Formation and structure of the first metal complexes comprising amidino-guanidinate ligands.

The first metal complexes comprising amidino-guanidinate ligands have been prepared and structurally characterized, namely bis-[μ-N,N',N'',N'''-tetraisopropyl-1-(1-butyl-amidinato)guanidinato-κ(3)N(1),N(2):N(2)]bis-[(tetra-hydro-furan)lithium], [Li(2)(C(18)H(37)N(4))(2)(C(4)H(8)O)(2)], (2), and [bis-(tetra-hydro-furan)-lithium]-di-μ-chlorido-{(N,N'-di-cyclo-hexyl-1-butyl-amidinato-κ(2)N(1),N(2))[N,N',N'',N'''-tetra-cyclo-hexyl-1-(1-butyl-amidinato)guanidinato-κ(2)N(1),N(2)]holmate(III)}, [HoLiCl(2)(C(4)H(8)O)(2)(C(17)H(31)N(2))(C(30)H(53)N(4))], (3). The novel lithium amidino-guanidinate precursors Li[ (n) BuC(=NR)(NR)C(NR)(2)] [1: R = Cy (cyclo-hex-yl), 2: R = (i) Pr) were obtained by treatment of N,N'-diorganocarbodi-imides, R-N=C=N-R (R = (i) Pr, Cy), with 0.5 equivalents of n-butyl-lithium under well-defined reaction conditions. An X-ray diffraction study of 2 revealed a ladder-type dimeric structure in the solid state. Reaction of anhydrous holmium(III) chloride with in situ-prepared 2 afforded the unexpected holmium 'ate' complex [ (n) BuC(=NCy)(NCy)C(NCy)(2)]Ho[ (n) BuC(NCy)(2)](μ-Cl)(2)Li(THF)(2) (3) in 71% yield. An X-ray crystal structure determination of 3 showed that this complex contains both an amidinate ligand and the new amidino-guanidinate ligand.