Iridapyrrole complexes

A further significant feature of the ethyl-vinyl complexes Tp Ir(C2H4R)(CH = CHR)(NCR ) (R = Me (292), (473), (390), R = Bu (387)) and, in acetonitrile, 198, is their propensity for intramolecular [3 + 2] cycloaddition of the alkenyl and nitrile ligands.This affords iridapyrrole complexes 474, 475, 545, 546 and 547 (Chart 9 discussed in Section II-E) for which fully delocalised aromatic structures have been assigned on the basis of NMR spectroscopic data. Besides this study the hydrides 201 and 204 were found to react with a series of aldehydes, resulting in formation of the alkoxide-alkene chelates 244-247 (Scheme 13, Section III-B.l). 

Fig. 11. Molecular structure of iridapyrrole complex 493. Hydrogen atoms omitted.

The final examples are obtained from the complexes Tp Ir(CH2CH2R)(CH = CHR)(NCMe) (R = H (292), Me (473)), not via C-H activation vide supra), but rather by intramolecular cycloaddition of the acetonitrile and vinyl ligands. Thus, under thermal activation the iridapyrroles 474 and 475 can be prepared, each of which retains the d-alkyl ancillary ligand (Schemes 12 and 40). ... 

It should be noted that while a number iridapyrroles exist (Section II-E) their protonation does not universally afford isolable alkylidenes, particularly those complexes comprising an alkyl ligand in place of the hydride, which typically afford chelating Ti-alkene complexes. 

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