16949-48-7Relevant academic research and scientific papers
Four- and five-coordinate complexes of rhodium and iridium containing trifluorophosphine
Bennett,Patmore
, p. 2387 - 2395 (2008/10/08)
Trifluorophosphine displaces coordinated cyclooctene from the complex [RhCl(C8H14)2]2 at room temperature and pressure to give an almost quantitative yield of the dimeric, chloro-bridged complex [RhCl(PF3)2]2, which was previously accessible in only 2.6% yield. Trifluorophosphine also reacts with [IrCl(C8H14)2]2 to give as the final product a five-coordinate complex IrCl(PF3)4, though there is evidence for intermediate mixed cyclooctene-trifluorophosphine complexes. Both these and IrCl(PF3)4 readily decompose on warming to give the new compound [IrCl(PF3)2]2. Metal-metal bonded structures are proposed for [MCl(PF3)2]2 (M = Rh or Ir) in the solid state. The preparation of mononuclear complexes such as M(acac)-(PF3)2 and π-C5H5Rh(PF3)2 is also described. Nmr studies indicate that there is rapid exchange between free and coordinated PF3 at room temperature in planar rhodium(I) complexes but not in π-C5H5Rh(PF3)2. The complexes [RhCl(PF3)2]2 (in the presence of PF3) and IrCl(PF3)4 are reduced by potassium amalgam in ether giving initially the new metal-mercury bonded complexes Hg[M(PF3)4]2 and finally the known salts K[M(PF3)2]. The latter react with [RhCl(PF3)2]2-PF3 or IrCl(PF3)4 to give the dimeric metal-metal bonded complexes Rh2(PF3)8 and Ir2(PF3)8, which probably are structurally similar to the isomer of Co2(CO)8 without bridging CO's. Cleavage of Rh2(PF3)8 with H2 (25°, 1 atm) gives HRh(PF3)4 quantitatively. Five-coordinate metal-metal bonded complexes of general formula RM(PF3)4 [M = Rh or Ir, R = (C6H5)3Sn or (C6H5)3PAu; M = Ir, R = (C6H5)3Pb] can be made by reaction of [M(PF3)4]- with RCl. However there is no reaction between M (PF3)4 and (C6H5)3SiCl or (C6H5)3GeCl, indicating that Rh(PF3)4- and Ir(PF3)4- are poorer nucleophiles than Co(CO)4-. A more general route to compounds containing bonds between rhodium or iridium and a group IV element is the reaction between M2(PF3)8 and a group IV hydride: M2(PF3)8 + RH → RM(PF3)4 + HM(PF3)4 [R = (C6H5)3Si, (C2H5O)3Si, Cl3Si, or (C6H5)3Ge]. With triphenylgermane there is a subsequent slow reversible reaction HM(PF3)4 + RH ? H2 + RM(PF3)4, while with (C2H5O)3SiH and HSiCl3, this reaction goes to completion. Kinetic studies indicate both reactions to be bimolecular, the rates depending on the transition element (Rh > Ir), the group IV element (Ge > Si), and the substituents on the group IV atom (Cl ～ C2H5O > C6H5). The reactions are compared with those believed to occur in the hydrosilation of Co2(CO)8.
