Cationic iridium complexes of the Xantphos ligand. Flexible coordination modes and the isolation of the hydride insertion product with an alkene

Journal article

Reaction of the Ir(I)-Xantphos complex [Ir(κ2-Xantphos) (COD)][BArF4] (Xantphos = 4,5-bis(diphenylphosphino)-9,9- dimethylxanthene, ArF = C6H3(CF 3)2) with H2 in acetone or CH 2Cl2/MeCN affords the Ir(III)-hydrido complexes [Ir(κ3-Xantphos)(H)2(L)][BArF4], L = acetone or MeCN, whereas in non-coordinating CH 2Cl2 solvent dimeric [Ir(κ3-Xantphos)(H) (μ-H)]2[BArF4]2 is formed. A common intermediate in these reactions that invokes a (σ, η2-C8H13) ligand is reported. Addition of excess tert-butylethene (tbe) to [Ir(κ3-Xantphos)(H) 2(MeCN)][BArF4] results in insertion of a hydride into the alkene to form [Ir(κ3-Xantphos)(MeCN)(CH 2CH2C(CH3)3)(H)][BAr F4], an Ir(III) alkyl-hydrido-Xantphos complex. This reaction is reversible, and heating (80 °C) results in the reformation of [Ir(κ3-Xantphos)(H)2(MeCN)][BArF4] and tbe. These complexes have been characterised by NMR spectroscopy, ESI-MS and single-crystal X-ray diffraction. They show variable coordination modes of the Xantphos ligand: cis-κ2-P,P, fac-κ3-P,O,P and mer-κ3-P,O,P with the later coordination mode like that found in related PNP-pincer complexes. © 2011 Elsevier B.V. All rights reserved.

Authors: Pontiggia, A; Chaplin, AB; Weller, A

• Publication status: Published
• Journal: JOURNAL OF ORGANOMETALLIC CHEMISTRY
• Volume: 696
• Issue: 17
• Pages: 2870-2876
• Publication date: 2011-08-15
• DOI: 10.1016/j.jorganchem.2011.01.036
• ISSN: 0022-328X
• Language: English
• Keywords: Phosphine; X-ray; Hydride; Xantphos; Pincer; Iridium