ΑΝΟΡΓΑΝΗ ΙΙΙ. Prof. Dr. Maria Louloudi. Laboratory of Biomimetic Catalysis & Biomimetic Materials. Chemistry Department. University of Ioannina

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1 Prof. Dr. Maria Louloudi Laboratory of Biomimetic Catalysis & Biomimetic Materials Chemistry Department University of Ioannina ΑΝΟΡΓΑΝΗ ΙΙΙ Μηχανισµοί Ανόργανων Αντιδράσεων (στοιχειοµετρικές αντιδράσεις) Κατάλυση από σύµπλοκα (καταλυτικές αντιδράσεις) Στοιχεία Βιοανόργανης Χηµείας

2 Κατάλυση από σύµπλοκα (καταλυτικές αντιδράσεις) A catalyst is a substance that alters the rate of a reaction without appearing in any of the products of that reaction; It may speed up or slow down a reaction. A homogeneous catalyst is in the same phase as the components of the reaction that it is catalysing. A heterogeneous catalyst is in a different phase from the components of the reaction for which it is acting. Energy profiles for a reaction: catalysed versus non catalysed A schematic representation of the reaction profile of a reaction without and with a catalyst. The pathway for the catalysed reaction has two steps, and the first step is rate determining.

3 Catalytic cycles A catalytic cycle consists of a series of stoichiometric reactions (often reversible) that form a closed loop; The catalyst must be regenerated so that it can participate in the cycle of reactions more than once. Catalytic cycle for the Wacker process; for simplicity, we have ignored the role of coordinated H 2, which replaces Cl - trans to the alkene.

4 Choosing a catalyst. the concentration of catalyst required;. the catalytic turnover;. the selectivity of the catalyst to the desired product;. how often the catalyst needs renewing. The catalytic turnover number (T) is the number of moles of product per mole of catalyst; this number indicates the number of catalytic cycles for a given process. αριθµός επανάληψης του καταλυτικού κύκλου The catalytic turnover frequency (TF) is the catalytic turnover per unit time: the number of moles of product per mole of catalyst per unit time. συχνότητα επανάληψης του καταλυτικού κύκλου the n:iratio of the aldehydes (regioselectivity of the reaction) (τοποεκλεκτικότητα) the aldehyde :alcohol ratio for a given chain (chemoselectivity of the reaction) (χηµειοεκλεκτικότητα) Although a catalytic cycle shows a catalyst being regenerated and passing once more around the cycle, in practice, catalysts eventually become exhausted or are poisoned, e.g. by impurities in the feedstock.

5 Homogeneous catalysis: Isomerization (double-bond migration) Η ισοµερίωση περιλαµβάνει µεταφορά Η από το µεταλλικό σύµπλοκο υδριδίου σε ενταγµένο αλκένιο παρέχοντας ένα σ-αλκυλ-σύµπλοκο RhH(C)(PPh 3 ) 3 + C 2 F 4 Rh(CF 2 CF 2 H)(C)(PPh 3 ) 2 + PPh 3 Πρώτο βήµα: ένταξη αλκενίου εύτερο βήµα: µεταφορά Η, σχηµατισµός αλκυλ-υποκαταστάτη Τρίτο βήµα: αντιστρεπτή αντίδραση: β απόσπαση

6 Homogeneous catalysis: Isomerization (double-bond migration) Anti-Markovnikov προσθήκη: οµογενοποιεί τα Η της β-θέσης, δεν ισοµεριώνει το αλκένιο Markovnikov προσθήκη: α) β-απόσπαση Η από CH 3 επανασχηµατισµός αρχικού αλκενίου β) β-απόσπαση Η από CH 2 σχηµατισµός ενός αλκενίου-2 Ισοµερίωση επιτυγχάνεται µόνο µέσω Markovnikov-προσθήκης παρέχοντας αλκένια -2 cis- ή trans- ή και τα δύο

7 Homogeneous catalysis: alkene (olefin) metathesis Examples of alkene (olefin) metathesis reactions with their usual abbreviations Grubbs catalysts

8 Homogeneous catalysis: alkene (olefin) metathesis A catalyic cycle for ring-closure metathesis (RCM) showing the Chauvin mechanism which involves [2 + 2]-cycloadditions and cycloreversions.

9 Homogeneous catalysis: alkene (olefin) metathesis

10 Homogeneous catalysis: industrial applications Alkene hydrogenation Wilkinson s catalyst

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13 is used in the treatment of Parkinson s disease (Monsanto) The anti-inflammatory drug aproxen (active in the (S)-form) is prepared by chiral resolution or by asymmetric hydrogenation of a prochiral alkene

14 Monsanto acetic acid synthesis

15 Monsanto acetic acid synthesis The Monsanto acetic acid process involves two interrelated catalytic cycles.

16 Tennessee Eastman acetic anhydride process MeH by MeC 2 Me H 2 bymec 2 H MeC 2 H by (MeC) 2 Catalytic cycle for the Tennessee Eastman acetic anhydride process.

17 Hydroformylation (xo-process) complications Co 2 (C) 8 hydrogenation of aldehydes to alcohols alkene isomerization HCo(C) 3 (PBu 3 ) HRh(C)(PPh 3 ) 3 This is controlled by using H 2 :C ratios greater than 1:1 Competitive catalytic cycles in the hydroformylation of alkenes to give linear (inner cycle) and branched (outer cycle) aldehydes.

18 Hydroformylation (xo-process)

19 Hydroformylation (xo-process)

20 Alkene oligomerization Παραγωγή ολεφινών υψηλού Μ.Β. Με τη µέθοδο της Shell Simplified catalytic cycle illustrating the oligomerization of ethene using a nickel-based catalyst; L = phosphine, X = electronegative group.

21 Homogeneous catalyst development Polymer-supported catalysts Καρβονυλίωση MeH παρουσία MeI σχετίζεται µε τη διαδικασία Monsanto

22 Παραγωγή Η 2 από µυρµηκικό οξύ P HCH (l) H 2 (g) + C 2 (g) P Si 2 P HCH (l) C (g) + H 2 PPh 3 PPh 2 PPh 3 + Li, BuCl, Cl(CH 2 ) 2 -LiCl PPh 2 P P P P Si 2 P P P P P(PPh 2 ) 3 P(PPh 2 ) 2 P(PPh 2 ) 3 + Li, BuCl, Cl(CH 2 ) 2 -LiCl P(PPh 2 ) 2

23 CATALYSIS of Pentachlorophenol PCP [PCP] (µm) [Cl - ] [PCP] time (min)

24 F 3 C F 3 C H H HFEI H F 3 C CF 3 F 3 C CF 3 H Fe Cl HFEIFe III Cl CF 3 CF 3 H Fe Cl DPEIFe III Cl Si 2 Si 2 H H F 3 C F 3 C Fe Cl CF 3 CF 3 Fe Cl HFEIFe 2 DPEIFe 2

25 C 6 H 5 H C 6 H 5 H H C 6 H 5 L1 C 6 H 5 Me Me Si Me Si H C 6 H 5 C 6 H 5 C 6 H 5 H L1-S H C 6 H 5 H 3 reflux, 6h Mn II C H Si H C H C H C 6 H 5 C 6 H 5 Mn C 6 H 5 C 6 H 5 Mn II -L1-S C H C H Si H C C 6 H 5 Mn II -L1@AC C 6 H 5 C 6 H 5 Mn C 6 H 5

26 Ετερογενής κατάλυση: επιφάνειες & αλληλεπιδράσεις µε τις προσροφηµένες ουσίες σωµατίδια µετάλλων διασπορά γ-αλούµινα πυριτία (σίλικα)

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28 Heterogeneous catalysis: commercial applications Alkene polymerization: Ziegler atta catalysis

29 Heterogeneous catalysis: commercial applications Alkene polymerization: Ziegler atta catalysis καταλύτης:δ-ticl 3 συγκαταλύτης: Et 2 AlCl καταλύτης:ticl 4 Υποστηριγµένος σε MgCl 2 συγκαταλύτης: Et 3 Al A schematic representation of alkene polymerization on the surface of a Ziegler atta catalyst; the vacant coordination site must be cis to the coordinated alkyl group.

30 Heterogeneous catalysis: commercial applications Alkene polymerization: Ziegler atta catalysis µεταλλοκένια ως καταλύτες υποστηριγµένα σε Si 2, Al 2 3, MgCl 2 µηχανισµός:

31 Fischer-Tropsch (carbon chain growth)

32 Haber process (industrial production of H 3 ) The catalyst used industrially is active a-fe which is produced by reducing Fe 3 4 mixed with K 2 (an electronic promoter which improves catalytic activity), Si 2 and Al 2 3 (structural promoters which stabilize the catalyst s structure). High-purity materials are essential since some impurities poison the catalyst.