Synthesis of cationic half-sandwich rhodium(I) complexes of 1,4,7-trithiacyclononane ([9]aneS3). The single-crystal structures of [Rh([9]aneS3)(C2H4)2]PF6, [Rh([9]aneS3)(C8H12)]BF4 and [Rh([9]aneS3)(C4H6)]PF6·0.25OEt2

Abstract

Reaction of [Rh₂L₂L′₂Cl₂]{L,L′= C₂H₄, ½cod or ½nbd; L = C₂H₄, L′= PPrⁱ₃ or P(C₆H₁₁)₃; cod = cycloocta-1,5-diene, nbd = norbornadiene (bicyclo[2.2.1]hepta-2,5-diene)} with 2 molar equivalents of 1,4,7-trithiacyclononane([9]aneS₃) in the presence of NaBF₄ or NH₄PF₆ at 293 K, or treatment of [Rh(C₄H₆)₂Cl] or [Rh(CO)Cl(PPh₃)₂] with 1 molar equivalent of [9]aneS₃ and NH₄PF₆ afforded [Rh([9]aneS₃)L(L′)]X [L,L′= C₂H₄, ½cod, ½nbd or ½C₄H₆; L = C₂H₄, L′= PPrⁱ₃, P(C₆H₁₁)₃; L = CO, L′= PPh₃; X = BF₄ or PF₆] in moderate yields. The crystal structure of the complex [Rh([9]aneS₃)(C₂H₄)₂]PF₆ has been determined: monoclinic, space group P2₁/n, a= 11.487(3), b= 9.459(3), c= 15.745(6)Å, β= 105.54(3)° and Z= 4. The cation adopts a trigonal-bipyramidal geometry, with one equatorial and one axial ethene ligand. The complex [Rh([9]aneS₃)(cod)]BF₄ crystallises in the triclinic space group P with a= 11.491(13), b= 12.803(6), c= 13.377(15), α= 88.12(7), β= 70.30(8), γ= 74.68(7)° and Z= 4. The two molecules in each asymmetric unit also adopt distorted trigonal-bipyramidal stereochemistries, with the conformation in molecule 1 being related to that of molecule 2 by a 6° rotation of the macrocyclic ring about the central M–[9]aneS₃ axis. The complex [Rh([9]aneS₃)(C₄H₆)]PF₆ crystallises in the monoclinic space group C2/c with a= 18.612(6), b= 8.679(5), c= 23.756(5), β= 96.844(18)° and Z= 8. The structure shows a quasi-square-pyramidal complex cation. Treatment of [Rh₂(CO)₄Cl₂] with [9]aneS₃ and NH₄PF₆ yielded the dimeric complex [Rh₂([9]aneS₃)₂(µ-CO)₃][PF₆]₂. Reaction of [Rh([9]aneS₃)(C₂H₄)L]⁺[L = C₂H₄ or P(C₆H₁₁)₃] with halogenated substrates afforded insoluble [Rh([9]aneS₃)X₃](X = Cl or I), while no reaction was observed with C₆H₆ or SiEt₃H. Spectroscopic, structural and chemical evidence indicates that the [Rh([9]aneS₃)]⁺ fragment has a high electrophilic character.