Synthesis and Structure of Oligomeric Dimesitylgermyl-Substituted Carbodiimides; Characterization of Higher Oligomers

New cyclic oligomers of dimesitylgermylene carbodiimides (Mes(2)GeNCN)(n) (n = 3 (1) and 4 (2)) were synthesized by reactions of dimesityldichlorogermane with either cyanamide in the presence of triethylamine or lithium cyanamide. The reactions always gave 1, the trimer of the hypothetical (Mes(2)Ge = N - CN), as the major compound. Higher oligomers 3 (n up to 20 - 30) also can be isolated, depending on the reaction conditions. In THF solution at room temperature, 2 and 3 slowly isomerize to 1, which seems to be the most stable compound. X-ray analysis of trimer 1 and tetramer 2 shows unstrained tetrahedral germanium atoms and linear diimine linkers.