Ge4Cl4[MCp(CO)3]4 (M = Cr,Mo, W): A Series of Transition Metal Substituted Four-membered Cyclogermanes

The reaction of GeCl₂ · dioxane with the sodium salts NaMCp(CO)₃ (M = Cr, Mo, W) leads to new four-membered ring compounds Ge₄Cl₄MCp(CO)₃]₄, where the remaining chlorine atom cannot be substituted by another MCp(CO)₃ substituent. A large excess of the sodium salts only leads to some minor side-reactions. All Ge₄-compounds exhibit a non-planar four-membered Ge₄ ring, which can be traced back to electrostatic effects as shown by quantum chemical calculations. Furthermore, cluster build-up reactions might be possible due to the halide substituents in the new ring compounds of germanium, showing that GeCl₂ · dioxane is an excellent starting material for the synthesis of cluster compounds of germanium.