Trimethylenemethane metal complexes. Part 1. Synthesis of ruthenium, osmium, rhodium, and iridium complexes

Abstract

2-[(Methylsulphonyloxy)methyl]-3-trimethylsilylprop-1-ene, available from 2-methylprop-2-en-1-ol, serves as a new entry into trimethylenemethane (tmm) metal complexes. Reaction with low-valent metal complexes affords the first tmm metal complexes of ruthenium, osmium, rhodium, and iridium: [MCl(NO)(PPh₃)(η⁴-tmm)](M = Ru or Os), [Os(CO)₂(PPh₃)(η⁴-tmm)], [MCI(PPh₃)₂(η⁴-tmm)](M = Rh or Ir), and [IrX(CO)(L)(η⁴-tmm)](X = CI, L = PPh₃ or AsPh₃; X = Br, L = PPh₃). The desilylation of an η³-allyl intermediate rationalises the results and has been verified by the reaction of sodium fluoride with [Rh{η³-CH₂C(CH₂SiMe₃)CH₂}Cl(CO)(PMe₂Ph)₂] BPh₄ in aqueous methyl cyanide which gave the complex [Rh(CO)(PMe₂Ph)₂(η⁴-tmm)] BPh₄ in quantitative yield. N.m.r. data (¹H, ¹³C-{¹H}) are reported and variable-temperature ¹H n.m.r. spin-magnetisation transfer experiments have been used to set a lower limit of ca. 90 kJ mol^–1 for the activation energies for trimethylenemethane rotation.