Depending on the reaction conditions, different products are obtained from the reaction of CoCl2 with CH3C(CH2PPh2)(3) (triphos), including the law-spin complexes [(triphos)Co(mu-Cl)(2)Co(triphos)](2+) (1(2+)) and [(triphos)CoCl2] (3), their solid-state structures being determined by X-ray methods. In solution, additionally, a four-coordinate high-spin complex [(eta(2)-triphos)CoCl2] (2) is present, its concentration relative to that of 3 depending on the solvent and the temperature. The reactivity of these species toward Lewis acids is investigated leading to the novel heterodinuclear complexes [(triphos)Co(mu-Cl)(2)MCl2] (M = Fe (5), Co (6)). Reactions with Lewis bases L yield complexes of the rare type [(triphos)CoCl(L)](+) (L = CO (7(+)), PMe3 (8(+)), NH3 (9(+)), CH3CN (10(+))). One electron reduction of 3 leads to the previously prepared pseudotetrahedral [(triphos)(CoCl)-Cl-I] complex 11, and one-electron oxidation to the novel trigonal-bipyramidal low-spin complex [(triphos)(CoCl2)-Cl-III](+) (12(+)).