Others had attempted to synthesize the ligand N-(2-mercaptoethyl)-N,N’-bis(2-methyl-2-mercaptopropyl)-ethylenediamine and react the ligand with pertechnetate and a reducing agent. We showed that the product was the unexpected complex oxo(2-(1’-methyl-1’-mercaptoethyl)-3-(5"-mercapto-3"-(dehydroaza)hexyl)-thiazolidinato-N-3, N-3", S-1’, S-5")technetium(V), C12H23N2OS3Tc, 1. Crystals of 1 were orthorhombic, P2(1)2(1)2(1), with a = 7.679(2) Angstrom, b = 11.993(4) Angstrom, c = 18.268(4) Angstrom, and Z = 4 (R = 0.053 and R(w) = 0.043 for 2841 independent reflections with I>0). The complex had the usual square pyramidal structure associated with the TcON2S2 core with a Tc=O bond length of 1.665(5) Angstrom. It was established that the synthesis was much more complicated than expected and , as a consequence, rather than the expected intermediate 3,3,10,10-tetramethyl-1,2-dithia-5,8-diazocyclodecane, 6, 2,2,5,5-tetramethyl-3,4-dithia-7,10-diazabicyclo[5.3.0]decane, 5, was obtained. Reaction of 5 with ethylene sulfide gave the thiazolidine-containing ligand 2,2,5,5-tetramethyl-3,4,13-trithia-7,10-diazabicyclo[8.3.0]tridecane as the hydrochloride salt, 7, and the dimeric species 10,10’-(3,4-dithiahexane-1,6-diyl)bis(2,2,5,5-tetramethyl-3,4- dithia-7,10-diazabicyclo[5.3.0]decane, 8. Crystals of 7, C12H25ClN2S3, were triclinic, P (1) over bar, with a = 6.921(2) Angstrom, b = 9.650(2) Angstrom, c = 13.712(2) Angstrom, alpha = 106.88(2)degrees, beta = 101.04(2)degrees, gamma = 97.93(2)degrees, and Z = 2 (R = 0.095 and R(w) = 0.068 based on 2222 independent reflections). Bond lengths and angles were normal.