Pentafluorophenylphosphine complexes of rhodium(I): extended X-ray absorption fine structure studies of [{Rh[PPhx(C6F5)3 –x]2(µ-CI)}n](x= 0–2) and [{Rh[(C6F5)2PCH2CH2P(C6F5)2](µ-CI)}2]. Crystal structures of [RhCl(PPh3){(C6F5)2PCH2CH2P(C6F5)2}]·C4H8O and (C6F5)2PCH2CH2P(C6F5)2

Abstract

The NMR spectroscopic properties of the rhodium pentafluorophenylphosphine complexes [{Rh[PPh_x(C₆F₅)_{3 –x}]₂(µ-Cl)}_n](x= 0 1, 1 2 or 2 3) and trans-[Rh{PPh_x(C₆F₅)_{3 –x}}₂Cl(CO)](x= 0 5, 1 6 or 2 7) have been investigated. The new complexes [{Rh[(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂](µ-Cl)}₂]4 and cis-[Rh{(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂}Cl(CO)]8 have been prepared. A rhodium K-edge extended X-ray absorption fine structure (EXAFS) study of complexes 1–4 has been performed, and confirms that complexes 2, 3 and 4 are dimers with each Rh ⋯ Rh′ distance bridged by two chlorides [d(Rh–P) 2.16–2.21, d(Rh–Cl) 2.38–2.39, d(Rh ⋯ Rh′) 3.50–3.58 Å], whereas complex 1 is a polymer with each Rh ⋯ Rh′ distance bridged by one chloride [d(Rh–P) 2.18, d(Rh–Cl) 2.36, d(Rh ⋯ Rh′) 4.30 Å]. The reaction between [{Rh[(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂](µ-Cl)}₂] and PPh₃ yields the four-co-ordinate mononuclear rhodium(I) complex [RhCl(PPh₃){(C₆F₅)₂PCH₂CH₂P(C₆F₅)₂}]9. The crystal structures of 9 and of (C₆F₅)₂PCH₂CH₂P(C₆F₅)₂ have been determined by X-ray crystallography. Complex 9 crystallizes in the monoclinic space group P2₁/c with a= 12.707(2), b= 17.066(2), c= 22.003(3)Å, β= 101.41(1)°, z= 4. Refinement gave final R₁ and wR₂ values of 0.0429 and 0.0715 for 5193 observed reflections. The geometry about the rhodium atom is distorted-square planar and there is a short distance between an ortho-hydrogen atom of the triphenylphosphine ligand and the rhodium atom (2.699 Å) indicative of an agostic interaction. The phosphine (C₆F₅)₂PCH₂CH₂P(C₆F₅)₂ crystallizes in the triclinic space group P with a= 5.833(1), b= 10.011(2), c= 11.514(4)Å, α= 75.25(2), β= 88.69(2), γ= 84.28(2)°, z= 1. Refinement gave final R₁ and wR₂ values of 0.0482 and 0.0987 respectively for 1339 observed reflections.