Metal—ligand bonds insertion reactions with

A quite spectacular insertion reaction of the earbene analogues 1 and 2 into transition metal ligand bonds is found with nickelocene [NiCp2] (Eq. 15). ... 

Example Selective activation of C-H bonds is rarely observed in saturated alkyl groups, but the iridium complex 1 does react by C-H insertion of the metal into a ligand bond upon treatment with LiBr in solution. The reaction can be tracked by LT-FAB-MS (Fig. 9.17). A decreasing intensity of the molecular ion of 1, m/z 812.4, and increasing of 2, m/z 856.4, indicate the progress of this reaction. Furthermore, the halogen exchange is indicated by the isotopic pattern. 

Organometallic Niobium ) and Tantalum ) Compounds. Reports this year have concerned two main areas of interest the preparation of alkyl-niobium and tantalum halides and their reactions with donor ligands, and insertion reactions into methyl-metal bonds. The first examples of monomethyl niobium and tantalum compounds have been prepared by the low-temperature methylation of the appropriate halides... 

The P-P bond still present in 127 readily undergoes insertion reactions with various reagents, e.g., to afford the products 130-132 (Scheme 5)128. In addition, the phosphorus atoms can also serve as ligands in transition metal complexes. The complexes 133 and 134 with one or two W(CO)s fragments are two typical examples126 (Scheme 5). 

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... 

The pincer like diamino functionalised carbene ligand stabilises the group 4 metal sufficiently to perform a few very interesting insertion reactions with the M-Me bond. The reactions were performed with the hafnium rather than the zirconium complexes [113]. Small molecules used for these insertion reactions include isonitriles (aryl and alkyl) and CO (see Figure 4.36). Reaction of the hafnium carbene dimethyl complex with xylyl-isonitrile results in addition of this excellent donor ligand and subsequent insertion into the Hf-Me... 

Oxidative addition occurs when the metal inserts into the C—H bond to give new hydride and hydrocarbyl ligands (Scheme 11.8). The formation of two new metal-ligand bonds requires four electrons. Two electrons are derived from the C—H bond and two electrons are donated by the metal center. Thus, this process results in a formal two-electron oxidation of the metal center (Scheme 11.9). The C—H oxidative addition with a single metal center requires that the metal precursor have access to two vacant coordination sites and possess at least one lone pair of electrons. Such reactions... 

In the context of C—H bond insertion reactions involving metal nitrenoids, Mn and Ru catalysts hold important positions. These catalysts often contain multidentate ligands, such as porphyrins and salen ligands. With these catalysts, the enantioselectivity can be well controlled in many cases. 

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