Acta Crystallographica Section E: Crystallographic Communications (Oct 2024)

Crystal structures of the (η2:η2-cycloocta-1,5-diene)(η6-toluene)iridium(I) cation and μ-chlorido-iridium(III) complexes of 2-(phosphinito)- and 2-(phosphinomethyl)anthraquinone ligands

  • Sachin Thackeray,
  • James Mahoney,
  • Ashleigh Arrington,
  • Miles Wilklow-Marnell,
  • William W. Brennessel

DOI
https://doi.org/10.1107/S2056989024008922
Journal volume & issue
Vol. 80, no. 10
pp. 1101 – 1109

Abstract

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When reacted in dry, degassed toluene, [Ir(COD)Cl]2 (COD = cycloocta-1,5-diene) and 2 equivalents of 2-(di-tert-butylphosphinito)anthraquinone (tBuPOAQH) were found to form a unique tri-iridium compound consisting of one monoanionic dinuclear tri-μ-chlorido complex bearing one bidentate tBuPOAQ ligand per iridium, which was charge-balanced by an outer sphere [Ir(toluene)(COD)]+ ion, the structure of which has not previously been reported. This product, which is a toluene solvate, namely, (η2:η2-cycloocta-1,5-diene)(η6-toluene)iridium(I) tri-μ-chlorido-bis({3-[(di-tert-butylphosphanyl)oxy]-9,10-dioxoanthracen-2-yl}hydridoiridium(III)) toluene monosolvate, [Ir(C7H8)(C8H12)][Ir2H2(C22H24O3P)2Cl3]·C7H8 or [Ir(toluene)(COD)][Ir(κ-P,C-tBuPOAQ)(H)]2(μ-Cl)3]·toluene, formed as small orange platelets at room temperature, crystallizing in the triclinic space group P\overline{1}. The cation and anion are linked via weak C—H...O interactions. The stronger intermolecular attractions are likely the offset parallel π–π interactions, which occur between the toluene ligands of pairs of inverted cations and between pairs of inverted anthraquinone moieties, the latter of which are capped by toluene solvate molecules, making for π-stacks of four molecules each. The related ligand, 2-(di-tert-butylphosphinomethyl)-anthraquinone (tBuPCAQH), did not form crystals suitable for X-ray diffraction under analogous reaction conditions. However, when the reaction was conducted in chloroform, yellow needles readily formed following addition of 1 atm of carbon monoxide. Diffraction studies revealed a neutral, dinuclear, di-μ-chlorido complex, di-μ-chlorido-bis(carbonyl{3-[(di-tert-butylphosphanyl)oxy]-9,10-dioxoanthracen-2-yl}hydridoiridium(I)), [Ir2H2(C23H26O2P)2Cl2(CO)2] or [Ir(κ-P,C-tBuPCAQ)(H)(CO)(μ-Cl)]2, Ir2C48H54Cl2O6P2, again crystallizing in space group P\overline{1}. Offset parallel π–π interactions between anthraquinone groups of adjacent molecules link the molecules in one dimension.

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