The ligand H 4 tmsab as well as the precursor molecule [Co(bmsab)(dme)] were prepared according to literature. Commercially available chemicals were purchased from Sigma-Aldrich or abcr and used without further purification with the exception of [18-crown-6], which was resublimated before use. A Schlenk flask is charged with the bridging ligand H 4 tmsab (112 mg, 0.25 mmol, 1 eq.), anhydrous KOH (56 mg, 1 mmol, 4 eq.) and 18-crown-6 (198 mg, 0.75 mmol, 3 eq.). After addition of degassed and dry MeCN (12.5 ml), the mixture is stirred for 30 min, giving a pink suspension. The precursor [Co(bmsab)(dme)] (207 mg, 0.5 mmol, 2 eq.) is dissolved in MeCN (12.5 ml), leading to a dark red solution, and cooled to -20°C. The suspension of the deprotonated ligand is added in five portions under exclusion of air to give a red solution with a violet tinge. After stirring for 1.5 h, a freshly prepared solution of FcPF 6 (83 mg, 0.25 mmol, 1 eq.) in 5 ml MeCN is added dropwise, leading to a deep violet solution. After stirring for 1 h, the solvent is removed, giving a dark solid, which is washed with diethyl ether to remove ferrocene. Afterwards, the product is purified by crystallization. Because the precise crystallization procedure is of great importance for the reproducible synthesis of 2, it is described in detail in the following.