Organometallic macrocyclic chemistry: synthesis of cationic half-sandwich iridium(I) complexes of 1,4,7-trithiacyclononane ([9]aneS3). Crystal structures of [Ir([9]aneS3)(C2H4)2]PF6, [Ir([9]aneS3)(C8H12)]PF6 and [Ir([9]aneS3)(C4H6)]PF6·0.5Et2O

Abstract

Reaction of [Ir₂L₄Cl₂](L = C₈H₁₄ or 0.5C₈H₁₂) or [IrL₄Cl](L = C₂H₄ or 0.5C₄H₆) with 1 molar equivalent of 1,4,7-trithiacyclononane ([9]aneS₃) and NH₄PF₆ in acetone, tetrahydrofuran or CH₂Cl₂ under N₂ at 293 K afforded the complexes [Ir([9]aneS₃)L₂]PF₆. The single-crystal structures of [Ir([9]aneS₃)(C₂H₄)₂]PF₆ and [Ir([9]aneS₃)(C₈H₁₂)]PF₆ have been determined and show that the complex cations adopt distorted five-co-ordinate geometries. For [Ir([9]aneS₃)(C₂H₄)₂]PF₆, Ir–S(1) 2.317(2), Ir–S(4) 2.402(2), Ir–S(7) 2.384(2), Ir–C(11) 2.173(9), Ir–C(12) 2.194(10), Ir–C(13) 2.146(8), Ir–C(14) 2.118(7), C(11)C(12) 1.366(13) and C(13)C(14) 1.443(11)Å. For [Ir([9]aneS₃)(C₈H₁₂)]PF₆, Ir–S(1) 2.319(5), Ir–S(4) 2.343(4), Ir–S(7) 2.419(4), Ir–C(11) 2.166(14), Ir–C(12) 2.199(14), Ir–C(15) 2.188(15), Ir–C(16) 2.141(15), C(11)C(12) 1.411(19) and C(15)C(16) 1.418(21)Å. The single-crystal structure of [Ir([9]aneS₃)(C₄H₆)]PF₆·0.5Et₂O shows this complex to have a five-coordinate stereochemistry analogous to that adopted by [Fe(CO)₃(C₄H₆)] with Ir–S(1) 2.321(2), Ir–S(4) 2.331(2), Ir–S(7) 2.325(2), Ir–C(11) 2.149(9), Ir–C(12) 2.141(9), Ir–C(13) 2.146(9), Ir–C(14) 2.115(10), C(11)C(12) 1.433(13), C(12)–C(13) 1.381(13) and C(13)C(14) 1.461(14)Å. Variable-temperature ¹H and ¹³C NMR spectroscopic data on [M([9]aneS₃)(C₂H₄)₂]⁺ and [M([9]aneS₃)(C₄H₆)]⁺(M = Rh or lr) are consistent with the highly electrophilic character of the cationic fragments [M([9]aneS₃)]⁺. On the basis of J(C–H) coupling data and of an analysis of bond-length distributions and observed dihedral angles in the complex, the butadiene ligand in [Ir([9]aneS₃)(C₄H₆)]⁺ is assigned as η⁴ bonded but with a significant σ² component.