AbstractThe monomeric cobalt‐phosphite‐thiolato complex [ Co (mpt)2{P (OCH3)3}2] BF4(Hmpt = 2‐mercaptothiazoline) has been prepared and characterized by X‐ray crystallography. The complex crystallizes in the monoclinic space group C2/cwitha= 0.8078(5),b= 2.6020(18),c= 1.2191(7) nm, β= 99.38 (1)°,V =2.528(3) nm3, and Z = 4. The structure comprises discrete cations [Co (mpt)2(P(OCH3)3}2]+and anions BF4−, in which the cobalt (III) atom is coordinated to two chelate mpt−and twocis‐oriented monodentate P(OCH3)3ligands in a highly distorted octahedral geometry. The most distorted angles are S(2)‐Co(1)‐S(2a) of 162.23(10)° and N (l)‐Co(1)‐S(2) of 71.47 (13)°, the latter is caused by the geometric constraint of the bidentate ligand mpt−. Cyclic voltammetry has been used to study the electrochemical behavior of the title complex on the Pt electrode in MeCN solution with 0.1 mol · L−1of Bu4nNBF489 electrolyte, The dts indicate that the tit