18 electron rule: EAN rule (Effective Atomic Number)

1. 18 electron rule: EAN rule (Effective Atomic Number) In 1927, developed by Sidgwick d electrons of metal + electrons of ligand = 18 electrons • 4 5 6 7 8 9 10 11 12 • d3 d4 d5 d6 d7 d8 d9 d10 • Sc Ti V Cr Mn Fe Co Ni Cu Zn • Y Zr Nb Mo Tc Ru RhPd Ag Cd • Ta W Re Os Ir Pt Au Hg

3. Ni: 1s22s22p63d84s2 : it is better to promote 4s electron to 3d, therefore Ni(0) is d10. Cu(I), Ag(I), and Au(I) is d10, Zn2+, Cd2+, andHg2+ is d10 Ti(IV) serves as a good index for memorizing the d electrons Because it is a d0 metal ion. TiCl4 is colorless, diamagnetic liquid TiCl3 is violet color

4. tetrahedral octahedral Square planar Trigonal bipyramid

7. Ni(CO)4, Fe(CO)5, Cr(CO)6, Ni(CO)4, For Mn, Mn(CO)5: 17 electrons Mn(CO)6: 19 electrons Mn(CO)5 (CO)5Mn-Mn(CO)5 HMn(CO)5, CH3Mn(CO)5, ClMn(CO)5 CH3Mn(CO)5 CH3- + Mn(CO)5+

9. 18 Electron Rule: strong field ligand such as CO, Hydride, Cycanide anion. Not good for Aqua complex: Weak Field Ligand such as H2O is not matched with 18 electron rule. Late transition metal is better than early transition metals.

10. Exceptions Early trantion metals (η5-C5H5)2ZrCl2: 5ex2+4e+2e=16e, (CH3)3TaCl2는 1ex3+5e+2e=10e (CH3)6W는 1ex6+6e=12e For early transition metals, there is not enough room to attach many ligands to satisfy 18 electron rule. Coordination number: number of ligand to bind to metal. Coordination number cannot be larger than the maximun oxidation number or the group number of element. For Late transition Metals (PPh3)3Pt: 2ex3+10e=16e (η5-C5H5)2Ni:5ex2+10e=20e

11. d8complex: 16 electrons Pt(II), Pd(II), Cu(III), Ir(I), Rh(I): square planar For example, Cl(PPh3)3Rh(I) (Wilkinson’s complex), Cl(PPh3)2(CO)Ir(I) (Vaska’ complex), (PPh3)2(CCPh)2Pt(II) even though they contains strong field ligand

15. 1.3 Mechanism in Organometallic Chemistry • oxidative addition (산화성부가반응) and • reductive elimination (환원성 제거반응 ) • 2. insertion (삽입반응) and deinsertion • (이탈반응) • 3. Oxidative coupling (산화성결합반응)and • Reductive Cleavage (환원성결합분열)

16. 1. oxidative addition (산화성부가반응) and reductive elimination (환원성 제거반응 ) two electron oxidative addtion (이전자 산화성부가반응) and one electron oxidative addition (일전자 산화성부가반응) A; 16 electron complexes B: 18 electron complexes

17. H2Fe(CO)2-4 20 electron complex Na2Fe(CO)4 18 electron complex [RFe(CO)4]+X- 18 electron complex

19. Rh(II), Co(II) d7 complex

20. 1965, Chatt and Davidson Kinetic Factor Thermodynamic Factor

21. In 1982, Bergman, Graham, Jones

22. Endo methyl migration: aromatic stablization energy

23. Reductive Elimination: spontaneous To do reductive elimination, two ligands should be placed at cis-position Concerted Mechanism

24. Transphos Ligand: Pd(II) is dsp2 (square planar): no reductive elimination Addition of CH3I allows to make cis-dimethyl to undergo reductive elimination.

25. 2. Elimination of one of ligand to make T-shape to Y shape. 3. Reduce the electron density of central metal Ligand off from metal by heat or light, oxidize the metal, addition of strong pi-acceptor ligand such as CO, maleic anhydride, quinone, tetracyanoethylene

26. 1. Insertion (삽입반응) and Deinsertion (이탈반응)

27. Migratory Insertion: cis position and concerted mechanism Order: h3-allyl ≥ Et 〉Me 〉PhCH2 〉vinyl ≥aryl, ROCH2 〉HOCH2 Hard to migrate to CO: Hydride(H-), acyl (CH3CO), CF3 ,Heteroatome: RO-, R2N

28. Decarbonylation

29. Hydride Insertion: cis-addition, 4-centered transition state For example: hydroboration, hydrosilylation, hydroformylation Reverse Reaction: b-Hydride Elimination The reason why it is hard to make a long chain alkylmetal complex

30. Alkyl Migration into olefin: olefin polymerization

31. Order of Migration of sigma liand-metal complex to Olefin: H >> R, vinyl, aryl> RCO>>RO, R2N Heteroatom is hard to migrate because of strong bond of heteroatom bearing lone pair to metal

32. Alkyne undergoes migratory insertion, but further successive reaction make polymer compounds, which make complication. Other Insertion, deinsertion substrate; isocyanide (:C≡NR), carbene(:CR2), SO2 , etc

33. Nucleophilic Addition Reaction (친핵부가반응) reverse sterechemistry to migratory insertion High valent metal species: electron deficient metal

34. Trans-Addition Product

35. Order of Reactivity 1.4.3 Oxidative coupling (산화성결합반응) Reductive Cleavage (환원성결합분열) M: +2 Increase

36. Electron withdrawing or strained molecules For alkyne, electron-withdrawing is no necessary