Group 13 metal(i) and (ii) guanidinate complexes: effect of ligand backbone on metal oxidation state and coordination sphere

Abstract

Reactions of lithium salts of the bulky guanidinate and phosphaguanidinate ligands, [ArNC(ER₂)NAr]⁻ (ER₂ = NPrⁱ₂ (Priso⁻), cis-NC₅H₈Me₂-2,6 (Pipiso⁻) or P(C₆H₁₁)₂ (PGiso⁻); Ar = C₆H₃Prⁱ₂-2,6), with group 13 metal(I) halides have been carried out. All reactions with TlBr led to monomeric thallium(I) complexes, [Tl{ArNC(ER₂)NAr}], in which the ligand chelates the metal in an N,arene-fashion. The reactions with InCl led to mixed results and the isolation of the dimeric indium(II) complexes, [{InCl(Priso)}₂] and [{InCl(Pipiso)}₂], and the monomeric indium(I) species, [In(Pipiso)] and [In(PGiso)]. The ligands of the latter two complexes exhibit differing coordination modes in the solid state, namely N,N′-chelating and N,arene-chelating, respectively. The reactions with “GaI” were less successful and gave only low yields of the poorly characterised gallium(II) complexes, [{GaI(Priso)}₂] and [{GaI(Pipiso)}₂]. This study has shown that the related ligand, [ArNC{N(C₆H₁₁)₂}NAr]⁻ (Giso⁻) is superior for the stabilisation of group 13 metal(I) complexes. The oxidative additions of I₂ or SiMe₃I to one such complex, [Ga(Giso)], yielded the gallium(III) compounds, [GaI₂(Giso)] and [GaI(SiMe₃)(Giso)].