The synthesis of the guanidine MesN{C(NCy 2 )}N(H)Mes (LH; Mes = 2,4,6-Me 3 C 6 H 2 , Cy = cyclohexyl), and its use as a proligand for the synthesis of alkaline earth metal complexes are reported. Described herein are (i) an unusual Hauser base cubane, (ii) a homoleptic and a base-stabilized magnesium complex featuring the same guanidinate ligands, and (iii) the comparison of a series of alkaline earth (Mg, Ca, Sr, Ba) bis(guanidinate) complexes, which allows the opportunity to compare the changing trends in bonding as the Group is descended. The reaction between LH and MeMgI-(OEt 2 ) 2 yields the Hauser base as a mixture of the tetramer [Mg 4 L 4 (μ 3 -I) 4 ] (1a) and dimer [Mg 2 L 2 (μ-I) 2 (OEt 2 ) 2 ] (1b), and