Synthesis, molecular structure, and reactivity of Iridium(I) and Iridium(III) complexes formed by coordination and C−H activation of the substituted arenes C6H5CH2CH2PiPr2 and C6H5OCH2CH2PtBu2

Abstract

The dimer [Ir(ο-Cl)(C8H14)2]2 (1) reacts with AgPF6 in acetone to give the bis(acetone) adduct cis-[Ir(acetone)2(C8H14)2] PF6 (2), which upon treatment with iPr2PCH2CH2C6H5 (L1) affords the half-sandwich-type complex [(η6-L1-κ-P)Ir(C8H14)] PF6 (3). The methoxy-bridged dimer [Ir(ο-OMe)(C8H12)]2 (4) gives upon treatment with the phosphonium salt L1·HBF4 the compound [Ir(C8H12)(acetone)(L1-κ-P)] BF4 (5), whereas with L2·HBF4 (L2 = tBu2PCH2CH2-OC6 H5) the bis(chelate) complex [Ir(C8H12)(L2-κ2-O,P)] BF4 (6) is generated. Both 5 and 6 react with hydrogen in acetone to yield the dihydridoiridium(III) derivatives [(η6-L1- κ-P)IrH2]BF4 (7) and [(η6-L2-κ-P)IrH2]BF4 (8), respectively. Compounds 7 and 8 react with excess ethene or propene to give the iridium(I) olefin complexes [(η6-L1-κ-P)Ir (CH2=CHR)]BF4 [R = H (9), Me (11)] and [(η6-L2-κ-P)Ir(CH2=CHR)] BF4 [R = H (10), Me (12)], which in the presence of H2 regenerate the dihydrido precursors. The reaction of 7 with 2 equiv of PhC≡ CPh affords the π-alkyne complex [(η6-L1-κ-P)Ir(PhC≡CPh]BF4 (14) via the stilbene derivative [(η6-L1-κ-P)Ir (Z-PhCH=CHPh)]BF4 (13) as an intermediate. Compound 13 can be isolated upon treatment of 11 with Z-stilbene and has been characterized crystallographically. The reactions of 7 and 11 with acetonitrile lead to the cleavage of the arene-metal bond and afford the octahedral iridium(III) complexes [IrH2(NCCH3)3(L1- κ-P)]BF4 (15) and [IrH(C6H4 CH2CH2PiPr2-κ2-C,P) (NCCH3)3]BF4 (16), respectively. Treatment of the C-H activation product 16 with H2 yields 15. The X-ray crystal structure analysis of 16 reveals that the Ir(NCCH3)3 fragment possesses the fac configuration.