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

The
unprecedented transformation of a terminal two-electron-donor amidinate–germylene
ligand into a chelating three-electron-donor κ2-N,Ge-imine–germanate ligand has been achieved by
treating the manganese amidinate–germylene complex [MnBr­{Ge­(iPr2bzam)tBu}­(CO)4] (1; iPr2bzam = N,N′-bis­(isopropyl)­benzamidinate)
with LiMe or Ag­[BF4]. In these reactions, which afford
[Mn­{κ2Ge,N-GeMe­(iPr2bzam)tBu}­(CO)4] (2) and [Mn­{κ2Ge,N-GeF­(iPr2bzam)tBu}­(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 AgOTf (OTf = triflate) leads to [Mn­(OTf)­{Ge­(iPr2bzam)tBu}­(CO)4] (4), which maintains intact the amidinate–germylene
ligand. Complex 4 is very moisture-sensitive, leading
to [Mn2{μ–κ4Ge2,O2-Ge2tBu2(OH)2O}­(CO)8]
(5) and [iPr2bzamH2]­OTf (6) in wet solvents. In 5,
a novel digermanate­(II) ligand, [tBu­(OH)­GeOGe­(OH)tBu]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.