Oxidative addition of the carbon-halogen bond

Oxidative addition of the carbon-halogen bond is a well-documented reaction for Group 10 transition metal complexes, but it is relatively limited for ruthenium. The example given here involves the reversible oxidative addition of allyl halide to RuCp(CO)2X to produce RuCp(p -allyl)X2 [78]. Oxidative addition of allyl halide to a Ru(0) complex Ru(l,5-COD)(l,3,5-COT) is also reported, but the product yield was poor [79]. Nevertheless, a catalytic Heck-type alkenylation of bromostyrene with methyl acrylate by Ru(l,5-COD)(l,3,5-COT) proceeded smoothly [80]. A cross-coupling reaction of alkenyl halide with Grignard reagents or alkyl lithium also pro-... 

Transition-metal catalyzed metathesis of carbon-halogen bonds with Si-Si bonds provides useful access to organosilicon compounds. Most of the reaction may involve initial oxidative addition of the carbon-halogen bond onto the transition-metal followed by activation of the Si-Si bond to give (organosilyl)(orga-no)palladium(II) complex, which undergoes reductive elimination of the carbon-silicon bond. 

Both Ni and Pd reactions are proposed to proceed via the general catalytic pathway shown in Scheme 8.1. Following the oxidative addition of a carbon-halogen bond to a coordinatively unsaturated zero valent metal centre (invariably formed in situ), displacement of the halide ligand by alkoxide and subsequent P-hydride elimination affords a Ni(II)/Pd(ll) aryl-hydride complex, which reductively eliminates the dehalogenated product and regenerates M(0)(NHC). ... 

This type of oxidative addition involving the carbon-halogen bond cleavage may be involved in other catalytic processes using alcohols in the presence of hydrogen halide. For example, in the carbonylation of benzyl alcohol in the presence of HI, phenylacetic acid can be catalyfically produced in the presence of aPd(O) complex (Eq. 1.5) [25]. 

Palladium can effect cyclization of pyrroles and indoles with appropriately placed haloaryl substituents. The reaction presumably involves generation of a palladium(O) species which undergoes oxidative addition at the carbon—halogen bond followed by electrophilic metalation to form a diarylpalladium intermediate (Equation (123)) <90T4003,91TL3317,93TL5449). 

The iron slurries show exceptional reactivity toward oxidative addition reactions with carbon halogen bonds. In fact, the reaction with C.FcI is so exothermic that the slurry has to be cooled to 0 °C before the addition of C F L The reaction of iron with C F Br is also quite exothermic, hence, even for this addition, the iron slurry is cooled to about 0 ° C. The organoiron compound formed in the above reactions, solvated Fe(C.F )2, reacts with CO at room temperature and ambient pressure to yiela Fe(C,F3)2(CO)2(DMEL. 

A long-standing success in transition metal catalysis is the carbonylation reaction [66], in particular the synthesis of acetic acid [67]. Formally this is the insertion of CO into another bond, in particular into a carbon-halogen bond. After the oxidative addition to the transition metal (the breaking of the carbon-halogen bond), a reaction with a CO ligand takes place. This reaction is often called an insertion. Mechanistic studies have, however, shown that the actual reaction... 

How far can the catalyst diffuse or ring walk along the polymer backbone before either oxidative addition to a carbon-halogen bond or dissociation of the catalyst ... 

The mechanism of the Stille reaction involves an oxidative addition of the palladium(O) species into the carbon-halogen bond, a trans-metallation reaction with the organostannane and a final reductive elimination step releasing the product and thereby regenerating the palla-dium(O) catalyst. 

The degrees of the exchange reactions depend on several factors, the central metals, the ligands, the structures of the terminal groups, and the reaction conditions. The absence of carbon—metal species, which would form via oxidative addition of the metal complexes into the carbon—halogen bonds, also excludes the coordination mechanism. 

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