Synthesis, reactions, and crystal structures of carbonyl-free hydride-bridged mixed organotransition metal derivatives of bis(phosphine)-rhodium(III) or -iridium(III) cations with dihydridobis(η5-cyclopentadienyl)-molybdenum and tungsten

Abstract

The Lewis bases [MH₂(η⁵-C₅H₅)₂](M = MO or W) displace acetone from the labile complex [RhH₂(PPh₃)₂(OCMe₂)₂][PF₆] to give [(PPh₃)₂Rh(µ-H)₂M(η₅-C₅H₅)₂][PF₆] which are readily cleaved by pyridine or HCl and undergo H/D exchange at the cyclopentadienyl rings under mild conditions. The tungsten product (3b) is monoclinic, space group P2₁/c, a= 12.511(1), b= 9.273(1), c= 36.036(6)Å, β= 98.98(1)°, and Z= 4.6 052 Observed reflections having l/σ(l) 3.0 were refined to R= 0.039. The metal atoms are linked by two bridging H atoms, and have Rh-W = 2.7206(7)Å. The tungsten atom has the normal W(η⁵-C₅H₅)₂ geometry (dihedral angle 136°) and the rhodium atom has a square-planar co-ordination. Reaction of [MH₂(η⁵-C₅H₅)₂](M = MO or W) with [IrH₂(PPh₃)₂(OCMe₂)₂][PF₆] gives [(PPh₃)₂Hlr(µ-H)₂(µ-σ:1–5-η₅-C₅H₄)M(η-C₅H₅)][PF₆]. Intermediate formation of [(PPh₃)₂H₂Ir(µ-H)₂M(η⁵-C₅H₅)₂]⁺ is observed, and kinetic parameters have been determined for the C–H insertion reaction. Hydride bridge cleavage of the product (M = W) occurs reversibly with ligands such as pyridine and acetonitrile, but dppe [1,2-bis(diphenylphosphino)ethane] also displaces PPh₃ to give [(PPh₃)(dppe)Hlr(µ-H)(µ-σ:1–5-η-C₅H₄)WH(η₅-C₅H₅)][PF₆]. This is monoclinic, space group P2₁/n, a= 13.573(2), b= 19.979(3), c= 19.546(3)Å, β= 99.53(1)°, and Z= 4. 7 474. Observed reflections were refined to R= 0.035. The metal atoms each have one terminal H atom and are linked by one bridging H, with W-Ir = 3.0771(7)Å. The metallated cyclopentadienyl ring has Ir-C = 2.073(8)Å. The geometry about W is similar to that in complex (3b)(dihedral angle 142°) and that about Ir is very distorted octahedral.