1g } n {e 2g } 2 {a 1g } 1 {e 1g *} Fe {e 2g } 4 {a 1g } o {e 2g } 4 {a 1g } 2 {e 1g *} i {e 2g } 4 {a 1g } 2 {e 1g *} Figure 28. Stable 1 st Row etallocenes 12

14 FG-PROBLE LASS 4 1. Explain why the carbonyl complexes [V() 6 ] -, [r() 6 ], and [n() 6 ] + exhibit similar patterns of bands in the ν stretching region of their IR/Raman spectra, but the frequencies (in cm -1 ) are highest for [n() 6 ] + and lowest for [V() 6 ] omplete the following reaction sequences: PhLi?? (a) r() >? > r() 5 {Oe}Ph > r() 4 I(Ph) xs LiH 2 e 3 (b) Tal 2 (e 3 H 2 ) >? -PF 3 (c) oh(pf 3 ) 4 + butadiene >? +? base (d) Pdl 2 + propene >? >? (e) r() 6 + cyclohepta-1,3,5-triene >? (f)fe() 5 + cyclopentadiene >??? All 3 /H 3 l (g) yclopentadiene >? > Fe(η- 5 H 5 ) >? 13

15 co-condense at 196 (h) Ti (a) + benzene >? (i) r() 6 + 1,3,5-trimethylbenzene >? 3. Place the following in increasing order of = bond length: 2 H 4, Pt(PPh 3 )( 2 () 4 ), K[Ptl 3 ( 2 H 4 )] 4. How do Schrock carbene complexes (alkylidenes) differ from Fischer carbene complexes? 5. Discuss the following observations: (a) Fe(η- 5 H 5 ) 2 and i(η- 5 H 5 ) 2 can be oxidised to the corresponding mono-cations, both of which have one unpaired electron. (b) The metal to ring distance in Fe(η- 5 H 5 ) 2 + is longer than in Fe(η- 5 H 5 ) 2, whereas the metal to ring distance in o(η- 5 H 5 ) 2 + is shorter than in o(η- 5 H 5 ) 2. 14