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     Rh    Pd Ag Cd Ta      W     Re     Os     Ir      Pt  Au Hg

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+, and Hg2+ 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

tetrahedral octahedral Square planar Trigonal bipyramid

Electrons Ligand 1 수소라디칼(H radical), 알킬 라디칼(alkyl radical), 아릴 라디칼(aryl radical) , 할로겐 라디칼(halogen radical), NO (굽은 형태) 2 CO, CS, RCN, R3N, R3P, R3As, RCN, R2S, 수소음이온(H-), 알킬음이온(R-), 알켄 (alkene), η3-알릴 양이온(η3-allyl+), 알킨(alkyne), 니트로실 양이온(NO+), 할로겐 음이온(X-) 3 η3-알릴 라디칼(η3-allyl), NO (직선형) 4 η3-알릴 음이온(η3-allyl-), η4-C4R4(η4-cyclobutadiene), η4-비공액디엔(nonconjugate diene), η4-공액디엔(conjugate diene) 5 η5-C5R5 라디칼(η5-cyclopentadienyl radical) 6 η5-C5R5 음이온(η5-cyclopentadienyl anion), η6-C6R6, η7-C7R7 양이온(cycloheptatrienyl cation) 7 η7-C7R7 라디칼(cycloheptatrienyl radical) 8 η8-C8R8 (cyclooctatetraene)

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+ 

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.  

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

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

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)

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

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

Rh(II), Co(II) d7 complex

1965, Chatt and Davidson Kinetic Factor Thermodynamic Factor

In 1982, Bergman, Graham, Jones

Endo methyl migration: aromatic stablization energy

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

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

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

1. Insertion (삽입반응) and Deinsertion (이탈반응)

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

Decarbonylation

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

Alkyl Migration into olefin: olefin polymerization

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

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

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

Trans-Addition Product

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

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