Homogeneous catalysis alkene olefin metathesis

The catalytic turnover number (TON) is the number of moles of product per mole of catalyst this number indicates the number of catalytic cycles for a given process, e.g. after 2 h, the TON was 2400. The catalytic turnover frequency (TOP) is the catalytic turnover per unit time the number of moles of product per mole of catalyst per unit time, e.g. the TOF was 20min.  

Defining the catalytic turnover number and frequency is not without problems. For example, if there is more than one product, one should distinguish between values of the total TON and TOF for aU the catalytic products, and specific values for individual products. The term catalytic turnover number is usually used for batch processes, whereas catalytic turnover frequency is usually apphed to continuous processes (flow reactors). 

Now we turn to the question of selectivity, and the conversion of propene to an aldehyde provides a good example. Equation 26.5 shows the four possible products that may result from the reaction of propene with CO and H2 (hydroformylation see also Section 26.4). 

The choice of catalyst can have a significant effect on these ratios. For reaction 26.5, a cobalt carbonyl catalyst (e.g. HCo(CO)4) gives a 80% C4-aldehyde, 10% C4-alcohol and 10% other products, and an h ratio 3 1. For the same reaction, various rhodium catalysts with phosphine cocatalysts can give an n i ratio of between 8 1 and 16 1, whereas ruthenium cluster catalysts show a high chemo-selectivity to aldehydes with the regioselectivity depending on the choice of cluster, e.g. for Ru3(CO)i2, a 2 1, and for [HRu3(CO)ii], 74 1. Where the hydroformylation 

Ph2PCH2CH2PPh2), the ligand bite angle (see structure 6.16) can significantly influence the product distribution. For example, the n i ratios in the hydroformylation of 

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Chapter 26 Homogeneous catalysis alkene (olefin) metathesis 789... 

Phosphine-modified cobalt hydroformylation is only used commercially by Shell. It is tightly coupled to Shell s Higher Olefins Process (SHOP, see Metathesis Polymerization Processes by Homogeneous Catalysis) that produces a C4 through C20 mixture of linear, internal alkenes for hydroformylation to detergent-grade alcohols. 

An Organometallic Com pound That Occurs Naturally Coenzyme B,2 591 Organocopper Reagents 592 Palladium-Catalyzed Cross-Coupling 595 Homogeneous Catalytic Hydrogenation 597 Olefin Metathesis 600 Ziegler-Natta Catalysis of Alkene Polymerization 603 Summary 606 Problems 608... 

Homogeneous Catalysis of Alkene Hydrogenation 599 Olefin Cross-Metathesis 602... 

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