Iridium complexes bonding

Rhodium and Iridium rr-Bonded Alkyl and Aryl Complexes. 29,4... 

One most important observation for the mechanistic discussion is the oxidative addition/insertion/reductive elimination processes of the iridium complex (31) (Scheme 1-10) [62]. The oxidative addition of catecholborane yields an octahedral iridium-boryl complex (32) which allows the anti-Markovnikov insertion of alkyne into the H-Ir bond giving a l-alkenyliridium(III) intermediate (34). The electron-... 

The C-C bond-forming coupling of solvent molecules via sp2- and r/ -C-H bond functionalizations can be achieved using an iridium complex based on the TpMe2 ligand (hydridotris(3,5-dimethylpyrazolyl)borate) (Equation (64)).65... 

Remarkable carbon-boron bond-forming reactions are catalyzed by iridium complexes and proceed at room temperature with excellent regioselectivity, governed by steric factors. Heteroarenes are borylated in the 2-position and this reaction is generally tolerant of halide substituents on the arene (Equations (87) and (88)). 

Alkylation of sp3 C-H bonds adjacent to a heteroatom such as nitrogen and oxygen is possible. The early works using tungsten or iridium complexes involved the reaction of dimethylamine with 1-pentene (Equation (29)) and the alkylation of a C-H bond adjacent to oxygen with / r/-butylethylene.34,34a,34b... 

Eisenberg reported product inhibition in the hydrogenation of acetone with a cationic iridium complex [42]. Apparently, the bond between iridium and isopropanol is too strong on account of the cationic nature of the complex (Scheme 44.7). 

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. 

In this review, the recent developments in catalytic functionalization of C-H bonds by iridium complexes will be emphasized. For more information on previous work and their details, there are excellent reviews published recently on C-H bond functionalization by transition metal complexes generally [1-9], as well as with an emphasis on iridium [11, 16]. 

Several iridium-catalyzed dehydrogenations of HCXH (X = O, N) linkages have been reported by pincer-iridium complexes. While these dehydrogenations are not generally considered as C-H bond activations or functionalizations, it is generally not known if they proceed via initial activation of the X-H or C-H bond [65, 66]. 

---