Activation of Aliphatic Ethers by TpMe2Ir Compounds: Multiple C−H Bond Activation and C−C Bond Formation

10 páginas, 4 figuras, 1 tabla, 8 esquemas.Benzene solutions of the unsaturated fragment TpMe2Ir(C6H5)2 (1), generated in situ from either TpMe2Ir(C2H4)2 or TpMe2Ir(C6H5)2(N2), react with methyl ethers MeOBut, MeOBun, and MeOCH2CH2OMe to give the organometallic hydride carbene products TpMe2(H)2( C(H)OR) 4 (R = But, 4a; Bun, 4b; CH2CH2OMe, 4c) along with benzylic ethers C6H5CH2OR 5. The overall reaction is very complex and involves the participation of two molecules of the ether, MeOR, and one of benzene per molecule of the iridium precursor. The latter induces multiple C−H bond cleavage along with the formation of a new C−C bond. Hydride carbenes of composition TpMe2Ir(H)(C6H5)(C (H)OR) (2) are early intermediates of this reaction. They can be shown to undergo a reversible 1,2-H shift between the metal atom and the carbene carbon atom, until eventually β-H elimination from the Ir−C6H5 unit allows the C−C coupling through a nonisolable benzyne intermediate. Me−OR bond cleavage, although somewhat more energetically demanding than C−H activation, can also occur and has been demonstrated in the reaction of 1 with Me−OBun, which permits the isolation of the hydride n-propyl carbonyl complex TpMe2Ir(H)(CH2CH2CH3)(CO), 10b.Financial support from the Spanish Ministerio de Educación y Ciencia (MEC) (CTQ2004-00409/BQU, FEDER support, and HU2003-039) and from the Junta de Andalucía, and EU COST Action WD-D17-003 is acknowledged. A.G.P. and L.L.S. thank the MEC for a grant.Peer reviewe