Preparation and fluxional behaviour of 4-substituted 2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane hydride complexes of the cobalt triad

Abstract

Caged phosphite complexes of the type [MH{P(OCH₂)CPrⁿ}₄](M = Co, Rh, or Ir) have been synthesized. These complexes are stereochemically non-rigid on the n.m.r. time scale at 25 °C. However, for the rhodium and iridium analogues, near-limiting and limiting slow-exchange spectra respectively, corresponding to a structure with C_3v, symmetry, have been obtained at low temperatures. Activation parameters have been calculated from lineshape analyses. Mixed-ligand complexes of the types [M(CO)H(PPh₃)₂{P(OCH₂)₃CX}](M = Rh or Ir; X = Prⁿ or NO₂) and [M(CO)H(PPh₃){P(OCH₂)₃CX}₂](X = Prⁿ, Ph, or NO₂) have also been prepared. For the latter complexes, n.m.r. evidence suggests that more than two isomers are involved.