Novel rhodate and iridate complexes containing C,N chelating arylamine ligand systems

The synthesis is described of a series of new iridate and rhodate complexes Li(L-C,N)₂M(cod) (M = Rh, Ir; cod = cycloocta-1,5-diene) containing the ortho-chelating, mono-anionic, arylamine ligands L = C₆H₄CH₂NR₂-2 (R = Me, Et), C₆H₃CH₂NMe₂- 2-Me-5, C₆H₄CH(Me)NMe₂-(R)-2 or C₆H₄CH₂NMe(^tBu)-2. The synthetic procedure for the -ate complexes from [MCl(cod)] ₂ depends on the solubility of the starting aryllithium compound in benzene-an indirect effect of the bulky organic group on the N-donor atom. All the -ate complexes are formed diastereoselectively (and in the case of C₆H₄CH(Me)NMe₂-(R)-2, enantioselectively). ¹H and ¹³C NMR spectroscopies show the -ate complexes to be monomeric, heterobimetallic species. The ¹³C NMR data show clearly that C_ipso is bridging between the late transition metal and the lithium centre. Consequently, this C_ipso atom is chiral, and its configuration is stabilized by intramolecular coordination of the N-donor atom of the ortho-amine substituent. The -ate complexes are fluxional with differences in fluxionality (which involve N-dissociation/association, pyramidal inversion at N and rotation around the C_benzyl-N bond) that can be attributed to differences in the bulk of the groups on the nitrogen atom.