Controlling Catenation in Germanium(I) Chemistry through Hemilability.

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 Ar GeCl (Ar =2,6-( Pr NCH ) C H )-featuring hemilabile N Pr donors-yields (Ar Ge) (2), which contains a tetrameric Ge chain. 2 represents a novel type of a linear homo-catenated Ge 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 IMe and W(CO) (NMe ) give the base- or acid-stabilized digermynes (Ar Ge(IMe )) (4) and (Ar Ge{W(CO) }) (5), respectively. The use of smaller N-donors leads to stronger Ge-N interactions and quenching of catenation behaviour: reduction of Ar GeCl gives the digermyne (Ar Ge) , while the unsymmetrical system Ar GeGeAr dimerizes to give tetranuclear (Ar GeGeAr ) through aggregation at the N Pr -ligated Ge centres.