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-<i>N,Ge</i>-imine–germanate ligand has been achieved by treating the manganese amidinate–germylene complex [MnBr­{Ge­(^<i>i</i>Pr₂bzam)^<i>t</i>Bu}­(CO)₄] (<b>1</b>; ^<i>i</i>Pr₂bzam = <i>N</i>,<i>N</i>′-bis­(isopropyl)­benzamidinate) with LiMe or Ag­[BF₄]. In these reactions, which afford [Mn­{κ²<i>Ge,N</i>-GeMe­(^<i>i</i>Pr₂bzam)^<i>t</i>Bu}­(CO)₄] (<b>2</b>) and [Mn­{κ²<i>Ge,N</i>-GeF­(^<i>i</i>Pr₂bzam)^<i>t</i>Bu}­(CO)₄] (<b>3</b>), 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 <b>1</b> with AgOTf (OTf = triflate) leads to [Mn­(OTf)­{Ge­(^<i>i</i>Pr₂bzam)^<i>t</i>Bu}­(CO)₄] (<b>4</b>), which maintains intact the amidinate–germylene ligand. Complex <b>4</b> is very moisture-sensitive, leading to [Mn₂{μ–κ⁴<i>Ge</i>₂<i>,O</i>₂-Ge₂^<i>t</i>Bu₂(OH)₂O}­(CO)₈] (<b>5</b>) and [^<i>i</i>Pr₂bzamH₂]­OTf (<b>6</b>) in wet solvents. In <b>5</b>, a novel digermanate­(II) ligand, [^<i>t</i>Bu­(OH)­GeOGe­(OH)^<i>t</i>Bu]^2–, doubly bridges two Mn­(CO)₄ units. The structures of <b>1</b>–<b>6</b> have been characterized by spectroscopic (IR, NMR) and single-crystal X-ray diffraction methods