Generation of Metallacyclic Structures from the Reactions of Vinyl Ethers with a Tp^Me2Ir^III Compound

The vinyl ethers CH2CHOEt and CH2CHOPrn react with the IrIII fragment [TpMe2Ir(C6H5)2] [1; TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate] with the formation of unusual metallacyclic structures. Each of the ethers gives rise to three different metallacyclic units in complexes 2−4. Compounds 2are iridacyclopentenes that contain a chelating organic ligand with alkyl and carbene termini, {Ir[C(OR)CH2CH(OR)CH2]} (R = Et, Prn), resulting from the C−C coupling of two molecules of the ether, following prior vinylic C−H activation in one of them. They readily eliminate a molecule of the respective alcohol, ROH, in an acid-catalyzed process that leads to metallacyclopenta-1,3-diene units in 4 {Ir[C(OR)CHCHCH2]}. Complexes 3 have a more complex metallacyclic structure resulting from tridentate coordination of a formally dianionic ligand that possesses alkyl, alkoxide, and carbene functionalities. Generation of this ligand involves the participation of two molecules of the vinyl ether, with one of them undergoing Cvinyl−O bond cleavage. The metallacyclic units that define the molecular structures of 2−4 have been unequivocally characterized by X-ray crystallography.