Reactions of K12Si17 with the low-valent transition-metal complex Mo(CO)(3)(C7H8) in ethylenediamine/toluene solutions in the presence of 2,2,2-cryptand yield the {Si(NHCH2CH2NH)(3)[Mo(CO)(3)](2)}(2-) dianion, which contains an octahedral Si(NHCH2CH2NH)(3)(2-) subunit. The SiN6 core comprises a rare example of a doubly deprotonated ethylenediame ligand in a coordination complex and is also the first structurally characterized example of a homoleptic Si(N boolean AND N)(3) trischelate. Its structure and spectroscopic properties are described.