Formation and structure of the first metal complexes comprising amidino­guanidinate ligands

The first metal complexes comprising amidino­guanidinate ligands have been prepared and structurally characterized, namely bis­[μ-N,N′,N′′,N′′′-tetraisopropyl-1-(1-butyl­amidinato)guanidinato-κ(3) N (1),N (2):N (2)]bis­[(tetra­hydro­furan)lithium], [Li(2)(C(18)H(37)N(4))(2)(C(4)H(8)O)(2)], (2), and [bis­(tetra­hydro­furan)­lithium]-di-μ-chlorido-{(N,N′-di­cyclo­hexyl-1-butyl­amidinato-κ(2) N (1),N (2))[N,N′,N′′,N′′′-tetra­cyclo­hexyl-1-(1-butyl­amidinato)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 amidino­guanidinate precursors Li[(n)BuC(=NR)(NR)C(NR)(2)] [1: R = Cy (cyclo­hex­yl), 2: R = (i)Pr) were obtained by treatment of N,N′-diorganocarbodi­imides, R—N=C=N—R (R = (i)Pr, Cy), with 0.5 equivalents of n-butyl­lithium 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 amidino­guanidinate ligand.