Controlling Catenation in Germanium(I) Chemistry through Hemilability

摘要

We present a novel approach for constructing chains of Group 14 metal atoms linked by unsupported metal-metal bonds that exploits hemilabile ligands to generate unsaturated metal sites. The formation/nature of catenated species (oligo-dimetallynes) can be controlled by the use of (acidic/basic) "protecting groups" and through variation of the ligand scaffold. Reduction of (ArGeCl)-Ge-NiPr2 (Ar-NiPr2=2,6-((Pr2NCH2)-Pr-i)(2)C6H3)-featuring hemilabile (NPr2)-Pr-i donors-yields ((ArGe)-Ge-NiPr2)(4) (2), which contains a tetrameric Ge-4 chain. 2 represents a novel type of a linear homo-catenated Ge-I compound featuring unsupported E-E bonds. Trapping experiments reveal that a key structural component is the central two-way Ge=Ge donor-acceptor bond: reactions with IMe4 and W(CO)(5)(NMe3) give the base- or acid-stabilized digermynes ((ArGe)-Ge-NiPr2(IMe4))(2) (4) and ((ArGe)-Ge-NiPr2{W(CO)(5)})(2) (5), respectively. The use of smaller N-donors leads to stronger Ge-N interactions and quenching of catenation behaviour: reduction of (ArGeCl)-Ge-NEt2 gives the digermyne ((ArGe)-Ge-NEt2)(2), while the unsymmetrical system (ArGeGeArNiPr2)-Ge-NEt2 dimerizes to give tetranuclear ((ArGeGeArNiPr2)-Ge-NEt2)(2) through aggregation at the (NPr2)-Pr-i-ligated Ge-I centres.