Conversion of a Monodentate Amidinate-Germylene Ligand into Chelating Imine-Germanate Ligands (on Mononuclear Manganese Complexes)

The unprecedented transformation of a terminal twoelectron-donor amidinate-germylene ligand into a chelating threeelectron-donor K-2-N,Ge-imine-germanate ligand has been achieved by treating the manganese amidinate-germylene complex [MnBr{Ge-((i)Pr(2)bzam)Bu-t}(CO)(4)] (1; (i)Pr(2)bzam = N,N'-bis(isopropyI)-benzamidinate) with LiMe or Ag[BF4]. In these reactions, which afford [Mn{k(2)Ge,N-GeMe((i)Pr(2)bzam)Bu-t)(CO)(4)] (2) and [Mn{k(2)Ge,N-GeF-((i)Pr(2)bzam)Bu-t}(CO)(4)] (3), respectively, the anionic nucleophile, Me- or F-, ends on the Ge atom while an arm of the amidinate fragment migrates from the Ge atom to the Mn atom. In contrast, the reaction of 1 with AgOTE (OTf = triflate) leads to [Mn(OTf{Ge((i)Pr(2)bzam)Bu-t}(CO)(4)] (4), which maintains intact the amidinate-germylene ligand. Complex 4 is very moisture-sensitive, leading to [Mn-2{mu-(KGe2)-Ge-4,O-2-(Ge2Bu2)-Bu-t(OH)(2)O}(CO)(8)] (5) and [(i)Pr(2)bzamH(2)]OTf (6) in wet solvents. In 5, a novel digermanate(II) ligand, [Bu-t(OH)GeOGe(OH)Bu-t](2-), doubly bridges two Mn(CO)(4) units. The structures of 1-6 have been characterized by spectroscopic (IR, NMR) and single-crystal X-ray diffraction methods.