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Strategies to Introduce „Free Coordination Sites“ 1. 2. 3. 4. 5. 6. 7. 8

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Strategies to Introduce „Free Coordination Sites“ 1. 2. 3. 4. 5. 6. 7. 8 R 1. R N P R OC P Mo N CO 2. Cr OC Cr P N OC OC P H P N CO Ru TheSteric Complete Restriction P Ph Symmetric Restriction P Steric Restriction Reductive Elimination 8. Co N Pd H N O Agostic Interactions Hemilability M 3. Strategies to introduce „Free coordination sites“ PCy3 Cl H Ph CO Ru OC Mn CO Cl OC PCy3 7. CO Neighboring group Effect N Pseudo-Jahn-Teller-Effect O W Ph F C 3 Rh 6. 4. O F3C 5. OC CO CF3 Indenyl Effect CF3 1 Dynamic Lone Pair 1. Steric restrictions + - N2 + 6 H + 6e R R R R R R R R cat. N N N R R R R N 2 NH3 N N Mo N Mo N + - N N H , e N N R R + - R R -NH3 H , e NH R R R R R R N N Mo N R N R N + - H2N H , e N Mo N N N R R R R R R R R R R R R + - NH2 H , e R R R R H+, e- R + - N R N H , e HN N N Mo N N Mo N -NH3 Mo N N N N N N N 2 Symmetric restrictions R R 1. R R + - N N2 + 6 H + 6e N R cat. R N Mo N 2 NH3 N N 15e-complex rather than 17e-complex E one lone pair is non-bonding! 3 Electron-transfer-Catalysis 1. Electronic restrictions CH3 CH3 PPh 18e-Complex 3 18e-Complex Mn Mn CO CO H CCN slow Ph P 3 CO 3 CO o E =0.19V Eo=0.52V CH3 CH3 PPh 3 17e-Complex 17e-Complex Mn fast Mn CO CO H CCN Ph P 3 CO 3 CO CH3 Mn CO H3CCN CO The reaction works catalytically, because PPh 3 is a stronger π-acid than CH 3CN. Thus, the substituted complex becomes more precious than the starting compound. 4 1. Electron-transfer-Catalysis Electronic restrictions CO CO CO CO OC Mo CO PPh Mo 18e-Complex 3 OC PPh3 18e-Complex OC OC slow CO CO CO CO CO -CO, +PPh3 CO Mo OC CO OC Mo PPh 17e-Complex 17e-Complex 3 OC OC CO CO CO CO OC Mo CO OC CO 5 Electronic restrictions 1. CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO CO Mo Mo Mo Mo OC Mo CO OC Mo PPh3 OC CO OC PPh3 OC Mo CO OC Mo PPh3 OC CO OC PPh3 OC OC OC OC OC OC OC OC CO CO CO CO CO CO CO CO - - A B A B + + E A B A B metal center in B more electron rich than in A metal center in B less electron rich than in A CH CH CH3 CH CH 3 3 CH 3 3 CH CH3 Mn Mn Mn Mn Mn Mn Mn CO CO Mn CO CO CO CO CO H3CCN Ph P CO Ph3P H3CCN Ph3P H3CCN Ph P CO 3 CO H3CCN CO CO CO CO 3 CO - CO- A B A B A B+ A+ B E 6 Reductive elimination 2. P CN P II H Ru P Ph cat. P ∆ - H Ph N CN P P P P P P Ru0 Ru CN Ru CN P P P P P P H3C Red El Ox Add (CH-activation) P P H N H P C P N CN Ru Ru PP PP α-H-insertion 7 hemilability 3. N CH3 Pd O N Solv C cat. CO O CH N 3 N Solv N Pd Pd Pd n N N CO N C C O O O N C CO O O N N N Pd CO Pd Pd Pd N N N N O O O N C Pd N O 8 Temporary free Coordination Sites (Hemilabile Ligands) 3. Electronically (enthalpically): introduction of a M-D (hart-soft) or (soft-hard) interaction rather than (hard-hard) or (soft-soft) labile or weak D Entropically: M M Ring size smaller or larger than 5 D stable (or inert) Sterically (enthalpically): introduction of large substituents at D (tBu, Adamantyl) 9 Temporary free Coordination Sites (M-H cis to CO) 4. Metal hydrides insert CO in contrast to M-Alkyls reversibly ! Metal hydrides often substitute easier than other similar complexes. They are sensitive to traces of radicals present, because those start a radical reaction by homolysis of the M-H bond! L L H H OC Mn OC Mn CO OC OC O CO CO Regel 6 -CO H L CO CO H +L CO H OC Mn CO OC Mn OC Mn OC OC OC O O CO CO H CO CO OC Mn CO Rad OC CO -CO L -CO OC CO L L CO CO Mn +L OC Mn CO CO H CO OC Mn Mn OC OC OC CO CO OC OC CO O H 10 Neighboring group effect 4. PP W 18e-complex 16e-complex 16e-complex 18e-complex P P H PP PP P PP P PP W W W W P P P P H P H PP W H H P P P H 16e-complex 18e-complex H H H H H P P P PP P W W W P P P H P P P PP 16e-complex W 16e-complex P P H 18e-complex H H H H PP P W P 18e-complex P W H P P P 11 Dynamic lone pair 5. Formally an 18e-complex C1 C3 C2 C4 R R R N N R R cat. N R N N O Mo R PMe3 O Mo R O Mo R O C C F3C O PMe3 O 1 3 F3C CF F C F3C 3 3 F C F3C CF3 3 CF3 CF3 C2 C4 CF3 CF3 18e-Complex 18e-Complex 18e-Complex O O O N N N OC CO +L OC CO -CO OC CO Mn Mn Mn OC CO OC CO OC L L 18e-Complex 18e-Complex 18e-Complex O Mn O Mn +L O Mn -PPh3 L PPh3 Racemization N N N R R R O O O 12 Characterization of metal carbonyl complexes to classic non- classic 70 metal-π-donation predominates Ligand-σ-donation predominates 13 Characterization of metal nitrosyl complexes to to 74 Ligand-π-donation predominates Ligand-σ-donation predominates 14 Indenyl effect 6. N2 CHCO2Et 18e-complex 18e-complex 16e-complex R'RC O PPh3 cat. N2 CHCO2Et Ru PPh3 Ru Ph3P CHCOOEt PPh3 Ru Cl -N2 CHCOOEt Cl PPh -PPh Cl N 3 3 PPh 2 3 PPh3 R'RC CHCOOEt N2 CHCO2Et O PPh3 -PPh3 Ru PPh3 Ru Cl CHCO2Et -N2 PPh3 Cl PPh3 N CHCO Et 2 2 Ph3P 18e-complex 18e-complex 15 Temporary free Coordination Sites (Charged Polyenes) 6. Electron-withdrawing and „rearomatizing“ substituents, annelated to the charged Polyene, facilitate the substitution at the Metal Center (Indenyl-Effect)! 18e-Komplex 18e-Komplex 18e-Komplex + PPh3 + CO Rh Rh Rh OC CO OC CO OC PPh3 PPh3 CH3 H3C PPh + CH NO2 3 3 H3C H3C CH3 > > > > > > CH3 CH3 H3C H3C CH3 CH3 16 Indenyl effect 6. 17 Pseudo-Jahn-Teller effect 7. PR X Ph 3 PR3 Ph PR3 PR3 X Pd Pd X Pd X Pd X base cat. PR3 PR3 Pd X Pd X base*HX H H Ph Ph E D4h C2v D3h L L L L M L L M L M L L L 18 7. Desymmetrization effects Coupling of electronic and vibrational structure (Vibronic) Effect Jahn-Teller 1. order Jahn-Teller 2. order Pseudo-Jahn-Teller Renner-Teller E Γ Γ c Γb c Γc Γc Γa Γa Γa Γ Γa b Γc Γb Γb H HH H 19 Hidden Coordination Sites (Jahn-Teller-Effect) 7. E D4h C2v D3h L L L -L L M L L M L M L L L High T 31 P-NMR Low T b a 2920 Molecular vibration Molecular Rotation Process Chemical Dynamic exchange processes Macroscopic transport processes slow s ms µs ns ps fs fast Line wide- perturbation slow fast The NMR time scale Finding exchange exchange Spectroscopic Longitudinal Magnetization exchange Relaxation Spectral Larmor- 21 time scale time scale time scale Pseudo-Jahn-Teller effect 7. PPh3 PPh3 Ph3P Rh PPh3 Ph3P Rh PPh3 Cl 22 18e-Complexes 7. Pseudo-Jahn-Teller effect Le L M Pseudo-Jahn-Teller-EffectJahn-Teller-Effekt in casebei of d d6-low-spin6-low-spin E E Oh E C4v D3h Le VerlustLoss ofder a a e a e L M L L M +L + L L M +Le + L L M L StereokontrolleStereo control L M Le L M Le 23 Pseudo-Jahn-Teller effect 7. T- or Y- shape? −π-donors maximize the angle to each other −σ-donors and π-aceptors prefer 90° and 180° angles to each other 24 Agostic interactions 8. n Zr H Zr Zr H H H cat. XHY Y=C, B, Si Y=C, N, O, F 2e-3c 4e-3c n X=M X=B X=M X=N, O, F agostic IA 2e-3c-Bondung anagostic IA Hydrogen-bonding IA Reason: mainly orbital interaction (IA) Reason: mainly electrostatic interanction (IA) Y H XHY X Y Y Y B δ δ δ VB: H H H H XHY XHY M M M B MO: π-Rückbindung σ-Hinbindung bindend nicht-bindend anti-bindend n (erfordert d - (immer möglich) Konfiguration) Ph H O H2N N H H H N N Br Ni NH N NH Co B B Br N N HN N H H H H O H Ph 25 agostische WW 2e-3c-Bindung anagostische WW Wasserstoffbrücken-WW Hidden free Coordination Sites (agostic Hydrogens) 8.
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