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

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

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.

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.

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.

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

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

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

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

Homogeneous catalysis: alkene (olefin) metathesis

Homogeneous catalysis: industrial applications Alkene hydrogenation Wilkinson s catalyst

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

Monsanto acetic acid synthesis

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

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.

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.

Hydroformylation (xo-process)

Hydroformylation (xo-process)

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.

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

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 @Si 2 PPh 3 + Li, BuCl, Cl(CH 2 ) 3 @Si 2 -LiCl PPh 2 @Si 2 P P P P Si 2 P P P P P(PPh 2 ) 3 P(PPh 2 ) 3 @Si 2 P(PPh 2 ) 3 + Li, BuCl, Cl(CH 2 ) 3 @Si 2 -LiCl P(PPh 2 ) 3 @Si 2

CATALYSIS of Pentachlorophenol PCP [PCP] (µm) 175 150 125 100 75 50 25 0 [Cl - ] [PCP] 0 60 120 180 240 1440 time (min) 800 600 400 200 0

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 III @Si 2 DPEIFe III @Si 2

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

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

Heterogeneous catalysis: commercial applications Alkene polymerization: Ziegler atta catalysis

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.

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

Fischer-Tropsch (carbon chain growth)

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.