Dedicated to Professor Jose Barluenga on the occasion of his 60th birthday
The selective activation of CÀH bonds of hydrocarbons and other common organic substrates (such as ethers, amines, and nitriles) is a far-reaching objective of current research in organometallic chemistry. [1] A very valuable reaction is the regioselective activation of two a-CÀH bonds of an ether or amine functionality, RCH 2 X (X OR', NR 2 '), since it constitutes an unused synthetic route to Fischer-type carbenes, M C(R)X. [2] Despite its potential applications, this double CÀH activation 4] is still a rarely observed process. Herein, we wish to report that [Ir(k 3 -Tp Ph )(h 4 -isoprene)] (1; Tp Ph hydridotris(3-phenylpyrazol-1-yl)borate), when treated with substrates such as anisole (MeOPh), N,N-dimethylaniline (Me 2 NPh), tetrahydrofuran (C 4 H 8 O), ethyl phenyl ether (EtOPh), or even diethyl ether (Et 2 O), generates heteroatom-substituted carbene complexes. [4±7] Most significantly, and at variance with somewhat related Cp*Ir systems (Cp* h 5 -Me 5 C 5 ), [7] a-elimination from the activated ether or amine substrate takes place for every case investigated, even if bhydrogen atoms are available.
Recently, it has been shown that [
] when treated with a Lewis base L. Taking advantage of the possibility of precoordination of a substrate and, having additionally demonstrated that [IrTp x (R)(R')] centers (R, R' H, alkyl, aryl; x Me, Ph) activate two a-CÀH bonds of THF, [4b, c, 9] 1 was heated in the presence of THF (80 8C, 4 h). [10] High yields (about 90 %) of a cyclic carbene 2 derived from a molecule of