Pentamethylcyclopentadienyl-rhodium and -iridium complexes. Part 26. Dicationic η⁵-aniline and η⁶-anisole complexes

Abstract

The preparation and properties of a series of dicationic aniline and substituted aniline complexes [M(C5Me5)(p-R1C6H4NR2R3)][PF6]2(M = Rh or Ir; R1= R2= R3= H; R1= R2= H, R3= Me or Ph; R1= H, R2= R3= Me; R1= R2= R3= Me; R1= Me, R2= R3= H) are described. From the 1H and 13C n.m.r. spectra and the i.r. spectra it is concluded that a 6-imino-1–5-η-cyclohexadienyl form is a significant contributor to the bonding in these complexes and accounts, for example, for the barrier to rotation about the C–N bonds observed in the N-methylaniline and diphenylamine complexes. This was confirmed by the single-crystal X-ray structure of [Rh(C5Me5)(PhNHMe)][PF6]2 even though disorder and rather large estimated standard deviations preclude very accurate bond-length and bond-angle measurements. The related anisole complexes [M(C5Me5)(PhOMe)][PF6]2 were also prepared. Their n.m.r. spectra are not characteristic of an η5-bonded benzene ring, and it is proposed that the anisole is η6-bonded. The rhodium–anisole complex is labile and the anisole is easily displaced by acetone; it is concluded that OMe does not significantly stabilise η6-arene binding in these complexes in contrast to methyl which does.