[CoCl 2 {N,N′-Te 2 (N t Bu) 4 }] (1) was obtained in good yields by the reaction of equimolar amounts of ( t Bu)NTe(μ-N t Bu) 2 TeN( t Bu) and CoCl 2 in toluene under an argon atmosphere. The crystal structure of 1·CH 2 Cl 2 showed that the dimeric tellurium diimide ligand is N,N′-chelated to cobalt. The related reaction of Se(N t Bu) 2 and CoCl 2 affords a green product tentatively identified as a 1:1 adduct [CoCl 2 {N,N′-Se(N t Bu) 2 }] (CHN analysis). However, recrystallization from thf produces the ion-separated complex [Co 2 (μ-Cl) 3 {N,N′-Se(N t Bu) 2 } 2 (thf) 2 ][CoCl 3 {NH 2 ( t Bu)}]·1½thf (2·1½thf), in which the monomeric selenium diimide ligand is N,N′-chelated to cobalt in the cation. A pathway for the formation of 2 from [CoCl 2 {N,N′-Se(N t Bu) 2 }] in thf is proposed.