Bulky formamidinate complexes of lithium:: the first examples of η2:η1-C=N,N′ metal amidinate coordination

The lithium complexes [Li{N(Ar) C(H) N(Ar)}(pmdeta)], where Ar = 2,6- R2C6H3 (R = Me ( 1), Et ( 2) and Pr-i ( 3)) and pmdeta = N, N, N', N '', N ''-pentamethyldiethylenetriamine, have been synthesised and their solid state structures determined by X-ray methods. Compounds 1 - 3 comprise a Li( pmdeta) centre coordinated by a bulky formamidinate in either the E-syn or E-anti isomeric form. The structures of compound 3 and one unique molecular unit of compound 1 ( E-anti isomer) display coordination of the pendant amidinate imine, and can therefore be considered the first examples of eta(2):eta(1)- C=N, N' metal amidinate coordination.