The reaction of CoCl 2 ·THF and thallium tris(4,4-dimethyl-2-oxazolinyl)phenylborate (TlTo M ) in tetrahydrofuran (THF) provides To M CoCl (1) in 95 % yield; however, appropriate solvents and starting materials are required to favor 1 over two other readily formed side-products, (To M ) 2 Co (2) and {HTo M }CoCl 2 (3). ESR, NMR, FTIR, and UV/Vis spectroscopies were used to distinguish these cobalt(II) products and probe their electronic and structural properties. Even after the structures indicated by these methods were confirmed by X-ray crystallography, the spectroscopic identification of trace contaminants in the material was challenging. The recognition of possible contaminants in the synthesis of To M CoCl in combination [a]